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 #include <linux/smp_lock.h> 441da177e4SLinus Torvalds 451da177e4SLinus Torvalds /* People can turn this off for buggy TCP's found in printers etc. */ 461da177e4SLinus Torvalds int sysctl_tcp_retrans_collapse = 1; 471da177e4SLinus Torvalds 481da177e4SLinus Torvalds /* This limits the percentage of the congestion window which we 491da177e4SLinus Torvalds * will allow a single TSO frame to consume. Building TSO frames 501da177e4SLinus Torvalds * which are too large can cause TCP streams to be bursty. 511da177e4SLinus Torvalds */ 521da177e4SLinus Torvalds int sysctl_tcp_tso_win_divisor = 8; 531da177e4SLinus Torvalds 541da177e4SLinus Torvalds static inline void update_send_head(struct sock *sk, struct tcp_sock *tp, 551da177e4SLinus Torvalds struct sk_buff *skb) 561da177e4SLinus Torvalds { 571da177e4SLinus Torvalds sk->sk_send_head = skb->next; 581da177e4SLinus Torvalds if (sk->sk_send_head == (struct sk_buff *)&sk->sk_write_queue) 591da177e4SLinus Torvalds sk->sk_send_head = NULL; 601da177e4SLinus Torvalds tp->snd_nxt = TCP_SKB_CB(skb)->end_seq; 611da177e4SLinus Torvalds tcp_packets_out_inc(sk, tp, skb); 621da177e4SLinus Torvalds } 631da177e4SLinus Torvalds 641da177e4SLinus Torvalds /* SND.NXT, if window was not shrunk. 651da177e4SLinus Torvalds * If window has been shrunk, what should we make? It is not clear at all. 661da177e4SLinus Torvalds * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-( 671da177e4SLinus Torvalds * Anything in between SND.UNA...SND.UNA+SND.WND also can be already 681da177e4SLinus Torvalds * invalid. OK, let's make this for now: 691da177e4SLinus Torvalds */ 701da177e4SLinus Torvalds static inline __u32 tcp_acceptable_seq(struct sock *sk, struct tcp_sock *tp) 711da177e4SLinus Torvalds { 721da177e4SLinus Torvalds if (!before(tp->snd_una+tp->snd_wnd, tp->snd_nxt)) 731da177e4SLinus Torvalds return tp->snd_nxt; 741da177e4SLinus Torvalds else 751da177e4SLinus Torvalds return tp->snd_una+tp->snd_wnd; 761da177e4SLinus Torvalds } 771da177e4SLinus Torvalds 781da177e4SLinus Torvalds /* Calculate mss to advertise in SYN segment. 791da177e4SLinus Torvalds * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that: 801da177e4SLinus Torvalds * 811da177e4SLinus Torvalds * 1. It is independent of path mtu. 821da177e4SLinus Torvalds * 2. Ideally, it is maximal possible segment size i.e. 65535-40. 831da177e4SLinus Torvalds * 3. For IPv4 it is reasonable to calculate it from maximal MTU of 841da177e4SLinus Torvalds * attached devices, because some buggy hosts are confused by 851da177e4SLinus Torvalds * large MSS. 861da177e4SLinus Torvalds * 4. We do not make 3, we advertise MSS, calculated from first 871da177e4SLinus Torvalds * hop device mtu, but allow to raise it to ip_rt_min_advmss. 881da177e4SLinus Torvalds * This may be overridden via information stored in routing table. 891da177e4SLinus Torvalds * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible, 901da177e4SLinus Torvalds * probably even Jumbo". 911da177e4SLinus Torvalds */ 921da177e4SLinus Torvalds static __u16 tcp_advertise_mss(struct sock *sk) 931da177e4SLinus Torvalds { 941da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 951da177e4SLinus Torvalds struct dst_entry *dst = __sk_dst_get(sk); 961da177e4SLinus Torvalds int mss = tp->advmss; 971da177e4SLinus Torvalds 981da177e4SLinus Torvalds if (dst && dst_metric(dst, RTAX_ADVMSS) < mss) { 991da177e4SLinus Torvalds mss = dst_metric(dst, RTAX_ADVMSS); 1001da177e4SLinus Torvalds tp->advmss = mss; 1011da177e4SLinus Torvalds } 1021da177e4SLinus Torvalds 1031da177e4SLinus Torvalds return (__u16)mss; 1041da177e4SLinus Torvalds } 1051da177e4SLinus Torvalds 1061da177e4SLinus Torvalds /* RFC2861. Reset CWND after idle period longer RTO to "restart window". 1071da177e4SLinus Torvalds * This is the first part of cwnd validation mechanism. */ 1081da177e4SLinus Torvalds static void tcp_cwnd_restart(struct tcp_sock *tp, struct dst_entry *dst) 1091da177e4SLinus Torvalds { 1101da177e4SLinus Torvalds s32 delta = tcp_time_stamp - tp->lsndtime; 1111da177e4SLinus Torvalds u32 restart_cwnd = tcp_init_cwnd(tp, dst); 1121da177e4SLinus Torvalds u32 cwnd = tp->snd_cwnd; 1131da177e4SLinus Torvalds 114317a76f9SStephen Hemminger tcp_ca_event(tp, CA_EVENT_CWND_RESTART); 1151da177e4SLinus Torvalds 1161da177e4SLinus Torvalds tp->snd_ssthresh = tcp_current_ssthresh(tp); 1171da177e4SLinus Torvalds restart_cwnd = min(restart_cwnd, cwnd); 1181da177e4SLinus Torvalds 1191da177e4SLinus Torvalds while ((delta -= tp->rto) > 0 && cwnd > restart_cwnd) 1201da177e4SLinus Torvalds cwnd >>= 1; 1211da177e4SLinus Torvalds tp->snd_cwnd = max(cwnd, restart_cwnd); 1221da177e4SLinus Torvalds tp->snd_cwnd_stamp = tcp_time_stamp; 1231da177e4SLinus Torvalds tp->snd_cwnd_used = 0; 1241da177e4SLinus Torvalds } 1251da177e4SLinus Torvalds 1261da177e4SLinus Torvalds static inline void tcp_event_data_sent(struct tcp_sock *tp, 1271da177e4SLinus Torvalds struct sk_buff *skb, struct sock *sk) 1281da177e4SLinus Torvalds { 1291da177e4SLinus Torvalds u32 now = tcp_time_stamp; 1301da177e4SLinus Torvalds 1311da177e4SLinus Torvalds if (!tp->packets_out && (s32)(now - tp->lsndtime) > tp->rto) 1321da177e4SLinus Torvalds tcp_cwnd_restart(tp, __sk_dst_get(sk)); 1331da177e4SLinus Torvalds 1341da177e4SLinus Torvalds tp->lsndtime = now; 1351da177e4SLinus Torvalds 1361da177e4SLinus Torvalds /* If it is a reply for ato after last received 1371da177e4SLinus Torvalds * packet, enter pingpong mode. 1381da177e4SLinus Torvalds */ 1391da177e4SLinus Torvalds if ((u32)(now - tp->ack.lrcvtime) < tp->ack.ato) 1401da177e4SLinus Torvalds tp->ack.pingpong = 1; 1411da177e4SLinus Torvalds } 1421da177e4SLinus Torvalds 143fc6415bcSDavid S. Miller static __inline__ void tcp_event_ack_sent(struct sock *sk, unsigned int pkts) 1441da177e4SLinus Torvalds { 1451da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 1461da177e4SLinus Torvalds 147fc6415bcSDavid S. Miller tcp_dec_quickack_mode(tp, pkts); 1481da177e4SLinus Torvalds tcp_clear_xmit_timer(sk, TCP_TIME_DACK); 1491da177e4SLinus Torvalds } 1501da177e4SLinus Torvalds 1511da177e4SLinus Torvalds /* Determine a window scaling and initial window to offer. 1521da177e4SLinus Torvalds * Based on the assumption that the given amount of space 1531da177e4SLinus Torvalds * will be offered. Store the results in the tp structure. 1541da177e4SLinus Torvalds * NOTE: for smooth operation initial space offering should 1551da177e4SLinus Torvalds * be a multiple of mss if possible. We assume here that mss >= 1. 1561da177e4SLinus Torvalds * This MUST be enforced by all callers. 1571da177e4SLinus Torvalds */ 1581da177e4SLinus Torvalds void tcp_select_initial_window(int __space, __u32 mss, 1591da177e4SLinus Torvalds __u32 *rcv_wnd, __u32 *window_clamp, 1601da177e4SLinus Torvalds int wscale_ok, __u8 *rcv_wscale) 1611da177e4SLinus Torvalds { 1621da177e4SLinus Torvalds unsigned int space = (__space < 0 ? 0 : __space); 1631da177e4SLinus Torvalds 1641da177e4SLinus Torvalds /* If no clamp set the clamp to the max possible scaled window */ 1651da177e4SLinus Torvalds if (*window_clamp == 0) 1661da177e4SLinus Torvalds (*window_clamp) = (65535 << 14); 1671da177e4SLinus Torvalds space = min(*window_clamp, space); 1681da177e4SLinus Torvalds 1691da177e4SLinus Torvalds /* Quantize space offering to a multiple of mss if possible. */ 1701da177e4SLinus Torvalds if (space > mss) 1711da177e4SLinus Torvalds space = (space / mss) * mss; 1721da177e4SLinus Torvalds 1731da177e4SLinus Torvalds /* NOTE: offering an initial window larger than 32767 1741da177e4SLinus Torvalds * will break some buggy TCP stacks. We try to be nice. 1751da177e4SLinus Torvalds * If we are not window scaling, then this truncates 1761da177e4SLinus Torvalds * our initial window offering to 32k. There should also 1771da177e4SLinus Torvalds * be a sysctl option to stop being nice. 1781da177e4SLinus Torvalds */ 1791da177e4SLinus Torvalds (*rcv_wnd) = min(space, MAX_TCP_WINDOW); 1801da177e4SLinus Torvalds (*rcv_wscale) = 0; 1811da177e4SLinus Torvalds if (wscale_ok) { 1821da177e4SLinus Torvalds /* Set window scaling on max possible window 1831da177e4SLinus Torvalds * See RFC1323 for an explanation of the limit to 14 1841da177e4SLinus Torvalds */ 1851da177e4SLinus Torvalds space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max); 1861da177e4SLinus Torvalds while (space > 65535 && (*rcv_wscale) < 14) { 1871da177e4SLinus Torvalds space >>= 1; 1881da177e4SLinus Torvalds (*rcv_wscale)++; 1891da177e4SLinus Torvalds } 1901da177e4SLinus Torvalds } 1911da177e4SLinus Torvalds 1921da177e4SLinus Torvalds /* Set initial window to value enough for senders, 1931da177e4SLinus Torvalds * following RFC1414. Senders, not following this RFC, 1941da177e4SLinus Torvalds * will be satisfied with 2. 1951da177e4SLinus Torvalds */ 1961da177e4SLinus Torvalds if (mss > (1<<*rcv_wscale)) { 1971da177e4SLinus Torvalds int init_cwnd = 4; 1981da177e4SLinus Torvalds if (mss > 1460*3) 1991da177e4SLinus Torvalds init_cwnd = 2; 2001da177e4SLinus Torvalds else if (mss > 1460) 2011da177e4SLinus Torvalds init_cwnd = 3; 2021da177e4SLinus Torvalds if (*rcv_wnd > init_cwnd*mss) 2031da177e4SLinus Torvalds *rcv_wnd = init_cwnd*mss; 2041da177e4SLinus Torvalds } 2051da177e4SLinus Torvalds 2061da177e4SLinus Torvalds /* Set the clamp no higher than max representable value */ 2071da177e4SLinus Torvalds (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp); 2081da177e4SLinus Torvalds } 2091da177e4SLinus Torvalds 2101da177e4SLinus Torvalds /* Chose a new window to advertise, update state in tcp_sock for the 2111da177e4SLinus Torvalds * socket, and return result with RFC1323 scaling applied. The return 2121da177e4SLinus Torvalds * value can be stuffed directly into th->window for an outgoing 2131da177e4SLinus Torvalds * frame. 2141da177e4SLinus Torvalds */ 2151da177e4SLinus Torvalds static __inline__ u16 tcp_select_window(struct sock *sk) 2161da177e4SLinus Torvalds { 2171da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 2181da177e4SLinus Torvalds u32 cur_win = tcp_receive_window(tp); 2191da177e4SLinus Torvalds u32 new_win = __tcp_select_window(sk); 2201da177e4SLinus Torvalds 2211da177e4SLinus Torvalds /* Never shrink the offered window */ 2221da177e4SLinus Torvalds if(new_win < cur_win) { 2231da177e4SLinus Torvalds /* Danger Will Robinson! 2241da177e4SLinus Torvalds * Don't update rcv_wup/rcv_wnd here or else 2251da177e4SLinus Torvalds * we will not be able to advertise a zero 2261da177e4SLinus Torvalds * window in time. --DaveM 2271da177e4SLinus Torvalds * 2281da177e4SLinus Torvalds * Relax Will Robinson. 2291da177e4SLinus Torvalds */ 2301da177e4SLinus Torvalds new_win = cur_win; 2311da177e4SLinus Torvalds } 2321da177e4SLinus Torvalds tp->rcv_wnd = new_win; 2331da177e4SLinus Torvalds tp->rcv_wup = tp->rcv_nxt; 2341da177e4SLinus Torvalds 2351da177e4SLinus Torvalds /* Make sure we do not exceed the maximum possible 2361da177e4SLinus Torvalds * scaled window. 2371da177e4SLinus Torvalds */ 2381da177e4SLinus Torvalds if (!tp->rx_opt.rcv_wscale) 2391da177e4SLinus Torvalds new_win = min(new_win, MAX_TCP_WINDOW); 2401da177e4SLinus Torvalds else 2411da177e4SLinus Torvalds new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); 2421da177e4SLinus Torvalds 2431da177e4SLinus Torvalds /* RFC1323 scaling applied */ 2441da177e4SLinus Torvalds new_win >>= tp->rx_opt.rcv_wscale; 2451da177e4SLinus Torvalds 2461da177e4SLinus Torvalds /* If we advertise zero window, disable fast path. */ 2471da177e4SLinus Torvalds if (new_win == 0) 2481da177e4SLinus Torvalds tp->pred_flags = 0; 2491da177e4SLinus Torvalds 2501da177e4SLinus Torvalds return new_win; 2511da177e4SLinus Torvalds } 2521da177e4SLinus Torvalds 2531da177e4SLinus Torvalds 2541da177e4SLinus Torvalds /* This routine actually transmits TCP packets queued in by 2551da177e4SLinus Torvalds * tcp_do_sendmsg(). This is used by both the initial 2561da177e4SLinus Torvalds * transmission and possible later retransmissions. 2571da177e4SLinus Torvalds * All SKB's seen here are completely headerless. It is our 2581da177e4SLinus Torvalds * job to build the TCP header, and pass the packet down to 2591da177e4SLinus Torvalds * IP so it can do the same plus pass the packet off to the 2601da177e4SLinus Torvalds * device. 2611da177e4SLinus Torvalds * 2621da177e4SLinus Torvalds * We are working here with either a clone of the original 2631da177e4SLinus Torvalds * SKB, or a fresh unique copy made by the retransmit engine. 