1 /* 2 * Linux NET3: GRE over IP protocol decoder. 3 * 4 * Authors: Alexey Kuznetsov (kuznet@ms2.inr.ac.ru) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 * 11 */ 12 13 #include <linux/config.h> 14 #include <linux/module.h> 15 #include <linux/types.h> 16 #include <linux/sched.h> 17 #include <linux/kernel.h> 18 #include <asm/uaccess.h> 19 #include <linux/skbuff.h> 20 #include <linux/netdevice.h> 21 #include <linux/in.h> 22 #include <linux/tcp.h> 23 #include <linux/udp.h> 24 #include <linux/if_arp.h> 25 #include <linux/mroute.h> 26 #include <linux/init.h> 27 #include <linux/in6.h> 28 #include <linux/inetdevice.h> 29 #include <linux/igmp.h> 30 #include <linux/netfilter_ipv4.h> 31 #include <linux/if_ether.h> 32 33 #include <net/sock.h> 34 #include <net/ip.h> 35 #include <net/icmp.h> 36 #include <net/protocol.h> 37 #include <net/ipip.h> 38 #include <net/arp.h> 39 #include <net/checksum.h> 40 #include <net/dsfield.h> 41 #include <net/inet_ecn.h> 42 #include <net/xfrm.h> 43 44 #ifdef CONFIG_IPV6 45 #include <net/ipv6.h> 46 #include <net/ip6_fib.h> 47 #include <net/ip6_route.h> 48 #endif 49 50 /* 51 Problems & solutions 52 -------------------- 53 54 1. The most important issue is detecting local dead loops. 55 They would cause complete host lockup in transmit, which 56 would be "resolved" by stack overflow or, if queueing is enabled, 57 with infinite looping in net_bh. 58 59 We cannot track such dead loops during route installation, 60 it is infeasible task. The most general solutions would be 61 to keep skb->encapsulation counter (sort of local ttl), 62 and silently drop packet when it expires. It is the best 63 solution, but it supposes maintaing new variable in ALL 64 skb, even if no tunneling is used. 65 66 Current solution: t->recursion lock breaks dead loops. It looks 67 like dev->tbusy flag, but I preferred new variable, because 68 the semantics is different. One day, when hard_start_xmit 69 will be multithreaded we will have to use skb->encapsulation. 70 71 72 73 2. Networking dead loops would not kill routers, but would really 74 kill network. IP hop limit plays role of "t->recursion" in this case, 75 if we copy it from packet being encapsulated to upper header. 76 It is very good solution, but it introduces two problems: 77 78 - Routing protocols, using packets with ttl=1 (OSPF, RIP2), 79 do not work over tunnels. 80 - traceroute does not work. I planned to relay ICMP from tunnel, 81 so that this problem would be solved and traceroute output 82 would even more informative. This idea appeared to be wrong: 83 only Linux complies to rfc1812 now (yes, guys, Linux is the only 84 true router now :-)), all routers (at least, in neighbourhood of mine) 85 return only 8 bytes of payload. It is the end. 86 87 Hence, if we want that OSPF worked or traceroute said something reasonable, 88 we should search for another solution. 89 90 One of them is to parse packet trying to detect inner encapsulation 91 made by our node. It is difficult or even impossible, especially, 92 taking into account fragmentation. TO be short, tt is not solution at all. 93 94 Current solution: The solution was UNEXPECTEDLY SIMPLE. 95 We force DF flag on tunnels with preconfigured hop limit, 96 that is ALL. :-) Well, it does not remove the problem completely, 97 but exponential growth of network traffic is changed to linear 98 (branches, that exceed pmtu are pruned) and tunnel mtu 99 fastly degrades to value <68, where looping stops. 100 Yes, it is not good if there exists a router in the loop, 101 which does not force DF, even when encapsulating packets have DF set. 102 But it is not our problem! Nobody could accuse us, we made 103 all that we could make. Even if it is your gated who injected 104 fatal route to network, even if it were you who configured 105 fatal static route: you are innocent. :-) 106 107 108 109 3. Really, ipv4/ipip.c, ipv4/ip_gre.c and ipv6/sit.c contain 110 practically identical code. It would be good to glue them 111 together, but it is not very evident, how to make them modular. 112 sit is integral part of IPv6, ipip and gre are naturally modular. 113 We could extract common parts (hash table, ioctl etc) 114 to a separate module (ip_tunnel.c). 115 116 Alexey Kuznetsov. 