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, <[email protected]> 10 * Donald Becker, <[email protected]> 11 * Alan Cox, <[email protected]> 12 * Richard Underwood 13 * Stefan Becker, <[email protected]> 14 * Jorge Cwik, <[email protected]> 15 * Arnt Gulbrandsen, <[email protected]> 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 [email protected]) 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_BH(net, IPSTATS_MIB_INDELIVERS); 222 } else { 223 if (!raw) { 224 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 225 IP_INC_STATS_BH(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_BH(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_BH(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_BH(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 int sysctl_ip_early_demux __read_mostly = 1; 312 EXPORT_SYMBOL(sysctl_ip_early_demux); 313 314 static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb) 315 { 316 const struct iphdr *iph = ip_hdr(skb); 317 struct rtable *rt; 318 319 if (sysctl_ip_early_demux && 320 !skb_dst(skb) && 321 !skb->sk && 322 !ip_is_fragment(iph)) { 323 const struct net_protocol *ipprot; 324 int protocol = iph->protocol; 325 326 ipprot = rcu_dereference(inet_protos[protocol]); 327 if (ipprot && ipprot->early_demux) { 328 ipprot->early_demux(skb); 329 /* must reload iph, skb->head might have changed */ 330 iph = ip_hdr(skb); 331 } 332 } 333 334 /* 335 * Initialise the virtual path cache for the packet. It describes 336 * how the packet travels inside Linux networking. 337 */ 338 if (!skb_valid_dst(skb)) { 339 int err = ip_route_input_noref(skb, iph->daddr, iph->saddr, 340 iph->tos, skb->dev); 341 if (unlikely(err)) { 342 if (err == -EXDEV) 343 NET_INC_STATS_BH(net, LINUX_MIB_IPRPFILTER); 344 goto drop; 345 } 346 } 347 348 #ifdef CONFIG_IP_ROUTE_CLASSID 349 if (unlikely(skb_dst(skb)->tclassid)) { 350 struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct); 351 u32 idx = skb_dst(skb)->tclassid; 352 st[idx&0xFF].o_packets++; 353 st[idx&0xFF].o_bytes += skb->len; 354 st[(idx>>16)&0xFF].i_packets++; 355 st[(idx>>16)&0xFF].i_bytes += skb->len; 356 } 357 #endif 358 359 if (iph->ihl > 5 && ip_rcv_options(skb)) 360 goto drop; 361 362 rt = skb_rtable(skb); 363 if (rt->rt_type == RTN_MULTICAST) { 364 IP_UPD_PO_STATS_BH(net, IPSTATS_MIB_INMCAST, skb->len); 365 } else if (rt->rt_type == RTN_BROADCAST) { 366 IP_UPD_PO_STATS_BH(net, IPSTATS_MIB_INBCAST, skb->len); 367 } else if (skb->pkt_type == PACKET_BROADCAST || 368 skb->pkt_type == PACKET_MULTICAST) { 369 struct in_device *in_dev = __in_dev_get_rcu(skb->dev); 370 371 /* RFC 1122 3.3.6: 372 * 373 * When a host sends a datagram to a link-layer broadcast 374 * address, the IP destination address MUST be a legal IP 375 * broadcast or IP multicast address. 376 * 377 * A host SHOULD silently discard a datagram that is received 378 * via a link-layer broadcast (see Section 2.4) but does not 379 * specify an IP multicast or broadcast destination address. 380 * 381 * This doesn't explicitly say L2 *broadcast*, but broadcast is 382 * in a way a form of multicast and the most common use case for 383 * this is 802.11 protecting against cross-station spoofing (the 384 * so-called "hole-196" attack) so do it for both. 385 */ 386 if (in_dev && 387 IN_DEV_ORCONF(in_dev, DROP_UNICAST_IN_L2_MULTICAST)) 388 goto drop; 389 } 390 391 return dst_input(skb); 392 393 drop: 394 kfree_skb(skb); 395 return NET_RX_DROP; 396 } 397 398 /* 399 * Main IP Receive routine. 400 */ 401 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 402 { 403 const struct iphdr *iph; 404 struct net *net; 405 u32 len; 406 407 /* When the interface is in promisc. mode, drop all the crap 408 * that it receives, do not try to analyse it. 409 */ 410 if (skb->pkt_type == PACKET_OTHERHOST) 411 goto drop; 412 413 414 net = dev_net(dev); 415 IP_UPD_PO_STATS_BH(net, IPSTATS_MIB_IN, skb->len); 416 417 skb = skb_share_check(skb, GFP_ATOMIC); 418 if (!skb) { 419 IP_INC_STATS_BH(net, IPSTATS_MIB_INDISCARDS); 420 goto out; 421 } 422 423 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 424 goto inhdr_error; 425 426 iph = ip_hdr(skb); 427 428 /* 429 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum. 430 * 431 * Is the datagram acceptable? 432 * 433 * 1. Length at least the size of an ip header 434 * 2. Version of 4 435 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 436 * 4. Doesn't have a bogus length 437 */ 438 439 if (iph->ihl < 5 || iph->version != 4) 440 goto inhdr_error; 441 442 BUILD_BUG_ON(IPSTATS_MIB_ECT1PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_1); 443 BUILD_BUG_ON(IPSTATS_MIB_ECT0PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_0); 444 BUILD_BUG_ON(IPSTATS_MIB_CEPKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_CE); 445 IP_ADD_STATS_BH(net, 446 IPSTATS_MIB_NOECTPKTS + (iph->tos & INET_ECN_MASK), 447 max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs)); 448 449 if (!pskb_may_pull(skb, iph->ihl*4)) 450 goto inhdr_error; 451 452 iph = ip_hdr(skb); 453 454 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 455 goto csum_error; 456 457 len = ntohs(iph->tot_len); 458 if (skb->len < len) { 459 IP_INC_STATS_BH(net, IPSTATS_MIB_INTRUNCATEDPKTS); 460 goto drop; 461 } else if (len < (iph->ihl*4)) 462 goto inhdr_error; 463 464 /* Our transport medium may have padded the buffer out. Now we know it 465 * is IP we can trim to the true length of the frame. 466 * Note this now means skb->len holds ntohs(iph->tot_len). 467 */ 468 if (pskb_trim_rcsum(skb, len)) { 469 IP_INC_STATS_BH(net, IPSTATS_MIB_INDISCARDS); 470 goto drop; 471 } 472 473 skb->transport_header = skb->network_header + iph->ihl*4; 474 475 /* Remove any debris in the socket control block */ 476 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 477 478 /* Must drop socket now because of tproxy. */ 479 skb_orphan(skb); 480 481 return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, 482 net, NULL, skb, dev, NULL, 483 ip_rcv_finish); 484 485 csum_error: 486 IP_INC_STATS_BH(net, IPSTATS_MIB_CSUMERRORS); 487 inhdr_error: 488 IP_INC_STATS_BH(net, IPSTATS_MIB_INHDRERRORS); 489 drop: 490 kfree_skb(skb); 491 out: 492 return NET_RX_DROP; 493 } 494