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 <net/inet_ecn.h> 145 #include <linux/netfilter_ipv4.h> 146 #include <net/xfrm.h> 147 #include <linux/mroute.h> 148 #include <linux/netlink.h> 149 150 /* 151 * Process Router Attention IP option (RFC 2113) 152 */ 153 bool ip_call_ra_chain(struct sk_buff *skb) 154 { 155 struct ip_ra_chain *ra; 156 u8 protocol = ip_hdr(skb)->protocol; 157 struct sock *last = NULL; 158 struct net_device *dev = skb->dev; 159 160 for (ra = rcu_dereference(ip_ra_chain); ra; ra = rcu_dereference(ra->next)) { 161 struct sock *sk = ra->sk; 162 163 /* If socket is bound to an interface, only report 164 * the packet if it came from that interface. 165 */ 166 if (sk && inet_sk(sk)->inet_num == protocol && 167 (!sk->sk_bound_dev_if || 168 sk->sk_bound_dev_if == dev->ifindex) && 169 net_eq(sock_net(sk), dev_net(dev))) { 170 if (ip_is_fragment(ip_hdr(skb))) { 171 if (ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN)) 172 return true; 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 return true; 186 } 187 return false; 188 } 189 190 static int ip_local_deliver_finish(struct sk_buff *skb) 191 { 192 struct net *net = dev_net(skb->dev); 193 194 __skb_pull(skb, skb_network_header_len(skb)); 195 196 rcu_read_lock(); 197 { 198 int protocol = ip_hdr(skb)->protocol; 199 const struct net_protocol *ipprot; 200 int raw; 201 202 resubmit: 203 raw = raw_local_deliver(skb, protocol); 204 205 ipprot = rcu_dereference(inet_protos[protocol]); 206 if (ipprot != NULL) { 207 int ret; 208 209 if (!ipprot->no_policy) { 210 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 211 kfree_skb(skb); 212 goto out; 213 } 214 nf_reset(skb); 215 } 216 ret = ipprot->handler(skb); 217 if (ret < 0) { 218 protocol = -ret; 219 goto resubmit; 220 } 221 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 222 } else { 223 if (!raw) { 224 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 225 IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS); 226 icmp_send(skb, ICMP_DEST_UNREACH, 227 ICMP_PROT_UNREACH, 0); 228 } 229 kfree_skb(skb); 230 } else { 231 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 232 consume_skb(skb); 233 } 234 } 235 } 236 out: 237 rcu_read_unlock(); 238 239 return 0; 240 } 241 242 /* 243 * Deliver IP Packets to the higher protocol layers. 244 */ 245 int ip_local_deliver(struct sk_buff *skb) 246 { 247 /* 248 * Reassemble IP fragments. 249 */ 250 251 if (ip_is_fragment(ip_hdr(skb))) { 252 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER)) 253 return 0; 254 } 255 256 return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, skb, skb->dev, NULL, 257 ip_local_deliver_finish); 258 } 259 260 static inline bool ip_rcv_options(struct sk_buff *skb) 261 { 262 struct ip_options *opt; 263 const struct iphdr *iph; 264 struct net_device *dev = skb->dev; 265 266 /* It looks as overkill, because not all 267 IP options require packet mangling. 268 But it is the easiest for now, especially taking 269 into account that combination of IP options 270 and running sniffer is extremely rare condition. 271 --ANK (980813) 272 */ 273 if (skb_cow(skb, skb_headroom(skb))) { 274 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 275 goto drop; 276 } 277 278 iph = ip_hdr(skb); 279 opt = &(IPCB(skb)->opt); 280 opt->optlen = iph->ihl*4 - sizeof(struct iphdr); 281 282 if (ip_options_compile(dev_net(dev), opt, skb)) { 283 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 284 goto drop; 285 } 286 287 if (unlikely(opt->srr)) { 288 struct in_device *in_dev = __in_dev_get_rcu(dev); 289 290 if (in_dev) { 291 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 292 if (IN_DEV_LOG_MARTIANS(in_dev)) 293 net_info_ratelimited("source