2641da177e4SLinus Torvalds */ 2651da177e4SLinus Torvalds static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb) 2661da177e4SLinus Torvalds { 2671da177e4SLinus Torvalds if (skb != NULL) { 2681da177e4SLinus Torvalds struct inet_sock *inet = inet_sk(sk); 2691da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 2701da177e4SLinus Torvalds struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); 2711da177e4SLinus Torvalds int tcp_header_size = tp->tcp_header_len; 2721da177e4SLinus Torvalds struct tcphdr *th; 2731da177e4SLinus Torvalds int sysctl_flags; 2741da177e4SLinus Torvalds int err; 2751da177e4SLinus Torvalds 2761da177e4SLinus Torvalds BUG_ON(!tcp_skb_pcount(skb)); 2771da177e4SLinus Torvalds 2781da177e4SLinus Torvalds #define SYSCTL_FLAG_TSTAMPS 0x1 2791da177e4SLinus Torvalds #define SYSCTL_FLAG_WSCALE 0x2 2801da177e4SLinus Torvalds #define SYSCTL_FLAG_SACK 0x4 2811da177e4SLinus Torvalds 282317a76f9SStephen Hemminger /* If congestion control is doing timestamping */ 283317a76f9SStephen Hemminger if (tp->ca_ops->rtt_sample) 284317a76f9SStephen Hemminger do_gettimeofday(&skb->stamp); 285317a76f9SStephen Hemminger 2861da177e4SLinus Torvalds sysctl_flags = 0; 2871da177e4SLinus Torvalds if (tcb->flags & TCPCB_FLAG_SYN) { 2881da177e4SLinus Torvalds tcp_header_size = sizeof(struct tcphdr) + TCPOLEN_MSS; 2891da177e4SLinus Torvalds if(sysctl_tcp_timestamps) { 2901da177e4SLinus Torvalds tcp_header_size += TCPOLEN_TSTAMP_ALIGNED; 2911da177e4SLinus Torvalds sysctl_flags |= SYSCTL_FLAG_TSTAMPS; 2921da177e4SLinus Torvalds } 2931da177e4SLinus Torvalds if(sysctl_tcp_window_scaling) { 2941da177e4SLinus Torvalds tcp_header_size += TCPOLEN_WSCALE_ALIGNED; 2951da177e4SLinus Torvalds sysctl_flags |= SYSCTL_FLAG_WSCALE; 2961da177e4SLinus Torvalds } 2971da177e4SLinus Torvalds if(sysctl_tcp_sack) { 2981da177e4SLinus Torvalds sysctl_flags |= SYSCTL_FLAG_SACK; 2991da177e4SLinus Torvalds if(!(sysctl_flags & SYSCTL_FLAG_TSTAMPS)) 3001da177e4SLinus Torvalds tcp_header_size += TCPOLEN_SACKPERM_ALIGNED; 3011da177e4SLinus Torvalds } 3021da177e4SLinus Torvalds } else if (tp->rx_opt.eff_sacks) { 3031da177e4SLinus Torvalds /* A SACK is 2 pad bytes, a 2 byte header, plus 3041da177e4SLinus Torvalds * 2 32-bit sequence numbers for each SACK block. 3051da177e4SLinus Torvalds */ 3061da177e4SLinus Torvalds tcp_header_size += (TCPOLEN_SACK_BASE_ALIGNED + 3071da177e4SLinus Torvalds (tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK)); 3081da177e4SLinus Torvalds } 3091da177e4SLinus Torvalds 310317a76f9SStephen Hemminger if (tcp_packets_in_flight(tp) == 0) 311317a76f9SStephen Hemminger tcp_ca_event(tp, CA_EVENT_TX_START); 3121da177e4SLinus Torvalds 3131da177e4SLinus Torvalds th = (struct tcphdr *) skb_push(skb, tcp_header_size); 3141da177e4SLinus Torvalds skb->h.th = th; 3151da177e4SLinus Torvalds skb_set_owner_w(skb, sk); 3161da177e4SLinus Torvalds 3171da177e4SLinus Torvalds /* Build TCP header and checksum it. */ 3181da177e4SLinus Torvalds th->source = inet->sport; 3191da177e4SLinus Torvalds th->dest = inet->dport; 3201da177e4SLinus Torvalds th->seq = htonl(tcb->seq); 3211da177e4SLinus Torvalds th->ack_seq = htonl(tp->rcv_nxt); 3221da177e4SLinus Torvalds *(((__u16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) | tcb->flags); 3231da177e4SLinus Torvalds if (tcb->flags & TCPCB_FLAG_SYN) { 3241da177e4SLinus Torvalds /* RFC1323: The window in SYN & SYN/ACK segments 3251da177e4SLinus Torvalds * is never scaled. 3261da177e4SLinus Torvalds */ 3271da177e4SLinus Torvalds th->window = htons(tp->rcv_wnd); 3281da177e4SLinus Torvalds } else { 3291da177e4SLinus Torvalds th->window = htons(tcp_select_window(sk)); 3301da177e4SLinus Torvalds } 3311da177e4SLinus Torvalds th->check = 0; 3321da177e4SLinus Torvalds th->urg_ptr = 0; 3331da177e4SLinus Torvalds 3341da177e4SLinus Torvalds if (tp->urg_mode && 3351da177e4SLinus Torvalds between(tp->snd_up, tcb->seq+1, tcb->seq+0xFFFF)) { 3361da177e4SLinus Torvalds th->urg_ptr = htons(tp->snd_up-tcb->seq); 3371da177e4SLinus Torvalds th->urg = 1; 3381da177e4SLinus Torvalds } 3391da177e4SLinus Torvalds 3401da177e4SLinus Torvalds if (tcb->flags & TCPCB_FLAG_SYN) { 3411da177e4SLinus Torvalds tcp_syn_build_options((__u32 *)(th + 1), 3421da177e4SLinus Torvalds tcp_advertise_mss(sk), 3431da177e4SLinus Torvalds (sysctl_flags & SYSCTL_FLAG_TSTAMPS), 3441da177e4SLinus Torvalds (sysctl_flags & SYSCTL_FLAG_SACK), 3451da177e4SLinus Torvalds (sysctl_flags & SYSCTL_FLAG_WSCALE), 3461da177e4SLinus Torvalds tp->rx_opt.rcv_wscale, 3471da177e4SLinus Torvalds tcb->when, 3481da177e4SLinus Torvalds tp->rx_opt.ts_recent); 3491da177e4SLinus Torvalds } else { 3501da177e4SLinus Torvalds tcp_build_and_update_options((__u32 *)(th + 1), 3511da177e4SLinus Torvalds tp, tcb->when); 3521da177e4SLinus Torvalds 3531da177e4SLinus Torvalds TCP_ECN_send(sk, tp, skb, tcp_header_size); 3541da177e4SLinus Torvalds } 3551da177e4SLinus Torvalds tp->af_specific->send_check(sk, th, skb->len, skb); 3561da177e4SLinus Torvalds 3571da177e4SLinus Torvalds if (tcb->flags & TCPCB_FLAG_ACK) 358fc6415bcSDavid S. Miller tcp_event_ack_sent(sk, tcp_skb_pcount(skb)); 3591da177e4SLinus Torvalds 3601da177e4SLinus Torvalds if (skb->len != tcp_header_size) 3611da177e4SLinus Torvalds tcp_event_data_sent(tp, skb, sk); 3621da177e4SLinus Torvalds 3631da177e4SLinus Torvalds TCP_INC_STATS(TCP_MIB_OUTSEGS); 3641da177e4SLinus Torvalds 3651da177e4SLinus Torvalds err = tp->af_specific->queue_xmit(skb, 0); 3661da177e4SLinus Torvalds if (err <= 0) 3671da177e4SLinus Torvalds return err; 3681da177e4SLinus Torvalds 3691da177e4SLinus Torvalds tcp_enter_cwr(tp); 3701da177e4SLinus Torvalds 3711da177e4SLinus Torvalds /* NET_XMIT_CN is special. It does not guarantee, 3721da177e4SLinus Torvalds * that this packet is lost. It tells that device 3731da177e4SLinus Torvalds * is about to start to drop packets or already 3741da177e4SLinus Torvalds * drops some packets of the same priority and 3751da177e4SLinus Torvalds * invokes us to send less aggressively. 3761da177e4SLinus Torvalds */ 3771da177e4SLinus Torvalds return err == NET_XMIT_CN ? 0 : err; 3781da177e4SLinus Torvalds } 3791da177e4SLinus Torvalds return -ENOBUFS; 3801da177e4SLinus Torvalds #undef SYSCTL_FLAG_TSTAMPS 3811da177e4SLinus Torvalds #undef SYSCTL_FLAG_WSCALE 3821da177e4SLinus Torvalds #undef SYSCTL_FLAG_SACK 3831da177e4SLinus Torvalds } 3841da177e4SLinus Torvalds 3851da177e4SLinus Torvalds 3861da177e4SLinus Torvalds /* This routine just queue's the buffer 3871da177e4SLinus Torvalds * 3881da177e4SLinus Torvalds * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames, 3891da177e4SLinus Torvalds * otherwise socket can stall. 3901da177e4SLinus Torvalds */ 3911da177e4SLinus Torvalds static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) 3921da177e4SLinus Torvalds { 3931da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 3941da177e4SLinus Torvalds 3951da177e4SLinus Torvalds /* Advance write_seq and place onto the write_queue. */ 3961da177e4SLinus Torvalds tp->write_seq = TCP_SKB_CB(skb)->end_seq; 3971da177e4SLinus Torvalds skb_header_release(skb); 3981da177e4SLinus Torvalds __skb_queue_tail(&sk->sk_write_queue, skb); 3991da177e4SLinus Torvalds sk_charge_skb(sk, skb); 4001da177e4SLinus Torvalds 4011da177e4SLinus Torvalds /* Queue it, remembering where we must start sending. */ 4021da177e4SLinus Torvalds if (sk->sk_send_head == NULL) 4031da177e4SLinus Torvalds sk->sk_send_head = skb; 4041da177e4SLinus Torvalds } 4051da177e4SLinus Torvalds 4061da177e4SLinus Torvalds static inline void tcp_tso_set_push(struct sk_buff *skb) 4071da177e4SLinus Torvalds { 4081da177e4SLinus Torvalds /* Force push to be on for any TSO frames to workaround 4091da177e4SLinus Torvalds * problems with busted implementations like Mac OS-X that 4101da177e4SLinus Torvalds * hold off socket receive wakeups until push is seen. 4111da177e4SLinus Torvalds */ 4121da177e4SLinus Torvalds if (tcp_skb_pcount(skb) > 1) 4131da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; 4141da177e4SLinus Torvalds } 4151da177e4SLinus Torvalds 416f6302d1dSDavid S. Miller static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb) 417f6302d1dSDavid S. Miller { 418f6302d1dSDavid S. Miller struct tcp_sock *tp = tcp_sk(sk); 419f6302d1dSDavid S. Miller 420f6302d1dSDavid S. Miller if (skb->len <= tp->mss_cache_std || 421f6302d1dSDavid S. Miller !(sk->sk_route_caps & NETIF_F_TSO)) { 422f6302d1dSDavid S. Miller /* Avoid the costly divide in the normal 423f6302d1dSDavid S. Miller * non-TSO case. 424f6302d1dSDavid S. Miller */ 425f6302d1dSDavid S. Miller skb_shinfo(skb)->tso_segs = 1; 426f6302d1dSDavid S. Miller skb_shinfo(skb)->tso_size = 0; 427f6302d1dSDavid S. Miller } else { 428f6302d1dSDavid S. Miller unsigned int factor; 429f6302d1dSDavid S. Miller 430f6302d1dSDavid S. Miller factor = skb->len + (tp->mss_cache_std - 1); 431f6302d1dSDavid S. Miller factor /= tp->mss_cache_std; 432f6302d1dSDavid S. Miller skb_shinfo(skb)->tso_segs = factor; 433f6302d1dSDavid S. Miller skb_shinfo(skb)->tso_size = tp->mss_cache_std; 434f6302d1dSDavid S. Miller } 435f6302d1dSDavid S. Miller } 436f6302d1dSDavid S. Miller 437f6302d1dSDavid S. Miller static inline int tcp_minshall_check(const struct tcp_sock *tp) 438f6302d1dSDavid S. Miller { 439f6302d1dSDavid S. Miller return after(tp->snd_sml,tp->snd_una) && 440f6302d1dSDavid S. Miller !after(tp->snd_sml, tp->snd_nxt); 441f6302d1dSDavid S. Miller } 442f6302d1dSDavid S. Miller 443f6302d1dSDavid S. Miller /* Return 0, if packet can be sent now without violation Nagle's rules: 444f6302d1dSDavid S. Miller * 1. It is full sized. 445f6302d1dSDavid S. Miller * 2. Or it contains FIN. 446f6302d1dSDavid S. Miller * 3. Or TCP_NODELAY was set. 447f6302d1dSDavid S. Miller * 4. Or TCP_CORK is not set, and all sent packets are ACKed. 448f6302d1dSDavid S. Miller * With Minshall's modification: all sent small packets are ACKed. 449f6302d1dSDavid S. Miller */ 450f6302d1dSDavid S. Miller 451f6302d1dSDavid S. Miller static inline int tcp_nagle_check(const struct tcp_sock *tp, 452f6302d1dSDavid S. Miller const struct sk_buff *skb, 453f6302d1dSDavid S. Miller unsigned mss_now, int nonagle) 454f6302d1dSDavid S. Miller { 455f6302d1dSDavid S. Miller return (skb->len < mss_now && 456f6302d1dSDavid S. Miller !(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) && 457f6302d1dSDavid S. Miller ((nonagle&TCP_NAGLE_CORK) || 458f6302d1dSDavid S. Miller (!nonagle && 459f6302d1dSDavid S. Miller tp->packets_out && 460f6302d1dSDavid S. Miller tcp_minshall_check(tp)))); 461f6302d1dSDavid S. Miller } 462f6302d1dSDavid S. Miller 463f6302d1dSDavid S. Miller /* This checks if the data bearing packet SKB (usually sk->sk_send_head) 464f6302d1dSDavid S. Miller * should be put on the wire right now. 465f6302d1dSDavid S. Miller */ 466f6302d1dSDavid S. Miller static int tcp_snd_test(struct sock *sk, struct sk_buff *skb, 467f6302d1dSDavid S. Miller unsigned cur_mss, int nonagle) 468f6302d1dSDavid S. Miller { 469f6302d1dSDavid S. Miller struct tcp_sock *tp = tcp_sk(sk); 470f6302d1dSDavid S. Miller int pkts = tcp_skb_pcount(skb); 471f6302d1dSDavid S. Miller 472f6302d1dSDavid S. Miller if (!pkts) { 473f6302d1dSDavid S. Miller tcp_set_skb_tso_segs(sk, skb); 474f6302d1dSDavid S. Miller pkts = tcp_skb_pcount(skb); 475f6302d1dSDavid S. Miller } 476f6302d1dSDavid S. Miller 477f6302d1dSDavid S. Miller /* RFC 1122 - section 4.2.3.4 478f6302d1dSDavid S. Miller * 479f6302d1dSDavid S. Miller * We must queue if 480f6302d1dSDavid S. Miller * 481f6302d1dSDavid S. Miller * a) The right edge of this frame exceeds the window 482f6302d1dSDavid S. Miller * b) There are packets in flight and we have a small segment 483f6302d1dSDavid S. Miller * [SWS avoidance and Nagle algorithm] 484f6302d1dSDavid S. Miller * (part of SWS is done on packetization) 485f6302d1dSDavid S. Miller * Minshall version sounds: there are no _small_ 486f6302d1dSDavid S. Miller * segments in flight. (tcp_nagle_check) 487f6302d1dSDavid S. Miller * c) We have too many packets 'in flight' 488f6302d1dSDavid S. Miller * 489f6302d1dSDavid S. Miller * Don't use the nagle rule for urgent data (or 490f6302d1dSDavid S. Miller * for the final FIN -DaveM). 491f6302d1dSDavid S. Miller * 492f6302d1dSDavid S. Miller * Also, Nagle rule does not apply to frames, which 493f6302d1dSDavid S. Miller * sit in the middle of queue (they have no chances 494f6302d1dSDavid S. Miller * to get new data) and if room at tail of skb is 495f6302d1dSDavid S. Miller * not enough to save something seriously (<32 for now). 