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 #define pr_fmt(fmt) "IPv4: " fmt 117 118 #include <linux/module.h> 119 #include <linux/types.h> 120 #include <linux/kernel.h> 121 #include <linux/string.h> 122 #include <linux/errno.h> 123 #include <linux/slab.h> 124 125 #include <linux/net.h> 126 #include <linux/socket.h> 127 #include <linux/sockios.h> 128 #include <linux/in.h> 129 #include <linux/inet.h> 130 #include <linux/inetdevice.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 * Process Router Attention IP option (RFC 2113) 151 */ 152 bool ip_call_ra_chain(struct sk_buff *skb) 153 { 154 struct ip_ra_chain *ra; 155 u8 protocol = ip_hdr(skb)->protocol; 156 struct sock *last = NULL; 157 struct net_device *dev = skb->dev; 158 159 for (ra = rcu_dereference(ip_ra_chain); ra; ra = rcu_dereference(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_is_fragment(ip_hdr(skb))) { 170 if (ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN)) 171 return true; 172 } 173 if (last) { 174 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); 175 if (skb2) 176 raw_rcv(last, skb2); 177 } 178 last = sk; 179 } 180 } 181 182 if (last) { 183 raw_rcv(last, skb); 184 return true; 185 } 186 return false; 187 } 188 189 static int ip_local_deliver_finish(struct sk_buff *skb) 190 { 191 struct net *net = dev_net(skb->dev); 192 193 __skb_pull(skb, ip_hdrlen(skb)); 194 195 /* Point into the IP datagram, just past the header. */ 196 skb_reset_transport_header(skb); 197 198 rcu_read_lock(); 199 { 200 int protocol = ip_hdr(skb)->protocol; 201 const struct net_protocol *ipprot; 202 int raw; 203 204 resubmit: 205 raw = raw_local_deliver(skb, protocol); 206 207 ipprot = rcu_dereference(inet_protos[protocol]); 208 if (ipprot != NULL) { 209 int ret; 210 211 if (!net_eq(net, &init_net) && !ipprot->netns_ok) { 212 net_info_ratelimited("%s: proto %d isn't netns-ready\n", 213 __func__, protocol); 214 kfree_skb(skb); 215 goto out; 216 } 217 218 if (!ipprot->no_policy) { 219 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 220 kfree_skb(skb); 221 goto out; 222 } 223 nf_reset(skb); 224 } 225 ret = ipprot->handler(skb); 226 if (ret < 0) { 227 protocol = -ret; 228 goto resubmit; 229 } 230 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 231 } else { 232 if (!raw) { 233 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 234 IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS); 235 icmp_send(skb, ICMP_DEST_UNREACH, 236 ICMP_PROT_UNREACH, 0); 237 } 238 } else 239 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 240 kfree_skb(skb); 241 } 242 } 243 out: 244 rcu_read_unlock(); 245 246 return 0; 247 } 248 249 /* 250 * Deliver IP Packets to the higher protocol layers. 251 */ 252 int ip_local_deliver(struct sk_buff *skb) 253 { 254 /* 255 * Reassemble IP fragments. 256 */ 257 258 if (ip_is_fragment(ip_hdr(skb))) { 259 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER)) 260 return 0; 261 } 262 263 return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, skb, skb->dev, NULL, 264 ip_local_deliver_finish); 265 } 266 267 static inline bool ip_rcv_options(struct sk_buff *skb) 268 { 269 struct ip_options *opt; 270 const struct iphdr *iph; 271 struct net_device *dev = skb->dev; 272 273 /* It looks as overkill, because not all 274 IP options require packet mangling. 275 But it is the easiest for now, especially taking 276 into account that combination of IP options 277 and running sniffer is extremely rare condition. 278 --ANK (980813) 279 */ 280 if (skb_cow(skb, skb_headroom(skb))) { 281 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 282 goto drop; 283 } 284 285 iph = ip_hdr(skb); 286 opt = &(IPCB(skb)->opt); 287 opt->optlen = iph->ihl*4 - sizeof(struct iphdr); 288 289 if (ip_options_compile(dev_net(dev), opt, skb)) { 290 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 291 goto drop; 292 } 293 294 if (unlikely(opt->srr)) { 295 struct in_device *in_dev = __in_dev_get_rcu(dev); 296 297 if (in_dev) { 298 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 299 if (IN_DEV_LOG_MARTIANS(in_dev)) 300 net_info_ratelimited("source route