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   1 /*
   2  *      IPv6 over IPv4 tunnel device - Simple Internet Transition (SIT)
   3  *      Linux INET6 implementation
   4  *
   5  *      Authors:
   6  *      Pedro Roque             <roque@di.fc.ul.pt>
   7  *      Alexey Kuznetsov        <kuznet@ms2.inr.ac.ru>
   8  *
   9  *      $Id: sit.c,v 1.53 2001/09/25 05:09:53 davem Exp $
  10  *
  11  *      This program is free software; you can redistribute it and/or
  12  *      modify it under the terms of the GNU General Public License
  13  *      as published by the Free Software Foundation; either version
  14  *      2 of the License, or (at your option) any later version.
  15  *
  16  *      Changes:
  17  * Roger Venning <r.venning@telstra.com>:       6to4 support
  18  * Nate Thompson <nate@thebog.net>:             6to4 support
  19  * Fred Templin <fred.l.templin@boeing.com>:    isatap support
  20  */
  21
  22 #include <linux/module.h>
  23 #include <linux/capability.h>
  24 #include <linux/errno.h>
  25 #include <linux/types.h>
  26 #include <linux/socket.h>
  27 #include <linux/sockios.h>
  28 #include <linux/net.h>
  29 #include <linux/in6.h>
  30 #include <linux/netdevice.h>
  31 #include <linux/if_arp.h>
  32 #include <linux/icmp.h>
  33 #include <asm/uaccess.h>
  34 #include <linux/init.h>
  35 #include <linux/netfilter_ipv4.h>
  36 #include <linux/if_ether.h>
  37
  38 #include <net/sock.h>
  39 #include <net/snmp.h>
  40
  41 #include <net/ipv6.h>
  42 #include <net/protocol.h>
  43 #include <net/transp_v6.h>
  44 #include <net/ip6_fib.h>
  45 #include <net/ip6_route.h>
  46 #include <net/ndisc.h>
  47 #include <net/addrconf.h>
  48 #include <net/ip.h>
  49 #include <net/udp.h>
  50 #include <net/icmp.h>
  51 #include <net/ipip.h>
  52 #include <net/inet_ecn.h>
  53 #include <net/xfrm.h>
  54 #include <net/dsfield.h>
  55 #include <net/net_namespace.h>
  56 #include <net/netns/generic.h>
  57
  58 /*
  59    This version of net/ipv6/sit.c is cloned of net/ipv4/ip_gre.c
  60
  61    For comments look at net/ipv4/ip_gre.c --ANK
  62  */
  63
  64 #define HASH_SIZE  16
  65 #define HASH(addr) (((__force u32)addr^((__force u32)addr>>4))&0xF)
  66
  67 static int ipip6_fb_tunnel_init(struct net_device *dev);
  68 static int ipip6_tunnel_init(struct net_device *dev);
  69 static void ipip6_tunnel_setup(struct net_device *dev);
  70
  71 static int sit_net_id;
  72 struct sit_net {
  73         struct ip_tunnel *tunnels_r_l[HASH_SIZE];
  74         struct ip_tunnel *tunnels_r[HASH_SIZE];
  75         struct ip_tunnel *tunnels_l[HASH_SIZE];
  76         struct ip_tunnel *tunnels_wc[1];
  77         struct ip_tunnel **tunnels[4];
  78
  79         struct net_device *fb_tunnel_dev;
  80 };
  81
  82 static DEFINE_RWLOCK(ipip6_lock);
  83
  84 static struct ip_tunnel * ipip6_tunnel_lookup(struct net *net,
  85                 __be32 remote, __be32 local)
  86 {
  87         unsigned h0 = HASH(remote);
  88         unsigned h1 = HASH(local);
  89         struct ip_tunnel *t;
  90         struct sit_net *sitn = net_generic(net, sit_net_id);
  91
  92         for (t = sitn->tunnels_r_l[h0^h1]; t; t = t->next) {
  93                 if (local == t->parms.iph.saddr &&
  94                     remote == t->parms.iph.daddr && (t->dev->flags&IFF_UP))
  95                         return t;
  96         }
  97         for (t = sitn->tunnels_r[h0]; t; t = t->next) {
  98                 if (remote == t->parms.iph.daddr && (t->dev->flags&IFF_UP))
  99                         return t;
 100         }
 101         for (t = sitn->tunnels_l[h1]; t; t = t->next) {
 102                 if (local == t->parms.iph.saddr && (t->dev->flags&IFF_UP))
 103                         return t;
 104         }
 105         if ((t = sitn->tunnels_wc[0]) != NULL && (t->dev->flags&IFF_UP))
 106                 return t;
 107         return NULL;
 108 }
 109
 110 static struct ip_tunnel **__ipip6_bucket(struct sit_net *sitn,
 111                 struct ip_tunnel_parm *parms)
 112 {
 113         __be32 remote = parms->iph.daddr;
 114         __be32 local = parms->iph.saddr;
 115         unsigned h = 0;
 116         int prio = 0;
 117
 118         if (remote) {
 119                 prio |= 2;
 120                 h ^= HASH(remote);
 121         }
 122         if (local) {
