1 /* 2 * INET An implementation of the TCP/IP protocol suite for the LINUX 3 * operating system. INET is implemented using the BSD Socket 4 * interface as the means of communication with the user level. 5 * 6 * The Internet Protocol (IP) module. 7 * 8 * Authors: Ross Biro 9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 10 * Donald Becker, <becker@super.org> 11 * Alan Cox, <alan@lxorguk.ukuu.org.uk> 12 * Richard Underwood 13 * Stefan Becker, <stefanb@yello.ping.de> 14 * Jorge Cwik, <jorge@laser.satlink.net> 15 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 16 * 17 * 18 * Fixes: 19 * Alan Cox : Commented a couple of minor bits of surplus code 20 * Alan Cox : Undefining IP_FORWARD doesn't include the code 21 * (just stops a compiler warning). 22 * Alan Cox : Frames with >=MAX_ROUTE record routes, strict routes or loose routes 23 * are junked rather than corrupting things. 24 * Alan Cox : Frames to bad broadcast subnets are dumped 25 * We used to process them non broadcast and 26 * boy could that cause havoc. 27 * Alan Cox : ip_forward sets the free flag on the 28 * new frame it queues. Still crap because 29 * it copies the frame but at least it 30 * doesn't eat memory too. 31 * Alan Cox : Generic queue code and memory fixes. 32 * Fred Van Kempen : IP fragment support (borrowed from NET2E) 33 * Gerhard Koerting: Forward fragmented frames correctly. 34 * Gerhard Koerting: Fixes to my fix of the above 8-). 35 * Gerhard Koerting: IP interface addressing fix. 36 * Linus Torvalds : More robustness checks 37 * Alan Cox : Even more checks: Still not as robust as it ought to be 38 * Alan Cox : Save IP header pointer for later 39 * Alan Cox : ip option setting 40 * Alan Cox : Use ip_tos/ip_ttl settings 41 * Alan Cox : Fragmentation bogosity removed 42 * (Thanks to Mark.Bush@prg.ox.ac.uk) 43 * Dmitry Gorodchanin : Send of a raw packet crash fix. 44 * Alan Cox : Silly ip bug when an overlength 45 * fragment turns up. Now frees the 46 * queue. 47 * Linus Torvalds/ : Memory leakage on fragmentation 48 * Alan Cox : handling. 49 * Gerhard Koerting: Forwarding uses IP priority hints 50 * Teemu Rantanen : Fragment problems. 51 * Alan Cox : General cleanup, comments and reformat 52 * Alan Cox : SNMP statistics 53 * Alan Cox : BSD address rule semantics. Also see 54 * UDP as there is a nasty checksum issue 55 * if you do things the wrong way. 56 * Alan Cox : Always defrag, moved IP_FORWARD to the config.in file 57 * Alan Cox : IP options adjust sk->priority. 58 * Pedro Roque : Fix mtu/length error in ip_forward. 59 * Alan Cox : Avoid ip_chk_addr when possible. 60 * Richard Underwood : IP multicasting. 61 * Alan Cox : Cleaned up multicast handlers. 62 * Alan Cox : RAW sockets demultiplex in the BSD style. 63 * Gunther Mayer : Fix the SNMP reporting typo 64 * Alan Cox : Always in group 224.0.0.1 65 * Pauline Middelink : Fast ip_checksum update when forwarding 66 * Masquerading support. 67 * Alan Cox : Multicast loopback error for 224.0.0.1 68 * Alan Cox : IP_MULTICAST_LOOP option. 69 * Alan Cox : Use notifiers. 70 * Bjorn Ekwall : Removed ip_csum (from slhc.c too) 71 * Bjorn Ekwall : Moved ip_fast_csum to ip.h (inline!) 72 * Stefan Becker : Send out ICMP HOST REDIRECT 73 * Arnt Gulbrandsen : ip_build_xmit 74 * Alan Cox : Per socket routing cache 75 * Alan Cox : Fixed routing cache, added header cache. 76 * Alan Cox : Loopback didn't work right in original ip_build_xmit - fixed it. 77 * Alan Cox : Only send ICMP_REDIRECT if src/dest are the same net. 78 * Alan Cox : Incoming IP option handling. 79 * Alan Cox : Set saddr on raw output frames as per BSD. 80 * Alan Cox : Stopped broadcast source route explosions. 81 * Alan Cox : Can disable source routing 82 * Takeshi Sone : Masquerading didn't work. 83 * Dave Bonn,Alan Cox : Faster IP forwarding whenever possible. 