117 */ 118 119 static int ipgre_tunnel_init(struct net_device *dev); 120 static void ipgre_tunnel_setup(struct net_device *dev); 121 122 /* Fallback tunnel: no source, no destination, no key, no options */ 123 124 static int ipgre_fb_tunnel_init(struct net_device *dev); 125 126 static struct net_device *ipgre_fb_tunnel_dev; 127 128 /* Tunnel hash table */ 129 130 /* 131 4 hash tables: 132 133 3: (remote,local) 134 2: (remote,*) 135 1: (*,local) 136 0: (*,*) 137 138 We require exact key match i.e. if a key is present in packet 139 it will match only tunnel with the same key; if it is not present, 140 it will match only keyless tunnel. 141 142 All keysless packets, if not matched configured keyless tunnels 143 will match fallback tunnel. 144 */ 145 146 #define HASH_SIZE 16 147 #define HASH(addr) ((addr^(addr>>4))&0xF) 148 149 static struct ip_tunnel *tunnels[4][HASH_SIZE]; 150 151 #define tunnels_r_l (tunnels[3]) 152 #define tunnels_r (tunnels[2]) 153 #define tunnels_l (tunnels[1]) 154 #define tunnels_wc (tunnels[0]) 155 156 static DEFINE_RWLOCK(ipgre_lock); 157 158 /* Given src, dst and key, find appropriate for input tunnel. */ 159 160 static struct ip_tunnel * ipgre_tunnel_lookup(u32 remote, u32 local, u32 key) 161 { 162 unsigned h0 = HASH(remote); 163 unsigned h1 = HASH(key); 164 struct ip_tunnel *t; 165 166 for (t = tunnels_r_l[h0^h1]; t; t = t->next) { 167 if (local == t->parms.iph.saddr && remote == t->parms.iph.daddr) { 168 if (t->parms.i_key == key && (t->dev->flags&IFF_UP)) 169 return t; 170 } 171 } 172 for (t = tunnels_r[h0^h1]; t; t = t->next) { 173 if (remote == t->parms.iph.daddr) { 174 if (t->parms.i_key == key && (t->dev->flags&IFF_UP)) 175 return t; 176 } 177 } 178 for (t = tunnels_l[h1]; t; t = t->next) { 179 if (local == t->parms.iph.saddr || 180 (local == t->parms.iph.daddr && MULTICAST(local))) { 181 if (t->parms.i_key == key && (t->dev->flags&IFF_UP)) 182 return t; 183 } 184 } 185 for (t = tunnels_wc[h1]; t; t = t->next) { 186 if (t->parms.i_key == key && (t->dev->flags&IFF_UP)) 187 return t; 188 } 189 190 if (ipgre_fb_tunnel_dev->flags&IFF_UP) 191 return netdev_priv(ipgre_fb_tunnel_dev); 192 return NULL; 193 } 194 195 static struct ip_tunnel **ipgre_bucket(struct ip_tunnel *t) 196 { 197 u32 remote = t->parms.iph.daddr; 198 u32 local = t->parms.iph.saddr; 199 u32 key = t->parms.i_key; 200 unsigned h = HASH(key); 201 int prio = 0; 202 203 if (local) 204 prio |= 1; 205 if (remote && !MULTICAST(remote)) { 206 prio |= 2; 207 h ^= HASH(remote); 208 } 209 210 return &tunnels[prio][h]; 211 } 212 213 static void ipgre_tunnel_link(struct ip_tunnel *t) 214 { 215 struct ip_tunnel **tp = ipgre_bucket(t); 216 217 t->next = *tp; 218 write_lock_bh(&ipgre_lock); 219 *tp = t; 220 write_unlock_bh(&ipgre_lock); 221 } 222 223 static void ipgre_tunnel_unlink(struct ip_tunnel *t) 224 { 225 struct ip_tunnel **tp; 226 227 for (tp = ipgre_bucket(t); *tp; tp = &(*tp)->next) { 228 if (t == *tp) { 229 write_lock_bh(&ipgre_lock); 230 *tp = t->next; 231 write_unlock_bh(&ipgre_lock); 232 break; 233 } 234 } 235 } 236 237 static struct ip_tunnel * ipgre_tunnel_locate(struct ip_tunnel_parm *parms, int create) 238 { 239 u32 remote = parms->iph.daddr; 240 u32 local = parms->iph.saddr; 241 u32 key = parms->i_key; 242 struct ip_tunnel *t, **tp, *nt; 243 struct net_device *dev; 244 unsigned h = HASH(key); 245 int prio = 0; 246 char name[IFNAMSIZ]; 247 248 if (local) 249 prio |= 1; 250 if (remote && !MULTICAST(remote)) { 251 prio |= 2; 252 h ^= HASH(remote); 253 } 254 for (tp = &tunnels[prio][h]; (t = *tp) != NULL; tp = &t->next) { 255 if (local == t->parms.iph.saddr && remote == t->parms.iph.daddr) { 256 if (key == t->parms.i_key) 257 return t; 258 } 259 } 260 if (!create) 261 return NULL; 262 263 if (parms->name[0]) 264 strlcpy(name, parms->name, IFNAMSIZ); 265 else { 266 int i; 267 for (i=1; i<100; i++) { 268 sprintf(name, "gre%d", i); 269 if (__dev_get_by_name(name) == NULL) 270 break; 271 } 272 if (i==100) 273 goto failed; 274 } 275 276 dev = alloc_netdev(sizeof(*t), name, ipgre_tunnel_setup); 277 if (!dev) 278 return NULL; 279 280 dev->init = ipgre_tunnel_init; 281 nt = netdev_priv(dev); 282 nt->parms = *parms; 283 284 if (register_netdevice(dev) < 0) { 285 free_netdev(dev); 286 goto failed; 287 } 288 289 dev_hold(dev); 290 ipgre_tunnel_link(nt); 291 return nt; 292 293 failed: 294 return NULL; 295 } 296 297 static void ipgre_tunnel_uninit(struct net_device *dev) 298 { 299 ipgre_tunnel_unlink(netdev_priv(dev)); 300 dev_put(dev); 301 } 302 303 304 static void ipgre_err(struct sk_buff *skb, u32 info) 305 { 306 #ifndef I_WISH_WORLD_WERE_PERFECT 307 308 /* It is not :-( All the routers (except for Linux) return only 309 8 bytes of packet payload. It means, that precise relaying of 310 ICMP in the real Internet is absolutely infeasible. 