11da177e4SLinus Torvalds /* 21da177e4SLinus Torvalds * INET An implementation of the TCP/IP protocol suite for the LINUX 31da177e4SLinus Torvalds * operating system. INET is implemented using the BSD Socket 41da177e4SLinus Torvalds * interface as the means of communication with the user level. 51da177e4SLinus Torvalds * 61da177e4SLinus Torvalds * Implementation of the Transmission Control Protocol(TCP). 71da177e4SLinus Torvalds * 81da177e4SLinus Torvalds * Version: $Id: tcp_output.c,v 1.146 2002/02/01 22:01:04 davem Exp $ 91da177e4SLinus Torvalds * 1002c30a84SJesper Juhl * Authors: Ross Biro 111da177e4SLinus Torvalds * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 121da177e4SLinus Torvalds * Mark Evans, <evansmp@uhura.aston.ac.uk> 131da177e4SLinus Torvalds * Corey Minyard <wf-rch!minyard@relay.EU.net> 141da177e4SLinus Torvalds * Florian La Roche, <flla@stud.uni-sb.de> 151da177e4SLinus Torvalds * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> 161da177e4SLinus Torvalds * Linus Torvalds, <torvalds@cs.helsinki.fi> 171da177e4SLinus Torvalds * Alan Cox, <gw4pts@gw4pts.ampr.org> 181da177e4SLinus Torvalds * Matthew Dillon, <dillon@apollo.west.oic.com> 191da177e4SLinus Torvalds * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 201da177e4SLinus Torvalds * Jorge Cwik, <jorge@laser.satlink.net> 211da177e4SLinus Torvalds */ 221da177e4SLinus Torvalds 231da177e4SLinus Torvalds /* 241da177e4SLinus Torvalds * Changes: Pedro Roque : Retransmit queue handled by TCP. 251da177e4SLinus Torvalds * : Fragmentation on mtu decrease 261da177e4SLinus Torvalds * : Segment collapse on retransmit 271da177e4SLinus Torvalds * : AF independence 281da177e4SLinus Torvalds * 291da177e4SLinus Torvalds * Linus Torvalds : send_delayed_ack 301da177e4SLinus Torvalds * David S. Miller : Charge memory using the right skb 311da177e4SLinus Torvalds * during syn/ack processing. 321da177e4SLinus Torvalds * David S. Miller : Output engine completely rewritten. 331da177e4SLinus Torvalds * Andrea Arcangeli: SYNACK carry ts_recent in tsecr. 341da177e4SLinus Torvalds * Cacophonix Gaul : draft-minshall-nagle-01 351da177e4SLinus Torvalds * J Hadi Salim : ECN support 361da177e4SLinus Torvalds * 371da177e4SLinus Torvalds */ 381da177e4SLinus Torvalds 391da177e4SLinus Torvalds #include <net/tcp.h> 401da177e4SLinus Torvalds 411da177e4SLinus Torvalds #include <linux/compiler.h> 421da177e4SLinus Torvalds #include <linux/module.h> 431da177e4SLinus Torvalds 441da177e4SLinus Torvalds /* People can turn this off for buggy TCP's found in printers etc. */ 45ab32ea5dSBrian Haley int sysctl_tcp_retrans_collapse __read_mostly = 1; 461da177e4SLinus Torvalds 4715d99e02SRick Jones /* People can turn this on to work with those rare, broken TCPs that 4815d99e02SRick Jones * interpret the window field as a signed quantity. 4915d99e02SRick Jones */ 50ab32ea5dSBrian Haley int sysctl_tcp_workaround_signed_windows __read_mostly = 0; 5115d99e02SRick Jones 521da177e4SLinus Torvalds /* This limits the percentage of the congestion window which we 531da177e4SLinus Torvalds * will allow a single TSO frame to consume. Building TSO frames 541da177e4SLinus Torvalds * which are too large can cause TCP streams to be bursty. 551da177e4SLinus Torvalds */ 56ab32ea5dSBrian Haley int sysctl_tcp_tso_win_divisor __read_mostly = 3; 571da177e4SLinus Torvalds 58ab32ea5dSBrian Haley int sysctl_tcp_mtu_probing __read_mostly = 0; 59ab32ea5dSBrian Haley int sysctl_tcp_base_mss __read_mostly = 512; 605d424d5aSJohn Heffner 6135089bb2SDavid S. Miller /* By default, RFC2861 behavior. */ 62ab32ea5dSBrian Haley int sysctl_tcp_slow_start_after_idle __read_mostly = 1; 6335089bb2SDavid S. Miller 646ff03ac3SIlpo Järvinen static inline void tcp_packets_out_inc(struct sock *sk, 656ff03ac3SIlpo Järvinen const struct sk_buff *skb) 666ff03ac3SIlpo Järvinen { 676ff03ac3SIlpo Järvinen struct tcp_sock *tp = tcp_sk(sk); 686ff03ac3SIlpo Järvinen int orig = tp->packets_out; 696ff03ac3SIlpo Järvinen 706ff03ac3SIlpo Järvinen tp->packets_out += tcp_skb_pcount(skb); 716ff03ac3SIlpo Järvinen if (!orig) 726ff03ac3SIlpo Järvinen inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 736ff03ac3SIlpo Järvinen inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 746ff03ac3SIlpo Järvinen } 756ff03ac3SIlpo Järvinen 769e412ba7SIlpo Järvinen static void update_send_head(struct sock *sk, struct sk_buff *skb) 771da177e4SLinus Torvalds { 789e412ba7SIlpo Järvinen struct tcp_sock *tp = tcp_sk(sk); 799e412ba7SIlpo Järvinen 80fe067e8aSDavid S. Miller tcp_advance_send_head(sk, skb); 811da177e4SLinus Torvalds tp->snd_nxt = TCP_SKB_CB(skb)->end_seq; 829e412ba7SIlpo Järvinen tcp_packets_out_inc(sk, skb); 831da177e4SLinus Torvalds } 841da177e4SLinus Torvalds 851da177e4SLinus Torvalds /* SND.NXT, if window was not shrunk. 861da177e4SLinus Torvalds * If window has been shrunk, what should we make? It is not clear at all. 871da177e4SLinus Torvalds * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-( 881da177e4SLinus Torvalds * Anything in between SND.UNA...SND.UNA+SND.WND also can be already 891da177e4SLinus Torvalds * invalid. OK, let's make this for now: 901da177e4SLinus Torvalds */ 919e412ba7SIlpo Järvinen static inline __u32 tcp_acceptable_seq(struct sock *sk) 921da177e4SLinus Torvalds { 939e412ba7SIlpo Järvinen struct tcp_sock *tp = tcp_sk(sk); 949e412ba7SIlpo Järvinen 951da177e4SLinus Torvalds if (!before(tp->snd_una+tp->snd_wnd, tp->snd_nxt)) 961da177e4SLinus Torvalds return tp->snd_nxt; 971da177e4SLinus Torvalds else 981da177e4SLinus Torvalds return tp->snd_una+tp->snd_wnd; 991da177e4SLinus Torvalds } 1001da177e4SLinus Torvalds 1011da177e4SLinus Torvalds /* Calculate mss to advertise in SYN segment. 1021da177e4SLinus Torvalds * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that: 1031da177e4SLinus Torvalds * 1041da177e4SLinus Torvalds * 1. It is independent of path mtu. 1051da177e4SLinus Torvalds * 2. Ideally, it is maximal possible segment size i.e. 65535-40. 1061da177e4SLinus Torvalds * 3. For IPv4 it is reasonable to calculate it from maximal MTU of 1071da177e4SLinus Torvalds * attached devices, because some buggy hosts are confused by 1081da177e4SLinus Torvalds * large MSS. 1091da177e4SLinus Torvalds * 4. We do not make 3, we advertise MSS, calculated from first 1101da177e4SLinus Torvalds * hop device mtu, but allow to raise it to ip_rt_min_advmss. 1111da177e4SLinus Torvalds * This may be overridden via information stored in routing table. 1121da177e4SLinus Torvalds * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible, 1131da177e4SLinus Torvalds * probably even Jumbo". 1141da177e4SLinus Torvalds */ 1151da177e4SLinus Torvalds static __u16 tcp_advertise_mss(struct sock *sk) 1161da177e4SLinus Torvalds { 1171da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 1181da177e4SLinus Torvalds struct dst_entry *dst = __sk_dst_get(sk); 1191da177e4SLinus Torvalds int mss = tp->advmss; 1201da177e4SLinus Torvalds 1211da177e4SLinus Torvalds if (dst && dst_metric(dst, RTAX_ADVMSS) < mss) { 1221da177e4SLinus Torvalds mss = dst_metric(dst, RTAX_ADVMSS); 1231da177e4SLinus Torvalds tp->advmss = mss; 1241da177e4SLinus Torvalds } 1251da177e4SLinus Torvalds 1261da177e4SLinus Torvalds return (__u16)mss; 1271da177e4SLinus Torvalds } 1281da177e4SLinus Torvalds 1291da177e4SLinus Torvalds /* RFC2861. Reset CWND after idle period longer RTO to "restart window". 1301da177e4SLinus Torvalds * This is the first part of cwnd validation mechanism. */ 131463c84b9SArnaldo Carvalho de Melo static void tcp_cwnd_restart(struct sock *sk, struct dst_entry *dst) 1321da177e4SLinus Torvalds { 133463c84b9SArnaldo Carvalho de Melo struct tcp_sock *tp = tcp_sk(sk); 1341da177e4SLinus Torvalds s32 delta = tcp_time_stamp - tp->lsndtime; 1351da177e4SLinus Torvalds u32 restart_cwnd = tcp_init_cwnd(tp, dst); 1361da177e4SLinus Torvalds u32 cwnd = tp->snd_cwnd; 1371da177e4SLinus Torvalds 1386687e988SArnaldo Carvalho de Melo tcp_ca_event(sk, CA_EVENT_CWND_RESTART); 1391da177e4SLinus Torvalds 1406687e988SArnaldo Carvalho de Melo tp->snd_ssthresh = tcp_current_ssthresh(sk); 1411da177e4SLinus Torvalds restart_cwnd = min(restart_cwnd, cwnd); 1421da177e4SLinus Torvalds 143463c84b9SArnaldo Carvalho de Melo while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd) 1441da177e4SLinus Torvalds cwnd >>= 1; 1451da177e4SLinus Torvalds tp->snd_cwnd = max(cwnd, restart_cwnd); 1461da177e4SLinus Torvalds tp->snd_cwnd_stamp = tcp_time_stamp; 1471da177e4SLinus Torvalds tp->snd_cwnd_used = 0; 1481da177e4SLinus Torvalds } 1491da177e4SLinus Torvalds 15040efc6faSStephen Hemminger static void tcp_event_data_sent(struct tcp_sock *tp, 1511da177e4SLinus Torvalds struct sk_buff *skb, struct sock *sk) 1521da177e4SLinus Torvalds { 153463c84b9SArnaldo Carvalho de Melo struct inet_connection_sock *icsk = inet_csk(sk); 154463c84b9SArnaldo Carvalho de Melo const u32 now = tcp_time_stamp; 1551da177e4SLinus Torvalds 15635089bb2SDavid S. Miller if (sysctl_tcp_slow_start_after_idle && 15735089bb2SDavid S. Miller (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto)) 158463c84b9SArnaldo Carvalho de Melo tcp_cwnd_restart(sk, __sk_dst_get(sk)); 1591da177e4SLinus Torvalds 1601da177e4SLinus Torvalds tp->lsndtime = now; 1611da177e4SLinus Torvalds 1621da177e4SLinus Torvalds /* If it is a reply for ato after last received 1631da177e4SLinus Torvalds * packet, enter pingpong mode. 1641da177e4SLinus Torvalds */ 165463c84b9SArnaldo Carvalho de Melo if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato) 166463c84b9SArnaldo Carvalho de Melo icsk->icsk_ack.pingpong = 1; 1671da177e4SLinus Torvalds } 1681da177e4SLinus Torvalds 16940efc6faSStephen Hemminger static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts) 1701da177e4SLinus Torvalds { 171463c84b9SArnaldo Carvalho de Melo tcp_dec_quickack_mode(sk, pkts); 172463c84b9SArnaldo Carvalho de Melo inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); 1731da177e4SLinus Torvalds } 1741da177e4SLinus Torvalds 1751da177e4SLinus Torvalds /* Determine a window scaling and initial window to offer. 1761da177e4SLinus Torvalds * Based on the assumption that the given amount of space 1771da177e4SLinus Torvalds * will be offered. Store the results in the tp structure. 1781da177e4SLinus Torvalds * NOTE: for smooth operation initial space offering should 1791da177e4SLinus Torvalds * be a multiple of mss if possible. We assume here that mss >= 1. 1801da177e4SLinus Torvalds * This MUST be enforced by all callers. 1811da177e4SLinus Torvalds */ 1821da177e4SLinus Torvalds void tcp_select_initial_window(int __space, __u32 mss, 1831da177e4SLinus Torvalds __u32 *rcv_wnd, __u32 *window_clamp, 1841da177e4SLinus Torvalds int wscale_ok, __u8 *rcv_wscale) 1851da177e4SLinus Torvalds { 1861da177e4SLinus Torvalds unsigned int space = (__space < 0 ? 0 : __space); 1871da177e4SLinus Torvalds 1881da177e4SLinus Torvalds /* If no clamp set the clamp to the max possible scaled window */ 1891da177e4SLinus Torvalds if (*window_clamp == 0) 1901da177e4SLinus Torvalds (*window_clamp) = (65535 << 14); 1911da177e4SLinus Torvalds space = min(*window_clamp, space); 1921da177e4SLinus Torvalds 1931da177e4SLinus Torvalds /* Quantize space offering to a multiple of mss if possible. */ 1941da177e4SLinus Torvalds if (space > mss) 1951da177e4SLinus Torvalds space = (space / mss) * mss; 1961da177e4SLinus Torvalds 1971da177e4SLinus Torvalds /* NOTE: offering an initial window larger than 32767 19815d99e02SRick Jones * will break some buggy TCP stacks. If the admin tells us 19915d99e02SRick Jones * it is likely we could be speaking with such a buggy stack 20015d99e02SRick Jones * we will truncate our initial window offering to 32K-1 20115d99e02SRick Jones * unless the remote has sent us a window scaling option, 20215d99e02SRick Jones * which we interpret as a sign the remote TCP is not 20315d99e02SRick Jones * misinterpreting the window field as a signed quantity. 2041da177e4SLinus Torvalds */ 20515d99e02SRick Jones if (sysctl_tcp_workaround_signed_windows) 2061da177e4SLinus Torvalds (*rcv_wnd) = min(space, MAX_TCP_WINDOW); 20715d99e02SRick Jones else 20815d99e02SRick Jones (*rcv_wnd) = space; 20915d99e02SRick Jones 2101da177e4SLinus Torvalds (*rcv_wscale) = 0; 2111da177e4SLinus Torvalds if (wscale_ok) { 2121da177e4SLinus Torvalds /* Set window scaling on max possible window 2131da177e4SLinus Torvalds * See RFC1323 for an explanation of the limit to 14 2141da177e4SLinus Torvalds */ 2151da177e4SLinus Torvalds space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max); 216316c1592SStephen Hemminger space = min_t(u32, space, *window_clamp); 2171da177e4SLinus Torvalds while (space > 65535 && (*rcv_wscale) < 14) { 2181da177e4SLinus Torvalds space >>= 1; 2191da177e4SLinus Torvalds (*rcv_wscale)++; 2201da177e4SLinus Torvalds } 2211da177e4SLinus Torvalds } 2221da177e4SLinus Torvalds 2231da177e4SLinus Torvalds /* Set initial window to value enough for senders, 2246b251858SDavid S. Miller * following RFC2414. Senders, not following this RFC, 2251da177e4SLinus Torvalds * will be satisfied with 2. 2261da177e4SLinus Torvalds */ 2271da177e4SLinus Torvalds if (mss > (1<<*rcv_wscale)) { 22801ff367eSDavid S. Miller int init_cwnd = 4; 22901ff367eSDavid S. Miller if (mss > 1460*3) 2301da177e4SLinus Torvalds init_cwnd = 2; 23101ff367eSDavid S. Miller else if (mss > 1460) 23201ff367eSDavid S. Miller init_cwnd = 3; 2331da177e4SLinus Torvalds if (*rcv_wnd > init_cwnd*mss) 2341da177e4SLinus Torvalds *rcv_wnd = init_cwnd*mss; 2351da177e4SLinus Torvalds } 2361da177e4SLinus Torvalds 2371da177e4SLinus Torvalds /* Set the clamp no higher than max representable value */ 2381da177e4SLinus Torvalds (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp); 2391da177e4SLinus Torvalds } 2401da177e4SLinus Torvalds 2411da177e4SLinus Torvalds /* Chose a new window to advertise, update state in tcp_sock for the 2421da177e4SLinus Torvalds * socket, and return result with RFC1323 scaling applied. The return 2431da177e4SLinus Torvalds * value can be stuffed directly into th->window for an outgoing 2441da177e4SLinus Torvalds * frame. 2451da177e4SLinus Torvalds */ 24640efc6faSStephen Hemminger static u16 tcp_select_window(struct sock *sk) 2471da177e4SLinus Torvalds { 2481da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 2491da177e4SLinus Torvalds u32 cur_win = tcp_receive_window(tp); 2501da177e4SLinus Torvalds u32 new_win = __tcp_select_window(sk); 2511da177e4SLinus Torvalds 2521da177e4SLinus Torvalds /* Never shrink the offered window */ 2531da177e4SLinus Torvalds if (new_win < cur_win) { 2541da177e4SLinus Torvalds /* Danger Will Robinson! 2551da177e4SLinus Torvalds * Don't update rcv_wup/rcv_wnd here or else 2561da177e4SLinus Torvalds * we will not be able to advertise a zero 2571da177e4SLinus Torvalds * window in time. --DaveM 2581da177e4SLinus Torvalds * 2591da177e4SLinus Torvalds * Relax Will Robinson. 2601da177e4SLinus Torvalds */ 2611da177e4SLinus Torvalds new_win = cur_win; 2621da177e4SLinus Torvalds } 2631da177e4SLinus Torvalds tp->rcv_wnd = new_win; 2641da177e4SLinus Torvalds tp->rcv_wup = tp->rcv_nxt; 2651da177e4SLinus Torvalds 2661da177e4SLinus Torvalds /* Make sure we do not exceed the maximum possible 2671da177e4SLinus Torvalds * scaled window. 2681da177e4SLinus Torvalds */ 26915d99e02SRick Jones if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows) 2701da177e4SLinus Torvalds new_win = min(new_win, MAX_TCP_WINDOW); 2711da177e4SLinus Torvalds else 2721da177e4SLinus Torvalds new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); 2731da177e4SLinus Torvalds 2741da177e4SLinus Torvalds /* RFC1323 scaling applied */ 2751da177e4SLinus Torvalds new_win >>= tp->rx_opt.rcv_wscale; 2761da177e4SLinus Torvalds 2771da177e4SLinus Torvalds /* If we advertise zero window, disable fast path. */ 2781da177e4SLinus Torvalds if (new_win == 0) 2791da177e4SLinus Torvalds tp->pred_flags = 0; 2801da177e4SLinus Torvalds 2811da177e4SLinus Torvalds return new_win; 2821da177e4SLinus Torvalds } 2831da177e4SLinus Torvalds 284bdf1ee5dSIlpo Järvinen static inline void TCP_ECN_send_synack(struct tcp_sock *tp, 285bdf1ee5dSIlpo Järvinen struct sk_buff *skb) 286bdf1ee5dSIlpo Järvinen { 287bdf1ee5dSIlpo Järvinen TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_CWR; 288bdf1ee5dSIlpo Järvinen if (!(tp->ecn_flags&TCP_ECN_OK)) 289bdf1ee5dSIlpo Järvinen TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_ECE; 290bdf1ee5dSIlpo Järvinen } 291bdf1ee5dSIlpo Järvinen 292bdf1ee5dSIlpo Järvinen static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb) 293bdf1ee5dSIlpo Järvinen { 294bdf1ee5dSIlpo Järvinen struct tcp_sock *tp = tcp_sk(sk); 295bdf1ee5dSIlpo Järvinen 296bdf1ee5dSIlpo Järvinen tp->ecn_flags = 0; 297bdf1ee5dSIlpo Järvinen if (sysctl_tcp_ecn) { 298bdf1ee5dSIlpo Järvinen TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ECE|TCPCB_FLAG_CWR; 299bdf1ee5dSIlpo Järvinen tp->ecn_flags = TCP_ECN_OK; 300bdf1ee5dSIlpo Järvinen } 301bdf1ee5dSIlpo Järvinen } 302bdf1ee5dSIlpo Järvinen 303bdf1ee5dSIlpo Järvinen static __inline__ void 304bdf1ee5dSIlpo Järvinen TCP_ECN_make_synack(struct request_sock *req, struct tcphdr *th) 305bdf1ee5dSIlpo Järvinen { 306bdf1ee5dSIlpo Järvinen if (inet_rsk(req)->ecn_ok) 307bdf1ee5dSIlpo Järvinen th->ece = 1; 308bdf1ee5dSIlpo Järvinen } 309bdf1ee5dSIlpo Järvinen 310bdf1ee5dSIlpo Järvinen static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb, 311bdf1ee5dSIlpo Järvinen int tcp_header_len) 312bdf1ee5dSIlpo Järvinen { 313bdf1ee5dSIlpo Järvinen struct tcp_sock *tp = tcp_sk(sk); 314bdf1ee5dSIlpo Järvinen 315bdf1ee5dSIlpo Järvinen if (tp->ecn_flags & TCP_ECN_OK) { 316bdf1ee5dSIlpo Järvinen /* Not-retransmitted data segment: set ECT and inject CWR. */ 317bdf1ee5dSIlpo Järvinen if (skb->len != tcp_header_len && 318bdf1ee5dSIlpo Järvinen !