net/ipv4/ip_gre.c

   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/capability.h>
  14 #include <linux/module.h>
  15 #include <linux/types.h>
  16 #include <linux/kernel.h>
  17 #include <asm/uaccess.h>
  18 #include <linux/skbuff.h>
  19 #include <linux/netdevice.h>
  20 #include <linux/in.h>
  21 #include <linux/tcp.h>
  22 #include <linux/udp.h>
  23 #include <linux/if_arp.h>
  24 #include <linux/mroute.h>
  25 #include <linux/init.h>
  26 #include <linux/in6.h>
  27 #include <linux/inetdevice.h>
  28 #include <linux/igmp.h>
  29 #include <linux/netfilter_ipv4.h>
  30 #include <linux/if_ether.h>
  31
  32 #include <net/sock.h>
  33 #include <net/ip.h>
  34 #include <net/icmp.h>
  35 #include <net/protocol.h>
  36 #include <net/ipip.h>
  37 #include <net/arp.h>
  38 #include <net/checksum.h>
  39 #include <net/dsfield.h>
  40 #include <net/inet_ecn.h>
  41 #include <net/xfrm.h>
  42
  43 #ifdef CONFIG_IPV6
  44 #include <net/ipv6.h>
  45 #include <net/ip6_fib.h>
  46 #include <net/ip6_route.h>
  47 #endif
  48
  49 /*
  50    Problems & solutions
  51    --------------------
  52
  53    1. The most important issue is detecting local dead loops.
  54    They would cause complete host lockup in transmit, which
  55    would be "resolved" by stack overflow or, if queueing is enabled,
  56    with infinite looping in net_bh.
  57
  58    We cannot track such dead loops during route installation,
  59    it is infeasible task. The most general solutions would be
  60    to keep skb->encapsulation counter (sort of local ttl),
  61    and silently drop packet when it expires. It is the best
  62    solution, but it supposes maintaing new variable in ALL
  63    skb, even if no tunneling is used.
  64
  65    Current solution: t->recursion lock breaks dead loops. It looks
  66    like dev->tbusy flag, but I preferred new variable, because
  67    the semantics is different. One day, when hard_start_xmit
  68    will be multithreaded we will have to use skb->encapsulation.
  69
  70
  71
  72    2. Networking dead loops would not kill routers, but would really
  73    kill network. IP hop limit plays role of "t->recursion" in this case,
  74    if we copy it from packet being encapsulated to upper header.
  75    It is very good solution, but it introduces two problems:
  76
  77    - Routing protocols, using packets with ttl=1 (OSPF, RIP2),
  78      do not work over tunnels.
  79    - traceroute does not work. I planned to relay ICMP from tunnel,
  80      so that this problem would be solved and traceroute output
  81      would even more informative. This idea appeared to be wrong:
  82      only Linux complies to rfc1812 now (yes, guys, Linux is the only
  83      true router now :-)), all routers (at least, in neighbourhood of mine)
  84      return only 8 bytes of payload. It is the end.
  85
  86    Hence, if we want that OSPF worked or traceroute said something reasonable,
  87    we should search for another solution.
  88
  89    One of them is to parse packet trying to detect inner encapsulation
  90    made by our node. It is difficult or even impossible, especially,
  91    taking into account fragmentation. TO be short, tt is not solution at all.
  92
  93    Current solution: The solution was UNEXPECTEDLY SIMPLE.
  94    We force DF flag on tunnels with preconfigured hop limit,
  95    that is ALL. :-) Well, it does not remove the problem completely,
  96    but exponential growth of network traffic is changed to linear
  97    (branches, that exceed pmtu are pruned) and tunnel mtu
  98    fastly degrades to value <68, where looping stops.
  99    Yes, it is not good if there exists a router in the loop,
 100    which does not force DF, even when encapsulating packets have DF set.
 101    But it is not our problem! Nobody could accuse us, we made
 102    all that we could make. Even if it is your gated who injected
 103    fatal route to network, even if it were you who configured
 104    fatal static route: you are innocent. :-)
 105
 106
 107
 108    3. Really, ipv4/ipip.c, ipv4/ip_gre.c and ipv6/sit.c contain
 109    practically identical code. It would be good to glue them
 110    together, but it is not very evident, how to make them modular.
 111    sit is integral part of IPv6, ipip and gre are naturally modular.
 112    We could extract common parts (hash table, ioctl etc)
 113    to a separate module (ip_tunnel.c).
 114
 115    Alexey Kuznetsov.
 116  */
 117
 118 static int ipgre_tunnel_init(struct net_device *dev);
 119 static void ipgre_tunnel_setup(struct net_device *dev);
 120
 121 /* Fallback tunnel: no source, no destination, no key, no options */
 122
 123 static int ipgre_fb_tunnel_init(struct net_device *dev);
 124
 125 static struct net_device *ipgre_fb_tunnel_dev;
 126
 127 /* Tunnel hash table */
 128
 129 /*
 130    4 hash tables:
 131
 132    3: (remote,local)
 133    2: (remote,*)
 134    1: (*,local)
 135    0: (*,*)
 136
 137    We require exact key match i.e. if a key is present in packet
 138    it will match only tunnel with the same key; if it is not present,
 139    it will match only keyless tunnel.
 140
 141    All keysless packets, if not matched configured keyless tunnels
 142    will match fallback tunnel.