311 312 Moreover, Cisco "wise men" put GRE key to the third word 313 in GRE header. It makes impossible maintaining even soft state for keyed 314 GRE tunnels with enabled checksum. Tell them "thank you". 315 316 Well, I wonder, rfc1812 was written by Cisco employee, 317 what the hell these idiots break standrads established 318 by themself??? 319 */ 320 321 struct iphdr *iph = (struct iphdr*)skb->data; 322 u16 *p = (u16*)(skb->data+(iph->ihl<<2)); 323 int grehlen = (iph->ihl<<2) + 4; 324 int type = skb->h.icmph->type; 325 int code = skb->h.icmph->code; 326 struct ip_tunnel *t; 327 u16 flags; 328 329 flags = p[0]; 330 if (flags&(GRE_CSUM|GRE_KEY|GRE_SEQ|GRE_ROUTING|GRE_VERSION)) { 331 if (flags&(GRE_VERSION|GRE_ROUTING)) 332 return; 333 if (flags&GRE_KEY) { 334 grehlen += 4; 335 if (flags&GRE_CSUM) 336 grehlen += 4; 337 } 338 } 339 340 /* If only 8 bytes returned, keyed message will be dropped here */ 341 if (skb_headlen(skb) < grehlen) 342 return; 343 344 switch (type) { 345 default: 346 case ICMP_PARAMETERPROB: 347 return; 348 349 case ICMP_DEST_UNREACH: 350 switch (code) { 351 case ICMP_SR_FAILED: 352 case ICMP_PORT_UNREACH: 353 /* Impossible event. */ 354 return; 355 case ICMP_FRAG_NEEDED: 356 /* Soft state for pmtu is maintained by IP core. */ 357 return; 358 default: 359 /* All others are translated to HOST_UNREACH. 360 rfc2003 contains "deep thoughts" about NET_UNREACH, 361 I believe they are just ether pollution. --ANK 362 */ 363 break; 364 } 365 break; 366 case ICMP_TIME_EXCEEDED: 367 if (code != ICMP_EXC_TTL) 368 return; 369 break; 370 } 371 372 read_lock(&ipgre_lock); 373 t = ipgre_tunnel_lookup(iph->daddr, iph->saddr, (flags&GRE_KEY) ? *(((u32*)p) + (grehlen>>2) - 1) : 0); 374 if (t == NULL || t->parms.iph.daddr == 0 || MULTICAST(t->parms.iph.daddr)) 375 goto out; 376 377 if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED) 378 goto out; 379 380 if (jiffies - t->err_time < IPTUNNEL_ERR_TIMEO) 381 t->err_count++; 382 else 383 t->err_count = 1; 384 t->err_time = jiffies; 385 out: 386 read_unlock(&ipgre_lock); 387 return; 388 #else 389 struct iphdr *iph = (struct iphdr*)dp; 390 struct iphdr *eiph; 391 u16 *p = (u16*)(dp+(iph->ihl<<2)); 392 int type = skb->h.icmph->type; 393 int code = skb->h.icmph->code; 394 int rel_type = 0; 395 int rel_code = 0; 396 int rel_info = 0; 397 u16 flags; 398 int grehlen = (iph->ihl<<2) + 4; 399 struct sk_buff *skb2; 400 struct flowi fl; 401 struct rtable *rt; 402 403 if (p[1] != htons(ETH_P_IP)) 404 return; 405 406 flags = p[0]; 407 if (flags&(GRE_CSUM|GRE_KEY|GRE_SEQ|GRE_ROUTING|GRE_VERSION)) { 408 if (flags&(GRE_VERSION|GRE_ROUTING)) 409 return; 410 if (flags&GRE_CSUM) 411 grehlen += 4; 412 if (flags&GRE_KEY) 413 grehlen += 4; 414 if (flags&GRE_SEQ) 415 grehlen += 4; 416 } 417 if (len < grehlen + sizeof(struct iphdr)) 418 return; 419 eiph = (struct iphdr*)(dp + grehlen); 420 421 switch (type) { 422 default: 423 return; 424 case ICMP_PARAMETERPROB: 425 if (skb->h.icmph->un.gateway < (iph->ihl<<2)) 426 return; 427 428 /* So... This guy found something strange INSIDE encapsulated 429 packet. Well, he is fool, but what can we do ? 430 */ 431 rel_type = ICMP_PARAMETERPROB; 432 rel_info = skb->h.icmph->un.gateway - grehlen; 433 break; 434 435 case ICMP_DEST_UNREACH: 436 switch (code) { 437 case ICMP_SR_FAILED: 438 case ICMP_PORT_UNREACH: 439 /* Impossible event. */ 440 return; 441 case ICMP_FRAG_NEEDED: 442 /* And it is the only really necessary thing :-) */ 443 rel_info = ntohs(skb->h.icmph->un.frag.mtu); 444 if (rel_info < grehlen+68) 445 return; 446 rel_info -= grehlen; 447 /* BSD 4.2 MORE DOES NOT EXIST IN NATURE. */ 448 if (rel_info > ntohs(eiph->tot_len)) 449 return; 450 break; 451 default: 452 /* All others are translated to HOST_UNREACH. 