 123                 prio |= 1;
 124                 h ^= HASH(local);
 125         }
 126         return &sitn->tunnels[prio][h];
 127 }
 128
 129 static inline struct ip_tunnel **ipip6_bucket(struct sit_net *sitn,
 130                 struct ip_tunnel *t)
 131 {
 132         return __ipip6_bucket(sitn, &t->parms);
 133 }
 134
 135 static void ipip6_tunnel_unlink(struct sit_net *sitn, struct ip_tunnel *t)
 136 {
 137         struct ip_tunnel **tp;
 138
 139         for (tp = ipip6_bucket(sitn, t); *tp; tp = &(*tp)->next) {
 140                 if (t == *tp) {
 141                         write_lock_bh(&ipip6_lock);
 142                         *tp = t->next;
 143                         write_unlock_bh(&ipip6_lock);
 144                         break;
 145                 }
 146         }
 147 }
 148
 149 static void ipip6_tunnel_link(struct sit_net *sitn, struct ip_tunnel *t)
 150 {
 151         struct ip_tunnel **tp = ipip6_bucket(sitn, t);
 152
 153         t->next = *tp;
 154         write_lock_bh(&ipip6_lock);
 155         *tp = t;
 156         write_unlock_bh(&ipip6_lock);
 157 }
 158
 159 static struct ip_tunnel * ipip6_tunnel_locate(struct net *net,
 160                 struct ip_tunnel_parm *parms, int create)
 161 {
 162         __be32 remote = parms->iph.daddr;
 163         __be32 local = parms->iph.saddr;
 164         struct ip_tunnel *t, **tp, *nt;
 165         struct net_device *dev;
 166         char name[IFNAMSIZ];
 167         struct sit_net *sitn = net_generic(net, sit_net_id);
 168
 169         for (tp = __ipip6_bucket(sitn, parms); (t = *tp) != NULL; tp = &t->next) {
 170                 if (local == t->parms.iph.saddr && remote == t->parms.iph.daddr)
 171                         return t;
 172         }
 173         if (!create)
 174                 goto failed;
 175
 176         if (parms->name[0])
 177                 strlcpy(name, parms->name, IFNAMSIZ);
 178         else
 179                 sprintf(name, "sit%%d");
 180
 181         dev = alloc_netdev(sizeof(*t), name, ipip6_tunnel_setup);
 182         if (dev == NULL)
 183                 return NULL;
 184
 185         dev_net_set(dev, net);
 186
 187         if (strchr(name, '%')) {
 188                 if (dev_alloc_name(dev, name) < 0)
 189                         goto failed_free;
 190         }
 191
 192         nt = netdev_priv(dev);
 193         dev->init = ipip6_tunnel_init;
 194         nt->parms = *parms;
 195
 196         if (parms->i_flags & SIT_ISATAP)
 197                 dev->priv_flags |= IFF_ISATAP;
 198
 199         if (register_netdevice(dev) < 0)
 200                 goto failed_free;
 201
 202         dev_hold(dev);
 203
 204         ipip6_tunnel_link(sitn, nt);
 205         return nt;
 206
 207 failed_free:
 208         free_netdev(dev);
 209 failed:
 210         return NULL;
 211 }
 212
 213 static struct ip_tunnel_prl_entry *
 214 __ipip6_tunnel_locate_prl(struct ip_tunnel *t, __be32 addr)
 215 {
 216         struct ip_tunnel_prl_entry *p = (struct ip_tunnel_prl_entry *)NULL;
 217
 218         for (p = t->prl; p; p = p->next)
 219                 if (p->addr == addr)
 220                         break;
 221         return p;
 222
 223 }
 224
 225 static int ipip6_tunnel_get_prl(struct ip_tunnel *t,
 226                                 struct ip_tunnel_prl __user *a)
 227 {
 228         struct ip_tunnel_prl kprl, *kp;
 229         struct ip_tunnel_prl_entry *prl;
 230         unsigned int cmax, c = 0, ca, len;
 231         int ret = 0;
 232
 233         if (copy_from_user(&kprl, a, sizeof(kprl)))
 234                 return -EFAULT;
 235         cmax = kprl.datalen / sizeof(kprl);
 236         if (cmax > 1 && kprl.addr != htonl(INADDR_ANY))
 237                 cmax = 1;
 238
 239         /* For simple GET or for root users,
 240          * we try harder to allocate.
 241          */
 242         kp = (cmax <= 1 || capable(CAP_NET_ADMIN)) ?
 243                 kcalloc(cmax, sizeof(*kp), GFP_KERNEL) :
 244                 NULL;
 245
 246         read_lock(&ipip6_lock);
 247
 248         ca = t->prl_count < cmax ? t->prl_count : cmax;
 249
 250         if (!kp) {
 251                 /* We don't try hard to allocate much memory for
 252                  * non-root users.
 253                  * For root users, retry allocating enough memory for
 254                  * the answer.