 143  */
 144
 145 #define HASH_SIZE  16
 146 #define HASH(addr) (((__force u32)addr^((__force u32)addr>>4))&0xF)
 147
 148 static struct ip_tunnel *tunnels[4][HASH_SIZE];
 149
 150 #define tunnels_r_l     (tunnels[3])
 151 #define tunnels_r       (tunnels[2])
 152 #define tunnels_l       (tunnels[1])
 153 #define tunnels_wc      (tunnels[0])
 154
 155 static DEFINE_RWLOCK(ipgre_lock);
 156
 157 /* Given src, dst and key, find appropriate for input tunnel. */
 158
 159 static struct ip_tunnel * ipgre_tunnel_lookup(__be32 remote, __be32 local, __be32 key)
 160 {
 161         unsigned h0 = HASH(remote);
 162         unsigned h1 = HASH(key);
 163         struct ip_tunnel *t;
 164
 165         for (t = tunnels_r_l[h0^h1]; t; t = t->next) {
 166                 if (local == t->parms.iph.saddr && remote == t->parms.iph.daddr) {
 167                         if (t->parms.i_key == key && (t->dev->flags&IFF_UP))
 168                                 return t;
 169                 }
 170         }
 171         for (t = tunnels_r[h0^h1]; t; t = t->next) {
 172                 if (remote == t->parms.iph.daddr) {
 173                         if (t->parms.i_key == key && (t->dev->flags&IFF_UP))
 174                                 return t;
 175                 }
 176         }
 177         for (t = tunnels_l[h1]; t; t = t->next) {
 178                 if (local == t->parms.iph.saddr ||
 179                      (local == t->parms.iph.daddr && MULTICAST(local))) {
 180                         if (t->parms.i_key == key && (t->dev->flags&IFF_UP))
 181                                 return t;
 182                 }
 183         }
 184         for (t = tunnels_wc[h1]; t; t = t->next) {
 185                 if (t->parms.i_key == key && (t->dev->flags&IFF_UP))
 186                         return t;
 187         }
 188
 189         if (ipgre_fb_tunnel_dev->flags&IFF_UP)
 190                 return netdev_priv(ipgre_fb_tunnel_dev);
 191         return NULL;
 192 }
 193
 194 static struct ip_tunnel **__ipgre_bucket(struct ip_tunnel_parm *parms)
 195 {
 196         __be32 remote = parms->iph.daddr;
 197         __be32 local = parms->iph.saddr;
 198         __be32 key = parms->i_key;
 199         unsigned h = HASH(key);
 200         int prio = 0;
 201
 202         if (local)
 203                 prio |= 1;
 204         if (remote && !MULTICAST(remote)) {
 205                 prio |= 2;
 206                 h ^= HASH(remote);
 207         }
 208
 209         return &tunnels[prio][h];
 210 }
 211
 212 static inline struct ip_tunnel **ipgre_bucket(struct ip_tunnel *t)
 213 {
 214         return __ipgre_bucket(&t->parms);
 215 }
 216
 217 static void ipgre_tunnel_link(struct ip_tunnel *t)
 218 {
 219         struct ip_tunnel **tp = ipgre_bucket(t);
 220
 221         t->next = *tp;
 222         write_lock_bh(&ipgre_lock);
 223         *tp = t;
 224         write_unlock_bh(&ipgre_lock);
 225 }
 226
 227 static void ipgre_tunnel_unlink(struct ip_tunnel *t)
 228 {
 229         struct ip_tunnel **tp;
 230
 231         for (tp = ipgre_bucket(t); *tp; tp = &(*tp)->next) {
 232                 if (t == *tp) {
 233                         write_lock_bh(&ipgre_lock);
 234                         *tp = t->next;
 235                         write_unlock_bh(&ipgre_lock);
 236                         break;
 237                 }
 238         }
 239 }
 240
 241 static struct ip_tunnel * ipgre_tunnel_locate(struct ip_tunnel_parm *parms, int create)
 242 {
 243         __be32 remote = parms->iph.daddr;
 244         __be32 local = parms->iph.saddr;
 245         __be32 key = parms->i_key;
 246         struct ip_tunnel *t, **tp, *nt;
 247         struct net_device *dev;
 248         char name[IFNAMSIZ];
 249
 250         for (tp = __ipgre_bucket(parms); (t = *tp) != NULL; tp = &t->next) {
 251                 if (local == t->parms.iph.saddr && remote == t->parms.iph.daddr) {
 252                         if (key == t->parms.i_key)
 253                                 return t;
 254                 }
 255         }
 256         if (!create)
 257                 return NULL;
 258
 259         if (parms->name[0])
 260                 strlcpy(name, parms->name, IFNAMSIZ);
 261         else {
 262                 int i;
 263                 for (i=1; i<100; i++) {
 264                         sprintf(name, "gre%d", i);
 265                         if (__dev_get_by_name(name) == NULL)
 266                                 break;
 267                 }
 268                 if (i==100)
 269                         goto failed;
 270         }
 271
 272         dev = alloc_netdev(sizeof(*t), name, ipgre_tunnel_setup);
 273         if (!dev)
 274           return NULL;
 275
 276         dev->init = ipgre_tunnel_init;
 277         nt = netdev_priv(dev);
 278         nt->parms = *parms;
 279
 280         if (register_netdevice(dev) < 0) {
 281                 free_netdev(dev);
 282                 goto failed;
 283         }
 284
 285         dev_hold(dev);
 286         ipgre_tunnel_link(nt);
 287         return nt;
 288
 289 failed:
 290         return NULL;
 291 }
 292
 293 static void ipgre_tunnel_uninit(struct net_device *dev)
 294 {
 295         ipgre_tunnel_unlink(netdev_priv(dev));
 296         dev_put(dev);
 297 }
 298
 299
 300 static void ipgre_err(struct sk_buff *skb, u32 info)
 301 {
 302 #ifndef I_WISH_WORLD_WERE_PERFECT
 303
 304 /* It is not :-( All the routers (except for Linux) return only
 305    8 bytes of packet payload. It means, that precise relaying of
 306    ICMP in the real Internet is absolutely infeasible.
 307
 308    Moreover, Cisco "wise men" put GRE key to the third word
 309    in GRE header. It makes impossible maintaining even soft state for keyed
 310    GRE tunnels with enabled checksum. Tell them "thank you".
 311
 312    Well, I wonder, rfc1812 was written by Cisco employee,
 313    what the hell these idiots break standrads established
 314    by themself???
