Merge with rsync://fileserver/linux
[linux-2.6] / 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/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
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) ((addr^(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(u32 remote, u32 local, u32 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 ipgre_fb_tunnel_dev->priv;
191         return NULL;
192 }
193
194 static struct ip_tunnel **ipgre_bucket(struct ip_tunnel *t)
195 {
196         u32 remote = t->parms.iph.daddr;
197         u32 local = t->parms.iph.saddr;
198         u32 key = t->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 void ipgre_tunnel_link(struct ip_tunnel *t)
213 {
214         struct ip_tunnel **tp = ipgre_bucket(t);
215
216         t->next = *tp;
217         write_lock_bh(&ipgre_lock);
218         *tp = t;
219         write_unlock_bh(&ipgre_lock);
220 }
221
222 static void ipgre_tunnel_unlink(struct ip_tunnel *t)
223 {
224         struct ip_tunnel **tp;
225
226         for (tp = ipgre_bucket(t); *tp; tp = &(*tp)->next) {
227                 if (t == *tp) {
228                         write_lock_bh(&ipgre_lock);
229                         *tp = t->next;
230                         write_unlock_bh(&ipgre_lock);
231                         break;
232                 }
233         }
234 }
235
236 static struct ip_tunnel * ipgre_tunnel_locate(struct ip_tunnel_parm *parms, int create)
237 {
238         u32 remote = parms->iph.daddr;
239         u32 local = parms->iph.saddr;
240         u32 key = parms->i_key;
241         struct ip_tunnel *t, **tp, *nt;
242         struct net_device *dev;
243         unsigned h = HASH(key);
244         int prio = 0;
245         char name[IFNAMSIZ];
246
247         if (local)
248                 prio |= 1;
249         if (remote && !MULTICAST(remote)) {
250                 prio |= 2;
251                 h ^= HASH(remote);
252         }
253         for (tp = &tunnels[prio][h]; (t = *tp) != NULL; tp = &t->next) {
254                 if (local == t->parms.iph.saddr && remote == t->parms.iph.daddr) {
255                         if (key == t->parms.i_key)
256                                 return t;
257                 }
258         }
259         if (!create)
260                 return NULL;
261
262         if (parms->name[0])
263                 strlcpy(name, parms->name, IFNAMSIZ);
264         else {
265                 int i;
266                 for (i=1; i<100; i++) {
267                         sprintf(name, "gre%d", i);
268                         if (__dev_get_by_name(name) == NULL)
269                                 break;
270                 }
271                 if (i==100)
272                         goto failed;
273         }
274
275         dev = alloc_netdev(sizeof(*t), name, ipgre_tunnel_setup);
276         if (!dev)
277           return NULL;
278
279         dev->init = ipgre_tunnel_init;
280         nt = dev->priv;
281         nt->parms = *parms;
282
283         if (register_netdevice(dev) < 0) {
284                 free_netdev(dev);
285                 goto failed;
286         }
287
288         nt = dev->priv;
289         nt->parms = *parms;
290
291         dev_hold(dev);
292         ipgre_tunnel_link(nt);
293         /* Do not decrement MOD_USE_COUNT here. */
294         return nt;
295
296 failed:
297         return NULL;
298 }
299
300 static void ipgre_tunnel_uninit(struct net_device *dev)
301 {
302         ipgre_tunnel_unlink((struct ip_tunnel*)dev->priv);
303         dev_put(dev);
304 }
305
306
307 static void ipgre_err(struct sk_buff *skb, u32 info)
308 {
309 #ifndef I_WISH_WORLD_WERE_PERFECT
310
311 /* It is not :-( All the routers (except for Linux) return only
312    8 bytes of packet payload. It means, that precise relaying of
313    ICMP in the real Internet is absolutely infeasible.
314
315    Moreover, Cisco "wise men" put GRE key to the third word
316    in GRE header. It makes impossible maintaining even soft state for keyed
317    GRE tunnels with enabled checksum. Tell them "thank you".
318
319    Well, I wonder, rfc1812 was written by Cisco employee,
320    what the hell these idiots break standrads established
321    by themself???