 255                  */
 256                 kp = kcalloc(ca, sizeof(*kp), GFP_ATOMIC);
 257                 if (!kp) {
 258                         ret = -ENOMEM;
 259                         goto out;
 260                 }
 261         }
 262
 263         c = 0;
 264         for (prl = t->prl; prl; prl = prl->next) {
 265                 if (c > cmax)
 266                         break;
 267                 if (kprl.addr != htonl(INADDR_ANY) && prl->addr != kprl.addr)
 268                         continue;
 269                 kp[c].addr = prl->addr;
 270                 kp[c].flags = prl->flags;
 271                 c++;
 272                 if (kprl.addr != htonl(INADDR_ANY))
 273                         break;
 274         }
 275 out:
 276         read_unlock(&ipip6_lock);
 277
 278         len = sizeof(*kp) * c;
 279         ret = 0;
 280         if ((len && copy_to_user(a + 1, kp, len)) || put_user(len, &a->datalen))
 281                 ret = -EFAULT;
 282
 283         kfree(kp);
 284
 285         return ret;
 286 }
 287
 288 static int
 289 ipip6_tunnel_add_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a, int chg)
 290 {
 291         struct ip_tunnel_prl_entry *p;
 292         int err = 0;
 293
 294         if (a->addr == htonl(INADDR_ANY))
 295                 return -EINVAL;
 296
 297         write_lock(&ipip6_lock);
 298
 299         for (p = t->prl; p; p = p->next) {
 300                 if (p->addr == a->addr) {
 301                         if (chg)
 302                                 goto update;
 303                         err = -EEXIST;
 304                         goto out;
 305                 }
 306         }
 307
 308         if (chg) {
 309                 err = -ENXIO;
 310                 goto out;
 311         }
 312
 313         p = kzalloc(sizeof(struct ip_tunnel_prl_entry), GFP_KERNEL);
 314         if (!p) {
 315                 err = -ENOBUFS;
 316                 goto out;
 317         }
 318
 319         p->next = t->prl;
 320         t->prl = p;
 321         t->prl_count++;
 322 update:
 323         p->addr = a->addr;
 324         p->flags = a->flags;
 325 out:
 326         write_unlock(&ipip6_lock);
 327         return err;
 328 }
 329
 330 static int
 331 ipip6_tunnel_del_prl(struct ip_tunnel *t, struct ip_tunnel_prl *a)
 332 {
 333         struct ip_tunnel_prl_entry *x, **p;
 334         int err = 0;
 335
 336         write_lock(&ipip6_lock);
 337
 338         if (a && a->addr != htonl(INADDR_ANY)) {
 339                 for (p = &t->prl; *p; p = &(*p)->next) {
 340                         if ((*p)->addr == a->addr) {
 341                                 x = *p;
 342                                 *p = x->next;
 343                                 kfree(x);
 344                                 t->prl_count--;
 345                                 goto out;
 346                         }
 347                 }
 348                 err = -ENXIO;
 349         } else {
 350                 while (t->prl) {
 351                         x = t->prl;
 352                         t->prl = t->prl->next;
 353                         kfree(x);
 354                         t->prl_count--;
 355                 }
 356         }
 357 out:
 358         write_unlock(&ipip6_lock);
 359         return 0;
 360 }
 361
 362 static int
 363 isatap_chksrc(struct sk_buff *skb, struct iphdr *iph, struct ip_tunnel *t)
 364 {
 365         struct ip_tunnel_prl_entry *p;
 366         int ok = 1;
 367
 368         read_lock(&ipip6_lock);
 369         p = __ipip6_tunnel_locate_prl(t, iph->saddr);
 370         if (p) {
 371                 if (p->flags & PRL_DEFAULT)
 372                         skb->ndisc_nodetype = NDISC_NODETYPE_DEFAULT;
 373                 else
 374                         skb->ndisc_nodetype = NDISC_NODETYPE_NODEFAULT;
 375         } else {
 376                 struct in6_addr *addr6 = &ipv6_hdr(skb)->saddr;
 377                 if (ipv6_addr_is_isatap(addr6) &&
 378                     (addr6->s6_addr32[3] == iph->saddr) &&
 379                     ipv6_chk_prefix(addr6, t->dev))
 380                         skb->ndisc_nodetype = NDISC_NODETYPE_HOST;
 381                 else
 382                         ok = 0;
 383         }
 384         read_unlock(&ipip6_lock);
 385         return ok;
 386 }
 387
 388 static void ipip6_tunnel_uninit(struct net_device *dev)
 389 {
 390         struct net *net = dev_net(dev);
 391         struct sit_net *sitn = net_generic(net, sit_net_id);
 392
 393         if (dev == sitn->fb_tunnel_dev) {
 394                 write_lock_bh(&ipip6_lock);
 395                 sitn->tunnels_wc[0] = NULL;
 396                 write_unlock_bh(&ipip6_lock);
 397                 dev_put(dev);
 398         } else {
 399                 ipip6_tunnel_unlink(sitn, netdev_priv(dev));
 400                 ipip6_tunnel_del_prl(netdev_priv(dev), NULL);
 401                 dev_put(dev);
 402         }
 403 }
 404
 405
 406 static int ipip6_err(struct sk_buff *skb, u32 info)
 407 {
 408
 409 /* All the routers (except for Linux) return only
 410    8 bytes of packet payload. It means, that precise relaying of
 411    ICMP in the real Internet is absolutely infeasible.
 412  */
 413         struct iphdr *iph = (struct iphdr*)skb->data;
 414         const int type = icmp_hdr(skb)->type;
 415         const int code = icmp_hdr(skb)->code;
 416         struct ip_tunnel *t;
 417         int err;
 418
 419         switch (type) {
 420         default:
 421         case ICMP_PARAMETERPROB:
 422                 return 0;
 423
 424         case ICMP_DEST_UNREACH:
 425                 switch (code) {
 426                 case ICMP_SR_FAILED:
 427                 case ICMP_PORT_UNREACH:
 428                         /* Impossible event. */
 429                         return 0;
 430                 case ICMP_FRAG_NEEDED:
 431                         /* Soft state for pmtu is maintained by IP core. */
 432                         return 0;
 433                 default:
 434                         /* All others are translated to HOST_UNREACH.