84 * Alan Cox : Memory leaks, tramples, misc debugging. 85 * Alan Cox : Fixed multicast (by popular demand 8)) 86 * Alan Cox : Fixed forwarding (by even more popular demand 8)) 87 * Alan Cox : Fixed SNMP statistics [I think] 88 * Gerhard Koerting : IP fragmentation forwarding fix 89 * Alan Cox : Device lock against page fault. 90 * Alan Cox : IP_HDRINCL facility. 91 * Werner Almesberger : Zero fragment bug 92 * Alan Cox : RAW IP frame length bug 93 * Alan Cox : Outgoing firewall on build_xmit 94 * A.N.Kuznetsov : IP_OPTIONS support throughout the kernel 95 * Alan Cox : Multicast routing hooks 96 * Jos Vos : Do accounting *before* call_in_firewall 97 * Willy Konynenberg : Transparent proxying support 98 * 99 * 100 * 101 * To Fix: 102 * IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient 103 * and could be made very efficient with the addition of some virtual memory hacks to permit 104 * the allocation of a buffer that can then be 'grown' by twiddling page tables. 105 * Output fragmentation wants updating along with the buffer management to use a single 106 * interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet 107 * output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause 108 * fragmentation anyway. 109 * 110 * This program is free software; you can redistribute it and/or 111 * modify it under the terms of the GNU General Public License 112 * as published by the Free Software Foundation; either version 113 * 2 of the License, or (at your option) any later version. 114 */ 115 116 #define pr_fmt(fmt) "IPv4: " fmt 117 118 #include <linux/module.h> 119 #include <linux/types.h> 120 #include <linux/kernel.h> 121 #include <linux/string.h> 122 #include <linux/errno.h> 123 #include <linux/slab.h> 124 125 #include <linux/net.h> 126 #include <linux/socket.h> 127 #include <linux/sockios.h> 128 #include <linux/in.h> 129 #include <linux/inet.h> 130 #include <linux/inetdevice.h> 131 #include <linux/netdevice.h> 132 #include <linux/etherdevice.h> 133 134 #include <net/snmp.h> 135 #include <net/ip.h> 136 #include <net/protocol.h> 137 #include <net/route.h> 138 #include <linux/skbuff.h> 139 #include <net/sock.h> 140 #include <net/arp.h> 141 #include <net/icmp.h> 142 #include <net/raw.h> 143 #include <net/checksum.h> 144 #include <net/inet_ecn.h> 145 #include <linux/netfilter_ipv4.h> 146 #include <net/xfrm.h> 147 #include <linux/mroute.h> 148 #include <linux/netlink.h> 149 #include <net/dst_metadata.h> 150 151 /* 152 * Process Router Attention IP option (RFC 2113) 153 */ 154 bool ip_call_ra_chain(struct sk_buff *skb) 155 { 156 struct ip_ra_chain *ra; 157 u8 protocol = ip_hdr(skb)->protocol; 158 struct sock *last = NULL; 159 struct net_device *dev = skb->dev; 160 struct net *net = dev_net(dev); 161 162 for (ra = rcu_dereference(net->ipv4.ra_chain); ra; ra = rcu_dereference(ra->next)) { 163 struct sock *sk = ra->sk; 164 165 /* If socket is bound to an interface, only report 166 * the packet if it came from that interface. 167 */ 168 if (sk && inet_sk(sk)->inet_num == protocol && 169 (!sk->sk_bound_dev_if || 170 sk->sk_bound_dev_if == dev->ifindex)) { 171 if (ip_is_fragment(ip_hdr(skb))) { 172 if (ip_defrag(net, skb, IP_DEFRAG_CALL_RA_CHAIN)) 173 return true; 174 } 175 if (last) { 176 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); 177 if (skb2) 178 raw_rcv(last, skb2); 179 } 180 last = sk; 181 } 182 } 183 184 if (last) { 185 raw_rcv(last, skb); 186 return true; 187 } 188 return false; 189 } 190 191 void ip_protocol_deliver_rcu(struct net *net, struct sk_buff *skb, int protocol) 192 { 193 const struct net_protocol *ipprot; 194 int raw, ret; 195 196 resubmit: 197 raw = raw_local_deliver(skb, protocol); 198 199 ipprot = rcu_dereference(inet_protos[protocol]); 200 if (ipprot) { 201 if (!ipprot->no_policy) { 