322  */
323
324         struct iphdr *iph = (struct iphdr*)skb->data;
325         u16          *p = (u16*)(skb->data+(iph->ihl<<2));
326         int grehlen = (iph->ihl<<2) + 4;
327         int type = skb->h.icmph->type;
328         int code = skb->h.icmph->code;
329         struct ip_tunnel *t;
330         u16 flags;
331
332         flags = p[0];
333         if (flags&(GRE_CSUM|GRE_KEY|GRE_SEQ|GRE_ROUTING|GRE_VERSION)) {
334                 if (flags&(GRE_VERSION|GRE_ROUTING))
335                         return;
336                 if (flags&GRE_KEY) {
337                         grehlen += 4;
338                         if (flags&GRE_CSUM)
339                                 grehlen += 4;
340                 }
341         }
342
343         /* If only 8 bytes returned, keyed message will be dropped here */
344         if (skb_headlen(skb) < grehlen)
345                 return;
346
347         switch (type) {
348         default:
349         case ICMP_PARAMETERPROB:
350                 return;
351
352         case ICMP_DEST_UNREACH:
353                 switch (code) {
354                 case ICMP_SR_FAILED:
355                 case ICMP_PORT_UNREACH:
356                         /* Impossible event. */
357                         return;
358                 case ICMP_FRAG_NEEDED:
359                         /* Soft state for pmtu is maintained by IP core. */
360                         return;
361                 default:
362                         /* All others are translated to HOST_UNREACH.
363                            rfc2003 contains "deep thoughts" about NET_UNREACH,
364                            I believe they are just ether pollution. --ANK
365                          */
366                         break;
367                 }
368                 break;
369         case ICMP_TIME_EXCEEDED:
370                 if (code != ICMP_EXC_TTL)
371                         return;
372                 break;
373         }
374
375         read_lock(&ipgre_lock);
376         t = ipgre_tunnel_lookup(iph->daddr, iph->saddr, (flags&GRE_KEY) ? *(((u32*)p) + (grehlen>>2) - 1) : 0);
377         if (t == NULL || t->parms.iph.daddr == 0 || MULTICAST(t->parms.iph.daddr))
378                 goto out;
379
380         if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)
381                 goto out;
382
383         if (jiffies - t->err_time < IPTUNNEL_ERR_TIMEO)
384                 t->err_count++;
385         else
386                 t->err_count = 1;
387         t->err_time = jiffies;
388 out:
389         read_unlock(&ipgre_lock);
390         return;
391 #else
392         struct iphdr *iph = (struct iphdr*)dp;
393         struct iphdr *eiph;
394         u16          *p = (u16*)(dp+(iph->ihl<<2));
395         int type = skb->h.icmph->type;
396         int code = skb->h.icmph->code;
397         int rel_type = 0;
398         int rel_code = 0;
399         int rel_info = 0;
400         u16 flags;
401         int grehlen = (iph->ihl<<2) + 4;
402         struct sk_buff *skb2;
403         struct flowi fl;
404         struct rtable *rt;
405
406         if (p[1] != htons(ETH_P_IP))
407                 return;
408
409         flags = p[0];
410         if (flags&(GRE_CSUM|GRE_KEY|GRE_SEQ|GRE_ROUTING|GRE_VERSION)) {
411                 if (flags&(GRE_VERSION|GRE_ROUTING))
412                         return;
413                 if (flags&GRE_CSUM)
414                         grehlen += 4;
415                 if (flags&GRE_KEY)
416                         grehlen += 4;
417                 if (flags&GRE_SEQ)
418                         grehlen += 4;
419         }
420         if (len < grehlen + sizeof(struct iphdr))
421                 return;
422         eiph = (struct iphdr*)(dp + grehlen);
423
424         switch (type) {
425         default:
426                 return;
427         case ICMP_PARAMETERPROB:
428                 if (skb->h.icmph->un.gateway < (iph->ihl<<2))
429                         return;
430
431                 /* So... This guy found something strange INSIDE encapsulated
432                    packet. Well, he is fool, but what can we do ?