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) { 319bdf1ee5dSIlpo Järvinen INET_ECN_xmit(sk); 320bdf1ee5dSIlpo Järvinen if (tp->ecn_flags&TCP_ECN_QUEUE_CWR) { 321bdf1ee5dSIlpo Järvinen tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR; 322bdf1ee5dSIlpo Järvinen tcp_hdr(skb)->cwr = 1; 323bdf1ee5dSIlpo Järvinen skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; 324bdf1ee5dSIlpo Järvinen } 325bdf1ee5dSIlpo Järvinen } else { 326bdf1ee5dSIlpo Järvinen /* ACK or retransmitted segment: clear ECT|CE */ 327bdf1ee5dSIlpo Järvinen INET_ECN_dontxmit(sk); 328bdf1ee5dSIlpo Järvinen } 329bdf1ee5dSIlpo Järvinen if (tp->ecn_flags & TCP_ECN_DEMAND_CWR) 330bdf1ee5dSIlpo Järvinen tcp_hdr(skb)->ece = 1; 331bdf1ee5dSIlpo Järvinen } 332bdf1ee5dSIlpo Järvinen } 333bdf1ee5dSIlpo Järvinen 334df7a3b07SAl Viro static void tcp_build_and_update_options(__be32 *ptr, struct tcp_sock *tp, 335cfb6eeb4SYOSHIFUJI Hideaki __u32 tstamp, __u8 **md5_hash) 33640efc6faSStephen Hemminger { 33740efc6faSStephen Hemminger if (tp->rx_opt.tstamp_ok) { 338496c98dfSYOSHIFUJI Hideaki *ptr++ = htonl((TCPOPT_NOP << 24) | 33940efc6faSStephen Hemminger (TCPOPT_NOP << 16) | 34040efc6faSStephen Hemminger (TCPOPT_TIMESTAMP << 8) | 34140efc6faSStephen Hemminger TCPOLEN_TIMESTAMP); 34240efc6faSStephen Hemminger *ptr++ = htonl(tstamp); 34340efc6faSStephen Hemminger *ptr++ = htonl(tp->rx_opt.ts_recent); 34440efc6faSStephen Hemminger } 34540efc6faSStephen Hemminger if (tp->rx_opt.eff_sacks) { 34640efc6faSStephen Hemminger struct tcp_sack_block *sp = tp->rx_opt.dsack ? tp->duplicate_sack : tp->selective_acks; 34740efc6faSStephen Hemminger int this_sack; 34840efc6faSStephen Hemminger 34940efc6faSStephen Hemminger *ptr++ = htonl((TCPOPT_NOP << 24) | 35040efc6faSStephen Hemminger (TCPOPT_NOP << 16) | 35140efc6faSStephen Hemminger (TCPOPT_SACK << 8) | 35240efc6faSStephen Hemminger (TCPOLEN_SACK_BASE + (tp->rx_opt.eff_sacks * 35340efc6faSStephen Hemminger TCPOLEN_SACK_PERBLOCK))); 3542de979bdSStephen Hemminger 35540efc6faSStephen Hemminger for (this_sack = 0; this_sack < tp->rx_opt.eff_sacks; this_sack++) { 35640efc6faSStephen Hemminger *ptr++ = htonl(sp[this_sack].start_seq); 35740efc6faSStephen Hemminger *ptr++ = htonl(sp[this_sack].end_seq); 35840efc6faSStephen Hemminger } 3592de979bdSStephen Hemminger 36040efc6faSStephen Hemminger if (tp->rx_opt.dsack) { 36140efc6faSStephen Hemminger tp->rx_opt.dsack = 0; 36240efc6faSStephen Hemminger tp->rx_opt.eff_sacks--; 36340efc6faSStephen Hemminger } 36440efc6faSStephen Hemminger } 365cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 366cfb6eeb4SYOSHIFUJI Hideaki if (md5_hash) { 367cfb6eeb4SYOSHIFUJI Hideaki *ptr++ = htonl((TCPOPT_NOP << 24) | 368cfb6eeb4SYOSHIFUJI Hideaki (TCPOPT_NOP << 16) | 369cfb6eeb4SYOSHIFUJI Hideaki (TCPOPT_MD5SIG << 8) | 370cfb6eeb4SYOSHIFUJI Hideaki TCPOLEN_MD5SIG); 371cfb6eeb4SYOSHIFUJI Hideaki *md5_hash = (__u8 *)ptr; 372cfb6eeb4SYOSHIFUJI Hideaki } 373cfb6eeb4SYOSHIFUJI Hideaki #endif 37440efc6faSStephen Hemminger } 37540efc6faSStephen Hemminger 37640efc6faSStephen Hemminger /* Construct a tcp options header for a SYN or SYN_ACK packet. 37740efc6faSStephen Hemminger * If this is every changed make sure to change the definition of 37840efc6faSStephen Hemminger * MAX_SYN_SIZE to match the new maximum number of options that you 37940efc6faSStephen Hemminger * can generate. 380cfb6eeb4SYOSHIFUJI Hideaki * 381cfb6eeb4SYOSHIFUJI Hideaki * Note - that with the RFC2385 TCP option, we make room for the 382cfb6eeb4SYOSHIFUJI Hideaki * 16 byte MD5 hash. This will be filled in later, so the pointer for the 383cfb6eeb4SYOSHIFUJI Hideaki * location to be filled is passed back up. 38440efc6faSStephen Hemminger */ 385df7a3b07SAl Viro static void tcp_syn_build_options(__be32 *ptr, int mss, int ts, int sack, 38640efc6faSStephen Hemminger int offer_wscale, int wscale, __u32 tstamp, 387cfb6eeb4SYOSHIFUJI Hideaki __u32 ts_recent, __u8 **md5_hash) 38840efc6faSStephen Hemminger { 38940efc6faSStephen Hemminger /* We always get an MSS option. 39040efc6faSStephen Hemminger * The option bytes which will be seen in normal data 39140efc6faSStephen Hemminger * packets should timestamps be used, must be in the MSS 39240efc6faSStephen Hemminger * advertised. But we subtract them from tp->mss_cache so 39340efc6faSStephen Hemminger * that calculations in tcp_sendmsg are simpler etc. 39440efc6faSStephen Hemminger * So account for this fact here if necessary. If we 39540efc6faSStephen Hemminger * don't do this correctly, as a receiver we won't 39640efc6faSStephen Hemminger * recognize data packets as being full sized when we 39740efc6faSStephen Hemminger * should, and thus we won't abide by the delayed ACK 39840efc6faSStephen Hemminger * rules correctly. 39940efc6faSStephen Hemminger * SACKs don't matter, we never delay an ACK when we 40040efc6faSStephen Hemminger * have any of those going out. 40140efc6faSStephen Hemminger */ 40240efc6faSStephen Hemminger *ptr++ = htonl((TCPOPT_MSS << 24) | (TCPOLEN_MSS << 16) | mss); 40340efc6faSStephen Hemminger if (ts) { 40440efc6faSStephen Hemminger if (sack) 405496c98dfSYOSHIFUJI Hideaki *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | 406496c98dfSYOSHIFUJI Hideaki (TCPOLEN_SACK_PERM << 16) | 407496c98dfSYOSHIFUJI Hideaki (TCPOPT_TIMESTAMP << 8) | 408496c98dfSYOSHIFUJI Hideaki TCPOLEN_TIMESTAMP); 40940efc6faSStephen Hemminger else 410496c98dfSYOSHIFUJI Hideaki *ptr++ = htonl((TCPOPT_NOP << 24) | 411496c98dfSYOSHIFUJI Hideaki (TCPOPT_NOP << 16) | 412496c98dfSYOSHIFUJI Hideaki (TCPOPT_TIMESTAMP << 8) | 413496c98dfSYOSHIFUJI Hideaki TCPOLEN_TIMESTAMP); 41440efc6faSStephen Hemminger *ptr++ = htonl(tstamp); /* TSVAL */ 41540efc6faSStephen Hemminger *ptr++ = htonl(ts_recent); /* TSECR */ 41640efc6faSStephen Hemminger } else if (sack) 417496c98dfSYOSHIFUJI Hideaki *ptr++ = htonl((TCPOPT_NOP << 24) | 418496c98dfSYOSHIFUJI Hideaki (TCPOPT_NOP << 16) | 419496c98dfSYOSHIFUJI Hideaki (TCPOPT_SACK_PERM << 8) | 420496c98dfSYOSHIFUJI Hideaki TCPOLEN_SACK_PERM); 42140efc6faSStephen Hemminger if (offer_wscale) 422496c98dfSYOSHIFUJI Hideaki *ptr++ = htonl((TCPOPT_NOP << 24) | 423496c98dfSYOSHIFUJI Hideaki (TCPOPT_WINDOW << 16) | 424496c98dfSYOSHIFUJI Hideaki (TCPOLEN_WINDOW << 8) | 425496c98dfSYOSHIFUJI Hideaki (wscale)); 426cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 427cfb6eeb4SYOSHIFUJI Hideaki /* 428cfb6eeb4SYOSHIFUJI Hideaki * If MD5 is enabled, then we set the option, and include the size 429cfb6eeb4SYOSHIFUJI Hideaki * (always 18). The actual MD5 hash is added just before the 430cfb6eeb4SYOSHIFUJI Hideaki * packet is sent. 431cfb6eeb4SYOSHIFUJI Hideaki */ 432cfb6eeb4SYOSHIFUJI Hideaki if (md5_hash) { 433cfb6eeb4SYOSHIFUJI Hideaki *ptr++ = htonl((TCPOPT_NOP << 24) | 434cfb6eeb4SYOSHIFUJI Hideaki (TCPOPT_NOP << 16) | 435cfb6eeb4SYOSHIFUJI Hideaki (TCPOPT_MD5SIG << 8) | 436cfb6eeb4SYOSHIFUJI Hideaki TCPOLEN_MD5SIG); 437cfb6eeb4SYOSHIFUJI Hideaki *md5_hash = (__u8 *) ptr; 438cfb6eeb4SYOSHIFUJI Hideaki } 439cfb6eeb4SYOSHIFUJI Hideaki #endif 44040efc6faSStephen Hemminger } 4411da177e4SLinus Torvalds 4421da177e4SLinus Torvalds /* This routine actually transmits TCP packets queued in by 4431da177e4SLinus Torvalds * tcp_do_sendmsg(). This is used by both the initial 4441da177e4SLinus Torvalds * transmission and possible later retransmissions. 4451da177e4SLinus Torvalds * All SKB's seen here are completely headerless. It is our 4461da177e4SLinus Torvalds * job to build the TCP header, and pass the packet down to 4471da177e4SLinus Torvalds * IP so it can do the same plus pass the packet off to the 4481da177e4SLinus Torvalds * device. 4491da177e4SLinus Torvalds * 4501da177e4SLinus Torvalds * We are working here with either a clone of the original 4511da177e4SLinus Torvalds * SKB, or a fresh unique copy made by the retransmit engine. 4521da177e4SLinus Torvalds */ 453dfb4b9dcSDavid S. Miller static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, gfp_t gfp_mask) 4541da177e4SLinus Torvalds { 4556687e988SArnaldo Carvalho de Melo const struct inet_connection_sock *icsk = inet_csk(sk); 456dfb4b9dcSDavid S. Miller struct inet_sock *inet; 457dfb4b9dcSDavid S. Miller struct tcp_sock *tp; 458dfb4b9dcSDavid S. Miller struct tcp_skb_cb *tcb; 459dfb4b9dcSDavid S. Miller int tcp_header_size; 460cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 461cfb6eeb4SYOSHIFUJI Hideaki struct tcp_md5sig_key *md5; 462cfb6eeb4SYOSHIFUJI Hideaki __u8 *md5_hash_location; 463cfb6eeb4SYOSHIFUJI Hideaki #endif 4641da177e4SLinus Torvalds struct tcphdr *th; 4651da177e4SLinus Torvalds int sysctl_flags; 4661da177e4SLinus Torvalds int err; 4671da177e4SLinus Torvalds 468dfb4b9dcSDavid S. Miller BUG_ON(!skb || !tcp_skb_pcount(skb)); 469dfb4b9dcSDavid S. Miller 470dfb4b9dcSDavid S. Miller /* If congestion control is doing timestamping, we must 471dfb4b9dcSDavid S. Miller * take such a timestamp before we potentially clone/copy. 472dfb4b9dcSDavid S. Miller */ 473164891aaSStephen Hemminger if (icsk->icsk_ca_ops->flags & TCP_CONG_RTT_STAMP) 474dfb4b9dcSDavid S. Miller __net_timestamp(skb); 475dfb4b9dcSDavid S. Miller 476dfb4b9dcSDavid S. Miller if (likely(clone_it)) { 477dfb4b9dcSDavid S. Miller if (unlikely(skb_cloned(skb))) 478dfb4b9dcSDavid S. Miller skb = pskb_copy(skb, gfp_mask); 479dfb4b9dcSDavid S. Miller else 480dfb4b9dcSDavid S. Miller skb = skb_clone(skb, gfp_mask); 481dfb4b9dcSDavid S. Miller if (unlikely(!skb)) 482dfb4b9dcSDavid S. Miller return -ENOBUFS; 483dfb4b9dcSDavid S. Miller } 484dfb4b9dcSDavid S. Miller 485dfb4b9dcSDavid S. Miller inet = inet_sk(sk); 486dfb4b9dcSDavid S. Miller tp = tcp_sk(sk); 487dfb4b9dcSDavid S. Miller tcb = TCP_SKB_CB(skb); 488dfb4b9dcSDavid S. Miller tcp_header_size = tp->tcp_header_len; 4891da177e4SLinus Torvalds 4901da177e4SLinus Torvalds #define SYSCTL_FLAG_TSTAMPS 0x1 4911da177e4SLinus Torvalds #define SYSCTL_FLAG_WSCALE 0x2 4921da177e4SLinus Torvalds #define SYSCTL_FLAG_SACK 0x4 4931da177e4SLinus Torvalds 4941da177e4SLinus Torvalds sysctl_flags = 0; 495dfb4b9dcSDavid S. Miller if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) { 4961da177e4SLinus Torvalds tcp_header_size = sizeof(struct tcphdr) + TCPOLEN_MSS; 4971da177e4SLinus Torvalds if (sysctl_tcp_timestamps) { 4981da177e4SLinus Torvalds tcp_header_size += TCPOLEN_TSTAMP_ALIGNED; 4991da177e4SLinus Torvalds sysctl_flags |= SYSCTL_FLAG_TSTAMPS; 5001da177e4SLinus Torvalds } 5011da177e4SLinus Torvalds if (sysctl_tcp_window_scaling) { 5021da177e4SLinus Torvalds tcp_header_size += TCPOLEN_WSCALE_ALIGNED; 5031da177e4SLinus Torvalds sysctl_flags |= SYSCTL_FLAG_WSCALE; 5041da177e4SLinus Torvalds } 5051da177e4SLinus Torvalds if (sysctl_tcp_sack) { 5061da177e4SLinus Torvalds sysctl_flags |= SYSCTL_FLAG_SACK; 5071da177e4SLinus Torvalds if (!(sysctl_flags & SYSCTL_FLAG_TSTAMPS)) 5081da177e4SLinus Torvalds tcp_header_size += TCPOLEN_SACKPERM_ALIGNED; 5091da177e4SLinus Torvalds } 510dfb4b9dcSDavid S. Miller } else if (unlikely(tp->rx_opt.eff_sacks)) { 5111da177e4SLinus Torvalds /* A SACK is 2 pad bytes, a 2 byte header, plus 5121da177e4SLinus Torvalds * 2 32-bit sequence numbers for each SACK block. 5131da177e4SLinus Torvalds */ 5141da177e4SLinus Torvalds tcp_header_size += (TCPOLEN_SACK_BASE_ALIGNED + 515dfb4b9dcSDavid S. Miller (tp->rx_opt.eff_sacks * 516dfb4b9dcSDavid S. Miller TCPOLEN_SACK_PERBLOCK)); 5171da177e4SLinus Torvalds } 5181da177e4SLinus Torvalds 519317a76f9SStephen Hemminger if (tcp_packets_in_flight(tp) == 0) 5206687e988SArnaldo Carvalho de Melo tcp_ca_event(sk, CA_EVENT_TX_START); 5211da177e4SLinus Torvalds 522cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 523cfb6eeb4SYOSHIFUJI Hideaki /* 524cfb6eeb4SYOSHIFUJI Hideaki * Are we doing MD5 on this segment? If so - make 525cfb6eeb4SYOSHIFUJI Hideaki * room for it. 526cfb6eeb4SYOSHIFUJI Hideaki */ 527cfb6eeb4SYOSHIFUJI Hideaki md5 = tp->af_specific->md5_lookup(sk, sk); 528cfb6eeb4SYOSHIFUJI Hideaki if (md5) 529cfb6eeb4SYOSHIFUJI Hideaki tcp_header_size += TCPOLEN_MD5SIG_ALIGNED; 530cfb6eeb4SYOSHIFUJI Hideaki #endif 531cfb6eeb4SYOSHIFUJI Hideaki 532aa8223c7SArnaldo Carvalho de Melo skb_push(skb, tcp_header_size); 533aa8223c7SArnaldo Carvalho de Melo skb_reset_transport_header(skb); 534e89862f4SDavid S. Miller skb_set_owner_w(skb, sk); 5351da177e4SLinus Torvalds 5361da177e4SLinus Torvalds /* Build TCP header and checksum it. */ 537aa8223c7SArnaldo Carvalho de Melo th = tcp_hdr(skb); 5381da177e4SLinus Torvalds th->source = inet->sport; 5391da177e4SLinus Torvalds th->dest = inet->dport; 5401da177e4SLinus Torvalds th->seq = htonl(tcb->seq); 5411da177e4SLinus Torvalds th->ack_seq = htonl(tp->rcv_nxt); 542df7a3b07SAl Viro *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) | 543dfb4b9dcSDavid S. Miller tcb->flags); 544dfb4b9dcSDavid S. Miller 545dfb4b9dcSDavid S. Miller if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) { 5461da177e4SLinus Torvalds /* RFC1323: The window in SYN & SYN/ACK segments 5471da177e4SLinus Torvalds * is never scaled. 5481da177e4SLinus Torvalds */ 549600ff0c2SIlpo Järvinen th->window = htons(min(tp->rcv_wnd, 65535U)); 5501da177e4SLinus Torvalds } else { 5511da177e4SLinus Torvalds th->window = htons(tcp_select_window(sk)); 5521da177e4SLinus Torvalds } 5531da177e4SLinus Torvalds th->check = 0; 5541da177e4SLinus Torvalds th->urg_ptr = 0; 5551da177e4SLinus Torvalds 556dfb4b9dcSDavid S. Miller if (unlikely(tp->urg_mode && 557dfb4b9dcSDavid S. Miller between(tp->snd_up, tcb->seq+1, tcb->seq+0xFFFF))) { 5581da177e4SLinus Torvalds th->urg_ptr = htons(tp->snd_up-tcb->seq); 5591da177e4SLinus Torvalds th->urg = 1; 5601da177e4SLinus Torvalds } 5611da177e4SLinus Torvalds 562dfb4b9dcSDavid S. Miller if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) { 563df7a3b07SAl Viro tcp_syn_build_options((__be32 *)(th + 1), 5641da177e4SLinus Torvalds tcp_advertise_mss(sk), 5651da177e4SLinus Torvalds (sysctl_flags & SYSCTL_FLAG_TSTAMPS), 5661da177e4SLinus Torvalds (sysctl_flags & SYSCTL_FLAG_SACK), 5671da177e4SLinus Torvalds (sysctl_flags & SYSCTL_FLAG_WSCALE), 5681da177e4SLinus Torvalds tp->rx_opt.rcv_wscale, 5691da177e4SLinus Torvalds tcb->when, 570cfb6eeb4SYOSHIFUJI Hideaki tp->rx_opt.ts_recent, 571cfb6eeb4SYOSHIFUJI Hideaki 572cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 573cfb6eeb4SYOSHIFUJI Hideaki md5 ? &md5_hash_location : 574cfb6eeb4SYOSHIFUJI Hideaki #endif 575cfb6eeb4SYOSHIFUJI Hideaki NULL); 5761da177e4SLinus Torvalds } else { 577df7a3b07SAl Viro tcp_build_and_update_options((__be32 *)(th + 1), 578cfb6eeb4SYOSHIFUJI Hideaki tp, tcb->when, 579cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 580cfb6eeb4SYOSHIFUJI Hideaki md5 ? &md5_hash_location : 581cfb6eeb4SYOSHIFUJI Hideaki #endif 582cfb6eeb4SYOSHIFUJI Hideaki NULL); 5839e412ba7SIlpo Järvinen TCP_ECN_send(sk, skb, tcp_header_size); 5841da177e4SLinus Torvalds } 585dfb4b9dcSDavid S. Miller 586cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 587cfb6eeb4SYOSHIFUJI Hideaki /* Calculate the MD5 hash, as we have all we need now */ 588cfb6eeb4SYOSHIFUJI Hideaki if (md5) { 589cfb6eeb4SYOSHIFUJI Hideaki tp->af_specific->calc_md5_hash(md5_hash_location, 590cfb6eeb4SYOSHIFUJI Hideaki md5, 591cfb6eeb4SYOSHIFUJI Hideaki sk, NULL, NULL, 592aa8223c7SArnaldo Carvalho de Melo tcp_hdr(skb), 593cfb6eeb4SYOSHIFUJI Hideaki sk->sk_protocol, 594cfb6eeb4SYOSHIFUJI Hideaki skb->len); 595cfb6eeb4SYOSHIFUJI Hideaki } 596cfb6eeb4SYOSHIFUJI Hideaki #endif 597cfb6eeb4SYOSHIFUJI Hideaki 5988292a17aSArnaldo Carvalho de Melo icsk->icsk_af_ops->send_check(sk, skb->len, skb); 5991da177e4SLinus Torvalds 600dfb4b9dcSDavid S. Miller if (likely(tcb->flags & TCPCB_FLAG_ACK)) 601fc6415bcSDavid S. Miller tcp_event_ack_sent(sk, tcp_skb_pcount(skb)); 6021da177e4SLinus Torvalds 6031da177e4SLinus Torvalds if (skb->len != tcp_header_size) 6041da177e4SLinus Torvalds tcp_event_data_sent(tp, skb, sk); 6051da177e4SLinus Torvalds 606bd37a088SWei Yongjun if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq) 6071da177e4SLinus Torvalds TCP_INC_STATS(TCP_MIB_OUTSEGS); 6081da177e4SLinus Torvalds 609e89862f4SDavid S. Miller err = icsk->icsk_af_ops->queue_xmit(skb, 0); 61083de47cdSHua Zhong if (likely(err <= 0)) 6111da177e4SLinus Torvalds return err; 6121da177e4SLinus Torvalds 6133cfe3baaSIlpo Järvinen tcp_enter_cwr(sk, 1); 6141da177e4SLinus Torvalds 615b9df3cb8SGerrit Renker return net_xmit_eval(err); 616dfb4b9dcSDavid S. Miller 6171da177e4SLinus Torvalds #undef SYSCTL_FLAG_TSTAMPS 6181da177e4SLinus Torvalds #undef SYSCTL_FLAG_WSCALE 6191da177e4SLinus Torvalds #undef SYSCTL_FLAG_SACK 6201da177e4SLinus Torvalds } 6211da177e4SLinus Torvalds 6221da177e4SLinus Torvalds 6231da177e4SLinus Torvalds /* This routine just queue's the buffer 6241da177e4SLinus Torvalds * 6251da177e4SLinus Torvalds * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames, 6261da177e4SLinus Torvalds * otherwise socket can stall. 6271da177e4SLinus Torvalds */ 6281da177e4SLinus Torvalds static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) 6291da177e4SLinus Torvalds { 6301da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 6311da177e4SLinus Torvalds 6321da177e4SLinus Torvalds /* Advance write_seq and place onto the write_queue. */ 6331da177e4SLinus Torvalds tp->write_seq = TCP_SKB_CB(skb)->end_seq; 6341da177e4SLinus Torvalds skb_header_release(skb); 635fe067e8aSDavid S. Miller tcp_add_write_queue_tail(sk, skb); 6361da177e4SLinus Torvalds sk_charge_skb(sk, skb); 6371da177e4SLinus Torvalds } 6381da177e4SLinus Torvalds 639846998aeSDavid S. Miller static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now) 640f6302d1dSDavid S. Miller { 641bcd76111SHerbert Xu if (skb->len <= mss_now || !sk_can_gso(sk)) { 642f6302d1dSDavid S. Miller /* Avoid the costly divide in the normal 643f6302d1dSDavid S. Miller * non-TSO case. 644f6302d1dSDavid S. Miller */ 6457967168cSHerbert Xu skb_shinfo(skb)->gso_segs = 1; 6467967168cSHerbert Xu skb_shinfo(skb)->gso_size = 0; 6477967168cSHerbert Xu skb_shinfo(skb)->gso_type = 0; 648f6302d1dSDavid S. Miller } else { 649356f89e1SIlpo Järvinen skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now); 6507967168cSHerbert Xu skb_shinfo(skb)->gso_size = mss_now; 651bcd76111SHerbert Xu skb_shinfo(skb)->gso_type = sk->sk_gso_type; 6521da177e4SLinus Torvalds } 6531da177e4SLinus Torvalds } 6541da177e4SLinus Torvalds 65591fed7a1SIlpo Järvinen /* When a modification to fackets out becomes necessary, we need to check 65691fed7a1SIlpo Järvinen * skb is counted to fackets_out or not. Another important thing is to 65791fed7a1SIlpo Järvinen * tweak SACK fastpath hint too as it would overwrite all changes unless 65891fed7a1SIlpo Järvinen * hint is also changed. 