 315  */
 316
 317         struct iphdr *iph = (struct iphdr*)skb->data;
 318         __be16       *p = (__be16*)(skb->data+(iph->ihl<<2));
 319         int grehlen = (iph->ihl<<2) + 4;
 320         const int type = icmp_hdr(skb)->type;
 321         const int code = icmp_hdr(skb)->code;
 322         struct ip_tunnel *t;
 323         __be16 flags;
 324
 325         flags = p[0];
 326         if (flags&(GRE_CSUM|GRE_KEY|GRE_SEQ|GRE_ROUTING|GRE_VERSION)) {
 327                 if (flags&(GRE_VERSION|GRE_ROUTING))
 328                         return;
 329                 if (flags&GRE_KEY) {
 330                         grehlen += 4;
 331                         if (flags&GRE_CSUM)
 332                                 grehlen += 4;
 333                 }
 334         }
 335
 336         /* If only 8 bytes returned, keyed message will be dropped here */
 337         if (skb_headlen(skb) < grehlen)
 338                 return;
 339
 340         switch (type) {
 341         default:
 342         case ICMP_PARAMETERPROB:
 343                 return;
 344
 345         case ICMP_DEST_UNREACH:
 346                 switch (code) {
 347                 case ICMP_SR_FAILED:
 348                 case ICMP_PORT_UNREACH:
 349                         /* Impossible event. */
 350                         return;
 351                 case ICMP_FRAG_NEEDED:
 352                         /* Soft state for pmtu is maintained by IP core. */
 353                         return;
 354                 default:
 355                         /* All others are translated to HOST_UNREACH.
 356                            rfc2003 contains "deep thoughts" about NET_UNREACH,
 357                            I believe they are just ether pollution. --ANK
 358                          */
 359                         break;
 360                 }
 361                 break;
 362         case ICMP_TIME_EXCEEDED:
 363                 if (code != ICMP_EXC_TTL)
 364                         return;
 365                 break;
 366         }
 367
 368         read_lock(&ipgre_lock);
 369         t = ipgre_tunnel_lookup(iph->daddr, iph->saddr, (flags&GRE_KEY) ? *(((__be32*)p) + (grehlen>>2) - 1) : 0);
 370         if (t == NULL || t->parms.iph.daddr == 0 || MULTICAST(t->parms.iph.daddr))
 371                 goto out;
 372
 373         if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)
 374                 goto out;
 375
 376         if (jiffies - t->err_time < IPTUNNEL_ERR_TIMEO)
 377                 t->err_count++;
 378         else
 379                 t->err_count = 1;
 380         t->err_time = jiffies;
 381 out:
 382         read_unlock(&ipgre_lock);
 383         return;
 384 #else
 385         struct iphdr *iph = (struct iphdr*)dp;
 386         struct iphdr *eiph;
 387         __be16       *p = (__be16*)(dp+(iph->ihl<<2));
 388         const int type = icmp_hdr(skb)->type;
 389         const int code = icmp_hdr(skb)->code;
 390         int rel_type = 0;
 391         int rel_code = 0;
 392         __be32 rel_info = 0;
 393         __u32 n = 0;
 394         __be16 flags;
 395         int grehlen = (iph->ihl<<2) + 4;
 396         struct sk_buff *skb2;
 397         struct flowi fl;
 398         struct rtable *rt;
 399
 400         if (p[1] != htons(ETH_P_IP))
 401                 return;
 402
 403         flags = p[0];
 404         if (flags&(GRE_CSUM|GRE_KEY|GRE_SEQ|GRE_ROUTING|GRE_VERSION)) {
 405                 if (flags&(GRE_VERSION|GRE_ROUTING))
 406                         return;
 407                 if (flags&GRE_CSUM)
 408                         grehlen += 4;
 409                 if (flags&GRE_KEY)
 410                         grehlen += 4;
 411                 if (flags&GRE_SEQ)
 412                         grehlen += 4;
 413         }
 414         if (len < grehlen + sizeof(struct iphdr))
 415                 return;
 416         eiph = (struct iphdr*)(dp + grehlen);
 417
 418         switch (type) {
 419         default:
 420                 return;
 421         case ICMP_PARAMETERPROB:
 422                 n = ntohl(icmp_hdr(skb)->un.gateway) >> 24;
 423                 if (n < (iph->ihl<<2))
 424                         return;
 425
 426                 /* So... This guy found something strange INSIDE encapsulated
 427                    packet. Well, he is fool, but what can we do ?
 428                  */
 429                 rel_type = ICMP_PARAMETERPROB;
 430                 n -= grehlen;
 431                 rel_info = htonl(n << 24);
 432                 break;
 433
 434         case ICMP_DEST_UNREACH:
 435                 switch (code) {
 436                 case ICMP_SR_FAILED:
 437                 case ICMP_PORT_UNREACH:
 438                         /* Impossible event. */
 439                         return;
 440                 case ICMP_FRAG_NEEDED:
 441                         /* And it is the only really necessary thing :-) */
 442                         n = ntohs(icmp_hdr(skb)->un.frag.mtu);
 443                         if (n < grehlen+68)
 444                                 return;
 445                         n -= grehlen;
 446                         /* BSD 4.2 MORE DOES NOT EXIST IN NATURE. */
 447                         if (n > ntohs(eiph->tot_len))
 448                                 return;
 449                         rel_info = htonl(n);
 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         skb_reset_network_header(skb2);
 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 (n > dst_mtu(skb2->dst)) {
 512                         kfree_skb(skb2);
 513                         return;
 514                 }
 515                 skb2->dst->ops->update_pmtu(skb2->dst, n);
 516         } else if (type == ICMP_TIME_EXCEEDED) {
 517                 struct ip_tunnel *t = netdev_priv(skb2->dev);
 518                 if (t->parms.iph.ttl) {
 519                         rel_type = ICMP_DEST_UNREACH;
 520                         rel_code = ICMP_HOST_UNREACH;
 521                 }
 522         }
 523
 524         icmp_send(skb2, rel_type, rel_code, rel_info);
 525         kfree_skb(skb2);
 526 #endif
 527 }
 528
 529 static inline void ipgre_ecn_decapsulate(struct iphdr *iph, struct sk_buff *skb)
 530 {
 531         if (INET_ECN_is_ce(iph->tos)) {
 532                 if (skb->protocol == htons(ETH_P_IP)) {
 533                         IP_ECN_set_ce(ip_hdr(skb));
 534                 } else if (skb->protocol == htons(ETH_P_IPV6)) {
 535                         IP6_ECN_set_ce(ipv6_hdr(skb));
 536                 }
 537         }
 538 }
 539
 540 static inline u8
 541 ipgre_ecn_encapsulate(u8 tos, struct iphdr *old_iph, struct sk_buff *skb)
 542 {
 543         u8 inner = 0;
 544         if (skb->protocol == htons(ETH_P_IP))
 545                 inner = old_iph->tos;
 546         else if (skb->protocol == htons(ETH_P_IPV6))
 547                 inner = ipv6_get_dsfield((struct ipv6hdr *)old_iph);
 548         return INET_ECN_encapsulate(tos, inner);
 549 }
 550
 551 static int ipgre_rcv(struct sk_buff *skb)
 552 {
 553         struct iphdr *iph;
 554         u8     *h;
 555         __be16    flags;
 556         __sum16   csum = 0;
 557         __be32 key = 0;
 558         u32    seqno = 0;
 559         struct ip_tunnel *tunnel;
 560         int    offset = 4;
 561
 562         if (!pskb_may_pull(skb, 16))
 563                 goto drop_nolock;
 564
 565         iph = ip_hdr(skb);
 566         h = skb->data;
 567         flags = *(__be16*)h;
 568
 569         if (flags&(GRE_CSUM|GRE_KEY|GRE_ROUTING|GRE_SEQ|GRE_VERSION)) {
 570                 /* - Version must be 0.