433                  */
434                 rel_type = ICMP_PARAMETERPROB;
435                 rel_info = skb->h.icmph->un.gateway - grehlen;
436                 break;
437
438         case ICMP_DEST_UNREACH:
439                 switch (code) {
440                 case ICMP_SR_FAILED:
441                 case ICMP_PORT_UNREACH:
442                         /* Impossible event. */
443                         return;
444                 case ICMP_FRAG_NEEDED:
445                         /* And it is the only really necessary thing :-) */
446                         rel_info = ntohs(skb->h.icmph->un.frag.mtu);
447                         if (rel_info < grehlen+68)
448                                 return;
449                         rel_info -= grehlen;
450                         /* BSD 4.2 MORE DOES NOT EXIST IN NATURE. */
451                         if (rel_info > ntohs(eiph->tot_len))
452                                 return;
453                         break;
454                 default:
455                         /* All others are translated to HOST_UNREACH.
456                            rfc2003 contains "deep thoughts" about NET_UNREACH,
457                            I believe, it is just ether pollution. --ANK
458                          */
459                         rel_type = ICMP_DEST_UNREACH;
460                         rel_code = ICMP_HOST_UNREACH;
461                         break;
462                 }
463                 break;
464         case ICMP_TIME_EXCEEDED:
465                 if (code != ICMP_EXC_TTL)
466                         return;
467                 break;
468         }
469
470         /* Prepare fake skb to feed it to icmp_send */
471         skb2 = skb_clone(skb, GFP_ATOMIC);
472         if (skb2 == NULL)
473                 return;
474         dst_release(skb2->dst);
475         skb2->dst = NULL;
476         skb_pull(skb2, skb->data - (u8*)eiph);
477         skb2->nh.raw = skb2->data;
478
479         /* Try to guess incoming interface */
480         memset(&fl, 0, sizeof(fl));
481         fl.fl4_dst = eiph->saddr;
482         fl.fl4_tos = RT_TOS(eiph->tos);
483         fl.proto = IPPROTO_GRE;
484         if (ip_route_output_key(&rt, &fl)) {
485                 kfree_skb(skb2);
486                 return;
487         }
488         skb2->dev = rt->u.dst.dev;
489
490         /* route "incoming" packet */
491         if (rt->rt_flags&RTCF_LOCAL) {
492                 ip_rt_put(rt);
493                 rt = NULL;
494                 fl.fl4_dst = eiph->daddr;
495                 fl.fl4_src = eiph->saddr;
496                 fl.fl4_tos = eiph->tos;
497                 if (ip_route_output_key(&rt, &fl) ||
498                     rt->u.dst.dev->type != ARPHRD_IPGRE) {
499                         ip_rt_put(rt);
500                         kfree_skb(skb2);
501                         return;
502                 }
503         } else {
504                 ip_rt_put(rt);
505                 if (ip_route_input(skb2, eiph->daddr, eiph->saddr, eiph->tos, skb2->dev) ||
506                     skb2->dst->dev->type != ARPHRD_IPGRE) {
507                         kfree_skb(skb2);
508                         return;
509                 }
510         }
511
512         /* change mtu on this route */
513         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
514                 if (rel_info > dst_mtu(skb2->dst)) {
515                         kfree_skb(skb2);
516                         return;
517                 }
518                 skb2->dst->ops->update_pmtu(skb2->dst, rel_info);
519                 rel_info = htonl(rel_info);
520         } else if (type == ICMP_TIME_EXCEEDED) {
521                 struct ip_tunnel *t = (struct ip_tunnel*)skb2->dev->priv;
522                 if (t->parms.iph.ttl) {
523                         rel_type = ICMP_DEST_UNREACH;
524                         rel_code = ICMP_HOST_UNREACH;
525                 }
526         }
527
528         icmp_send(skb2, rel_type, rel_code, rel_info);
529         kfree_skb(skb2);
530 #endif
531 }
532
533 static inline void ipgre_ecn_decapsulate(struct iphdr *iph, struct sk_buff *skb)
534 {
535         if (INET_ECN_is_ce(iph->tos)) {
536                 if (skb->protocol == htons(ETH_P_IP)) {
537                         IP_ECN_set_ce(skb->nh.iph);