65991fed7a1SIlpo Järvinen */ 66091fed7a1SIlpo Järvinen static void tcp_adjust_fackets_out(struct tcp_sock *tp, struct sk_buff *skb, 66191fed7a1SIlpo Järvinen int decr) 66291fed7a1SIlpo Järvinen { 66391fed7a1SIlpo Järvinen if (!tp->sacked_out) 66491fed7a1SIlpo Järvinen return; 66591fed7a1SIlpo Järvinen 66691fed7a1SIlpo Järvinen if (!before(tp->highest_sack, TCP_SKB_CB(skb)->seq)) 66791fed7a1SIlpo Järvinen tp->fackets_out -= decr; 66891fed7a1SIlpo Järvinen 66991fed7a1SIlpo Järvinen /* cnt_hint is "off-by-one" compared with fackets_out (see sacktag) */ 67091fed7a1SIlpo Järvinen if (tp->fastpath_skb_hint != NULL && 67191fed7a1SIlpo Järvinen after(TCP_SKB_CB(tp->fastpath_skb_hint)->seq, TCP_SKB_CB(skb)->seq)) 67291fed7a1SIlpo Järvinen tp->fastpath_cnt_hint -= decr; 67391fed7a1SIlpo Järvinen } 67491fed7a1SIlpo Järvinen 6751da177e4SLinus Torvalds /* Function to create two new TCP segments. Shrinks the given segment 6761da177e4SLinus Torvalds * to the specified size and appends a new segment with the rest of the 6771da177e4SLinus Torvalds * packet to the list. This won't be called frequently, I hope. 6781da177e4SLinus Torvalds * Remember, these are still headerless SKBs at this point. 6791da177e4SLinus Torvalds */ 6806475be16SDavid S. Miller int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss_now) 6811da177e4SLinus Torvalds { 6821da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 6831da177e4SLinus Torvalds struct sk_buff *buff; 6846475be16SDavid S. Miller int nsize, old_factor; 685b60b49eaSHerbert Xu int nlen; 6861da177e4SLinus Torvalds u16 flags; 6871da177e4SLinus Torvalds 688b2cc99f0SHerbert Xu BUG_ON(len > skb->len); 6896a438bbeSStephen Hemminger 690b7689205SIlpo Järvinen tcp_clear_retrans_hints_partial(tp); 6911da177e4SLinus Torvalds nsize = skb_headlen(skb) - len; 6921da177e4SLinus Torvalds if (nsize < 0) 6931da177e4SLinus Torvalds nsize = 0; 6941da177e4SLinus Torvalds 6951da177e4SLinus Torvalds if (skb_cloned(skb) && 6961da177e4SLinus Torvalds skb_is_nonlinear(skb) && 6971da177e4SLinus Torvalds pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) 6981da177e4SLinus Torvalds return -ENOMEM; 6991da177e4SLinus Torvalds 7001da177e4SLinus Torvalds /* Get a new skb... force flag on. */ 7011da177e4SLinus Torvalds buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC); 7021da177e4SLinus Torvalds if (buff == NULL) 7031da177e4SLinus Torvalds return -ENOMEM; /* We'll just try again later. */ 704ef5cb973SHerbert Xu 705b60b49eaSHerbert Xu sk_charge_skb(sk, buff); 706b60b49eaSHerbert Xu nlen = skb->len - len - nsize; 707b60b49eaSHerbert Xu buff->truesize += nlen; 708b60b49eaSHerbert Xu skb->truesize -= nlen; 7091da177e4SLinus Torvalds 7101da177e4SLinus Torvalds /* Correct the sequence numbers. */ 7111da177e4SLinus Torvalds TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; 7121da177e4SLinus Torvalds TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; 7131da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; 7141da177e4SLinus Torvalds 7150dde7b54SIlpo Järvinen if (tp->sacked_out && (TCP_SKB_CB(skb)->seq == tp->highest_sack)) 7160dde7b54SIlpo Järvinen tp->highest_sack = TCP_SKB_CB(buff)->seq; 7170dde7b54SIlpo Järvinen 7181da177e4SLinus Torvalds /* PSH and FIN should only be set in the second packet. */ 7191da177e4SLinus Torvalds flags = TCP_SKB_CB(skb)->flags; 7201da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH); 7211da177e4SLinus Torvalds TCP_SKB_CB(buff)->flags = flags; 722e14c3cafSHerbert Xu TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked; 7231da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked &= ~TCPCB_AT_TAIL; 7241da177e4SLinus Torvalds 72584fa7933SPatrick McHardy if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) { 7261da177e4SLinus Torvalds /* Copy and checksum data tail into the new buffer. */ 7271da177e4SLinus Torvalds buff->csum = csum_partial_copy_nocheck(skb->data + len, skb_put(buff, nsize), 7281da177e4SLinus Torvalds nsize, 0); 7291da177e4SLinus Torvalds 7301da177e4SLinus Torvalds skb_trim(skb, len); 7311da177e4SLinus Torvalds 7321da177e4SLinus Torvalds skb->csum = csum_block_sub(skb->csum, buff->csum, len); 7331da177e4SLinus Torvalds } else { 73484fa7933SPatrick McHardy skb->ip_summed = CHECKSUM_PARTIAL; 7351da177e4SLinus Torvalds skb_split(skb, buff, len); 7361da177e4SLinus Torvalds } 7371da177e4SLinus Torvalds 7381da177e4SLinus Torvalds buff->ip_summed = skb->ip_summed; 7391da177e4SLinus Torvalds 7401da177e4SLinus Torvalds /* Looks stupid, but our code really uses when of 7411da177e4SLinus Torvalds * skbs, which it never sent before. --ANK 7421da177e4SLinus Torvalds */ 7431da177e4SLinus Torvalds TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when; 744a61bbcf2SPatrick McHardy buff->tstamp = skb->tstamp; 7451da177e4SLinus Torvalds 7466475be16SDavid S. Miller old_factor = tcp_skb_pcount(skb); 7476475be16SDavid S. Miller 7481da177e4SLinus Torvalds /* Fix up tso_factor for both original and new SKB. */ 749846998aeSDavid S. Miller tcp_set_skb_tso_segs(sk, skb, mss_now); 750846998aeSDavid S. Miller tcp_set_skb_tso_segs(sk, buff, mss_now); 7511da177e4SLinus Torvalds 7526475be16SDavid S. Miller /* If this packet has been sent out already, we must 7536475be16SDavid S. Miller * adjust the various packet counters. 7546475be16SDavid S. Miller */ 755cf0b450cSHerbert Xu if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) { 7566475be16SDavid S. Miller int diff = old_factor - tcp_skb_pcount(skb) - 7576475be16SDavid S. Miller tcp_skb_pcount(buff); 7581da177e4SLinus Torvalds 7596475be16SDavid S. Miller tp->packets_out -= diff; 760e14c3cafSHerbert Xu 761e14c3cafSHerbert Xu if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) 762e14c3cafSHerbert Xu tp->sacked_out -= diff; 763e14c3cafSHerbert Xu if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) 764e14c3cafSHerbert Xu tp->retrans_out -= diff; 765e14c3cafSHerbert Xu 766b5860bbaSIlpo Järvinen if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) 7676475be16SDavid S. Miller tp->lost_out -= diff; 76883ca28beSHerbert Xu 76983ca28beSHerbert Xu /* Adjust Reno SACK estimate. */ 77091fed7a1SIlpo Järvinen if (tcp_is_reno(tp) && diff > 0) { 771af610b4cSIlpo Järvinen tcp_dec_pcount_approx_int(&tp->sacked_out, diff); 772005903bcSIlpo Järvinen tcp_verify_left_out(tp); 77383ca28beSHerbert Xu } 77491fed7a1SIlpo Järvinen tcp_adjust_fackets_out(tp, skb, diff); 7751da177e4SLinus Torvalds } 7761da177e4SLinus Torvalds 7771da177e4SLinus Torvalds /* Link BUFF into the send queue. */ 778f44b5271SDavid S. Miller skb_header_release(buff); 779fe067e8aSDavid S. Miller tcp_insert_write_queue_after(skb, buff, sk); 7801da177e4SLinus Torvalds 7811da177e4SLinus Torvalds return 0; 7821da177e4SLinus Torvalds } 7831da177e4SLinus Torvalds 7841da177e4SLinus Torvalds /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c 7851da177e4SLinus Torvalds * eventually). The difference is that pulled data not copied, but 7861da177e4SLinus Torvalds * immediately discarded. 7871da177e4SLinus Torvalds */ 788f2911969SHerbert Xu ~{PmVHI~} static void __pskb_trim_head(struct sk_buff *skb, int len) 7891da177e4SLinus Torvalds { 7901da177e4SLinus Torvalds int i, k, eat; 7911da177e4SLinus Torvalds 7921da177e4SLinus Torvalds eat = len; 7931da177e4SLinus Torvalds k = 0; 7941da177e4SLinus Torvalds for (i=0; i<skb_shinfo(skb)->nr_frags; i++) { 7951da177e4SLinus Torvalds if (skb_shinfo(skb)->frags[i].size <= eat) { 7961da177e4SLinus Torvalds put_page(skb_shinfo(skb)->frags[i].page); 7971da177e4SLinus Torvalds eat -= skb_shinfo(skb)->frags[i].size; 7981da177e4SLinus Torvalds } else { 7991da177e4SLinus Torvalds skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i]; 8001da177e4SLinus Torvalds if (eat) { 8011da177e4SLinus Torvalds skb_shinfo(skb)->frags[k].page_offset += eat; 8021da177e4SLinus Torvalds skb_shinfo(skb)->frags[k].size -= eat; 8031da177e4SLinus Torvalds eat = 0; 8041da177e4SLinus Torvalds } 8051da177e4SLinus Torvalds k++; 8061da177e4SLinus Torvalds } 8071da177e4SLinus Torvalds } 8081da177e4SLinus Torvalds skb_shinfo(skb)->nr_frags = k; 8091da177e4SLinus Torvalds 81027a884dcSArnaldo Carvalho de Melo skb_reset_tail_pointer(skb); 8111da177e4SLinus Torvalds skb->data_len -= len; 8121da177e4SLinus Torvalds skb->len = skb->data_len; 8131da177e4SLinus Torvalds } 8141da177e4SLinus Torvalds 8151da177e4SLinus Torvalds int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) 8161da177e4SLinus Torvalds { 8171da177e4SLinus Torvalds if (skb_cloned(skb) && 8181da177e4SLinus Torvalds pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) 8191da177e4SLinus Torvalds return -ENOMEM; 8201da177e4SLinus Torvalds 821f2911969SHerbert Xu ~{PmVHI~} /* If len == headlen, we avoid __skb_pull to preserve alignment. */ 822f2911969SHerbert Xu ~{PmVHI~} if (unlikely(len < skb_headlen(skb))) 8231da177e4SLinus Torvalds __skb_pull(skb, len); 824f2911969SHerbert Xu ~{PmVHI~} else 825f2911969SHerbert Xu ~{PmVHI~} __pskb_trim_head(skb, len - skb_headlen(skb)); 8261da177e4SLinus Torvalds 8271da177e4SLinus Torvalds TCP_SKB_CB(skb)->seq += len; 82884fa7933SPatrick McHardy skb->ip_summed = CHECKSUM_PARTIAL; 8291da177e4SLinus Torvalds 8301da177e4SLinus Torvalds skb->truesize -= len; 8311da177e4SLinus Torvalds sk->sk_wmem_queued -= len; 8321da177e4SLinus Torvalds sk->sk_forward_alloc += len; 8331da177e4SLinus Torvalds sock_set_flag(sk, SOCK_QUEUE_SHRUNK); 8341da177e4SLinus Torvalds 8351da177e4SLinus Torvalds /* Any change of skb->len requires recalculation of tso 8361da177e4SLinus Torvalds * factor and mss. 8371da177e4SLinus Torvalds */ 8381da177e4SLinus Torvalds if (tcp_skb_pcount(skb) > 1) 839846998aeSDavid S. Miller tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk, 1)); 8401da177e4SLinus Torvalds 8411da177e4SLinus Torvalds return 0; 8421da177e4SLinus Torvalds } 8431da177e4SLinus Torvalds 8445d424d5aSJohn Heffner /* Not accounting for SACKs here. */ 8455d424d5aSJohn Heffner int tcp_mtu_to_mss(struct sock *sk, int pmtu) 8465d424d5aSJohn Heffner { 8475d424d5aSJohn Heffner struct tcp_sock *tp = tcp_sk(sk); 8485d424d5aSJohn Heffner struct inet_connection_sock *icsk = inet_csk(sk); 8495d424d5aSJohn Heffner int mss_now; 8505d424d5aSJohn Heffner 8515d424d5aSJohn Heffner /* Calculate base mss without TCP options: 8525d424d5aSJohn Heffner It is MMS_S - sizeof(tcphdr) of rfc1122 8535d424d5aSJohn Heffner */ 8545d424d5aSJohn Heffner mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr); 8555d424d5aSJohn Heffner 8565d424d5aSJohn Heffner /* Clamp it (mss_clamp does not include tcp options) */ 8575d424d5aSJohn Heffner if (mss_now > tp->rx_opt.mss_clamp) 8585d424d5aSJohn Heffner mss_now = tp->rx_opt.mss_clamp; 8595d424d5aSJohn Heffner 8605d424d5aSJohn Heffner /* Now subtract optional transport overhead */ 8615d424d5aSJohn Heffner mss_now -= icsk->icsk_ext_hdr_len; 8625d424d5aSJohn Heffner 8635d424d5aSJohn Heffner /* Then reserve room for full set of TCP options and 8 bytes of data */ 8645d424d5aSJohn Heffner if (mss_now < 48) 8655d424d5aSJohn Heffner mss_now = 48; 8665d424d5aSJohn Heffner 8675d424d5aSJohn Heffner /* Now subtract TCP options size, not including SACKs */ 8685d424d5aSJohn Heffner mss_now -= tp->tcp_header_len - sizeof(struct tcphdr); 8695d424d5aSJohn Heffner 8705d424d5aSJohn Heffner return mss_now; 8715d424d5aSJohn Heffner } 8725d424d5aSJohn Heffner 8735d424d5aSJohn Heffner /* Inverse of above */ 8745d424d5aSJohn Heffner int tcp_mss_to_mtu(struct sock *sk, int mss) 8755d424d5aSJohn Heffner { 8765d424d5aSJohn Heffner struct tcp_sock *tp = tcp_sk(sk); 8775d424d5aSJohn Heffner struct inet_connection_sock *icsk = inet_csk(sk); 8785d424d5aSJohn Heffner int mtu; 8795d424d5aSJohn Heffner 8805d424d5aSJohn Heffner mtu = mss + 8815d424d5aSJohn Heffner tp->tcp_header_len + 8825d424d5aSJohn Heffner icsk->icsk_ext_hdr_len + 8835d424d5aSJohn Heffner icsk->icsk_af_ops->net_header_len; 8845d424d5aSJohn Heffner 8855d424d5aSJohn Heffner return mtu; 8865d424d5aSJohn Heffner } 8875d424d5aSJohn Heffner 8885d424d5aSJohn Heffner void tcp_mtup_init(struct sock *sk) 8895d424d5aSJohn Heffner { 8905d424d5aSJohn Heffner struct tcp_sock *tp = tcp_sk(sk); 8915d424d5aSJohn Heffner struct inet_connection_sock *icsk = inet_csk(sk); 8925d424d5aSJohn Heffner 8935d424d5aSJohn Heffner icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1; 8945d424d5aSJohn Heffner icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) + 8955d424d5aSJohn Heffner icsk->icsk_af_ops->net_header_len; 8965d424d5aSJohn Heffner icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss); 8975d424d5aSJohn Heffner icsk->icsk_mtup.probe_size = 0; 8985d424d5aSJohn Heffner } 8995d424d5aSJohn Heffner 9001da177e4SLinus Torvalds /* This function synchronize snd mss to current pmtu/exthdr set. 9011da177e4SLinus Torvalds 9021da177e4SLinus Torvalds tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts 9031da177e4SLinus Torvalds for TCP options, but includes only bare TCP header. 9041da177e4SLinus Torvalds 9051da177e4SLinus Torvalds tp->rx_opt.mss_clamp is mss negotiated at connection setup. 906caa20d9aSStephen Hemminger It is minimum of user_mss and mss received with SYN. 9071da177e4SLinus Torvalds It also does not include TCP options. 9081da177e4SLinus Torvalds 909d83d8461SArnaldo Carvalho de Melo inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function. 9101da177e4SLinus Torvalds 9111da177e4SLinus Torvalds tp->mss_cache is current effective sending mss, including 9121da177e4SLinus Torvalds all tcp options except for SACKs. It is evaluated, 9131da177e4SLinus Torvalds taking into account current pmtu, but never exceeds 9141da177e4SLinus Torvalds tp->rx_opt.mss_clamp. 9151da177e4SLinus Torvalds 9161da177e4SLinus Torvalds NOTE1. rfc1122 clearly states that advertised MSS 9171da177e4SLinus Torvalds DOES NOT include either tcp or ip options. 9181da177e4SLinus Torvalds 919d83d8461SArnaldo Carvalho de Melo NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache 920d83d8461SArnaldo Carvalho de Melo are READ ONLY outside this function. --ANK (980731) 9211da177e4SLinus Torvalds */ 9221da177e4SLinus Torvalds 9231da177e4SLinus Torvalds unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu) 9241da177e4SLinus Torvalds { 9251da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 926d83d8461SArnaldo Carvalho de Melo struct inet_connection_sock *icsk = inet_csk(sk); 9275d424d5aSJohn Heffner int mss_now; 9281da177e4SLinus Torvalds 9295d424d5aSJohn Heffner if (icsk->icsk_mtup.search_high > pmtu) 9305d424d5aSJohn Heffner icsk->icsk_mtup.search_high = pmtu; 9311da177e4SLinus Torvalds 9325d424d5aSJohn Heffner mss_now = tcp_mtu_to_mss(sk, pmtu); 9331da177e4SLinus Torvalds 9341da177e4SLinus Torvalds /* Bound mss with half of window */ 9351da177e4SLinus Torvalds if (tp->max_window && mss_now > (tp->max_window>>1)) 9361da177e4SLinus Torvalds mss_now = max((tp->max_window>>1), 68U - tp->tcp_header_len); 9371da177e4SLinus Torvalds 9381da177e4SLinus Torvalds /* And store cached results */ 939d83d8461SArnaldo Carvalho de Melo icsk->icsk_pmtu_cookie = pmtu; 9405d424d5aSJohn Heffner if (icsk->icsk_mtup.enabled) 9415d424d5aSJohn Heffner mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)); 942c1b4a7e6SDavid S. Miller tp->mss_cache = mss_now; 9431da177e4SLinus Torvalds 9441da177e4SLinus Torvalds return mss_now; 9451da177e4SLinus Torvalds } 9461da177e4SLinus Torvalds 9471da177e4SLinus Torvalds /* Compute the current effective MSS, taking SACKs and IP options, 9481da177e4SLinus Torvalds * and even PMTU discovery events into account. 