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 struct net_device *dev = skb->dev; 164 165 read_lock(&ip_ra_lock); 166 for (ra = ip_ra_chain; ra; ra = ra->next) { 167 struct sock *sk = ra->sk; 168 169 /* If socket is bound to an interface, only report 170 * the packet if it came from that interface. 171 */ 172 if (sk && inet_sk(sk)->num == protocol && 173 (!sk->sk_bound_dev_if || 174 sk->sk_bound_dev_if == dev->ifindex) && 175 sk->sk_net == dev_net(dev)) { 176 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 177 if (ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN)) { 178 read_unlock(&ip_ra_lock); 179 return 1; 180 } 181 } 182 if (last) { 183 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); 184 if (skb2) 185 raw_rcv(last, skb2); 186 } 187 last = sk; 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 int ip_local_deliver_finish(struct sk_buff *skb) 201 { 202 struct net *net = dev_net(skb->dev); 203 204 __skb_pull(skb, ip_hdrlen(skb)); 205 206 /* Point into the IP datagram, just past the header. */ 207 skb_reset_transport_header(skb); 208 209 rcu_read_lock(); 210 { 211 int protocol = ip_hdr(skb)->protocol; 212 int hash, raw; 213 struct net_protocol *ipprot; 214 215 resubmit: 216 raw = raw_local_deliver(skb, protocol); 217 218 hash = protocol & (MAX_INET_PROTOS - 1); 219 ipprot = rcu_dereference(inet_protos[hash]); 220 if (ipprot != NULL && (net == &init_net || ipprot->netns_ok)) { 221 int ret; 222 223 if (!ipprot->no_policy) { 224 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 225 kfree_skb(skb); 226 goto out; 227 } 228 nf_reset(skb); 229 } 230 ret = ipprot->handler(skb); 231 if (ret < 0) { 232 protocol = -ret; 233 goto resubmit; 234 } 235 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 236 } else { 237 if (!raw) { 238 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 239 IP_INC_STATS_BH(IPSTATS_MIB_INUNKNOWNPROTOS); 240 icmp_send(skb, ICMP_DEST_UNREACH, 241 ICMP_PROT_UNREACH, 0); 242 } 243 } else 244 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 245 kfree_skb(skb); 246 } 247 } 248 out: 249 rcu_read_unlock(); 250 251 return 0; 252 } 253 254 /* 255 * Deliver IP Packets to the higher protocol layers. 256 */ 257 int ip_local_deliver(struct sk_buff *skb) 258 { 259 /* 260 * Reassemble IP fragments. 261 */ 262 263 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 264 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER)) 265 return 0; 266 } 267 268 return NF_HOOK(PF_INET, NF_INET_LOCAL_IN, skb, skb->dev, NULL, 269 ip_local_deliver_finish); 270 } 271 272 static inline int ip_rcv_options(struct sk_buff *skb) 273 { 274 struct ip_options *opt; 275 struct iphdr *iph; 276 struct net_device *dev = skb->dev; 277 278 /* It looks as overkill, because not all 279 IP options require packet mangling. 280 But it is the easiest for now, especially taking 281 into account that combination of IP options 282 and running sniffer is extremely rare condition. 283 --ANK (980813) 284 */ 285 if (skb_cow(skb, skb_headroom(skb))) { 286 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 287 goto drop; 288 } 289 290 iph = ip_hdr(skb); 291 opt = &(IPCB(skb)->opt); 292 opt->optlen = iph->ihl*4 - sizeof(struct iphdr); 293 294 if (ip_options_compile(dev_net(dev), opt, skb)) { 295 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 296 goto drop; 297 } 298 299 if (unlikely(opt->srr)) { 300 struct in_device *in_dev = in_dev_get(dev); 301 if (in_dev) { 302 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 303 if (IN_DEV_LOG_MARTIANS(in_dev) && 304 net_ratelimit()) 305 printk(KERN_INFO "source route option " 306 "%u.%u.%u.%u -> %u.%u.%u.%u\n", 307 NIPQUAD(iph->saddr), 308 NIPQUAD(iph->daddr)); 309 in_dev_put(in_dev); 310 goto drop; 311 } 312 313 in_dev_put(in_dev); 314 } 315 316 if (ip_options_rcv_srr(skb)) 317 goto drop; 318 } 319 320 return 0; 321 drop: 322 return -1; 323 } 324 325 static int ip_rcv_finish(struct sk_buff *skb) 326 { 327 const struct iphdr *iph = ip_hdr(skb); 328 struct rtable *rt; 329 330 /* 331 * Initialise the virtual path cache for the packet. It describes 332 * how the packet travels inside Linux networking. 333 */ 334 if (skb->dst == NULL) { 335 int err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, 336 skb->dev); 337 if (unlikely(err)) { 338 if (err == -EHOSTUNREACH) 339 IP_INC_STATS_BH(IPSTATS_MIB_INADDRERRORS); 340 else if (err == -ENETUNREACH) 341 IP_INC_STATS_BH(IPSTATS_MIB_INNOROUTES); 342 goto drop; 343 } 344 } 345 346 #ifdef CONFIG_NET_CLS_ROUTE 347 if (unlikely(skb->dst->tclassid)) { 348 struct ip_rt_acct *st = per_cpu_ptr(ip_rt_acct, smp_processor_id()); 349 u32 idx = skb->dst->tclassid; 350 st[idx&0xFF].o_packets++; 351 st[idx&0xFF].o_bytes+=skb->len; 352 st[(idx>>16)&0xFF].i_packets++; 353 st[(idx>>16)&0xFF].i_bytes+=skb->len; 354 } 355 #endif 356 357 if (iph->ihl > 5 && ip_rcv_options(skb)) 358 goto drop; 359 360 rt = skb->rtable; 361 if (rt->rt_type == RTN_MULTICAST) 362 IP_INC_STATS_BH(IPSTATS_MIB_INMCASTPKTS); 363 else if (rt->rt_type == RTN_BROADCAST) 364 IP_INC_STATS_BH(IPSTATS_MIB_INBCASTPKTS); 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 = ip_hdr(skb); 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 = ip_hdr(skb); 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) { 423 IP_INC_STATS_BH(IPSTATS_MIB_INTRUNCATEDPKTS); 424 goto drop; 425 } else if (len < (iph->ihl*4)) 426 goto inhdr_error; 427 428 /* Our transport medium may have padded the buffer out. Now we know it 429 * is IP we can trim to the true length of the frame. 430 * Note this now means skb->len holds ntohs(iph->tot_len). 431 */ 432 if (pskb_trim_rcsum(skb, len)) { 433 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 434 goto drop; 435 } 436 437 /* Remove any debris in the socket control block */ 438 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 439 440 return NF_HOOK(PF_INET, NF_INET_PRE_ROUTING, skb, dev, NULL, 441 ip_rcv_finish); 442 443 inhdr_error: 444 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 445 drop: 446 kfree_skb(skb); 447 out: 448 return NET_RX_DROP; 449 } 450 451 EXPORT_SYMBOL(ip_statistics); 452