 435                            rfc2003 contains "deep thoughts" about NET_UNREACH,
 436                            I believe they are just ether pollution. --ANK
 437                          */
 438                         break;
 439                 }
 440                 break;
 441         case ICMP_TIME_EXCEEDED:
 442                 if (code != ICMP_EXC_TTL)
 443                         return 0;
 444                 break;
 445         }
 446
 447         err = -ENOENT;
 448
 449         read_lock(&ipip6_lock);
 450         t = ipip6_tunnel_lookup(dev_net(skb->dev), iph->daddr, iph->saddr);
 451         if (t == NULL || t->parms.iph.daddr == 0)
 452                 goto out;
 453
 454         err = 0;
 455         if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)
 456                 goto out;
 457
 458         if (jiffies - t->err_time < IPTUNNEL_ERR_TIMEO)
 459                 t->err_count++;
 460         else
 461                 t->err_count = 1;
 462         t->err_time = jiffies;
 463 out:
 464         read_unlock(&ipip6_lock);
 465         return err;
 466 }
 467
 468 static inline void ipip6_ecn_decapsulate(struct iphdr *iph, struct sk_buff *skb)
 469 {
 470         if (INET_ECN_is_ce(iph->tos))
 471                 IP6_ECN_set_ce(ipv6_hdr(skb));
 472 }
 473
 474 static int ipip6_rcv(struct sk_buff *skb)
 475 {
 476         struct iphdr *iph;
 477         struct ip_tunnel *tunnel;
 478
 479         if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
 480                 goto out;
 481
 482         iph = ip_hdr(skb);
 483
 484         read_lock(&ipip6_lock);
 485         if ((tunnel = ipip6_tunnel_lookup(dev_net(skb->dev),
 486                                         iph->saddr, iph->daddr)) != NULL) {
 487                 secpath_reset(skb);
 488                 skb->mac_header = skb->network_header;
 489                 skb_reset_network_header(skb);
 490                 IPCB(skb)->flags = 0;
 491                 skb->protocol = htons(ETH_P_IPV6);
 492                 skb->pkt_type = PACKET_HOST;
 493
 494                 if ((tunnel->dev->priv_flags & IFF_ISATAP) &&
 495                     !isatap_chksrc(skb, iph, tunnel)) {
 496                         tunnel->stat.rx_errors++;
 497                         read_unlock(&ipip6_lock);
 498                         kfree_skb(skb);
 499                         return 0;
 500                 }
 501                 tunnel->stat.rx_packets++;
 502                 tunnel->stat.rx_bytes += skb->len;
 503                 skb->dev = tunnel->dev;
 504                 dst_release(skb->dst);
 505                 skb->dst = NULL;
 506                 nf_reset(skb);
 507                 ipip6_ecn_decapsulate(iph, skb);
 508                 netif_rx(skb);
 509                 read_unlock(&ipip6_lock);
 510                 return 0;
 511         }
 512
 513         icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
 514         read_unlock(&ipip6_lock);
 515 out:
 516         kfree_skb(skb);
 517         return 0;
 518 }
 519
 520 /* Returns the embedded IPv4 address if the IPv6 address
 521    comes from 6to4 (RFC 3056) addr space */
 522
 523 static inline __be32 try_6to4(struct in6_addr *v6dst)
 524 {
 525         __be32 dst = 0;
 526
 527         if (v6dst->s6_addr16[0] == htons(0x2002)) {
 528                 /* 6to4 v6 addr has 16 bits prefix, 32 v4addr, 16 SLA, ... */
 529                 memcpy(&dst, &v6dst->s6_addr16[1], 4);
 530         }
 531         return dst;
 532 }
 533
 534 /*
 535  *      This function assumes it is being called from dev_queue_xmit()
 536  *      and that skb is filled properly by that function.