9491da177e4SLinus Torvalds * 9501da177e4SLinus Torvalds * LARGESEND note: !urg_mode is overkill, only frames up to snd_up 9511da177e4SLinus Torvalds * cannot be large. However, taking into account rare use of URG, this 9521da177e4SLinus Torvalds * is not a big flaw. 9531da177e4SLinus Torvalds */ 954c1b4a7e6SDavid S. Miller unsigned int tcp_current_mss(struct sock *sk, int large_allowed) 9551da177e4SLinus Torvalds { 9561da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 9571da177e4SLinus Torvalds struct dst_entry *dst = __sk_dst_get(sk); 958c1b4a7e6SDavid S. Miller u32 mss_now; 959c1b4a7e6SDavid S. Miller u16 xmit_size_goal; 960c1b4a7e6SDavid S. Miller int doing_tso = 0; 9611da177e4SLinus Torvalds 962c1b4a7e6SDavid S. Miller mss_now = tp->mss_cache; 963c1b4a7e6SDavid S. Miller 964bcd76111SHerbert Xu if (large_allowed && sk_can_gso(sk) && !tp->urg_mode) 965c1b4a7e6SDavid S. Miller doing_tso = 1; 966c1b4a7e6SDavid S. Miller 9671da177e4SLinus Torvalds if (dst) { 9681da177e4SLinus Torvalds u32 mtu = dst_mtu(dst); 969d83d8461SArnaldo Carvalho de Melo if (mtu != inet_csk(sk)->icsk_pmtu_cookie) 9701da177e4SLinus Torvalds mss_now = tcp_sync_mss(sk, mtu); 9711da177e4SLinus Torvalds } 9721da177e4SLinus Torvalds 9731da177e4SLinus Torvalds if (tp->rx_opt.eff_sacks) 9741da177e4SLinus Torvalds mss_now -= (TCPOLEN_SACK_BASE_ALIGNED + 9751da177e4SLinus Torvalds (tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK)); 976c1b4a7e6SDavid S. Miller 977cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 978cfb6eeb4SYOSHIFUJI Hideaki if (tp->af_specific->md5_lookup(sk, sk)) 979cfb6eeb4SYOSHIFUJI Hideaki mss_now -= TCPOLEN_MD5SIG_ALIGNED; 980cfb6eeb4SYOSHIFUJI Hideaki #endif 981cfb6eeb4SYOSHIFUJI Hideaki 982c1b4a7e6SDavid S. Miller xmit_size_goal = mss_now; 983c1b4a7e6SDavid S. Miller 984c1b4a7e6SDavid S. Miller if (doing_tso) { 9858292a17aSArnaldo Carvalho de Melo xmit_size_goal = (65535 - 9868292a17aSArnaldo Carvalho de Melo inet_csk(sk)->icsk_af_ops->net_header_len - 987d83d8461SArnaldo Carvalho de Melo inet_csk(sk)->icsk_ext_hdr_len - 988d83d8461SArnaldo Carvalho de Melo tp->tcp_header_len); 989c1b4a7e6SDavid S. Miller 990c1b4a7e6SDavid S. Miller if (tp->max_window && 991c1b4a7e6SDavid S. Miller (xmit_size_goal > (tp->max_window >> 1))) 992c1b4a7e6SDavid S. Miller xmit_size_goal = max((tp->max_window >> 1), 993c1b4a7e6SDavid S. Miller 68U - tp->tcp_header_len); 994c1b4a7e6SDavid S. Miller 995c1b4a7e6SDavid S. Miller xmit_size_goal -= (xmit_size_goal % mss_now); 996c1b4a7e6SDavid S. Miller } 997c1b4a7e6SDavid S. Miller tp->xmit_size_goal = xmit_size_goal; 998c1b4a7e6SDavid S. Miller 9991da177e4SLinus Torvalds return mss_now; 10001da177e4SLinus Torvalds } 10011da177e4SLinus Torvalds 1002a762a980SDavid S. Miller /* Congestion window validation. (RFC2861) */ 1003a762a980SDavid S. Miller 10049e412ba7SIlpo Järvinen static void tcp_cwnd_validate(struct sock *sk) 1005a762a980SDavid S. Miller { 10069e412ba7SIlpo Järvinen struct tcp_sock *tp = tcp_sk(sk); 1007a762a980SDavid S. Miller __u32 packets_out = tp->packets_out; 1008a762a980SDavid S. Miller 1009a762a980SDavid S. Miller if (packets_out >= tp->snd_cwnd) { 1010a762a980SDavid S. Miller /* Network is feed fully. */ 1011a762a980SDavid S. Miller tp->snd_cwnd_used = 0; 1012a762a980SDavid S. Miller tp->snd_cwnd_stamp = tcp_time_stamp; 1013a762a980SDavid S. Miller } else { 1014a762a980SDavid S. Miller /* Network starves. */ 1015a762a980SDavid S. Miller if (tp->packets_out > tp->snd_cwnd_used) 1016a762a980SDavid S. Miller tp->snd_cwnd_used = tp->packets_out; 1017a762a980SDavid S. Miller 101815d33c07SDavid S. Miller if (sysctl_tcp_slow_start_after_idle && 101915d33c07SDavid S. Miller (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto) 1020a762a980SDavid S. Miller tcp_cwnd_application_limited(sk); 1021a762a980SDavid S. Miller } 1022a762a980SDavid S. Miller } 1023a762a980SDavid S. Miller 1024c1b4a7e6SDavid S. Miller static unsigned int tcp_window_allows(struct tcp_sock *tp, struct sk_buff *skb, unsigned int mss_now, unsigned int cwnd) 1025c1b4a7e6SDavid S. Miller { 1026c1b4a7e6SDavid S. Miller u32 window, cwnd_len; 1027c1b4a7e6SDavid S. Miller 1028c1b4a7e6SDavid S. Miller window = (tp->snd_una + tp->snd_wnd - TCP_SKB_CB(skb)->seq); 1029c1b4a7e6SDavid S. Miller cwnd_len = mss_now * cwnd; 1030c1b4a7e6SDavid S. Miller return min(window, cwnd_len); 1031c1b4a7e6SDavid S. Miller } 1032c1b4a7e6SDavid S. Miller 1033c1b4a7e6SDavid S. Miller /* Can at least one segment of SKB be sent right now, according to the 1034c1b4a7e6SDavid S. Miller * congestion window rules? If so, return how many segments are allowed. 1035c1b4a7e6SDavid S. Miller */ 1036c1b4a7e6SDavid S. Miller static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp, struct sk_buff *skb) 1037c1b4a7e6SDavid S. Miller { 1038c1b4a7e6SDavid S. Miller u32 in_flight, cwnd; 1039c1b4a7e6SDavid S. Miller 1040c1b4a7e6SDavid S. Miller /* Don't be strict about the congestion window for the final FIN. */ 1041104439a8SJohn Heffner if ((TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) && 1042104439a8SJohn Heffner tcp_skb_pcount(skb) == 1) 1043c1b4a7e6SDavid S. Miller return 1; 1044c1b4a7e6SDavid S. Miller 1045c1b4a7e6SDavid S. Miller in_flight = tcp_packets_in_flight(tp); 1046c1b4a7e6SDavid S. Miller cwnd = tp->snd_cwnd; 1047c1b4a7e6SDavid S. Miller if (in_flight < cwnd) 1048c1b4a7e6SDavid S. Miller return (cwnd - in_flight); 1049c1b4a7e6SDavid S. Miller 1050c1b4a7e6SDavid S. Miller return 0; 1051c1b4a7e6SDavid S. Miller } 1052c1b4a7e6SDavid S. Miller 1053c1b4a7e6SDavid S. Miller /* This must be invoked the first time we consider transmitting 1054c1b4a7e6SDavid S. Miller * SKB onto the wire. 1055c1b4a7e6SDavid S. Miller */ 105640efc6faSStephen Hemminger static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now) 1057c1b4a7e6SDavid S. Miller { 1058c1b4a7e6SDavid S. Miller int tso_segs = tcp_skb_pcount(skb); 1059c1b4a7e6SDavid S. Miller 1060846998aeSDavid S. Miller if (!tso_segs || 1061846998aeSDavid S. Miller (tso_segs > 1 && 10627967168cSHerbert Xu tcp_skb_mss(skb) != mss_now)) { 1063846998aeSDavid S. Miller tcp_set_skb_tso_segs(sk, skb, mss_now); 1064c1b4a7e6SDavid S. Miller tso_segs = tcp_skb_pcount(skb); 1065c1b4a7e6SDavid S. Miller } 1066c1b4a7e6SDavid S. Miller return tso_segs; 1067c1b4a7e6SDavid S. Miller } 1068c1b4a7e6SDavid S. Miller 1069c1b4a7e6SDavid S. Miller static inline int tcp_minshall_check(const struct tcp_sock *tp) 1070c1b4a7e6SDavid S. Miller { 1071c1b4a7e6SDavid S. Miller return after(tp->snd_sml,tp->snd_una) && 1072c1b4a7e6SDavid S. Miller !after(tp->snd_sml, tp->snd_nxt); 1073c1b4a7e6SDavid S. Miller } 1074c1b4a7e6SDavid S. Miller 1075c1b4a7e6SDavid S. Miller /* Return 0, if packet can be sent now without violation Nagle's rules: 1076c1b4a7e6SDavid S. Miller * 1. It is full sized. 1077c1b4a7e6SDavid S. Miller * 2. Or it contains FIN. (already checked by caller) 1078c1b4a7e6SDavid S. Miller * 3. Or TCP_NODELAY was set. 1079c1b4a7e6SDavid S. Miller * 4. Or TCP_CORK is not set, and all sent packets are ACKed. 1080c1b4a7e6SDavid S. Miller * With Minshall's modification: all sent small packets are ACKed. 1081c1b4a7e6SDavid S. Miller */ 1082c1b4a7e6SDavid S. Miller 1083c1b4a7e6SDavid S. Miller static inline int tcp_nagle_check(const struct tcp_sock *tp, 1084c1b4a7e6SDavid S. Miller const struct sk_buff *skb, 1085c1b4a7e6SDavid S. Miller unsigned mss_now, int nonagle) 1086c1b4a7e6SDavid S. Miller { 1087c1b4a7e6SDavid S. Miller return (skb->len < mss_now && 1088c1b4a7e6SDavid S. Miller ((nonagle&TCP_NAGLE_CORK) || 1089c1b4a7e6SDavid S. Miller (!nonagle && 1090c1b4a7e6SDavid S. Miller tp->packets_out && 1091c1b4a7e6SDavid S. Miller tcp_minshall_check(tp)))); 1092c1b4a7e6SDavid S. Miller } 1093c1b4a7e6SDavid S. Miller 1094c1b4a7e6SDavid S. Miller /* Return non-zero if the Nagle test allows this packet to be 1095c1b4a7e6SDavid S. Miller * sent now. 1096c1b4a7e6SDavid S. Miller */ 1097c1b4a7e6SDavid S. Miller static inline int tcp_nagle_test(struct tcp_sock *tp, struct sk_buff *skb, 1098c1b4a7e6SDavid S. Miller unsigned int cur_mss, int nonagle) 1099c1b4a7e6SDavid S. Miller { 1100c1b4a7e6SDavid S. Miller /* Nagle rule does not apply to frames, which sit in the middle of the 1101c1b4a7e6SDavid S. Miller * write_queue (they have no chances to get new data). 1102c1b4a7e6SDavid S. Miller * 1103c1b4a7e6SDavid S. Miller * This is implemented in the callers, where they modify the 'nonagle' 1104c1b4a7e6SDavid S. Miller * argument based upon the location of SKB in the send queue. 1105c1b4a7e6SDavid S. Miller */ 1106c1b4a7e6SDavid S. Miller if (nonagle & TCP_NAGLE_PUSH) 1107c1b4a7e6SDavid S. Miller return 1; 1108c1b4a7e6SDavid S. Miller 1109d551e454SIlpo Järvinen /* Don't use the nagle rule for urgent data (or for the final FIN). 1110d551e454SIlpo Järvinen * Nagle can be ignored during F-RTO too (see RFC4138). 1111d551e454SIlpo Järvinen */ 1112d551e454SIlpo Järvinen if (tp->urg_mode || (tp->frto_counter == 2) || 1113c1b4a7e6SDavid S. Miller (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)) 1114c1b4a7e6SDavid S. Miller return 1; 1115c1b4a7e6SDavid S. Miller 1116c1b4a7e6SDavid S. Miller if (!tcp_nagle_check(tp, skb, cur_mss, nonagle)) 1117c1b4a7e6SDavid S. Miller return 1; 1118c1b4a7e6SDavid S. Miller 1119c1b4a7e6SDavid S. Miller return 0; 1120c1b4a7e6SDavid S. Miller } 1121c1b4a7e6SDavid S. Miller 1122c1b4a7e6SDavid S. Miller /* Does at least the first segment of SKB fit into the send window? */ 1123c1b4a7e6SDavid S. Miller static inline int tcp_snd_wnd_test(struct tcp_sock *tp, struct sk_buff *skb, unsigned int cur_mss) 1124c1b4a7e6SDavid S. Miller { 1125c1b4a7e6SDavid S. Miller u32 end_seq = TCP_SKB_CB(skb)->end_seq; 1126c1b4a7e6SDavid S. Miller 1127c1b4a7e6SDavid S. Miller if (skb->len > cur_mss) 1128c1b4a7e6SDavid S. Miller end_seq = TCP_SKB_CB(skb)->seq + cur_mss; 1129c1b4a7e6SDavid S. Miller 1130c1b4a7e6SDavid S. Miller return !after(end_seq, tp->snd_una + tp->snd_wnd); 1131c1b4a7e6SDavid S. Miller } 1132c1b4a7e6SDavid S. Miller 1133fe067e8aSDavid S. Miller /* This checks if the data bearing packet SKB (usually tcp_send_head(sk)) 1134c1b4a7e6SDavid S. Miller * should be put on the wire right now. If so, it returns the number of 1135c1b4a7e6SDavid S. Miller * packets allowed by the congestion window. 1136c1b4a7e6SDavid S. Miller */ 1137c1b4a7e6SDavid S. Miller static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb, 1138c1b4a7e6SDavid S. Miller unsigned int cur_mss, int nonagle) 1139c1b4a7e6SDavid S. Miller { 1140c1b4a7e6SDavid S. Miller struct tcp_sock *tp = tcp_sk(sk); 1141c1b4a7e6SDavid S. Miller unsigned int cwnd_quota; 1142c1b4a7e6SDavid S. Miller 1143846998aeSDavid S. Miller tcp_init_tso_segs(sk, skb, cur_mss); 1144c1b4a7e6SDavid S. Miller 1145c1b4a7e6SDavid S. Miller if (!tcp_nagle_test(tp, skb, cur_mss, nonagle)) 1146c1b4a7e6SDavid S. Miller return 0; 1147c1b4a7e6SDavid S. Miller 1148c1b4a7e6SDavid S. Miller cwnd_quota = tcp_cwnd_test(tp, skb); 1149c1b4a7e6SDavid S. Miller if (cwnd_quota && 1150c1b4a7e6SDavid S. Miller !tcp_snd_wnd_test(tp, skb, cur_mss)) 1151c1b4a7e6SDavid S. Miller cwnd_quota = 0; 1152c1b4a7e6SDavid S. Miller 1153c1b4a7e6SDavid S. Miller return cwnd_quota; 1154c1b4a7e6SDavid S. Miller } 1155c1b4a7e6SDavid S. Miller 11569e412ba7SIlpo Järvinen int tcp_may_send_now(struct sock *sk) 1157c1b4a7e6SDavid S. Miller { 11589e412ba7SIlpo Järvinen struct tcp_sock *tp = tcp_sk(sk); 1159fe067e8aSDavid S. Miller struct sk_buff *skb = tcp_send_head(sk); 1160c1b4a7e6SDavid S. Miller 1161c1b4a7e6SDavid S. Miller return (skb && 1162c1b4a7e6SDavid S. Miller tcp_snd_test(sk, skb, tcp_current_mss(sk, 1), 1163c1b4a7e6SDavid S. Miller (tcp_skb_is_last(sk, skb) ? 1164c1b4a7e6SDavid S. Miller TCP_NAGLE_PUSH : 1165c1b4a7e6SDavid S. Miller tp->nonagle))); 1166c1b4a7e6SDavid S. Miller } 1167c1b4a7e6SDavid S. Miller 1168c1b4a7e6SDavid S. Miller /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet 1169c1b4a7e6SDavid S. Miller * which is put after SKB on the list. It is very much like 1170c1b4a7e6SDavid S. Miller * tcp_fragment() except that it may make several kinds of assumptions 1171c1b4a7e6SDavid S. Miller * in order to speed up the splitting operation. In particular, we 1172c1b4a7e6SDavid S. Miller * know that all the data is in scatter-gather pages, and that the 1173c1b4a7e6SDavid S. Miller * packet has never been sent out before (and thus is not cloned). 1174c1b4a7e6SDavid S. Miller */ 1175846998aeSDavid S. Miller static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, unsigned int mss_now) 1176c1b4a7e6SDavid S. Miller { 1177c1b4a7e6SDavid S. Miller struct sk_buff *buff; 1178c1b4a7e6SDavid S. Miller int nlen = skb->len - len; 1179c1b4a7e6SDavid S. Miller u16 flags; 1180c1b4a7e6SDavid S. Miller 1181c1b4a7e6SDavid S. Miller /* All of a TSO frame must be composed of paged data. */ 1182c8ac3774SHerbert Xu if (skb->len != skb->data_len) 1183c8ac3774SHerbert Xu return tcp_fragment(sk, skb, len, mss_now); 1184c1b4a7e6SDavid S. Miller 1185c1b4a7e6SDavid S. Miller buff = sk_stream_alloc_pskb(sk, 0, 0, GFP_ATOMIC); 1186c1b4a7e6SDavid S. Miller if (unlikely(buff == NULL)) 1187c1b4a7e6SDavid S. Miller return -ENOMEM; 1188c1b4a7e6SDavid S. Miller 1189b60b49eaSHerbert Xu sk_charge_skb(sk, buff); 1190b60b49eaSHerbert Xu buff->truesize += nlen; 1191c1b4a7e6SDavid S. Miller skb->truesize -= nlen; 1192c1b4a7e6SDavid S. Miller 1193c1b4a7e6SDavid S. Miller /* Correct the sequence numbers. */ 1194c1b4a7e6SDavid S. Miller TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; 1195c1b4a7e6SDavid S. Miller TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; 1196c1b4a7e6SDavid S. Miller TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; 1197c1b4a7e6SDavid S. Miller 1198c1b4a7e6SDavid S. Miller /* PSH and FIN should only be set in the second packet. */ 1199c1b4a7e6SDavid S. Miller flags = TCP_SKB_CB(skb)->flags; 1200c1b4a7e6SDavid S. Miller TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH); 1201c1b4a7e6SDavid S. Miller TCP_SKB_CB(buff)->flags = flags; 1202c1b4a7e6SDavid S. Miller 1203c1b4a7e6SDavid S. Miller /* This packet was never sent out yet, so no SACK bits. */ 1204c1b4a7e6SDavid S. Miller TCP_SKB_CB(buff)->sacked = 0; 1205c1b4a7e6SDavid S. Miller 120684fa7933SPatrick McHardy buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL; 1207c1b4a7e6SDavid S. Miller skb_split(skb, buff, len); 1208c1b4a7e6SDavid S. Miller 1209c1b4a7e6SDavid S. Miller /* Fix up tso_factor for both original and new SKB. */ 1210846998aeSDavid S. Miller tcp_set_skb_tso_segs(sk, skb, mss_now); 1211846998aeSDavid S. Miller tcp_set_skb_tso_segs(sk, buff, mss_now); 1212c1b4a7e6SDavid S. Miller 1213c1b4a7e6SDavid S. Miller /* Link BUFF into the send queue. */ 1214c1b4a7e6SDavid S. Miller skb_header_release(buff); 1215fe067e8aSDavid S. Miller tcp_insert_write_queue_after(skb, buff, sk); 1216c1b4a7e6SDavid S. Miller 1217c1b4a7e6SDavid S. Miller return 0; 1218c1b4a7e6SDavid S. Miller } 1219c1b4a7e6SDavid S. Miller 1220c1b4a7e6SDavid S. Miller /* Try to defer sending, if possible, in order to minimize the amount 1221c1b4a7e6SDavid S. Miller * of TSO splitting we do. View it as a kind of TSO Nagle test. 1222c1b4a7e6SDavid S. Miller * 1223c1b4a7e6SDavid S. Miller * This algorithm is from John Heffner. 1224c1b4a7e6SDavid S. Miller */ 12259e412ba7SIlpo Järvinen static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb) 1226c1b4a7e6SDavid S. Miller { 12279e412ba7SIlpo Järvinen struct tcp_sock *tp = tcp_sk(sk); 12286687e988SArnaldo Carvalho de Melo const struct inet_connection_sock *icsk = inet_csk(sk); 1229c1b4a7e6SDavid S. Miller u32 send_win, cong_win, limit, in_flight; 1230c1b4a7e6SDavid S. Miller 1231c1b4a7e6SDavid S. Miller if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) 1232ae8064acSJohn Heffner goto send_now; 1233c1b4a7e6SDavid S. Miller 12346687e988SArnaldo Carvalho de Melo if (icsk->icsk_ca_state != TCP_CA_Open) 1235ae8064acSJohn Heffner goto send_now; 1236ae8064acSJohn Heffner 1237ae8064acSJohn Heffner /* Defer for less than two clock ticks. */ 1238ae8064acSJohn Heffner if (!tp->tso_deferred && ((jiffies<<1)>>1) - (tp->tso_deferred>>1) > 1) 1239ae8064acSJohn Heffner goto send_now; 1240908a75c1SDavid S. Miller 1241c1b4a7e6SDavid S. Miller in_flight = tcp_packets_in_flight(tp); 1242c1b4a7e6SDavid S. Miller 1243c1b4a7e6SDavid S. Miller BUG_ON(tcp_skb_pcount(skb) <= 1 || 1244c1b4a7e6SDavid S. Miller (tp->snd_cwnd <= in_flight)); 1245c1b4a7e6SDavid S. Miller 1246c1b4a7e6SDavid S. Miller send_win = (tp->snd_una + tp->snd_wnd) - TCP_SKB_CB(skb)->seq; 1247c1b4a7e6SDavid S. Miller 1248c1b4a7e6SDavid S. Miller /* From in_flight test above, we know that cwnd > in_flight. */ 1249c1b4a7e6SDavid S. Miller cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache; 1250c1b4a7e6SDavid S. Miller 1251c1b4a7e6SDavid S. Miller limit = min(send_win, cong_win); 1252c1b4a7e6SDavid S. Miller 1253ba244fe9SDavid S. Miller /* If a full-sized TSO skb can be sent, do it. */ 1254ba244fe9SDavid S. Miller if (limit >= 65536) 1255ae8064acSJohn Heffner goto send_now; 1256ba244fe9SDavid S. Miller 1257c1b4a7e6SDavid S. Miller if (sysctl_tcp_tso_win_divisor) { 1258c1b4a7e6SDavid S. Miller u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache); 1259c1b4a7e6SDavid S. Miller 1260c1b4a7e6SDavid S. Miller /* If at least some fraction of a window is available, 1261c1b4a7e6SDavid S. Miller * just use it. 1262c1b4a7e6SDavid S. Miller */ 1263c1b4a7e6SDavid S. Miller chunk /= sysctl_tcp_tso_win_divisor; 1264c1b4a7e6SDavid S. Miller if (limit >= chunk) 1265ae8064acSJohn Heffner goto send_now; 1266c1b4a7e6SDavid S. Miller } else { 1267c1b4a7e6SDavid S. Miller /* Different approach, try not to defer past a single 1268c1b4a7e6SDavid S. Miller * ACK. Receiver should ACK every other full sized 1269c1b4a7e6SDavid S. Miller * frame, so if we have space for more than 3 frames 1270c1b4a7e6SDavid S. Miller * then send now. 1271c1b4a7e6SDavid S. Miller */ 1272c1b4a7e6SDavid S. Miller if (limit > tcp_max_burst(tp) * tp->mss_cache) 1273ae8064acSJohn Heffner goto send_now; 1274c1b4a7e6SDavid S. Miller } 1275c1b4a7e6SDavid S. Miller 1276c1b4a7e6SDavid S. Miller /* Ok, it looks like it is advisable to defer. */ 1277ae8064acSJohn Heffner tp->tso_deferred = 1 | (jiffies<<1); 1278ae8064acSJohn Heffner 1279c1b4a7e6SDavid S. Miller return 1; 1280ae8064acSJohn Heffner 1281ae8064acSJohn Heffner send_now: 1282ae8064acSJohn Heffner tp->tso_deferred = 0; 1283ae8064acSJohn Heffner return 0; 1284c1b4a7e6SDavid S. Miller } 1285c1b4a7e6SDavid S. Miller 12865d424d5aSJohn Heffner /* Create a new MTU probe if we are ready. 