453 rfc2003 contains "deep thoughts" about NET_UNREACH, 454 I believe, it is just ether pollution. --ANK 455 */ 456 rel_type = ICMP_DEST_UNREACH; 457 rel_code = ICMP_HOST_UNREACH; 458 break; 459 } 460 break; 461 case ICMP_TIME_EXCEEDED: 462 if (code != ICMP_EXC_TTL) 463 return; 464 break; 465 } 466 467 /* Prepare fake skb to feed it to icmp_send */ 468 skb2 = skb_clone(skb, GFP_ATOMIC); 469 if (skb2 == NULL) 470 return; 471 dst_release(skb2->dst); 472 skb2->dst = NULL; 473 skb_pull(skb2, skb->data - (u8*)eiph); 474 skb2->nh.raw = skb2->data; 475 476 /* Try to guess incoming interface */ 477 memset(&fl, 0, sizeof(fl)); 478 fl.fl4_dst = eiph->saddr; 479 fl.fl4_tos = RT_TOS(eiph->tos); 480 fl.proto = IPPROTO_GRE; 481 if (ip_route_output_key(&rt, &fl)) { 482 kfree_skb(skb2); 483 return; 484 } 485 skb2->dev = rt->u.dst.dev; 486 487 /* route "incoming" packet */ 488 if (rt->rt_flags&RTCF_LOCAL) { 489 ip_rt_put(rt); 490 rt = NULL; 491 fl.fl4_dst = eiph->daddr; 492 fl.fl4_src = eiph->saddr; 493 fl.fl4_tos = eiph->tos; 494 if (ip_route_output_key(&rt, &fl) || 495 rt->u.dst.dev->type != ARPHRD_IPGRE) { 496 ip_rt_put(rt); 497 kfree_skb(skb2); 498 return; 499 } 500 } else { 501 ip_rt_put(rt); 502 if (ip_route_input(skb2, eiph->daddr, eiph->saddr, eiph->tos, skb2->dev) || 503 skb2->dst->dev->type != ARPHRD_IPGRE) { 504 kfree_skb(skb2); 505 return; 506 } 507 } 508 509 /* change mtu on this route */ 510 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) { 511 if (rel_info > dst_mtu(skb2->dst)) { 512 kfree_skb(skb2); 513 return; 514 } 515 skb2->dst->ops->update_pmtu(skb2->dst, rel_info); 516 rel_info = htonl(rel_info); 517 } else if (type == ICMP_TIME_EXCEEDED) { 518 struct ip_tunnel *t = netdev_priv(skb2->dev); 519 if (t->parms.iph.ttl) { 520 rel_type = ICMP_DEST_UNREACH; 521 rel_code = ICMP_HOST_UNREACH; 522 } 523 } 524 525 icmp_send(skb2, rel_type, rel_code, rel_info); 526 kfree_skb(skb2); 527 #endif 528 } 529 530 static inline void ipgre_ecn_decapsulate(struct iphdr *iph, struct sk_buff *skb) 531 { 532 if (INET_ECN_is_ce(iph->tos)) { 533 if (skb->protocol == htons(ETH_P_IP)) { 534 IP_ECN_set_ce(skb->nh.iph); 535 } else if (skb->protocol == htons(ETH_P_IPV6)) { 536 IP6_ECN_set_ce(skb->nh.ipv6h); 537 } 538 } 539 } 540 541 static inline u8 542 ipgre_ecn_encapsulate(u8 tos, struct iphdr *old_iph, struct sk_buff *skb) 543 { 544 u8 inner = 0; 545 if (skb->protocol == htons(ETH_P_IP)) 546 inner = old_iph->tos; 547 else if (skb->protocol == htons(ETH_P_IPV6)) 548 inner = ipv6_get_dsfield((struct ipv6hdr *)old_iph); 549 return INET_ECN_encapsulate(tos, inner); 550 } 551 552 static int ipgre_rcv(struct sk_buff *skb) 553 { 554 struct iphdr *iph; 555 u8 *h; 556 u16 flags; 557 u16 csum = 0; 558 u32 key = 0; 559 u32 seqno = 0; 560 struct ip_tunnel *tunnel; 561 int offset = 4; 562 563 if (!pskb_may_pull(skb, 16)) 564 goto drop_nolock; 565 566 iph = skb->nh.iph; 567 h = skb->data; 568 flags = *(u16*)h; 569 570 if (flags&(GRE_CSUM|GRE_KEY|GRE_ROUTING|GRE_SEQ|GRE_VERSION)) { 571 /* - Version must be 0. 572 - We do not support routing headers. 573 */ 574 if (flags&(GRE_VERSION|GRE_ROUTING)) 575 goto drop_nolock; 576 577 if (flags&GRE_CSUM) { 578 switch (skb->ip_summed) { 579 case CHECKSUM_HW: 580 csum = (u16)csum_fold(skb->csum); 581 if (!csum) 582 break; 583 /* fall through */ 584 case CHECKSUM_NONE: 585 skb->csum = 0; 586 csum = __skb_checksum_complete(skb); 587 skb->ip_summed = CHECKSUM_HW; 588 } 589 offset += 4; 590 } 591 if (flags&GRE_KEY) { 592 key = *(u32*)(h + offset); 593 offset += 4; 594 } 595 if (flags&GRE_SEQ) { 596 seqno = ntohl(*(u32*)(h + offset)); 597 offset += 4; 598 } 599 } 600 601 read_lock(&ipgre_lock); 602 if ((tunnel = ipgre_tunnel_lookup(iph->saddr, iph->daddr, key)) != NULL) { 603 secpath_reset(skb); 604 605 skb->protocol = *(u16*)(h + 2); 606 /* WCCP version 1 and 2 protocol decoding. 607 * - Change protocol to IP 608 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header 609 */ 610 if (flags == 0 && 611 skb->protocol == __constant_htons(ETH_P_WCCP)) { 612 skb->protocol = __constant_htons(ETH_P_IP); 613 if ((*(h + offset) & 0xF0) != 0x40) 614 offset += 4; 615 } 616 617 skb->mac.raw = skb->nh.raw; 618 skb->nh.raw = __pskb_pull(skb, offset); 619 skb_postpull_rcsum(skb, skb->h.raw, offset); 620 memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options)); 621 skb->pkt_type = PACKET_HOST; 622 #ifdef CONFIG_NET_IPGRE_BROADCAST 623 if (MULTICAST(iph->daddr)) { 624 /* Looped back packet, drop it! */ 625 if (((struct rtable*)skb->dst)->fl.iif == 0) 626 goto drop; 627 tunnel->stat.multicast++; 628 skb->pkt_type = PACKET_BROADCAST; 629 } 630 #endif 631 632 if (((flags&GRE_CSUM) && csum) || 633 (!