 537  */
 538
 539 static int ipip6_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 540 {
 541         struct ip_tunnel *tunnel = netdev_priv(dev);
 542         struct net_device_stats *stats = &tunnel->stat;
 543         struct iphdr  *tiph = &tunnel->parms.iph;
 544         struct ipv6hdr *iph6 = ipv6_hdr(skb);
 545         u8     tos = tunnel->parms.iph.tos;
 546         struct rtable *rt;                      /* Route to the other host */
 547         struct net_device *tdev;                        /* Device to other host */
 548         struct iphdr  *iph;                     /* Our new IP header */
 549         unsigned int max_headroom;              /* The extra header space needed */
 550         __be32 dst = tiph->daddr;
 551         int    mtu;
 552         struct in6_addr *addr6;
 553         int addr_type;
 554
 555         if (tunnel->recursion++) {
 556                 tunnel->stat.collisions++;
 557                 goto tx_error;
 558         }
 559
 560         if (skb->protocol != htons(ETH_P_IPV6))
 561                 goto tx_error;
 562
 563         /* ISATAP (RFC4214) - must come before 6to4 */
 564         if (dev->priv_flags & IFF_ISATAP) {
 565                 struct neighbour *neigh = NULL;
 566
 567                 if (skb->dst)
 568                         neigh = skb->dst->neighbour;
 569
 570                 if (neigh == NULL) {
 571                         if (net_ratelimit())
 572                                 printk(KERN_DEBUG "sit: nexthop == NULL\n");
 573                         goto tx_error;
 574                 }
 575
 576                 addr6 = (struct in6_addr*)&neigh->primary_key;
 577                 addr_type = ipv6_addr_type(addr6);
 578
 579                 if ((addr_type & IPV6_ADDR_UNICAST) &&
 580                      ipv6_addr_is_isatap(addr6))
 581                         dst = addr6->s6_addr32[3];
 582                 else
 583                         goto tx_error;
 584         }
 585
 586         if (!dst)
 587                 dst = try_6to4(&iph6->daddr);
 588
 589         if (!dst) {
 590                 struct neighbour *neigh = NULL;
 591
 592                 if (skb->dst)
 593                         neigh = skb->dst->neighbour;
 594
 595                 if (neigh == NULL) {
 596                         if (net_ratelimit())
 597                                 printk(KERN_DEBUG "sit: nexthop == NULL\n");
 598                         goto tx_error;
 599                 }
 600
 601                 addr6 = (struct in6_addr*)&neigh->primary_key;
 602                 addr_type = ipv6_addr_type(addr6);
 603
 604                 if (addr_type == IPV6_ADDR_ANY) {
 605                         addr6 = &ipv6_hdr(skb)->daddr;
 606                         addr_type = ipv6_addr_type(addr6);
 607                 }
 608
 609                 if ((addr_type & IPV6_ADDR_COMPATv4) == 0)
 610                         goto tx_error_icmp;
 611
 612                 dst = addr6->s6_addr32[3];
 613         }
 614
 615         {
 616                 struct flowi fl = { .nl_u = { .ip4_u =
 617                                               { .daddr = dst,
 618                                                 .saddr = tiph->saddr,
 619                                                 .tos = RT_TOS(tos) } },
 620                                     .oif = tunnel->parms.link,
 621                                     .proto = IPPROTO_IPV6 };
 622                 if (ip_route_output_key(dev_net(dev), &rt, &fl)) {
 623                         tunnel->stat.tx_carrier_errors++;
 624                         goto tx_error_icmp;
 625                 }
 626         }
 627         if (rt->rt_type != RTN_UNICAST) {
 628                 ip_rt_put(rt);
 629                 tunnel->stat.tx_carrier_errors++;
 630                 goto tx_error_icmp;
 631         }
 632         tdev = rt->u.dst.dev;
 633
 634         if (tdev == dev) {
 635                 ip_rt_put(rt);
 636                 tunnel->stat.collisions++;
 637                 goto tx_error;
 638         }
 639
 640         if (tiph->frag_off)
 641                 mtu = dst_mtu(&rt->u.dst) - sizeof(struct iphdr);
 642         else
 643                 mtu = skb->dst ? dst_mtu(skb->dst) : dev->mtu;
 644
 645         if (mtu < 68) {
 646                 tunnel->stat.collisions++;
 647                 ip_rt_put(rt);
 648                 goto tx_error;
 649         }
 650         if (mtu < IPV6_MIN_MTU)
 651                 mtu = IPV6_MIN_MTU;
 652         if (tunnel->parms.iph.daddr && skb->dst)
 653                 skb->dst->ops->update_pmtu(skb->dst, mtu);
 654
 655         if (skb->len > mtu) {
 656                 icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, dev);
 657                 ip_rt_put(rt);
 658                 goto tx_error;
 659         }
 660
 661         if (tunnel->err_count > 0) {
 662                 if (jiffies - tunnel->err_time < IPTUNNEL_ERR_TIMEO) {
 663                         tunnel->err_count--;
 664                         dst_link_failure(skb);
 665                 } else
 666                         tunnel->err_count = 0;
 667         }
 668
 669         /*
 670          * Okay, now see if we can stuff it in the buffer as-is.
 671          */
 672         max_headroom = LL_RESERVED_SPACE(tdev)+sizeof(struct iphdr);
 673
 674         if (skb_headroom(skb) < max_headroom || skb_shared(skb) ||
 675             (skb_cloned(skb) && !skb_clone_writable(skb, 0))) {
 676                 struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
 677                 if (!new_skb) {
 678                         ip_rt_put(rt);
 679                         stats->tx_dropped++;
 680                         dev_kfree_skb(skb);
 681                         tunnel->recursion--;
 682                         return 0;
 683                 }
 684                 if (skb->sk)
 685                         skb_set_owner_w(new_skb, skb->sk);
 686                 dev_kfree_skb(skb);
 687                 skb = new_skb;
 688                 iph6 = ipv6_hdr(skb);
 689         }
 690
 691         skb->transport_header = skb->network_header;
 692         skb_push(skb, sizeof(struct iphdr));
 693         skb_reset_network_header(skb);
 694         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 695         IPCB(skb)->flags = 0;
 696         dst_release(skb->dst);
 697         skb->dst = &rt->u.dst;
 698
 699         /*
 700          *      Push down and install the IPIP header.
