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 #include <linux/slab.h> 123 124 #include <linux/net.h> 125 #include <linux/socket.h> 126 #include <linux/sockios.h> 127 #include <linux/in.h> 128 #include <linux/inet.h> 129 #include <linux/inetdevice.h> 130 #include <linux/netdevice.h> 131 #include <linux/etherdevice.h> 132 133 #include <net/snmp.h> 134 #include <net/ip.h> 135 #include <net/protocol.h> 136 #include <net/route.h> 137 #include <linux/skbuff.h> 138 #include <net/sock.h> 139 #include <net/arp.h> 140 #include <net/icmp.h> 141 #include <net/raw.h> 142 #include <net/checksum.h> 143 #include <linux/netfilter_ipv4.h> 144 #include <net/xfrm.h> 145 #include <linux/mroute.h> 146 #include <linux/netlink.h> 147 148 /* 149 * Process Router Attention IP option 150 */ 151 int ip_call_ra_chain(struct sk_buff *skb) 152 { 153 struct ip_ra_chain *ra; 154 u8 protocol = ip_hdr(skb)->protocol; 155 struct sock *last = NULL; 156 struct net_device *dev = skb->dev; 157 158 read_lock(&ip_ra_lock); 159 for (ra = ip_ra_chain; ra; ra = ra->next) { 160 struct sock *sk = ra->sk; 161 162 /* If socket is bound to an interface, only report 163 * the packet if it came from that interface. 164 */ 165 if (sk && inet_sk(sk)->inet_num == protocol && 166 (!sk->sk_bound_dev_if || 167 sk->sk_bound_dev_if == dev->ifindex) && 168 net_eq(sock_net(sk), dev_net(dev))) { 169 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 170 if (ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN)) { 171 read_unlock(&ip_ra_lock); 172 return 1; 173 } 174 } 175 if (last) { 176 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); 177 if (skb2) 178 raw_rcv(last, skb2); 179 } 180 last = sk; 181 } 182 } 183 184 if (last) { 185 raw_rcv(last, skb); 186 read_unlock(&ip_ra_lock); 187 return 1; 188 } 189 read_unlock(&ip_ra_lock); 190 return 0; 191 } 192 193 static int ip_local_deliver_finish(struct sk_buff *skb) 194 { 195 struct net *net = dev_net(skb->dev); 196 197 __skb_pull(skb, ip_hdrlen(skb)); 198 199 /* Point into the IP datagram, just past the header. */ 200 skb_reset_transport_header(skb); 201 202 rcu_read_lock(); 203 { 204 int protocol = ip_hdr(skb)->protocol; 205 int hash, raw; 206 const struct net_protocol *ipprot; 207 208 resubmit: 209 raw = raw_local_deliver(skb, protocol); 210 211 hash = protocol & (MAX_INET_PROTOS - 1); 212 ipprot = rcu_dereference(inet_protos[hash]); 213 if (ipprot != NULL) { 214 int ret; 215 216 if (!net_eq(net, &init_net) && !ipprot->netns_ok) { 217 if (net_ratelimit()) 218 printk("%s: proto %d isn't netns-ready\n", 219 __func__, protocol); 220 kfree_skb(skb); 221 goto out; 222 } 223 224 if (!ipprot->no_policy) { 225 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 226 kfree_skb(skb); 227 goto out; 228 } 229 nf_reset(skb); 230 } 231 ret = ipprot->handler(skb); 232 if (ret < 0) { 233 protocol = -ret; 234 goto resubmit; 235 } 236 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 237 } else { 238 if (!raw) { 239 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 240 IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS); 241 icmp_send(skb, ICMP_DEST_UNREACH, 242 ICMP_PROT_UNREACH, 0); 243 } 244 } else 245 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 246 kfree_skb(skb); 247 } 248 } 249 out: 250 rcu_read_unlock(); 251 252 return 0; 253 } 254 255 /* 256 * Deliver IP Packets to the higher protocol layers. 257 */ 258 int ip_local_deliver(struct sk_buff *skb) 259 { 260 /* 261 * Reassemble IP fragments. 262 */ 263 264 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 265 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER)) 266 return 0; 267 } 268 269 return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, skb, skb->dev, NULL, 270 ip_local_deliver_finish); 271 } 272 273 static inline int ip_rcv_options(struct sk_buff *skb) 274 { 275 struct ip_options *opt; 276 struct iphdr *iph; 277 struct net_device *dev = skb->dev; 278 279 /* It looks as overkill, because not all 280 IP options require packet mangling. 281 But it is the easiest for now, especially taking 282 into account that combination of IP options 283 and running sniffer is extremely rare condition. 