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 #include <linux/config.h> 125 126 #include <linux/net.h> 127 #include <linux/socket.h> 128 #include <linux/sockios.h> 129 #include <linux/in.h> 130 #include <linux/inet.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 = skb->nh.iph->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 (skb->nh.iph->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 nf_reset(skb); 188 } 189 } 190 191 if (last) { 192 raw_rcv(last, skb); 193 read_unlock(&ip_ra_lock); 194 return 1; 195 } 196 read_unlock(&ip_ra_lock); 197 return 0; 198 } 199 200 static inline int ip_local_deliver_finish(struct sk_buff *skb) 201 { 202 int ihl = skb->nh.iph->ihl*4; 203 204 __skb_pull(skb, ihl); 205 206 /* Free reference early: we don't need it any more, and it may 207 hold ip_conntrack module loaded indefinitely. */ 208 nf_reset(skb); 209 210 /* Point into the IP datagram, just past the header. */ 211 skb->h.raw = skb->data; 212 213 rcu_read_lock(); 214 { 215 /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */ 216 int protocol = skb->nh.iph->protocol; 217 int hash; 218 struct sock *raw_sk; 219 struct net_protocol *ipprot; 220 221 resubmit: 222 hash = protocol & (MAX_INET_PROTOS - 1); 223 raw_sk = sk_head(&raw_v4_htable[hash]); 224 225 /* If there maybe a raw socket we must check - if not we 226 * don't care less 227 */ 228 if (raw_sk && !raw_v4_input(skb, skb->nh.iph, hash)) 229 raw_sk = NULL; 230 231 if ((ipprot = rcu_dereference(inet_protos[hash])) != NULL) { 232 int ret; 233 234 if (!ipprot->no_policy && 235 !xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 236 kfree_skb(skb); 237 goto out; 238 } 239 ret = ipprot->handler(skb); 240 if (ret < 0) { 241 protocol = -ret; 242 goto resubmit; 243 } 244 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 245 } else { 246 if (!raw_sk) { 247 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 248 IP_INC_STATS_BH(IPSTATS_MIB_INUNKNOWNPROTOS); 249 icmp_send(skb, ICMP_DEST_UNREACH, 250 ICMP_PROT_UNREACH, 0); 251 } 252 } else 253 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 254 kfree_skb(skb); 255 } 256 } 257 out: 258 rcu_read_unlock(); 259 260 return 0; 261 } 262 263 /* 264 * Deliver IP Packets to the higher protocol layers. 265 */ 266 int ip_local_deliver(struct sk_buff *skb) 267 { 268 /* 269 * Reassemble IP fragments. 270 */ 271 272 if (skb->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) { 273 skb = ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER); 274 if (!skb) 275 return 0; 276 } 277 278 return NF_HOOK(PF_INET, NF_IP_LOCAL_IN, skb, skb->dev, NULL, 279 ip_local_deliver_finish); 280 } 281 282 static inline int ip_rcv_options(struct sk_buff *skb) 283 { 284 struct ip_options *opt; 285 struct iphdr *iph; 286 struct net_device *dev = skb->dev; 287 288 /* It looks as overkill, because not all 289 IP options require packet mangling. 290 But it is the easiest for now, especially taking 291 into account that combination of IP options 292 and running sniffer is extremely rare condition. 293 --ANK (980813) 294 */ 295 if (skb_cow(skb, skb_headroom(skb))) { 296 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 297 goto drop; 298 } 299 300 iph = skb->nh.iph; 301 302 if (ip_options_compile(NULL, skb)) { 303 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 304 goto drop; 305 } 306 307 opt = &(IPCB(skb)->opt); 308 if (unlikely(opt->srr)) { 309 struct in_device *in_dev = in_dev_get(dev); 310 if (in_dev) { 311 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 312 if (IN_DEV_LOG_MARTIANS(in_dev) && 313 net_ratelimit()) 314 printk(KERN_INFO "source route option " 315 "%u.%u.%u.%u -> %u.%u.%u.%u\n", 316 NIPQUAD(iph->saddr), 317 NIPQUAD(iph->daddr)); 318 in_dev_put(in_dev); 319 goto drop; 320 } 321 322 in_dev_put(in_dev); 323 } 324 325 if (ip_options_rcv_srr(skb)) 326 goto drop; 327 } 328 329 return 0; 330 drop: 331 return -1; 332 } 333 334 static inline int ip_rcv_finish(struct sk_buff *skb) 335 { 336 struct iphdr *iph = skb->nh.iph; 337 338 /* 339 * Initialise the virtual path cache for the packet. It describes 340 * how the packet travels inside Linux networking. 341 */ 342 if (likely(skb->dst == NULL)) { 343 int err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, 344 skb->dev); 345 if (unlikely(err)) { 346 if (err == -EHOSTUNREACH) 347 IP_INC_STATS_BH(IPSTATS_MIB_INADDRERRORS); 348 goto drop; 349 } 350 } 351 352 #ifdef CONFIG_NET_CLS_ROUTE 353 if (unlikely(skb->dst->tclassid)) { 354 struct ip_rt_acct *st = ip_rt_acct + 256*smp_processor_id(); 355 u32 idx = skb->dst->tclassid; 356 st[idx&0xFF].o_packets++; 357 st[idx&0xFF].o_bytes+=skb->len; 358 st[(idx>>16)&0xFF].i_packets++; 359 st[(idx>>16)&0xFF].i_bytes+=skb->len; 360 } 361 #endif 362 363 if (iph->ihl > 5 && ip_rcv_options(skb)) 364 goto drop; 365 366 return dst_input(skb); 367 368 drop: 369 kfree_skb(skb); 370 return NET_RX_DROP; 371 } 372 373 /* 374 * Main IP Receive routine. 375 */ 376 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 377 { 378 struct iphdr *iph; 379 u32 len; 380 381 /* When the interface is in promisc. mode, drop all the crap 382 * that it receives, do not try to analyse it. 383 */ 384 if (skb->pkt_type == PACKET_OTHERHOST) 385 goto drop; 386 387 IP_INC_STATS_BH(IPSTATS_MIB_INRECEIVES); 388 389 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 390 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 391 goto out; 392 } 393 394 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 395 goto inhdr_error; 396 397 iph = skb->nh.iph; 398 399 /* 400 * RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum. 401 * 402 * Is the datagram acceptable? 403 * 404 * 1. Length at least the size of an ip header 405 * 2. Version of 4 406 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 407 * 4. Doesn't have a bogus length 408 */ 409 410 if (iph->ihl < 5 || iph->version != 4) 411 goto inhdr_error; 412 413 if (!pskb_may_pull(skb, iph->ihl*4)) 414 goto inhdr_error; 415 416 iph = skb->nh.iph; 417 418 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 419 goto inhdr_error; 420 421 len = ntohs(iph->tot_len); 422 if (skb->len < len || len < (iph->ihl*4)) 423 goto inhdr_error; 424 425 /* Our transport medium may have padded the buffer out. Now we know it 426 * is IP we can trim to the true length of the frame. 427 * Note this now means skb->len holds ntohs(iph->tot_len). 428 */ 429 if (pskb_trim_rcsum(skb, len)) { 430 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 431 goto drop; 432 } 433 434 return NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL, 435 ip_rcv_finish); 436 437 inhdr_error: 438 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 439 drop: 440 kfree_skb(skb); 441 out: 442 return NET_RX_DROP; 443 } 444 445 EXPORT_SYMBOL(ip_statistics); 446