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 * Authors: Ross Biro 9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 10 * Donald Becker, <becker@super.org> 11 * Alan Cox, <Alan.Cox@linux.org> 12 * Richard Underwood 13 * Stefan Becker, <stefanb@yello.ping.de> 14 * Jorge Cwik, <jorge@laser.satlink.net> 15 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 16 * 17 * 18 * Fixes: 19 * Alan Cox : Commented a couple of minor bits of surplus code 20 * Alan Cox : Undefining IP_FORWARD doesn't include the code 21 * (just stops a compiler warning). 22 * Alan Cox : Frames with >=MAX_ROUTE record routes, strict routes or loose routes 23 * are junked rather than corrupting things. 24 * Alan Cox : Frames to bad broadcast subnets are dumped 25 * We used to process them non broadcast and 26 * boy could that cause havoc. 27 * Alan Cox : ip_forward sets the free flag on the 28 * new frame it queues. Still crap because 29 * it copies the frame but at least it 30 * doesn't eat memory too. 31 * Alan Cox : Generic queue code and memory fixes. 32 * Fred Van Kempen : IP fragment support (borrowed from NET2E) 33 * Gerhard Koerting: Forward fragmented frames correctly. 34 * Gerhard Koerting: Fixes to my fix of the above 8-). 35 * Gerhard Koerting: IP interface addressing fix. 36 * Linus Torvalds : More robustness checks 37 * Alan Cox : Even more checks: Still not as robust as it ought to be 38 * Alan Cox : Save IP header pointer for later 39 * Alan Cox : ip option setting 40 * Alan Cox : Use ip_tos/ip_ttl settings 41 * Alan Cox : Fragmentation bogosity removed 42 * (Thanks to Mark.Bush@prg.ox.ac.uk) 43 * Dmitry Gorodchanin : Send of a raw packet crash fix. 44 * Alan Cox : Silly ip bug when an overlength 45 * fragment turns up. Now frees the 46 * queue. 47 * Linus Torvalds/ : Memory leakage on fragmentation 48 * Alan Cox : handling. 49 * Gerhard Koerting: Forwarding uses IP priority hints 50 * Teemu Rantanen : Fragment problems. 51 * Alan Cox : General cleanup, comments and reformat 52 * Alan Cox : SNMP statistics 53 * Alan Cox : BSD address rule semantics. Also see 54 * UDP as there is a nasty checksum issue 55 * if you do things the wrong way. 56 * Alan Cox : Always defrag, moved IP_FORWARD to the config.in file 57 * Alan Cox : IP options adjust sk->priority. 58 * Pedro Roque : Fix mtu/length error in ip_forward. 59 * Alan Cox : Avoid ip_chk_addr when possible. 60 * Richard Underwood : IP multicasting. 61 * Alan Cox : Cleaned up multicast handlers. 62 * Alan Cox : RAW sockets demultiplex in the BSD style. 63 * Gunther Mayer : Fix the SNMP reporting typo 64 * Alan Cox : Always in group 224.0.0.1 65 * Pauline Middelink : Fast ip_checksum update when forwarding 66 * Masquerading support. 67 * Alan Cox : Multicast loopback error for 224.0.0.1 68 * Alan Cox : IP_MULTICAST_LOOP option. 69 * Alan Cox : Use notifiers. 70 * Bjorn Ekwall : Removed ip_csum (from slhc.c too) 71 * Bjorn Ekwall : Moved ip_fast_csum to ip.h (inline!) 72 * Stefan Becker : Send out ICMP HOST REDIRECT 73 * Arnt Gulbrandsen : ip_build_xmit 74 * Alan Cox : Per socket routing cache 75 * Alan Cox : Fixed routing cache, added header cache. 76 * Alan Cox : Loopback didn't work right in original ip_build_xmit - fixed it. 77 * Alan Cox : Only send ICMP_REDIRECT if src/dest are the same net. 78 * Alan Cox : Incoming IP option handling. 79 * Alan Cox : Set saddr on raw output frames as per BSD. 80 * Alan Cox : Stopped broadcast source route explosions. 81 * Alan Cox : Can disable source routing 82 * Takeshi Sone : Masquerading didn't work. 83 * Dave Bonn,Alan Cox : Faster IP forwarding whenever possible. 84 * Alan Cox : Memory leaks, tramples, misc debugging. 85 * Alan Cox : Fixed multicast (by popular demand 8)) 86 * Alan Cox : Fixed forwarding (by even more popular demand 8)) 87 * Alan Cox : Fixed SNMP statistics [I think] 88 * Gerhard Koerting : IP fragmentation forwarding fix 89 * Alan Cox : Device lock against page fault. 90 * Alan Cox : IP_HDRINCL facility. 