1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * INET An implementation of the TCP/IP protocol suite for the LINUX 4 * operating system. INET is implemented using the BSD Socket 5 * interface as the means of communication with the user level. 6 * 7 * The Internet Protocol (IP) output module. 8 * 9 * Authors: Ross Biro 10 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 11 * Donald Becker, <becker@super.org> 12 * Alan Cox, <Alan.Cox@linux.org> 13 * Richard Underwood 14 * Stefan Becker, <stefanb@yello.ping.de> 15 * Jorge Cwik, <jorge@laser.satlink.net> 16 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 17 * Hirokazu Takahashi, <taka@valinux.co.jp> 18 * 19 * See ip_input.c for original log 20 * 21 * Fixes: 22 * Alan Cox : Missing nonblock feature in ip_build_xmit. 23 * Mike Kilburn : htons() missing in ip_build_xmit. 24 * Bradford Johnson: Fix faulty handling of some frames when 25 * no route is found. 26 * Alexander Demenshin: Missing sk/skb free in ip_queue_xmit 27 * (in case if packet not accepted by 28 * output firewall rules) 29 * Mike McLagan : Routing by source 30 * Alexey Kuznetsov: use new route cache 31 * Andi Kleen: Fix broken PMTU recovery and remove 32 * some redundant tests. 33 * Vitaly E. Lavrov : Transparent proxy revived after year coma. 34 * Andi Kleen : Replace ip_reply with ip_send_reply. 35 * Andi Kleen : Split fast and slow ip_build_xmit path 36 * for decreased register pressure on x86 37 * and more readability. 38 * Marc Boucher : When call_out_firewall returns FW_QUEUE, 39 * silently drop skb instead of failing with -EPERM. 40 * Detlev Wengorz : Copy protocol for fragments. 41 * Hirokazu Takahashi: HW checksumming for outgoing UDP 42 * datagrams. 43 * Hirokazu Takahashi: sendfile() on UDP works now. 44 */ 45 46 #include <linux/uaccess.h> 47 #include <linux/module.h> 48 #include <linux/types.h> 49 #include <linux/kernel.h> 50 #include <linux/mm.h> 51 #include <linux/string.h> 52 #include <linux/errno.h> 53 #include <linux/highmem.h> 54 #include <linux/slab.h> 55 56 #include <linux/socket.h> 57 #include <linux/sockios.h> 58 #include <linux/in.h> 59 #include <linux/inet.h> 60 #include <linux/netdevice.h> 61 #include <linux/etherdevice.h> 62 #include <linux/proc_fs.h> 63 #include <linux/stat.h> 64 #include <linux/init.h> 65 66 #include <net/snmp.h> 67 #include <net/ip.h> 68 #include <net/protocol.h> 69 #include <net/route.h> 70 #include <net/xfrm.h> 71 #include <linux/skbuff.h> 72 #include <net/sock.h> 73 #include <net/arp.h> 74 #include <net/icmp.h> 75 #include <net/checksum.h> 76 #include <net/gso.h> 77 #include <net/inetpeer.h> 78 #include <net/inet_ecn.h> 79 #include <net/lwtunnel.h> 80 #include <linux/bpf-cgroup.h> 81 #include <linux/igmp.h> 82 #include <linux/netfilter_ipv4.h> 83 #include <linux/netfilter_bridge.h> 84 #include <linux/netlink.h> 85 #include <linux/tcp.h> 86 87 static int 88 ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, 89 unsigned int mtu, 90 int (*output)(struct net *, struct sock *, struct sk_buff *)); 91 92 /* Generate a checksum for an outgoing IP datagram. */ 93 void ip_send_check(struct iphdr *iph) 94 { 95 iph->check = 0; 96 iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl); 97 } 98 EXPORT_SYMBOL(ip_send_check); 99 100 int __ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb) 101 { 102 struct iphdr *iph = ip_hdr(skb); 103 104 IP_INC_STATS(net, IPSTATS_MIB_OUTREQUESTS); 105 106 iph_set_totlen(iph, skb->len); 107 ip_send_check(iph); 108 109 /* if egress device is enslaved to an L3 master device pass the 110 * skb to its handler for processing 111 */ 112 skb = l3mdev_ip_out(sk, skb); 113 if (unlikely(!skb)) 114 return 0; 115 116 skb->protocol = htons(ETH_P_IP); 117 118 return nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT, 119 net, sk, skb, NULL, skb_dst(skb)->dev, 120 dst_output); 121 } 122 123 int ip_local_out(struct net *net, struct sock *sk, struct sk_buff *skb) 124 { 125 int err; 126 127 err = __ip_local_out(net, sk, skb); 128 if (likely(err == 1)) 129 err = dst_output(net, sk, skb); 130 131 return err; 132 } 133 EXPORT_SYMBOL_GPL(ip_local_out); 134 135 static inline int ip_select_ttl(const struct inet_sock *inet, 136 const struct dst_entry *dst) 137 { 138 int ttl = READ_ONCE(inet->uc_ttl); 139 140 if (ttl < 0) 141 ttl = ip4_dst_hoplimit(dst); 142 return ttl; 143 } 144 145 /* 146 * Add an ip header to a skbuff and send it out. 147 * 148 */ 149 int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk, 150 __be32 saddr, __be32 daddr, struct ip_options_rcu *opt, 151 u8 tos) 152 { 153 const struct inet_sock *inet = inet_sk(sk); 154 struct rtable *rt = skb_rtable(skb); 155 struct net *net = sock_net(sk); 156 struct iphdr *iph; 157 158 /* Build the IP header. */ 159 skb_push(skb, sizeof(struct iphdr) + (opt ? opt->opt.optlen : 0)); 160 skb_reset_network_header(skb); 161 iph = ip_hdr(skb); 162 iph->version = 4; 163 iph->ihl = 5; 164 iph->tos = tos; 165 iph->ttl = ip_select_ttl(inet, &rt->dst); 166 iph->daddr = (opt && opt->opt.srr ? opt->opt.faddr : daddr); 167 iph->saddr = saddr; 168 iph->protocol = sk->sk_protocol; 169 /* Do not bother generating IPID for small packets (eg SYNACK) */ 170 if (skb->len <= IPV4_MIN_MTU || ip_dont_fragment(sk, &rt->dst)) { 171 iph->frag_off = htons(IP_DF); 172 iph->id = 0; 173 } else { 174 iph->frag_off = 0; 175 /* TCP packets here are SYNACK with fat IPv4/TCP options. 176 * Avoid using the hashed IP ident generator. 