 571                    - We do not support routing headers.
 572                  */
 573                 if (flags&(GRE_VERSION|GRE_ROUTING))
 574                         goto drop_nolock;
 575
 576                 if (flags&GRE_CSUM) {
 577                         switch (skb->ip_summed) {
 578                         case CHECKSUM_COMPLETE:
 579                                 csum = csum_fold(skb->csum);
 580                                 if (!csum)
 581                                         break;
 582                                 /* fall through */
 583                         case CHECKSUM_NONE:
 584                                 skb->csum = 0;
 585                                 csum = __skb_checksum_complete(skb);
 586                                 skb->ip_summed = CHECKSUM_COMPLETE;
 587                         }
 588                         offset += 4;
 589                 }
 590                 if (flags&GRE_KEY) {
 591                         key = *(__be32*)(h + offset);
 592                         offset += 4;
 593                 }
 594                 if (flags&GRE_SEQ) {
 595                         seqno = ntohl(*(__be32*)(h + offset));
 596                         offset += 4;
 597                 }
 598         }
 599
 600         read_lock(&ipgre_lock);
 601         if ((tunnel = ipgre_tunnel_lookup(iph->saddr, iph->daddr, key)) != NULL) {
 602                 secpath_reset(skb);
 603
 604                 skb->protocol = *(__be16*)(h + 2);
 605                 /* WCCP version 1 and 2 protocol decoding.
 606                  * - Change protocol to IP
 607                  * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
 608                  */
 609                 if (flags == 0 &&
 610                     skb->protocol == htons(ETH_P_WCCP)) {
 611                         skb->protocol = htons(ETH_P_IP);
 612                         if ((*(h + offset) & 0xF0) != 0x40)
 613                                 offset += 4;
 614                 }
 615
 616                 skb_reset_mac_header(skb);
 617                 __pskb_pull(skb, offset);
 618                 skb_reset_network_header(skb);
 619                 skb_postpull_rcsum(skb, skb_transport_header(skb), offset);
 620                 skb->pkt_type = PACKET_HOST;
 621 #ifdef CONFIG_NET_IPGRE_BROADCAST
 622                 if (MULTICAST(iph->daddr)) {
 623                         /* Looped back packet, drop it! */
 624                         if (((struct rtable*)skb->dst)->fl.iif == 0)
 625                                 goto drop;
 626                         tunnel->stat.multicast++;
 627                         skb->pkt_type = PACKET_BROADCAST;
 628                 }
 629 #endif
 630
 631                 if (((flags&GRE_CSUM) && csum) ||
 632                     (!(flags&GRE_CSUM) && tunnel->parms.i_flags&GRE_CSUM)) {
 633                         tunnel->stat.rx_crc_errors++;
 634                         tunnel->stat.rx_errors++;
 635                         goto drop;
 636                 }
 637                 if (tunnel->parms.i_flags&GRE_SEQ) {
 638                         if (!(flags&GRE_SEQ) ||
 639                             (tunnel->i_seqno && (s32)(seqno - tunnel->i_seqno) < 0)) {
 640                                 tunnel->stat.rx_fifo_errors++;
 641                                 tunnel->stat.rx_errors++;
 642                                 goto drop;
 643                         }
 644                         tunnel->i_seqno = seqno + 1;
 645                 }
 646                 tunnel->stat.rx_packets++;
 647                 tunnel->stat.rx_bytes += skb->len;
 648                 skb->dev = tunnel->dev;
 649                 dst_release(skb->dst);
 650                 skb->dst = NULL;
 651                 nf_reset(skb);
 652                 ipgre_ecn_decapsulate(iph, skb);
 653                 netif_rx(skb);
 654                 read_unlock(&ipgre_lock);
 655                 return(0);
 656         }
 657         icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
 658
 659 drop:
 660         read_unlock(&ipgre_lock);
 661 drop_nolock:
 662         kfree_skb(skb);
 663         return(0);
 664 }
 665
 666 static int ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 667 {
 668         struct ip_tunnel *tunnel = netdev_priv(dev);
 669         struct net_device_stats *stats = &tunnel->stat;
 670         struct iphdr  *old_iph = ip_hdr(skb);
 671         struct iphdr  *tiph;
 672         u8     tos;
 673         __be16 df;
 674         struct rtable *rt;                      /* Route to the other host */
 675         struct net_device *tdev;                        /* Device to other host */
 676         struct iphdr  *iph;                     /* Our new IP header */
 677         int    max_headroom;                    /* The extra header space needed */
 678         int    gre_hlen;
 679         __be32 dst;
 680         int    mtu;
 681
 682         if (tunnel->recursion++) {
 683                 tunnel->stat.collisions++;
 684                 goto tx_error;
 685         }
 686
 687         if (dev->hard_header) {
 688                 gre_hlen = 0;
 689                 tiph = (struct iphdr*)skb->data;
 690         } else {
 691                 gre_hlen = tunnel->hlen;
 692                 tiph = &tunnel->parms.iph;
 693         }
 694
 695         if ((dst = tiph->daddr) == 0) {
 696                 /* NBMA tunnel */
 697
 698                 if (skb->dst == NULL) {
 699                         tunnel->stat.tx_fifo_errors++;
 700                         goto tx_error;
 701                 }
 702