496f6302d1dSDavid S. Miller */ 497f6302d1dSDavid S. Miller 498f6302d1dSDavid S. Miller /* Don't be strict about the congestion window for the 499f6302d1dSDavid S. Miller * final FIN frame. -DaveM 500f6302d1dSDavid S. Miller */ 501f6302d1dSDavid S. Miller return (((nonagle&TCP_NAGLE_PUSH) || tp->urg_mode 502f6302d1dSDavid S. Miller || !tcp_nagle_check(tp, skb, cur_mss, nonagle)) && 503f6302d1dSDavid S. Miller (((tcp_packets_in_flight(tp) + (pkts-1)) < tp->snd_cwnd) || 504f6302d1dSDavid S. Miller (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)) && 505f6302d1dSDavid S. Miller !after(TCP_SKB_CB(skb)->end_seq, tp->snd_una + tp->snd_wnd)); 506f6302d1dSDavid S. Miller } 507f6302d1dSDavid S. Miller 508f6302d1dSDavid S. Miller static inline int tcp_skb_is_last(const struct sock *sk, 509f6302d1dSDavid S. Miller const struct sk_buff *skb) 510f6302d1dSDavid S. Miller { 511f6302d1dSDavid S. Miller return skb->next == (struct sk_buff *)&sk->sk_write_queue; 512f6302d1dSDavid S. Miller } 513f6302d1dSDavid S. Miller 514f6302d1dSDavid S. Miller int tcp_may_send_now(struct sock *sk, struct tcp_sock *tp) 515f6302d1dSDavid S. Miller { 516f6302d1dSDavid S. Miller struct sk_buff *skb = sk->sk_send_head; 517f6302d1dSDavid S. Miller 518f6302d1dSDavid S. Miller return (skb && 519f6302d1dSDavid S. Miller tcp_snd_test(sk, skb, tcp_current_mss(sk, 1), 520f6302d1dSDavid S. Miller (tcp_skb_is_last(sk, skb) ? 521f6302d1dSDavid S. Miller TCP_NAGLE_PUSH : 522f6302d1dSDavid S. Miller tp->nonagle))); 523f6302d1dSDavid S. Miller } 524f6302d1dSDavid S. Miller 525f6302d1dSDavid S. Miller 5261da177e4SLinus Torvalds /* Send _single_ skb sitting at the send head. This function requires 5271da177e4SLinus Torvalds * true push pending frames to setup probe timer etc. 5281da177e4SLinus Torvalds */ 5291da177e4SLinus Torvalds void tcp_push_one(struct sock *sk, unsigned cur_mss) 5301da177e4SLinus Torvalds { 5311da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 5321da177e4SLinus Torvalds struct sk_buff *skb = sk->sk_send_head; 5331da177e4SLinus Torvalds 534d5ac99a6SDavid S. Miller if (tcp_snd_test(sk, skb, cur_mss, TCP_NAGLE_PUSH)) { 5351da177e4SLinus Torvalds /* Send it out now. */ 5361da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 5371da177e4SLinus Torvalds tcp_tso_set_push(skb); 5381da177e4SLinus Torvalds if (!tcp_transmit_skb(sk, skb_clone(skb, sk->sk_allocation))) { 5391da177e4SLinus Torvalds sk->sk_send_head = NULL; 5401da177e4SLinus Torvalds tp->snd_nxt = TCP_SKB_CB(skb)->end_seq; 5411da177e4SLinus Torvalds tcp_packets_out_inc(sk, tp, skb); 5421da177e4SLinus Torvalds return; 5431da177e4SLinus Torvalds } 5441da177e4SLinus Torvalds } 5451da177e4SLinus Torvalds } 5461da177e4SLinus Torvalds 5471da177e4SLinus Torvalds /* Function to create two new TCP segments. Shrinks the given segment 5481da177e4SLinus Torvalds * to the specified size and appends a new segment with the rest of the 5491da177e4SLinus Torvalds * packet to the list. This won't be called frequently, I hope. 5501da177e4SLinus Torvalds * Remember, these are still headerless SKBs at this point. 5511da177e4SLinus Torvalds */ 5521da177e4SLinus Torvalds static int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len) 5531da177e4SLinus Torvalds { 5541da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 5551da177e4SLinus Torvalds struct sk_buff *buff; 5561da177e4SLinus Torvalds int nsize; 5571da177e4SLinus Torvalds u16 flags; 5581da177e4SLinus Torvalds 5591da177e4SLinus Torvalds nsize = skb_headlen(skb) - len; 5601da177e4SLinus Torvalds if (nsize < 0) 5611da177e4SLinus Torvalds nsize = 0; 5621da177e4SLinus Torvalds 5631da177e4SLinus Torvalds if (skb_cloned(skb) && 5641da177e4SLinus Torvalds skb_is_nonlinear(skb) && 5651da177e4SLinus Torvalds pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) 5661da177e4SLinus Torvalds return -ENOMEM; 5671da177e4SLinus Torvalds 5681da177e4SLinus Torvalds /* Get a new skb... force flag on. */ 5691da177e4SLinus Torvalds buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC); 5701da177e4SLinus Torvalds if (buff == NULL) 5711da177e4SLinus Torvalds return -ENOMEM; /* We'll just try again later. */ 5721da177e4SLinus Torvalds sk_charge_skb(sk, buff); 5731da177e4SLinus Torvalds 5741da177e4SLinus Torvalds /* Correct the sequence numbers. */ 5751da177e4SLinus Torvalds TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; 5761da177e4SLinus Torvalds TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; 5771da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; 5781da177e4SLinus Torvalds 5791da177e4SLinus Torvalds /* PSH and FIN should only be set in the second packet. */ 5801da177e4SLinus Torvalds flags = TCP_SKB_CB(skb)->flags; 5811da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH); 5821da177e4SLinus Torvalds TCP_SKB_CB(buff)->flags = flags; 5831da177e4SLinus Torvalds TCP_SKB_CB(buff)->sacked = 5841da177e4SLinus Torvalds (TCP_SKB_CB(skb)->sacked & 5851da177e4SLinus Torvalds (TCPCB_LOST | TCPCB_EVER_RETRANS | TCPCB_AT_TAIL)); 5861da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked &= ~TCPCB_AT_TAIL; 5871da177e4SLinus Torvalds 5881da177e4SLinus Torvalds if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_HW) { 5891da177e4SLinus Torvalds /* Copy and checksum data tail into the new buffer. */ 5901da177e4SLinus Torvalds buff->csum = csum_partial_copy_nocheck(skb->data + len, skb_put(buff, nsize), 5911da177e4SLinus Torvalds nsize, 0); 5921da177e4SLinus Torvalds 5931da177e4SLinus Torvalds skb_trim(skb, len); 5941da177e4SLinus Torvalds 5951da177e4SLinus Torvalds skb->csum = csum_block_sub(skb->csum, buff->csum, len); 5961da177e4SLinus Torvalds } else { 5971da177e4SLinus Torvalds skb->ip_summed = CHECKSUM_HW; 5981da177e4SLinus Torvalds skb_split(skb, buff, len); 5991da177e4SLinus Torvalds } 6001da177e4SLinus Torvalds 6011da177e4SLinus Torvalds buff->ip_summed = skb->ip_summed; 6021da177e4SLinus Torvalds 6031da177e4SLinus Torvalds /* Looks stupid, but our code really uses when of 6041da177e4SLinus Torvalds * skbs, which it never sent before. --ANK 6051da177e4SLinus Torvalds */ 6061da177e4SLinus Torvalds TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when; 607317a76f9SStephen Hemminger buff->stamp = skb->stamp; 6081da177e4SLinus Torvalds 6091da177e4SLinus Torvalds if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) { 6101da177e4SLinus Torvalds tp->lost_out -= tcp_skb_pcount(skb); 6111da177e4SLinus Torvalds tp->left_out -= tcp_skb_pcount(skb); 6121da177e4SLinus Torvalds } 6131da177e4SLinus Torvalds 6141da177e4SLinus Torvalds /* Fix up tso_factor for both original and new SKB. */ 615d5ac99a6SDavid S. Miller tcp_set_skb_tso_segs(sk, skb); 616d5ac99a6SDavid S. Miller tcp_set_skb_tso_segs(sk, buff); 6171da177e4SLinus Torvalds 6181da177e4SLinus Torvalds if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) { 6191da177e4SLinus Torvalds tp->lost_out += tcp_skb_pcount(skb); 6201da177e4SLinus Torvalds tp->left_out += tcp_skb_pcount(skb); 6211da177e4SLinus Torvalds } 6221da177e4SLinus Torvalds 6231da177e4SLinus Torvalds if (TCP_SKB_CB(buff)->sacked&TCPCB_LOST) { 6241da177e4SLinus Torvalds tp->lost_out += tcp_skb_pcount(buff); 6251da177e4SLinus Torvalds tp->left_out += tcp_skb_pcount(buff); 6261da177e4SLinus Torvalds } 6271da177e4SLinus Torvalds 6281da177e4SLinus Torvalds /* Link BUFF into the send queue. */ 629f44b5271SDavid S. Miller skb_header_release(buff); 6301da177e4SLinus Torvalds __skb_append(skb, buff); 6311da177e4SLinus Torvalds 6321da177e4SLinus Torvalds return 0; 6331da177e4SLinus Torvalds } 6341da177e4SLinus Torvalds 6351da177e4SLinus Torvalds /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c 6361da177e4SLinus Torvalds * eventually). The difference is that pulled data not copied, but 6371da177e4SLinus Torvalds * immediately discarded. 6381da177e4SLinus Torvalds */ 6391da177e4SLinus Torvalds static unsigned char *__pskb_trim_head(struct sk_buff *skb, int len) 6401da177e4SLinus Torvalds { 6411da177e4SLinus Torvalds int i, k, eat; 6421da177e4SLinus Torvalds 6431da177e4SLinus Torvalds eat = len; 6441da177e4SLinus Torvalds k = 0; 6451da177e4SLinus Torvalds for (i=0; i<skb_shinfo(skb)->nr_frags; i++) { 6461da177e4SLinus Torvalds if (skb_shinfo(skb)->frags[i].size <= eat) { 6471da177e4SLinus Torvalds put_page(skb_shinfo(skb)->frags[i].page); 6481da177e4SLinus Torvalds eat -= skb_shinfo(skb)->frags[i].size; 6491da177e4SLinus Torvalds } else { 6501da177e4SLinus Torvalds skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i]; 6511da177e4SLinus Torvalds if (eat) { 6521da177e4SLinus Torvalds skb_shinfo(skb)->frags[k].page_offset += eat; 6531da177e4SLinus Torvalds skb_shinfo(skb)->frags[k].size -= eat; 6541da177e4SLinus Torvalds eat = 0; 6551da177e4SLinus Torvalds } 6561da177e4SLinus Torvalds k++; 6571da177e4SLinus Torvalds } 6581da177e4SLinus Torvalds } 6591da177e4SLinus Torvalds skb_shinfo(skb)->nr_frags = k; 6601da177e4SLinus Torvalds 6611da177e4SLinus Torvalds skb->tail = skb->data; 6621da177e4SLinus Torvalds skb->data_len -= len; 6631da177e4SLinus Torvalds skb->len = skb->data_len; 6641da177e4SLinus Torvalds return skb->tail; 6651da177e4SLinus Torvalds } 6661da177e4SLinus Torvalds 6671da177e4SLinus Torvalds int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) 6681da177e4SLinus Torvalds { 6691da177e4SLinus Torvalds if (skb_cloned(skb) && 6701da177e4SLinus Torvalds pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) 6711da177e4SLinus Torvalds return -ENOMEM; 6721da177e4SLinus Torvalds 6731da177e4SLinus Torvalds if (len <= skb_headlen(skb)) { 6741da177e4SLinus Torvalds __skb_pull(skb, len); 6751da177e4SLinus Torvalds } else { 6761da177e4SLinus Torvalds if (__pskb_trim_head(skb, len-skb_headlen(skb)) == NULL) 6771da177e4SLinus Torvalds return -ENOMEM; 6781da177e4SLinus Torvalds } 6791da177e4SLinus Torvalds 6801da177e4SLinus Torvalds TCP_SKB_CB(skb)->seq += len; 6811da177e4SLinus Torvalds skb->ip_summed = CHECKSUM_HW; 6821da177e4SLinus Torvalds 6831da177e4SLinus Torvalds skb->truesize -= len; 6841da177e4SLinus Torvalds sk->sk_wmem_queued -= len; 6851da177e4SLinus Torvalds sk->sk_forward_alloc += len; 6861da177e4SLinus Torvalds sock_set_flag(sk, SOCK_QUEUE_SHRUNK); 6871da177e4SLinus Torvalds 6881da177e4SLinus Torvalds /* Any change of skb->len requires recalculation of tso 6891da177e4SLinus Torvalds * factor and mss. 6901da177e4SLinus Torvalds */ 6911da177e4SLinus Torvalds if (tcp_skb_pcount(skb) > 1) 692d5ac99a6SDavid S. Miller tcp_set_skb_tso_segs(sk, skb); 6931da177e4SLinus Torvalds 6941da177e4SLinus Torvalds return 0; 6951da177e4SLinus Torvalds } 6961da177e4SLinus Torvalds 6971da177e4SLinus Torvalds /* This function synchronize snd mss to current pmtu/exthdr set. 6981da177e4SLinus Torvalds 6991da177e4SLinus Torvalds tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts 7001da177e4SLinus Torvalds for TCP options, but includes only bare TCP header. 7011da177e4SLinus Torvalds 7021da177e4SLinus Torvalds tp->rx_opt.mss_clamp is mss negotiated at connection setup. 7031da177e4SLinus Torvalds It is minumum of user_mss and mss received with SYN. 7041da177e4SLinus Torvalds It also does not include TCP options. 7051da177e4SLinus Torvalds 7061da177e4SLinus Torvalds tp->pmtu_cookie is last pmtu, seen by this function. 7071da177e4SLinus Torvalds 7081da177e4SLinus Torvalds tp->mss_cache is current effective sending mss, including 7091da177e4SLinus Torvalds all tcp options except for SACKs. It is evaluated, 7101da177e4SLinus Torvalds taking into account current pmtu, but never exceeds 7111da177e4SLinus Torvalds tp->rx_opt.mss_clamp. 7121da177e4SLinus Torvalds 7131da177e4SLinus Torvalds NOTE1. rfc1122 clearly states that advertised MSS 7141da177e4SLinus Torvalds DOES NOT include either tcp or ip options. 7151da177e4SLinus Torvalds 7161da177e4SLinus Torvalds NOTE2. tp->pmtu_cookie and tp->mss_cache are READ ONLY outside 7171da177e4SLinus Torvalds this function. --ANK (980731) 7181da177e4SLinus Torvalds */ 7191da177e4SLinus Torvalds 7201da177e4SLinus Torvalds unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu) 7211da177e4SLinus Torvalds { 7221da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 7231da177e4SLinus Torvalds int mss_now; 7241da177e4SLinus Torvalds 7251da177e4SLinus Torvalds /* Calculate base mss without TCP options: 7261da177e4SLinus Torvalds It is MMS_S - sizeof(tcphdr) of rfc1122 7271da177e4SLinus Torvalds */ 7281da177e4SLinus Torvalds mss_now = pmtu - tp->af_specific->net_header_len - sizeof(struct tcphdr); 7291da177e4SLinus Torvalds 7301da177e4SLinus Torvalds /* Clamp it (mss_clamp does not include tcp options) */ 7311da177e4SLinus Torvalds if (mss_now > tp->rx_opt.mss_clamp) 7321da177e4SLinus Torvalds mss_now = tp->rx_opt.mss_clamp; 7331da177e4SLinus Torvalds 7341da177e4SLinus Torvalds /* Now subtract optional transport overhead */ 7351da177e4SLinus Torvalds mss_now -= tp->ext_header_len; 7361da177e4SLinus Torvalds 7371da177e4SLinus Torvalds /* Then reserve room for full set of TCP options and 8 bytes of data */ 7381da177e4SLinus Torvalds if (mss_now < 48) 7391da177e4SLinus Torvalds mss_now = 48; 7401da177e4SLinus Torvalds 7411da177e4SLinus Torvalds /* Now subtract TCP options size, not including SACKs */ 7421da177e4SLinus Torvalds mss_now -= tp->tcp_header_len - sizeof(struct tcphdr); 7431da177e4SLinus Torvalds 7441da177e4SLinus Torvalds /* Bound mss with half of window */ 7451da177e4SLinus Torvalds if (tp->max_window && mss_now > (tp->max_window>>1)) 7461da177e4SLinus Torvalds mss_now = max((tp->max_window>>1), 68U - tp->tcp_header_len); 7471da177e4SLinus Torvalds 7481da177e4SLinus Torvalds /* And store cached results */ 7491da177e4SLinus Torvalds tp->pmtu_cookie = pmtu; 7501da177e4SLinus Torvalds tp->mss_cache = tp->mss_cache_std = mss_now; 7511da177e4SLinus Torvalds 7521da177e4SLinus Torvalds return mss_now; 7531da177e4SLinus Torvalds } 7541da177e4SLinus Torvalds 7551da177e4SLinus Torvalds /* Compute the current effective MSS, taking SACKs and IP options, 7561da177e4SLinus Torvalds * and even PMTU discovery events into account. 