284 --ANK (980813) 285 */ 286 if (skb_cow(skb, skb_headroom(skb))) { 287 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 288 goto drop; 289 } 290 291 iph = ip_hdr(skb); 292 opt = &(IPCB(skb)->opt); 293 opt->optlen = iph->ihl*4 - sizeof(struct iphdr); 294 295 if (ip_options_compile(dev_net(dev), opt, skb)) { 296 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 297 goto drop; 298 } 299 300 if (unlikely(opt->srr)) { 301 struct in_device *in_dev = in_dev_get(dev); 302 if (in_dev) { 303 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 304 if (IN_DEV_LOG_MARTIANS(in_dev) && 305 net_ratelimit()) 306 printk(KERN_INFO "source route option %pI4 -> %pI4\n", 307 &iph->saddr, &iph->daddr); 308 in_dev_put(in_dev); 309 goto drop; 310 } 311 312 in_dev_put(in_dev); 313 } 314 315 if (ip_options_rcv_srr(skb)) 316 goto drop; 317 } 318 319 return 0; 320 drop: 321 return -1; 322 } 323 324 static int ip_rcv_finish(struct sk_buff *skb) 325 { 326 const struct iphdr *iph = ip_hdr(skb); 327 struct rtable *rt; 328 329 /* 330 * Initialise the virtual path cache for the packet. It describes 331 * how the packet travels inside Linux networking. 332 */ 333 if (skb_dst(skb) == NULL) { 334 int err = ip_route_input_noref(skb, iph->daddr, iph->saddr, 335 iph->tos, skb->dev); 336 if (unlikely(err)) { 337 if (err == -EHOSTUNREACH) 338 IP_INC_STATS_BH(dev_net(skb->dev), 339 IPSTATS_MIB_INADDRERRORS); 340 else if (err == -ENETUNREACH) 341 IP_INC_STATS_BH(dev_net(skb->dev), 342 IPSTATS_MIB_INNOROUTES); 343 goto drop; 344 } 345 } 346 347 #ifdef CONFIG_NET_CLS_ROUTE 348 if (unlikely(skb_dst(skb)->tclassid)) { 349 struct ip_rt_acct *st = per_cpu_ptr(ip_rt_acct, smp_processor_id()); 350 u32 idx = skb_dst(skb)->tclassid; 351 st[idx&0xFF].o_packets++; 352 st[idx&0xFF].o_bytes += skb->len; 353 st[(idx>>16)&0xFF].i_packets++; 354 st[(idx>>16)&0xFF].i_bytes += skb->len; 355 } 356 #endif 357 358 if (iph->ihl > 5 && ip_rcv_options(skb)) 359 goto drop; 360 361 rt = skb_rtable(skb); 362 if (rt->rt_type == RTN_MULTICAST) { 363 IP_UPD_PO_STATS_BH(dev_net(rt->u.dst.dev), IPSTATS_MIB_INMCAST, 364 skb->len); 365 } else if (rt->rt_type == RTN_BROADCAST) 366 IP_UPD_PO_STATS_BH(dev_net(rt->u.dst.dev), IPSTATS_MIB_INBCAST, 367 skb->len); 368 369 return dst_input(skb); 370 371 drop: 372 kfree_skb(skb); 373 return NET_RX_DROP; 374 } 375 376 /* 377 * Main IP Receive routine. 378 */ 379 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 380 { 381 struct iphdr *iph; 382 u32 len; 383 384 /* When the interface is in promisc. mode, drop all the crap 385 * that it receives, do not try to analyse it. 386 */ 387 if (skb->pkt_type == PACKET_OTHERHOST) 388 goto drop; 389 390 391 IP_UPD_PO_STATS_BH(dev_net(dev), IPSTATS_MIB_IN, skb->len); 392 393 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 394 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 395 goto out; 396 } 397 398 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 399 goto inhdr_error; 400 401 iph = ip_hdr(skb); 402 403 /* 404 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum. 405 * 406 * Is the datagram acceptable? 407 * 408 * 1. Length at least the size of an ip header 409 * 2. Version of 4 410 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 411 * 4. Doesn't have a bogus length 412 */ 413 414 if (iph->ihl < 5 || iph->version != 4) 415 goto inhdr_error; 416 417 if (!pskb_may_pull(skb, iph->ihl*4)) 418 goto inhdr_error; 419 420 iph = ip_hdr(skb); 421 422 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 423 goto inhdr_error; 424 425 len = ntohs(iph->tot_len); 426 if (skb->len < len) { 427 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS); 428 goto drop; 429 } else if (len < (iph->ihl*4)) 430 goto inhdr_error; 431 432 /* Our transport medium may have padded the buffer out. Now we know it 433 * is IP we can trim to the true length of the frame. 434 * Note this now means skb->len holds ntohs(iph->tot_len). 435 */ 436 if (pskb_trim_rcsum(skb, len)) { 437 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 438 goto drop; 439 } 440 441 /* Remove any debris in the socket control block */ 442 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 443 444 /* Must drop socket now because of tproxy. */ 445 skb_orphan(skb); 446 447 return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, dev, NULL, 448 ip_rcv_finish); 449 450 inhdr_error: 451 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 452 drop: 453 kfree_skb(skb); 454 out: 455 return NET_RX_DROP; 456 } 457