177 */ 178 if (sk->sk_protocol == IPPROTO_TCP) 179 iph->id = (__force __be16)get_random_u16(); 180 else 181 __ip_select_ident(net, iph, 1); 182 } 183 184 if (opt && opt->opt.optlen) { 185 iph->ihl += opt->opt.optlen>>2; 186 ip_options_build(skb, &opt->opt, daddr, rt); 187 } 188 189 skb->priority = READ_ONCE(sk->sk_priority); 190 if (!skb->mark) 191 skb->mark = READ_ONCE(sk->sk_mark); 192 193 /* Send it out. */ 194 return ip_local_out(net, skb->sk, skb); 195 } 196 EXPORT_SYMBOL_GPL(ip_build_and_send_pkt); 197 198 static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *skb) 199 { 200 struct dst_entry *dst = skb_dst(skb); 201 struct rtable *rt = (struct rtable *)dst; 202 struct net_device *dev = dst->dev; 203 unsigned int hh_len = LL_RESERVED_SPACE(dev); 204 struct neighbour *neigh; 205 bool is_v6gw = false; 206 207 if (rt->rt_type == RTN_MULTICAST) { 208 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTMCAST, skb->len); 209 } else if (rt->rt_type == RTN_BROADCAST) 210 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len); 211 212 /* OUTOCTETS should be counted after fragment */ 213 IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len); 214 215 if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) { 216 skb = skb_expand_head(skb, hh_len); 217 if (!skb) 218 return -ENOMEM; 219 } 220 221 if (lwtunnel_xmit_redirect(dst->lwtstate)) { 222 int res = lwtunnel_xmit(skb); 223 224 if (res != LWTUNNEL_XMIT_CONTINUE) 225 return res; 226 } 227 228 rcu_read_lock(); 229 neigh = ip_neigh_for_gw(rt, skb, &is_v6gw); 230 if (!IS_ERR(neigh)) { 231 int res; 232 233 sock_confirm_neigh(skb, neigh); 234 /* if crossing protocols, can not use the cached header */ 235 res = neigh_output(neigh, skb, is_v6gw); 236 rcu_read_unlock(); 237 return res; 238 } 239 rcu_read_unlock(); 240 241 net_dbg_ratelimited("%s: No header cache and no neighbour!\n", 242 __func__); 243 kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_CREATEFAIL); 244 return PTR_ERR(neigh); 245 } 246 247 static int ip_finish_output_gso(struct net *net, struct sock *sk, 248 struct sk_buff *skb, unsigned int mtu) 249 { 250 struct sk_buff *segs, *nskb; 251 netdev_features_t features; 252 int ret = 0; 253 254 /* common case: seglen is <= mtu 255 */ 256 if (skb_gso_validate_network_len(skb, mtu)) 257 return ip_finish_output2(net, sk, skb); 258 259 /* Slowpath - GSO segment length exceeds the egress MTU. 260 * 261 * This can happen in several cases: 262 * - Forwarding of a TCP GRO skb, when DF flag is not set. 263 * - Forwarding of an skb that arrived on a virtualization interface 264 * (virtio-net/vhost/tap) with TSO/GSO size set by other network 265 * stack. 266 * - Local GSO skb transmitted on an NETIF_F_TSO tunnel stacked over an 267 * interface with a smaller MTU. 268 * - Arriving GRO skb (or GSO skb in a virtualized environment) that is 269 * bridged to a NETIF_F_TSO tunnel stacked over an interface with an 270 * insufficient MTU. 271 */ 272 features = netif_skb_features(skb); 273 BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_GSO_CB_OFFSET); 274 segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK); 275 if (IS_ERR_OR_NULL(segs)) { 276 kfree_skb(skb); 277 return -ENOMEM; 278 } 279 280 consume_skb(skb); 281 282 skb_list_walk_safe(segs, segs, nskb) { 283 int err; 284 285 skb_mark_not_on_list(segs); 286 err = ip_fragment(net, sk, segs, mtu, ip_finish_output2); 287 288 if (err && ret == 0) 289 ret = err; 290 } 291 292 return ret; 293 } 294 295 static int __ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb) 296 { 297 unsigned int mtu; 298 299 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM) 300 /* Policy lookup after SNAT yielded a new policy */ 301 if (skb_dst(skb)->xfrm) { 302 IPCB(skb)->flags |= IPSKB_REROUTED; 303 return dst_output(net, sk, skb); 304 } 305 #endif 306 mtu = ip_skb_dst_mtu(sk, skb); 307 if (skb_is_gso(skb)) 308 return ip_finish_output_gso(net, sk, skb, mtu); 309 310 if (skb->len > mtu || IPCB(skb)->frag_max_size) 311 return ip_fragment(net, sk, skb, mtu, ip_finish_output2); 312 313 return ip_finish_output2(net, sk, skb); 314 } 315 316 static int ip_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb) 317 { 318 int ret; 319 320 ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb); 321 switch (ret) { 322 case NET_XMIT_SUCCESS: 323 return __ip_finish_output(net, sk, skb); 324 case NET_XMIT_CN: 325 return __ip_finish_output(net, sk, skb) ? : ret; 326 default: 327 kfree_skb_reason(skb, SKB_DROP_REASON_BPF_CGROUP_EGRESS); 328 return ret; 329 } 330 } 331 332 static int ip_mc_finish_output(struct net *net, struct sock *sk, 333 struct sk_buff *skb) 334 { 335 struct rtable *new_rt; 336 bool do_cn = false; 337 int ret, err; 338 339 ret = BPF_CGROUP_RUN_PROG_INET_EGRESS(sk, skb); 340 switch (ret) { 341 case NET_XMIT_CN: 342 do_cn = true; 343 fallthrough; 344 case NET_XMIT_SUCCESS: 345 break; 346 default: 347 kfree_skb_reason(skb, SKB_DROP_REASON_BPF_CGROUP_EGRESS); 348 return ret; 349 } 350 351 /* Reset rt_iif so that inet_iif() will return skb->skb_iif. Setting 352 * this to non-zero causes ipi_ifindex in in_pktinfo to be overwritten, 353 * see ipv4_pktinfo_prepare(). 354 */ 355 new_rt = rt_dst_clone(net->loopback_dev, skb_rtable(skb)); 356 if (new_rt) { 357 new_rt->rt_iif = 0; 358 skb_dst_drop(skb); 359 skb_dst_set(skb, &new_rt->dst); 360 } 361 362 err = dev_loopback_xmit(net, sk, skb); 363 return (do_cn && err) ? ret : err; 364 } 365 366 int ip_mc_output(struct net *net, struct sock *sk, struct sk_buff *skb) 367 { 368 struct rtable *rt = skb_rtable(skb); 369 struct net_device *dev = rt->dst.dev; 370 371 /* 372 * If the indicated interface is up and running, send the packet. 373 */ 374 skb->dev = dev; 375 skb->protocol = htons(ETH_P_IP); 376 377 /* 378 * Multicasts are looped back for other local users 379 */ 380 381 if (rt->rt_flags&RTCF_MULTICAST) { 382 if (sk_mc_loop(sk) 383 #ifdef CONFIG_IP_MROUTE 384 /* Small optimization: do not loopback not local frames, 385 which returned after forwarding; they will be dropped 386 by ip_mr_input in any case. 387 Note, that local frames are looped back to be delivered 388 to local recipients. 389 390 This check is duplicated in ip_mr_input at the moment. 391 */ 392 && 393 ((rt->rt_flags & RTCF_LOCAL) || 394 !