(flags&GRE_CSUM) && tunnel->parms.i_flags&GRE_CSUM)) { 634 tunnel->stat.rx_crc_errors++; 635 tunnel->stat.rx_errors++; 636 goto drop; 637 } 638 if (tunnel->parms.i_flags&GRE_SEQ) { 639 if (!(flags&GRE_SEQ) || 640 (tunnel->i_seqno && (s32)(seqno - tunnel->i_seqno) < 0)) { 641 tunnel->stat.rx_fifo_errors++; 642 tunnel->stat.rx_errors++; 643 goto drop; 644 } 645 tunnel->i_seqno = seqno + 1; 646 } 647 tunnel->stat.rx_packets++; 648 tunnel->stat.rx_bytes += skb->len; 649 skb->dev = tunnel->dev; 650 dst_release(skb->dst); 651 skb->dst = NULL; 652 nf_reset(skb); 653 ipgre_ecn_decapsulate(iph, skb); 654 netif_rx(skb); 655 read_unlock(&ipgre_lock); 656 return(0); 657 } 658 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PROT_UNREACH, 0); 659 660 drop: 661 read_unlock(&ipgre_lock); 662 drop_nolock: 663 kfree_skb(skb); 664 return(0); 665 } 666 667 static int ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev) 668 { 669 struct ip_tunnel *tunnel = netdev_priv(dev); 670 struct net_device_stats *stats = &tunnel->stat; 671 struct iphdr *old_iph = skb->nh.iph; 672 struct iphdr *tiph; 673 u8 tos; 674 u16 df; 675 struct rtable *rt; /* Route to the other host */ 676 struct net_device *tdev; /* Device to other host */ 677 struct iphdr *iph; /* Our new IP header */ 678 int max_headroom; /* The extra header space needed */ 679 int gre_hlen; 680 u32 dst; 681 int mtu; 682 683 if (tunnel->recursion++) { 684 tunnel->stat.collisions++; 685 goto tx_error; 686 } 687 688 if (dev->hard_header) { 689 gre_hlen = 0; 690 tiph = (struct iphdr*)skb->data; 691 } else { 692 gre_hlen = tunnel->hlen; 693 tiph = &tunnel->parms.iph; 694 } 695 696 if ((dst = tiph->daddr) == 0) { 697 /* NBMA tunnel */ 698 699 if (skb->dst == NULL) { 700 tunnel->stat.tx_fifo_errors++; 701 goto tx_error; 702 } 703 704 if (skb->protocol == htons(ETH_P_IP)) { 705 rt = (struct rtable*)skb->dst; 706 if ((dst = rt->rt_gateway) == 0) 707 goto tx_error_icmp; 708 } 709 #ifdef CONFIG_IPV6 710 else if (skb->protocol == htons(ETH_P_IPV6)) { 711 struct in6_addr *addr6; 712 int addr_type; 713 struct neighbour *neigh = skb->dst->neighbour; 714 715 if (neigh == NULL) 716 goto tx_error; 717 718 addr6 = (struct in6_addr*)&neigh->primary_key; 719 addr_type = ipv6_addr_type(addr6); 720 721 if (addr_type == IPV6_ADDR_ANY) { 722 addr6 = &skb->nh.ipv6h->daddr; 723 addr_type = ipv6_addr_type(addr6); 724 } 725 726 if ((addr_type & IPV6_ADDR_COMPATv4) == 0) 727 goto tx_error_icmp; 728 729 dst = addr6->s6_addr32[3]; 730 } 731 #endif 732 else 733 goto tx_error; 734 } 735 736 tos = tiph->tos; 737 if (tos&1) { 738 if (skb->protocol == htons(ETH_P_IP)) 739 tos = old_iph->tos; 740 tos &= ~1; 741 } 742 743 { 744 struct flowi fl = { .oif = tunnel->parms.link, 745 .nl_u = { .ip4_u = 746 { .daddr = dst, 747 .saddr = tiph->saddr, 748 .tos = RT_TOS(tos) } }, 749 .proto = IPPROTO_GRE }; 750 if (ip_route_output_key(&rt, &fl)) { 751 tunnel->stat.tx_carrier_errors++; 752 goto tx_error; 753 } 754 } 755 tdev = rt->u.dst.dev; 756 757 if (tdev == dev) { 758 ip_rt_put(rt); 759 tunnel->stat.collisions++; 760 goto tx_error; 761 } 762 763 df = tiph->frag_off; 764 if (df) 765 mtu = dst_mtu(&rt->u.dst) - tunnel->hlen; 766 else 767 mtu = skb->dst ? dst_mtu(skb->dst) : dev->mtu; 768 769 if (skb->dst) 770 skb->dst->ops->update_pmtu(skb->dst, mtu); 771 772 if (skb->protocol == htons(ETH_P_IP)) { 773 df |= (old_iph->frag_off&htons(IP_DF)); 774 775 if ((old_iph->frag_off&htons(IP_DF)) && 776 mtu < ntohs(old_iph->tot_len)) { 777 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu)); 778 ip_rt_put(rt); 779 goto tx_error; 780 } 781 } 782 #ifdef CONFIG_IPV6 783 else if (skb->protocol == htons(ETH_P_IPV6)) { 784 struct rt6_info *rt6 = (struct rt6_info*)skb->dst; 785 786 if (rt6 && mtu < dst_mtu(skb->dst) && mtu >= IPV6_MIN_MTU) { 787 if ((tunnel->parms.iph.daddr && !MULTICAST(tunnel->parms.iph.daddr)) || 788 rt6->rt6i_dst.plen == 128) { 789 rt6->rt6i_flags |= RTF_MODIFIED; 790 skb->dst->metrics[RTAX_MTU-1] = mtu; 791 } 792 } 793 794 if (mtu >= IPV6_MIN_MTU && mtu < skb->len - tunnel->hlen + gre_hlen) { 795 icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, dev); 796 ip_rt_put(rt); 797 goto tx_error; 798 } 799 } 800 #endif 801 802 if (tunnel->err_count > 0) { 803 if (jiffies - tunnel->err_time < IPTUNNEL_ERR_TIMEO) { 804 tunnel->err_count--; 