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 * Version: $Id: ip_input.c,v 1.55 2002/01/12 07:39:45 davem Exp $ 9 * 10 * Authors: Ross Biro 11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 12 * Donald Becker, <becker@super.org> 13 * Alan Cox, <Alan.Cox@linux.org> 14 * Richard Underwood 15 * Stefan Becker, <stefanb@yello.ping.de> 16 * Jorge Cwik, <jorge@laser.satlink.net> 17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 18 * 19 * 20 * Fixes: 21 * Alan Cox : Commented a couple of minor bits of surplus code 22 * Alan Cox : Undefining IP_FORWARD doesn't include the code 23 * (just stops a compiler warning). 24 * Alan Cox : Frames with >=MAX_ROUTE record routes, strict routes or loose routes 25 * are junked rather than corrupting things. 26 * Alan Cox : Frames to bad broadcast subnets are dumped 27 * We used to process them non broadcast and 28 * boy could that cause havoc. 29 * Alan Cox : ip_forward sets the free flag on the 30 * new frame it queues. Still crap because 31 * it copies the frame but at least it 32 * doesn't eat memory too. 33 * Alan Cox : Generic queue code and memory fixes. 34 * Fred Van Kempen : IP fragment support (borrowed from NET2E) 35 * Gerhard Koerting: Forward fragmented frames correctly. 36 * Gerhard Koerting: Fixes to my fix of the above 8-). 37 * Gerhard Koerting: IP interface addressing fix. 38 * Linus Torvalds : More robustness checks 39 * Alan Cox : Even more checks: Still not as robust as it ought to be 40 * Alan Cox : Save IP header pointer for later 41 * Alan Cox : ip option setting 42 * Alan Cox : Use ip_tos/ip_ttl settings 43 * Alan Cox : Fragmentation bogosity removed 44 * (Thanks to Mark.Bush@prg.ox.ac.uk) 45 * Dmitry Gorodchanin : Send of a raw packet crash fix. 46 * Alan Cox : Silly ip bug when an overlength 47 * fragment turns up. Now frees the 48 * queue. 49 * Linus Torvalds/ : Memory leakage on fragmentation 50 * Alan Cox : handling. 51 * Gerhard Koerting: Forwarding uses IP priority hints 52 * Teemu Rantanen : Fragment problems. 53 * Alan Cox : General cleanup, comments and reformat 54 * Alan Cox : SNMP statistics 55 * Alan Cox : BSD address rule semantics. Also see 56 * UDP as there is a nasty checksum issue 57 * if you do things the wrong way. 58 * Alan Cox : Always defrag, moved IP_FORWARD to the config.in file 59 * Alan Cox : IP options adjust sk->priority. 60 * Pedro Roque : Fix mtu/length error in ip_forward. 61 * Alan Cox : Avoid ip_chk_addr when possible. 62 * Richard Underwood : IP multicasting. 63 * Alan Cox : Cleaned up multicast handlers. 64 * Alan Cox : RAW sockets demultiplex in the BSD style. 65 * Gunther Mayer : Fix the SNMP reporting typo 66 * Alan Cox : Always in group 224.0.0.1 67 * Pauline Middelink : Fast ip_checksum update when forwarding 68 * Masquerading support. 69 * Alan Cox : Multicast loopback error for 224.0.0.1 70 * Alan Cox : IP_MULTICAST_LOOP option. 71 * Alan Cox : Use notifiers. 72 * Bjorn Ekwall : Removed ip_csum (from slhc.c too) 73 * Bjorn Ekwall : Moved ip_fast_csum to ip.h (inline!) 74 * Stefan Becker : Send out ICMP HOST REDIRECT 75 * Arnt Gulbrandsen : ip_build_xmit 76 * Alan Cox : Per socket routing cache 77 * Alan Cox : Fixed routing cache, added header cache. 78 * Alan Cox : Loopback didn't work right in original ip_build_xmit - fixed it. 79 * Alan Cox : Only send ICMP_REDIRECT if src/dest are the same net. 80 * Alan Cox : Incoming IP option handling. 81 * Alan Cox : Set saddr on raw output frames as per BSD. 82 * Alan Cox : Stopped broadcast source route explosions. 83 * Alan Cox : Can disable source routing 84 * Takeshi Sone : Masquerading didn't work. 85 * Dave Bonn,Alan Cox : Faster IP forwarding whenever possible. 86 * Alan Cox : Memory leaks, tramples, misc debugging. 87 * Alan Cox : Fixed multicast (by popular demand 8)) 88 * Alan Cox : Fixed forwarding (by even more popular demand 8)) 89 * Alan Cox : Fixed SNMP statistics [I think] 90 * Gerhard Koerting : IP fragmentation forwarding fix 91 * Alan Cox : Device lock against page fault. 92 * Alan Cox : IP_HDRINCL facility. 93 * Werner Almesberger : Zero fragment bug 94 * Alan Cox : RAW IP frame length bug 95 * Alan Cox : Outgoing firewall on build_xmit 96 * A.N.Kuznetsov : IP_OPTIONS support throughout the kernel 97 * Alan Cox : Multicast routing hooks 98 * Jos Vos : Do accounting *before* call_in_firewall 99 * Willy Konynenberg : Transparent proxying support 100 * 101 * 102 * 103 * To Fix: 104 * IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient 105 * and could be made very efficient with the addition of some virtual memory hacks to permit 106 * the allocation of a buffer that can then be 'grown' by twiddling page tables. 