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 static int ip_local_deliver_finish(struct net *net, struct sock *sk, struct sk_buff *skb) 192 { 193 __skb_pull(skb, skb_network_header_len(skb)); 194 195 rcu_read_lock(); 196 { 197 int protocol = ip_hdr(skb)->protocol; 198 const struct net_protocol *ipprot; 199 int raw; 200 201 resubmit: 202 raw = raw_local_deliver(skb, protocol); 203 204 ipprot = rcu_dereference(inet_protos[protocol]); 205 if (ipprot) { 206 int ret; 207 208 if (!ipprot->no_policy) { 209 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 210 kfree_skb(skb); 211 goto out; 212 } 213 nf_reset(skb); 214 } 215 ret = ipprot->handler(skb); 216 if (ret < 0) { 217 protocol = -ret; 218 goto resubmit; 219 } 220 __IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS); 221 } else { 222 if (!raw) { 223 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 224 __IP_INC_STATS(net, IPSTATS_MIB_INUNKNOWNPROTOS); 225 icmp_send(skb, ICMP_DEST_UNREACH, 226 ICMP_PROT_UNREACH, 0); 227 } 228 kfree_skb(skb); 229 } else { 230 __IP_INC_STATS(net, IPSTATS_MIB_INDELIVERS); 231 consume_skb(skb); 232 } 233 } 234 } 235 out: 236 rcu_read_unlock(); 237 238 return 0; 239 } 240 241 /* 242 * Deliver IP Packets to the higher protocol layers. 243 */ 244 int ip_local_deliver(struct sk_buff *skb) 245 { 246 /* 247 * Reassemble IP fragments. 248 */ 249 struct net *net = dev_net(skb->dev); 250 251 if (ip_is_fragment(ip_hdr(skb))) { 252 if (ip_defrag(net, skb, IP_DEFRAG_LOCAL_DELIVER)) 253 return 0; 254 } 255 256 return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, 257 net, NULL, skb, skb->dev, NULL, 258 ip_local_deliver_finish); 259 } 260 261 static inline bool ip_rcv_options(struct sk_buff *skb) 262 { 263 struct ip_options *opt; 264 const struct iphdr *iph; 265 struct net_device *dev = skb->dev; 266 267 /* It looks as overkill, because not all 268 IP options require packet mangling. 269 But it is the easiest for now, especially taking 270 into account that combination of IP options 271 and running sniffer is extremely rare condition. 272 --ANK (980813) 273 */ 274 if (skb_cow(skb, skb_headroom(skb))) { 275 __IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INDISCARDS); 276 goto drop; 277 } 278 279 iph = ip_hdr(skb); 280 opt = &(IPCB(skb)->opt); 281 opt->optlen = iph->ihl*4 - sizeof(struct iphdr); 282 283 if (ip_options_compile(dev_net(dev), opt, skb)) { 284 __IP_INC_STATS(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 285 goto drop; 286 } 287 288 if (unlikely(opt->srr)) { 289 struct in_device *in_dev = __in_dev_get_rcu(dev); 290 291 if (in_dev) { 292 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 293 if (IN_DEV_LOG_MARTIANS(in_dev)) 294 net_info_ratelimited("source route option %pI4 -> %pI4\n", 295 &iph->saddr, 296 &iph->daddr); 297 goto drop; 298 } 299 } 300 301 if (ip_options_rcv_srr(skb)) 302 goto drop; 303 } 304 305 return false; 306 drop: 307 return true; 308 } 309 310 static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb) 311 { 312 const struct iphdr *iph = ip_hdr(skb); 313 int (*edemux)(struct sk_buff *skb); 314 struct net_device *dev = skb->dev; 315 struct rtable *rt; 316 int err; 317 318 /* if ingress device is enslaved to an L3 master device pass the 319 * skb to its handler for processing 320 */ 321 skb = l3mdev_ip_rcv(skb); 322 if (!skb) 323 return NET_RX_SUCCESS; 324 325 if (net->ipv4.sysctl_ip_early_demux && 326 !skb_dst(skb) && 327 !skb->sk && 328 !ip_is_fragment(iph)) { 329 const struct net_protocol *ipprot; 330 int protocol = iph->protocol; 331 332 ipprot = rcu_dereference(inet_protos[protocol]); 333 if (ipprot && (edemux = READ_ONCE(ipprot->early_demux))) { 334 err = edemux(skb); 335 if (unlikely(err)) 336 goto drop_error; 337 /* must reload iph, skb->head might have changed */ 338 iph = ip_hdr(skb); 339 } 340 } 341 342 /* 343 * Initialise the virtual path cache for the packet. It describes 344 * how the packet travels inside Linux networking. 