7571da177e4SLinus Torvalds * 7581da177e4SLinus Torvalds * LARGESEND note: !urg_mode is overkill, only frames up to snd_up 7591da177e4SLinus Torvalds * cannot be large. However, taking into account rare use of URG, this 7601da177e4SLinus Torvalds * is not a big flaw. 7611da177e4SLinus Torvalds */ 7621da177e4SLinus Torvalds 7631da177e4SLinus Torvalds unsigned int tcp_current_mss(struct sock *sk, int large) 7641da177e4SLinus Torvalds { 7651da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 7661da177e4SLinus Torvalds struct dst_entry *dst = __sk_dst_get(sk); 7671da177e4SLinus Torvalds unsigned int do_large, mss_now; 7681da177e4SLinus Torvalds 7691da177e4SLinus Torvalds mss_now = tp->mss_cache_std; 7701da177e4SLinus Torvalds if (dst) { 7711da177e4SLinus Torvalds u32 mtu = dst_mtu(dst); 7721da177e4SLinus Torvalds if (mtu != tp->pmtu_cookie) 7731da177e4SLinus Torvalds mss_now = tcp_sync_mss(sk, mtu); 7741da177e4SLinus Torvalds } 7751da177e4SLinus Torvalds 7761da177e4SLinus Torvalds do_large = (large && 7771da177e4SLinus Torvalds (sk->sk_route_caps & NETIF_F_TSO) && 7781da177e4SLinus Torvalds !tp->urg_mode); 7791da177e4SLinus Torvalds 7801da177e4SLinus Torvalds if (do_large) { 7811da177e4SLinus Torvalds unsigned int large_mss, factor, limit; 7821da177e4SLinus Torvalds 7831da177e4SLinus Torvalds large_mss = 65535 - tp->af_specific->net_header_len - 7841da177e4SLinus Torvalds tp->ext_header_len - tp->tcp_header_len; 7851da177e4SLinus Torvalds 7861da177e4SLinus Torvalds if (tp->max_window && large_mss > (tp->max_window>>1)) 7871da177e4SLinus Torvalds large_mss = max((tp->max_window>>1), 7881da177e4SLinus Torvalds 68U - tp->tcp_header_len); 7891da177e4SLinus Torvalds 7901da177e4SLinus Torvalds factor = large_mss / mss_now; 7911da177e4SLinus Torvalds 7921da177e4SLinus Torvalds /* Always keep large mss multiple of real mss, but 7931da177e4SLinus Torvalds * do not exceed 1/tso_win_divisor of the congestion window 7941da177e4SLinus Torvalds * so we can keep the ACK clock ticking and minimize 7951da177e4SLinus Torvalds * bursting. 7961da177e4SLinus Torvalds */ 7971da177e4SLinus Torvalds limit = tp->snd_cwnd; 7981da177e4SLinus Torvalds if (sysctl_tcp_tso_win_divisor) 7991da177e4SLinus Torvalds limit /= sysctl_tcp_tso_win_divisor; 8001da177e4SLinus Torvalds limit = max(1U, limit); 8011da177e4SLinus Torvalds if (factor > limit) 8021da177e4SLinus Torvalds factor = limit; 8031da177e4SLinus Torvalds 8041da177e4SLinus Torvalds tp->mss_cache = mss_now * factor; 8051da177e4SLinus Torvalds 8061da177e4SLinus Torvalds mss_now = tp->mss_cache; 8071da177e4SLinus Torvalds } 8081da177e4SLinus Torvalds 8091da177e4SLinus Torvalds if (tp->rx_opt.eff_sacks) 8101da177e4SLinus Torvalds mss_now -= (TCPOLEN_SACK_BASE_ALIGNED + 8111da177e4SLinus Torvalds (tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK)); 8121da177e4SLinus Torvalds return mss_now; 8131da177e4SLinus Torvalds } 8141da177e4SLinus Torvalds 815a762a980SDavid S. Miller /* Congestion window validation. (RFC2861) */ 816a762a980SDavid S. Miller 817a762a980SDavid S. Miller static inline void tcp_cwnd_validate(struct sock *sk, struct tcp_sock *tp) 818a762a980SDavid S. Miller { 819a762a980SDavid S. Miller __u32 packets_out = tp->packets_out; 820a762a980SDavid S. Miller 821a762a980SDavid S. Miller if (packets_out >= tp->snd_cwnd) { 822a762a980SDavid S. Miller /* Network is feed fully. */ 823a762a980SDavid S. Miller tp->snd_cwnd_used = 0; 824a762a980SDavid S. Miller tp->snd_cwnd_stamp = tcp_time_stamp; 825a762a980SDavid S. Miller } else { 826a762a980SDavid S. Miller /* Network starves. */ 827a762a980SDavid S. Miller if (tp->packets_out > tp->snd_cwnd_used) 828a762a980SDavid S. Miller tp->snd_cwnd_used = tp->packets_out; 829a762a980SDavid S. Miller 830a762a980SDavid S. Miller if ((s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= tp->rto) 831a762a980SDavid S. Miller tcp_cwnd_application_limited(sk); 832a762a980SDavid S. Miller } 833a762a980SDavid S. Miller } 834a762a980SDavid S. Miller 8351da177e4SLinus Torvalds /* This routine writes packets to the network. It advances the 8361da177e4SLinus Torvalds * send_head. This happens as incoming acks open up the remote 8371da177e4SLinus Torvalds * window for us. 8381da177e4SLinus Torvalds * 8391da177e4SLinus Torvalds * Returns 1, if no segments are in flight and we have queued segments, but 8401da177e4SLinus Torvalds * cannot send anything now because of SWS or another problem. 8411da177e4SLinus Torvalds */ 842a762a980SDavid S. Miller static int tcp_write_xmit(struct sock *sk, int nonagle) 8431da177e4SLinus Torvalds { 8441da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 845*92df7b51SDavid S. Miller struct sk_buff *skb; 8461da177e4SLinus Torvalds unsigned int mss_now; 847*92df7b51SDavid S. Miller int sent_pkts; 8481da177e4SLinus Torvalds 8491da177e4SLinus Torvalds /* If we are closed, the bytes will have to remain here. 8501da177e4SLinus Torvalds * In time closedown will finish, we empty the write queue and all 8511da177e4SLinus Torvalds * will be happy. 8521da177e4SLinus Torvalds */ 853*92df7b51SDavid S. Miller if (unlikely(sk->sk_state == TCP_CLOSE)) 854*92df7b51SDavid S. Miller return 0; 855*92df7b51SDavid S. Miller 8561da177e4SLinus Torvalds 8571da177e4SLinus Torvalds /* Account for SACKS, we may need to fragment due to this. 8581da177e4SLinus Torvalds * It is just like the real MSS changing on us midstream. 8591da177e4SLinus Torvalds * We also handle things correctly when the user adds some 8601da177e4SLinus Torvalds * IP options mid-stream. Silly to do, but cover it. 8611da177e4SLinus Torvalds */ 8621da177e4SLinus Torvalds mss_now = tcp_current_mss(sk, 1); 863*92df7b51SDavid S. Miller sent_pkts = 0; 8641da177e4SLinus Torvalds while ((skb = sk->sk_send_head) && 865d5ac99a6SDavid S. Miller tcp_snd_test(sk, skb, mss_now, 8661da177e4SLinus Torvalds tcp_skb_is_last(sk, skb) ? nonagle : 8671da177e4SLinus Torvalds TCP_NAGLE_PUSH)) { 8681da177e4SLinus Torvalds if (skb->len > mss_now) { 8691da177e4SLinus Torvalds if (tcp_fragment(sk, skb, mss_now)) 8701da177e4SLinus Torvalds break; 8711da177e4SLinus Torvalds } 8721da177e4SLinus Torvalds 8731da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 8741da177e4SLinus Torvalds tcp_tso_set_push(skb); 8751da177e4SLinus Torvalds if (tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC))) 8761da177e4SLinus Torvalds break; 8771da177e4SLinus Torvalds 8781da177e4SLinus Torvalds /* Advance the send_head. This one is sent out. 8791da177e4SLinus Torvalds * This call will increment packets_out. 8801da177e4SLinus Torvalds */ 8811da177e4SLinus Torvalds update_send_head(sk, tp, skb); 8821da177e4SLinus Torvalds 8831da177e4SLinus Torvalds tcp_minshall_update(tp, mss_now, skb); 8841da177e4SLinus Torvalds sent_pkts = 1; 8851da177e4SLinus Torvalds } 8861da177e4SLinus Torvalds 8871da177e4SLinus Torvalds if (sent_pkts) { 8881da177e4SLinus Torvalds tcp_cwnd_validate(sk, tp); 8891da177e4SLinus Torvalds return 0; 8901da177e4SLinus Torvalds } 8911da177e4SLinus Torvalds 8921da177e4SLinus Torvalds return !tp->packets_out && sk->sk_send_head; 8931da177e4SLinus Torvalds } 8941da177e4SLinus Torvalds 895a762a980SDavid S. Miller /* Push out any pending frames which were held back due to 896a762a980SDavid S. Miller * TCP_CORK or attempt at coalescing tiny packets. 897a762a980SDavid S. Miller * The socket must be locked by the caller. 898a762a980SDavid S. Miller */ 899a762a980SDavid S. Miller void __tcp_push_pending_frames(struct sock *sk, struct tcp_sock *tp, 900a762a980SDavid S. Miller unsigned cur_mss, int nonagle) 901a762a980SDavid S. Miller { 902a762a980SDavid S. Miller struct sk_buff *skb = sk->sk_send_head; 903a762a980SDavid S. Miller 904a762a980SDavid S. Miller if (skb) { 905a762a980SDavid S. Miller if (!tcp_skb_is_last(sk, skb)) 906a762a980SDavid S. Miller nonagle = TCP_NAGLE_PUSH; 907a762a980SDavid S. Miller if (!tcp_snd_test(sk, skb, cur_mss, nonagle) || 908a762a980SDavid S. Miller tcp_write_xmit(sk, nonagle)) 909a762a980SDavid S. Miller tcp_check_probe_timer(sk, tp); 910a762a980SDavid S. Miller } 911a762a980SDavid S. Miller } 912a762a980SDavid S. Miller 913a762a980SDavid S. Miller void __tcp_data_snd_check(struct sock *sk, struct sk_buff *skb) 914a762a980SDavid S. Miller { 915a762a980SDavid S. Miller struct tcp_sock *tp = tcp_sk(sk); 916a762a980SDavid S. Miller 917a762a980SDavid S. Miller if (after(TCP_SKB_CB(skb)->end_seq, tp->snd_una + tp->snd_wnd) || 918a762a980SDavid S. Miller tcp_packets_in_flight(tp) >= tp->snd_cwnd || 919a762a980SDavid S. Miller tcp_write_xmit(sk, tp->nonagle)) 920a762a980SDavid S. Miller tcp_check_probe_timer(sk, tp); 921a762a980SDavid S. Miller } 922a762a980SDavid S. Miller 9231da177e4SLinus Torvalds /* This function returns the amount that we can raise the 9241da177e4SLinus Torvalds * usable window based on the following constraints 9251da177e4SLinus Torvalds * 9261da177e4SLinus Torvalds * 1. The window can never be shrunk once it is offered (RFC 793) 9271da177e4SLinus Torvalds * 2. We limit memory per socket 9281da177e4SLinus Torvalds * 9291da177e4SLinus Torvalds * RFC 1122: 9301da177e4SLinus Torvalds * "the suggested [SWS] avoidance algorithm for the receiver is to keep 9311da177e4SLinus Torvalds * RECV.NEXT + RCV.WIN fixed until: 9321da177e4SLinus Torvalds * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)" 9331da177e4SLinus Torvalds * 9341da177e4SLinus Torvalds * i.e. don't raise the right edge of the window until you can raise 9351da177e4SLinus Torvalds * it at least MSS bytes. 9361da177e4SLinus Torvalds * 9371da177e4SLinus Torvalds * Unfortunately, the recommended algorithm breaks header prediction, 9381da177e4SLinus Torvalds * since header prediction assumes th->window stays fixed. 9391da177e4SLinus Torvalds * 9401da177e4SLinus Torvalds * Strictly speaking, keeping th->window fixed violates the receiver 9411da177e4SLinus Torvalds * side SWS prevention criteria. The problem is that under this rule 9421da177e4SLinus Torvalds * a stream of single byte packets will cause the right side of the 9431da177e4SLinus Torvalds * window to always advance by a single byte. 9441da177e4SLinus Torvalds * 9451da177e4SLinus Torvalds * Of course, if the sender implements sender side SWS prevention 9461da177e4SLinus Torvalds * then this will not be a problem. 9471da177e4SLinus Torvalds * 9481da177e4SLinus Torvalds * BSD seems to make the following compromise: 9491da177e4SLinus Torvalds * 9501da177e4SLinus Torvalds * If the free space is less than the 1/4 of the maximum 9511da177e4SLinus Torvalds * space available and the free space is less than 1/2 mss, 9521da177e4SLinus Torvalds * then set the window to 0. 9531da177e4SLinus Torvalds * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ] 9541da177e4SLinus Torvalds * Otherwise, just prevent the window from shrinking 9551da177e4SLinus Torvalds * and from being larger than the largest representable value. 9561da177e4SLinus Torvalds * 9571da177e4SLinus Torvalds * This prevents incremental opening of the window in the regime 9581da177e4SLinus Torvalds * where TCP is limited by the speed of the reader side taking 9591da177e4SLinus Torvalds * data out of the TCP receive queue. It does nothing about 9601da177e4SLinus Torvalds * those cases where the window is constrained on the sender side 9611da177e4SLinus Torvalds * because the pipeline is full. 9621da177e4SLinus Torvalds * 9631da177e4SLinus Torvalds * BSD also seems to "accidentally" limit itself to windows that are a 9641da177e4SLinus Torvalds * multiple of MSS, at least until the free space gets quite small. 9651da177e4SLinus Torvalds * This would appear to be a side effect of the mbuf implementation. 9661da177e4SLinus Torvalds * Combining these two algorithms results in the observed behavior 9671da177e4SLinus Torvalds * of having a fixed window size at almost all times. 