107 * Output fragmentation wants updating along with the buffer management to use a single 108 * interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet 109 * output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause 110 * fragmentation anyway. 111 * 112 * This program is free software; you can redistribute it and/or 113 * modify it under the terms of the GNU General Public License 114 * as published by the Free Software Foundation; either version 115 * 2 of the License, or (at your option) any later version. 116 */ 117 118 #include <asm/system.h> 119 #include <linux/module.h> 120 #include <linux/types.h> 121 #include <linux/kernel.h> 122 #include <linux/string.h> 123 #include <linux/errno.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 <linux/netfilter_ipv4.h> 145 #include <net/xfrm.h> 146 #include <linux/mroute.h> 147 #include <linux/netlink.h> 148 149 /* 150 * SNMP management statistics 151 */ 152 153 DEFINE_SNMP_STAT(struct ipstats_mib, ip_statistics) __read_mostly; 154 155 /* 156 * Process Router Attention IP option 157 */ 158 int ip_call_ra_chain(struct sk_buff *skb) 159 { 160 struct ip_ra_chain *ra; 161 u8 protocol = ip_hdr(skb)->protocol; 162 struct sock *last = NULL; 163 164 read_lock(&ip_ra_lock); 165 for (ra = ip_ra_chain; ra; ra = ra->next) { 166 struct sock *sk = ra->sk; 167 168 /* If socket is bound to an interface, only report 169 * the packet if it came from that interface. 170 */ 171 if (sk && inet_sk(sk)->num == protocol && 172 (!sk->sk_bound_dev_if || 173 sk->sk_bound_dev_if == skb->dev->ifindex)) { 174 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 175 skb = ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN); 176 if (skb == NULL) { 177 read_unlock(&ip_ra_lock); 178 return 1; 179 } 180 } 181 if (last) { 182 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); 183 if (skb2) 184 raw_rcv(last, skb2); 185 } 186 last = sk; 187 } 188 } 189 190 if (last) { 191 raw_rcv(last, skb); 192 read_unlock(&ip_ra_lock); 193 return 1; 194 } 195 read_unlock(&ip_ra_lock); 196 return 0; 197 } 198 199 static inline int ip_local_deliver_finish(struct sk_buff *skb) 200 { 201 __skb_pull(skb, ip_hdrlen(skb)); 202 203 /* Point into the IP datagram, just past the header. */ 204 skb_reset_transport_header(skb); 205 206 rcu_read_lock(); 207 { 208 /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */ 209 int protocol = ip_hdr(skb)->protocol; 210 int hash; 211 struct sock *raw_sk; 212 struct net_protocol *ipprot; 213 214 resubmit: 215 hash = protocol & (MAX_INET_PROTOS - 1); 216 raw_sk = sk_head(&raw_v4_htable[hash]); 217 218 /* If there maybe a raw socket we must check - if not we 219 * don't care less 220 */ 221 if (raw_sk && !raw_v4_input(skb, ip_hdr(skb), hash)) 222 raw_sk = NULL; 223 224 if ((ipprot = rcu_dereference(inet_protos[hash])) != NULL) { 225 int ret; 226 227 if (!ipprot->no_policy) { 228 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 229 kfree_skb(skb); 230 goto out; 231 } 232 nf_reset(skb); 233 } 234 ret = ipprot->handler(skb); 235 if (ret < 0) { 236 protocol = -ret; 237 goto resubmit; 238 } 239 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 240 } else { 241 if (!raw_sk) { 242 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 243 IP_INC_STATS_BH(IPSTATS_MIB_INUNKNOWNPROTOS); 244 icmp_send(skb, ICMP_DEST_UNREACH, 245 ICMP_PROT_UNREACH, 0); 246 } 247 } else 248 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 249 kfree_skb(skb); 250 } 251 } 252 out: 253 rcu_read_unlock(); 254 255 return 0; 256 } 257 258 /* 259 * Deliver IP Packets to the higher protocol layers. 260 */ 261 int ip_local_deliver(struct sk_buff *skb) 262 { 263 /* 264 * Reassemble IP fragments. 265 */ 266 267 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 268 skb = ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER); 269 if (!skb) 270 return 0; 271 } 272 273 return NF_HOOK(PF_INET, NF_IP_LOCAL_IN, skb, skb->dev, NULL, 274 ip_local_deliver_finish); 275 } 276 277 static inline int ip_rcv_options(struct sk_buff *skb) 278 { 279 struct ip_options *opt; 280 struct iphdr *iph; 281 struct net_device *dev = skb->dev; 282 283 /* It looks as overkill, because not all 284 IP options require packet mangling. 