 701          */
 702
 703         iph                     =       ip_hdr(skb);
 704         iph->version            =       4;
 705         iph->ihl                =       sizeof(struct iphdr)>>2;
 706         if (mtu > IPV6_MIN_MTU)
 707                 iph->frag_off   =       htons(IP_DF);
 708         else
 709                 iph->frag_off   =       0;
 710
 711         iph->protocol           =       IPPROTO_IPV6;
 712         iph->tos                =       INET_ECN_encapsulate(tos, ipv6_get_dsfield(iph6));
 713         iph->daddr              =       rt->rt_dst;
 714         iph->saddr              =       rt->rt_src;
 715
 716         if ((iph->ttl = tiph->ttl) == 0)
 717                 iph->ttl        =       iph6->hop_limit;
 718
 719         nf_reset(skb);
 720
 721         IPTUNNEL_XMIT();
 722         tunnel->recursion--;
 723         return 0;
 724
 725 tx_error_icmp:
 726         dst_link_failure(skb);
 727 tx_error:
 728         stats->tx_errors++;
 729         dev_kfree_skb(skb);
 730         tunnel->recursion--;
 731         return 0;
 732 }
 733
 734 static void ipip6_tunnel_bind_dev(struct net_device *dev)
 735 {
 736         struct net_device *tdev = NULL;
 737         struct ip_tunnel *tunnel;
 738         struct iphdr *iph;
 739
 740         tunnel = netdev_priv(dev);
 741         iph = &tunnel->parms.iph;
 742
 743         if (iph->daddr) {
 744                 struct flowi fl = { .nl_u = { .ip4_u =
 745                                               { .daddr = iph->daddr,
 746                                                 .saddr = iph->saddr,
 747                                                 .tos = RT_TOS(iph->tos) } },
 748                                     .oif = tunnel->parms.link,
 749                                     .proto = IPPROTO_IPV6 };
 750                 struct rtable *rt;
 751                 if (!ip_route_output_key(dev_net(dev), &rt, &fl)) {
 752                         tdev = rt->u.dst.dev;
 753                         ip_rt_put(rt);
 754                 }
 755                 dev->flags |= IFF_POINTOPOINT;
 756         }
 757
 758         if (!tdev && tunnel->parms.link)
 759                 tdev = __dev_get_by_index(dev_net(dev), tunnel->parms.link);
 760
 761         if (tdev) {
 762                 dev->hard_header_len = tdev->hard_header_len + sizeof(struct iphdr);
 763                 dev->mtu = tdev->mtu - sizeof(struct iphdr);
 764                 if (dev->mtu < IPV6_MIN_MTU)
 765                         dev->mtu = IPV6_MIN_MTU;
 766         }
 767         dev->iflink = tunnel->parms.link;
 768 }
 769
 770 static int
 771 ipip6_tunnel_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd)
 772 {
 773         int err = 0;
 774         struct ip_tunnel_parm p;
 775         struct ip_tunnel_prl prl;
 776         struct ip_tunnel *t;
 777         struct net *net = dev_net(dev);
 778         struct sit_net *sitn = net_generic(net, sit_net_id);
 779
 780         switch (cmd) {
 781         case SIOCGETTUNNEL:
 782                 t = NULL;
 783                 if (dev == sitn->fb_tunnel_dev) {
 784                         if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) {
 785                                 err = -EFAULT;
 786                                 break;
 787                         }
 788                         t = ipip6_tunnel_locate(net, &p, 0);
 789                 }
 790                 if (t == NULL)
 791                         t = netdev_priv(dev);
 792                 memcpy(&p, &t->parms, sizeof(p));
 793                 if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
 794                         err = -EFAULT;
 795                 break;
 796
 797         case SIOCADDTUNNEL:
 798         case SIOCCHGTUNNEL:
 799                 err = -EPERM;
 800                 if (!capable(CAP_NET_ADMIN))
 801                         goto done;
 802
 803                 err = -EFAULT;
 804                 if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
 805                         goto done;
 806
 807                 err = -EINVAL;
 808                 if (p.iph.version != 4 || p.iph.protocol != IPPROTO_IPV6 ||
 809                     p.iph.ihl != 5 || (p.iph.frag_off&htons(~IP_DF)))
 810                         goto done;
 811                 if (p.iph.ttl)
 812                         p.iph.frag_off |= htons(IP_DF);
 813
 814                 t = ipip6_tunnel_locate(net, &p, cmd == SIOCADDTUNNEL);
 815
 816                 if (dev != sitn->fb_tunnel_dev && cmd == SIOCCHGTUNNEL) {
 817                         if (t != NULL) {
 818                                 if (t->dev != dev) {
 819                                         err = -EEXIST;
 820                                         break;
 821                                 }
 822                         } else {
 823                                 if (((dev->flags&IFF_POINTOPOINT) && !p.iph.daddr) ||
 824                                     (!(dev->flags&IFF_POINTOPOINT) && p.iph.daddr)) {
