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 if (ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN)) { 176 read_unlock(&ip_ra_lock); 177 return 1; 178 } 179 } 180 if (last) { 181 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); 182 if (skb2) 183 raw_rcv(last, skb2); 184 } 185 last = sk; 186 } 187 } 188 189 if (last) { 190 raw_rcv(last, skb); 191 read_unlock(&ip_ra_lock); 192 return 1; 193 } 194 read_unlock(&ip_ra_lock); 195 return 0; 196 } 197 198 static int ip_local_deliver_finish(struct sk_buff *skb) 199 { 200 __skb_pull(skb, ip_hdrlen(skb)); 201 202 /* Point into the IP datagram, just past the header. */ 203 skb_reset_transport_header(skb); 204 205 rcu_read_lock(); 206 { 207 /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */ 208 int protocol = ip_hdr(skb)->protocol; 209 int hash; 210 struct sock *raw_sk; 211 struct net_protocol *ipprot; 212 213 resubmit: 214 hash = protocol & (MAX_INET_PROTOS - 1); 215 raw_sk = sk_head(&raw_v4_htable[hash]); 216 217 /* If there maybe a raw socket we must check - if not we 218 * don't care less 219 */ 220 if (raw_sk && !raw_v4_input(skb, ip_hdr(skb), hash)) 221 raw_sk = NULL; 222 223 if ((ipprot = rcu_dereference(inet_protos[hash])) != NULL) { 224 int ret; 225 226 if (!ipprot->no_policy) { 227 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 228 kfree_skb(skb); 229 goto out; 230 } 231 nf_reset(skb); 232 } 233 ret = ipprot->handler(skb); 234 if (ret < 0) { 235 protocol = -ret; 236 goto resubmit; 237 } 238 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 239 } else { 240 if (!raw_sk) { 241 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 242 IP_INC_STATS_BH(IPSTATS_MIB_INUNKNOWNPROTOS); 243 icmp_send(skb, ICMP_DEST_UNREACH, 244 ICMP_PROT_UNREACH, 0); 245 } 246 } else 247 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 248 kfree_skb(skb); 249 } 250 } 251 out: 252 rcu_read_unlock(); 253 254 return 0; 255 } 256 257 /* 258 * Deliver IP Packets to the higher protocol layers. 259 */ 260 int ip_local_deliver(struct sk_buff *skb) 261 { 262 /* 263 * Reassemble IP fragments. 264 */ 265 266 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 267 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER)) 268 return 0; 269 } 270 271 return NF_HOOK(PF_INET, NF_IP_LOCAL_IN, skb, skb->dev, NULL, 272 ip_local_deliver_finish); 273 } 274 275 static inline int ip_rcv_options(struct sk_buff *skb) 276 { 277 struct ip_options *opt; 278 struct iphdr *iph; 279 struct net_device *dev = skb->dev; 280 281 /* It looks as overkill, because not all 282 IP options require packet mangling. 283 But it is the easiest for now, especially taking 284 into account that combination of IP options 285 and running sniffer is extremely rare condition. 286 --ANK (980813) 287 */ 288 if (skb_cow(skb, skb_headroom(skb))) { 289 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 290 goto drop; 291 } 292 293 iph = ip_hdr(skb); 294 295 if (ip_options_compile(NULL, skb)) { 296 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 297 goto drop; 298 } 299 300 opt = &(IPCB(skb)->opt); 301 if (unlikely(opt->srr)) { 302 struct in_device *in_dev = in_dev_get(dev); 303 if (in_dev) { 304 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 305 if (IN_DEV_LOG_MARTIANS(in_dev) && 306 net_ratelimit()) 307 printk(KERN_INFO "source route option " 308 "%u.%u.%u.%u -> %u.%u.%u.