(IPCB(skb)->flags & IPSKB_FORWARDED)) 395 #endif 396 ) { 397 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC); 398 if (newskb) 399 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, 400 net, sk, newskb, NULL, newskb->dev, 401 ip_mc_finish_output); 402 } 403 404 /* Multicasts with ttl 0 must not go beyond the host */ 405 406 if (ip_hdr(skb)->ttl == 0) { 407 kfree_skb(skb); 408 return 0; 409 } 410 } 411 412 if (rt->rt_flags&RTCF_BROADCAST) { 413 struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC); 414 if (newskb) 415 NF_HOOK(NFPROTO_IPV4, NF_INET_POST_ROUTING, 416 net, sk, newskb, NULL, newskb->dev, 417 ip_mc_finish_output); 418 } 419 420 return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, 421 net, sk, skb, NULL, skb->dev, 422 ip_finish_output, 423 !(IPCB(skb)->flags & IPSKB_REROUTED)); 424 } 425 426 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb) 427 { 428 struct net_device *dev = skb_dst(skb)->dev, *indev = skb->dev; 429 430 skb->dev = dev; 431 skb->protocol = htons(ETH_P_IP); 432 433 return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING, 434 net, sk, skb, indev, dev, 435 ip_finish_output, 436 !(IPCB(skb)->flags & IPSKB_REROUTED)); 437 } 438 EXPORT_SYMBOL(ip_output); 439 440 /* 441 * copy saddr and daddr, possibly using 64bit load/stores 442 * Equivalent to : 443 * iph->saddr = fl4->saddr; 444 * iph->daddr = fl4->daddr; 445 */ 446 static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4) 447 { 448 BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) != 449 offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr)); 450 451 iph->saddr = fl4->saddr; 452 iph->daddr = fl4->daddr; 453 } 454 455 /* Note: skb->sk can be different from sk, in case of tunnels */ 456 int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl, 457 __u8 tos) 458 { 459 struct inet_sock *inet = inet_sk(sk); 460 struct net *net = sock_net(sk); 461 struct ip_options_rcu *inet_opt; 462 struct flowi4 *fl4; 463 struct rtable *rt; 464 struct iphdr *iph; 465 int res; 466 467 /* Skip all of this if the packet is already routed, 468 * f.e. by something like SCTP. 469 */ 470 rcu_read_lock(); 471 inet_opt = rcu_dereference(inet->inet_opt); 472 fl4 = &fl->u.ip4; 473 rt = skb_rtable(skb); 474 if (rt) 475 goto packet_routed; 476 477 /* Make sure we can route this packet. */ 478 rt = (struct rtable *)__sk_dst_check(sk, 0); 479 if (!rt) { 480 __be32 daddr; 481 482 /* Use correct destination address if we have options. */ 483 daddr = inet->inet_daddr; 484 if (inet_opt && inet_opt->opt.srr) 485 daddr = inet_opt->opt.faddr; 486 487 /* If this fails, retransmit mechanism of transport layer will 488 * keep trying until route appears or the connection times 489 * itself out. 490 */ 491 rt = ip_route_output_ports(net, fl4, sk, 492 daddr, inet->inet_saddr, 493 inet->inet_dport, 494 inet->inet_sport, 495 sk->sk_protocol, 496 RT_CONN_FLAGS_TOS(sk, tos), 497 sk->sk_bound_dev_if); 498 if (IS_ERR(rt)) 499 goto no_route; 500 sk_setup_caps(sk, &rt->dst); 501 } 502 skb_dst_set_noref(skb, &rt->dst); 503 504 packet_routed: 505 if (inet_opt && inet_opt->opt.is_strictroute && rt->rt_uses_gateway) 506 goto no_route; 507 508 /* OK, we know where to send it, allocate and build IP header. */ 509 skb_push(skb, sizeof(struct iphdr) + (inet_opt ? inet_opt->opt.optlen : 0)); 510 skb_reset_network_header(skb); 511 iph = ip_hdr(skb); 512 *((__be16 *)iph) = htons((4 << 12) | (5 << 8) | (tos & 0xff)); 513 if (ip_dont_fragment(sk, &rt->dst) && !skb->ignore_df) 514 iph->frag_off = htons(IP_DF); 515 else 516 iph->frag_off = 0; 517 iph->ttl = ip_select_ttl(inet, &rt->dst); 518 iph->protocol = sk->sk_protocol; 519 ip_copy_addrs(iph, fl4); 520 521 /* Transport layer set skb->h.foo itself. */ 522 523 if (inet_opt && inet_opt->opt.optlen) { 524 iph->ihl += inet_opt->opt.optlen >> 2; 525 ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt); 526 } 527 528 ip_select_ident_segs(net, skb, sk, 529 skb_shinfo(skb)->gso_segs ?: 1); 530 531 /* TODO : should we use skb->sk here instead of sk ? */ 532 skb->priority = READ_ONCE(sk->sk_priority); 533 skb->mark = READ_ONCE(sk->sk_mark); 534 535 res = ip_local_out(net, sk, skb); 536 rcu_read_unlock(); 537 return res; 538 539 no_route: 540 rcu_read_unlock(); 541 IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES); 542 kfree_skb_reason(skb, SKB_DROP_REASON_IP_OUTNOROUTES); 543 return -EHOSTUNREACH; 544 } 545 EXPORT_SYMBOL(__ip_queue_xmit); 546 547 int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl) 548 { 549 return __ip_queue_xmit(sk, skb, fl, READ_ONCE(inet_sk(sk)->tos)); 550 } 551 EXPORT_SYMBOL(ip_queue_xmit); 552 553 static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from) 554 { 555 to->pkt_type = from->pkt_type; 556 to->priority = from->priority; 557 to->protocol = from->protocol; 558 to->skb_iif = from->skb_iif; 559 skb_dst_drop(to); 560 skb_dst_copy(to, from); 561 to->dev = from->dev; 562 to->mark = from->mark; 563 564 skb_copy_hash(to, from); 565 566 #ifdef CONFIG_NET_SCHED 567 to->tc_index = from->tc_index; 568 #endif 569 nf_copy(to, from); 570 skb_ext_copy(to, from); 571 #if IS_ENABLED(CONFIG_IP_VS) 572 to->ipvs_property = from->ipvs_property; 573 #endif 574 skb_copy_secmark(to, from); 575 } 576 577 static int ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, 578 unsigned int mtu, 579 int (*output)(struct net *, struct sock *, struct sk_buff *)) 580 { 581 struct iphdr *iph = ip_hdr(skb); 582 583 if ((iph->frag_off & htons(IP_DF)) == 0) 584 return ip_do_fragment(net, sk, skb, output); 585 586 if (unlikely(!skb->ignore_df || 587 (IPCB(skb)->frag_max_size && 588 IPCB(skb)->frag_max_size > mtu))) { 589 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS); 590 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, 591 htonl(mtu)); 592 kfree_skb(skb); 593 return -EMSGSIZE; 594 } 595 596 return ip_do_fragment(net, sk, skb, output); 597 } 598 599 void ip_fraglist_init(struct sk_buff *skb, struct iphdr *iph, 600 unsigned int hlen, struct ip_fraglist_iter *iter) 601 { 602 unsigned int first_len = skb_pagelen(skb); 