9681da177e4SLinus Torvalds * 9691da177e4SLinus Torvalds * Below we obtain similar behavior by forcing the offered window to 9701da177e4SLinus Torvalds * a multiple of the mss when it is feasible to do so. 9711da177e4SLinus Torvalds * 9721da177e4SLinus Torvalds * Note, we don't "adjust" for TIMESTAMP or SACK option bytes. 9731da177e4SLinus Torvalds * Regular options like TIMESTAMP are taken into account. 9741da177e4SLinus Torvalds */ 9751da177e4SLinus Torvalds u32 __tcp_select_window(struct sock *sk) 9761da177e4SLinus Torvalds { 9771da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 9781da177e4SLinus Torvalds /* MSS for the peer's data. Previous verions used mss_clamp 9791da177e4SLinus Torvalds * here. I don't know if the value based on our guesses 9801da177e4SLinus Torvalds * of peer's MSS is better for the performance. It's more correct 9811da177e4SLinus Torvalds * but may be worse for the performance because of rcv_mss 9821da177e4SLinus Torvalds * fluctuations. --SAW 1998/11/1 9831da177e4SLinus Torvalds */ 9841da177e4SLinus Torvalds int mss = tp->ack.rcv_mss; 9851da177e4SLinus Torvalds int free_space = tcp_space(sk); 9861da177e4SLinus Torvalds int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk)); 9871da177e4SLinus Torvalds int window; 9881da177e4SLinus Torvalds 9891da177e4SLinus Torvalds if (mss > full_space) 9901da177e4SLinus Torvalds mss = full_space; 9911da177e4SLinus Torvalds 9921da177e4SLinus Torvalds if (free_space < full_space/2) { 9931da177e4SLinus Torvalds tp->ack.quick = 0; 9941da177e4SLinus Torvalds 9951da177e4SLinus Torvalds if (tcp_memory_pressure) 9961da177e4SLinus Torvalds tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U*tp->advmss); 9971da177e4SLinus Torvalds 9981da177e4SLinus Torvalds if (free_space < mss) 9991da177e4SLinus Torvalds return 0; 10001da177e4SLinus Torvalds } 10011da177e4SLinus Torvalds 10021da177e4SLinus Torvalds if (free_space > tp->rcv_ssthresh) 10031da177e4SLinus Torvalds free_space = tp->rcv_ssthresh; 10041da177e4SLinus Torvalds 10051da177e4SLinus Torvalds /* Don't do rounding if we are using window scaling, since the 10061da177e4SLinus Torvalds * scaled window will not line up with the MSS boundary anyway. 10071da177e4SLinus Torvalds */ 10081da177e4SLinus Torvalds window = tp->rcv_wnd; 10091da177e4SLinus Torvalds if (tp->rx_opt.rcv_wscale) { 10101da177e4SLinus Torvalds window = free_space; 10111da177e4SLinus Torvalds 10121da177e4SLinus Torvalds /* Advertise enough space so that it won't get scaled away. 10131da177e4SLinus Torvalds * Import case: prevent zero window announcement if 10141da177e4SLinus Torvalds * 1<<rcv_wscale > mss. 10151da177e4SLinus Torvalds */ 10161da177e4SLinus Torvalds if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window) 10171da177e4SLinus Torvalds window = (((window >> tp->rx_opt.rcv_wscale) + 1) 10181da177e4SLinus Torvalds << tp->rx_opt.rcv_wscale); 10191da177e4SLinus Torvalds } else { 10201da177e4SLinus Torvalds /* Get the largest window that is a nice multiple of mss. 10211da177e4SLinus Torvalds * Window clamp already applied above. 10221da177e4SLinus Torvalds * If our current window offering is within 1 mss of the 10231da177e4SLinus Torvalds * free space we just keep it. This prevents the divide 10241da177e4SLinus Torvalds * and multiply from happening most of the time. 10251da177e4SLinus Torvalds * We also don't do any window rounding when the free space 10261da177e4SLinus Torvalds * is too small. 10271da177e4SLinus Torvalds */ 10281da177e4SLinus Torvalds if (window <= free_space - mss || window > free_space) 10291da177e4SLinus Torvalds window = (free_space/mss)*mss; 10301da177e4SLinus Torvalds } 10311da177e4SLinus Torvalds 10321da177e4SLinus Torvalds return window; 10331da177e4SLinus Torvalds } 10341da177e4SLinus Torvalds 10351da177e4SLinus Torvalds /* Attempt to collapse two adjacent SKB's during retransmission. */ 10361da177e4SLinus Torvalds static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int mss_now) 10371da177e4SLinus Torvalds { 10381da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 10391da177e4SLinus Torvalds struct sk_buff *next_skb = skb->next; 10401da177e4SLinus Torvalds 10411da177e4SLinus Torvalds /* The first test we must make is that neither of these two 10421da177e4SLinus Torvalds * SKB's are still referenced by someone else. 10431da177e4SLinus Torvalds */ 10441da177e4SLinus Torvalds if (!skb_cloned(skb) && !skb_cloned(next_skb)) { 10451da177e4SLinus Torvalds int skb_size = skb->len, next_skb_size = next_skb->len; 10461da177e4SLinus Torvalds u16 flags = TCP_SKB_CB(skb)->flags; 10471da177e4SLinus Torvalds 10481da177e4SLinus Torvalds /* Also punt if next skb has been SACK'd. */ 10491da177e4SLinus Torvalds if(TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_ACKED) 10501da177e4SLinus Torvalds return; 10511da177e4SLinus Torvalds 10521da177e4SLinus Torvalds /* Next skb is out of window. */ 10531da177e4SLinus Torvalds if (after(TCP_SKB_CB(next_skb)->end_seq, tp->snd_una+tp->snd_wnd)) 10541da177e4SLinus Torvalds return; 10551da177e4SLinus Torvalds 10561da177e4SLinus Torvalds /* Punt if not enough space exists in the first SKB for 10571da177e4SLinus Torvalds * the data in the second, or the total combined payload 10581da177e4SLinus Torvalds * would exceed the MSS. 10591da177e4SLinus Torvalds */ 10601da177e4SLinus Torvalds if ((next_skb_size > skb_tailroom(skb)) || 10611da177e4SLinus Torvalds ((skb_size + next_skb_size) > mss_now)) 10621da177e4SLinus Torvalds return; 10631da177e4SLinus Torvalds 10641da177e4SLinus Torvalds BUG_ON(tcp_skb_pcount(skb) != 1 || 10651da177e4SLinus Torvalds tcp_skb_pcount(next_skb) != 1); 10661da177e4SLinus Torvalds 10671da177e4SLinus Torvalds /* Ok. We will be able to collapse the packet. */ 10681da177e4SLinus Torvalds __skb_unlink(next_skb, next_skb->list); 10691da177e4SLinus Torvalds 10701da177e4SLinus Torvalds memcpy(skb_put(skb, next_skb_size), next_skb->data, next_skb_size); 10711da177e4SLinus Torvalds 10721da177e4SLinus Torvalds if (next_skb->ip_summed == CHECKSUM_HW) 10731da177e4SLinus Torvalds skb->ip_summed = CHECKSUM_HW; 10741da177e4SLinus Torvalds 10751da177e4SLinus Torvalds if (skb->ip_summed != CHECKSUM_HW) 10761da177e4SLinus Torvalds skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size); 10771da177e4SLinus Torvalds 10781da177e4SLinus Torvalds /* Update sequence range on original skb. */ 10791da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq; 10801da177e4SLinus Torvalds 10811da177e4SLinus Torvalds /* Merge over control information. */ 10821da177e4SLinus Torvalds flags |= TCP_SKB_CB(next_skb)->flags; /* This moves PSH/FIN etc. over */ 10831da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags = flags; 10841da177e4SLinus Torvalds 10851da177e4SLinus Torvalds /* All done, get rid of second SKB and account for it so 10861da177e4SLinus Torvalds * packet counting does not break. 10871da177e4SLinus Torvalds */ 10881da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked&(TCPCB_EVER_RETRANS|TCPCB_AT_TAIL); 10891da177e4SLinus Torvalds if (TCP_SKB_CB(next_skb)->sacked&TCPCB_SACKED_RETRANS) 10901da177e4SLinus Torvalds tp->retrans_out -= tcp_skb_pcount(next_skb); 10911da177e4SLinus Torvalds if (TCP_SKB_CB(next_skb)->sacked&TCPCB_LOST) { 10921da177e4SLinus Torvalds tp->lost_out -= tcp_skb_pcount(next_skb); 10931da177e4SLinus Torvalds tp->left_out -= tcp_skb_pcount(next_skb); 10941da177e4SLinus Torvalds } 10951da177e4SLinus Torvalds /* Reno case is special. Sigh... */ 10961da177e4SLinus Torvalds if (!tp->rx_opt.sack_ok && tp->sacked_out) { 10971da177e4SLinus Torvalds tcp_dec_pcount_approx(&tp->sacked_out, next_skb); 10981da177e4SLinus Torvalds tp->left_out -= tcp_skb_pcount(next_skb); 10991da177e4SLinus Torvalds } 11001da177e4SLinus Torvalds 11011da177e4SLinus Torvalds /* Not quite right: it can be > snd.fack, but 11021da177e4SLinus Torvalds * it is better to underestimate fackets. 11031da177e4SLinus Torvalds */ 11041da177e4SLinus Torvalds tcp_dec_pcount_approx(&tp->fackets_out, next_skb); 11051da177e4SLinus Torvalds tcp_packets_out_dec(tp, next_skb); 11061da177e4SLinus Torvalds sk_stream_free_skb(sk, next_skb); 11071da177e4SLinus Torvalds } 11081da177e4SLinus Torvalds } 11091da177e4SLinus Torvalds 11101da177e4SLinus Torvalds /* Do a simple retransmit without using the backoff mechanisms in 11111da177e4SLinus Torvalds * tcp_timer. This is used for path mtu discovery. 11121da177e4SLinus Torvalds * The socket is already locked here. 11131da177e4SLinus Torvalds */ 11141da177e4SLinus Torvalds void tcp_simple_retransmit(struct sock *sk) 11151da177e4SLinus Torvalds { 11161da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 11171da177e4SLinus Torvalds struct sk_buff *skb; 11181da177e4SLinus Torvalds unsigned int mss = tcp_current_mss(sk, 0); 11191da177e4SLinus Torvalds int lost = 0; 11201da177e4SLinus Torvalds 11211da177e4SLinus Torvalds sk_stream_for_retrans_queue(skb, sk) { 11221da177e4SLinus Torvalds if (skb->len > mss && 11231da177e4SLinus Torvalds !(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) { 11241da177e4SLinus Torvalds if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) { 11251da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 11261da177e4SLinus Torvalds tp->retrans_out -= tcp_skb_pcount(skb); 11271da177e4SLinus Torvalds } 11281da177e4SLinus Torvalds if (!(TCP_SKB_CB(skb)->sacked&TCPCB_LOST)) { 11291da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 11301da177e4SLinus Torvalds tp->lost_out += tcp_skb_pcount(skb); 11311da177e4SLinus Torvalds lost = 1; 11321da177e4SLinus Torvalds } 11331da177e4SLinus Torvalds } 11341da177e4SLinus Torvalds } 11351da177e4SLinus Torvalds 11361da177e4SLinus Torvalds if (!lost) 11371da177e4SLinus Torvalds return; 11381da177e4SLinus Torvalds 11391da177e4SLinus Torvalds tcp_sync_left_out(tp); 11401da177e4SLinus Torvalds 11411da177e4SLinus Torvalds /* Don't muck with the congestion window here. 11421da177e4SLinus Torvalds * Reason is that we do not increase amount of _data_ 11431da177e4SLinus Torvalds * in network, but units changed and effective 11441da177e4SLinus Torvalds * cwnd/ssthresh really reduced now. 11451da177e4SLinus Torvalds */ 11461da177e4SLinus Torvalds if (tp->ca_state != TCP_CA_Loss) { 11471da177e4SLinus Torvalds tp->high_seq = tp->snd_nxt; 11481da177e4SLinus Torvalds tp->snd_ssthresh = tcp_current_ssthresh(tp); 11491da177e4SLinus Torvalds tp->prior_ssthresh = 0; 11501da177e4SLinus Torvalds tp->undo_marker = 0; 11511da177e4SLinus Torvalds tcp_set_ca_state(tp, TCP_CA_Loss); 11521da177e4SLinus Torvalds } 11531da177e4SLinus Torvalds tcp_xmit_retransmit_queue(sk); 11541da177e4SLinus Torvalds } 11551da177e4SLinus Torvalds 11561da177e4SLinus Torvalds /* This retransmits one SKB. Policy decisions and retransmit queue 11571da177e4SLinus Torvalds * state updates are done by the caller. Returns non-zero if an 11581da177e4SLinus Torvalds * error occurred which prevented the send. 11591da177e4SLinus Torvalds */ 11601da177e4SLinus Torvalds int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) 11611da177e4SLinus Torvalds { 11621da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 11631da177e4SLinus Torvalds unsigned int cur_mss = tcp_current_mss(sk, 0); 11641da177e4SLinus Torvalds int err; 11651da177e4SLinus Torvalds 11661da177e4SLinus Torvalds /* Do not sent more than we queued. 1/4 is reserved for possible 11671da177e4SLinus Torvalds * copying overhead: frgagmentation, tunneling, mangling etc. 11681da177e4SLinus Torvalds */ 11691da177e4SLinus Torvalds if (atomic_read(&sk->sk_wmem_alloc) > 11701da177e4SLinus Torvalds min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf)) 11711da177e4SLinus Torvalds return -EAGAIN; 11721da177e4SLinus Torvalds 11731da177e4SLinus Torvalds if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) { 11741da177e4SLinus Torvalds if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 11751da177e4SLinus Torvalds BUG(); 11761da177e4SLinus Torvalds 11771da177e4SLinus Torvalds if (sk->sk_route_caps & NETIF_F_TSO) { 11781da177e4SLinus Torvalds sk->sk_route_caps &= ~NETIF_F_TSO; 11791da177e4SLinus Torvalds sock_set_flag(sk, SOCK_NO_LARGESEND); 11801da177e4SLinus Torvalds tp->mss_cache = tp->mss_cache_std; 11811da177e4SLinus Torvalds } 11821da177e4SLinus Torvalds 11831da177e4SLinus Torvalds if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) 11841da177e4SLinus Torvalds return -ENOMEM; 11851da177e4SLinus Torvalds } 11861da177e4SLinus Torvalds 11871da177e4SLinus Torvalds /* If receiver has shrunk his window, and skb is out of 11881da177e4SLinus Torvalds * new window, do not retransmit it. The exception is the 11891da177e4SLinus Torvalds * case, when window is shrunk to zero. In this case 11901da177e4SLinus Torvalds * our retransmit serves as a zero window probe. 