 703                 if (skb->protocol == htons(ETH_P_IP)) {
 704                         rt = (struct rtable*)skb->dst;
 705                         if ((dst = rt->rt_gateway) == 0)
 706                                 goto tx_error_icmp;
 707                 }
 708 #ifdef CONFIG_IPV6
 709                 else if (skb->protocol == htons(ETH_P_IPV6)) {
 710                         struct in6_addr *addr6;
 711                         int addr_type;
 712                         struct neighbour *neigh = skb->dst->neighbour;
 713
 714                         if (neigh == NULL)
 715                                 goto tx_error;
 716
 717                         addr6 = (struct in6_addr*)&neigh->primary_key;
 718                         addr_type = ipv6_addr_type(addr6);
 719
 720                         if (addr_type == IPV6_ADDR_ANY) {
 721                                 addr6 = &ipv6_hdr(skb)->daddr;
 722                                 addr_type = ipv6_addr_type(addr6);
 723                         }
 724
 725                         if ((addr_type & IPV6_ADDR_COMPATv4) == 0)
 726                                 goto tx_error_icmp;
 727
 728                         dst = addr6->s6_addr32[3];
 729                 }
 730 #endif
 731                 else
 732                         goto tx_error;
 733         }
 734
 735         tos = tiph->tos;
 736         if (tos&1) {
 737                 if (skb->protocol == htons(ETH_P_IP))
 738                         tos = old_iph->tos;
 739                 tos &= ~1;
 740         }
 741
 742         {
 743                 struct flowi fl = { .oif = tunnel->parms.link,
 744                                     .nl_u = { .ip4_u =
 745                                               { .daddr = dst,
 746                                                 .saddr = tiph->saddr,
 747                                                 .tos = RT_TOS(tos) } },
 748                                     .proto = IPPROTO_GRE };
 749                 if (ip_route_output_key(&rt, &fl)) {
 750                         tunnel->stat.tx_carrier_errors++;
 751                         goto tx_error;
 752                 }
 753         }
 754         tdev = rt->u.dst.dev;
 755
 756         if (tdev == dev) {
 757                 ip_rt_put(rt);
 758                 tunnel->stat.collisions++;
 759                 goto tx_error;
 760         }
 761
 762         df = tiph->frag_off;
 763         if (df)
 764                 mtu = dst_mtu(&rt->u.dst) - tunnel->hlen;
 765         else
 766                 mtu = skb->dst ? dst_mtu(skb->dst) : dev->mtu;
 767
 768         if (skb->dst)
 769                 skb->dst->ops->update_pmtu(skb->dst, mtu);
 770
 771         if (skb->protocol == htons(ETH_P_IP)) {
 772                 df |= (old_iph->frag_off&htons(IP_DF));
 773
 774                 if ((old_iph->frag_off&htons(IP_DF)) &&
 775                     mtu < ntohs(old_iph->tot_len)) {
 776                         icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
 777                         ip_rt_put(rt);
 778                         goto tx_error;
 779                 }
 780         }
 781 #ifdef CONFIG_IPV6
 782         else if (skb->protocol == htons(ETH_P_IPV6)) {
 783                 struct rt6_info *rt6 = (struct rt6_info*)skb->dst;
 784
 785                 if (rt6 && mtu < dst_mtu(skb->dst) && mtu >= IPV6_MIN_MTU) {
 786                         if ((tunnel->parms.iph.daddr && !MULTICAST(tunnel->parms.iph.daddr)) ||
 787                             rt6->rt6i_dst.plen == 128) {
 788                                 rt6->rt6i_flags |= RTF_MODIFIED;
 789                                 skb->dst->metrics[RTAX_MTU-1] = mtu;
 790                         }
 791                 }
 792
 793                 if (mtu >= IPV6_MIN_MTU && mtu < skb->len - tunnel->hlen + gre_hlen) {
 794                         icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, dev);
 795                         ip_rt_put(rt);
 796                         goto tx_error;
 797                 }
 798         }
 799 #endif
 800
 801         if (tunnel->err_count > 0) {
 802                 if (jiffies - tunnel->err_time < IPTUNNEL_ERR_TIMEO) {
 803                         tunnel->err_count--;
 804
 805                         dst_link_failure(skb);
 806                 } else
 807                         tunnel->err_count = 0;
 808         }
 809
 810         max_headroom = LL_RESERVED_SPACE(tdev) + gre_hlen;
 811
 812         if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) {
 813                 struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
 814                 if (!new_skb) {
 815                         ip_rt_put(rt);
 816                         stats->tx_dropped++;
 817                         dev_kfree_skb(skb);
 818                         tunnel->recursion--;
 819                         return 0;
 820                 }
 821                 if (skb->sk)
 822                         skb_set_owner_w(new_skb, skb->sk);
 823                 dev_kfree_skb(skb);
 824                 skb = new_skb;
 825                 old_iph = ip_hdr(skb);
 826         }
 827
 828         skb->transport_header = skb->network_header;
 829         skb_push(skb, gre_hlen);
 830         skb_reset_network_header(skb);
 831         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 832         IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
 833                               IPSKB_REROUTED);
 834         dst_release(skb->dst);
 835         skb->dst = &rt->u.dst;
 836
 837         /*
 838          *      Push down and install the IPIP header.