603 604 iter->frag = skb_shinfo(skb)->frag_list; 605 skb_frag_list_init(skb); 606 607 iter->offset = 0; 608 iter->iph = iph; 609 iter->hlen = hlen; 610 611 skb->data_len = first_len - skb_headlen(skb); 612 skb->len = first_len; 613 iph->tot_len = htons(first_len); 614 iph->frag_off = htons(IP_MF); 615 ip_send_check(iph); 616 } 617 EXPORT_SYMBOL(ip_fraglist_init); 618 619 void ip_fraglist_prepare(struct sk_buff *skb, struct ip_fraglist_iter *iter) 620 { 621 unsigned int hlen = iter->hlen; 622 struct iphdr *iph = iter->iph; 623 struct sk_buff *frag; 624 625 frag = iter->frag; 626 frag->ip_summed = CHECKSUM_NONE; 627 skb_reset_transport_header(frag); 628 __skb_push(frag, hlen); 629 skb_reset_network_header(frag); 630 memcpy(skb_network_header(frag), iph, hlen); 631 iter->iph = ip_hdr(frag); 632 iph = iter->iph; 633 iph->tot_len = htons(frag->len); 634 ip_copy_metadata(frag, skb); 635 iter->offset += skb->len - hlen; 636 iph->frag_off = htons(iter->offset >> 3); 637 if (frag->next) 638 iph->frag_off |= htons(IP_MF); 639 /* Ready, complete checksum */ 640 ip_send_check(iph); 641 } 642 EXPORT_SYMBOL(ip_fraglist_prepare); 643 644 void ip_frag_init(struct sk_buff *skb, unsigned int hlen, 645 unsigned int ll_rs, unsigned int mtu, bool DF, 646 struct ip_frag_state *state) 647 { 648 struct iphdr *iph = ip_hdr(skb); 649 650 state->DF = DF; 651 state->hlen = hlen; 652 state->ll_rs = ll_rs; 653 state->mtu = mtu; 654 655 state->left = skb->len - hlen; /* Space per frame */ 656 state->ptr = hlen; /* Where to start from */ 657 658 state->offset = (ntohs(iph->frag_off) & IP_OFFSET) << 3; 659 state->not_last_frag = iph->frag_off & htons(IP_MF); 660 } 661 EXPORT_SYMBOL(ip_frag_init); 662 663 static void ip_frag_ipcb(struct sk_buff *from, struct sk_buff *to, 664 bool first_frag) 665 { 666 /* Copy the flags to each fragment. */ 667 IPCB(to)->flags = IPCB(from)->flags; 668 669 /* ANK: dirty, but effective trick. Upgrade options only if 670 * the segment to be fragmented was THE FIRST (otherwise, 671 * options are already fixed) and make it ONCE 672 * on the initial skb, so that all the following fragments 673 * will inherit fixed options. 674 */ 675 if (first_frag) 676 ip_options_fragment(from); 677 } 678 679 struct sk_buff *ip_frag_next(struct sk_buff *skb, struct ip_frag_state *state) 680 { 681 unsigned int len = state->left; 682 struct sk_buff *skb2; 683 struct iphdr *iph; 684 685 /* IF: it doesn't fit, use 'mtu' - the data space left */ 686 if (len > state->mtu) 687 len = state->mtu; 688 /* IF: we are not sending up to and including the packet end 689 then align the next start on an eight byte boundary */ 690 if (len < state->left) { 691 len &= ~7; 692 } 693 694 /* Allocate buffer */ 695 skb2 = alloc_skb(len + state->hlen + state->ll_rs, GFP_ATOMIC); 696 if (!skb2) 697 return ERR_PTR(-ENOMEM); 698 699 /* 700 * Set up data on packet 701 */ 702 703 ip_copy_metadata(skb2, skb); 704 skb_reserve(skb2, state->ll_rs); 705 skb_put(skb2, len + state->hlen); 706 skb_reset_network_header(skb2); 707 skb2->transport_header = skb2->network_header + state->hlen; 708 709 /* 710 * Charge the memory for the fragment to any owner 711 * it might possess 712 */ 713 714 if (skb->sk) 715 skb_set_owner_w(skb2, skb->sk); 716 717 /* 718 * Copy the packet header into the new buffer. 719 */ 720 721 skb_copy_from_linear_data(skb, skb_network_header(skb2), state->hlen); 722 723 /* 724 * Copy a block of the IP datagram. 725 */ 726 if (skb_copy_bits(skb, state->ptr, skb_transport_header(skb2), len)) 727 BUG(); 728 state->left -= len; 729 730 /* 731 * Fill in the new header fields. 732 */ 733 iph = ip_hdr(skb2); 734 iph->frag_off = htons((state->offset >> 3)); 735 if (state->DF) 736 iph->frag_off |= htons(IP_DF); 737 738 /* 739 * Added AC : If we are fragmenting a fragment that's not the 740 * last fragment then keep MF on each bit 741 */ 742 if (state->left > 0 || state->not_last_frag) 743 iph->frag_off |= htons(IP_MF); 744 state->ptr += len; 745 state->offset += len; 746 747 iph->tot_len = htons(len + state->hlen); 748 749 ip_send_check(iph); 750 751 return skb2; 752 } 753 EXPORT_SYMBOL(ip_frag_next); 754 755 /* 756 * This IP datagram is too large to be sent in one piece. Break it up into 757 * smaller pieces (each of size equal to IP header plus 758 * a block of the data of the original IP data part) that will yet fit in a 759 * single device frame, and queue such a frame for sending. 760 */ 761 762 int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, 763 int (*output)(struct net *, struct sock *, struct sk_buff *)) 764 { 765 struct iphdr *iph; 766 struct sk_buff *skb2; 767 bool mono_delivery_time = skb->mono_delivery_time; 768 struct rtable *rt = skb_rtable(skb); 769 unsigned int mtu, hlen, ll_rs; 770 struct ip_fraglist_iter iter; 771 ktime_t tstamp = skb->tstamp; 772 struct ip_frag_state state; 773 int err = 0; 774 775 /* for offloaded checksums cleanup checksum before fragmentation */ 776 if (skb->ip_summed == CHECKSUM_PARTIAL && 777 (err = skb_checksum_help(skb))) 778 goto fail; 779 780 /* 781 * Point into the IP datagram header. 782 */ 783 784 iph = ip_hdr(skb); 785 786 mtu = ip_skb_dst_mtu(sk, skb); 787 if (IPCB(skb)->frag_max_size && IPCB(skb)->frag_max_size < mtu) 788 mtu = IPCB(skb)->frag_max_size; 789 790 /* 791 * Setup starting values. 792 */ 793 794 hlen = iph->ihl * 4; 795 mtu = mtu - hlen; /* Size of data space */ 796 IPCB(skb)->flags |= IPSKB_FRAG_COMPLETE; 797 ll_rs = LL_RESERVED_SPACE(rt->dst.dev); 798 799 /* When frag_list is given, use it. First, check its validity: 800 * some transformers could create wrong frag_list or break existing 801 * one, it is not prohibited. In this case fall back to copying. 802 * 803 * LATER: this step can be merged to real generation of fragments, 804 * we can switch to copy when see the first bad fragment. 