285 But it is the easiest for now, especially taking 286 into account that combination of IP options 287 and running sniffer is extremely rare condition. 288 --ANK (980813) 289 */ 290 if (skb_cow(skb, skb_headroom(skb))) { 291 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 292 goto drop; 293 } 294 295 iph = ip_hdr(skb); 296 297 if (ip_options_compile(NULL, skb)) { 298 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 299 goto drop; 300 } 301 302 opt = &(IPCB(skb)->opt); 303 if (unlikely(opt->srr)) { 304 struct in_device *in_dev = in_dev_get(dev); 305 if (in_dev) { 306 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 307 if (IN_DEV_LOG_MARTIANS(in_dev) && 308 net_ratelimit()) 309 printk(KERN_INFO "source route option " 310 "%u.%u.%u.%u -> %u.%u.%u.%u\n", 311 NIPQUAD(iph->saddr), 312 NIPQUAD(iph->daddr)); 313 in_dev_put(in_dev); 314 goto drop; 315 } 316 317 in_dev_put(in_dev); 318 } 319 320 if (ip_options_rcv_srr(skb)) 321 goto drop; 322 } 323 324 return 0; 325 drop: 326 return -1; 327 } 328 329 static inline int ip_rcv_finish(struct sk_buff *skb) 330 { 331 const struct iphdr *iph = ip_hdr(skb); 332 struct rtable *rt; 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->dst == NULL) { 339 int err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, 340 skb->dev); 341 if (unlikely(err)) { 342 if (err == -EHOSTUNREACH) 343 IP_INC_STATS_BH(IPSTATS_MIB_INADDRERRORS); 344 else if (err == -ENETUNREACH) 345 IP_INC_STATS_BH(IPSTATS_MIB_INNOROUTES); 346 goto drop; 347 } 348 } 349 350 #ifdef CONFIG_NET_CLS_ROUTE 351 if (unlikely(skb->dst->tclassid)) { 352 struct ip_rt_acct *st = ip_rt_acct + 256*smp_processor_id(); 353 u32 idx = skb->dst->tclassid; 354 st[idx&0xFF].o_packets++; 355 st[idx&0xFF].o_bytes+=skb->len; 356 st[(idx>>16)&0xFF].i_packets++; 357 st[(idx>>16)&0xFF].i_bytes+=skb->len; 358 } 359 #endif 360 361 if (iph->ihl > 5 && ip_rcv_options(skb)) 362 goto drop; 363 364 rt = (struct rtable*)skb->dst; 365 if (rt->rt_type == RTN_MULTICAST) 366 IP_INC_STATS_BH(IPSTATS_MIB_INMCASTPKTS); 367 else if (rt->rt_type == RTN_BROADCAST) 368 IP_INC_STATS_BH(IPSTATS_MIB_INBCASTPKTS); 369 370 return dst_input(skb); 371 372 drop: 373 kfree_skb(skb); 374 return NET_RX_DROP; 375 } 376 377 /* 378 * Main IP Receive routine. 379 */ 380 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 381 { 382 struct iphdr *iph; 383 u32 len; 384 385 if (dev->nd_net != &init_net) 386 goto drop; 387 388 /* When the interface is in promisc. mode, drop all the crap 389 * that it receives, do not try to analyse it. 390 */ 391 if (skb->pkt_type == PACKET_OTHERHOST) 392 goto drop; 393 394 IP_INC_STATS_BH(IPSTATS_MIB_INRECEIVES); 395 396 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 397 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 398 goto out; 399 } 400 401 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 402 goto inhdr_error; 403 404 iph = ip_hdr(skb); 405 406 /* 407 * RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum. 408 * 409 * Is the datagram acceptable? 410 * 411 * 1. Length at least the size of an ip header 412 * 2. Version of 4 413 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 414 * 4. Doesn't have a bogus length 415 */ 416 417 if (iph->ihl < 5 || iph->version != 4) 418 goto inhdr_error; 419 420 if (!pskb_may_pull(skb, iph->ihl*4)) 421 goto inhdr_error; 422 423 iph = ip_hdr(skb); 424 425 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 426 goto inhdr_error; 427 428 len = ntohs(iph->tot_len); 429 if (skb->len < len) { 430 IP_INC_STATS_BH(IPSTATS_MIB_INTRUNCATEDPKTS); 431 goto drop; 432 } else if (len < (iph->ihl*4)) 433 goto inhdr_error; 434 435 /* Our transport medium may have padded the buffer out. Now we know it 436 * is IP we can trim to the true length of the frame. 437 * Note this now means skb->len holds ntohs(iph->tot_len). 438 */ 439 if (pskb_trim_rcsum(skb, len)) { 440 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 441 goto drop; 442 } 443 444 /* Remove any debris in the socket control block */ 445 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 446 447 return NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL, 448 ip_rcv_finish); 449 450 inhdr_error: 451 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 452 drop: 453 kfree_skb(skb); 454 out: 455 return NET_RX_DROP; 456 } 457 458 EXPORT_SYMBOL(ip_statistics); 459