 839          */
 840
 841         iph                     =       ip_hdr(skb);
 842         iph->version            =       4;
 843         iph->ihl                =       sizeof(struct iphdr) >> 2;
 844         iph->frag_off           =       df;
 845         iph->protocol           =       IPPROTO_GRE;
 846         iph->tos                =       ipgre_ecn_encapsulate(tos, old_iph, skb);
 847         iph->daddr              =       rt->rt_dst;
 848         iph->saddr              =       rt->rt_src;
 849
 850         if ((iph->ttl = tiph->ttl) == 0) {
 851                 if (skb->protocol == htons(ETH_P_IP))
 852                         iph->ttl = old_iph->ttl;
 853 #ifdef CONFIG_IPV6
 854                 else if (skb->protocol == htons(ETH_P_IPV6))
 855                         iph->ttl = ((struct ipv6hdr*)old_iph)->hop_limit;
 856 #endif
 857                 else
 858                         iph->ttl = dst_metric(&rt->u.dst, RTAX_HOPLIMIT);
 859         }
 860
 861         ((__be16*)(iph+1))[0] = tunnel->parms.o_flags;
 862         ((__be16*)(iph+1))[1] = skb->protocol;
 863
 864         if (tunnel->parms.o_flags&(GRE_KEY|GRE_CSUM|GRE_SEQ)) {
 865                 __be32 *ptr = (__be32*)(((u8*)iph) + tunnel->hlen - 4);
 866
 867                 if (tunnel->parms.o_flags&GRE_SEQ) {
 868                         ++tunnel->o_seqno;
 869                         *ptr = htonl(tunnel->o_seqno);
 870                         ptr--;
 871                 }
 872                 if (tunnel->parms.o_flags&GRE_KEY) {
 873                         *ptr = tunnel->parms.o_key;
 874                         ptr--;
 875                 }
 876                 if (tunnel->parms.o_flags&GRE_CSUM) {
 877                         *ptr = 0;
 878                         *(__sum16*)ptr = ip_compute_csum((void*)(iph+1), skb->len - sizeof(struct iphdr));
 879                 }
 880         }
 881
 882         nf_reset(skb);
 883
 884         IPTUNNEL_XMIT();
 885         tunnel->recursion--;
 886         return 0;
 887
 888 tx_error_icmp:
 889         dst_link_failure(skb);
 890
 891 tx_error:
 892         stats->tx_errors++;
 893         dev_kfree_skb(skb);
 894         tunnel->recursion--;
 895         return 0;
 896 }
 897
 898 static int
 899 ipgre_tunnel_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd)
 900 {
 901         int err = 0;
 902         struct ip_tunnel_parm p;
 903         struct ip_tunnel *t;
 904
 905         switch (cmd) {
 906         case SIOCGETTUNNEL:
 907                 t = NULL;
 908                 if (dev == ipgre_fb_tunnel_dev) {
 909                         if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) {
 910                                 err = -EFAULT;
 911                                 break;
 912                         }
 913                         t = ipgre_tunnel_locate(&p, 0);
 914                 }
 915                 if (t == NULL)
 916                         t = netdev_priv(dev);
 917                 memcpy(&p, &t->parms, sizeof(p));
 918                 if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
 919                         err = -EFAULT;
 920                 break;
 921
 922         case SIOCADDTUNNEL:
 923         case SIOCCHGTUNNEL:
 924                 err = -EPERM;
 925                 if (!capable(CAP_NET_ADMIN))
 926                         goto done;
 927
 928                 err = -EFAULT;
 929                 if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
 930                         goto done;
 931
 932                 err = -EINVAL;
 933                 if (p.iph.version != 4 || p.iph.protocol != IPPROTO_GRE ||
 934                     p.iph.ihl != 5 || (p.iph.frag_off&htons(~IP_DF)) ||
 935                     ((p.i_flags|p.o_flags)&(GRE_VERSION|GRE_ROUTING)))
 936                         goto done;
 937                 if (p.iph.ttl)
 938                         p.iph.frag_off |= htons(IP_DF);
 939
 940                 if (!(p.i_flags&GRE_KEY))
 941                         p.i_key = 0;
 942                 if (!(p.o_flags&GRE_KEY))
 943                         p.o_key = 0;
 944
 945                 t = ipgre_tunnel_locate(&p, cmd == SIOCADDTUNNEL);
 946
 947                 if (dev != ipgre_fb_tunnel_dev && cmd == SIOCCHGTUNNEL) {
 948                         if (t != NULL) {
 949                                 if (t->dev != dev) {
 950                                         err = -EEXIST;
 951                                         break;
 952                                 }
 953                         } else {
 954                                 unsigned nflags=0;
 955
 956                                 t = netdev_priv(dev);
 957
 958                                 if (MULTICAST(p.iph.daddr))
 959                                         nflags = IFF_BROADCAST;
 960                                 else if (p.iph.daddr)
 961                                         nflags = IFF_POINTOPOINT;
 962
 963                                 if ((dev->flags^nflags)&(IFF_POINTOPOINT|IFF_BROADCAST)) {
 964                                         err = -EINVAL;
 965                                         break;
 966                                 }
 967                                 ipgre_tunnel_unlink(t);
 968                                 t->parms.iph.saddr = p.iph.saddr;
 969                                 t->parms.iph.daddr = p.iph.daddr;
 970                                 t->parms.i_key = p.i_key;
 971                                 t->parms.o_key = p.o_key;
 972                                 memcpy(dev->dev_addr, &p.iph.saddr, 4);
 973                                 memcpy(dev->broadcast, &p.iph.daddr, 4);
 974                                 ipgre_tunnel_link(t);
 975                                 netdev_state_change(dev);
 976                         }
 977                 }
 978
 979                 if (t) {
 980                         err = 0;
 981                         if (cmd == SIOCCHGTUNNEL) {
 982                                 t->parms.iph.ttl = p.iph.ttl;
 983                                 t->parms.iph.tos = p.iph.tos;
 984                                 t->parms.iph.frag_off = p.iph.frag_off;
 985                         }
 986                         if (copy_to_user(ifr->ifr_ifru.ifru_data, &t->parms, sizeof(p)))
 987                                 err = -EFAULT;
 988                 } else
 989                         err = (cmd == SIOCADDTUNNEL ? -ENOBUFS : -ENOENT);
 990                 break;
 991
 992         case SIOCDELTUNNEL:
 993                 err = -EPERM;
 994                 if (!capable(CAP_NET_ADMIN))
 995                         goto done;
 996
 997                 if (dev == ipgre_fb_tunnel_dev) {
 998                         err = -EFAULT;
 999                         if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
1000                                 goto done;
1001                         err = -ENOENT;
1002                         if ((t = ipgre_tunnel_locate(&p, 0)) == NULL)
1003                                 goto done;
1004                         err = -EPERM;
1005                         if (t == netdev_priv(ipgre_fb_tunnel_dev))
1006                                 goto done;
1007                         dev = t->dev;
1008                 }
1009                 unregister_netdevice(dev);
1010                 err = 0;
1011                 break;
1012
1013         default:
1014                 err = -EINVAL;
1015         }
1016
1017 done:
1018         return err;
1019 }
1020
1021 static struct net_device_stats *ipgre_tunnel_get_stats(struct net_device *dev)
1022 {
1023         return &(((struct ip_tunnel*)netdev_priv(dev))->stat);
1024 }
1025
1026 static int ipgre_tunnel_change_mtu(struct net_device *dev, int new_mtu)
1027 {
1028         struct ip_tunnel *tunnel = netdev_priv(dev);
1029         if (new_mtu < 68 || new_mtu > 0xFFF8 - tunnel->hlen)
1030                 return -EINVAL;
1031         dev->mtu = new_mtu;
1032         return 0;
1033 }
1034
1035 #ifdef CONFIG_NET_IPGRE_BROADCAST
1036 /* Nice toy. Unfortunately, useless in real life :-)
1037    It allows to construct virtual multiprotocol broadcast "LAN"
1038    over the Internet, provided multicast routing is tuned.