805 */ 806 if (skb_has_frag_list(skb)) { 807 struct sk_buff *frag, *frag2; 808 unsigned int first_len = skb_pagelen(skb); 809 810 if (first_len - hlen > mtu || 811 ((first_len - hlen) & 7) || 812 ip_is_fragment(iph) || 813 skb_cloned(skb) || 814 skb_headroom(skb) < ll_rs) 815 goto slow_path; 816 817 skb_walk_frags(skb, frag) { 818 /* Correct geometry. */ 819 if (frag->len > mtu || 820 ((frag->len & 7) && frag->next) || 821 skb_headroom(frag) < hlen + ll_rs) 822 goto slow_path_clean; 823 824 /* Partially cloned skb? */ 825 if (skb_shared(frag)) 826 goto slow_path_clean; 827 828 BUG_ON(frag->sk); 829 if (skb->sk) { 830 frag->sk = skb->sk; 831 frag->destructor = sock_wfree; 832 } 833 skb->truesize -= frag->truesize; 834 } 835 836 /* Everything is OK. Generate! */ 837 ip_fraglist_init(skb, iph, hlen, &iter); 838 839 for (;;) { 840 /* Prepare header of the next frame, 841 * before previous one went down. */ 842 if (iter.frag) { 843 bool first_frag = (iter.offset == 0); 844 845 IPCB(iter.frag)->flags = IPCB(skb)->flags; 846 ip_fraglist_prepare(skb, &iter); 847 if (first_frag && IPCB(skb)->opt.optlen) { 848 /* ipcb->opt is not populated for frags 849 * coming from __ip_make_skb(), 850 * ip_options_fragment() needs optlen 851 */ 852 IPCB(iter.frag)->opt.optlen = 853 IPCB(skb)->opt.optlen; 854 ip_options_fragment(iter.frag); 855 ip_send_check(iter.iph); 856 } 857 } 858 859 skb_set_delivery_time(skb, tstamp, mono_delivery_time); 860 err = output(net, sk, skb); 861 862 if (!err) 863 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES); 864 if (err || !iter.frag) 865 break; 866 867 skb = ip_fraglist_next(&iter); 868 } 869 870 if (err == 0) { 871 IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS); 872 return 0; 873 } 874 875 kfree_skb_list(iter.frag); 876 877 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS); 878 return err; 879 880 slow_path_clean: 881 skb_walk_frags(skb, frag2) { 882 if (frag2 == frag) 883 break; 884 frag2->sk = NULL; 885 frag2->destructor = NULL; 886 skb->truesize += frag2->truesize; 887 } 888 } 889 890 slow_path: 891 /* 892 * Fragment the datagram. 893 */ 894 895 ip_frag_init(skb, hlen, ll_rs, mtu, IPCB(skb)->flags & IPSKB_FRAG_PMTU, 896 &state); 897 898 /* 899 * Keep copying data until we run out. 900 */ 901 902 while (state.left > 0) { 903 bool first_frag = (state.offset == 0); 904 905 skb2 = ip_frag_next(skb, &state); 906 if (IS_ERR(skb2)) { 907 err = PTR_ERR(skb2); 908 goto fail; 909 } 910 ip_frag_ipcb(skb, skb2, first_frag); 911 912 /* 913 * Put this fragment into the sending queue. 914 */ 915 skb_set_delivery_time(skb2, tstamp, mono_delivery_time); 916 err = output(net, sk, skb2); 917 if (err) 918 goto fail; 919 920 IP_INC_STATS(net, IPSTATS_MIB_FRAGCREATES); 921 } 922 consume_skb(skb); 923 IP_INC_STATS(net, IPSTATS_MIB_FRAGOKS); 924 return err; 925 926 fail: 927 kfree_skb(skb); 928 IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS); 929 return err; 930 } 931 EXPORT_SYMBOL(ip_do_fragment); 932 933 int 934 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb) 935 { 936 struct msghdr *msg = from; 937 938 if (skb->ip_summed == CHECKSUM_PARTIAL) { 939 if (!copy_from_iter_full(to, len, &msg->msg_iter)) 940 return -EFAULT; 941 } else { 942 __wsum csum = 0; 943 if (!csum_and_copy_from_iter_full(to, len, &csum, &msg->msg_iter)) 944 return -EFAULT; 945 skb->csum = csum_block_add(skb->csum, csum, odd); 946 } 947 return 0; 948 } 949 EXPORT_SYMBOL(ip_generic_getfrag); 950 951 static int __ip_append_data(struct sock *sk, 952 struct flowi4 *fl4, 953 struct sk_buff_head *queue, 954 struct inet_cork *cork, 955 struct page_frag *pfrag, 956 int getfrag(void *from, char *to, int offset, 957 int len, int odd, struct sk_buff *skb), 958 void *from, int length, int transhdrlen, 959 unsigned int flags) 960 { 961 struct inet_sock *inet = inet_sk(sk); 962 struct ubuf_info *uarg = NULL; 963 struct sk_buff *skb; 964 struct ip_options *opt = cork->opt; 965 int hh_len; 966 int exthdrlen; 967 int mtu; 968 int copy; 969 int err; 970 int offset = 0; 971 bool zc = false; 972 unsigned int maxfraglen, fragheaderlen, maxnonfragsize; 973 int csummode = CHECKSUM_NONE; 974 struct rtable *rt = (struct rtable *)cork->dst; 975 unsigned int wmem_alloc_delta = 0; 976 bool paged, extra_uref = false; 977 u32 tskey = 0; 978 979 skb = skb_peek_tail(queue); 980 981 exthdrlen = !skb ? rt->dst.header_len : 0; 982 mtu = cork->gso_size ? IP_MAX_MTU : cork->fragsize; 983 paged = !!cork->gso_size; 984 985 if (cork->tx_flags & SKBTX_ANY_TSTAMP && 986 READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_OPT_ID) 987 tskey = atomic_inc_return(&sk->sk_tskey) - 1; 988 989 hh_len = LL_RESERVED_SPACE(rt->dst.dev); 990 991 fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0); 992 maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen; 993 maxnonfragsize = ip_sk_ignore_df(sk) ? IP_MAX_MTU : mtu; 994 995 if (cork->length + length > maxnonfragsize - fragheaderlen) { 996 ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport, 997 mtu - (opt ? opt->optlen : 0)); 998 return -EMSGSIZE; 999 } 1000 1001 /* 1002 * transhdrlen > 0 means that this is the first fragment and we wish 1003 * it won't be fragmented in the future. 1004 */ 1005 if (transhdrlen && 1006 length + fragheaderlen <= mtu && 1007 rt->dst.dev->features & (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM) && 1008 (!