202 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 203 kfree_skb(skb); 204 return; 205 } 206 nf_reset(skb); 207 } 208 ret = ipprot->handler(skb); 209 if (ret < 0) { 210 protocol = -ret; 211 goto resubmit; 212 } 213 __IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS); 214 } else { 215 if (!raw) { 216 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 217 __IP_INC_STATS(net, IPSTATS_MIB_INUNKNOWNPROTOS); 218 icmp_send(skb, ICMP_DEST_UNREACH, 219 ICMP_PROT_UNREACH, 0); 220 } 221 kfree_skb(skb); 222 } else { 223 __IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS); 224 consume_skb(skb); 225 } 226 } 227 } 228 229 static int ip_local_deliver_finish(struct net *net, struct sock *sk, struct sk_buff *skb) 230 { 231 __skb_pull(skb, skb_network_header_len(skb)); 232 233 rcu_read_lock(); 234 ip_protocol_deliver_rcu(net, skb, ip_hdr(skb)->protocol); 235 rcu_read_unlock(); 236 237 return 0; 238 } 239 240 /* 241 * Deliver IP Packets to the higher protocol layers. 242 */ 243 int ip_local_deliver(struct sk_buff *skb) 244 { 245 /* 246 * Reassemble IP fragments. 247 */ 248 struct net *net = dev_net(skb->dev); 249 250 if (ip_is_fragment(ip_hdr(skb))) { 251 if (ip_defrag(net, skb, IP_DEFRAG_LOCAL_DELIVER)) 252 return 0; 253 } 254 255 return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, 256 net, NULL, skb, skb->dev, NULL, 257 ip_local_deliver_finish); 258 } 259 260 static inline bool ip_rcv_options(struct sk_buff *skb, struct net_device *dev) 261 { 262 struct ip_options *opt; 263 const struct iphdr *iph; 264 265 /* It looks as overkill, because not all 266 IP options require packet mangling. 267 But it is the easiest for now, especially taking 268 into account that combination of IP options 269 and running sniffer is extremely rare condition. 270 --ANK (980813) 271 */ 272 if (skb_cow(skb, skb_headroom(skb))) { 273 __IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INDISCARDS); 274 goto drop; 275 } 276 277 iph = ip_hdr(skb); 278 opt = &(IPCB(skb)->opt); 279 opt->optlen = iph->ihl*4 - sizeof(struct iphdr); 280 281 if (ip_options_compile(dev_net(dev), opt, skb)) { 282 __IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 283 goto drop; 284 } 285 286 if (unlikely(opt->srr)) { 287 struct in_device *in_dev = __in_dev_get_rcu(dev); 288 289 if (in_dev) { 290 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 291 if (IN_DEV_LOG_MARTIANS(in_dev)) 292 net_info_ratelimited("source route option %pI4 -> %pI4\n", 293 &iph->saddr, 294 &iph->daddr); 295 goto drop; 296 } 297 } 298 299 if (ip_options_rcv_srr(skb, dev)) 300 goto drop; 301 } 302 303 return false; 304 drop: 305 return true; 306 } 307 308 static int ip_rcv_finish_core(struct net *net, struct sock *sk, 309 struct sk_buff *skb, struct net_device *dev) 310 { 311 const struct iphdr *iph = ip_hdr(skb); 312 int (*edemux)(struct sk_buff *skb); 313 struct rtable *rt; 314 int err; 315 316 if (net->ipv4.sysctl_ip_early_demux && 317 !skb_dst(skb) && 318 !skb->sk && 319 !ip_is_fragment(iph)) { 320 const struct net_protocol *ipprot; 321 int protocol = iph->protocol; 322 323 ipprot = rcu_dereference(inet_protos[protocol]); 324 if (ipprot && (edemux = READ_ONCE(ipprot->early_demux))) { 325 err = edemux(skb); 326 if (unlikely(err)) 327 goto drop_error; 328 /* must reload iph, skb->head might have changed */ 329 iph = ip_hdr(skb); 330 } 331 } 332 333 /* 334 * Initialise the virtual path cache for the packet. It describes 335 * how the packet travels inside Linux networking. 