805 806 dst_link_failure(skb); 807 } else 808 tunnel->err_count = 0; 809 } 810 811 max_headroom = LL_RESERVED_SPACE(tdev) + gre_hlen; 812 813 if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) { 814 struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom); 815 if (!new_skb) { 816 ip_rt_put(rt); 817 stats->tx_dropped++; 818 dev_kfree_skb(skb); 819 tunnel->recursion--; 820 return 0; 821 } 822 if (skb->sk) 823 skb_set_owner_w(new_skb, skb->sk); 824 dev_kfree_skb(skb); 825 skb = new_skb; 826 old_iph = skb->nh.iph; 827 } 828 829 skb->h.raw = skb->nh.raw; 830 skb->nh.raw = skb_push(skb, gre_hlen); 831 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt)); 832 IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE|IPSKB_XFRM_TRANSFORMED); 833 dst_release(skb->dst); 834 skb->dst = &rt->u.dst; 835 836 /* 837 * Push down and install the IPIP header. 838 */ 839 840 iph = skb->nh.iph; 841 iph->version = 4; 842 iph->ihl = sizeof(struct iphdr) >> 2; 843 iph->frag_off = df; 844 iph->protocol = IPPROTO_GRE; 845 iph->tos = ipgre_ecn_encapsulate(tos, old_iph, skb); 846 iph->daddr = rt->rt_dst; 847 iph->saddr = rt->rt_src; 848 849 if ((iph->ttl = tiph->ttl) == 0) { 850 if (skb->protocol == htons(ETH_P_IP)) 851 iph->ttl = old_iph->ttl; 852 #ifdef CONFIG_IPV6 853 else if (skb->protocol == htons(ETH_P_IPV6)) 854 iph->ttl = ((struct ipv6hdr*)old_iph)->hop_limit; 855 #endif 856 else 857 iph->ttl = dst_metric(&rt->u.dst, RTAX_HOPLIMIT); 858 } 859 860 ((u16*)(iph+1))[0] = tunnel->parms.o_flags; 861 ((u16*)(iph+1))[1] = skb->protocol; 862 863 if (tunnel->parms.o_flags&(GRE_KEY|GRE_CSUM|GRE_SEQ)) { 864 u32 *ptr = (u32*)(((u8*)iph) + tunnel->hlen - 4); 865 866 if (tunnel->parms.o_flags&GRE_SEQ) { 867 ++tunnel->o_seqno; 868 *ptr = htonl(tunnel->o_seqno); 869 ptr--; 870 } 871 if (tunnel->parms.o_flags&GRE_KEY) { 872 *ptr = tunnel->parms.o_key; 873 ptr--; 874 } 875 if (tunnel->parms.o_flags&GRE_CSUM) { 876 *ptr = 0; 877 *(__u16*)ptr = ip_compute_csum((void*)(iph+1), skb->len - sizeof(struct iphdr)); 878 } 879 } 880 881 nf_reset(skb); 882 883 IPTUNNEL_XMIT(); 884 tunnel->recursion--; 885 return 0; 886 887 tx_error_icmp: 888 dst_link_failure(skb); 889 890 tx_error: 891 stats->tx_errors++; 892 dev_kfree_skb(skb); 893 tunnel->recursion--; 894 return 0; 895 } 896 897 static int 898 ipgre_tunnel_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd) 899 { 900 int err = 0; 901 struct ip_tunnel_parm p; 902 struct ip_tunnel *t; 903 904 switch (cmd) { 905 case SIOCGETTUNNEL: 906 t = NULL; 907 if (dev == ipgre_fb_tunnel_dev) { 908 if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) { 909 err = -EFAULT; 910 break; 911 } 912 t = ipgre_tunnel_locate(&p, 0); 913 } 914 if (t == NULL) 915 t = netdev_priv(dev); 916 memcpy(&p, &t->parms, sizeof(p)); 917 if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p))) 918 err = -EFAULT; 919 break; 920 921 case SIOCADDTUNNEL: 922 case SIOCCHGTUNNEL: 923 err = -EPERM; 924 if (!capable(CAP_NET_ADMIN)) 925 goto done; 926 927 err = -EFAULT; 928 if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) 929 goto done; 930 931 err = -EINVAL; 932 if (p.iph.version != 4 || p.iph.protocol != IPPROTO_GRE || 933 p.iph.ihl != 5 || (p.iph.frag_off&htons(~IP_DF)) || 934 ((p.i_flags|p.o_flags)&(GRE_VERSION|GRE_ROUTING))) 935 goto done; 936 if (p.iph.ttl) 937 p.iph.frag_off |= htons(IP_DF); 938 939 if (!(p.i_flags&GRE_KEY)) 940 p.i_key = 0; 941 if (!(p.o_flags&GRE_KEY)) 942 p.o_key = 0; 943 944 t = ipgre_tunnel_locate(&p, cmd == SIOCADDTUNNEL); 945 946 if (dev != ipgre_fb_tunnel_dev && cmd == SIOCCHGTUNNEL) { 947 if (t != NULL) { 948 if (t->dev != dev) { 949 err = -EEXIST; 950 break; 951 } 952 } else { 953 unsigned nflags=0; 954 955 t = netdev_priv(dev); 956 957 if (MULTICAST(p.iph.daddr)) 958 nflags = IFF_BROADCAST; 959 else if (p.iph.daddr) 960 nflags = IFF_POINTOPOINT; 961 962 if ((dev->flags^nflags)&(IFF_POINTOPOINT|IFF_BROADCAST)) { 963 err = -EINVAL; 964 break; 965 } 966 ipgre_tunnel_unlink(t); 967 t->parms.iph.saddr = p.iph.saddr; 968 t->parms.iph.daddr = p.iph.daddr; 969 t->parms.i_key = p.i_key; 970 t->parms.o_key = p.o_key; 971 memcpy(dev->dev_addr, &p.iph.saddr, 4); 972 memcpy(dev->broadcast, &p.iph.daddr, 4); 973 ipgre_tunnel_link(t); 974 netdev_state_change(dev); 975 } 976 } 977 978 if (t) { 979 err = 0; 980 if (cmd == SIOCCHGTUNNEL) { 981 t->parms.iph.ttl = p.iph.ttl; 982 t->parms.iph.tos = p.iph.tos; 983 t->parms.iph.frag_off = p.iph.frag_off; 984 } 985 if (copy_to_user(ifr->ifr_ifru.ifru_data, &t->parms, sizeof(p))) 986 err = -EFAULT; 987 } else 988 err = (cmd == SIOCADDTUNNEL ? -ENOBUFS : -ENOENT); 989 break; 990 991 case SIOCDELTUNNEL: 992 err = -EPERM; 993 if (!capable(CAP_NET_ADMIN)) 994 goto done; 995 996 if (dev == ipgre_fb_tunnel_dev) { 997 err = -EFAULT; 998 if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) 999 goto done; 1000 err = -ENOENT; 1001 if ((t = ipgre_tunnel_locate(&p, 0)) == NULL) 1002 goto done; 1003 err = -EPERM; 1004 if (t == netdev_priv(ipgre_fb_tunnel_dev)) 1005 goto done; 1006 dev = t->dev; 1007 } 1008 err = unregister_netdevice(dev); 1009 break; 1010 1011 default: 1012 err = -EINVAL; 1013 } 1014 1015 done: 1016 return err; 1017 } 1018 1019 static struct net_device_stats *ipgre_tunnel_get_stats(struct net_device *dev) 1020 { 1021 return &(((struct ip_tunnel*)netdev_priv(dev))->stat); 1022 } 1023 1024 static int ipgre_tunnel_change_mtu(struct net_device *dev, int new_mtu) 1025 { 1026 struct ip_tunnel *tunnel = netdev_priv(dev); 1027 if (new_mtu < 68 || new_mtu > 0xFFF8 - tunnel->hlen) 1028 return -EINVAL; 1029 dev->mtu = new_mtu; 1030 return 0; 1031 } 1032 1033 #ifdef CONFIG_NET_IPGRE_BROADCAST 1034 /* Nice toy. Unfortunately, useless in real life :-) 1035 It allows to construct virtual multiprotocol broadcast "LAN" 1036 over the Internet, provided multicast routing is tuned. 1037 1038 1039 I have no idea was this bicycle invented before me, 1040 so that I had to set ARPHRD_IPGRE to a random value. 1041 I have an impression, that Cisco could make something similar, 1042 but this feature is apparently missing in IOS<=11.2(8). 1043 1044 I set up 10.66.66/24 and fec0:6666:6666::0/96 as virtual networks 1045 with broadcast 224.66.66.66. If you have access to mbone, play with me :-) 1046 1047 ping -t 255 224.66.66.66 1048 1049 If nobody answers, mbone does not work. 1050 1051 ip tunnel add Universe mode gre remote 224.66.66.66 local <Your_real_addr> ttl 255 1052 ip addr add 10.66.66.<somewhat>/24 dev Universe 1053 ifconfig Universe up 1054 ifconfig Universe add fe80::<Your_real_addr>/10 1055 ifconfig Universe add fec0:6666:6666::<Your_real_addr>/96 1056 ftp 10.66.66.66 1057 ... 1058 ftp fec0:6666:6666::193.233.7.65 1059 ... 1060 1061 */ 1062 1063 static int ipgre_header(struct sk_buff *skb, struct net_device *dev, unsigned short type, 1064 void *daddr, void *saddr, unsigned len) 1065 { 1066 struct ip_tunnel *t = netdev_priv(dev); 1067 struct iphdr *iph = (struct iphdr *)skb_push(skb, t->hlen); 1068 u16 *p = (u16*)(iph+1); 1069 1070 memcpy(iph, &t->parms.iph, sizeof(struct iphdr)); 1071 p[0] = t->parms.o_flags; 1072 p[1] = htons(type); 1073 1074 /* 1075 * Set the source hardware address. 1076 */ 1077 1078 if (saddr) 1079 memcpy(&iph->saddr, saddr, 4); 1080 1081 if (daddr) { 1082 memcpy(&iph->daddr, daddr, 4); 1083 return t->hlen; 1084 } 1085 if (iph->daddr && !MULTICAST(iph->daddr)) 1086 return t->hlen; 1087 1088 return -t->hlen; 1089 } 1090 1091 static int ipgre_open(struct net_device *dev) 1092 { 1093 struct ip_tunnel *t = netdev_priv(dev); 1094 1095 if (MULTICAST(t->parms.iph.daddr)) { 1096 struct flowi fl = { .oif = t->parms.link, 1097 .nl_u = { .ip4_u = 1098 { .daddr = t->parms.iph.daddr, 1099 .saddr = t->parms.iph.saddr, 1100 .tos = RT_TOS(t->parms.iph.tos) } }, 1101 .proto = IPPROTO_GRE }; 1102 struct rtable *rt; 1103 if (ip_route_output_key(&rt, &fl)) 1104 return -EADDRNOTAVAIL; 1105 dev = rt->u.dst.dev; 1106 ip_rt_put(rt); 1107 if (__in_dev_get_rtnl(dev) == NULL) 1108 return -EADDRNOTAVAIL; 1109 t->mlink = dev->ifindex; 1110 ip_mc_inc_group(__in_dev_get_rtnl(dev), t->parms.iph.daddr); 1111 } 1112 return 0; 1113 } 1114 1115 static int ipgre_close(struct net_device *dev) 1116 { 1117 struct ip_tunnel *t = netdev_priv(dev); 1118 if (MULTICAST(t->parms.iph.daddr) && t->mlink) { 1119 struct in_device *in_dev = inetdev_by_index(t->mlink); 1120 if (in_dev) { 1121 ip_mc_dec_group(in_dev, t->parms.iph.daddr); 1122 in_dev_put(in_dev); 1123 } 1124 } 1125 return 0; 1126 } 1127 1128 #endif 1129 1130 static void ipgre_tunnel_setup(struct net_device *dev) 1131 { 1132 SET_MODULE_OWNER(dev); 1133 dev->uninit = ipgre_tunnel_uninit; 1134 dev->destructor = free_netdev; 1135 dev->hard_start_xmit = ipgre_tunnel_xmit; 1136 