(flags & MSG_MORE) || cork->gso_size) && 1009 (!exthdrlen || (rt->dst.dev->features & NETIF_F_HW_ESP_TX_CSUM))) 1010 csummode = CHECKSUM_PARTIAL; 1011 1012 if ((flags & MSG_ZEROCOPY) && length) { 1013 struct msghdr *msg = from; 1014 1015 if (getfrag == ip_generic_getfrag && msg->msg_ubuf) { 1016 if (skb_zcopy(skb) && msg->msg_ubuf != skb_zcopy(skb)) 1017 return -EINVAL; 1018 1019 /* Leave uarg NULL if can't zerocopy, callers should 1020 * be able to handle it. 1021 */ 1022 if ((rt->dst.dev->features & NETIF_F_SG) && 1023 csummode == CHECKSUM_PARTIAL) { 1024 paged = true; 1025 zc = true; 1026 uarg = msg->msg_ubuf; 1027 } 1028 } else if (sock_flag(sk, SOCK_ZEROCOPY)) { 1029 uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb)); 1030 if (!uarg) 1031 return -ENOBUFS; 1032 extra_uref = !skb_zcopy(skb); /* only ref on new uarg */ 1033 if (rt->dst.dev->features & NETIF_F_SG && 1034 csummode == CHECKSUM_PARTIAL) { 1035 paged = true; 1036 zc = true; 1037 } else { 1038 uarg_to_msgzc(uarg)->zerocopy = 0; 1039 skb_zcopy_set(skb, uarg, &extra_uref); 1040 } 1041 } 1042 } else if ((flags & MSG_SPLICE_PAGES) && length) { 1043 if (inet_test_bit(HDRINCL, sk)) 1044 return -EPERM; 1045 if (rt->dst.dev->features & NETIF_F_SG && 1046 getfrag == ip_generic_getfrag) 1047 /* We need an empty buffer to attach stuff to */ 1048 paged = true; 1049 else 1050 flags &= ~MSG_SPLICE_PAGES; 1051 } 1052 1053 cork->length += length; 1054 1055 /* So, what's going on in the loop below? 1056 * 1057 * We use calculated fragment length to generate chained skb, 1058 * each of segments is IP fragment ready for sending to network after 1059 * adding appropriate IP header. 1060 */ 1061 1062 if (!skb) 1063 goto alloc_new_skb; 1064 1065 while (length > 0) { 1066 /* Check if the remaining data fits into current packet. */ 1067 copy = mtu - skb->len; 1068 if (copy < length) 1069 copy = maxfraglen - skb->len; 1070 if (copy <= 0) { 1071 char *data; 1072 unsigned int datalen; 1073 unsigned int fraglen; 1074 unsigned int fraggap; 1075 unsigned int alloclen, alloc_extra; 1076 unsigned int pagedlen; 1077 struct sk_buff *skb_prev; 1078 alloc_new_skb: 1079 skb_prev = skb; 1080 if (skb_prev) 1081 fraggap = skb_prev->len - maxfraglen; 1082 else 1083 fraggap = 0; 1084 1085 /* 1086 * If remaining data exceeds the mtu, 1087 * we know we need more fragment(s). 1088 */ 1089 datalen = length + fraggap; 1090 if (datalen > mtu - fragheaderlen) 1091 datalen = maxfraglen - fragheaderlen; 1092 fraglen = datalen + fragheaderlen; 1093 pagedlen = 0; 1094 1095 alloc_extra = hh_len + 15; 1096 alloc_extra += exthdrlen; 1097 1098 /* The last fragment gets additional space at tail. 1099 * Note, with MSG_MORE we overallocate on fragments, 1100 * because we have no idea what fragment will be 1101 * the last. 1102 */ 1103 if (datalen == length + fraggap) 1104 alloc_extra += rt->dst.trailer_len; 1105 1106 if ((flags & MSG_MORE) && 1107 !(rt->dst.dev->features&NETIF_F_SG)) 1108 alloclen = mtu; 1109 else if (!paged && 1110 (fraglen + alloc_extra < SKB_MAX_ALLOC || 1111 !(rt->dst.dev->features & NETIF_F_SG))) 1112 alloclen = fraglen; 1113 else { 1114 alloclen = fragheaderlen + transhdrlen; 1115 pagedlen = datalen - transhdrlen; 1116 } 1117 1118 alloclen += alloc_extra; 1119 1120 if (transhdrlen) { 1121 skb = sock_alloc_send_skb(sk, alloclen, 1122 (flags & MSG_DONTWAIT), &err); 1123 } else { 1124 skb = NULL; 1125 if (refcount_read(&sk->sk_wmem_alloc) + wmem_alloc_delta <= 1126 2 * sk->sk_sndbuf) 1127 skb = alloc_skb(alloclen, 1128 sk->sk_allocation); 1129 if (unlikely(!skb)) 1130 err = -ENOBUFS; 1131 } 1132 if (!skb) 1133 goto error; 1134 1135 /* 1136 * Fill in the control structures 1137 */ 1138 skb->ip_summed = csummode; 1139 skb->csum = 0; 1140 skb_reserve(skb, hh_len); 1141 1142 /* 1143 * Find where to start putting bytes. 1144 */ 1145 data = skb_put(skb, fraglen + exthdrlen - pagedlen); 1146 skb_set_network_header(skb, exthdrlen); 1147 skb->transport_header = (skb->network_header + 1148 fragheaderlen); 1149 data += fragheaderlen + exthdrlen; 1150 1151 if (fraggap) { 1152 skb->csum = skb_copy_and_csum_bits( 1153 skb_prev, maxfraglen, 1154 data + transhdrlen, fraggap); 1155 skb_prev->csum = csum_sub(skb_prev->csum, 1156 skb->csum); 1157 data += fraggap; 1158 pskb_trim_unique(skb_prev, maxfraglen); 1159 } 1160 1161 copy = datalen - transhdrlen - fraggap - pagedlen; 1162 /* [!] NOTE: copy will be negative if pagedlen>0 1163 * because then the equation reduces to -fraggap. 1164 */ 1165 if (copy > 0 && getfrag(from, data + transhdrlen, offset, copy, fraggap, skb) < 0) { 1166 err = -EFAULT; 1167 kfree_skb(skb); 1168 goto error; 1169 } else if (flags & MSG_SPLICE_PAGES) { 1170 copy = 0; 1171 } 1172 1173 offset += copy; 1174 length -= copy + transhdrlen; 1175 transhdrlen = 0; 1176 exthdrlen = 0; 1177 csummode = CHECKSUM_NONE; 1178 1179 /* only the initial fragment is time stamped */ 1180 skb_shinfo(skb)->tx_flags = cork->tx_flags; 1181 cork->tx_flags = 0; 1182 skb_shinfo(skb)->tskey = tskey; 1183 tskey = 0; 1184 skb_zcopy_set(skb, uarg, &extra_uref); 1185 1186 if ((flags & MSG_CONFIRM) && !skb_prev) 1187 skb_set_dst_pending_confirm(skb, 1); 1188 1189 /* 1190 * Put the packet on the pending queue. 1191 */ 1192 if (!skb->destructor) { 1193 skb->destructor = sock_wfree; 1194 skb->sk = sk; 1195 wmem_alloc_delta += skb->truesize; 1196 } 1197 __skb_queue_tail(queue, skb); 1198 continue; 1199 } 1200 1201 if (copy > length) 1202 copy = length; 1203 1204 if (!(rt->dst.dev->features&NETIF_F_SG) && 1205 skb_tailroom(skb) >= copy) { 1206 unsigned int off; 1207 1208 off = skb->len; 1209 if (getfrag(from, skb_put(skb, copy), 1210 offset, copy, off, skb) < 0) { 1211 __skb_trim(skb, off); 1212 err = -EFAULT; 1213 goto error; 1214 } 1215 } else if (flags & MSG_SPLICE_PAGES) { 1216 struct msghdr *msg = from; 1217 1218 err = -EIO; 1219 if (WARN_ON_ONCE(copy > msg->msg_iter.count)) 1220 goto error; 1221 1222 err = skb_splice_from_iter(skb, &msg->msg_iter, copy, 1223 sk->sk_allocation); 1224 if (err < 0) 1225 goto error; 1226 copy = err; 1227 wmem_alloc_delta += copy; 1228 } else if (!zc) { 1229 int i = skb_shinfo(skb)->nr_frags; 1230 1231 err = -ENOMEM; 1232 if (!sk_page_frag_refill(sk, pfrag)) 1233 goto error; 1234 1235 skb_zcopy_downgrade_managed(skb); 1236 if (!skb_can_coalesce(skb, i, pfrag->page, 1237 pfrag->offset)) { 1238 err = -EMSGSIZE; 1239 if (i == MAX_SKB_FRAGS) 1240 goto error; 1241 1242 __skb_fill_page_desc(skb, i, pfrag->page, 1243 pfrag->offset, 0); 1244 skb_shinfo(skb)->nr_frags = ++i; 1245 get_page(pfrag->page); 1246 } 1247 