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(ip_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 net_eq(sock_net(sk), net)) { 172 if (ip_is_fragment(ip_hdr(skb))) { 173 if (ip_defrag(net, skb, IP_DEFRAG_CALL_RA_CHAIN)) 174 return true; 175 } 176 if (last) { 177 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); 178 if (skb2) 179 raw_rcv(last, skb2); 180 } 181 last = sk; 182 } 183 } 184 185 if (last) { 186 raw_rcv(last, skb); 187 return true; 188 } 189 return false; 190 } 191 192 static int ip_local_deliver_finish(struct net *net, struct sock *sk, struct sk_buff *skb) 193 { 194 __skb_pull(skb, skb_network_header_len(skb)); 195 196 rcu_read_lock(); 197 { 198 int protocol = ip_hdr(skb)->protocol; 199 const struct net_protocol *ipprot; 200 int raw; 201 202 resubmit: 203 raw = raw_local_deliver(skb, protocol); 204 205 ipprot = rcu_dereference(inet_protos[protocol]); 206 if (ipprot) { 207 int ret; 208 209 if (!ipprot->no_policy) { 210 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 211 kfree_skb(skb); 212 goto out; 213 } 214 nf_reset(skb); 215 } 216 ret = ipprot->handler(skb); 217 if (ret < 0) { 218 protocol = -ret; 219 goto resubmit; 220 } 221 __IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS); 222 } else { 223 if (!raw) { 224 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 225 __IP_INC_STATS(net, IPSTATS_MIB_INUNKNOWNPROTOS); 226 icmp_send(skb, ICMP_DEST_UNREACH, 227 ICMP_PROT_UNREACH, 0); 228 } 229 kfree_skb(skb); 230 } else { 231 __IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS); 232 consume_skb(skb); 233 } 234 } 235 } 236 out: 237 rcu_read_unlock(); 238 239 return 0; 240 } 241 242 /* 243 * Deliver IP Packets to the higher protocol layers. 244 */ 245 int ip_local_deliver(struct sk_buff *skb) 246 { 247 /* 248 * Reassemble IP fragments. 249 */ 250 struct net *net = dev_net(skb->dev); 251 252 if (ip_is_fragment(ip_hdr(skb))) { 253 if (ip_defrag(net, skb, IP_DEFRAG_LOCAL_DELIVER)) 254 return 0; 255 } 256 257 return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, 258 net, NULL, skb, skb->dev, NULL, 259 ip_local_deliver_finish); 260 } 261 262 static inline bool ip_rcv_options(struct sk_buff *skb) 263 { 264 struct ip_options *opt; 265 const struct iphdr *iph; 266 struct net_device *dev = skb->dev; 267 268 /* It looks as overkill, because not all 269 IP options require packet mangling. 270 But it is the easiest for now, especially taking 271 into account that combination of IP options 272 and running sniffer is extremely rare condition. 273 --ANK (980813) 274 */ 275 if (skb_cow(skb, skb_headroom(skb))) { 276 __IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INDISCARDS); 277 goto drop; 278 } 279 280 iph = ip_hdr(skb); 281 opt = &(IPCB(skb)->opt); 282 opt->optlen = iph->ihl*4 - sizeof(struct iphdr); 283 284 if (ip_options_compile(dev_net(dev), opt, skb)) { 285 __IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 286 goto drop; 287 } 288 289 if (unlikely(opt->srr)) { 290 struct in_device *in_dev = __in_dev_get_rcu(dev); 291 292 if (in_dev) { 293 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 294 if (IN_DEV_LOG_MARTIANS(in_dev)) 295 net_info_ratelimited("source route option %pI4 -> %pI4\n", 296 &iph->saddr, 297 &iph->daddr); 298 goto drop; 299 } 300 } 301 302 if (ip_options_rcv_srr(skb)) 303 goto drop; 304 } 305 306 return false; 307 drop: 308 return true; 309 } 310 311 static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb) 312 { 313 const struct iphdr *iph = ip_hdr(skb); 314 struct rtable *rt; 315 struct net_device *dev = skb->dev; 316 317 /* if ingress device is enslaved to an L3 master device pass the 318 * skb to its handler for processing 319 */ 320 skb = l3mdev_ip_rcv(skb); 321 if (!skb) 322 return NET_RX_SUCCESS; 323 324 if (net->ipv4.sysctl_ip_early_demux && 325 !skb_dst(skb) && 326 !skb->sk && 327 !ip_is_fragment(iph)) { 328 const struct net_protocol *ipprot; 329 int protocol = iph->protocol; 330 331 ipprot = rcu_dereference(inet_protos[protocol]); 332 if (ipprot && ipprot->early_demux) { 333 ipprot->early_demux(skb); 334 /* must reload iph, skb->head might have changed */ 335 iph = ip_hdr(skb); 336 } 337 } 338 339 /* 340 * Initialise the virtual path cache for the packet. It describes 341 * how the packet travels inside Linux networking. 