route option %pI4 -> %pI4\n", 294 &iph->saddr, 295 &iph->daddr); 296 goto drop; 297 } 298 } 299 300 if (ip_options_rcv_srr(skb)) 301 goto drop; 302 } 303 304 return false; 305 drop: 306 return true; 307 } 308 309 int sysctl_ip_early_demux __read_mostly = 1; 310 EXPORT_SYMBOL(sysctl_ip_early_demux); 311 312 static int ip_rcv_finish(struct sk_buff *skb) 313 { 314 const struct iphdr *iph = ip_hdr(skb); 315 struct rtable *rt; 316 317 if (sysctl_ip_early_demux && !skb_dst(skb)) { 318 const struct net_protocol *ipprot; 319 int protocol = iph->protocol; 320 321 ipprot = rcu_dereference(inet_protos[protocol]); 322 if (ipprot && ipprot->early_demux) { 323 ipprot->early_demux(skb); 324 /* must reload iph, skb->head might have changed */ 325 iph = ip_hdr(skb); 326 } 327 } 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)) { 334 int err = ip_route_input_noref(skb, iph->daddr, iph->saddr, 335 iph->tos, skb->dev); 336 if (unlikely(err)) { 337 if (err == -EXDEV) 338 NET_INC_STATS_BH(dev_net(skb->dev), 339 LINUX_MIB_IPRPFILTER); 340 goto drop; 341 } 342 } 343 344 #ifdef CONFIG_IP_ROUTE_CLASSID 345 if (unlikely(skb_dst(skb)->tclassid)) { 346 struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct); 347 u32 idx = skb_dst(skb)->tclassid; 348 st[idx&0xFF].o_packets++; 349 st[idx&0xFF].o_bytes += skb->len; 350 st[(idx>>16)&0xFF].i_packets++; 351 st[(idx>>16)&0xFF].i_bytes += skb->len; 352 } 353 #endif 354 355 if (iph->ihl > 5 && ip_rcv_options(skb)) 356 goto drop; 357 358 rt = skb_rtable(skb); 359 if (rt->rt_type == RTN_MULTICAST) { 360 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INMCAST, 361 skb->len); 362 } else if (rt->rt_type == RTN_BROADCAST) 363 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INBCAST, 364 skb->len); 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 const 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; 386 387 388 IP_UPD_PO_STATS_BH(dev_net(dev), IPSTATS_MIB_IN, skb->len); 389 390 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 391 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 392 goto out; 393 } 394 395 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 396 goto inhdr_error; 397 398 iph = ip_hdr(skb); 399 400 /* 401 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum. 402 * 403 * Is the datagram acceptable? 404 * 405 * 1. Length at least the size of an ip header 406 * 2. Version of 4 407 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 408 * 4. Doesn't have a bogus length 409 */ 410 411 if (iph->ihl < 5 || iph->version != 4) 412 goto inhdr_error; 413 414 BUILD_BUG_ON(IPSTATS_MIB_ECT1PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_1); 415 BUILD_BUG_ON(IPSTATS_MIB_ECT0PKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_ECT_0); 416 BUILD_BUG_ON(IPSTATS_MIB_CEPKTS != IPSTATS_MIB_NOECTPKTS + INET_ECN_CE); 417 IP_ADD_STATS_BH(dev_net(dev), 418 IPSTATS_MIB_NOECTPKTS + (iph->tos & INET_ECN_MASK), 419 max_t(unsigned short, 1, skb_shinfo(skb)->gso_segs)); 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 csum_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 skb->transport_header = skb->network_header + iph->ihl*4; 446 447 /* Remove any debris in the socket control block */ 448 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 449 450 /* Must drop socket now because of tproxy. */ 451 skb_orphan(skb); 452 453 return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, dev, NULL, 454 ip_rcv_finish); 455 456 csum_error: 457 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_CSUMERRORS); 458 inhdr_error: 459 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 460 drop: 461 kfree_skb(skb); 462 out: 463 return NET_RX_DROP; 464 } 465