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 int protocol = ip_hdr(skb)->protocol; 208 int hash, raw; 209 struct net_protocol *ipprot; 210 211 resubmit: 212 raw = raw_local_deliver(skb, protocol); 213 214 hash = protocol & (MAX_INET_PROTOS - 1); 215 if ((ipprot = rcu_dereference(inet_protos[hash])) != NULL) { 216 int ret; 217 218 if (!ipprot->no_policy) { 219 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 220 kfree_skb(skb); 221 goto out; 222 } 223 nf_reset(skb); 224 } 225 ret = ipprot->handler(skb); 226 if (ret < 0) { 227 protocol = -ret; 228 goto resubmit; 229 } 230 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 231 } else { 232 if (!raw) { 233 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 234 IP_INC_STATS_BH(IPSTATS_MIB_INUNKNOWNPROTOS); 235 icmp_send(skb, ICMP_DEST_UNREACH, 236 ICMP_PROT_UNREACH, 0); 237 } 238 } else 239 IP_INC_STATS_BH(IPSTATS_MIB_INDELIVERS); 240 kfree_skb(skb); 241 } 242 } 243 out: 244 rcu_read_unlock(); 245 246 return 0; 247 } 248 249 /* 250 * Deliver IP Packets to the higher protocol layers. 251 */ 252 int ip_local_deliver(struct sk_buff *skb) 253 { 254 /* 255 * Reassemble IP fragments. 256 */ 257 258 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 259 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER)) 260 return 0; 261 } 262 263 return NF_HOOK(PF_INET, NF_INET_LOCAL_IN, skb, skb->dev, NULL, 264 ip_local_deliver_finish); 265 } 266 267 static inline int ip_rcv_options(struct sk_buff *skb) 268 { 269 struct ip_options *opt; 270 struct iphdr *iph; 271 struct net_device *dev = skb->dev; 272 273 /* It looks as overkill, because not all 274 IP options require packet mangling. 275 But it is the easiest for now, especially taking 276 into account that combination of IP options 277 and running sniffer is extremely rare condition. 278 --ANK (980813) 279 */ 280 if (skb_cow(skb, skb_headroom(skb))) { 281 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 282 goto drop; 283 } 284 285 iph = ip_hdr(skb); 286 287 if (ip_options_compile(NULL, skb)) { 288 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 289 goto drop; 290 } 291 292 opt = &(IPCB(skb)->opt); 293 if (unlikely(opt->srr)) { 294 struct in_device *in_dev = in_dev_get(dev); 295 if (in_dev) { 296 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 297 if (IN_DEV_LOG_MARTIANS(in_dev) && 298 net_ratelimit()) 299 printk(KERN_INFO "source route option " 300 "%u.%u.%u.%u -> %u.%u.%u.%u\n", 301 NIPQUAD(iph->saddr), 302 NIPQUAD(iph->daddr)); 303 in_dev_put(in_dev); 304 goto drop; 305 } 306 307 in_dev_put(in_dev); 308 } 309 310 if (ip_options_rcv_srr(skb)) 311 goto drop; 312 } 313 314 return 0; 315 drop: 316 return -1; 317 } 318 319 static int ip_rcv_finish(struct sk_buff *skb) 320 { 321 const struct iphdr *iph = ip_hdr(skb); 322 struct rtable *rt; 323 324 /* 325 * Initialise the virtual path cache for the packet. It describes 326 * how the packet travels inside Linux networking. 327 */ 328 if (skb->dst == NULL) { 329 int err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, 330 skb->dev); 331 if (unlikely(err)) { 332 if (err == -EHOSTUNREACH) 333 IP_INC_STATS_BH(IPSTATS_MIB_INADDRERRORS); 334 else if (err == -ENETUNREACH) 335 IP_INC_STATS_BH(IPSTATS_MIB_INNOROUTES); 336 goto drop; 337 } 338 } 339 340 #ifdef CONFIG_NET_CLS_ROUTE 341 if (unlikely(skb->dst->tclassid)) { 342 struct ip_rt_acct *st = per_cpu_ptr(ip_rt_acct, smp_processor_id()); 343 u32 idx = skb->dst->tclassid; 344 st[idx&0xFF].o_packets++; 345 st[idx&0xFF].o_bytes+=skb->len; 346 st[(idx>>16)&0xFF].i_packets++; 347 st[(idx>>16)&0xFF].i_bytes+=skb->len; 348 } 349 #endif 350 351 if (iph->ihl > 5 && ip_rcv_options(skb)) 352 goto drop; 353 354 rt = (struct rtable*)skb->dst; 355 if (rt->rt_type == RTN_MULTICAST) 356 IP_INC_STATS_BH(IPSTATS_MIB_INMCASTPKTS); 357 else if (rt->rt_type == RTN_BROADCAST) 358 IP_INC_STATS_BH(IPSTATS_MIB_INBCASTPKTS); 359 360 return dst_input(skb); 361 362 drop: 363 kfree_skb(skb); 364 return NET_RX_DROP; 365 } 366 367 /* 368 * Main IP Receive routine. 369 */ 370 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 371 { 372 struct iphdr *iph; 373 u32 len; 374 375 if (dev->nd_net != &init_net) 376 goto drop; 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 = ip_hdr(skb); 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 = ip_hdr(skb); 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) { 420 IP_INC_STATS_BH(IPSTATS_MIB_INTRUNCATEDPKTS); 421 goto drop; 422 } else if (len < (iph->ihl*4)) 423 goto inhdr_error; 424 425 /* Our transport medium may have padded the buffer out. Now we know it 426 * is IP we can trim to the true length of the frame. 427 * Note this now means skb->len holds ntohs(iph->tot_len). 428 */ 429 if (pskb_trim_rcsum(skb, len)) { 430 IP_INC_STATS_BH(IPSTATS_MIB_INDISCARDS); 431 goto drop; 432 } 433 434 /* Remove any debris in the socket control block */ 435 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 436 437 return NF_HOOK(PF_INET, NF_INET_PRE_ROUTING, skb, dev, NULL, 438 ip_rcv_finish); 439 440 inhdr_error: 441 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); 442 drop: 443 kfree_skb(skb); 444 out: 445 return NET_RX_DROP; 446 } 447 448 EXPORT_SYMBOL(ip_statistics); 449