12875d424d5aSJohn Heffner * Returns 0 if we should wait to probe (no cwnd available), 12885d424d5aSJohn Heffner * 1 if a probe was sent, 12895d424d5aSJohn Heffner * -1 otherwise */ 12905d424d5aSJohn Heffner static int tcp_mtu_probe(struct sock *sk) 12915d424d5aSJohn Heffner { 12925d424d5aSJohn Heffner struct tcp_sock *tp = tcp_sk(sk); 12935d424d5aSJohn Heffner struct inet_connection_sock *icsk = inet_csk(sk); 12945d424d5aSJohn Heffner struct sk_buff *skb, *nskb, *next; 12955d424d5aSJohn Heffner int len; 12965d424d5aSJohn Heffner int probe_size; 12975d424d5aSJohn Heffner unsigned int pif; 12985d424d5aSJohn Heffner int copy; 12995d424d5aSJohn Heffner int mss_now; 13005d424d5aSJohn Heffner 13015d424d5aSJohn Heffner /* Not currently probing/verifying, 13025d424d5aSJohn Heffner * not in recovery, 13035d424d5aSJohn Heffner * have enough cwnd, and 13045d424d5aSJohn Heffner * not SACKing (the variable headers throw things off) */ 13055d424d5aSJohn Heffner if (!icsk->icsk_mtup.enabled || 13065d424d5aSJohn Heffner icsk->icsk_mtup.probe_size || 13075d424d5aSJohn Heffner inet_csk(sk)->icsk_ca_state != TCP_CA_Open || 13085d424d5aSJohn Heffner tp->snd_cwnd < 11 || 13095d424d5aSJohn Heffner tp->rx_opt.eff_sacks) 13105d424d5aSJohn Heffner return -1; 13115d424d5aSJohn Heffner 13125d424d5aSJohn Heffner /* Very simple search strategy: just double the MSS. */ 13135d424d5aSJohn Heffner mss_now = tcp_current_mss(sk, 0); 13145d424d5aSJohn Heffner probe_size = 2*tp->mss_cache; 13155d424d5aSJohn Heffner if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) { 13165d424d5aSJohn Heffner /* TODO: set timer for probe_converge_event */ 13175d424d5aSJohn Heffner return -1; 13185d424d5aSJohn Heffner } 13195d424d5aSJohn Heffner 13205d424d5aSJohn Heffner /* Have enough data in the send queue to probe? */ 13215d424d5aSJohn Heffner len = 0; 1322fe067e8aSDavid S. Miller if ((skb = tcp_send_head(sk)) == NULL) 13235d424d5aSJohn Heffner return -1; 13245d424d5aSJohn Heffner while ((len += skb->len) < probe_size && !tcp_skb_is_last(sk, skb)) 1325fe067e8aSDavid S. Miller skb = tcp_write_queue_next(sk, skb); 13265d424d5aSJohn Heffner if (len < probe_size) 13275d424d5aSJohn Heffner return -1; 13285d424d5aSJohn Heffner 13295d424d5aSJohn Heffner /* Receive window check. */ 13305d424d5aSJohn Heffner if (after(TCP_SKB_CB(skb)->seq + probe_size, tp->snd_una + tp->snd_wnd)) { 13315d424d5aSJohn Heffner if (tp->snd_wnd < probe_size) 13325d424d5aSJohn Heffner return -1; 13335d424d5aSJohn Heffner else 13345d424d5aSJohn Heffner return 0; 13355d424d5aSJohn Heffner } 13365d424d5aSJohn Heffner 13375d424d5aSJohn Heffner /* Do we need to wait to drain cwnd? */ 13385d424d5aSJohn Heffner pif = tcp_packets_in_flight(tp); 13395d424d5aSJohn Heffner if (pif + 2 > tp->snd_cwnd) { 13405d424d5aSJohn Heffner /* With no packets in flight, don't stall. */ 13415d424d5aSJohn Heffner if (pif == 0) 13425d424d5aSJohn Heffner return -1; 13435d424d5aSJohn Heffner else 13445d424d5aSJohn Heffner return 0; 13455d424d5aSJohn Heffner } 13465d424d5aSJohn Heffner 13475d424d5aSJohn Heffner /* We're allowed to probe. Build it now. */ 13485d424d5aSJohn Heffner if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL) 13495d424d5aSJohn Heffner return -1; 13505d424d5aSJohn Heffner sk_charge_skb(sk, nskb); 13515d424d5aSJohn Heffner 1352fe067e8aSDavid S. Miller skb = tcp_send_head(sk); 1353fe067e8aSDavid S. Miller tcp_insert_write_queue_before(nskb, skb, sk); 1354fe067e8aSDavid S. Miller tcp_advance_send_head(sk, skb); 13555d424d5aSJohn Heffner 13565d424d5aSJohn Heffner TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq; 13575d424d5aSJohn Heffner TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size; 13585d424d5aSJohn Heffner TCP_SKB_CB(nskb)->flags = TCPCB_FLAG_ACK; 13595d424d5aSJohn Heffner TCP_SKB_CB(nskb)->sacked = 0; 13605d424d5aSJohn Heffner nskb->csum = 0; 136184fa7933SPatrick McHardy nskb->ip_summed = skb->ip_summed; 13625d424d5aSJohn Heffner 13635d424d5aSJohn Heffner len = 0; 13645d424d5aSJohn Heffner while (len < probe_size) { 1365fe067e8aSDavid S. Miller next = tcp_write_queue_next(sk, skb); 13665d424d5aSJohn Heffner 13675d424d5aSJohn Heffner copy = min_t(int, skb->len, probe_size - len); 13685d424d5aSJohn Heffner if (nskb->ip_summed) 13695d424d5aSJohn Heffner skb_copy_bits(skb, 0, skb_put(nskb, copy), copy); 13705d424d5aSJohn Heffner else 13715d424d5aSJohn Heffner nskb->csum = skb_copy_and_csum_bits(skb, 0, 13725d424d5aSJohn Heffner skb_put(nskb, copy), copy, nskb->csum); 13735d424d5aSJohn Heffner 13745d424d5aSJohn Heffner if (skb->len <= copy) { 13755d424d5aSJohn Heffner /* We've eaten all the data from this skb. 13765d424d5aSJohn Heffner * Throw it away. */ 13775d424d5aSJohn Heffner TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags; 1378fe067e8aSDavid S. Miller tcp_unlink_write_queue(skb, sk); 13795d424d5aSJohn Heffner sk_stream_free_skb(sk, skb); 13805d424d5aSJohn Heffner } else { 13815d424d5aSJohn Heffner TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags & 13825d424d5aSJohn Heffner ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH); 13835d424d5aSJohn Heffner if (!skb_shinfo(skb)->nr_frags) { 13845d424d5aSJohn Heffner skb_pull(skb, copy); 138584fa7933SPatrick McHardy if (skb->ip_summed != CHECKSUM_PARTIAL) 13865d424d5aSJohn Heffner skb->csum = csum_partial(skb->data, skb->len, 0); 13875d424d5aSJohn Heffner } else { 13885d424d5aSJohn Heffner __pskb_trim_head(skb, copy); 13895d424d5aSJohn Heffner tcp_set_skb_tso_segs(sk, skb, mss_now); 13905d424d5aSJohn Heffner } 13915d424d5aSJohn Heffner TCP_SKB_CB(skb)->seq += copy; 13925d424d5aSJohn Heffner } 13935d424d5aSJohn Heffner 13945d424d5aSJohn Heffner len += copy; 13955d424d5aSJohn Heffner skb = next; 13965d424d5aSJohn Heffner } 13975d424d5aSJohn Heffner tcp_init_tso_segs(sk, nskb, nskb->len); 13985d424d5aSJohn Heffner 13995d424d5aSJohn Heffner /* We're ready to send. If this fails, the probe will 14005d424d5aSJohn Heffner * be resegmented into mss-sized pieces by tcp_write_xmit(). */ 14015d424d5aSJohn Heffner TCP_SKB_CB(nskb)->when = tcp_time_stamp; 14025d424d5aSJohn Heffner if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) { 14035d424d5aSJohn Heffner /* Decrement cwnd here because we are sending 14045d424d5aSJohn Heffner * effectively two packets. */ 14055d424d5aSJohn Heffner tp->snd_cwnd--; 14069e412ba7SIlpo Järvinen update_send_head(sk, nskb); 14075d424d5aSJohn Heffner 14085d424d5aSJohn Heffner icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len); 14090e7b1368SJohn Heffner tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq; 14100e7b1368SJohn Heffner tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq; 14115d424d5aSJohn Heffner 14125d424d5aSJohn Heffner return 1; 14135d424d5aSJohn Heffner } 14145d424d5aSJohn Heffner 14155d424d5aSJohn Heffner return -1; 14165d424d5aSJohn Heffner } 14175d424d5aSJohn Heffner 14185d424d5aSJohn Heffner 14191da177e4SLinus Torvalds /* This routine writes packets to the network. It advances the 14201da177e4SLinus Torvalds * send_head. This happens as incoming acks open up the remote 14211da177e4SLinus Torvalds * window for us. 14221da177e4SLinus Torvalds * 14231da177e4SLinus Torvalds * Returns 1, if no segments are in flight and we have queued segments, but 14241da177e4SLinus Torvalds * cannot send anything now because of SWS or another problem. 14251da177e4SLinus Torvalds */ 1426a2e2a59cSDavid S. Miller static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle) 14271da177e4SLinus Torvalds { 14281da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 142992df7b51SDavid S. Miller struct sk_buff *skb; 1430c1b4a7e6SDavid S. Miller unsigned int tso_segs, sent_pkts; 1431c1b4a7e6SDavid S. Miller int cwnd_quota; 14325d424d5aSJohn Heffner int result; 14331da177e4SLinus Torvalds 14341da177e4SLinus Torvalds /* If we are closed, the bytes will have to remain here. 14351da177e4SLinus Torvalds * In time closedown will finish, we empty the write queue and all 14361da177e4SLinus Torvalds * will be happy. 14371da177e4SLinus Torvalds */ 143892df7b51SDavid S. Miller if (unlikely(sk->sk_state == TCP_CLOSE)) 143992df7b51SDavid S. Miller return 0; 144092df7b51SDavid S. Miller 1441c1b4a7e6SDavid S. Miller sent_pkts = 0; 14425d424d5aSJohn Heffner 14435d424d5aSJohn Heffner /* Do MTU probing. */ 14445d424d5aSJohn Heffner if ((result = tcp_mtu_probe(sk)) == 0) { 14455d424d5aSJohn Heffner return 0; 14465d424d5aSJohn Heffner } else if (result > 0) { 14475d424d5aSJohn Heffner sent_pkts = 1; 14485d424d5aSJohn Heffner } 14495d424d5aSJohn Heffner 1450fe067e8aSDavid S. Miller while ((skb = tcp_send_head(sk))) { 1451c8ac3774SHerbert Xu unsigned int limit; 1452c8ac3774SHerbert Xu 1453b68e9f85SHerbert Xu tso_segs = tcp_init_tso_segs(sk, skb, mss_now); 1454c1b4a7e6SDavid S. Miller BUG_ON(!tso_segs); 1455c1b4a7e6SDavid S. Miller 1456b68e9f85SHerbert Xu cwnd_quota = tcp_cwnd_test(tp, skb); 1457b68e9f85SHerbert Xu if (!cwnd_quota) 1458b68e9f85SHerbert Xu break; 1459b68e9f85SHerbert Xu 1460b68e9f85SHerbert Xu if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) 1461b68e9f85SHerbert Xu break; 1462b68e9f85SHerbert Xu 1463c1b4a7e6SDavid S. Miller if (tso_segs == 1) { 1464aa93466bSDavid S. Miller if (unlikely(!tcp_nagle_test(tp, skb, mss_now, 1465aa93466bSDavid S. Miller (tcp_skb_is_last(sk, skb) ? 1466aa93466bSDavid S. Miller nonagle : TCP_NAGLE_PUSH)))) 1467aa93466bSDavid S. Miller break; 1468c1b4a7e6SDavid S. Miller } else { 14699e412ba7SIlpo Järvinen if (tcp_tso_should_defer(sk, skb)) 1470aa93466bSDavid S. Miller break; 1471c1b4a7e6SDavid S. Miller } 1472aa93466bSDavid S. Miller 1473c8ac3774SHerbert Xu limit = mss_now; 1474c1b4a7e6SDavid S. Miller if (tso_segs > 1) { 1475c8ac3774SHerbert Xu limit = tcp_window_allows(tp, skb, 1476c1b4a7e6SDavid S. Miller mss_now, cwnd_quota); 1477c1b4a7e6SDavid S. Miller 1478c1b4a7e6SDavid S. Miller if (skb->len < limit) { 1479c1b4a7e6SDavid S. Miller unsigned int trim = skb->len % mss_now; 1480c1b4a7e6SDavid S. Miller 1481c1b4a7e6SDavid S. Miller if (trim) 1482c1b4a7e6SDavid S. Miller limit = skb->len - trim; 1483c1b4a7e6SDavid S. Miller } 1484c1b4a7e6SDavid S. Miller } 1485c8ac3774SHerbert Xu 1486c8ac3774SHerbert Xu if (skb->len > limit && 1487c8ac3774SHerbert Xu unlikely(tso_fragment(sk, skb, limit, mss_now))) 14881da177e4SLinus Torvalds break; 14891da177e4SLinus Torvalds 14901da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 1491c1b4a7e6SDavid S. Miller 1492dfb4b9dcSDavid S. Miller if (unlikely(tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC))) 14931da177e4SLinus Torvalds break; 14941da177e4SLinus Torvalds 14951da177e4SLinus Torvalds /* Advance the send_head. This one is sent out. 14961da177e4SLinus Torvalds * This call will increment packets_out. 14971da177e4SLinus Torvalds */ 14989e412ba7SIlpo Järvinen update_send_head(sk, skb); 14991da177e4SLinus Torvalds 15001da177e4SLinus Torvalds tcp_minshall_update(tp, mss_now, skb); 1501aa93466bSDavid S. Miller sent_pkts++; 15021da177e4SLinus Torvalds } 15031da177e4SLinus Torvalds 1504aa93466bSDavid S. Miller if (likely(sent_pkts)) { 15059e412ba7SIlpo Järvinen tcp_cwnd_validate(sk); 15061da177e4SLinus Torvalds return 0; 15071da177e4SLinus Torvalds } 1508fe067e8aSDavid S. Miller return !tp->packets_out && tcp_send_head(sk); 15091da177e4SLinus Torvalds } 15101da177e4SLinus Torvalds 1511a762a980SDavid S. Miller /* Push out any pending frames which were held back due to 1512a762a980SDavid S. Miller * TCP_CORK or attempt at coalescing tiny packets. 1513a762a980SDavid S. Miller * The socket must be locked by the caller. 1514a762a980SDavid S. Miller */ 15159e412ba7SIlpo Järvinen void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss, 15169e412ba7SIlpo Järvinen int nonagle) 1517a762a980SDavid S. Miller { 1518fe067e8aSDavid S. Miller struct sk_buff *skb = tcp_send_head(sk); 1519a762a980SDavid S. Miller 1520a762a980SDavid S. Miller if (skb) { 152155c97f3eSDavid S. Miller if (tcp_write_xmit(sk, cur_mss, nonagle)) 15229e412ba7SIlpo Järvinen tcp_check_probe_timer(sk); 1523a762a980SDavid S. Miller } 1524a762a980SDavid S. Miller } 1525a762a980SDavid S. Miller 1526c1b4a7e6SDavid S. Miller /* Send _single_ skb sitting at the send head. This function requires 1527c1b4a7e6SDavid S. Miller * true push pending frames to setup probe timer etc. 1528c1b4a7e6SDavid S. Miller */ 1529c1b4a7e6SDavid S. Miller void tcp_push_one(struct sock *sk, unsigned int mss_now) 1530c1b4a7e6SDavid S. Miller { 1531c1b4a7e6SDavid S. Miller struct tcp_sock *tp = tcp_sk(sk); 1532fe067e8aSDavid S. Miller struct sk_buff *skb = tcp_send_head(sk); 1533c1b4a7e6SDavid S. Miller unsigned int tso_segs, cwnd_quota; 1534c1b4a7e6SDavid S. Miller 1535c1b4a7e6SDavid S. Miller BUG_ON(!skb || skb->len < mss_now); 1536c1b4a7e6SDavid S. Miller 1537846998aeSDavid S. Miller tso_segs = tcp_init_tso_segs(sk, skb, mss_now); 1538c1b4a7e6SDavid S. Miller cwnd_quota = tcp_snd_test(sk, skb, mss_now, TCP_NAGLE_PUSH); 1539c1b4a7e6SDavid S. Miller 1540c1b4a7e6SDavid S. Miller if (likely(cwnd_quota)) { 1541c8ac3774SHerbert Xu unsigned int limit; 1542c8ac3774SHerbert Xu 1543c1b4a7e6SDavid S. Miller BUG_ON(!tso_segs); 1544c1b4a7e6SDavid S. Miller 1545c8ac3774SHerbert Xu limit = mss_now; 1546c1b4a7e6SDavid S. Miller if (tso_segs > 1) { 1547c8ac3774SHerbert Xu limit = tcp_window_allows(tp, skb, 1548c1b4a7e6SDavid S. Miller mss_now, cwnd_quota); 1549c1b4a7e6SDavid S. Miller 1550c1b4a7e6SDavid S. Miller if (skb->len < limit) { 1551c1b4a7e6SDavid S. Miller unsigned int trim = skb->len % mss_now; 1552c1b4a7e6SDavid S. Miller 1553c1b4a7e6SDavid S. Miller if (trim) 1554c1b4a7e6SDavid S. Miller limit = skb->len - trim; 1555c1b4a7e6SDavid S. Miller } 1556c1b4a7e6SDavid S. Miller } 1557c8ac3774SHerbert Xu 1558c8ac3774SHerbert Xu if (skb->len > limit && 1559c8ac3774SHerbert Xu unlikely(tso_fragment(sk, skb, limit, mss_now))) 1560c1b4a7e6SDavid S. Miller return; 1561c1b4a7e6SDavid S. Miller 1562c1b4a7e6SDavid S. Miller /* Send it out now. */ 1563c1b4a7e6SDavid S. Miller TCP_SKB_CB(skb)->when = tcp_time_stamp; 1564c1b4a7e6SDavid S. Miller 1565dfb4b9dcSDavid S. Miller if (likely(!tcp_transmit_skb(sk, skb, 1, sk->sk_allocation))) { 15669e412ba7SIlpo Järvinen update_send_head(sk, skb); 15679e412ba7SIlpo Järvinen tcp_cwnd_validate(sk); 1568c1b4a7e6SDavid S. Miller return; 1569c1b4a7e6SDavid S. Miller } 1570c1b4a7e6SDavid S. Miller } 1571c1b4a7e6SDavid S. Miller } 1572c1b4a7e6SDavid S. Miller 15731da177e4SLinus Torvalds /* This function returns the amount that we can raise the 15741da177e4SLinus Torvalds * usable window based on the following constraints 15751da177e4SLinus Torvalds * 15761da177e4SLinus Torvalds * 1. The window can never be shrunk once it is offered (RFC 793) 15771da177e4SLinus Torvalds * 2. We limit memory per socket 15781da177e4SLinus Torvalds * 15791da177e4SLinus Torvalds * RFC 1122: 15801da177e4SLinus Torvalds * "the suggested [SWS] avoidance algorithm for the receiver is to keep 15811da177e4SLinus Torvalds * RECV.NEXT + RCV.WIN fixed until: 15821da177e4SLinus Torvalds * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)" 15831da177e4SLinus Torvalds * 15841da177e4SLinus Torvalds * i.e. don't raise the right edge of the window until you can raise 15851da177e4SLinus Torvalds * it at least MSS bytes. 15861da177e4SLinus Torvalds * 15871da177e4SLinus Torvalds * Unfortunately, the recommended algorithm breaks header prediction, 15881da177e4SLinus Torvalds * since header prediction assumes th->window stays fixed. 15891da177e4SLinus Torvalds * 15901da177e4SLinus Torvalds * Strictly speaking, keeping th->window fixed violates the receiver 15911da177e4SLinus Torvalds * side SWS prevention criteria. The problem is that under this rule 15921da177e4SLinus Torvalds * a stream of single byte packets will cause the right side of the 15931da177e4SLinus Torvalds * window to always advance by a single byte. 15941da177e4SLinus Torvalds * 15951da177e4SLinus Torvalds * Of course, if the sender implements sender side SWS prevention 15961da177e4SLinus Torvalds * then this will not be a problem. 15971da177e4SLinus Torvalds * 15981da177e4SLinus Torvalds * BSD seems to make the following compromise: 15991da177e4SLinus Torvalds * 16001da177e4SLinus Torvalds * If the free space is less than the 1/4 of the maximum 16011da177e4SLinus Torvalds * space available and the free space is less than 1/2 mss, 16021da177e4SLinus Torvalds * then set the window to 0. 16031da177e4SLinus Torvalds * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ] 16041da177e4SLinus Torvalds * Otherwise, just prevent the window from shrinking 16051da177e4SLinus Torvalds * and from being larger than the largest representable value. 16061da177e4SLinus Torvalds * 16071da177e4SLinus Torvalds * This prevents incremental opening of the window in the regime 16081da177e4SLinus Torvalds * where TCP is limited by the speed of the reader side taking 16091da177e4SLinus Torvalds * data out of the TCP receive queue. It does nothing about 16101da177e4SLinus Torvalds * those cases where the window is constrained on the sender side 16111da177e4SLinus Torvalds * because the pipeline is full. 16121da177e4SLinus Torvalds * 16131da177e4SLinus Torvalds * BSD also seems to "accidentally" limit itself to windows that are a 16141da177e4SLinus Torvalds * multiple of MSS, at least until the free space gets quite small. 16151da177e4SLinus Torvalds * This would appear to be a side effect of the mbuf implementation. 16161da177e4SLinus Torvalds * Combining these two algorithms results in the observed behavior 16171da177e4SLinus Torvalds * of having a fixed window size at almost all times. 16181da177e4SLinus Torvalds * 16191da177e4SLinus Torvalds * Below we obtain similar behavior by forcing the offered window to 16201da177e4SLinus Torvalds * a multiple of the mss when it is feasible to do so. 16211da177e4SLinus Torvalds * 16221da177e4SLinus Torvalds * Note, we don't "adjust" for TIMESTAMP or SACK option bytes. 16231da177e4SLinus Torvalds * Regular options like TIMESTAMP are taken into account. 16241da177e4SLinus Torvalds */ 16251da177e4SLinus Torvalds u32 __tcp_select_window(struct sock *sk) 16261da177e4SLinus Torvalds { 1627463c84b9SArnaldo Carvalho de Melo struct inet_connection_sock *icsk = inet_csk(sk); 16281da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 1629caa20d9aSStephen Hemminger /* MSS for the peer's data. Previous versions used mss_clamp 16301da177e4SLinus Torvalds * here. I don't know if the value based on our guesses 16311da177e4SLinus Torvalds * of peer's MSS is better for the performance. It's more correct 16321da177e4SLinus Torvalds * but may be worse for the performance because of rcv_mss 16331da177e4SLinus Torvalds * fluctuations. --SAW 1998/11/1 16341da177e4SLinus Torvalds */ 1635463c84b9SArnaldo Carvalho de Melo int mss = icsk->icsk_ack.rcv_mss; 16361da177e4SLinus Torvalds int free_space = tcp_space(sk); 16371da177e4SLinus Torvalds int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk)); 16381da177e4SLinus Torvalds int window; 16391da177e4SLinus Torvalds 16401da177e4SLinus Torvalds if (mss > full_space) 16411da177e4SLinus Torvalds mss = full_space; 16421da177e4SLinus Torvalds 16431da177e4SLinus Torvalds if (free_space < full_space/2) { 1644463c84b9SArnaldo Carvalho de Melo icsk->icsk_ack.quick = 0; 16451da177e4SLinus Torvalds 16461da177e4SLinus Torvalds if (tcp_memory_pressure) 16471da177e4SLinus Torvalds tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U*tp->advmss); 16481da177e4SLinus Torvalds 16491da177e4SLinus Torvalds if (free_space < mss) 16501da177e4SLinus Torvalds return 0; 16511da177e4SLinus Torvalds } 16521da177e4SLinus Torvalds 16531da177e4SLinus Torvalds if (free_space > tp->rcv_ssthresh) 16541da177e4SLinus Torvalds free_space = tp->rcv_ssthresh; 16551da177e4SLinus Torvalds 16561da177e4SLinus Torvalds /* Don't do rounding if we are using window scaling, since the 16571da177e4SLinus Torvalds * scaled window will not line up with the MSS boundary anyway. 