11911da177e4SLinus Torvalds */ 11921da177e4SLinus Torvalds if (!before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd) 11931da177e4SLinus Torvalds && TCP_SKB_CB(skb)->seq != tp->snd_una) 11941da177e4SLinus Torvalds return -EAGAIN; 11951da177e4SLinus Torvalds 11961da177e4SLinus Torvalds if (skb->len > cur_mss) { 11971da177e4SLinus Torvalds int old_factor = tcp_skb_pcount(skb); 11981da177e4SLinus Torvalds int new_factor; 11991da177e4SLinus Torvalds 12001da177e4SLinus Torvalds if (tcp_fragment(sk, skb, cur_mss)) 12011da177e4SLinus Torvalds return -ENOMEM; /* We'll try again later. */ 12021da177e4SLinus Torvalds 12031da177e4SLinus Torvalds /* New SKB created, account for it. */ 12041da177e4SLinus Torvalds new_factor = tcp_skb_pcount(skb); 12051da177e4SLinus Torvalds tp->packets_out -= old_factor - new_factor; 12061da177e4SLinus Torvalds tp->packets_out += tcp_skb_pcount(skb->next); 12071da177e4SLinus Torvalds } 12081da177e4SLinus Torvalds 12091da177e4SLinus Torvalds /* Collapse two adjacent packets if worthwhile and we can. */ 12101da177e4SLinus Torvalds if(!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) && 12111da177e4SLinus Torvalds (skb->len < (cur_mss >> 1)) && 12121da177e4SLinus Torvalds (skb->next != sk->sk_send_head) && 12131da177e4SLinus Torvalds (skb->next != (struct sk_buff *)&sk->sk_write_queue) && 12141da177e4SLinus Torvalds (skb_shinfo(skb)->nr_frags == 0 && skb_shinfo(skb->next)->nr_frags == 0) && 12151da177e4SLinus Torvalds (tcp_skb_pcount(skb) == 1 && tcp_skb_pcount(skb->next) == 1) && 12161da177e4SLinus Torvalds (sysctl_tcp_retrans_collapse != 0)) 12171da177e4SLinus Torvalds tcp_retrans_try_collapse(sk, skb, cur_mss); 12181da177e4SLinus Torvalds 12191da177e4SLinus Torvalds if(tp->af_specific->rebuild_header(sk)) 12201da177e4SLinus Torvalds return -EHOSTUNREACH; /* Routing failure or similar. */ 12211da177e4SLinus Torvalds 12221da177e4SLinus Torvalds /* Some Solaris stacks overoptimize and ignore the FIN on a 12231da177e4SLinus Torvalds * retransmit when old data is attached. So strip it off 12241da177e4SLinus Torvalds * since it is cheap to do so and saves bytes on the network. 12251da177e4SLinus Torvalds */ 12261da177e4SLinus Torvalds if(skb->len > 0 && 12271da177e4SLinus Torvalds (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) && 12281da177e4SLinus Torvalds tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) { 12291da177e4SLinus Torvalds if (!pskb_trim(skb, 0)) { 12301da177e4SLinus Torvalds TCP_SKB_CB(skb)->seq = TCP_SKB_CB(skb)->end_seq - 1; 12311da177e4SLinus Torvalds skb_shinfo(skb)->tso_segs = 1; 12321da177e4SLinus Torvalds skb_shinfo(skb)->tso_size = 0; 12331da177e4SLinus Torvalds skb->ip_summed = CHECKSUM_NONE; 12341da177e4SLinus Torvalds skb->csum = 0; 12351da177e4SLinus Torvalds } 12361da177e4SLinus Torvalds } 12371da177e4SLinus Torvalds 12381da177e4SLinus Torvalds /* Make a copy, if the first transmission SKB clone we made 12391da177e4SLinus Torvalds * is still in somebody's hands, else make a clone. 12401da177e4SLinus Torvalds */ 12411da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 12421da177e4SLinus Torvalds tcp_tso_set_push(skb); 12431da177e4SLinus Torvalds 12441da177e4SLinus Torvalds err = tcp_transmit_skb(sk, (skb_cloned(skb) ? 12451da177e4SLinus Torvalds pskb_copy(skb, GFP_ATOMIC): 12461da177e4SLinus Torvalds skb_clone(skb, GFP_ATOMIC))); 12471da177e4SLinus Torvalds 12481da177e4SLinus Torvalds if (err == 0) { 12491da177e4SLinus Torvalds /* Update global TCP statistics. */ 12501da177e4SLinus Torvalds TCP_INC_STATS(TCP_MIB_RETRANSSEGS); 12511da177e4SLinus Torvalds 12521da177e4SLinus Torvalds tp->total_retrans++; 12531da177e4SLinus Torvalds 12541da177e4SLinus Torvalds #if FASTRETRANS_DEBUG > 0 12551da177e4SLinus Torvalds if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) { 12561da177e4SLinus Torvalds if (net_ratelimit()) 12571da177e4SLinus Torvalds printk(KERN_DEBUG "retrans_out leaked.\n"); 12581da177e4SLinus Torvalds } 12591da177e4SLinus Torvalds #endif 12601da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS; 12611da177e4SLinus Torvalds tp->retrans_out += tcp_skb_pcount(skb); 12621da177e4SLinus Torvalds 12631da177e4SLinus Torvalds /* Save stamp of the first retransmit. */ 12641da177e4SLinus Torvalds if (!tp->retrans_stamp) 12651da177e4SLinus Torvalds tp->retrans_stamp = TCP_SKB_CB(skb)->when; 12661da177e4SLinus Torvalds 12671da177e4SLinus Torvalds tp->undo_retrans++; 12681da177e4SLinus Torvalds 12691da177e4SLinus Torvalds /* snd_nxt is stored to detect loss of retransmitted segment, 12701da177e4SLinus Torvalds * see tcp_input.c tcp_sacktag_write_queue(). 12711da177e4SLinus Torvalds */ 12721da177e4SLinus Torvalds TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt; 12731da177e4SLinus Torvalds } 12741da177e4SLinus Torvalds return err; 12751da177e4SLinus Torvalds } 12761da177e4SLinus Torvalds 12771da177e4SLinus Torvalds /* This gets called after a retransmit timeout, and the initially 12781da177e4SLinus Torvalds * retransmitted data is acknowledged. It tries to continue 12791da177e4SLinus Torvalds * resending the rest of the retransmit queue, until either 12801da177e4SLinus Torvalds * we've sent it all or the congestion window limit is reached. 12811da177e4SLinus Torvalds * If doing SACK, the first ACK which comes back for a timeout 12821da177e4SLinus Torvalds * based retransmit packet might feed us FACK information again. 12831da177e4SLinus Torvalds * If so, we use it to avoid unnecessarily retransmissions. 12841da177e4SLinus Torvalds */ 12851da177e4SLinus Torvalds void tcp_xmit_retransmit_queue(struct sock *sk) 12861da177e4SLinus Torvalds { 12871da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 12881da177e4SLinus Torvalds struct sk_buff *skb; 12891da177e4SLinus Torvalds int packet_cnt = tp->lost_out; 12901da177e4SLinus Torvalds 12911da177e4SLinus Torvalds /* First pass: retransmit lost packets. */ 12921da177e4SLinus Torvalds if (packet_cnt) { 12931da177e4SLinus Torvalds sk_stream_for_retrans_queue(skb, sk) { 12941da177e4SLinus Torvalds __u8 sacked = TCP_SKB_CB(skb)->sacked; 12951da177e4SLinus Torvalds 12961da177e4SLinus Torvalds /* Assume this retransmit will generate 12971da177e4SLinus Torvalds * only one packet for congestion window 12981da177e4SLinus Torvalds * calculation purposes. This works because 12991da177e4SLinus Torvalds * tcp_retransmit_skb() will chop up the 13001da177e4SLinus Torvalds * packet to be MSS sized and all the 13011da177e4SLinus Torvalds * packet counting works out. 13021da177e4SLinus Torvalds */ 13031da177e4SLinus Torvalds if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) 13041da177e4SLinus Torvalds return; 13051da177e4SLinus Torvalds 13061da177e4SLinus Torvalds if (sacked&TCPCB_LOST) { 13071da177e4SLinus Torvalds if (!(sacked&(TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) { 13081da177e4SLinus Torvalds if (tcp_retransmit_skb(sk, skb)) 13091da177e4SLinus Torvalds return; 13101da177e4SLinus Torvalds if (tp->ca_state != TCP_CA_Loss) 13111da177e4SLinus Torvalds NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS); 13121da177e4SLinus Torvalds else 13131da177e4SLinus Torvalds NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS); 13141da177e4SLinus Torvalds 13151da177e4SLinus Torvalds if (skb == 13161da177e4SLinus Torvalds skb_peek(&sk->sk_write_queue)) 13171da177e4SLinus Torvalds tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto); 13181da177e4SLinus Torvalds } 13191da177e4SLinus Torvalds 13201da177e4SLinus Torvalds packet_cnt -= tcp_skb_pcount(skb); 13211da177e4SLinus Torvalds if (packet_cnt <= 0) 13221da177e4SLinus Torvalds break; 13231da177e4SLinus Torvalds } 13241da177e4SLinus Torvalds } 13251da177e4SLinus Torvalds } 13261da177e4SLinus Torvalds 13271da177e4SLinus Torvalds /* OK, demanded retransmission is finished. */ 13281da177e4SLinus Torvalds 13291da177e4SLinus Torvalds /* Forward retransmissions are possible only during Recovery. */ 13301da177e4SLinus Torvalds if (tp->ca_state != TCP_CA_Recovery) 13311da177e4SLinus Torvalds return; 13321da177e4SLinus Torvalds 13331da177e4SLinus Torvalds /* No forward retransmissions in Reno are possible. */ 13341da177e4SLinus Torvalds if (!tp->rx_opt.sack_ok) 13351da177e4SLinus Torvalds return; 13361da177e4SLinus Torvalds 13371da177e4SLinus Torvalds /* Yeah, we have to make difficult choice between forward transmission 13381da177e4SLinus Torvalds * and retransmission... Both ways have their merits... 13391da177e4SLinus Torvalds * 13401da177e4SLinus Torvalds * For now we do not retransmit anything, while we have some new 13411da177e4SLinus Torvalds * segments to send. 13421da177e4SLinus Torvalds */ 13431da177e4SLinus Torvalds 13441da177e4SLinus Torvalds if (tcp_may_send_now(sk, tp)) 13451da177e4SLinus Torvalds return; 13461da177e4SLinus Torvalds 13471da177e4SLinus Torvalds packet_cnt = 0; 13481da177e4SLinus Torvalds 13491da177e4SLinus Torvalds sk_stream_for_retrans_queue(skb, sk) { 13501da177e4SLinus Torvalds /* Similar to the retransmit loop above we 13511da177e4SLinus Torvalds * can pretend that the retransmitted SKB 13521da177e4SLinus Torvalds * we send out here will be composed of one 13531da177e4SLinus Torvalds * real MSS sized packet because tcp_retransmit_skb() 13541da177e4SLinus Torvalds * will fragment it if necessary. 13551da177e4SLinus Torvalds */ 13561da177e4SLinus Torvalds if (++packet_cnt > tp->fackets_out) 13571da177e4SLinus Torvalds break; 13581da177e4SLinus Torvalds 13591da177e4SLinus Torvalds if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) 13601da177e4SLinus Torvalds break; 13611da177e4SLinus Torvalds 13621da177e4SLinus Torvalds if (TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) 13631da177e4SLinus Torvalds continue; 13641da177e4SLinus Torvalds 13651da177e4SLinus Torvalds /* Ok, retransmit it. */ 13661da177e4SLinus Torvalds if (tcp_retransmit_skb(sk, skb)) 13671da177e4SLinus Torvalds break; 13681da177e4SLinus Torvalds 13691da177e4SLinus Torvalds if (skb == skb_peek(&sk->sk_write_queue)) 13701da177e4SLinus Torvalds tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto); 13711da177e4SLinus Torvalds 13721da177e4SLinus Torvalds NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS); 13731da177e4SLinus Torvalds } 13741da177e4SLinus Torvalds } 13751da177e4SLinus Torvalds 13761da177e4SLinus Torvalds 13771da177e4SLinus Torvalds /* Send a fin. The caller locks the socket for us. This cannot be 13781da177e4SLinus Torvalds * allowed to fail queueing a FIN frame under any circumstances. 13791da177e4SLinus Torvalds */ 13801da177e4SLinus Torvalds void tcp_send_fin(struct sock *sk) 13811da177e4SLinus Torvalds { 13821da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 13831da177e4SLinus Torvalds struct sk_buff *skb = skb_peek_tail(&sk->sk_write_queue); 13841da177e4SLinus Torvalds int mss_now; 13851da177e4SLinus Torvalds 13861da177e4SLinus Torvalds /* Optimization, tack on the FIN if we have a queue of 13871da177e4SLinus Torvalds * unsent frames. But be careful about outgoing SACKS 13881da177e4SLinus Torvalds * and IP options. 