336 */ 337 if (!skb_valid_dst(skb)) { 338 err = ip_route_input_noref(skb, iph->daddr, iph->saddr, 339 iph->tos, dev); 340 if (unlikely(err)) 341 goto drop_error; 342 } 343 344 #ifdef CONFIG_IP_ROUTE_CLASSID 345 if (unlikely(skb_dst(skb)->tclassid)) { 346 struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct); 347 u32 idx = skb_dst(skb)->tclassid; 348 st[idx&0xFF].o_packets++; 349 st[idx&0xFF].o_bytes += skb->len; 350 st[(idx>>16)&0xFF].i_packets++; 351 st[(idx>>16)&0xFF].i_bytes += skb->len; 352 } 353 #endif 354 355 if (iph->ihl > 5 && ip_rcv_options(skb, dev)) 356 goto drop; 357 358 rt = skb_rtable(skb); 359 if (rt->rt_type == RTN_MULTICAST) { 360 __IP_UPD_PO_STATS(net, IPSTATS_MIB_INMCAST, skb->len); 361 } else if (rt->rt_type == RTN_BROADCAST) { 362 __IP_UPD_PO_STATS(net, IPSTATS_MIB_INBCAST, skb->len); 363 } else if (skb->pkt_type == PACKET_BROADCAST || 364 skb->pkt_type == PACKET_MULTICAST) { 365 struct in_device *in_dev = __in_dev_get_rcu(dev); 366 367 /* RFC 1122 3.3.6: 368 * 369 * When a host sends a datagram to a link-layer broadcast 370 * address, the IP destination address MUST be a legal IP 371 * broadcast or IP multicast address. 372 * 373 * A host SHOULD silently discard a datagram that is received 374 * via a link-layer broadcast (see Section 2.4) but does not 375 * specify an IP multicast or broadcast destination address. 376 * 377 * This doesn't explicitly say L2 *broadcast*, but broadcast is 378 * in a way a form of multicast and the most common use case for 379 * this is 802.11 protecting against cross-station spoofing (the 380 * so-called "hole-196" attack) so do it for both. 381 */ 382 if (in_dev && 383 IN_DEV_ORCONF(in_dev, DROP_UNICAST_IN_L2_MULTICAST)) 384 goto drop; 385 } 386 387 return NET_RX_SUCCESS; 388 389 drop: 390 kfree_skb(skb); 391 return NET_RX_DROP; 392 393 drop_error: 394 if (err == -EXDEV) 395 __NET_INC_STATS(net, LINUX_MIB_IPRPFILTER); 396 goto drop; 397 } 398 399 static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb) 400 { 401 struct net_device *dev = skb->dev; 402 int ret; 403 404 /* if ingress device is enslaved to an L3 master device pass the 405 * skb to its handler for processing 406 */ 407 skb = l3mdev_ip_rcv(skb); 408 if (!skb) 409 return NET_RX_SUCCESS; 410 411 ret = ip_rcv_finish_core(net, sk, skb, dev); 412 if (ret != NET_RX_DROP) 413 ret = dst_input(skb); 414 return ret; 415 } 416 417 /* 418 * Main IP Receive routine. 419 */ 420 static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net) 421 { 422 const struct iphdr *iph; 423 u32 len; 424 425 /* When the interface is in promisc. mode, drop all the crap 426 * that it receives, do not try to analyse it. 427 */ 428 if (skb->pkt_type == PACKET_OTHERHOST) 429 goto drop; 430 431 __IP_UPD_PO_STATS(net, IPSTATS_MIB_IN, skb->len); 432 433 skb = skb_share_check(skb, GFP_ATOMIC); 434 if (!skb) { 435 __IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS); 436 goto out; 437 } 438 439 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 440 goto inhdr_error; 441 442 iph = ip_hdr(skb); 443 444 /* 445 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum. 446 * 447 * Is the datagram acceptable? 448 * 449 * 1. Length at least the size of an ip header 450 * 2. Version of 4 451 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 452 * 4. Doesn't have a bogus length 453 */ 454 455 if (iph->ihl < 5 || iph->version != 4) 456 goto inhdr_error; 457 458 BUILD_BUG_ON(IPSTATS_MIB_ECT1PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_1); 459 BUILD_BUG_ON(IPSTATS_MIB_ECT0PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_0); 460 BUILD_BUG_ON(IPSTATS_MIB_CEPKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_CE); 461 __IP_ADD_STATS(net, 462 IPSTATS_MIB_NOECTPKTS + (iph->tos & INET_ECN_MASK), 463 max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs)); 464 465 if (!pskb_may_pull(skb, iph->ihl*4)) 466 goto inhdr_error; 467 468 iph = ip_hdr(skb); 469 470 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 471 goto csum_error; 472 473 len = ntohs(iph->tot_len); 474 if (skb->len < len) { 475 __IP_INC_STATS(net, IPSTATS_MIB_INTRUNCATEDPKTS); 476 goto drop; 477 } else if (len < (iph->ihl*4)) 478 goto inhdr_error; 479 480 /* Our transport medium may have padded the buffer out. Now we know it 481 * is IP we can trim to the true length of the frame. 