1039
1040
1041    I have no idea was this bicycle invented before me,
1042    so that I had to set ARPHRD_IPGRE to a random value.
1043    I have an impression, that Cisco could make something similar,
1044    but this feature is apparently missing in IOS<=11.2(8).
1045
1046    I set up 10.66.66/24 and fec0:6666:6666::0/96 as virtual networks
1047    with broadcast 224.66.66.66. If you have access to mbone, play with me :-)
1048
1049    ping -t 255 224.66.66.66
1050
1051    If nobody answers, mbone does not work.
1052
1053    ip tunnel add Universe mode gre remote 224.66.66.66 local <Your_real_addr> ttl 255
1054    ip addr add 10.66.66.<somewhat>/24 dev Universe
1055    ifconfig Universe up
1056    ifconfig Universe add fe80::<Your_real_addr>/10
1057    ifconfig Universe add fec0:6666:6666::<Your_real_addr>/96
1058    ftp 10.66.66.66
1059    ...
1060    ftp fec0:6666:6666::193.233.7.65
1061    ...
1062
1063  */
1064
1065 static int ipgre_header(struct sk_buff *skb, struct net_device *dev, unsigned short type,
1066                         void *daddr, void *saddr, unsigned len)
1067 {
1068         struct ip_tunnel *t = netdev_priv(dev);
1069         struct iphdr *iph = (struct iphdr *)skb_push(skb, t->hlen);
1070         __be16 *p = (__be16*)(iph+1);
1071
1072         memcpy(iph, &t->parms.iph, sizeof(struct iphdr));
1073         p[0]            = t->parms.o_flags;
1074         p[1]            = htons(type);
1075
1076         /*
1077          *      Set the source hardware address.
1078          */
1079
1080         if (saddr)
1081                 memcpy(&iph->saddr, saddr, 4);
1082
1083         if (daddr) {
1084                 memcpy(&iph->daddr, daddr, 4);
1085                 return t->hlen;
1086         }
1087         if (iph->daddr && !MULTICAST(iph->daddr))
1088                 return t->hlen;
1089
1090         return -t->hlen;
1091 }
1092
1093 static int ipgre_open(struct net_device *dev)
1094 {
1095         struct ip_tunnel *t = netdev_priv(dev);
1096
1097         if (MULTICAST(t->parms.iph.daddr)) {
1098                 struct flowi fl = { .oif = t->parms.link,
1099                                     .nl_u = { .ip4_u =
1100                                               { .daddr = t->parms.iph.daddr,
1101                                                 .saddr = t->parms.iph.saddr,
1102                                                 .tos = RT_TOS(t->parms.iph.tos) } },
1103                                     .proto = IPPROTO_GRE };
1104                 struct rtable *rt;
1105                 if (ip_route_output_key(&rt, &fl))
1106                         return -EADDRNOTAVAIL;
1107                 dev = rt->u.dst.dev;
1108                 ip_rt_put(rt);
1109                 if (__in_dev_get_rtnl(dev) == NULL)
1110                         return -EADDRNOTAVAIL;
1111                 t->mlink = dev->ifindex;
1112                 ip_mc_inc_group(__in_dev_get_rtnl(dev), t->parms.iph.daddr);
1113         }
1114         return 0;
1115 }
1116
1117 static int ipgre_close(struct net_device *dev)
1118 {
1119         struct ip_tunnel *t = netdev_priv(dev);
1120         if (MULTICAST(t->parms.iph.daddr) && t->mlink) {
1121                 struct in_device *in_dev = inetdev_by_index(t->mlink);
1122                 if (in_dev) {
1123                         ip_mc_dec_group(in_dev, t->parms.iph.daddr);
1124                         in_dev_put(in_dev);
1125                 }
1126         }
1127         return 0;
1128 }
1129
1130 #endif
1131
1132 static void ipgre_tunnel_setup(struct net_device *dev)
1133 {
1134         SET_MODULE_OWNER(dev);
1135         dev->uninit             = ipgre_tunnel_uninit;
1136         dev->destructor         = free_netdev;
1137         dev->hard_start_xmit    = ipgre_tunnel_xmit;
1138         dev->get_stats          = ipgre_tunnel_get_stats;
1139         dev->do_ioctl           = ipgre_tunnel_ioctl;
1140         dev->change_mtu         = ipgre_tunnel_change_mtu;
1141
1142         dev->type               = ARPHRD_IPGRE;
1143         dev->hard_header_len    = LL_MAX_HEADER + sizeof(struct iphdr) + 4;
1144         dev->mtu                = ETH_DATA_LEN - sizeof(struct iphdr) - 4;
1145         dev->flags              = IFF_NOARP;
1146         dev->iflink             = 0;
1147         dev->addr_len           = 4;
1148 }
1149
1150 static int ipgre_tunnel_init(struct net_device *dev)
1151 {
1152         struct net_device *tdev = NULL;
1153         struct ip_tunnel *tunnel;
1154         struct iphdr *iph;
1155         int hlen = LL_MAX_HEADER;
1156         int mtu = ETH_DATA_LEN;
1157         int addend = sizeof(struct iphdr) + 4;
1158
1159         tunnel = netdev_priv(dev);
1160         iph = &tunnel->parms.iph;
1161
1162         tunnel->dev = dev;
1163         strcpy(tunnel->parms.name, dev->name);
1164
1165         memcpy(dev->dev_addr, &tunnel->parms.iph.saddr, 4);