%u\n", 309 NIPQUAD(iph->saddr), 310 NIPQUAD(iph->daddr)); 311 in_dev_put(in_dev); 312 goto drop; 313 } 314 315 in_dev_put(in_dev); 316 } 317 318 if (ip_options_rcv_srr(skb)) 319 goto drop; 320 } 321 322 return 0; 323 drop: 324 return -1; 325 } 326 327 static int ip_rcv_finish(struct sk_buff *skb) 328 { 329 const struct iphdr *iph = ip_hdr(skb); 330 struct rtable *rt; 331 332 /* 333 * Initialise the virtual path cache for the packet. It describes 334 * how the packet travels inside Linux networking. 335 */ 336 if (skb->dst == NULL) { 337 int err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, 338 skb->dev); 339 if (unlikely(err)) { 340 if (err == -EHOSTUNREACH) 341 IP_INC_STATS_BH(IPSTATS_MIB_INADDRERRORS); 342 else if (err == -ENETUNREACH) 343 IP_INC_STATS_BH(IPSTATS_MIB_INNOROUTES); 344 goto drop; 345 } 346 } 347 348 #ifdef CONFIG_NET_CLS_ROUTE 349 if (unlikely(skb->dst->tclassid)) { 350 struct ip_rt_acct *st = ip_rt_acct + 256*smp_processor_id(); 351 u32 idx = skb->dst->tclassid; 352 st[idx&0xFF].o_packets++; 353 st[idx&0xFF].o_bytes+=skb->len; 354 st[(idx>>16)&0xFF].i_packets++; 355 st[(idx>>16)&0xFF].i_bytes+=skb->len; 356 } 357 #endif 358 359 if (iph->ihl > 5 && ip_rcv_options(skb)) 360 goto drop; 361 362 rt = (struct rtable*)skb->dst; 363 if (rt->rt_type == RTN_MULTICAST) 364 IP_INC_STATS_BH(IPSTATS_MIB_INMCASTPKTS); 365 else if (rt->rt_type == RTN_BROADCAST) 366 IP_INC_STATS_BH(IPSTATS_MIB_INBCASTPKTS); 367 368 return dst_input(skb); 369 370 drop: 371 kfree_skb(skb); 372 return NET_RX_DROP; 373 } 374 375 /* 376 * Main IP Receive routine. 377 */ 378 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 379 { 380 struct iphdr *iph; 381 u32 len; 382 383 if (dev->nd_net != &init_net) 384 goto drop; 385 386 /* When the interface is in promisc. mode, drop all the crap 387 * that it receives, do not try to analyse it. 388 */ 389 if (skb->pkt_type == PACKET_OTHERHOST) 390 goto drop; 391 392 IP_INC_STATS_BH(IPSTATS_MIB_INRECEIVES); 393 394 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 395 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 396 goto out; 397 } 398 399 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 400 goto inhdr_error; 401 402 iph = ip_hdr(skb); 403 404 /* 405 * RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum. 406 * 407 * Is the datagram acceptable? 408 * 409 * 1. Length at least the size of an ip header 410 * 2. Version of 4 411 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 412 * 4. Doesn't have a bogus length 413 */ 414 415 if (iph->ihl < 5 || iph->version != 4) 416 goto inhdr_error; 417 418 if (!pskb_may_pull(skb, iph->ihl*4)) 419 goto inhdr_error; 420 421 iph = ip_hdr(skb); 422 423 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 424 goto inhdr_error; 425 426 len = ntohs(iph->tot_len); 427 if (skb->len < len) { 428 IP_INC_STATS_BH(IPSTATS_MIB_INTRUNCATEDPKTS); 429 goto drop; 430 } else if (len < (iph->ihl*4)) 431 goto inhdr_error; 432 433 /* Our transport medium may have padded the buffer out. Now we know it 434 * is IP we can trim to the true length of the frame. 435 * Note this now means skb->len holds ntohs(iph->tot_len). 436 */ 437 if (pskb_trim_rcsum(skb, len)) { 438 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 439 goto drop; 440 } 441 442 /* Remove any debris in the socket control block */ 443 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 444 445 return NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL, 446 ip_rcv_finish); 447 448 inhdr_error: 449 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 450 drop: 451 kfree_skb(skb); 452 out: 453 return NET_RX_DROP; 454 } 455 456 EXPORT_SYMBOL(ip_statistics); 457