13891da177e4SLinus Torvalds */ 13901da177e4SLinus Torvalds mss_now = tcp_current_mss(sk, 1); 13911da177e4SLinus Torvalds 13921da177e4SLinus Torvalds if (sk->sk_send_head != NULL) { 13931da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN; 13941da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq++; 13951da177e4SLinus Torvalds tp->write_seq++; 13961da177e4SLinus Torvalds } else { 13971da177e4SLinus Torvalds /* Socket is locked, keep trying until memory is available. */ 13981da177e4SLinus Torvalds for (;;) { 13991da177e4SLinus Torvalds skb = alloc_skb(MAX_TCP_HEADER, GFP_KERNEL); 14001da177e4SLinus Torvalds if (skb) 14011da177e4SLinus Torvalds break; 14021da177e4SLinus Torvalds yield(); 14031da177e4SLinus Torvalds } 14041da177e4SLinus Torvalds 14051da177e4SLinus Torvalds /* Reserve space for headers and prepare control bits. */ 14061da177e4SLinus Torvalds skb_reserve(skb, MAX_TCP_HEADER); 14071da177e4SLinus Torvalds skb->csum = 0; 14081da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_FIN); 14091da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked = 0; 14101da177e4SLinus Torvalds skb_shinfo(skb)->tso_segs = 1; 14111da177e4SLinus Torvalds skb_shinfo(skb)->tso_size = 0; 14121da177e4SLinus Torvalds 14131da177e4SLinus Torvalds /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */ 14141da177e4SLinus Torvalds TCP_SKB_CB(skb)->seq = tp->write_seq; 14151da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1; 14161da177e4SLinus Torvalds tcp_queue_skb(sk, skb); 14171da177e4SLinus Torvalds } 14181da177e4SLinus Torvalds __tcp_push_pending_frames(sk, tp, mss_now, TCP_NAGLE_OFF); 14191da177e4SLinus Torvalds } 14201da177e4SLinus Torvalds 14211da177e4SLinus Torvalds /* We get here when a process closes a file descriptor (either due to 14221da177e4SLinus Torvalds * an explicit close() or as a byproduct of exit()'ing) and there 14231da177e4SLinus Torvalds * was unread data in the receive queue. This behavior is recommended 14241da177e4SLinus Torvalds * by draft-ietf-tcpimpl-prob-03.txt section 3.10. -DaveM 14251da177e4SLinus Torvalds */ 14261da177e4SLinus Torvalds void tcp_send_active_reset(struct sock *sk, int priority) 14271da177e4SLinus Torvalds { 14281da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 14291da177e4SLinus Torvalds struct sk_buff *skb; 14301da177e4SLinus Torvalds 14311da177e4SLinus Torvalds /* NOTE: No TCP options attached and we never retransmit this. */ 14321da177e4SLinus Torvalds skb = alloc_skb(MAX_TCP_HEADER, priority); 14331da177e4SLinus Torvalds if (!skb) { 14341da177e4SLinus Torvalds NET_INC_STATS(LINUX_MIB_TCPABORTFAILED); 14351da177e4SLinus Torvalds return; 14361da177e4SLinus Torvalds } 14371da177e4SLinus Torvalds 14381da177e4SLinus Torvalds /* Reserve space for headers and prepare control bits. */ 14391da177e4SLinus Torvalds skb_reserve(skb, MAX_TCP_HEADER); 14401da177e4SLinus Torvalds skb->csum = 0; 14411da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_RST); 14421da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked = 0; 14431da177e4SLinus Torvalds skb_shinfo(skb)->tso_segs = 1; 14441da177e4SLinus Torvalds skb_shinfo(skb)->tso_size = 0; 14451da177e4SLinus Torvalds 14461da177e4SLinus Torvalds /* Send it off. */ 14471da177e4SLinus Torvalds TCP_SKB_CB(skb)->seq = tcp_acceptable_seq(sk, tp); 14481da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq; 14491da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 14501da177e4SLinus Torvalds if (tcp_transmit_skb(sk, skb)) 14511da177e4SLinus Torvalds NET_INC_STATS(LINUX_MIB_TCPABORTFAILED); 14521da177e4SLinus Torvalds } 14531da177e4SLinus Torvalds 14541da177e4SLinus Torvalds /* WARNING: This routine must only be called when we have already sent 14551da177e4SLinus Torvalds * a SYN packet that crossed the incoming SYN that caused this routine 14561da177e4SLinus Torvalds * to get called. If this assumption fails then the initial rcv_wnd 14571da177e4SLinus Torvalds * and rcv_wscale values will not be correct. 14581da177e4SLinus Torvalds */ 14591da177e4SLinus Torvalds int tcp_send_synack(struct sock *sk) 14601da177e4SLinus Torvalds { 14611da177e4SLinus Torvalds struct sk_buff* skb; 14621da177e4SLinus Torvalds 14631da177e4SLinus Torvalds skb = skb_peek(&sk->sk_write_queue); 14641da177e4SLinus Torvalds if (skb == NULL || !(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_SYN)) { 14651da177e4SLinus Torvalds printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n"); 14661da177e4SLinus Torvalds return -EFAULT; 14671da177e4SLinus Torvalds } 14681da177e4SLinus Torvalds if (!(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_ACK)) { 14691da177e4SLinus Torvalds if (skb_cloned(skb)) { 14701da177e4SLinus Torvalds struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC); 14711da177e4SLinus Torvalds if (nskb == NULL) 14721da177e4SLinus Torvalds return -ENOMEM; 14731da177e4SLinus Torvalds __skb_unlink(skb, &sk->sk_write_queue); 14741da177e4SLinus Torvalds skb_header_release(nskb); 14751da177e4SLinus Torvalds __skb_queue_head(&sk->sk_write_queue, nskb); 14761da177e4SLinus Torvalds sk_stream_free_skb(sk, skb); 14771da177e4SLinus Torvalds sk_charge_skb(sk, nskb); 14781da177e4SLinus Torvalds skb = nskb; 14791da177e4SLinus Torvalds } 14801da177e4SLinus Torvalds 14811da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ACK; 14821da177e4SLinus Torvalds TCP_ECN_send_synack(tcp_sk(sk), skb); 14831da177e4SLinus Torvalds } 14841da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 14851da177e4SLinus Torvalds return tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC)); 14861da177e4SLinus Torvalds } 14871da177e4SLinus Torvalds 14881da177e4SLinus Torvalds /* 14891da177e4SLinus Torvalds * Prepare a SYN-ACK. 14901da177e4SLinus Torvalds */ 14911da177e4SLinus Torvalds struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst, 149260236fddSArnaldo Carvalho de Melo struct request_sock *req) 14931da177e4SLinus Torvalds { 14942e6599cbSArnaldo Carvalho de Melo struct inet_request_sock *ireq = inet_rsk(req); 14951da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 14961da177e4SLinus Torvalds struct tcphdr *th; 14971da177e4SLinus Torvalds int tcp_header_size; 14981da177e4SLinus Torvalds struct sk_buff *skb; 14991da177e4SLinus Torvalds 15001da177e4SLinus Torvalds skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC); 15011da177e4SLinus Torvalds if (skb == NULL) 15021da177e4SLinus Torvalds return NULL; 15031da177e4SLinus Torvalds 15041da177e4SLinus Torvalds /* Reserve space for headers. */ 15051da177e4SLinus Torvalds skb_reserve(skb, MAX_TCP_HEADER); 15061da177e4SLinus Torvalds 15071da177e4SLinus Torvalds skb->dst = dst_clone(dst); 15081da177e4SLinus Torvalds 15091da177e4SLinus Torvalds tcp_header_size = (sizeof(struct tcphdr) + TCPOLEN_MSS + 15102e6599cbSArnaldo Carvalho de Melo (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) + 15112e6599cbSArnaldo Carvalho de Melo (ireq->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) + 15121da177e4SLinus Torvalds /* SACK_PERM is in the place of NOP NOP of TS */ 15132e6599cbSArnaldo Carvalho de Melo ((ireq->sack_ok && !ireq->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0)); 15141da177e4SLinus Torvalds skb->h.th = th = (struct tcphdr *) skb_push(skb, tcp_header_size); 15151da177e4SLinus Torvalds 15161da177e4SLinus Torvalds memset(th, 0, sizeof(struct tcphdr)); 15171da177e4SLinus Torvalds th->syn = 1; 15181da177e4SLinus Torvalds th->ack = 1; 15191da177e4SLinus Torvalds if (dst->dev->features&NETIF_F_TSO) 15202e6599cbSArnaldo Carvalho de Melo ireq->ecn_ok = 0; 15211da177e4SLinus Torvalds TCP_ECN_make_synack(req, th); 15221da177e4SLinus Torvalds th->source = inet_sk(sk)->sport; 15232e6599cbSArnaldo Carvalho de Melo th->dest = ireq->rmt_port; 15242e6599cbSArnaldo Carvalho de Melo TCP_SKB_CB(skb)->seq = tcp_rsk(req)->snt_isn; 15251da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1; 15261da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked = 0; 15271da177e4SLinus Torvalds skb_shinfo(skb)->tso_segs = 1; 15281da177e4SLinus Torvalds skb_shinfo(skb)->tso_size = 0; 15291da177e4SLinus Torvalds th->seq = htonl(TCP_SKB_CB(skb)->seq); 15302e6599cbSArnaldo Carvalho de Melo th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1); 15311da177e4SLinus Torvalds if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */ 15321da177e4SLinus Torvalds __u8 rcv_wscale; 15331da177e4SLinus Torvalds /* Set this up on the first call only */ 15341da177e4SLinus Torvalds req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW); 15351da177e4SLinus Torvalds /* tcp_full_space because it is guaranteed to be the first packet */ 15361da177e4SLinus Torvalds tcp_select_initial_window(tcp_full_space(sk), 15372e6599cbSArnaldo Carvalho de Melo dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0), 15381da177e4SLinus Torvalds &req->rcv_wnd, 15391da177e4SLinus Torvalds &req->window_clamp, 15402e6599cbSArnaldo Carvalho de Melo ireq->wscale_ok, 15411da177e4SLinus Torvalds &rcv_wscale); 15422e6599cbSArnaldo Carvalho de Melo ireq->rcv_wscale = rcv_wscale; 15431da177e4SLinus Torvalds } 15441da177e4SLinus Torvalds 15451da177e4SLinus Torvalds /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */ 15461da177e4SLinus Torvalds th->window = htons(req->rcv_wnd); 15471da177e4SLinus Torvalds 15481da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 15492e6599cbSArnaldo Carvalho de Melo tcp_syn_build_options((__u32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), ireq->tstamp_ok, 15502e6599cbSArnaldo Carvalho de Melo ireq->sack_ok, ireq->wscale_ok, ireq->rcv_wscale, 15511da177e4SLinus Torvalds TCP_SKB_CB(skb)->when, 15521da177e4SLinus Torvalds req->ts_recent); 15531da177e4SLinus Torvalds 15541da177e4SLinus Torvalds skb->csum = 0; 15551da177e4SLinus Torvalds th->doff = (tcp_header_size >> 2); 15561da177e4SLinus Torvalds TCP_INC_STATS(TCP_MIB_OUTSEGS); 15571da177e4SLinus Torvalds return skb; 15581da177e4SLinus Torvalds } 15591da177e4SLinus Torvalds 15601da177e4SLinus Torvalds /* 15611da177e4SLinus Torvalds * Do all connect socket setups that can be done AF independent. 15621da177e4SLinus Torvalds */ 15631da177e4SLinus Torvalds static inline void tcp_connect_init(struct sock *sk) 15641da177e4SLinus Torvalds { 15651da177e4SLinus Torvalds struct dst_entry *dst = __sk_dst_get(sk); 15661da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 15671da177e4SLinus Torvalds __u8 rcv_wscale; 15681da177e4SLinus Torvalds 15691da177e4SLinus Torvalds /* We'll fix this up when we get a response from the other end. 15701da177e4SLinus Torvalds * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. 15711da177e4SLinus Torvalds */ 15721da177e4SLinus Torvalds tp->tcp_header_len = sizeof(struct tcphdr) + 15731da177e4SLinus Torvalds (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0); 15741da177e4SLinus Torvalds 15751da177e4SLinus Torvalds /* If user gave his TCP_MAXSEG, record it to clamp */ 15761da177e4SLinus Torvalds if (tp->rx_opt.user_mss) 15771da177e4SLinus Torvalds tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; 15781da177e4SLinus Torvalds tp->max_window = 0; 15791da177e4SLinus Torvalds tcp_sync_mss(sk, dst_mtu(dst)); 15801da177e4SLinus Torvalds 15811da177e4SLinus Torvalds if (!tp->window_clamp) 15821da177e4SLinus Torvalds tp->window_clamp = dst_metric(dst, RTAX_WINDOW); 15831da177e4SLinus Torvalds tp->advmss = dst_metric(dst, RTAX_ADVMSS); 15841da177e4SLinus Torvalds tcp_initialize_rcv_mss(sk); 15851da177e4SLinus Torvalds 15861da177e4SLinus Torvalds tcp_select_initial_window(tcp_full_space(sk), 15871da177e4SLinus Torvalds tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0), 15881da177e4SLinus Torvalds &tp->rcv_wnd, 15891da177e4SLinus Torvalds &tp->window_clamp, 15901da177e4SLinus Torvalds sysctl_tcp_window_scaling, 15911da177e4SLinus Torvalds &rcv_wscale); 15921da177e4SLinus Torvalds 15931da177e4SLinus Torvalds tp->rx_opt.rcv_wscale = rcv_wscale; 15941da177e4SLinus Torvalds tp->rcv_ssthresh = tp->rcv_wnd; 15951da177e4SLinus Torvalds 15961da177e4SLinus Torvalds sk->sk_err = 0; 15971da177e4SLinus Torvalds sock_reset_flag(sk, SOCK_DONE); 15981da177e4SLinus Torvalds tp->snd_wnd = 0; 15991da177e4SLinus Torvalds tcp_init_wl(tp, tp->write_seq, 0); 16001da177e4SLinus Torvalds tp->snd_una = tp->write_seq; 16011da177e4SLinus Torvalds tp->snd_sml = tp->write_seq; 16021da177e4SLinus Torvalds tp->rcv_nxt = 0; 16031da177e4SLinus Torvalds tp->rcv_wup = 0; 16041da177e4SLinus Torvalds tp->copied_seq = 0; 16051da177e4SLinus Torvalds 16061da177e4SLinus Torvalds tp->rto = TCP_TIMEOUT_INIT; 16071da177e4SLinus Torvalds tp->retransmits = 0; 16081da177e4SLinus Torvalds tcp_clear_retrans(tp); 16091da177e4SLinus Torvalds } 16101da177e4SLinus Torvalds 16111da177e4SLinus Torvalds /* 16121da177e4SLinus Torvalds * Build a SYN and send it off. 16131da177e4SLinus Torvalds */ 16141da177e4SLinus Torvalds int tcp_connect(struct sock *sk) 16151da177e4SLinus Torvalds { 16161da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 16171da177e4SLinus Torvalds struct sk_buff *buff; 16181da177e4SLinus Torvalds 16191da177e4SLinus Torvalds tcp_connect_init(sk); 16201da177e4SLinus Torvalds 16211da177e4SLinus Torvalds buff = alloc_skb(MAX_TCP_HEADER + 15, sk->sk_allocation); 16221da177e4SLinus Torvalds if (unlikely(buff == NULL)) 16231da177e4SLinus Torvalds return -ENOBUFS; 16241da177e4SLinus Torvalds 16251da177e4SLinus Torvalds /* Reserve space for headers. */ 16261da177e4SLinus Torvalds skb_reserve(buff, MAX_TCP_HEADER); 16271da177e4SLinus Torvalds 16281da177e4SLinus Torvalds TCP_SKB_CB(buff)->flags = TCPCB_FLAG_SYN; 16291da177e4SLinus Torvalds TCP_ECN_send_syn(sk, tp, buff); 16301da177e4SLinus Torvalds TCP_SKB_CB(buff)->sacked = 0; 16311da177e4SLinus Torvalds skb_shinfo(buff)->tso_segs = 1; 16321da177e4SLinus Torvalds skb_shinfo(buff)->tso_size = 0; 16331da177e4SLinus Torvalds buff->csum = 0; 16341da177e4SLinus Torvalds TCP_SKB_CB(buff)->seq = tp->write_seq++; 16351da177e4SLinus Torvalds TCP_SKB_CB(buff)->end_seq = tp->write_seq; 16361da177e4SLinus Torvalds tp->snd_nxt = tp->write_seq; 16371da177e4SLinus Torvalds tp->pushed_seq = tp->write_seq; 16381da177e4SLinus Torvalds 16391da177e4SLinus Torvalds /* Send it off. */ 16401da177e4SLinus Torvalds TCP_SKB_CB(buff)->when = tcp_time_stamp; 16411da177e4SLinus Torvalds tp->retrans_stamp = TCP_SKB_CB(buff)->when; 16421da177e4SLinus Torvalds skb_header_release(buff); 16431da177e4SLinus Torvalds __skb_queue_tail(&sk->sk_write_queue, buff); 16441da177e4SLinus Torvalds sk_charge_skb(sk, buff); 16451da177e4SLinus Torvalds tp->packets_out += tcp_skb_pcount(buff); 16461da177e4SLinus Torvalds tcp_transmit_skb(sk, skb_clone(buff, GFP_KERNEL)); 16471da177e4SLinus Torvalds TCP_INC_STATS(TCP_MIB_ACTIVEOPENS); 16481da177e4SLinus Torvalds 16491da177e4SLinus Torvalds /* Timer for repeating the SYN until an answer. */ 16501da177e4SLinus Torvalds tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto); 16511da177e4SLinus Torvalds return 0; 16521da177e4SLinus Torvalds } 16531da177e4SLinus Torvalds 16541da177e4SLinus Torvalds /* Send out a delayed ack, the caller does the policy checking 16551da177e4SLinus Torvalds * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check() 16561da177e4SLinus Torvalds * for details. 