option %pI4 -> %pI4\n", 301 &iph->saddr, 302 &iph->daddr); 303 goto drop; 304 } 305 } 306 307 if (ip_options_rcv_srr(skb)) 308 goto drop; 309 } 310 311 return false; 312 drop: 313 return true; 314 } 315 316 int sysctl_ip_early_demux __read_mostly = 1; 317 EXPORT_SYMBOL(sysctl_ip_early_demux); 318 319 static int ip_rcv_finish(struct sk_buff *skb) 320 { 321 const struct iphdr *iph = ip_hdr(skb); 322 struct rtable *rt; 323 324 if (sysctl_ip_early_demux && !skb_dst(skb)) { 325 const struct net_protocol *ipprot; 326 int protocol = iph->protocol; 327 328 ipprot = rcu_dereference(inet_protos[protocol]); 329 if (ipprot && ipprot->early_demux) { 330 ipprot->early_demux(skb); 331 /* must reload iph, skb->head might have changed */ 332 iph = ip_hdr(skb); 333 } 334 } 335 336 /* 337 * Initialise the virtual path cache for the packet. It describes 338 * how the packet travels inside Linux networking. 339 */ 340 if (!skb_dst(skb)) { 341 int err = ip_route_input_noref(skb, iph->daddr, iph->saddr, 342 iph->tos, skb->dev); 343 if (unlikely(err)) { 344 if (err == -EXDEV) 345 NET_INC_STATS_BH(dev_net(skb->dev), 346 LINUX_MIB_IPRPFILTER); 347 goto drop; 348 } 349 } 350 351 #ifdef CONFIG_IP_ROUTE_CLASSID 352 if (unlikely(skb_dst(skb)->tclassid)) { 353 struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct); 354 u32 idx = skb_dst(skb)->tclassid; 355 st[idx&0xFF].o_packets++; 356 st[idx&0xFF].o_bytes += skb->len; 357 st[(idx>>16)&0xFF].i_packets++; 358 st[(idx>>16)&0xFF].i_bytes += skb->len; 359 } 360 #endif 361 362 if (iph->ihl > 5 && ip_rcv_options(skb)) 363 goto drop; 364 365 rt = skb_rtable(skb); 366 if (rt->rt_type == RTN_MULTICAST) { 367 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INMCAST, 368 skb->len); 369 } else if (rt->rt_type == RTN_BROADCAST) 370 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INBCAST, 371 skb->len); 372 373 return dst_input(skb); 374 375 drop: 376 kfree_skb(skb); 377 return NET_RX_DROP; 378 } 379 380 /* 381 * Main IP Receive routine. 382 */ 383 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 384 { 385 const struct iphdr *iph; 386 u32 len; 387 388 /* When the interface is in promisc. mode, drop all the crap 389 * that it receives, do not try to analyse it. 390 */ 391 if (skb->pkt_type == PACKET_OTHERHOST) 392 goto drop; 393 394 395 IP_UPD_PO_STATS_BH(dev_net(dev), IPSTATS_MIB_IN, skb->len); 396 397 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 398 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 399 goto out; 400 } 401 402 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 403 goto inhdr_error; 404 405 iph = ip_hdr(skb); 406 407 /* 408 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum. 409 * 410 * Is the datagram acceptable? 411 * 412 * 1. Length at least the size of an ip header 413 * 2. Version of 4 414 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 415 * 4. Doesn't have a bogus length 416 */ 417 418 if (iph->ihl < 5 || iph->version != 4) 419 goto inhdr_error; 420 421 if (!pskb_may_pull(skb, iph->ihl*4)) 422 goto inhdr_error; 423 424 iph = ip_hdr(skb); 425 426 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 427 goto inhdr_error; 428 429 len = ntohs(iph->tot_len); 430 if (skb->len < len) { 431 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS); 432 goto drop; 433 } else if (len < (iph->ihl*4)) 434 goto inhdr_error; 435 436 /* Our transport medium may have padded the buffer out. Now we know it 437 * is IP we can trim to the true length of the frame. 438 * Note this now means skb->len holds ntohs(iph->tot_len). 439 */ 440 if (pskb_trim_rcsum(skb, len)) { 441 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 442 goto drop; 443 } 444 445 /* Remove any debris in the socket control block */ 446 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 447 448 /* Must drop socket now because of tproxy. */ 449 skb_orphan(skb); 450 451 return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, dev, NULL, 452 ip_rcv_finish); 453 454 inhdr_error: 455 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 456 drop: 457 kfree_skb(skb); 458 out: 459 return NET_RX_DROP; 460 } 461