345 */ 346 if (!skb_valid_dst(skb)) { 347 err = ip_route_input_noref(skb, iph->daddr, iph->saddr, 348 iph->tos, dev); 349 if (unlikely(err)) 350 goto drop_error; 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 drop_error: 403 if (err == -EXDEV) 404 __NET_INC_STATS(net, LINUX_MIB_IPRPFILTER); 405 goto drop; 406 } 407 408 /* 409 * Main IP Receive routine. 410 */ 411 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 412 { 413 const struct iphdr *iph; 414 struct net *net; 415 u32 len; 416 417 /* When the interface is in promisc. mode, drop all the crap 418 * that it receives, do not try to analyse it. 419 */ 420 if (skb->pkt_type == PACKET_OTHERHOST) 421 goto drop; 422 423 424 net = dev_net(dev); 425 __IP_UPD_PO_STATS(net, IPSTATS_MIB_IN, skb->len); 426 427 skb = skb_share_check(skb, GFP_ATOMIC); 428 if (!skb) { 429 __IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS); 430 goto out; 431 } 432 433 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 434 goto inhdr_error; 435 436 iph = ip_hdr(skb); 437 438 /* 439 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum. 440 * 441 * Is the datagram acceptable? 442 * 443 * 1. Length at least the size of an ip header 444 * 2. Version of 4 445 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 446 * 4. Doesn't have a bogus length 447 */ 448 449 if (iph->ihl < 5 || iph->version != 4) 450 goto inhdr_error; 451 452 BUILD_BUG_ON(IPSTATS_MIB_ECT1PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_1); 453 BUILD_BUG_ON(IPSTATS_MIB_ECT0PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_0); 454 BUILD_BUG_ON(IPSTATS_MIB_CEPKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_CE); 455 __IP_ADD_STATS(net, 456 IPSTATS_MIB_NOECTPKTS + (iph->tos & INET_ECN_MASK), 457 max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs)); 458 459 if (!pskb_may_pull(skb, iph->ihl*4)) 460 goto inhdr_error; 461 462 iph = ip_hdr(skb); 463 464 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 465 goto csum_error; 466 467 len = ntohs(iph->tot_len); 468 if (skb->len < len) { 469 __IP_INC_STATS(net, IPSTATS_MIB_INTRUNCATEDPKTS); 470 goto drop; 471 } else if (len < (iph->ihl*4)) 472 goto inhdr_error; 473 474 /* Our transport medium may have padded the buffer out. Now we know it 475 * is IP we can trim to the true length of the frame. 476 * Note this now means skb->len holds ntohs(iph->tot_len). 477 */ 478 if (pskb_trim_rcsum(skb, len)) { 479 __IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS); 480 goto drop; 481 } 482 483 skb->transport_header = skb->network_header + iph->ihl*4; 484 485 /* Remove any debris in the socket control block */ 486 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 487 IPCB(skb)->iif = skb->skb_iif; 488 489 /* Must drop socket now because of tproxy. */ 490 skb_orphan(skb); 491 492 return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, 493 net, NULL, skb, dev, NULL, 494 ip_rcv_finish); 495 496 csum_error: 497 __IP_INC_STATS(net, IPSTATS_MIB_CSUMERRORS); 498 inhdr_error: 499 __IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS); 500 drop: 501 kfree_skb(skb); 502 out: 503 return NET_RX_DROP; 504 } 505