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 (RFC 2113) 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 for (ra = rcu_dereference(ip_ra_chain); ra; ra = rcu_dereference(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)->inet_num == protocol && 165 (!sk->sk_bound_dev_if || 166 sk->sk_bound_dev_if == dev->ifindex) && 167 net_eq(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 return 1; 171 } 172 if (last) { 173 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); 174 if (skb2) 175 raw_rcv(last, skb2); 176 } 177 last = sk; 178 } 179 } 180 181 if (last) { 182 raw_rcv(last, skb); 183 return 1; 184 } 185 return 0; 186 } 187 188 static int ip_local_deliver_finish(struct sk_buff *skb) 189 { 190 struct net *net = dev_net(skb->dev); 191 192 __skb_pull(skb, ip_hdrlen(skb)); 193 194 /* Point into the IP datagram, just past the header. */ 195 skb_reset_transport_header(skb); 196 197 rcu_read_lock(); 198 { 199 int protocol = ip_hdr(skb)->protocol; 200 int hash, raw; 201 const struct net_protocol *ipprot; 202 203 resubmit: 204 raw = raw_local_deliver(skb, protocol); 205 206 hash = protocol & (MAX_INET_PROTOS - 1); 207 ipprot = rcu_dereference(inet_protos[hash]); 208 if (ipprot != NULL) { 209 int ret; 210 211 if (!net_eq(net, &init_net) && !ipprot->netns_ok) { 212 if (net_ratelimit()) 213 printk("%s: proto %d isn't netns-ready\n", 214 __func__, protocol); 215 kfree_skb(skb); 216 goto out; 217 } 218 219 if (!ipprot->no_policy) { 220 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 221 kfree_skb(skb); 222 goto out; 223 } 224 nf_reset(skb); 225 } 226 ret = ipprot->handler(skb); 227 if (ret < 0) { 228 protocol = -ret; 229 goto resubmit; 230 } 231 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 232 } else { 233 if (!raw) { 234 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 235 IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS); 236 icmp_send(skb, ICMP_DEST_UNREACH, 237 ICMP_PROT_UNREACH, 0); 238 } 239 } else 240 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 241 kfree_skb(skb); 242 } 243 } 244 out: 245 rcu_read_unlock(); 246 247 return 0; 248 } 249 250 /* 251 * Deliver IP Packets to the higher protocol layers. 252 */ 253 int ip_local_deliver(struct sk_buff *skb) 254 { 255 /* 256 * Reassemble IP fragments. 257 */ 258 259 if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) { 260 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER)) 261 return 0; 262 } 263 264 return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, skb, skb->dev, NULL, 265 ip_local_deliver_finish); 266 } 267 268 static inline int ip_rcv_options(struct sk_buff *skb) 269 { 270 struct ip_options *opt; 271 struct iphdr *iph; 272 struct net_device *dev = skb->dev; 273 274 /* It looks as overkill, because not all 275 IP options require packet mangling. 276 But it is the easiest for now, especially taking 277 into account that combination of IP options 278 and running sniffer is extremely rare condition. 279 --ANK (980813) 280 */ 281 if (skb_cow(skb, skb_headroom(skb))) { 282 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 283 goto drop; 284 } 285 286 iph = ip_hdr(skb); 287 opt = &(IPCB(skb)->opt); 288 opt->optlen = iph->ihl*4 - sizeof(struct iphdr); 289 290 if (ip_options_compile(dev_net(dev), opt, skb)) { 291 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 292 goto drop; 293 } 294 295 if (unlikely(opt->srr)) { 296 struct in_device *in_dev = __in_dev_get_rcu(dev); 297 298 if (in_dev) { 299 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 300 if (IN_DEV_LOG_MARTIANS(in_dev) && 301 net_ratelimit()) 302 printk(KERN_INFO "source route option %pI4 -> %pI4\n", 303 &iph->saddr, &iph->daddr); 304 goto drop; 305 } 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(skb) == NULL) { 327 int err = ip_route_input_noref(skb, iph->daddr, iph->saddr, 328 iph->tos, 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 else if (err == -EXDEV) 337 NET_INC_STATS_BH(dev_net(skb->dev), 338 LINUX_MIB_IPRPFILTER); 339 goto drop; 340 } 341 } 342 343 #ifdef CONFIG_IP_ROUTE_CLASSID 344 if (unlikely(skb_dst(skb)->tclassid)) { 345 struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct); 346 u32 idx = skb_dst(skb)->tclassid; 347 st[idx&0xFF].o_packets++; 348 st[idx&0xFF].o_bytes += skb->len; 349 st[(idx>>16)&0xFF].i_packets++; 350 st[(idx>>16)&0xFF].i_bytes += skb->len; 351 } 352 #endif 353 354 if (iph->ihl > 5 && ip_rcv_options(skb)) 355 goto drop; 356 357 rt = skb_rtable(skb); 358 if (rt->rt_type == RTN_MULTICAST) { 359 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INMCAST, 360 skb->len); 361 } else if (rt->rt_type == RTN_BROADCAST) 362 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INBCAST, 363 skb->len); 364 365 return dst_input(skb); 366 367 drop: 368 kfree_skb(skb); 369 return NET_RX_DROP; 370 } 371 372 /* 373 * Main IP Receive routine. 374 */ 375 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 376 { 377 struct iphdr *iph; 378 u32 len; 379 380 /* When the interface is in promisc. mode, drop all the crap 381 * that it receives, do not try to analyse it. 382 */ 383 if (skb->pkt_type == PACKET_OTHERHOST) 384 goto drop; 385 386 387 IP_UPD_PO_STATS_BH(dev_net(dev), IPSTATS_MIB_IN, skb->len); 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 /* Must drop socket now because of tproxy. */ 441 skb_orphan(skb); 442 443 return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, dev, NULL, 444 ip_rcv_finish); 445 446 inhdr_error: 447 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 448 drop: 449 kfree_skb(skb); 450 out: 451 return NET_RX_DROP; 452 } 453