copy = min_t(int, copy, pfrag->size - pfrag->offset); 1248 if (getfrag(from, 1249 page_address(pfrag->page) + pfrag->offset, 1250 offset, copy, skb->len, skb) < 0) 1251 goto error_efault; 1252 1253 pfrag->offset += copy; 1254 skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy); 1255 skb_len_add(skb, copy); 1256 wmem_alloc_delta += copy; 1257 } else { 1258 err = skb_zerocopy_iter_dgram(skb, from, copy); 1259 if (err < 0) 1260 goto error; 1261 } 1262 offset += copy; 1263 length -= copy; 1264 } 1265 1266 if (wmem_alloc_delta) 1267 refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc); 1268 return 0; 1269 1270 error_efault: 1271 err = -EFAULT; 1272 error: 1273 net_zcopy_put_abort(uarg, extra_uref); 1274 cork->length -= length; 1275 IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTDISCARDS); 1276 refcount_add(wmem_alloc_delta, &sk->sk_wmem_alloc); 1277 return err; 1278 } 1279 1280 static int ip_setup_cork(struct sock *sk, struct inet_cork *cork, 1281 struct ipcm_cookie *ipc, struct rtable **rtp) 1282 { 1283 struct ip_options_rcu *opt; 1284 struct rtable *rt; 1285 1286 rt = *rtp; 1287 if (unlikely(!rt)) 1288 return -EFAULT; 1289 1290 /* 1291 * setup for corking. 1292 */ 1293 opt = ipc->opt; 1294 if (opt) { 1295 if (!cork->opt) { 1296 cork->opt = kmalloc(sizeof(struct ip_options) + 40, 1297 sk->sk_allocation); 1298 if (unlikely(!cork->opt)) 1299 return -ENOBUFS; 1300 } 1301 memcpy(cork->opt, &opt->opt, sizeof(struct ip_options) + opt->opt.optlen); 1302 cork->flags |= IPCORK_OPT; 1303 cork->addr = ipc->addr; 1304 } 1305 1306 cork->fragsize = ip_sk_use_pmtu(sk) ? 1307 dst_mtu(&rt->dst) : READ_ONCE(rt->dst.dev->mtu); 1308 1309 if (!inetdev_valid_mtu(cork->fragsize)) 1310 return -ENETUNREACH; 1311 1312 cork->gso_size = ipc->gso_size; 1313 1314 cork->dst = &rt->dst; 1315 /* We stole this route, caller should not release it. */ 1316 *rtp = NULL; 1317 1318 cork->length = 0; 1319 cork->ttl = ipc->ttl; 1320 cork->tos = ipc->tos; 1321 cork->mark = ipc->sockc.mark; 1322 cork->priority = ipc->priority; 1323 cork->transmit_time = ipc->sockc.transmit_time; 1324 cork->tx_flags = 0; 1325 sock_tx_timestamp(sk, ipc->sockc.tsflags, &cork->tx_flags); 1326 1327 return 0; 1328 } 1329 1330 /* 1331 * ip_append_data() can make one large IP datagram from many pieces of 1332 * data. Each piece will be held on the socket until 1333 * ip_push_pending_frames() is called. Each piece can be a page or 1334 * non-page data. 1335 * 1336 * Not only UDP, other transport protocols - e.g. raw sockets - can use 1337 * this interface potentially. 1338 * 1339 * LATER: length must be adjusted by pad at tail, when it is required. 1340 */ 1341 int ip_append_data(struct sock *sk, struct flowi4 *fl4, 1342 int getfrag(void *from, char *to, int offset, int len, 1343 int odd, struct sk_buff *skb), 1344 void *from, int length, int transhdrlen, 1345 struct ipcm_cookie *ipc, struct rtable **rtp, 1346 unsigned int flags) 1347 { 1348 struct inet_sock *inet = inet_sk(sk); 1349 int err; 1350 1351 if (flags&MSG_PROBE) 1352 return 0; 1353 1354 if (skb_queue_empty(&sk->sk_write_queue)) { 1355 err = ip_setup_cork(sk, &inet->cork.base, ipc, rtp); 1356 if (err) 1357 return err; 1358 } else { 1359 transhdrlen = 0; 1360 } 1361 1362 return __ip_append_data(sk, fl4, &sk->sk_write_queue, &inet->cork.base, 1363 sk_page_frag(sk), getfrag, 1364 from, length, transhdrlen, flags); 1365 } 1366 1367 static void ip_cork_release(struct inet_cork *cork) 1368 { 1369 cork->flags &= ~IPCORK_OPT; 1370 kfree(cork->opt); 1371 cork->opt = NULL; 1372 dst_release(cork->dst); 1373 cork->dst = NULL; 1374 } 1375 1376 /* 1377 * Combined all pending IP fragments on the socket as one IP datagram 1378 * and push them out. 1379 */ 1380 struct sk_buff *__ip_make_skb(struct sock *sk, 1381 struct flowi4 *fl4, 1382 struct sk_buff_head *queue, 1383 struct inet_cork *cork) 1384 { 1385 struct sk_buff *skb, *tmp_skb; 1386 struct sk_buff **tail_skb; 1387 struct inet_sock *inet = inet_sk(sk); 1388 struct net *net = sock_net(sk); 1389 struct ip_options *opt = NULL; 1390 struct rtable *rt = (struct rtable *)cork->dst; 1391 struct iphdr *iph; 1392 u8 pmtudisc, ttl; 1393 __be16 df = 0; 1394 1395 skb = __skb_dequeue(queue); 1396 if (!skb) 1397 goto out; 1398 tail_skb = &(skb_shinfo(skb)->frag_list); 1399 1400 /* move skb->data to ip header from ext header */ 1401 if (skb->data < skb_network_header(skb)) 1402 __skb_pull(skb, skb_network_offset(skb)); 1403 while ((tmp_skb = __skb_dequeue(queue)) != NULL) { 1404 __skb_pull(tmp_skb, skb_network_header_len(skb)); 1405 *tail_skb = tmp_skb; 1406 tail_skb = &(tmp_skb->next); 1407 skb->len += tmp_skb->len; 1408 skb->data_len += tmp_skb->len; 1409 skb->truesize += tmp_skb->truesize; 1410 tmp_skb->destructor = NULL; 1411 tmp_skb->sk = NULL; 1412 } 1413 1414 /* Unless user demanded real pmtu discovery (IP_PMTUDISC_DO), we allow 1415 * to fragment the frame generated here. No matter, what transforms 1416 * how transforms change size of the packet, it will come out. 1417 */ 1418 skb->ignore_df = ip_sk_ignore_df(sk); 1419 1420 /* DF bit is set when we want to see DF on outgoing frames. 