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@lxorguk.ukuu.org.uk> 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) { 213 int ret; 214 215 if (!net_eq(net, &init_net) && !ipprot->netns_ok) { 216 if (net_ratelimit()) 217 printk("%s: proto %d isn't netns-ready\n", 218 __func__, protocol); 219 kfree_skb(skb); 220 goto out; 221 } 222 223 if (!ipprot->no_policy) { 224 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 225 kfree_skb(skb); 226 goto out; 227 } 228 nf_reset(skb); 229 } 230 ret = ipprot->handler(skb); 231 if (ret < 0) { 232 protocol = -ret; 233 goto resubmit; 234 } 235 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 236 } else { 237 if (!raw) { 238 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 239 IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS); 240 icmp_send(skb, ICMP_DEST_UNREACH, 241 ICMP_PROT_UNREACH, 0); 242 } 243 } else 244 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 245 kfree_skb(skb); 246 } 247 } 248 out: 249 rcu_read_unlock(); 250 251 return 0; 252 } 253 254 /* 255 * Deliver IP Packets to the higher protocol layers. 256 */ 257 int ip_local_deliver(struct sk_buff *skb) 258 { 259 /* 260 * Reassemble IP fragments. 261 */ 262 263 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 264 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER)) 265 return 0; 266 } 267 268 return NF_HOOK(PF_INET, NF_INET_LOCAL_IN, skb, skb->dev, NULL, 269 ip_local_deliver_finish); 270 } 271 272 static inline int ip_rcv_options(struct sk_buff *skb) 273 { 274 struct ip_options *opt; 275 struct iphdr *iph; 276 struct net_device *dev = skb->dev; 277 278 /* It looks as overkill, because not all 279 IP options require packet mangling. 280 But it is the easiest for now, especially taking 281 into account that combination of IP options 282 and running sniffer is extremely rare condition. 283 --ANK (980813) 284 */ 285 if (skb_cow(skb, skb_headroom(skb))) { 286 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 287 goto drop; 288 } 289 290 iph = ip_hdr(skb); 291 opt = &(IPCB(skb)->opt); 292 opt->optlen = iph->ihl*4 - sizeof(struct iphdr); 293 294 if (ip_options_compile(dev_net(dev), opt, skb)) { 295 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 296 goto drop; 297 } 298 299 if (unlikely(opt->srr)) { 300 struct in_device *in_dev = in_dev_get(dev); 301 if (in_dev) { 302 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 303 if (IN_DEV_LOG_MARTIANS(in_dev) && 304 net_ratelimit()) 305 printk(KERN_INFO "source route option %pI4 -> %pI4\n", 306 &iph->saddr, &iph->daddr); 307 in_dev_put(in_dev); 308 goto drop; 309 } 310 311 in_dev_put(in_dev); 312 } 313 314 if (ip_options_rcv_srr(skb)) 315 goto drop; 316 } 317 318 return 0; 319 drop: 320 return -1; 321 } 322 323 static int ip_rcv_finish(struct sk_buff *skb) 324 { 325 const struct iphdr *iph = ip_hdr(skb); 326 struct rtable *rt; 327 328 /* 329 * Initialise the virtual path cache for the packet. It describes 330 * how the packet travels inside Linux networking. 331 */ 332 if (skb->dst == NULL) { 333 int err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, 334 skb->dev); 335 if (unlikely(err)) { 336 if (err == -EHOSTUNREACH) 337 IP_INC_STATS_BH(dev_net(skb->dev), 338 IPSTATS_MIB_INADDRERRORS); 339 else if (err == -ENETUNREACH) 340 IP_INC_STATS_BH(dev_net(skb->dev), 341 IPSTATS_MIB_INNOROUTES); 342 goto drop; 343 } 344 } 345 346 #ifdef CONFIG_NET_CLS_ROUTE 347 if (unlikely(skb->dst->tclassid)) { 348 struct ip_rt_acct *st = per_cpu_ptr(ip_rt_acct, smp_processor_id()); 349 u32 idx = skb->dst->tclassid; 350 st[idx&0xFF].o_packets++; 351 st[idx&0xFF].o_bytes += skb->len; 352 st[(idx>>16)&0xFF].i_packets++; 353 st[(idx>>16)&0xFF].i_bytes += skb->len; 354 } 355 #endif 356 357 if (iph->ihl > 5 && ip_rcv_options(skb)) 358 goto drop; 359 360 rt = skb->rtable; 361 if (rt->rt_type == RTN_MULTICAST) 362 IP_INC_STATS_BH(dev_net(rt->u.dst.dev), IPSTATS_MIB_INMCASTPKTS); 363 else if (rt->rt_type == RTN_BROADCAST) 364 IP_INC_STATS_BH(dev_net(rt->u.dst.dev), IPSTATS_MIB_INBCASTPKTS); 365 366 return dst_input(skb); 367 368 drop: 369 kfree_skb(skb); 370 return NET_RX_DROP; 371 } 372 373 /* 374 * Main IP Receive routine. 375 */ 376 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 377 { 378 struct iphdr *iph; 379 u32 len; 380 381 /* When the interface is in promisc. mode, drop all the crap 382 * that it receives, do not try to analyse it. 383 */ 384 if (skb->pkt_type == PACKET_OTHERHOST) 385 goto drop; 386 387 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INRECEIVES); 388 389 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 390 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 391 goto out; 392 } 393 394 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 395 goto inhdr_error; 396 397 iph = ip_hdr(skb); 398 399 /* 400 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum. 401 * 402 * Is the datagram acceptable? 403 * 404 * 1. Length at least the size of an ip header 405 * 2. Version of 4 406 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 407 * 4. Doesn't have a bogus length 408 */ 409 410 if (iph->ihl < 5 || iph->version != 4) 411 goto inhdr_error; 412 413 if (!pskb_may_pull(skb, iph->ihl*4)) 414 goto inhdr_error; 415 416 iph = ip_hdr(skb); 417 418 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 419 goto inhdr_error; 420 421 len = ntohs(iph->tot_len); 422 if (skb->len < len) { 423 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS); 424 goto drop; 425 } else if (len < (iph->ihl*4)) 426 goto inhdr_error; 427 428 /* Our transport medium may have padded the buffer out. Now we know it 429 * is IP we can trim to the true length of the frame. 430 * Note this now means skb->len holds ntohs(iph->tot_len). 431 */ 432 if (pskb_trim_rcsum(skb, len)) { 433 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 434 goto drop; 435 } 436 437 /* Remove any debris in the socket control block */ 438 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 439 440 return NF_HOOK(PF_INET, NF_INET_PRE_ROUTING, skb, dev, NULL, 441 ip_rcv_finish); 442 443 inhdr_error: 444 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 445 drop: 446 kfree_skb(skb); 447 out: 448 return NET_RX_DROP; 449 } 450