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); 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) 229 raw_v4_input(skb, skb->nh.iph, hash); 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_finish(struct sk_buff *skb) 283 { 284 struct net_device *dev = skb->dev; 285 struct iphdr *iph = skb->nh.iph; 286 287 /* 288 * Initialise the virtual path cache for the packet. It describes 289 * how the packet travels inside Linux networking. 290 */ 291 if (skb->dst == NULL) { 292 if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev)) 293 goto drop; 294 } 295 296 #ifdef CONFIG_NET_CLS_ROUTE 297 if (skb->dst->tclassid) { 298 struct ip_rt_acct *st = ip_rt_acct + 256*smp_processor_id(); 299 u32 idx = skb->dst->tclassid; 300 st[idx&0xFF].o_packets++; 301 st[idx&0xFF].o_bytes+=skb->len; 302 st[(idx>>16)&0xFF].i_packets++; 303 st[(idx>>16)&0xFF].i_bytes+=skb->len; 304 } 305 #endif 306 307 if (iph->ihl > 5) { 308 struct ip_options *opt; 309 310 /* It looks as overkill, because not all 311 IP options require packet mangling. 312 But it is the easiest for now, especially taking 313 into account that combination of IP options 314 and running sniffer is extremely rare condition. 315 --ANK (980813) 316 */ 317 318 if (skb_cow(skb, skb_headroom(skb))) { 319 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 320 goto drop; 321 } 322 iph = skb->nh.iph; 323 324 if (ip_options_compile(NULL, skb)) 325 goto inhdr_error; 326 327 opt = &(IPCB(skb)->opt); 328 if (opt->srr) { 329 struct in_device *in_dev = in_dev_get(dev); 330 if (in_dev) { 331 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 332 if (IN_DEV_LOG_MARTIANS(in_dev) && net_ratelimit()) 333 printk(KERN_INFO "source route option %u.%u.%u.%u -> %u.%u.%u.%u\n", 334 NIPQUAD(iph->saddr), NIPQUAD(iph->daddr)); 335 in_dev_put(in_dev); 336 goto drop; 337 } 338 in_dev_put(in_dev); 339 } 340 if (ip_options_rcv_srr(skb)) 341 goto drop; 342 } 343 } 344 345 return dst_input(skb); 346 347 inhdr_error: 348 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 349 drop: 350 kfree_skb(skb); 351 return NET_RX_DROP; 352 } 353 354 /* 355 * Main IP Receive routine. 356 */ 357 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt) 358 { 359 struct iphdr *iph; 360 361 /* When the interface is in promisc. mode, drop all the crap 362 * that it receives, do not try to analyse it. 363 */ 364 if (skb->pkt_type == PACKET_OTHERHOST) 365 goto drop; 366 367 IP_INC_STATS_BH(IPSTATS_MIB_INRECEIVES); 368 369 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 370 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 371 goto out; 372 } 373 374 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 375 goto inhdr_error; 376 377 iph = skb->nh.iph; 378 379 /* 380 * RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum. 381 * 382 * Is the datagram acceptable? 383 * 384 * 1. Length at least the size of an ip header 385 * 2. Version of 4 386 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 387 * 4. Doesn't have a bogus length 388 */ 389 390 if (iph->ihl < 5 || iph->version != 4) 391 goto inhdr_error; 392 393 if (!pskb_may_pull(skb, iph->ihl*4)) 394 goto inhdr_error; 395 396 iph = skb->nh.iph; 397 398 if (ip_fast_csum((u8 *)iph, iph->ihl) != 0) 399 goto inhdr_error; 400 401 { 402 __u32 len = ntohs(iph->tot_len); 403 if (skb->len < len || len < (iph->ihl<<2)) 404 goto inhdr_error; 405 406 /* Our transport medium may have padded the buffer out. Now we know it 407 * is IP we can trim to the true length of the frame. 408 * Note this now means skb->len holds ntohs(iph->tot_len). 409 */ 410 if (pskb_trim_rcsum(skb, len)) { 411 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 412 goto drop; 413 } 414 } 415 416 return NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL, 417 ip_rcv_finish); 418 419 inhdr_error: 420 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 421 drop: 422 kfree_skb(skb); 423 out: 424 return NET_RX_DROP; 425 } 426 427 EXPORT_SYMBOL(ip_rcv); 428 EXPORT_SYMBOL(ip_statistics); 429