 825                                         err = -EINVAL;
 826                                         break;
 827                                 }
 828                                 t = netdev_priv(dev);
 829                                 ipip6_tunnel_unlink(sitn, t);
 830                                 t->parms.iph.saddr = p.iph.saddr;
 831                                 t->parms.iph.daddr = p.iph.daddr;
 832                                 memcpy(dev->dev_addr, &p.iph.saddr, 4);
 833                                 memcpy(dev->broadcast, &p.iph.daddr, 4);
 834                                 ipip6_tunnel_link(sitn, t);
 835                                 netdev_state_change(dev);
 836                         }
 837                 }
 838
 839                 if (t) {
 840                         err = 0;
 841                         if (cmd == SIOCCHGTUNNEL) {
 842                                 t->parms.iph.ttl = p.iph.ttl;
 843                                 t->parms.iph.tos = p.iph.tos;
 844                                 if (t->parms.link != p.link) {
 845                                         t->parms.link = p.link;
 846                                         ipip6_tunnel_bind_dev(dev);
 847                                         netdev_state_change(dev);
 848                                 }
 849                         }
 850                         if (copy_to_user(ifr->ifr_ifru.ifru_data, &t->parms, sizeof(p)))
 851                                 err = -EFAULT;
 852                 } else
 853                         err = (cmd == SIOCADDTUNNEL ? -ENOBUFS : -ENOENT);
 854                 break;
 855
 856         case SIOCDELTUNNEL:
 857                 err = -EPERM;
 858                 if (!capable(CAP_NET_ADMIN))
 859                         goto done;
 860
 861                 if (dev == sitn->fb_tunnel_dev) {
 862                         err = -EFAULT;
 863                         if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
 864                                 goto done;
 865                         err = -ENOENT;
 866                         if ((t = ipip6_tunnel_locate(net, &p, 0)) == NULL)
 867                                 goto done;
 868                         err = -EPERM;
 869                         if (t == netdev_priv(sitn->fb_tunnel_dev))
 870                                 goto done;
 871                         dev = t->dev;
 872                 }
 873                 unregister_netdevice(dev);
 874                 err = 0;
 875                 break;
 876
 877         case SIOCGETPRL:
 878                 err = -EINVAL;
 879                 if (dev == sitn->fb_tunnel_dev)
 880                         goto done;
 881                 err = -ENOENT;
 882                 if (!(t = netdev_priv(dev)))
 883                         goto done;
 884                 err = ipip6_tunnel_get_prl(t, ifr->ifr_ifru.ifru_data);
 885                 break;
 886
 887         case SIOCADDPRL:
 888         case SIOCDELPRL:
 889         case SIOCCHGPRL:
 890                 err = -EPERM;
 891                 if (!capable(CAP_NET_ADMIN))
 892                         goto done;
 893                 err = -EINVAL;
 894                 if (dev == sitn->fb_tunnel_dev)
 895                         goto done;
 896                 err = -EFAULT;
 897                 if (copy_from_user(&prl, ifr->ifr_ifru.ifru_data, sizeof(prl)))
 898                         goto done;
 899                 err = -ENOENT;
 900                 if (!(t = netdev_priv(dev)))
 901                         goto done;
 902
 903                 switch (cmd) {
 904                 case SIOCDELPRL:
 905                         err = ipip6_tunnel_del_prl(t, &prl);
 906                         break;
 907                 case SIOCADDPRL:
 908                 case SIOCCHGPRL:
 909                         err = ipip6_tunnel_add_prl(t, &prl, cmd == SIOCCHGPRL);
 910                         break;
 911                 }
 912                 netdev_state_change(dev);
 913                 break;
 914
 915         default:
 916                 err = -EINVAL;
 917         }
 918
 919 done:
 920         return err;
 921 }
 922
 923 static struct net_device_stats *ipip6_tunnel_get_stats(struct net_device *dev)
 924 {
 925         return &(((struct ip_tunnel*)netdev_priv(dev))->stat);
 926 }
 927
 928 static int ipip6_tunnel_change_mtu(struct net_device *dev, int new_mtu)
 929 {
 930         if (new_mtu < IPV6_MIN_MTU || new_mtu > 0xFFF8 - sizeof(struct iphdr))
 931                 return -EINVAL;
 932         dev->mtu = new_mtu;
 933         return 0;
 934 }
 935
 936 static void ipip6_tunnel_setup(struct net_device *dev)
 937 {
 938         dev->uninit             = ipip6_tunnel_uninit;
 939         dev->destructor         = free_netdev;
 940         dev->hard_start_xmit    = ipip6_tunnel_xmit;
 941         dev->get_stats          = ipip6_tunnel_get_stats;
 942         dev->do_ioctl           = ipip6_tunnel_ioctl;