1166         memcpy(dev->broadcast, &tunnel->parms.iph.daddr, 4);
1167
1168         /* Guess output device to choose reasonable mtu and hard_header_len */
1169
1170         if (iph->daddr) {
1171                 struct flowi fl = { .oif = tunnel->parms.link,
1172                                     .nl_u = { .ip4_u =
1173                                               { .daddr = iph->daddr,
1174                                                 .saddr = iph->saddr,
1175                                                 .tos = RT_TOS(iph->tos) } },
1176                                     .proto = IPPROTO_GRE };
1177                 struct rtable *rt;
1178                 if (!ip_route_output_key(&rt, &fl)) {
1179                         tdev = rt->u.dst.dev;
1180                         ip_rt_put(rt);
1181                 }
1182
1183                 dev->flags |= IFF_POINTOPOINT;
1184
1185 #ifdef CONFIG_NET_IPGRE_BROADCAST
1186                 if (MULTICAST(iph->daddr)) {
1187                         if (!iph->saddr)
1188                                 return -EINVAL;
1189                         dev->flags = IFF_BROADCAST;
1190                         dev->hard_header = ipgre_header;
1191                         dev->open = ipgre_open;
1192                         dev->stop = ipgre_close;
1193                 }
1194 #endif
1195         }
1196
1197         if (!tdev && tunnel->parms.link)
1198                 tdev = __dev_get_by_index(tunnel->parms.link);
1199
1200         if (tdev) {
1201                 hlen = tdev->hard_header_len;
1202                 mtu = tdev->mtu;
1203         }
1204         dev->iflink = tunnel->parms.link;
1205
1206         /* Precalculate GRE options length */
1207         if (tunnel->parms.o_flags&(GRE_CSUM|GRE_KEY|GRE_SEQ)) {
1208                 if (tunnel->parms.o_flags&GRE_CSUM)
1209                         addend += 4;
1210                 if (tunnel->parms.o_flags&GRE_KEY)
1211                         addend += 4;
1212                 if (tunnel->parms.o_flags&GRE_SEQ)
1213                         addend += 4;
1214         }
1215         dev->hard_header_len = hlen + addend;
1216         dev->mtu = mtu - addend;
1217         tunnel->hlen = addend;
1218         return 0;
1219 }
1220
1221 static int __init ipgre_fb_tunnel_init(struct net_device *dev)
1222 {
1223         struct ip_tunnel *tunnel = netdev_priv(dev);
1224         struct iphdr *iph = &tunnel->parms.iph;
1225
1226         tunnel->dev = dev;
1227         strcpy(tunnel->parms.name, dev->name);
1228
1229         iph->version            = 4;
1230         iph->protocol           = IPPROTO_GRE;
1231         iph->ihl                = 5;
1232         tunnel->hlen            = sizeof(struct iphdr) + 4;
1233
1234         dev_hold(dev);
1235         tunnels_wc[0]           = tunnel;
1236         return 0;
1237 }
1238
1239
1240 static struct net_protocol ipgre_protocol = {
1241         .handler        =       ipgre_rcv,
1242         .err_handler    =       ipgre_err,
1243 };
1244
1245
1246 /*
1247  *      And now the modules code and kernel interface.
1248  */
1249
1250 static int __init ipgre_init(void)
1251 {
1252         int err;
1253
1254         printk(KERN_INFO "GRE over IPv4 tunneling driver\n");
1255
1256         if (inet_add_protocol(&ipgre_protocol, IPPROTO_GRE) < 0) {
1257                 printk(KERN_INFO "ipgre init: can't add protocol\n");
1258                 return -EAGAIN;
1259         }
1260
1261         ipgre_fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "gre0",
1262                                            ipgre_tunnel_setup);
1263         if (!ipgre_fb_tunnel_dev) {
1264                 err = -ENOMEM;
1265                 goto err1;
1266         }
1267
1268         ipgre_fb_tunnel_dev->init = ipgre_fb_tunnel_init;
1269
1270         if ((err = register_netdev(ipgre_fb_tunnel_dev)))
1271                 goto err2;
1272 out:
1273         return err;
1274 err2:
1275         free_netdev(ipgre_fb_tunnel_dev);
1276 err1:
1277         inet_del_protocol(&ipgre_protocol, IPPROTO_GRE);
1278         goto out;
1279 }
1280
1281 static void __exit ipgre_destroy_tunnels(void)
1282 {
1283         int prio;
1284
1285         for (prio = 0; prio < 4; prio++) {
1286                 int h;
1287                 for (h = 0; h < HASH_SIZE; h++) {
1288                         struct ip_tunnel *t;
1289                         while ((t = tunnels[prio][h]) != NULL)
1290                                 unregister_netdevice(t->dev);
1291                 }
1292         }
1293 }
1294
1295 static void __exit ipgre_fini(void)
1296 {
1297         if (inet_del_protocol(&ipgre_protocol, IPPROTO_GRE) < 0)
1298                 printk(KERN_INFO "ipgre close: can't remove protocol\n");
1299
1300         rtnl_lock();
1301         ipgre_destroy_tunnels();
1302         rtnl_unlock();
1303 }
1304
1305 module_init(ipgre_init);
1306 module_exit(ipgre_fini);
1307 MODULE_LICENSE("GPL");