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, <bir7@leland.Stanford.Edu> 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 153DEFINE_SNMP_STAT(struct ip_mib, ip_statistics); 154 155/* 156 * Process Router Attention IP option 157 */ 158int 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); 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 199static inline int ip_local_deliver_finish(struct sk_buff *skb) 200{ 201 int ihl = skb->nh.iph->ihl*4; 202 203#ifdef CONFIG_NETFILTER_DEBUG 204 nf_debug_ip_local_deliver(skb); 205 skb->nf_debug = 0; 206#endif /*CONFIG_NETFILTER_DEBUG*/ 207 208 __skb_pull(skb, ihl); 209 210#ifdef CONFIG_NETFILTER 211 /* Free reference early: we don't need it any more, and it may 212 hold ip_conntrack module loaded indefinitely. */ 213 nf_conntrack_put(skb->nfct); 214 skb->nfct = NULL; 215#endif /*CONFIG_NETFILTER*/ 216 217 /* Point into the IP datagram, just past the header. */ 218 skb->h.raw = skb->data; 219 220 rcu_read_lock(); 221 { 222 /* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */ 223 int protocol = skb->nh.iph->protocol; 224 int hash; 225 struct sock *raw_sk; 226 struct inet_protocol *ipprot; 227 228 resubmit: 229 hash = protocol & (MAX_INET_PROTOS - 1); 230 raw_sk = sk_head(&raw_v4_htable[hash]); 231 232 /* If there maybe a raw socket we must check - if not we 233 * don't care less 234 */ 235 if (raw_sk) 236 raw_v4_input(skb, skb->nh.iph, hash); 237 238 if ((ipprot = inet_protos[hash]) != NULL) { 239 int ret; 240 241 smp_read_barrier_depends(); 242 if (!ipprot->no_policy && 243 !xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 244 kfree_skb(skb); 245 goto out; 246 } 247 ret = ipprot->handler(skb); 248 if (ret < 0) { 249 protocol = -ret; 250 goto resubmit; 251 } 252 IP_INC_STATS_BH(IpInDelivers); 253 } else { 254 if (!raw_sk) { 255 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 256 IP_INC_STATS_BH(IpInUnknownProtos); 257 icmp_send(skb, ICMP_DEST_UNREACH, 258 ICMP_PROT_UNREACH, 0); 259 } 260 } else 261 IP_INC_STATS_BH(IpInDelivers); 262 kfree_skb(skb); 263 } 264 } 265 out: 266 rcu_read_unlock(); 267 268 return 0; 269} 270 271/* 272 * Deliver IP Packets to the higher protocol layers. 273 */ 274int ip_local_deliver(struct sk_buff *skb) 275{ 276 /* 277 * Reassemble IP fragments. 278 */ 279 280 if (skb->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) { 281 skb = ip_defrag(skb); 282 if (!skb) 283 return 0; 284 } 285 286 return NF_HOOK(PF_INET, NF_IP_LOCAL_IN, skb, skb->dev, NULL, 287 ip_local_deliver_finish); 288} 289 290static inline int ip_rcv_finish(struct sk_buff *skb) 291{ 292 struct net_device *dev = skb->dev; 293 struct iphdr *iph = skb->nh.iph; 294 295 /* 296 * Initialise the virtual path cache for the packet. It describes 297 * how the packet travels inside Linux networking. 298 */ 299 if (skb->dst == NULL) { 300 if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev)) 301 goto drop; 302 } 303 304#ifdef CONFIG_NET_CLS_ROUTE 305 if (skb->dst->tclassid) { 306 struct ip_rt_acct *st = ip_rt_acct + 256*smp_processor_id(); 307 u32 idx = skb->dst->tclassid; 308 st[idx&0xFF].o_packets++; 309 st[idx&0xFF].o_bytes+=skb->len; 310 st[(idx>>16)&0xFF].i_packets++; 311 st[(idx>>16)&0xFF].i_bytes+=skb->len; 312 } 313#endif 314 315 if (iph->ihl > 5) { 316 struct ip_options *opt; 317 318 /* It looks as overkill, because not all 319 IP options require packet mangling. 320 But it is the easiest for now, especially taking 321 into account that combination of IP options 322 and running sniffer is extremely rare condition. 323 --ANK (980813) 324 */ 325 326 if (skb_cow(skb, skb_headroom(skb))) { 327 IP_INC_STATS_BH(IpInDiscards); 328 goto drop; 329 } 330 iph = skb->nh.iph; 331 332 if (ip_options_compile(NULL, skb)) 333 goto inhdr_error; 334 335 opt = &(IPCB(skb)->opt); 336 if (opt->srr) { 337 struct in_device *in_dev = in_dev_get(dev); 338 if (in_dev) { 339 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 340 if (IN_DEV_LOG_MARTIANS(in_dev) && net_ratelimit()) 341 printk(KERN_INFO "source route option %u.%u.%u.%u -> %u.%u.%u.%u\n", 342 NIPQUAD(iph->saddr), NIPQUAD(iph->daddr)); 343 in_dev_put(in_dev); 344 goto drop; 345 } 346 in_dev_put(in_dev); 347 } 348 if (ip_options_rcv_srr(skb)) 349 goto drop; 350 } 351 } 352 353 return dst_input(skb); 354 355inhdr_error: 356 IP_INC_STATS_BH(IpInHdrErrors); 357drop: 358 kfree_skb(skb); 359 return NET_RX_DROP; 360} 361 362/* 363 * Main IP Receive routine. 364 */ 365int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt) 366{ 367 struct iphdr *iph; 368 369 /* When the interface is in promisc. mode, drop all the crap 370 * that it receives, do not try to analyse it. 371 */ 372 if (skb->pkt_type == PACKET_OTHERHOST) 373 goto drop; 374 375 IP_INC_STATS_BH(IpInReceives); 376 377 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 378 IP_INC_STATS_BH(IpInDiscards); 379 goto out; 380 } 381 382 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 383 goto inhdr_error; 384 385 iph = skb->nh.iph; 386 387 /* 388 * RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum. 389 * 390 * Is the datagram acceptable? 391 * 392 * 1. Length at least the size of an ip header 393 * 2. Version of 4 394 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 395 * 4. Doesn't have a bogus length 396 */ 397 398 if (iph->ihl < 5 || iph->version != 4) 399 goto inhdr_error; 400 401 if (!pskb_may_pull(skb, iph->ihl*4)) 402 goto inhdr_error; 403 404 iph = skb->nh.iph; 405 406 if (ip_fast_csum((u8 *)iph, iph->ihl) != 0) 407 goto inhdr_error; 408 409 { 410 __u32 len = ntohs(iph->tot_len); 411 if (skb->len < len || len < (iph->ihl<<2)) 412 goto inhdr_error; 413 414 /* Our transport medium may have padded the buffer out. Now we know it 415 * is IP we can trim to the true length of the frame. 416 * Note this now means skb->len holds ntohs(iph->tot_len). 417 */ 418 if (skb->len > len) { 419 __pskb_trim(skb, len); 420 if (skb->ip_summed == CHECKSUM_HW) 421 skb->ip_summed = CHECKSUM_NONE; 422 } 423 } 424 425 return NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL, 426 ip_rcv_finish); 427 428inhdr_error: 429 IP_INC_STATS_BH(IpInHdrErrors); 430drop: 431 kfree_skb(skb); 432out: 433 return NET_RX_DROP; 434} 435 436EXPORT_SYMBOL(ip_rcv); 437EXPORT_SYMBOL(ip_statistics); 438