 943         dev->change_mtu         = ipip6_tunnel_change_mtu;
 944
 945         dev->type               = ARPHRD_SIT;
 946         dev->hard_header_len    = LL_MAX_HEADER + sizeof(struct iphdr);
 947         dev->mtu                = ETH_DATA_LEN - sizeof(struct iphdr);
 948         dev->flags              = IFF_NOARP;
 949         dev->iflink             = 0;
 950         dev->addr_len           = 4;
 951         dev->features           |= NETIF_F_NETNS_LOCAL;
 952 }
 953
 954 static int ipip6_tunnel_init(struct net_device *dev)
 955 {
 956         struct ip_tunnel *tunnel;
 957
 958         tunnel = netdev_priv(dev);
 959
 960         tunnel->dev = dev;
 961         strcpy(tunnel->parms.name, dev->name);
 962
 963         memcpy(dev->dev_addr, &tunnel->parms.iph.saddr, 4);
 964         memcpy(dev->broadcast, &tunnel->parms.iph.daddr, 4);
 965
 966         ipip6_tunnel_bind_dev(dev);
 967
 968         return 0;
 969 }
 970
 971 static int ipip6_fb_tunnel_init(struct net_device *dev)
 972 {
 973         struct ip_tunnel *tunnel = netdev_priv(dev);
 974         struct iphdr *iph = &tunnel->parms.iph;
 975         struct net *net = dev_net(dev);
 976         struct sit_net *sitn = net_generic(net, sit_net_id);
 977
 978         tunnel->dev = dev;
 979         strcpy(tunnel->parms.name, dev->name);
 980
 981         iph->version            = 4;
 982         iph->protocol           = IPPROTO_IPV6;
 983         iph->ihl                = 5;
 984         iph->ttl                = 64;
 985
 986         dev_hold(dev);
 987         sitn->tunnels_wc[0]     = tunnel;
 988         return 0;
 989 }
 990
 991 static struct xfrm_tunnel sit_handler = {
 992         .handler        =       ipip6_rcv,
 993         .err_handler    =       ipip6_err,
 994         .priority       =       1,
 995 };
 996
 997 static void sit_destroy_tunnels(struct sit_net *sitn)
 998 {
 999         int prio;
1000
1001         for (prio = 1; prio < 4; prio++) {
1002                 int h;
1003                 for (h = 0; h < HASH_SIZE; h++) {
1004                         struct ip_tunnel *t;
1005                         while ((t = sitn->tunnels[prio][h]) != NULL)
1006                                 unregister_netdevice(t->dev);
1007                 }
1008         }
1009 }
1010
1011 static int sit_init_net(struct net *net)
1012 {
1013         int err;
1014         struct sit_net *sitn;
1015
1016         err = -ENOMEM;
1017         sitn = kzalloc(sizeof(struct sit_net), GFP_KERNEL);
1018         if (sitn == NULL)
1019                 goto err_alloc;
1020
1021         err = net_assign_generic(net, sit_net_id, sitn);
1022         if (err < 0)
1023                 goto err_assign;
1024
1025         sitn->tunnels[0] = sitn->tunnels_wc;
1026         sitn->tunnels[1] = sitn->tunnels_l;
1027         sitn->tunnels[2] = sitn->tunnels_r;
1028         sitn->tunnels[3] = sitn->tunnels_r_l;
1029
1030         sitn->fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "sit0",
1031                                            ipip6_tunnel_setup);
1032         if (!sitn->fb_tunnel_dev) {
1033                 err = -ENOMEM;
1034                 goto err_alloc_dev;
1035         }
1036
1037         sitn->fb_tunnel_dev->init = ipip6_fb_tunnel_init;
1038         dev_net_set(sitn->fb_tunnel_dev, net);
1039
1040         if ((err = register_netdev(sitn->fb_tunnel_dev)))
1041                 goto err_reg_dev;
1042
1043         return 0;
1044
1045 err_reg_dev:
1046         free_netdev(sitn->fb_tunnel_dev);
1047 err_alloc_dev:
1048         /* nothing */
1049 err_assign:
1050         kfree(sitn);
1051 err_alloc:
1052         return err;
1053 }
1054
1055 static void sit_exit_net(struct net *net)
1056 {
1057         struct sit_net *sitn;
1058
1059         sitn = net_generic(net, sit_net_id);
1060         rtnl_lock();
1061         sit_destroy_tunnels(sitn);
1062         unregister_netdevice(sitn->fb_tunnel_dev);
1063         rtnl_unlock();
1064         kfree(sitn);
1065 }
1066
1067 static struct pernet_operations sit_net_ops = {
1068         .init = sit_init_net,
1069         .exit = sit_exit_net,
1070 };
1071
1072 static void __exit sit_cleanup(void)
1073 {
1074         xfrm4_tunnel_deregister(&sit_handler, AF_INET6);
1075
1076         unregister_pernet_gen_device(sit_net_id, &sit_net_ops);
1077 }
1078
1079 static int __init sit_init(void)
1080 {
1081         int err;
1082
1083         printk(KERN_INFO "IPv6 over IPv4 tunneling driver\n");
1084
1085         if (xfrm4_tunnel_register(&sit_handler, AF_INET6) < 0) {
1086                 printk(KERN_INFO "sit init: Can't add protocol\n");
1087                 return -EAGAIN;
1088         }
1089
1090         err = register_pernet_gen_device(&sit_net_id, &sit_net_ops);
1091         if (err < 0)
1092                 xfrm4_tunnel_deregister(&sit_handler, AF_INET6);
1093
1094         return err;
1095 }
1096
1097 module_init(sit_init);
1098 module_exit(sit_cleanup);
1099 MODULE_LICENSE("GPL");
1100 MODULE_ALIAS("sit0");