482 * Note this now means skb->len holds ntohs(iph->tot_len). 483 */ 484 if (pskb_trim_rcsum(skb, len)) { 485 __IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS); 486 goto drop; 487 } 488 489 iph = ip_hdr(skb); 490 skb->transport_header = skb->network_header + iph->ihl*4; 491 492 /* Remove any debris in the socket control block */ 493 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 494 IPCB(skb)->iif = skb->skb_iif; 495 496 /* Must drop socket now because of tproxy. */ 497 skb_orphan(skb); 498 499 return skb; 500 501 csum_error: 502 __IP_INC_STATS(net, IPSTATS_MIB_CSUMERRORS); 503 inhdr_error: 504 __IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS); 505 drop: 506 kfree_skb(skb); 507 out: 508 return NULL; 509 } 510 511 /* 512 * IP receive entry point 513 */ 514 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, 515 struct net_device *orig_dev) 516 { 517 struct net *net = dev_net(dev); 518 519 skb = ip_rcv_core(skb, net); 520 if (skb == NULL) 521 return NET_RX_DROP; 522 523 return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, 524 net, NULL, skb, dev, NULL, 525 ip_rcv_finish); 526 } 527 528 static void ip_sublist_rcv_finish(struct list_head *head) 529 { 530 struct sk_buff *skb, *next; 531 532 list_for_each_entry_safe(skb, next, head, list) { 533 skb_list_del_init(skb); 534 dst_input(skb); 535 } 536 } 537 538 static void ip_list_rcv_finish(struct net *net, struct sock *sk, 539 struct list_head *head) 540 { 541 struct dst_entry *curr_dst = NULL; 542 struct sk_buff *skb, *next; 543 struct list_head sublist; 544 545 INIT_LIST_HEAD(&sublist); 546 list_for_each_entry_safe(skb, next, head, list) { 547 struct net_device *dev = skb->dev; 548 struct dst_entry *dst; 549 550 skb_list_del_init(skb); 551 /* if ingress device is enslaved to an L3 master device pass the 552 * skb to its handler for processing 553 */ 554 skb = l3mdev_ip_rcv(skb); 555 if (!skb) 556 continue; 557 if (ip_rcv_finish_core(net, sk, skb, dev) == NET_RX_DROP) 558 continue; 559 560 dst = skb_dst(skb); 561 if (curr_dst != dst) { 562 /* dispatch old sublist */ 563 if (!list_empty(&sublist)) 564 ip_sublist_rcv_finish(&sublist); 565 /* start new sublist */ 566 INIT_LIST_HEAD(&sublist); 567 curr_dst = dst; 568 } 569 list_add_tail(&skb->list, &sublist); 570 } 571 /* dispatch final sublist */ 572 ip_sublist_rcv_finish(&sublist); 573 } 574 575 static void ip_sublist_rcv(struct list_head *head, struct net_device *dev, 576 struct net *net) 577 { 578 NF_HOOK_LIST(NFPROTO_IPV4, NF_INET_PRE_ROUTING, net, NULL, 579 head, dev, NULL, ip_rcv_finish); 580 ip_list_rcv_finish(net, NULL, head); 581 } 582 583 /* Receive a list of IP packets */ 584 void ip_list_rcv(struct list_head *head, struct packet_type *pt, 585 struct net_device *orig_dev) 586 { 587 struct net_device *curr_dev = NULL; 588 struct net *curr_net = NULL; 589 struct sk_buff *skb, *next; 590 struct list_head sublist; 591 592 INIT_LIST_HEAD(&sublist); 593 list_for_each_entry_safe(skb, next, head, list) { 594 struct net_device *dev = skb->dev; 595 struct net *net = dev_net(dev); 596 597 skb_list_del_init(skb); 598 skb = ip_rcv_core(skb, net); 599 if (skb == NULL) 600 continue; 601 602 if (curr_dev != dev || curr_net != net) { 603 /* dispatch old sublist */ 604 if (!list_empty(&sublist)) 605 ip_sublist_rcv(&sublist, curr_dev, curr_net); 606 /* start new sublist */ 607 INIT_LIST_HEAD(&sublist); 608 curr_dev = dev; 609 curr_net = net; 610 } 611 list_add_tail(&skb->list, &sublist); 612 } 613 /* dispatch final sublist */ 614 ip_sublist_rcv(&sublist, curr_dev, curr_net); 615 } 616