91 * Werner Almesberger : Zero fragment bug 92 * Alan Cox : RAW IP frame length bug 93 * Alan Cox : Outgoing firewall on build_xmit 94 * A.N.Kuznetsov : IP_OPTIONS support throughout the kernel 95 * Alan Cox : Multicast routing hooks 96 * Jos Vos : Do accounting *before* call_in_firewall 97 * Willy Konynenberg : Transparent proxying support 98 * 99 * 100 * 101 * To Fix: 102 * IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient 103 * and could be made very efficient with the addition of some virtual memory hacks to permit 104 * the allocation of a buffer that can then be 'grown' by twiddling page tables. 105 * Output fragmentation wants updating along with the buffer management to use a single 106 * interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet 107 * output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause 108 * fragmentation anyway. 109 * 110 * This program is free software; you can redistribute it and/or 111 * modify it under the terms of the GNU General Public License 112 * as published by the Free Software Foundation; either version 113 * 2 of the License, or (at your option) any later version. 114 */ 115 116 #include <asm/system.h> 117 #include <linux/module.h> 118 #include <linux/types.h> 119 #include <linux/kernel.h> 120 #include <linux/string.h> 121 #include <linux/errno.h> 122 123 #include <linux/net.h> 124 #include <linux/socket.h> 125 #include <linux/sockios.h> 126 #include <linux/in.h> 127 #include <linux/inet.h> 128 #include <linux/inetdevice.h> 129 #include <linux/netdevice.h> 130 #include <linux/etherdevice.h> 131 132 #include <net/snmp.h> 133 #include <net/ip.h> 134 #include <net/protocol.h> 135 #include <net/route.h> 136 #include <linux/skbuff.h> 137 #include <net/sock.h> 138 #include <net/arp.h> 139 #include <net/icmp.h> 140 #include <net/raw.h> 141 #include <net/checksum.h> 142 #include <linux/netfilter_ipv4.h> 143 #include <net/xfrm.h> 144 #include <linux/mroute.h> 145 #include <linux/netlink.h> 146 147 /* 148 * Process Router Attention IP option 149 */ 150 int ip_call_ra_chain(struct sk_buff *skb) 151 { 152 struct ip_ra_chain *ra; 153 u8 protocol = ip_hdr(skb)->protocol; 154 struct sock *last = NULL; 155 struct net_device *dev = skb->dev; 156 157 read_lock(&ip_ra_lock); 158 for (ra = ip_ra_chain; ra; ra = ra->next) { 159 struct sock *sk = ra->sk; 160 161 /* If socket is bound to an interface, only report 162 * the packet if it came from that interface. 163 */ 164 if (sk && inet_sk(sk)->num == protocol && 165 (!sk->sk_bound_dev_if || 166 sk->sk_bound_dev_if == dev->ifindex) && 167 sock_net(sk) == dev_net(dev)) { 168 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 169 if (ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN)) { 170 read_unlock(&ip_ra_lock); 171 return 1; 172 } 173 } 174 if (last) { 175 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); 176 if (skb2) 177 raw_rcv(last, skb2); 178 } 179 last = sk; 180 } 181 } 182 183 if (last) { 184 raw_rcv(last, skb); 185 read_unlock(&ip_ra_lock); 186 return 1; 187 } 188 read_unlock(&ip_ra_lock); 189 return 0; 190 } 191 192 static int ip_local_deliver_finish(struct sk_buff *skb) 193 { 194 struct net *net = dev_net(skb->dev); 195 196 __skb_pull(skb, ip_hdrlen(skb)); 197 198 /* Point into the IP datagram, just past the header. */ 199 skb_reset_transport_header(skb); 200 201 rcu_read_lock(); 202 { 203 int protocol = ip_hdr(skb)->protocol; 204 int hash, raw; 205 struct net_protocol *ipprot; 206 207 resubmit: 208 raw = raw_local_deliver(skb, protocol); 209 210 hash = protocol & (MAX_INET_PROTOS - 1); 211 ipprot = rcu_dereference(inet_protos[hash]); 212 if (ipprot != NULL && (net == &init_net || ipprot->netns_ok)) { 213 int ret; 214 215 if (!ipprot->no_policy) { 216 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 217 kfree_skb(skb); 218 goto out; 219 } 220 nf_reset(skb); 221 } 222 ret = ipprot->handler(skb); 223 if (ret < 0) { 224 protocol = -ret; 225 goto resubmit; 226 } 227 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 228 } else { 229 if (!raw) { 230 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 231 IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS); 232 icmp_send(skb, ICMP_DEST_UNREACH, 233 ICMP_PROT_UNREACH, 0); 234 } 235 } else 236 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 237 kfree_skb(skb); 238 } 239 } 240 out: 241 rcu_read_unlock(); 242 243 return 0; 244 } 245 246 /* 247 * Deliver IP Packets to the higher protocol layers. 