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, <bir7@leland.Stanford.Edu> 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); 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 } 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 int ihl = skb->nh.iph->ihl*4; 202 203 #ifdef CONFIG_NETFILTER_DEBUG 204 nf_debug_ip_local_deliver(skb); 205 #endif /*CONFIG_NETFILTER_DEBUG*/ 206 207 __skb_pull(skb, ihl); 208 209 /* Free reference early: we don't need it any more, and it may 210 hold ip_conntrack module loaded indefinitely. */ 211 nf_reset(skb); 212 213 /* Point into the IP datagram, just past the header. */ 214 skb->h.raw = skb->data; 215 216 rcu_read_lock(); 217 { 218 /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */ 219 int protocol = skb->nh.iph->protocol; 220 int hash; 221 struct sock *raw_sk; 222 struct net_protocol *ipprot; 223 224 resubmit: 225 hash = protocol & (MAX_INET_PROTOS - 1); 226 raw_sk = sk_head(&raw_v4_htable[hash]); 227 228 /* If there maybe a raw socket we must check - if not we 229 * don't care less 230 */ 231 if (raw_sk) 232 raw_v4_input(skb, skb->nh.iph, hash); 233 234 if ((ipprot = rcu_dereference(inet_protos[hash])) != NULL) { 235 int ret; 236 237 if (!ipprot->no_policy && 238 !xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 239 kfree_skb(skb); 240 goto out; 241 } 242 ret = ipprot->handler(skb); 243 if (ret < 0) { 244 protocol = -ret; 245 goto resubmit; 246 } 247 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 248 } else { 249 if (!raw_sk) { 250 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 251 IP_INC_STATS_BH(IPSTATS_MIB_INUNKNOWNPROTOS); 252 icmp_send(skb, ICMP_DEST_UNREACH, 253 ICMP_PROT_UNREACH, 0); 254 } 255 } else 256 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 257 kfree_skb(skb); 258 } 259 } 260 out: 261 rcu_read_unlock(); 262 263 return 0; 264 } 265 266 /* 267 * Deliver IP Packets to the higher protocol layers. 268 */ 269 int ip_local_deliver(struct sk_buff *skb) 270 { 271 /* 272 * Reassemble IP fragments. 273 */ 274 275 if (skb->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) { 276 skb = ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER); 277 if (!skb) 278 return 0; 279 } 280 281 return NF_HOOK(PF_INET, NF_IP_LOCAL_IN, skb, skb->dev, NULL, 282 ip_local_deliver_finish); 283 } 284 285 static inline int ip_rcv_finish(struct sk_buff *skb) 286 { 287 struct net_device *dev = skb->dev; 288 struct iphdr *iph = skb->nh.iph; 289 290 /* 291 * Initialise the virtual path cache for the packet. It describes 292 * how the packet travels inside Linux networking. 293 */ 294 if (skb->dst == NULL) { 295 if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev)) 296 goto drop; 297 } 298 299 #ifdef CONFIG_NET_CLS_ROUTE 300 if (skb->dst->tclassid) { 301 struct ip_rt_acct *st = ip_rt_acct + 256*smp_processor_id(); 302 u32 idx = skb->dst->tclassid; 303 st[idx&0xFF].o_packets++; 304 st[idx&0xFF].o_bytes+=skb->len; 305 st[(idx>>16)&0xFF].i_packets++; 306 st[(idx>>16)&0xFF].i_bytes+=skb->len; 307 } 308 #endif 309 310 if (iph->ihl > 5) { 311 struct ip_options *opt; 312 313 /* It looks as overkill, because not all 314 IP options require packet mangling. 315 But it is the easiest for now, especially taking 316 into account that combination of IP options 317 and running sniffer is extremely rare condition. 318 --ANK (980813) 319 */ 320 321 if (skb_cow(skb, skb_headroom(skb))) { 322 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 323 goto drop; 324 } 325 iph = skb->nh.iph; 326 327 if (ip_options_compile(NULL, skb)) 328 goto inhdr_error; 329 330 opt = &(IPCB(skb)->opt); 331 if (opt->srr) { 332 struct in_device *in_dev = in_dev_get(dev); 333 if (in_dev) { 334 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 335 if (IN_DEV_LOG_MARTIANS(in_dev) && net_ratelimit()) 336 printk(KERN_INFO "source route option %u.%u.%u.%u -> %u.%u.%u.%u\n", 337 NIPQUAD(iph->saddr), NIPQUAD(iph->daddr)); 338 in_dev_put(in_dev); 339 goto drop; 340 } 341 in_dev_put(in_dev); 342 } 343 if (ip_options_rcv_srr(skb)) 344 goto drop; 345 } 346 } 347 348 return dst_input(skb); 349 350 inhdr_error: 351 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 352 drop: 353 kfree_skb(skb); 354 return NET_RX_DROP; 355 } 356 357 /* 358 * Main IP Receive routine. 359 */ 360 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt) 361 { 362 struct iphdr *iph; 363 364 /* When the interface is in promisc. mode, drop all the crap 365 * that it receives, do not try to analyse it. 366 */ 367 if (skb->pkt_type == PACKET_OTHERHOST) 368 goto drop; 369 370 IP_INC_STATS_BH(IPSTATS_MIB_INRECEIVES); 371 372 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 373 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 374 goto out; 375 } 376 377 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 378 goto inhdr_error; 379 380 iph = skb->nh.iph; 381 382 /* 383 * RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum. 384 * 385 * Is the datagram acceptable? 386 * 387 * 1. Length at least the size of an ip header 388 * 2. Version of 4 389 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 390 * 4. Doesn't have a bogus length 391 */ 392 393 if (iph->ihl < 5 || iph->version != 4) 394 goto inhdr_error; 395 396 if (!pskb_may_pull(skb, iph->ihl*4)) 397 goto inhdr_error; 398 399 iph = skb->nh.iph; 400 401 if (ip_fast_csum((u8 *)iph, iph->ihl) != 0) 402 goto inhdr_error; 403 404 { 405 __u32 len = ntohs(iph->tot_len); 406 if (skb->len < len || len < (iph->ihl<<2)) 407 goto inhdr_error; 408 409 /* Our transport medium may have padded the buffer out. Now we know it 410 * is IP we can trim to the true length of the frame. 411 * Note this now means skb->len holds ntohs(iph->tot_len). 412 */ 413 if (pskb_trim_rcsum(skb, len)) { 414 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 415 goto drop; 416 } 417 } 418 419 return NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL, 420 ip_rcv_finish); 421 422 inhdr_error: 423 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 424 drop: 425 kfree_skb(skb); 426 out: 427 return NET_RX_DROP; 428 } 429 430 EXPORT_SYMBOL(ip_rcv); 431 EXPORT_SYMBOL(ip_statistics); 432