dev->get_stats = ipgre_tunnel_get_stats; 1137 dev->do_ioctl = ipgre_tunnel_ioctl; 1138 dev->change_mtu = ipgre_tunnel_change_mtu; 1139 1140 dev->type = ARPHRD_IPGRE; 1141 dev->hard_header_len = LL_MAX_HEADER + sizeof(struct iphdr) + 4; 1142 dev->mtu = ETH_DATA_LEN - sizeof(struct iphdr) - 4; 1143 dev->flags = IFF_NOARP; 1144 dev->iflink = 0; 1145 dev->addr_len = 4; 1146 } 1147 1148 static int ipgre_tunnel_init(struct net_device *dev) 1149 { 1150 struct net_device *tdev = NULL; 1151 struct ip_tunnel *tunnel; 1152 struct iphdr *iph; 1153 int hlen = LL_MAX_HEADER; 1154 int mtu = ETH_DATA_LEN; 1155 int addend = sizeof(struct iphdr) + 4; 1156 1157 tunnel = netdev_priv(dev); 1158 iph = &tunnel->parms.iph; 1159 1160 tunnel->dev = dev; 1161 strcpy(tunnel->parms.name, dev->name); 1162 1163 memcpy(dev->dev_addr, &tunnel->parms.iph.saddr, 4); 1164 memcpy(dev->broadcast, &tunnel->parms.iph.daddr, 4); 1165 1166 /* Guess output device to choose reasonable mtu and hard_header_len */ 1167 1168 if (iph->daddr) { 1169 struct flowi fl = { .oif = tunnel->parms.link, 1170 .nl_u = { .ip4_u = 1171 { .daddr = iph->daddr, 1172 .saddr = iph->saddr, 1173 .tos = RT_TOS(iph->tos) } }, 1174 .proto = IPPROTO_GRE }; 1175 struct rtable *rt; 1176 if (!ip_route_output_key(&rt, &fl)) { 1177 tdev = rt->u.dst.dev; 1178 ip_rt_put(rt); 1179 } 1180 1181 dev->flags |= IFF_POINTOPOINT; 1182 1183 #ifdef CONFIG_NET_IPGRE_BROADCAST 1184 if (MULTICAST(iph->daddr)) { 1185 if (!iph->saddr) 1186 return -EINVAL; 1187 dev->flags = IFF_BROADCAST; 1188 dev->hard_header = ipgre_header; 1189 dev->open = ipgre_open; 1190 dev->stop = ipgre_close; 1191 } 1192 #endif 1193 } 1194 1195 if (!tdev && tunnel->parms.link) 1196 tdev = __dev_get_by_index(tunnel->parms.link); 1197 1198 if (tdev) { 1199 hlen = tdev->hard_header_len; 1200 mtu = tdev->mtu; 1201 } 1202 dev->iflink = tunnel->parms.link; 1203 1204 /* Precalculate GRE options length */ 1205 if (tunnel->parms.o_flags&(GRE_CSUM|GRE_KEY|GRE_SEQ)) { 1206 if (tunnel->parms.o_flags&GRE_CSUM) 1207 addend += 4; 1208 if (tunnel->parms.o_flags&GRE_KEY) 1209 addend += 4; 1210 if (tunnel->parms.o_flags&GRE_SEQ) 1211 addend += 4; 1212 } 1213 dev->hard_header_len = hlen + addend; 1214 dev->mtu = mtu - addend; 1215 tunnel->hlen = addend; 1216 return 0; 1217 } 1218 1219 static int __init ipgre_fb_tunnel_init(struct net_device *dev) 1220 { 1221 struct ip_tunnel *tunnel = netdev_priv(dev); 1222 struct iphdr *iph = &tunnel->parms.iph; 1223 1224 tunnel->dev = dev; 1225 strcpy(tunnel->parms.name, dev->name); 1226 1227 iph->version = 4; 1228 iph->protocol = IPPROTO_GRE; 1229 iph->ihl = 5; 1230 tunnel->hlen = sizeof(struct iphdr) + 4; 1231 1232 dev_hold(dev); 1233 tunnels_wc[0] = tunnel; 1234 return 0; 1235 } 1236 1237 1238 static struct net_protocol ipgre_protocol = { 1239 .handler = ipgre_rcv, 1240 .err_handler = ipgre_err, 1241 }; 1242 1243 1244 /* 1245 * And now the modules code and kernel interface. 1246 */ 1247 1248 static int __init ipgre_init(void) 1249 { 1250 int err; 1251 1252 printk(KERN_INFO "GRE over IPv4 tunneling driver\n"); 1253 1254 if (inet_add_protocol(&ipgre_protocol, IPPROTO_GRE) < 0) { 1255 printk(KERN_INFO "ipgre init: can't add protocol\n"); 1256 return -EAGAIN; 1257 } 1258 1259 ipgre_fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "gre0", 1260 ipgre_tunnel_setup); 1261 if (!ipgre_fb_tunnel_dev) { 1262 err = -ENOMEM; 1263 goto err1; 1264 } 1265 1266 ipgre_fb_tunnel_dev->init = ipgre_fb_tunnel_init; 1267 1268 if ((err = register_netdev(ipgre_fb_tunnel_dev))) 1269 goto err2; 1270 out: 1271 return err; 1272 err2: 1273 free_netdev(ipgre_fb_tunnel_dev); 1274 err1: 1275 inet_del_protocol(&ipgre_protocol, IPPROTO_GRE); 1276 goto out; 1277 } 1278 1279 static void __exit ipgre_destroy_tunnels(void) 1280 { 1281 int prio; 1282 1283 for (prio = 0; prio < 4; prio++) { 1284 int h; 1285 for (h = 0; h < HASH_SIZE; h++) { 1286 struct ip_tunnel *t; 1287 while ((t = tunnels[prio][h]) != NULL) 1288 unregister_netdevice(t->dev); 1289 } 1290 } 1291 } 1292 1293 static void __exit ipgre_fini(void) 1294 { 1295 if (inet_del_protocol(&ipgre_protocol, IPPROTO_GRE) < 0) 1296 printk(KERN_INFO "ipgre close: can't remove protocol\n"); 1297 1298 rtnl_lock(); 1299 ipgre_destroy_tunnels(); 1300 rtnl_unlock(); 1301 } 1302 1303 module_init(ipgre_init); 1304 module_exit(ipgre_fini); 1305 MODULE_LICENSE("GPL"); 1306