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