16581da177e4SLinus Torvalds */ 16591da177e4SLinus Torvalds window = tp->rcv_wnd; 16601da177e4SLinus Torvalds if (tp->rx_opt.rcv_wscale) { 16611da177e4SLinus Torvalds window = free_space; 16621da177e4SLinus Torvalds 16631da177e4SLinus Torvalds /* Advertise enough space so that it won't get scaled away. 16641da177e4SLinus Torvalds * Import case: prevent zero window announcement if 16651da177e4SLinus Torvalds * 1<<rcv_wscale > mss. 16661da177e4SLinus Torvalds */ 16671da177e4SLinus Torvalds if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window) 16681da177e4SLinus Torvalds window = (((window >> tp->rx_opt.rcv_wscale) + 1) 16691da177e4SLinus Torvalds << tp->rx_opt.rcv_wscale); 16701da177e4SLinus Torvalds } else { 16711da177e4SLinus Torvalds /* Get the largest window that is a nice multiple of mss. 16721da177e4SLinus Torvalds * Window clamp already applied above. 16731da177e4SLinus Torvalds * If our current window offering is within 1 mss of the 16741da177e4SLinus Torvalds * free space we just keep it. This prevents the divide 16751da177e4SLinus Torvalds * and multiply from happening most of the time. 16761da177e4SLinus Torvalds * We also don't do any window rounding when the free space 16771da177e4SLinus Torvalds * is too small. 16781da177e4SLinus Torvalds */ 16791da177e4SLinus Torvalds if (window <= free_space - mss || window > free_space) 16801da177e4SLinus Torvalds window = (free_space/mss)*mss; 168184565070SJohn Heffner else if (mss == full_space && 168284565070SJohn Heffner free_space > window + full_space/2) 168384565070SJohn Heffner window = free_space; 16841da177e4SLinus Torvalds } 16851da177e4SLinus Torvalds 16861da177e4SLinus Torvalds return window; 16871da177e4SLinus Torvalds } 16881da177e4SLinus Torvalds 16891da177e4SLinus Torvalds /* Attempt to collapse two adjacent SKB's during retransmission. */ 16901da177e4SLinus Torvalds static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int mss_now) 16911da177e4SLinus Torvalds { 16921da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 1693fe067e8aSDavid S. Miller struct sk_buff *next_skb = tcp_write_queue_next(sk, skb); 16941da177e4SLinus Torvalds 16951da177e4SLinus Torvalds /* The first test we must make is that neither of these two 16961da177e4SLinus Torvalds * SKB's are still referenced by someone else. 16971da177e4SLinus Torvalds */ 16981da177e4SLinus Torvalds if (!skb_cloned(skb) && !skb_cloned(next_skb)) { 16991da177e4SLinus Torvalds int skb_size = skb->len, next_skb_size = next_skb->len; 17001da177e4SLinus Torvalds u16 flags = TCP_SKB_CB(skb)->flags; 17011da177e4SLinus Torvalds 17021da177e4SLinus Torvalds /* Also punt if next skb has been SACK'd. */ 17031da177e4SLinus Torvalds if (TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_ACKED) 17041da177e4SLinus Torvalds return; 17051da177e4SLinus Torvalds 17061da177e4SLinus Torvalds /* Next skb is out of window. */ 17071da177e4SLinus Torvalds if (after(TCP_SKB_CB(next_skb)->end_seq, tp->snd_una+tp->snd_wnd)) 17081da177e4SLinus Torvalds return; 17091da177e4SLinus Torvalds 17101da177e4SLinus Torvalds /* Punt if not enough space exists in the first SKB for 17111da177e4SLinus Torvalds * the data in the second, or the total combined payload 17121da177e4SLinus Torvalds * would exceed the MSS. 17131da177e4SLinus Torvalds */ 17141da177e4SLinus Torvalds if ((next_skb_size > skb_tailroom(skb)) || 17151da177e4SLinus Torvalds ((skb_size + next_skb_size) > mss_now)) 17161da177e4SLinus Torvalds return; 17171da177e4SLinus Torvalds 17181da177e4SLinus Torvalds BUG_ON(tcp_skb_pcount(skb) != 1 || 17191da177e4SLinus Torvalds tcp_skb_pcount(next_skb) != 1); 17201da177e4SLinus Torvalds 1721*a6963a6bSIlpo Järvinen if (WARN_ON(tp->sacked_out && 1722*a6963a6bSIlpo Järvinen (TCP_SKB_CB(next_skb)->seq == tp->highest_sack))) 1723*a6963a6bSIlpo Järvinen return; 1724*a6963a6bSIlpo Järvinen 17251da177e4SLinus Torvalds /* Ok. We will be able to collapse the packet. */ 1726fe067e8aSDavid S. Miller tcp_unlink_write_queue(next_skb, sk); 17271da177e4SLinus Torvalds 17281a4e2d09SArnaldo Carvalho de Melo skb_copy_from_linear_data(next_skb, 17291a4e2d09SArnaldo Carvalho de Melo skb_put(skb, next_skb_size), 17301a4e2d09SArnaldo Carvalho de Melo next_skb_size); 17311da177e4SLinus Torvalds 173252d570aaSJarek Poplawski if (next_skb->ip_summed == CHECKSUM_PARTIAL) 173352d570aaSJarek Poplawski skb->ip_summed = CHECKSUM_PARTIAL; 17341da177e4SLinus Torvalds 173584fa7933SPatrick McHardy if (skb->ip_summed != CHECKSUM_PARTIAL) 17361da177e4SLinus Torvalds skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size); 17371da177e4SLinus Torvalds 17381da177e4SLinus Torvalds /* Update sequence range on original skb. */ 17391da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq; 17401da177e4SLinus Torvalds 17411da177e4SLinus Torvalds /* Merge over control information. */ 17421da177e4SLinus Torvalds flags |= TCP_SKB_CB(next_skb)->flags; /* This moves PSH/FIN etc. over */ 17431da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags = flags; 17441da177e4SLinus Torvalds 17451da177e4SLinus Torvalds /* All done, get rid of second SKB and account for it so 17461da177e4SLinus Torvalds * packet counting does not break. 17471da177e4SLinus Torvalds */ 17481da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked&(TCPCB_EVER_RETRANS|TCPCB_AT_TAIL); 17491da177e4SLinus Torvalds if (TCP_SKB_CB(next_skb)->sacked&TCPCB_SACKED_RETRANS) 17501da177e4SLinus Torvalds tp->retrans_out -= tcp_skb_pcount(next_skb); 1751b5860bbaSIlpo Järvinen if (TCP_SKB_CB(next_skb)->sacked&TCPCB_LOST) 17521da177e4SLinus Torvalds tp->lost_out -= tcp_skb_pcount(next_skb); 17531da177e4SLinus Torvalds /* Reno case is special. Sigh... */ 1754e60402d0SIlpo Järvinen if (tcp_is_reno(tp) && tp->sacked_out) 17551da177e4SLinus Torvalds tcp_dec_pcount_approx(&tp->sacked_out, next_skb); 17561da177e4SLinus Torvalds 175791fed7a1SIlpo Järvinen tcp_adjust_fackets_out(tp, skb, tcp_skb_pcount(next_skb)); 1758e9144bd8SIlpo Järvinen tp->packets_out -= tcp_skb_pcount(next_skb); 1759b7689205SIlpo Järvinen 1760b7689205SIlpo Järvinen /* changed transmit queue under us so clear hints */ 1761b7689205SIlpo Järvinen tcp_clear_retrans_hints_partial(tp); 1762b7689205SIlpo Järvinen /* manually tune sacktag skb hint */ 1763b7689205SIlpo Järvinen if (tp->fastpath_skb_hint == next_skb) 1764b7689205SIlpo Järvinen tp->fastpath_skb_hint = skb; 1765b7689205SIlpo Järvinen 17661da177e4SLinus Torvalds sk_stream_free_skb(sk, next_skb); 17671da177e4SLinus Torvalds } 17681da177e4SLinus Torvalds } 17691da177e4SLinus Torvalds 17701da177e4SLinus Torvalds /* Do a simple retransmit without using the backoff mechanisms in 17711da177e4SLinus Torvalds * tcp_timer. This is used for path mtu discovery. 17721da177e4SLinus Torvalds * The socket is already locked here. 17731da177e4SLinus Torvalds */ 17741da177e4SLinus Torvalds void tcp_simple_retransmit(struct sock *sk) 17751da177e4SLinus Torvalds { 17766687e988SArnaldo Carvalho de Melo const struct inet_connection_sock *icsk = inet_csk(sk); 17771da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 17781da177e4SLinus Torvalds struct sk_buff *skb; 17791da177e4SLinus Torvalds unsigned int mss = tcp_current_mss(sk, 0); 17801da177e4SLinus Torvalds int lost = 0; 17811da177e4SLinus Torvalds 1782fe067e8aSDavid S. Miller tcp_for_write_queue(skb, sk) { 1783fe067e8aSDavid S. Miller if (skb == tcp_send_head(sk)) 1784fe067e8aSDavid S. Miller break; 17851da177e4SLinus Torvalds if (skb->len > mss && 17861da177e4SLinus Torvalds !(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) { 17871da177e4SLinus Torvalds if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) { 17881da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 17891da177e4SLinus Torvalds tp->retrans_out -= tcp_skb_pcount(skb); 17901da177e4SLinus Torvalds } 17911da177e4SLinus Torvalds if (!(TCP_SKB_CB(skb)->sacked&TCPCB_LOST)) { 17921da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 17931da177e4SLinus Torvalds tp->lost_out += tcp_skb_pcount(skb); 17941da177e4SLinus Torvalds lost = 1; 17951da177e4SLinus Torvalds } 17961da177e4SLinus Torvalds } 17971da177e4SLinus Torvalds } 17981da177e4SLinus Torvalds 17995af4ec23SIlpo Järvinen tcp_clear_all_retrans_hints(tp); 18006a438bbeSStephen Hemminger 18011da177e4SLinus Torvalds if (!lost) 18021da177e4SLinus Torvalds return; 18031da177e4SLinus Torvalds 1804005903bcSIlpo Järvinen tcp_verify_left_out(tp); 18051da177e4SLinus Torvalds 18061da177e4SLinus Torvalds /* Don't muck with the congestion window here. 18071da177e4SLinus Torvalds * Reason is that we do not increase amount of _data_ 18081da177e4SLinus Torvalds * in network, but units changed and effective 18091da177e4SLinus Torvalds * cwnd/ssthresh really reduced now. 18101da177e4SLinus Torvalds */ 18116687e988SArnaldo Carvalho de Melo if (icsk->icsk_ca_state != TCP_CA_Loss) { 18121da177e4SLinus Torvalds tp->high_seq = tp->snd_nxt; 18136687e988SArnaldo Carvalho de Melo tp->snd_ssthresh = tcp_current_ssthresh(sk); 18141da177e4SLinus Torvalds tp->prior_ssthresh = 0; 18151da177e4SLinus Torvalds tp->undo_marker = 0; 18166687e988SArnaldo Carvalho de Melo tcp_set_ca_state(sk, TCP_CA_Loss); 18171da177e4SLinus Torvalds } 18181da177e4SLinus Torvalds tcp_xmit_retransmit_queue(sk); 18191da177e4SLinus Torvalds } 18201da177e4SLinus Torvalds 18211da177e4SLinus Torvalds /* This retransmits one SKB. Policy decisions and retransmit queue 18221da177e4SLinus Torvalds * state updates are done by the caller. Returns non-zero if an 18231da177e4SLinus Torvalds * error occurred which prevented the send. 18241da177e4SLinus Torvalds */ 18251da177e4SLinus Torvalds int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) 18261da177e4SLinus Torvalds { 18271da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 18285d424d5aSJohn Heffner struct inet_connection_sock *icsk = inet_csk(sk); 18291da177e4SLinus Torvalds unsigned int cur_mss = tcp_current_mss(sk, 0); 18301da177e4SLinus Torvalds int err; 18311da177e4SLinus Torvalds 18325d424d5aSJohn Heffner /* Inconslusive MTU probe */ 18335d424d5aSJohn Heffner if (icsk->icsk_mtup.probe_size) { 18345d424d5aSJohn Heffner icsk->icsk_mtup.probe_size = 0; 18355d424d5aSJohn Heffner } 18365d424d5aSJohn Heffner 18371da177e4SLinus Torvalds /* Do not sent more than we queued. 1/4 is reserved for possible 1838caa20d9aSStephen Hemminger * copying overhead: fragmentation, tunneling, mangling etc. 18391da177e4SLinus Torvalds */ 18401da177e4SLinus Torvalds if (atomic_read(&sk->sk_wmem_alloc) > 18411da177e4SLinus Torvalds min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf)) 18421da177e4SLinus Torvalds return -EAGAIN; 18431da177e4SLinus Torvalds 18441da177e4SLinus Torvalds if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) { 18451da177e4SLinus Torvalds if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 18461da177e4SLinus Torvalds BUG(); 18471da177e4SLinus Torvalds if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) 18481da177e4SLinus Torvalds return -ENOMEM; 18491da177e4SLinus Torvalds } 18501da177e4SLinus Torvalds 18511da177e4SLinus Torvalds /* If receiver has shrunk his window, and skb is out of 18521da177e4SLinus Torvalds * new window, do not retransmit it. The exception is the 18531da177e4SLinus Torvalds * case, when window is shrunk to zero. In this case 18541da177e4SLinus Torvalds * our retransmit serves as a zero window probe. 18551da177e4SLinus Torvalds */ 18561da177e4SLinus Torvalds if (!before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd) 18571da177e4SLinus Torvalds && TCP_SKB_CB(skb)->seq != tp->snd_una) 18581da177e4SLinus Torvalds return -EAGAIN; 18591da177e4SLinus Torvalds 18601da177e4SLinus Torvalds if (skb->len > cur_mss) { 1861846998aeSDavid S. Miller if (tcp_fragment(sk, skb, cur_mss, cur_mss)) 18621da177e4SLinus Torvalds return -ENOMEM; /* We'll try again later. */ 18631da177e4SLinus Torvalds } 18641da177e4SLinus Torvalds 18651da177e4SLinus Torvalds /* Collapse two adjacent packets if worthwhile and we can. */ 18661da177e4SLinus Torvalds if (!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) && 18671da177e4SLinus Torvalds (skb->len < (cur_mss >> 1)) && 1868fe067e8aSDavid S. Miller (tcp_write_queue_next(sk, skb) != tcp_send_head(sk)) && 1869fe067e8aSDavid S. Miller (!tcp_skb_is_last(sk, skb)) && 1870fe067e8aSDavid S. Miller (skb_shinfo(skb)->nr_frags == 0 && skb_shinfo(tcp_write_queue_next(sk, skb))->nr_frags == 0) && 1871fe067e8aSDavid S. Miller (tcp_skb_pcount(skb) == 1 && tcp_skb_pcount(tcp_write_queue_next(sk, skb)) == 1) && 18721da177e4SLinus Torvalds (sysctl_tcp_retrans_collapse != 0)) 18731da177e4SLinus Torvalds tcp_retrans_try_collapse(sk, skb, cur_mss); 18741da177e4SLinus Torvalds 18758292a17aSArnaldo Carvalho de Melo if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk)) 18761da177e4SLinus Torvalds return -EHOSTUNREACH; /* Routing failure or similar. */ 18771da177e4SLinus Torvalds 18781da177e4SLinus Torvalds /* Some Solaris stacks overoptimize and ignore the FIN on a 18791da177e4SLinus Torvalds * retransmit when old data is attached. So strip it off 18801da177e4SLinus Torvalds * since it is cheap to do so and saves bytes on the network. 18811da177e4SLinus Torvalds */ 18821da177e4SLinus Torvalds if (skb->len > 0 && 18831da177e4SLinus Torvalds (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) && 18841da177e4SLinus Torvalds tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) { 18851da177e4SLinus Torvalds if (!pskb_trim(skb, 0)) { 18861da177e4SLinus Torvalds TCP_SKB_CB(skb)->seq = TCP_SKB_CB(skb)->end_seq - 1; 18877967168cSHerbert Xu skb_shinfo(skb)->gso_segs = 1; 18887967168cSHerbert Xu skb_shinfo(skb)->gso_size = 0; 18897967168cSHerbert Xu skb_shinfo(skb)->gso_type = 0; 18901da177e4SLinus Torvalds skb->ip_summed = CHECKSUM_NONE; 18911da177e4SLinus Torvalds skb->csum = 0; 18921da177e4SLinus Torvalds } 18931da177e4SLinus Torvalds } 18941da177e4SLinus Torvalds 18951da177e4SLinus Torvalds /* Make a copy, if the first transmission SKB clone we made 18961da177e4SLinus Torvalds * is still in somebody's hands, else make a clone. 18971da177e4SLinus Torvalds */ 18981da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 18991da177e4SLinus Torvalds 1900dfb4b9dcSDavid S. Miller err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 19011da177e4SLinus Torvalds 19021da177e4SLinus Torvalds if (err == 0) { 19031da177e4SLinus Torvalds /* Update global TCP statistics. */ 19041da177e4SLinus Torvalds TCP_INC_STATS(TCP_MIB_RETRANSSEGS); 19051da177e4SLinus Torvalds 19061da177e4SLinus Torvalds tp->total_retrans++; 19071da177e4SLinus Torvalds 19081da177e4SLinus Torvalds #if FASTRETRANS_DEBUG > 0 19091da177e4SLinus Torvalds if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) { 19101da177e4SLinus Torvalds if (net_ratelimit()) 19111da177e4SLinus Torvalds printk(KERN_DEBUG "retrans_out leaked.\n"); 19121da177e4SLinus Torvalds } 19131da177e4SLinus Torvalds #endif 19141da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS; 19151da177e4SLinus Torvalds tp->retrans_out += tcp_skb_pcount(skb); 19161da177e4SLinus Torvalds 19171da177e4SLinus Torvalds /* Save stamp of the first retransmit. */ 19181da177e4SLinus Torvalds if (!tp->retrans_stamp) 19191da177e4SLinus Torvalds tp->retrans_stamp = TCP_SKB_CB(skb)->when; 19201da177e4SLinus Torvalds 19211da177e4SLinus Torvalds tp->undo_retrans++; 19221da177e4SLinus Torvalds 19231da177e4SLinus Torvalds /* snd_nxt is stored to detect loss of retransmitted segment, 19241da177e4SLinus Torvalds * see tcp_input.c tcp_sacktag_write_queue(). 19251da177e4SLinus Torvalds */ 19261da177e4SLinus Torvalds TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt; 19271da177e4SLinus Torvalds } 19281da177e4SLinus Torvalds return err; 19291da177e4SLinus Torvalds } 19301da177e4SLinus Torvalds 19311da177e4SLinus Torvalds /* This gets called after a retransmit timeout, and the initially 19321da177e4SLinus Torvalds * retransmitted data is acknowledged. It tries to continue 19331da177e4SLinus Torvalds * resending the rest of the retransmit queue, until either 19341da177e4SLinus Torvalds * we've sent it all or the congestion window limit is reached. 19351da177e4SLinus Torvalds * If doing SACK, the first ACK which comes back for a timeout 19361da177e4SLinus Torvalds * based retransmit packet might feed us FACK information again. 19371da177e4SLinus Torvalds * If so, we use it to avoid unnecessarily retransmissions. 19381da177e4SLinus Torvalds */ 19391da177e4SLinus Torvalds void tcp_xmit_retransmit_queue(struct sock *sk) 19401da177e4SLinus Torvalds { 19416687e988SArnaldo Carvalho de Melo const struct inet_connection_sock *icsk = inet_csk(sk); 19421da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 19431da177e4SLinus Torvalds struct sk_buff *skb; 19446a438bbeSStephen Hemminger int packet_cnt; 19456a438bbeSStephen Hemminger 19466a438bbeSStephen Hemminger if (tp->retransmit_skb_hint) { 19476a438bbeSStephen Hemminger skb = tp->retransmit_skb_hint; 19486a438bbeSStephen Hemminger packet_cnt = tp->retransmit_cnt_hint; 19496a438bbeSStephen Hemminger }else{ 1950fe067e8aSDavid S. Miller skb = tcp_write_queue_head(sk); 19516a438bbeSStephen Hemminger packet_cnt = 0; 19526a438bbeSStephen Hemminger } 19531da177e4SLinus Torvalds 19541da177e4SLinus Torvalds /* First pass: retransmit lost packets. */ 19556a438bbeSStephen Hemminger if (tp->lost_out) { 1956fe067e8aSDavid S. Miller tcp_for_write_queue_from(skb, sk) { 19571da177e4SLinus Torvalds __u8 sacked = TCP_SKB_CB(skb)->sacked; 19581da177e4SLinus Torvalds 1959fe067e8aSDavid S. Miller if (skb == tcp_send_head(sk)) 1960fe067e8aSDavid S. Miller break; 19616a438bbeSStephen Hemminger /* we could do better than to assign each time */ 19626a438bbeSStephen Hemminger tp->retransmit_skb_hint = skb; 19636a438bbeSStephen Hemminger tp->retransmit_cnt_hint = packet_cnt; 19646a438bbeSStephen Hemminger 19651da177e4SLinus Torvalds /* Assume this retransmit will generate 19661da177e4SLinus Torvalds * only one packet for congestion window 19671da177e4SLinus Torvalds * calculation purposes. This works because 19681da177e4SLinus Torvalds * tcp_retransmit_skb() will chop up the 19691da177e4SLinus Torvalds * packet to be MSS sized and all the 19701da177e4SLinus Torvalds * packet counting works out. 19711da177e4SLinus Torvalds */ 19721da177e4SLinus Torvalds if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) 19731da177e4SLinus Torvalds return; 19741da177e4SLinus Torvalds 19751da177e4SLinus Torvalds if (sacked & TCPCB_LOST) { 19761da177e4SLinus Torvalds if (!