1421 * If ignore_df is set too, we still allow to fragment this frame 1422 * locally. */ 1423 pmtudisc = READ_ONCE(inet->pmtudisc); 1424 if (pmtudisc == IP_PMTUDISC_DO || 1425 pmtudisc == IP_PMTUDISC_PROBE || 1426 (skb->len <= dst_mtu(&rt->dst) && 1427 ip_dont_fragment(sk, &rt->dst))) 1428 df = htons(IP_DF); 1429 1430 if (cork->flags & IPCORK_OPT) 1431 opt = cork->opt; 1432 1433 if (cork->ttl != 0) 1434 ttl = cork->ttl; 1435 else if (rt->rt_type == RTN_MULTICAST) 1436 ttl = READ_ONCE(inet->mc_ttl); 1437 else 1438 ttl = ip_select_ttl(inet, &rt->dst); 1439 1440 iph = ip_hdr(skb); 1441 iph->version = 4; 1442 iph->ihl = 5; 1443 iph->tos = (cork->tos != -1) ? cork->tos : READ_ONCE(inet->tos); 1444 iph->frag_off = df; 1445 iph->ttl = ttl; 1446 iph->protocol = sk->sk_protocol; 1447 ip_copy_addrs(iph, fl4); 1448 ip_select_ident(net, skb, sk); 1449 1450 if (opt) { 1451 iph->ihl += opt->optlen >> 2; 1452 ip_options_build(skb, opt, cork->addr, rt); 1453 } 1454 1455 skb->priority = (cork->tos != -1) ? cork->priority: READ_ONCE(sk->sk_priority); 1456 skb->mark = cork->mark; 1457 skb->tstamp = cork->transmit_time; 1458 /* 1459 * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec 1460 * on dst refcount 1461 */ 1462 cork->dst = NULL; 1463 skb_dst_set(skb, &rt->dst); 1464 1465 if (iph->protocol == IPPROTO_ICMP) { 1466 u8 icmp_type; 1467 1468 /* For such sockets, transhdrlen is zero when do ip_append_data(), 1469 * so icmphdr does not in skb linear region and can not get icmp_type 1470 * by icmp_hdr(skb)->type. 1471 */ 1472 if (sk->sk_type == SOCK_RAW && 1473 !inet_test_bit(HDRINCL, sk)) 1474 icmp_type = fl4->fl4_icmp_type; 1475 else 1476 icmp_type = icmp_hdr(skb)->type; 1477 icmp_out_count(net, icmp_type); 1478 } 1479 1480 ip_cork_release(cork); 1481 out: 1482 return skb; 1483 } 1484 1485 int ip_send_skb(struct net *net, struct sk_buff *skb) 1486 { 1487 int err; 1488 1489 err = ip_local_out(net, skb->sk, skb); 1490 if (err) { 1491 if (err > 0) 1492 err = net_xmit_errno(err); 1493 if (err) 1494 IP_INC_STATS(net, IPSTATS_MIB_OUTDISCARDS); 1495 } 1496 1497 return err; 1498 } 1499 1500 int ip_push_pending_frames(struct sock *sk, struct flowi4 *fl4) 1501 { 1502 struct sk_buff *skb; 1503 1504 skb = ip_finish_skb(sk, fl4); 1505 if (!skb) 1506 return 0; 1507 1508 /* Netfilter gets whole the not fragmented skb. */ 1509 return ip_send_skb(sock_net(sk), skb); 1510 } 1511 1512 /* 1513 * Throw away all pending data on the socket. 1514 */ 1515 static void __ip_flush_pending_frames(struct sock *sk, 1516 struct sk_buff_head *queue, 1517 struct inet_cork *cork) 1518 { 1519 struct sk_buff *skb; 1520 1521 while ((skb = __skb_dequeue_tail(queue)) != NULL) 1522 kfree_skb(skb); 1523 1524 ip_cork_release(cork); 1525 } 1526 1527 void ip_flush_pending_frames(struct sock *sk) 1528 { 1529 __ip_flush_pending_frames(sk, &sk->sk_write_queue, &inet_sk(sk)->cork.base); 1530 } 1531 1532 struct sk_buff *ip_make_skb(struct sock *sk, 1533 struct flowi4 *fl4, 1534 int getfrag(void *from, char *to, int offset, 1535 int len, int odd, struct sk_buff *skb), 1536 void *from, int length, int transhdrlen, 1537 struct ipcm_cookie *ipc, struct rtable **rtp, 1538 struct inet_cork *cork, unsigned int flags) 1539 { 1540 struct sk_buff_head queue; 1541 int err; 1542 1543 if (flags & MSG_PROBE) 1544 return NULL; 1545 1546 __skb_queue_head_init(&queue); 1547 1548 cork->flags = 0; 1549 cork->addr = 0; 1550 cork->opt = NULL; 1551 err = ip_setup_cork(sk, cork, ipc, rtp); 1552 if (err) 1553 return ERR_PTR(err); 1554 1555 err = __ip_append_data(sk, fl4, &queue, cork, 1556 ¤t->task_frag, getfrag, 1557 from, length, transhdrlen, flags); 1558 if (err) { 1559 __ip_flush_pending_frames(sk, &queue, cork); 1560 return ERR_PTR(err); 1561 } 1562 1563 return __ip_make_skb(sk, fl4, &queue, cork); 1564 } 1565 1566 /* 1567 * Fetch data from kernel space and fill in checksum if needed. 1568 */ 1569 static int ip_reply_glue_bits(void *dptr, char *to, int offset, 1570 int len, int odd, struct sk_buff *skb) 1571 { 1572 __wsum csum; 1573 1574 csum = csum_partial_copy_nocheck(dptr+offset, to, len); 1575 skb->csum = csum_block_add(skb->csum, csum, odd); 1576 return 0; 1577 } 1578 1579 /* 1580 * Generic function to send a packet as reply to another packet. 1581 * Used to send some TCP resets/acks so far. 1582 */ 1583 void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb, 1584 const struct ip_options *sopt, 1585 __be32 daddr, __be32 saddr, 1586 const struct ip_reply_arg *arg, 1587 unsigned int len, u64 transmit_time, u32 txhash) 1588 { 1589 struct ip_options_data replyopts; 1590 struct ipcm_cookie ipc; 1591 struct flowi4 fl4; 1592 struct rtable *rt = skb_rtable(skb); 1593 struct net *net = sock_net(sk); 1594 struct sk_buff *nskb; 1595 int err; 1596 int oif; 1597 1598 if (__ip_options_echo(net, &replyopts.opt.opt, skb, sopt)) 1599 return; 1600 1601 ipcm_init(&ipc); 1602 ipc.addr = daddr; 1603 ipc.sockc.transmit_time = transmit_time; 1604 1605 if (replyopts.opt.opt.optlen) { 1606 ipc.opt = &replyopts.opt; 1607 1608 if (replyopts.opt.opt.srr) 1609 daddr = replyopts.opt.opt.faddr; 1610 } 1611 1612 oif = arg->bound_dev_if; 1613 if (!oif && netif_index_is_l3_master(net, skb->skb_iif)) 1614 oif = skb->skb_iif; 1615 1616 flowi4_init_output(&fl4, oif, 1617 IP4_REPLY_MARK(net, skb->mark) ?: sk->sk_mark, 1618 RT_TOS(arg->tos), 1619 RT_SCOPE_UNIVERSE, ip_hdr(skb)->protocol, 1620 ip_reply_arg_flowi_flags(arg), 1621 daddr, saddr, 1622 tcp_hdr(skb)->source, tcp_hdr(skb)->dest, 1623 arg->uid); 1624 security_skb_classify_flow(skb, flowi4_to_flowi_common(&fl4)); 1625 rt = ip_route_output_flow(net, &fl4, sk); 1626 if (IS_ERR(rt)) 1627 return; 1628 1629 inet_sk(sk)->tos = arg->tos & ~INET_ECN_MASK; 1630 1631 sk->sk_protocol = ip_hdr(skb)->protocol; 1632 sk->sk_bound_dev_if = arg->bound_dev_if; 1633 sk->sk_sndbuf = READ_ONCE(sysctl_wmem_default); 1634 ipc.sockc.mark = fl4.flowi4_mark; 1635 err = ip_append_data(sk, &fl4, ip_reply_glue_bits, arg->iov->iov_base, 1636 len, 0, &ipc, &rt, MSG_DONTWAIT); 1637 if (unlikely(err)) { 1638 ip_flush_pending_frames(sk); 1639 goto out; 1640 } 1641 1642 nskb = skb_peek(&sk->sk_write_queue); 1643 if (nskb) { 1644 if (arg->csumoffset >= 0) 1645 *((__sum16 *)skb_transport_header(nskb) + 1646 arg->csumoffset) = csum_fold(csum_add(nskb->csum, 1647 arg->csum)); 1648 nskb->ip_summed = CHECKSUM_NONE; 1649 nskb->mono_delivery_time = !!transmit_time; 1650 if (txhash) 1651 skb_set_hash(nskb, txhash, PKT_HASH_TYPE_L4); 1652 ip_push_pending_frames(sk, &fl4); 1653 } 1654 out: 1655 ip_rt_put(rt); 1656 } 1657 1658 void __init ip_init(void) 1659 { 1660 ip_rt_init(); 1661 inet_initpeers(); 1662 1663 #if defined(CONFIG_IP_MULTICAST) 1664 igmp_mc_init(); 1665 #endif 1666 } 1667