16571da177e4SLinus Torvalds */ 16581da177e4SLinus Torvalds void tcp_send_delayed_ack(struct sock *sk) 16591da177e4SLinus Torvalds { 16601da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 16611da177e4SLinus Torvalds int ato = tp->ack.ato; 16621da177e4SLinus Torvalds unsigned long timeout; 16631da177e4SLinus Torvalds 16641da177e4SLinus Torvalds if (ato > TCP_DELACK_MIN) { 16651da177e4SLinus Torvalds int max_ato = HZ/2; 16661da177e4SLinus Torvalds 16671da177e4SLinus Torvalds if (tp->ack.pingpong || (tp->ack.pending&TCP_ACK_PUSHED)) 16681da177e4SLinus Torvalds max_ato = TCP_DELACK_MAX; 16691da177e4SLinus Torvalds 16701da177e4SLinus Torvalds /* Slow path, intersegment interval is "high". */ 16711da177e4SLinus Torvalds 16721da177e4SLinus Torvalds /* If some rtt estimate is known, use it to bound delayed ack. 16731da177e4SLinus Torvalds * Do not use tp->rto here, use results of rtt measurements 16741da177e4SLinus Torvalds * directly. 16751da177e4SLinus Torvalds */ 16761da177e4SLinus Torvalds if (tp->srtt) { 16771da177e4SLinus Torvalds int rtt = max(tp->srtt>>3, TCP_DELACK_MIN); 16781da177e4SLinus Torvalds 16791da177e4SLinus Torvalds if (rtt < max_ato) 16801da177e4SLinus Torvalds max_ato = rtt; 16811da177e4SLinus Torvalds } 16821da177e4SLinus Torvalds 16831da177e4SLinus Torvalds ato = min(ato, max_ato); 16841da177e4SLinus Torvalds } 16851da177e4SLinus Torvalds 16861da177e4SLinus Torvalds /* Stay within the limit we were given */ 16871da177e4SLinus Torvalds timeout = jiffies + ato; 16881da177e4SLinus Torvalds 16891da177e4SLinus Torvalds /* Use new timeout only if there wasn't a older one earlier. */ 16901da177e4SLinus Torvalds if (tp->ack.pending&TCP_ACK_TIMER) { 16911da177e4SLinus Torvalds /* If delack timer was blocked or is about to expire, 16921da177e4SLinus Torvalds * send ACK now. 16931da177e4SLinus Torvalds */ 16941da177e4SLinus Torvalds if (tp->ack.blocked || time_before_eq(tp->ack.timeout, jiffies+(ato>>2))) { 16951da177e4SLinus Torvalds tcp_send_ack(sk); 16961da177e4SLinus Torvalds return; 16971da177e4SLinus Torvalds } 16981da177e4SLinus Torvalds 16991da177e4SLinus Torvalds if (!time_before(timeout, tp->ack.timeout)) 17001da177e4SLinus Torvalds timeout = tp->ack.timeout; 17011da177e4SLinus Torvalds } 17021da177e4SLinus Torvalds tp->ack.pending |= TCP_ACK_SCHED|TCP_ACK_TIMER; 17031da177e4SLinus Torvalds tp->ack.timeout = timeout; 17041da177e4SLinus Torvalds sk_reset_timer(sk, &tp->delack_timer, timeout); 17051da177e4SLinus Torvalds } 17061da177e4SLinus Torvalds 17071da177e4SLinus Torvalds /* This routine sends an ack and also updates the window. */ 17081da177e4SLinus Torvalds void tcp_send_ack(struct sock *sk) 17091da177e4SLinus Torvalds { 17101da177e4SLinus Torvalds /* If we have been reset, we may not send again. */ 17111da177e4SLinus Torvalds if (sk->sk_state != TCP_CLOSE) { 17121da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 17131da177e4SLinus Torvalds struct sk_buff *buff; 17141da177e4SLinus Torvalds 17151da177e4SLinus Torvalds /* We are not putting this on the write queue, so 17161da177e4SLinus Torvalds * tcp_transmit_skb() will set the ownership to this 17171da177e4SLinus Torvalds * sock. 17181da177e4SLinus Torvalds */ 17191da177e4SLinus Torvalds buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); 17201da177e4SLinus Torvalds if (buff == NULL) { 17211da177e4SLinus Torvalds tcp_schedule_ack(tp); 17221da177e4SLinus Torvalds tp->ack.ato = TCP_ATO_MIN; 17231da177e4SLinus Torvalds tcp_reset_xmit_timer(sk, TCP_TIME_DACK, TCP_DELACK_MAX); 17241da177e4SLinus Torvalds return; 17251da177e4SLinus Torvalds } 17261da177e4SLinus Torvalds 17271da177e4SLinus Torvalds /* Reserve space for headers and prepare control bits. */ 17281da177e4SLinus Torvalds skb_reserve(buff, MAX_TCP_HEADER); 17291da177e4SLinus Torvalds buff->csum = 0; 17301da177e4SLinus Torvalds TCP_SKB_CB(buff)->flags = TCPCB_FLAG_ACK; 17311da177e4SLinus Torvalds TCP_SKB_CB(buff)->sacked = 0; 17321da177e4SLinus Torvalds skb_shinfo(buff)->tso_segs = 1; 17331da177e4SLinus Torvalds skb_shinfo(buff)->tso_size = 0; 17341da177e4SLinus Torvalds 17351da177e4SLinus Torvalds /* Send it off, this clears delayed acks for us. */ 17361da177e4SLinus Torvalds TCP_SKB_CB(buff)->seq = TCP_SKB_CB(buff)->end_seq = tcp_acceptable_seq(sk, tp); 17371da177e4SLinus Torvalds TCP_SKB_CB(buff)->when = tcp_time_stamp; 17381da177e4SLinus Torvalds tcp_transmit_skb(sk, buff); 17391da177e4SLinus Torvalds } 17401da177e4SLinus Torvalds } 17411da177e4SLinus Torvalds 17421da177e4SLinus Torvalds /* This routine sends a packet with an out of date sequence 17431da177e4SLinus Torvalds * number. It assumes the other end will try to ack it. 17441da177e4SLinus Torvalds * 17451da177e4SLinus Torvalds * Question: what should we make while urgent mode? 17461da177e4SLinus Torvalds * 4.4BSD forces sending single byte of data. We cannot send 17471da177e4SLinus Torvalds * out of window data, because we have SND.NXT==SND.MAX... 17481da177e4SLinus Torvalds * 17491da177e4SLinus Torvalds * Current solution: to send TWO zero-length segments in urgent mode: 17501da177e4SLinus Torvalds * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is 17511da177e4SLinus Torvalds * out-of-date with SND.UNA-1 to probe window. 17521da177e4SLinus Torvalds */ 17531da177e4SLinus Torvalds static int tcp_xmit_probe_skb(struct sock *sk, int urgent) 17541da177e4SLinus Torvalds { 17551da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 17561da177e4SLinus Torvalds struct sk_buff *skb; 17571da177e4SLinus Torvalds 17581da177e4SLinus Torvalds /* We don't queue it, tcp_transmit_skb() sets ownership. */ 17591da177e4SLinus Torvalds skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); 17601da177e4SLinus Torvalds if (skb == NULL) 17611da177e4SLinus Torvalds return -1; 17621da177e4SLinus Torvalds 17631da177e4SLinus Torvalds /* Reserve space for headers and set control bits. */ 17641da177e4SLinus Torvalds skb_reserve(skb, MAX_TCP_HEADER); 17651da177e4SLinus Torvalds skb->csum = 0; 17661da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags = TCPCB_FLAG_ACK; 17671da177e4SLinus Torvalds TCP_SKB_CB(skb)->sacked = urgent; 17681da177e4SLinus Torvalds skb_shinfo(skb)->tso_segs = 1; 17691da177e4SLinus Torvalds skb_shinfo(skb)->tso_size = 0; 17701da177e4SLinus Torvalds 17711da177e4SLinus Torvalds /* Use a previous sequence. This should cause the other 17721da177e4SLinus Torvalds * end to send an ack. Don't queue or clone SKB, just 17731da177e4SLinus Torvalds * send it. 17741da177e4SLinus Torvalds */ 17751da177e4SLinus Torvalds TCP_SKB_CB(skb)->seq = urgent ? tp->snd_una : tp->snd_una - 1; 17761da177e4SLinus Torvalds TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq; 17771da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 17781da177e4SLinus Torvalds return tcp_transmit_skb(sk, skb); 17791da177e4SLinus Torvalds } 17801da177e4SLinus Torvalds 17811da177e4SLinus Torvalds int tcp_write_wakeup(struct sock *sk) 17821da177e4SLinus Torvalds { 17831da177e4SLinus Torvalds if (sk->sk_state != TCP_CLOSE) { 17841da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 17851da177e4SLinus Torvalds struct sk_buff *skb; 17861da177e4SLinus Torvalds 17871da177e4SLinus Torvalds if ((skb = sk->sk_send_head) != NULL && 17881da177e4SLinus Torvalds before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)) { 17891da177e4SLinus Torvalds int err; 17901da177e4SLinus Torvalds unsigned int mss = tcp_current_mss(sk, 0); 17911da177e4SLinus Torvalds unsigned int seg_size = tp->snd_una+tp->snd_wnd-TCP_SKB_CB(skb)->seq; 17921da177e4SLinus Torvalds 17931da177e4SLinus Torvalds if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq)) 17941da177e4SLinus Torvalds tp->pushed_seq = TCP_SKB_CB(skb)->end_seq; 17951da177e4SLinus Torvalds 17961da177e4SLinus Torvalds /* We are probing the opening of a window 17971da177e4SLinus Torvalds * but the window size is != 0 17981da177e4SLinus Torvalds * must have been a result SWS avoidance ( sender ) 17991da177e4SLinus Torvalds */ 18001da177e4SLinus Torvalds if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq || 18011da177e4SLinus Torvalds skb->len > mss) { 18021da177e4SLinus Torvalds seg_size = min(seg_size, mss); 18031da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; 18041da177e4SLinus Torvalds if (tcp_fragment(sk, skb, seg_size)) 18051da177e4SLinus Torvalds return -1; 18061da177e4SLinus Torvalds /* SWS override triggered forced fragmentation. 18071da177e4SLinus Torvalds * Disable TSO, the connection is too sick. */ 18081da177e4SLinus Torvalds if (sk->sk_route_caps & NETIF_F_TSO) { 18091da177e4SLinus Torvalds sock_set_flag(sk, SOCK_NO_LARGESEND); 18101da177e4SLinus Torvalds sk->sk_route_caps &= ~NETIF_F_TSO; 18111da177e4SLinus Torvalds tp->mss_cache = tp->mss_cache_std; 18121da177e4SLinus Torvalds } 18131da177e4SLinus Torvalds } else if (!tcp_skb_pcount(skb)) 1814d5ac99a6SDavid S. Miller tcp_set_skb_tso_segs(sk, skb); 18151da177e4SLinus Torvalds 18161da177e4SLinus Torvalds TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; 18171da177e4SLinus Torvalds TCP_SKB_CB(skb)->when = tcp_time_stamp; 18181da177e4SLinus Torvalds tcp_tso_set_push(skb); 18191da177e4SLinus Torvalds err = tcp_transmit_skb(sk, skb_clone(skb, GFP_ATOMIC)); 18201da177e4SLinus Torvalds if (!err) { 18211da177e4SLinus Torvalds update_send_head(sk, tp, skb); 18221da177e4SLinus Torvalds } 18231da177e4SLinus Torvalds return err; 18241da177e4SLinus Torvalds } else { 18251da177e4SLinus Torvalds if (tp->urg_mode && 18261da177e4SLinus Torvalds between(tp->snd_up, tp->snd_una+1, tp->snd_una+0xFFFF)) 18271da177e4SLinus Torvalds tcp_xmit_probe_skb(sk, TCPCB_URG); 18281da177e4SLinus Torvalds return tcp_xmit_probe_skb(sk, 0); 18291da177e4SLinus Torvalds } 18301da177e4SLinus Torvalds } 18311da177e4SLinus Torvalds return -1; 18321da177e4SLinus Torvalds } 18331da177e4SLinus Torvalds 18341da177e4SLinus Torvalds /* A window probe timeout has occurred. If window is not closed send 18351da177e4SLinus Torvalds * a partial packet else a zero probe. 18361da177e4SLinus Torvalds */ 18371da177e4SLinus Torvalds void tcp_send_probe0(struct sock *sk) 18381da177e4SLinus Torvalds { 18391da177e4SLinus Torvalds struct tcp_sock *tp = tcp_sk(sk); 18401da177e4SLinus Torvalds int err; 18411da177e4SLinus Torvalds 18421da177e4SLinus Torvalds err = tcp_write_wakeup(sk); 18431da177e4SLinus Torvalds 18441da177e4SLinus Torvalds if (tp->packets_out || !sk->sk_send_head) { 18451da177e4SLinus Torvalds /* Cancel probe timer, if it is not required. */ 18461da177e4SLinus Torvalds tp->probes_out = 0; 18471da177e4SLinus Torvalds tp->backoff = 0; 18481da177e4SLinus Torvalds return; 18491da177e4SLinus Torvalds } 18501da177e4SLinus Torvalds 18511da177e4SLinus Torvalds if (err <= 0) { 18521da177e4SLinus Torvalds if (tp->backoff < sysctl_tcp_retries2) 18531da177e4SLinus Torvalds tp->backoff++; 18541da177e4SLinus Torvalds tp->probes_out++; 18551da177e4SLinus Torvalds tcp_reset_xmit_timer (sk, TCP_TIME_PROBE0, 18561da177e4SLinus Torvalds min(tp->rto << tp->backoff, TCP_RTO_MAX)); 18571da177e4SLinus Torvalds } else { 18581da177e4SLinus Torvalds /* If packet was not sent due to local congestion, 18591da177e4SLinus Torvalds * do not backoff and do not remember probes_out. 18601da177e4SLinus Torvalds * Let local senders to fight for local resources. 18611da177e4SLinus Torvalds * 18621da177e4SLinus Torvalds * Use accumulated backoff yet. 18631da177e4SLinus Torvalds */ 18641da177e4SLinus Torvalds if (!tp->probes_out) 18651da177e4SLinus Torvalds tp->probes_out=1; 18661da177e4SLinus Torvalds tcp_reset_xmit_timer (sk, TCP_TIME_PROBE0, 18671da177e4SLinus Torvalds min(tp->rto << tp->backoff, TCP_RESOURCE_PROBE_INTERVAL)); 18681da177e4SLinus Torvalds } 18691da177e4SLinus Torvalds } 18701da177e4SLinus Torvalds 18711da177e4SLinus Torvalds EXPORT_SYMBOL(tcp_connect); 18721da177e4SLinus Torvalds EXPORT_SYMBOL(tcp_make_synack); 18731da177e4SLinus Torvalds EXPORT_SYMBOL(tcp_simple_retransmit); 18741da177e4SLinus Torvalds EXPORT_SYMBOL(tcp_sync_mss); 1875