(sacked&(TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) { 19776a438bbeSStephen Hemminger if (tcp_retransmit_skb(sk, skb)) { 19786a438bbeSStephen Hemminger tp->retransmit_skb_hint = NULL; 19791da177e4SLinus Torvalds return; 19806a438bbeSStephen Hemminger } 19816687e988SArnaldo Carvalho de Melo if (icsk->icsk_ca_state != TCP_CA_Loss) 19821da177e4SLinus Torvalds NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS); 19831da177e4SLinus Torvalds else 19841da177e4SLinus Torvalds NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS); 19851da177e4SLinus Torvalds 1986fe067e8aSDavid S. Miller if (skb == tcp_write_queue_head(sk)) 1987463c84b9SArnaldo Carvalho de Melo inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 19883f421baaSArnaldo Carvalho de Melo inet_csk(sk)->icsk_rto, 19893f421baaSArnaldo Carvalho de Melo TCP_RTO_MAX); 19901da177e4SLinus Torvalds } 19911da177e4SLinus Torvalds 19926a438bbeSStephen Hemminger packet_cnt += tcp_skb_pcount(skb); 19936a438bbeSStephen Hemminger if (packet_cnt >= tp->lost_out) 19941da177e4SLinus Torvalds break; 19951da177e4SLinus Torvalds } 19961da177e4SLinus Torvalds } 19971da177e4SLinus Torvalds } 19981da177e4SLinus Torvalds 19991da177e4SLinus Torvalds /* OK, demanded retransmission is finished. */ 20001da177e4SLinus Torvalds 20011da177e4SLinus Torvalds /* Forward retransmissions are possible only during Recovery. */ 20026687e988SArnaldo Carvalho de Melo if (icsk->icsk_ca_state != TCP_CA_Recovery) 20031da177e4SLinus Torvalds return; 20041da177e4SLinus Torvalds 20051da177e4SLinus Torvalds /* No forward retransmissions in Reno are possible. */ 2006e60402d0SIlpo Järvinen if (tcp_is_reno(tp)) 20071da177e4SLinus Torvalds return; 20081da177e4SLinus Torvalds 20091da177e4SLinus Torvalds /* Yeah, we have to make difficult choice between forward transmission 20101da177e4SLinus Torvalds * and retransmission... Both ways have their merits... 20111da177e4SLinus Torvalds * 20121da177e4SLinus Torvalds * For now we do not retransmit anything, while we have some new 2013539d243fSIlpo Järvinen * segments to send. In the other cases, follow rule 3 for 2014539d243fSIlpo Järvinen * NextSeg() specified in RFC3517. 20151da177e4SLinus Torvalds */ 20161da177e4SLinus Torvalds 20179e412ba7SIlpo Järvinen if (tcp_may_send_now(sk)) 20181da177e4SLinus Torvalds return; 20191da177e4SLinus Torvalds 2020539d243fSIlpo Järvinen /* If nothing is SACKed, highest_sack in the loop won't be valid */ 2021539d243fSIlpo Järvinen if (!tp->sacked_out) 2022539d243fSIlpo Järvinen return; 2023539d243fSIlpo Järvinen 2024539d243fSIlpo Järvinen if (tp->forward_skb_hint) 20256a438bbeSStephen Hemminger skb = tp->forward_skb_hint; 2026539d243fSIlpo Järvinen else 2027fe067e8aSDavid S. Miller skb = tcp_write_queue_head(sk); 20281da177e4SLinus Torvalds 2029fe067e8aSDavid S. Miller tcp_for_write_queue_from(skb, sk) { 2030fe067e8aSDavid S. Miller if (skb == tcp_send_head(sk)) 2031fe067e8aSDavid S. Miller break; 20326a438bbeSStephen Hemminger tp->forward_skb_hint = skb; 20336a438bbeSStephen Hemminger 2034539d243fSIlpo Järvinen if (after(TCP_SKB_CB(skb)->seq, tp->highest_sack)) 20351da177e4SLinus Torvalds break; 20361da177e4SLinus Torvalds 20371da177e4SLinus Torvalds if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) 20381da177e4SLinus Torvalds break; 20391da177e4SLinus Torvalds 20401da177e4SLinus Torvalds if (TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) 20411da177e4SLinus Torvalds continue; 20421da177e4SLinus Torvalds 20431da177e4SLinus Torvalds /* Ok, retransmit it. */ 20446a438bbeSStephen Hemminger if (tcp_retransmit_skb(sk, skb)) { 20456a438bbeSStephen Hemminger tp->forward_skb_hint = NULL; 20461da177e4SLinus Torvalds break; 20476a438bbeSStephen Hemminger } 20481da177e4SLinus Torvalds 2049fe067e8aSDavid S. Miller if (skb == tcp_write_queue_head(sk)) 20503f421baaSArnaldo Carvalho de Melo inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 20513f421baaSArnaldo Carvalho de Melo inet_csk(sk)->icsk_rto, 20523f421baaSArnaldo Carvalho de Melo TCP_RTO_MAX); 20531da177e4SLinus Torvalds 20541da177e4SLinus Torvalds NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS); 20551da177e4SLinus Torvalds } 20561da177e4SLinus Torvalds } 20571da177e4SLinus Torvalds 20581da177e4SLinus Torvalds 20591da177e4SLinus Torvalds /* Send a fin. The caller locks the socket for us. This cannot be 20601da177e4SLinus Torvalds * allowed to fail queueing a FIN frame under any circumstances. 20611da177e4SLinus Torvalds */ 20621da177e4SLinus Torvalds void tcp_send_fin(struct sock *sk) 20631da177e4SLinus Torvalds { 20641da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 2065fe067e8aSDavid S. Miller struct sk_buff *skb = tcp_write_queue_tail(sk); 20661da177e4SLinus Torvalds int mss_now; 20671da177e4SLinus Torvalds 20681da177e4SLinus Torvalds /* Optimization, tack on the FIN if we have a queue of 20691da177e4SLinus Torvalds * unsent frames. But be careful about outgoing SACKS 20701da177e4SLinus Torvalds * and IP options. 20711da177e4SLinus Torvalds */ 20721da177e4SLinus Torvalds mss_now = tcp_current_mss(sk, 1); 20731da177e4SLinus Torvalds 2074fe067e8aSDavid S. Miller if (tcp_send_head(sk) != NULL) { 20751da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN; 20761da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq++; 20771da177e4SLinus Torvalds tp->write_seq++; 20781da177e4SLinus Torvalds } else { 20791da177e4SLinus Torvalds /* Socket is locked, keep trying until memory is available. */ 20801da177e4SLinus Torvalds for (;;) { 2081d179cd12SDavid S. Miller skb = alloc_skb_fclone(MAX_TCP_HEADER, GFP_KERNEL); 20821da177e4SLinus Torvalds if (skb) 20831da177e4SLinus Torvalds break; 20841da177e4SLinus Torvalds yield(); 20851da177e4SLinus Torvalds } 20861da177e4SLinus Torvalds 20871da177e4SLinus Torvalds /* Reserve space for headers and prepare control bits. */ 20881da177e4SLinus Torvalds skb_reserve(skb, MAX_TCP_HEADER); 20891da177e4SLinus Torvalds skb->csum = 0; 20901da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_FIN); 20911da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked = 0; 20927967168cSHerbert Xu skb_shinfo(skb)->gso_segs = 1; 20937967168cSHerbert Xu skb_shinfo(skb)->gso_size = 0; 20947967168cSHerbert Xu skb_shinfo(skb)->gso_type = 0; 20951da177e4SLinus Torvalds 20961da177e4SLinus Torvalds /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */ 20971da177e4SLinus Torvalds TCP_SKB_CB(skb)->seq = tp->write_seq; 20981da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1; 20991da177e4SLinus Torvalds tcp_queue_skb(sk, skb); 21001da177e4SLinus Torvalds } 21019e412ba7SIlpo Järvinen __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF); 21021da177e4SLinus Torvalds } 21031da177e4SLinus Torvalds 21041da177e4SLinus Torvalds /* We get here when a process closes a file descriptor (either due to 21051da177e4SLinus Torvalds * an explicit close() or as a byproduct of exit()'ing) and there 21061da177e4SLinus Torvalds * was unread data in the receive queue. This behavior is recommended 210765bb723cSGerrit Renker * by RFC 2525, section 2.17. -DaveM 21081da177e4SLinus Torvalds */ 2109dd0fc66fSAl Viro void tcp_send_active_reset(struct sock *sk, gfp_t priority) 21101da177e4SLinus Torvalds { 21111da177e4SLinus Torvalds struct sk_buff *skb; 21121da177e4SLinus Torvalds 21131da177e4SLinus Torvalds /* NOTE: No TCP options attached and we never retransmit this. */ 21141da177e4SLinus Torvalds skb = alloc_skb(MAX_TCP_HEADER, priority); 21151da177e4SLinus Torvalds if (!skb) { 21161da177e4SLinus Torvalds NET_INC_STATS(LINUX_MIB_TCPABORTFAILED); 21171da177e4SLinus Torvalds return; 21181da177e4SLinus Torvalds } 21191da177e4SLinus Torvalds 21201da177e4SLinus Torvalds /* Reserve space for headers and prepare control bits. */ 21211da177e4SLinus Torvalds skb_reserve(skb, MAX_TCP_HEADER); 21221da177e4SLinus Torvalds skb->csum = 0; 21231da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_RST); 21241da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked = 0; 21257967168cSHerbert Xu skb_shinfo(skb)->gso_segs = 1; 21267967168cSHerbert Xu skb_shinfo(skb)->gso_size = 0; 21277967168cSHerbert Xu skb_shinfo(skb)->gso_type = 0; 21281da177e4SLinus Torvalds 21291da177e4SLinus Torvalds /* Send it off. */ 21309e412ba7SIlpo Järvinen TCP_SKB_CB(skb)->seq = tcp_acceptable_seq(sk); 21311da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq; 21321da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 2133dfb4b9dcSDavid S. Miller if (tcp_transmit_skb(sk, skb, 0, priority)) 21341da177e4SLinus Torvalds NET_INC_STATS(LINUX_MIB_TCPABORTFAILED); 21351da177e4SLinus Torvalds } 21361da177e4SLinus Torvalds 21371da177e4SLinus Torvalds /* WARNING: This routine must only be called when we have already sent 21381da177e4SLinus Torvalds * a SYN packet that crossed the incoming SYN that caused this routine 21391da177e4SLinus Torvalds * to get called. If this assumption fails then the initial rcv_wnd 21401da177e4SLinus Torvalds * and rcv_wscale values will not be correct. 21411da177e4SLinus Torvalds */ 21421da177e4SLinus Torvalds int tcp_send_synack(struct sock *sk) 21431da177e4SLinus Torvalds { 21441da177e4SLinus Torvalds struct sk_buff* skb; 21451da177e4SLinus Torvalds 2146fe067e8aSDavid S. Miller skb = tcp_write_queue_head(sk); 21471da177e4SLinus Torvalds if (skb == NULL || !(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_SYN)) { 21481da177e4SLinus Torvalds printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n"); 21491da177e4SLinus Torvalds return -EFAULT; 21501da177e4SLinus Torvalds } 21511da177e4SLinus Torvalds if (!(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_ACK)) { 21521da177e4SLinus Torvalds if (skb_cloned(skb)) { 21531da177e4SLinus Torvalds struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC); 21541da177e4SLinus Torvalds if (nskb == NULL) 21551da177e4SLinus Torvalds return -ENOMEM; 2156fe067e8aSDavid S. Miller tcp_unlink_write_queue(skb, sk); 21571da177e4SLinus Torvalds skb_header_release(nskb); 2158fe067e8aSDavid S. Miller __tcp_add_write_queue_head(sk, nskb); 21591da177e4SLinus Torvalds sk_stream_free_skb(sk, skb); 21601da177e4SLinus Torvalds sk_charge_skb(sk, nskb); 21611da177e4SLinus Torvalds skb = nskb; 21621da177e4SLinus Torvalds } 21631da177e4SLinus Torvalds 21641da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ACK; 21651da177e4SLinus Torvalds TCP_ECN_send_synack(tcp_sk(sk), skb); 21661da177e4SLinus Torvalds } 21671da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 2168dfb4b9dcSDavid S. Miller return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 21691da177e4SLinus Torvalds } 21701da177e4SLinus Torvalds 21711da177e4SLinus Torvalds /* 21721da177e4SLinus Torvalds * Prepare a SYN-ACK. 21731da177e4SLinus Torvalds */ 21741da177e4SLinus Torvalds struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst, 217560236fddSArnaldo Carvalho de Melo struct request_sock *req) 21761da177e4SLinus Torvalds { 21772e6599cbSArnaldo Carvalho de Melo struct inet_request_sock *ireq = inet_rsk(req); 21781da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 21791da177e4SLinus Torvalds struct tcphdr *th; 21801da177e4SLinus Torvalds int tcp_header_size; 21811da177e4SLinus Torvalds struct sk_buff *skb; 2182cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 2183cfb6eeb4SYOSHIFUJI Hideaki struct tcp_md5sig_key *md5; 2184cfb6eeb4SYOSHIFUJI Hideaki __u8 *md5_hash_location; 2185cfb6eeb4SYOSHIFUJI Hideaki #endif 21861da177e4SLinus Torvalds 21871da177e4SLinus Torvalds skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC); 21881da177e4SLinus Torvalds if (skb == NULL) 21891da177e4SLinus Torvalds return NULL; 21901da177e4SLinus Torvalds 21911da177e4SLinus Torvalds /* Reserve space for headers. */ 21921da177e4SLinus Torvalds skb_reserve(skb, MAX_TCP_HEADER); 21931da177e4SLinus Torvalds 21941da177e4SLinus Torvalds skb->dst = dst_clone(dst); 21951da177e4SLinus Torvalds 21961da177e4SLinus Torvalds tcp_header_size = (sizeof(struct tcphdr) + TCPOLEN_MSS + 21972e6599cbSArnaldo Carvalho de Melo (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) + 21982e6599cbSArnaldo Carvalho de Melo (ireq->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) + 21991da177e4SLinus Torvalds /* SACK_PERM is in the place of NOP NOP of TS */ 22002e6599cbSArnaldo Carvalho de Melo ((ireq->sack_ok && !ireq->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0)); 2201cfb6eeb4SYOSHIFUJI Hideaki 2202cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 2203cfb6eeb4SYOSHIFUJI Hideaki /* Are we doing MD5 on this segment? If so - make room for it */ 2204cfb6eeb4SYOSHIFUJI Hideaki md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req); 2205cfb6eeb4SYOSHIFUJI Hideaki if (md5) 2206cfb6eeb4SYOSHIFUJI Hideaki tcp_header_size += TCPOLEN_MD5SIG_ALIGNED; 2207cfb6eeb4SYOSHIFUJI Hideaki #endif 2208aa8223c7SArnaldo Carvalho de Melo skb_push(skb, tcp_header_size); 2209aa8223c7SArnaldo Carvalho de Melo skb_reset_transport_header(skb); 22101da177e4SLinus Torvalds 2211aa8223c7SArnaldo Carvalho de Melo th = tcp_hdr(skb); 22121da177e4SLinus Torvalds memset(th, 0, sizeof(struct tcphdr)); 22131da177e4SLinus Torvalds th->syn = 1; 22141da177e4SLinus Torvalds th->ack = 1; 22151da177e4SLinus Torvalds TCP_ECN_make_synack(req, th); 22161da177e4SLinus Torvalds th->source = inet_sk(sk)->sport; 22172e6599cbSArnaldo Carvalho de Melo th->dest = ireq->rmt_port; 22182e6599cbSArnaldo Carvalho de Melo TCP_SKB_CB(skb)->seq = tcp_rsk(req)->snt_isn; 22191da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1; 22201da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked = 0; 22217967168cSHerbert Xu skb_shinfo(skb)->gso_segs = 1; 22227967168cSHerbert Xu skb_shinfo(skb)->gso_size = 0; 22237967168cSHerbert Xu skb_shinfo(skb)->gso_type = 0; 22241da177e4SLinus Torvalds th->seq = htonl(TCP_SKB_CB(skb)->seq); 22252e6599cbSArnaldo Carvalho de Melo th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1); 22261da177e4SLinus Torvalds if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */ 22271da177e4SLinus Torvalds __u8 rcv_wscale; 22281da177e4SLinus Torvalds /* Set this up on the first call only */ 22291da177e4SLinus Torvalds req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW); 22301da177e4SLinus Torvalds /* tcp_full_space because it is guaranteed to be the first packet */ 22311da177e4SLinus Torvalds tcp_select_initial_window(tcp_full_space(sk), 22322e6599cbSArnaldo Carvalho de Melo dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0), 22331da177e4SLinus Torvalds &req->rcv_wnd, 22341da177e4SLinus Torvalds &req->window_clamp, 22352e6599cbSArnaldo Carvalho de Melo ireq->wscale_ok, 22361da177e4SLinus Torvalds &rcv_wscale); 22372e6599cbSArnaldo Carvalho de Melo ireq->rcv_wscale = rcv_wscale; 22381da177e4SLinus Torvalds } 22391da177e4SLinus Torvalds 22401da177e4SLinus Torvalds /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */ 2241600ff0c2SIlpo Järvinen th->window = htons(min(req->rcv_wnd, 65535U)); 22421da177e4SLinus Torvalds 22431da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 2244df7a3b07SAl Viro tcp_syn_build_options((__be32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), ireq->tstamp_ok, 22452e6599cbSArnaldo Carvalho de Melo ireq->sack_ok, ireq->wscale_ok, ireq->rcv_wscale, 22461da177e4SLinus Torvalds TCP_SKB_CB(skb)->when, 2247cfb6eeb4SYOSHIFUJI Hideaki req->ts_recent, 2248cfb6eeb4SYOSHIFUJI Hideaki ( 2249cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 2250cfb6eeb4SYOSHIFUJI Hideaki md5 ? &md5_hash_location : 2251cfb6eeb4SYOSHIFUJI Hideaki #endif 2252cfb6eeb4SYOSHIFUJI Hideaki NULL) 2253cfb6eeb4SYOSHIFUJI Hideaki ); 22541da177e4SLinus Torvalds 22551da177e4SLinus Torvalds skb->csum = 0; 22561da177e4SLinus Torvalds th->doff = (tcp_header_size >> 2); 22571da177e4SLinus Torvalds TCP_INC_STATS(TCP_MIB_OUTSEGS); 2258cfb6eeb4SYOSHIFUJI Hideaki 2259cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 2260cfb6eeb4SYOSHIFUJI Hideaki /* Okay, we have all we need - do the md5 hash if needed */ 2261cfb6eeb4SYOSHIFUJI Hideaki if (md5) { 2262cfb6eeb4SYOSHIFUJI Hideaki tp->af_specific->calc_md5_hash(md5_hash_location, 2263cfb6eeb4SYOSHIFUJI Hideaki md5, 2264cfb6eeb4SYOSHIFUJI Hideaki NULL, dst, req, 2265aa8223c7SArnaldo Carvalho de Melo tcp_hdr(skb), sk->sk_protocol, 2266cfb6eeb4SYOSHIFUJI Hideaki skb->len); 2267cfb6eeb4SYOSHIFUJI Hideaki } 2268cfb6eeb4SYOSHIFUJI Hideaki #endif 2269cfb6eeb4SYOSHIFUJI Hideaki 22701da177e4SLinus Torvalds return skb; 22711da177e4SLinus Torvalds } 22721da177e4SLinus Torvalds 22731da177e4SLinus Torvalds /* 22741da177e4SLinus Torvalds * Do all connect socket setups that can be done AF independent. 22751da177e4SLinus Torvalds */ 227640efc6faSStephen Hemminger static void tcp_connect_init(struct sock *sk) 22771da177e4SLinus Torvalds { 22781da177e4SLinus Torvalds struct dst_entry *dst = __sk_dst_get(sk); 22791da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 22801da177e4SLinus Torvalds __u8 rcv_wscale; 22811da177e4SLinus Torvalds 22821da177e4SLinus Torvalds /* We'll fix this up when we get a response from the other end. 22831da177e4SLinus Torvalds * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. 