248 */ 249 int ip_local_deliver(struct sk_buff *skb) 250 { 251 /* 252 * Reassemble IP fragments. 253 */ 254 255 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 256 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER)) 257 return 0; 258 } 259 260 return NF_HOOK(PF_INET, NF_INET_LOCAL_IN, skb, skb->dev, NULL, 261 ip_local_deliver_finish); 262 } 263 264 static inline int ip_rcv_options(struct sk_buff *skb) 265 { 266 struct ip_options *opt; 267 struct iphdr *iph; 268 struct net_device *dev = skb->dev; 269 270 /* It looks as overkill, because not all 271 IP options require packet mangling. 272 But it is the easiest for now, especially taking 273 into account that combination of IP options 274 and running sniffer is extremely rare condition. 275 --ANK (980813) 276 */ 277 if (skb_cow(skb, skb_headroom(skb))) { 278 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 279 goto drop; 280 } 281 282 iph = ip_hdr(skb); 283 opt = &(IPCB(skb)->opt); 284 opt->optlen = iph->ihl*4 - sizeof(struct iphdr); 285 286 if (ip_options_compile(dev_net(dev), opt, skb)) { 287 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 288 goto drop; 289 } 290 291 if (unlikely(opt->srr)) { 292 struct in_device *in_dev = in_dev_get(dev); 293 if (in_dev) { 294 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 295 if (IN_DEV_LOG_MARTIANS(in_dev) && 296 net_ratelimit()) 297 printk(KERN_INFO "source route option " 298 NIPQUAD_FMT " -> " NIPQUAD_FMT "\n", 299 NIPQUAD(iph->saddr), 300 NIPQUAD(iph->daddr)); 301 in_dev_put(in_dev); 302 goto drop; 303 } 304 305 in_dev_put(in_dev); 306 } 307 308 if (ip_options_rcv_srr(skb)) 309 goto drop; 310 } 311 312 return 0; 313 drop: 314 return -1; 315 } 316 317 static int ip_rcv_finish(struct sk_buff *skb) 318 { 319 const struct iphdr *iph = ip_hdr(skb); 320 struct rtable *rt; 321 322 /* 323 * Initialise the virtual path cache for the packet. It describes 324 * how the packet travels inside Linux networking. 325 */ 326 if (skb->dst == NULL) { 327 int err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, 328 skb->dev); 329 if (unlikely(err)) { 330 if (err == -EHOSTUNREACH) 331 IP_INC_STATS_BH(dev_net(skb->dev), 332 IPSTATS_MIB_INADDRERRORS); 333 else if (err == -ENETUNREACH) 334 IP_INC_STATS_BH(dev_net(skb->dev), 335 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 = skb->rtable; 355 if (rt->rt_type == RTN_MULTICAST) 356 IP_INC_STATS_BH(dev_net(rt->u.dst.dev), IPSTATS_MIB_INMCASTPKTS); 357 else if (rt->rt_type == RTN_BROADCAST) 358 IP_INC_STATS_BH(dev_net(rt->u.dst.dev), 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 /* When the interface is in promisc. mode, drop all the crap 376 * that it receives, do not try to analyse it. 377 */ 378 if (skb->pkt_type == PACKET_OTHERHOST) 379 goto drop; 380 381 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INRECEIVES); 382 383 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 384 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 385 goto out; 386 } 387 388 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 389 goto inhdr_error; 390 391 iph = ip_hdr(skb); 392 393 /* 394 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum. 395 * 396 * Is the datagram acceptable? 397 * 398 * 1. Length at least the size of an ip header 399 * 2. Version of 4 400 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 401 * 4. Doesn't have a bogus length 402 */ 403 404 if (iph->ihl < 5 || iph->version != 4) 405 goto inhdr_error; 406 407 if (!pskb_may_pull(skb, iph->ihl*4)) 408 goto inhdr_error; 409 410 iph = ip_hdr(skb); 411 412 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 413 goto inhdr_error; 414 415 len = ntohs(iph->tot_len); 416 if (skb->len < len) { 417 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS); 418 goto drop; 419 } else if (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(dev_net(dev), IPSTATS_MIB_INDISCARDS); 428 goto drop; 429 } 430 431 /* Remove any debris in the socket control block */ 432 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 433 434 return NF_HOOK(PF_INET, NF_INET_PRE_ROUTING, skb, dev, NULL, 435 ip_rcv_finish); 436 437 inhdr_error: 438 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 439 drop: 440 kfree_skb(skb); 441 out: 442 return NET_RX_DROP; 443 } 444