342 */ 343 if (!skb_valid_dst(skb)) { 344 int err = ip_route_input_noref(skb, iph->daddr, iph->saddr, 345 iph->tos, dev); 346 if (unlikely(err)) { 347 if (err == -EXDEV) 348 __NET_INC_STATS(net, LINUX_MIB_IPRPFILTER); 349 goto drop; 350 } 351 } 352 353 #ifdef CONFIG_IP_ROUTE_CLASSID 354 if (unlikely(skb_dst(skb)->tclassid)) { 355 struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct); 356 u32 idx = skb_dst(skb)->tclassid; 357 st[idx&0xFF].o_packets++; 358 st[idx&0xFF].o_bytes += skb->len; 359 st[(idx>>16)&0xFF].i_packets++; 360 st[(idx>>16)&0xFF].i_bytes += skb->len; 361 } 362 #endif 363 364 if (iph->ihl > 5 && ip_rcv_options(skb)) 365 goto drop; 366 367 rt = skb_rtable(skb); 368 if (rt->rt_type == RTN_MULTICAST) { 369 __IP_UPD_PO_STATS(net, IPSTATS_MIB_INMCAST, skb->len); 370 } else if (rt->rt_type == RTN_BROADCAST) { 371 __IP_UPD_PO_STATS(net, IPSTATS_MIB_INBCAST, skb->len); 372 } else if (skb->pkt_type == PACKET_BROADCAST || 373 skb->pkt_type == PACKET_MULTICAST) { 374 struct in_device *in_dev = __in_dev_get_rcu(dev); 375 376 /* RFC 1122 3.3.6: 377 * 378 * When a host sends a datagram to a link-layer broadcast 379 * address, the IP destination address MUST be a legal IP 380 * broadcast or IP multicast address. 381 * 382 * A host SHOULD silently discard a datagram that is received 383 * via a link-layer broadcast (see Section 2.4) but does not 384 * specify an IP multicast or broadcast destination address. 385 * 386 * This doesn't explicitly say L2 *broadcast*, but broadcast is 387 * in a way a form of multicast and the most common use case for 388 * this is 802.11 protecting against cross-station spoofing (the 389 * so-called "hole-196" attack) so do it for both. 390 */ 391 if (in_dev && 392 IN_DEV_ORCONF(in_dev, DROP_UNICAST_IN_L2_MULTICAST)) 393 goto drop; 394 } 395 396 return dst_input(skb); 397 398 drop: 399 kfree_skb(skb); 400 return NET_RX_DROP; 401 } 402 403 /* 404 * Main IP Receive routine. 405 */ 406 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 407 { 408 const struct iphdr *iph; 409 struct net *net; 410 u32 len; 411 412 /* When the interface is in promisc. mode, drop all the crap 413 * that it receives, do not try to analyse it. 414 */ 415 if (skb->pkt_type == PACKET_OTHERHOST) 416 goto drop; 417 418 419 net = dev_net(dev); 420 __IP_UPD_PO_STATS(net, IPSTATS_MIB_IN, skb->len); 421 422 skb = skb_share_check(skb, GFP_ATOMIC); 423 if (!skb) { 424 __IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS); 425 goto out; 426 } 427 428 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 429 goto inhdr_error; 430 431 iph = ip_hdr(skb); 432 433 /* 434 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum. 435 * 436 * Is the datagram acceptable? 437 * 438 * 1. Length at least the size of an ip header 439 * 2. Version of 4 440 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 441 * 4. Doesn't have a bogus length 442 */ 443 444 if (iph->ihl < 5 || iph->version != 4) 445 goto inhdr_error; 446 447 BUILD_BUG_ON(IPSTATS_MIB_ECT1PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_1); 448 BUILD_BUG_ON(IPSTATS_MIB_ECT0PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_0); 449 BUILD_BUG_ON(IPSTATS_MIB_CEPKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_CE); 450 __IP_ADD_STATS(net, 451 IPSTATS_MIB_NOECTPKTS + (iph->tos & INET_ECN_MASK), 452 max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs)); 453 454 if (!pskb_may_pull(skb, iph->ihl*4)) 455 goto inhdr_error; 456 457 iph = ip_hdr(skb); 458 459 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 460 goto csum_error; 461 462 len = ntohs(iph->tot_len); 463 if (skb->len < len) { 464 __IP_INC_STATS(net, IPSTATS_MIB_INTRUNCATEDPKTS); 465 goto drop; 466 } else if (len < (iph->ihl*4)) 467 goto inhdr_error; 468 469 /* Our transport medium may have padded the buffer out. Now we know it 470 * is IP we can trim to the true length of the frame. 471 * Note this now means skb->len holds ntohs(iph->tot_len). 472 */ 473 if (pskb_trim_rcsum(skb, len)) { 474 __IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS); 475 goto drop; 476 } 477 478 skb->transport_header = skb->network_header + iph->ihl*4; 479 480 /* Remove any debris in the socket control block */ 481 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 482 IPCB(skb)->iif = skb->skb_iif; 483 484 /* Must drop socket now because of tproxy. */ 485 skb_orphan(skb); 486 487 return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, 488 net, NULL, skb, dev, NULL, 489 ip_rcv_finish); 490 491 csum_error: 492 __IP_INC_STATS(net, IPSTATS_MIB_CSUMERRORS); 493 inhdr_error: 494 __IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS); 495 drop: 496 kfree_skb(skb); 497 out: 498 return NET_RX_DROP; 499 } 500