22841da177e4SLinus Torvalds */ 22851da177e4SLinus Torvalds tp->tcp_header_len = sizeof(struct tcphdr) + 22861da177e4SLinus Torvalds (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0); 22871da177e4SLinus Torvalds 2288cfb6eeb4SYOSHIFUJI Hideaki #ifdef CONFIG_TCP_MD5SIG 2289cfb6eeb4SYOSHIFUJI Hideaki if (tp->af_specific->md5_lookup(sk, sk) != NULL) 2290cfb6eeb4SYOSHIFUJI Hideaki tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; 2291cfb6eeb4SYOSHIFUJI Hideaki #endif 2292cfb6eeb4SYOSHIFUJI Hideaki 22931da177e4SLinus Torvalds /* If user gave his TCP_MAXSEG, record it to clamp */ 22941da177e4SLinus Torvalds if (tp->rx_opt.user_mss) 22951da177e4SLinus Torvalds tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; 22961da177e4SLinus Torvalds tp->max_window = 0; 22975d424d5aSJohn Heffner tcp_mtup_init(sk); 22981da177e4SLinus Torvalds tcp_sync_mss(sk, dst_mtu(dst)); 22991da177e4SLinus Torvalds 23001da177e4SLinus Torvalds if (!tp->window_clamp) 23011da177e4SLinus Torvalds tp->window_clamp = dst_metric(dst, RTAX_WINDOW); 23021da177e4SLinus Torvalds tp->advmss = dst_metric(dst, RTAX_ADVMSS); 23031da177e4SLinus Torvalds tcp_initialize_rcv_mss(sk); 23041da177e4SLinus Torvalds 23051da177e4SLinus Torvalds tcp_select_initial_window(tcp_full_space(sk), 23061da177e4SLinus Torvalds tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0), 23071da177e4SLinus Torvalds &tp->rcv_wnd, 23081da177e4SLinus Torvalds &tp->window_clamp, 23091da177e4SLinus Torvalds sysctl_tcp_window_scaling, 23101da177e4SLinus Torvalds &rcv_wscale); 23111da177e4SLinus Torvalds 23121da177e4SLinus Torvalds tp->rx_opt.rcv_wscale = rcv_wscale; 23131da177e4SLinus Torvalds tp->rcv_ssthresh = tp->rcv_wnd; 23141da177e4SLinus Torvalds 23151da177e4SLinus Torvalds sk->sk_err = 0; 23161da177e4SLinus Torvalds sock_reset_flag(sk, SOCK_DONE); 23171da177e4SLinus Torvalds tp->snd_wnd = 0; 23181da177e4SLinus Torvalds tcp_init_wl(tp, tp->write_seq, 0); 23191da177e4SLinus Torvalds tp->snd_una = tp->write_seq; 23201da177e4SLinus Torvalds tp->snd_sml = tp->write_seq; 23211da177e4SLinus Torvalds tp->rcv_nxt = 0; 23221da177e4SLinus Torvalds tp->rcv_wup = 0; 23231da177e4SLinus Torvalds tp->copied_seq = 0; 23241da177e4SLinus Torvalds 2325463c84b9SArnaldo Carvalho de Melo inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; 2326463c84b9SArnaldo Carvalho de Melo inet_csk(sk)->icsk_retransmits = 0; 23271da177e4SLinus Torvalds tcp_clear_retrans(tp); 23281da177e4SLinus Torvalds } 23291da177e4SLinus Torvalds 23301da177e4SLinus Torvalds /* 23311da177e4SLinus Torvalds * Build a SYN and send it off. 23321da177e4SLinus Torvalds */ 23331da177e4SLinus Torvalds int tcp_connect(struct sock *sk) 23341da177e4SLinus Torvalds { 23351da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 23361da177e4SLinus Torvalds struct sk_buff *buff; 23371da177e4SLinus Torvalds 23381da177e4SLinus Torvalds tcp_connect_init(sk); 23391da177e4SLinus Torvalds 2340d179cd12SDavid S. Miller buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation); 23411da177e4SLinus Torvalds if (unlikely(buff == NULL)) 23421da177e4SLinus Torvalds return -ENOBUFS; 23431da177e4SLinus Torvalds 23441da177e4SLinus Torvalds /* Reserve space for headers. */ 23451da177e4SLinus Torvalds skb_reserve(buff, MAX_TCP_HEADER); 23461da177e4SLinus Torvalds 23471da177e4SLinus Torvalds TCP_SKB_CB(buff)->flags = TCPCB_FLAG_SYN; 23489e412ba7SIlpo Järvinen TCP_ECN_send_syn(sk, buff); 23491da177e4SLinus Torvalds TCP_SKB_CB(buff)->sacked = 0; 23507967168cSHerbert Xu skb_shinfo(buff)->gso_segs = 1; 23517967168cSHerbert Xu skb_shinfo(buff)->gso_size = 0; 23527967168cSHerbert Xu skb_shinfo(buff)->gso_type = 0; 23531da177e4SLinus Torvalds buff->csum = 0; 2354bd37a088SWei Yongjun tp->snd_nxt = tp->write_seq; 23551da177e4SLinus Torvalds TCP_SKB_CB(buff)->seq = tp->write_seq++; 23561da177e4SLinus Torvalds TCP_SKB_CB(buff)->end_seq = tp->write_seq; 23571da177e4SLinus Torvalds 23581da177e4SLinus Torvalds /* Send it off. */ 23591da177e4SLinus Torvalds TCP_SKB_CB(buff)->when = tcp_time_stamp; 23601da177e4SLinus Torvalds tp->retrans_stamp = TCP_SKB_CB(buff)->when; 23611da177e4SLinus Torvalds skb_header_release(buff); 2362fe067e8aSDavid S. Miller __tcp_add_write_queue_tail(sk, buff); 23631da177e4SLinus Torvalds sk_charge_skb(sk, buff); 23641da177e4SLinus Torvalds tp->packets_out += tcp_skb_pcount(buff); 2365dfb4b9dcSDavid S. Miller tcp_transmit_skb(sk, buff, 1, GFP_KERNEL); 2366bd37a088SWei Yongjun 2367bd37a088SWei Yongjun /* We change tp->snd_nxt after the tcp_transmit_skb() call 2368bd37a088SWei Yongjun * in order to make this packet get counted in tcpOutSegs. 2369bd37a088SWei Yongjun */ 2370bd37a088SWei Yongjun tp->snd_nxt = tp->write_seq; 2371bd37a088SWei Yongjun tp->pushed_seq = tp->write_seq; 23721da177e4SLinus Torvalds TCP_INC_STATS(TCP_MIB_ACTIVEOPENS); 23731da177e4SLinus Torvalds 23741da177e4SLinus Torvalds /* Timer for repeating the SYN until an answer. */ 23753f421baaSArnaldo Carvalho de Melo inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 23763f421baaSArnaldo Carvalho de Melo inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 23771da177e4SLinus Torvalds return 0; 23781da177e4SLinus Torvalds } 23791da177e4SLinus Torvalds 23801da177e4SLinus Torvalds /* Send out a delayed ack, the caller does the policy checking 23811da177e4SLinus Torvalds * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check() 23821da177e4SLinus Torvalds * for details. 23831da177e4SLinus Torvalds */ 23841da177e4SLinus Torvalds void tcp_send_delayed_ack(struct sock *sk) 23851da177e4SLinus Torvalds { 2386463c84b9SArnaldo Carvalho de Melo struct inet_connection_sock *icsk = inet_csk(sk); 2387463c84b9SArnaldo Carvalho de Melo int ato = icsk->icsk_ack.ato; 23881da177e4SLinus Torvalds unsigned long timeout; 23891da177e4SLinus Torvalds 23901da177e4SLinus Torvalds if (ato > TCP_DELACK_MIN) { 2391463c84b9SArnaldo Carvalho de Melo const struct tcp_sock *tp = tcp_sk(sk); 23921da177e4SLinus Torvalds int max_ato = HZ/2; 23931da177e4SLinus Torvalds 2394463c84b9SArnaldo Carvalho de Melo if (icsk->icsk_ack.pingpong || (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)) 23951da177e4SLinus Torvalds max_ato = TCP_DELACK_MAX; 23961da177e4SLinus Torvalds 23971da177e4SLinus Torvalds /* Slow path, intersegment interval is "high". */ 23981da177e4SLinus Torvalds 23991da177e4SLinus Torvalds /* If some rtt estimate is known, use it to bound delayed ack. 2400463c84b9SArnaldo Carvalho de Melo * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements 24011da177e4SLinus Torvalds * directly. 24021da177e4SLinus Torvalds */ 24031da177e4SLinus Torvalds if (tp->srtt) { 24041da177e4SLinus Torvalds int rtt = max(tp->srtt>>3, TCP_DELACK_MIN); 24051da177e4SLinus Torvalds 24061da177e4SLinus Torvalds if (rtt < max_ato) 24071da177e4SLinus Torvalds max_ato = rtt; 24081da177e4SLinus Torvalds } 24091da177e4SLinus Torvalds 24101da177e4SLinus Torvalds ato = min(ato, max_ato); 24111da177e4SLinus Torvalds } 24121da177e4SLinus Torvalds 24131da177e4SLinus Torvalds /* Stay within the limit we were given */ 24141da177e4SLinus Torvalds timeout = jiffies + ato; 24151da177e4SLinus Torvalds 24161da177e4SLinus Torvalds /* Use new timeout only if there wasn't a older one earlier. */ 2417463c84b9SArnaldo Carvalho de Melo if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) { 24181da177e4SLinus Torvalds /* If delack timer was blocked or is about to expire, 24191da177e4SLinus Torvalds * send ACK now. 24201da177e4SLinus Torvalds */ 2421463c84b9SArnaldo Carvalho de Melo if (icsk->icsk_ack.blocked || 2422463c84b9SArnaldo Carvalho de Melo time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) { 24231da177e4SLinus Torvalds tcp_send_ack(sk); 24241da177e4SLinus Torvalds return; 24251da177e4SLinus Torvalds } 24261da177e4SLinus Torvalds 2427463c84b9SArnaldo Carvalho de Melo if (!time_before(timeout, icsk->icsk_ack.timeout)) 2428463c84b9SArnaldo Carvalho de Melo timeout = icsk->icsk_ack.timeout; 24291da177e4SLinus Torvalds } 2430463c84b9SArnaldo Carvalho de Melo icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; 2431463c84b9SArnaldo Carvalho de Melo icsk->icsk_ack.timeout = timeout; 2432463c84b9SArnaldo Carvalho de Melo sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); 24331da177e4SLinus Torvalds } 24341da177e4SLinus Torvalds 24351da177e4SLinus Torvalds /* This routine sends an ack and also updates the window. */ 24361da177e4SLinus Torvalds void tcp_send_ack(struct sock *sk) 24371da177e4SLinus Torvalds { 24381da177e4SLinus Torvalds /* If we have been reset, we may not send again. */ 24391da177e4SLinus Torvalds if (sk->sk_state != TCP_CLOSE) { 24401da177e4SLinus Torvalds struct sk_buff *buff; 24411da177e4SLinus Torvalds 24421da177e4SLinus Torvalds /* We are not putting this on the write queue, so 24431da177e4SLinus Torvalds * tcp_transmit_skb() will set the ownership to this 24441da177e4SLinus Torvalds * sock. 24451da177e4SLinus Torvalds */ 24461da177e4SLinus Torvalds buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); 24471da177e4SLinus Torvalds if (buff == NULL) { 2448463c84b9SArnaldo Carvalho de Melo inet_csk_schedule_ack(sk); 2449463c84b9SArnaldo Carvalho de Melo inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN; 24503f421baaSArnaldo Carvalho de Melo inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 24513f421baaSArnaldo Carvalho de Melo TCP_DELACK_MAX, TCP_RTO_MAX); 24521da177e4SLinus Torvalds return; 24531da177e4SLinus Torvalds } 24541da177e4SLinus Torvalds 24551da177e4SLinus Torvalds /* Reserve space for headers and prepare control bits. */ 24561da177e4SLinus Torvalds skb_reserve(buff, MAX_TCP_HEADER); 24571da177e4SLinus Torvalds buff->csum = 0; 24581da177e4SLinus Torvalds TCP_SKB_CB(buff)->flags = TCPCB_FLAG_ACK; 24591da177e4SLinus Torvalds TCP_SKB_CB(buff)->sacked = 0; 24607967168cSHerbert Xu skb_shinfo(buff)->gso_segs = 1; 24617967168cSHerbert Xu skb_shinfo(buff)->gso_size = 0; 24627967168cSHerbert Xu skb_shinfo(buff)->gso_type = 0; 24631da177e4SLinus Torvalds 24641da177e4SLinus Torvalds /* Send it off, this clears delayed acks for us. */ 24659e412ba7SIlpo Järvinen TCP_SKB_CB(buff)->seq = TCP_SKB_CB(buff)->end_seq = tcp_acceptable_seq(sk); 24661da177e4SLinus Torvalds TCP_SKB_CB(buff)->when = tcp_time_stamp; 2467dfb4b9dcSDavid S. Miller tcp_transmit_skb(sk, buff, 0, GFP_ATOMIC); 24681da177e4SLinus Torvalds } 24691da177e4SLinus Torvalds } 24701da177e4SLinus Torvalds 24711da177e4SLinus Torvalds /* This routine sends a packet with an out of date sequence 24721da177e4SLinus Torvalds * number. It assumes the other end will try to ack it. 24731da177e4SLinus Torvalds * 24741da177e4SLinus Torvalds * Question: what should we make while urgent mode? 24751da177e4SLinus Torvalds * 4.4BSD forces sending single byte of data. We cannot send 24761da177e4SLinus Torvalds * out of window data, because we have SND.NXT==SND.MAX... 24771da177e4SLinus Torvalds * 24781da177e4SLinus Torvalds * Current solution: to send TWO zero-length segments in urgent mode: 24791da177e4SLinus Torvalds * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is 24801da177e4SLinus Torvalds * out-of-date with SND.UNA-1 to probe window. 24811da177e4SLinus Torvalds */ 24821da177e4SLinus Torvalds static int tcp_xmit_probe_skb(struct sock *sk, int urgent) 24831da177e4SLinus Torvalds { 24841da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 24851da177e4SLinus Torvalds struct sk_buff *skb; 24861da177e4SLinus Torvalds 24871da177e4SLinus Torvalds /* We don't queue it, tcp_transmit_skb() sets ownership. */ 24881da177e4SLinus Torvalds skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); 24891da177e4SLinus Torvalds if (skb == NULL) 24901da177e4SLinus Torvalds return -1; 24911da177e4SLinus Torvalds 24921da177e4SLinus Torvalds /* Reserve space for headers and set control bits. */ 24931da177e4SLinus Torvalds skb_reserve(skb, MAX_TCP_HEADER); 24941da177e4SLinus Torvalds skb->csum = 0; 24951da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags = TCPCB_FLAG_ACK; 24961da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked = urgent; 24977967168cSHerbert Xu skb_shinfo(skb)->gso_segs = 1; 24987967168cSHerbert Xu skb_shinfo(skb)->gso_size = 0; 24997967168cSHerbert Xu skb_shinfo(skb)->gso_type = 0; 25001da177e4SLinus Torvalds 25011da177e4SLinus Torvalds /* Use a previous sequence. This should cause the other 25021da177e4SLinus Torvalds * end to send an ack. Don't queue or clone SKB, just 25031da177e4SLinus Torvalds * send it. 25041da177e4SLinus Torvalds */ 25051da177e4SLinus Torvalds TCP_SKB_CB(skb)->seq = urgent ? tp->snd_una : tp->snd_una - 1; 25061da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq; 25071da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 2508dfb4b9dcSDavid S. Miller return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC); 25091da177e4SLinus Torvalds } 25101da177e4SLinus Torvalds 25111da177e4SLinus Torvalds int tcp_write_wakeup(struct sock *sk) 25121da177e4SLinus Torvalds { 25131da177e4SLinus Torvalds if (sk->sk_state != TCP_CLOSE) { 25141da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 25151da177e4SLinus Torvalds struct sk_buff *skb; 25161da177e4SLinus Torvalds 2517fe067e8aSDavid S. Miller if ((skb = tcp_send_head(sk)) != NULL && 25181da177e4SLinus Torvalds before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)) { 25191da177e4SLinus Torvalds int err; 25201da177e4SLinus Torvalds unsigned int mss = tcp_current_mss(sk, 0); 25211da177e4SLinus Torvalds unsigned int seg_size = tp->snd_una+tp->snd_wnd-TCP_SKB_CB(skb)->seq; 25221da177e4SLinus Torvalds 25231da177e4SLinus Torvalds if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq)) 25241da177e4SLinus Torvalds tp->pushed_seq = TCP_SKB_CB(skb)->end_seq; 25251da177e4SLinus Torvalds 25261da177e4SLinus Torvalds /* We are probing the opening of a window 25271da177e4SLinus Torvalds * but the window size is != 0 25281da177e4SLinus Torvalds * must have been a result SWS avoidance ( sender ) 25291da177e4SLinus Torvalds */ 25301da177e4SLinus Torvalds if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq || 25311da177e4SLinus Torvalds skb->len > mss) { 25321da177e4SLinus Torvalds seg_size = min(seg_size, mss); 25331da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; 2534846998aeSDavid S. Miller if (tcp_fragment(sk, skb, seg_size, mss)) 25351da177e4SLinus Torvalds return -1; 25361da177e4SLinus Torvalds } else if (!tcp_skb_pcount(skb)) 2537846998aeSDavid S. Miller tcp_set_skb_tso_segs(sk, skb, mss); 25381da177e4SLinus Torvalds 25391da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; 25401da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 2541dfb4b9dcSDavid S. Miller err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 25421da177e4SLinus Torvalds if (!err) { 25439e412ba7SIlpo Järvinen update_send_head(sk, skb); 25441da177e4SLinus Torvalds } 25451da177e4SLinus Torvalds return err; 25461da177e4SLinus Torvalds } else { 25471da177e4SLinus Torvalds if (tp->urg_mode && 25481da177e4SLinus Torvalds between(tp->snd_up, tp->snd_una+1, tp->snd_una+0xFFFF)) 25491da177e4SLinus Torvalds tcp_xmit_probe_skb(sk, TCPCB_URG); 25501da177e4SLinus Torvalds return tcp_xmit_probe_skb(sk, 0); 25511da177e4SLinus Torvalds } 25521da177e4SLinus Torvalds } 25531da177e4SLinus Torvalds return -1; 25541da177e4SLinus Torvalds } 25551da177e4SLinus Torvalds 25561da177e4SLinus Torvalds /* A window probe timeout has occurred. If window is not closed send 25571da177e4SLinus Torvalds * a partial packet else a zero probe. 25581da177e4SLinus Torvalds */ 25591da177e4SLinus Torvalds void tcp_send_probe0(struct sock *sk) 25601da177e4SLinus Torvalds { 2561463c84b9SArnaldo Carvalho de Melo struct inet_connection_sock *icsk = inet_csk(sk); 25621da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 25631da177e4SLinus Torvalds int err; 25641da177e4SLinus Torvalds 25651da177e4SLinus Torvalds err = tcp_write_wakeup(sk); 25661da177e4SLinus Torvalds 2567fe067e8aSDavid S. Miller if (tp->packets_out || !tcp_send_head(sk)) { 25681da177e4SLinus Torvalds /* Cancel probe timer, if it is not required. */ 25696687e988SArnaldo Carvalho de Melo icsk->icsk_probes_out = 0; 2570463c84b9SArnaldo Carvalho de Melo icsk->icsk_backoff = 0; 25711da177e4SLinus Torvalds return; 25721da177e4SLinus Torvalds } 25731da177e4SLinus Torvalds 25741da177e4SLinus Torvalds if (err <= 0) { 2575463c84b9SArnaldo Carvalho de Melo if (icsk->icsk_backoff < sysctl_tcp_retries2) 2576463c84b9SArnaldo Carvalho de Melo icsk->icsk_backoff++; 25776687e988SArnaldo Carvalho de Melo icsk->icsk_probes_out++; 2578463c84b9SArnaldo Carvalho de Melo inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 25793f421baaSArnaldo Carvalho de Melo min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 25803f421baaSArnaldo Carvalho de Melo TCP_RTO_MAX); 25811da177e4SLinus Torvalds } else { 25821da177e4SLinus Torvalds /* If packet was not sent due to local congestion, 25836687e988SArnaldo Carvalho de Melo * do not backoff and do not remember icsk_probes_out. 25841da177e4SLinus Torvalds * Let local senders to fight for local resources. 25851da177e4SLinus Torvalds * 25861da177e4SLinus Torvalds * Use accumulated backoff yet. 25871da177e4SLinus Torvalds */ 25886687e988SArnaldo Carvalho de Melo if (!icsk->icsk_probes_out) 25896687e988SArnaldo Carvalho de Melo icsk->icsk_probes_out = 1; 2590463c84b9SArnaldo Carvalho de Melo inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 2591463c84b9SArnaldo Carvalho de Melo min(icsk->icsk_rto << icsk->icsk_backoff, 25923f421baaSArnaldo Carvalho de Melo TCP_RESOURCE_PROBE_INTERVAL), 25933f421baaSArnaldo Carvalho de Melo TCP_RTO_MAX); 25941da177e4SLinus Torvalds } 25951da177e4SLinus Torvalds } 25961da177e4SLinus Torvalds 25971da177e4SLinus Torvalds EXPORT_SYMBOL(tcp_connect); 25981da177e4SLinus Torvalds EXPORT_SYMBOL(tcp_make_synack); 25991da177e4SLinus Torvalds EXPORT_SYMBOL(tcp_simple_retransmit); 26001da177e4SLinus Torvalds EXPORT_SYMBOL(tcp_sync_mss); 2601f4805edeSStephen Hemminger EXPORT_SYMBOL(sysctl_tcp_tso_win_divisor); 26025d424d5aSJohn Heffner EXPORT_SYMBOL(tcp_mtup_init); 2603