538                 } else if (skb->protocol == htons(ETH_P_IPV6)) {
539                         IP6_ECN_set_ce(skb->nh.ipv6h);
540                 }
541         }
542 }
543
544 static inline u8
545 ipgre_ecn_encapsulate(u8 tos, struct iphdr *old_iph, struct sk_buff *skb)
546 {
547         u8 inner = 0;
548         if (skb->protocol == htons(ETH_P_IP))
549                 inner = old_iph->tos;
550         else if (skb->protocol == htons(ETH_P_IPV6))
551                 inner = ipv6_get_dsfield((struct ipv6hdr *)old_iph);
552         return INET_ECN_encapsulate(tos, inner);
553 }
554
555 static int ipgre_rcv(struct sk_buff *skb)
556 {
557         struct iphdr *iph;
558         u8     *h;
559         u16    flags;
560         u16    csum = 0;
561         u32    key = 0;
562         u32    seqno = 0;
563         struct ip_tunnel *tunnel;
564         int    offset = 4;
565
566         if (!pskb_may_pull(skb, 16))
567                 goto drop_nolock;
568
569         iph = skb->nh.iph;
570         h = skb->data;
571         flags = *(u16*)h;
572
573         if (flags&(GRE_CSUM|GRE_KEY|GRE_ROUTING|GRE_SEQ|GRE_VERSION)) {
574                 /* - Version must be 0.
575                    - We do not support routing headers.
576                  */
577                 if (flags&(GRE_VERSION|GRE_ROUTING))
578                         goto drop_nolock;
579
580                 if (flags&GRE_CSUM) {
581                         if (skb->ip_summed == CHECKSUM_HW) {
582                                 csum = (u16)csum_fold(skb->csum);
583                                 if (csum)
584                                         skb->ip_summed = CHECKSUM_NONE;
585                         }
586                         if (skb->ip_summed == CHECKSUM_NONE) {
587                                 skb->csum = skb_checksum(skb, 0, skb->len, 0);
588                                 skb->ip_summed = CHECKSUM_HW;
589                                 csum = (u16)csum_fold(skb->csum);
590                         }
591                         offset += 4;
592                 }
593                 if (flags&GRE_KEY) {
594                         key = *(u32*)(h + offset);
595                         offset += 4;
596                 }
597                 if (flags&GRE_SEQ) {
598                         seqno = ntohl(*(u32*)(h + offset));
599                         offset += 4;
600                 }
601         }
602
603         read_lock(&ipgre_lock);
604         if ((tunnel = ipgre_tunnel_lookup(iph->saddr, iph->daddr, key)) != NULL) {
605                 secpath_reset(skb);
606
607                 skb->protocol = *(u16*)(h + 2);
608                 /* WCCP version 1 and 2 protocol decoding.
609                  * - Change protocol to IP
610                  * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
611                  */
612                 if (flags == 0 &&
613                     skb->protocol == __constant_htons(ETH_P_WCCP)) {
614                         skb->protocol = __constant_htons(ETH_P_IP);
615                         if ((*(h + offset) & 0xF0) != 0x40) 
616                                 offset += 4;
617                 }
618
619                 skb->mac.raw = skb->nh.raw;
620                 skb->nh.raw = __pskb_pull(skb, offset);
621                 skb_postpull_rcsum(skb, skb->mac.raw, offset);
622                 memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
623                 skb->pkt_type = PACKET_HOST;
624 #ifdef CONFIG_NET_IPGRE_BROADCAST
625                 if (MULTICAST(iph->daddr)) {
626                         /* Looped back packet, drop it! */
627                         if (((struct rtable*)skb->dst)->fl.iif == 0)
628                                 goto drop;
629                         tunnel->stat.multicast++;
630                         skb->pkt_type = PACKET_BROADCAST;
631                 }
632 #endif
633
634                 if (((flags&GRE_CSUM) && csum) ||
635                     (!(flags&GRE_CSUM) && tunnel->parms.i_flags&GRE_CSUM)) {
636                         tunnel->stat.rx_crc_errors++;
637                         tunnel->stat.rx_errors++;
638                         goto drop;
639                 }
640                 if (tunnel->parms.i_flags&GRE_SEQ) {
641                         if (!(flags&GRE_SEQ) ||
642                             (tunnel->i_seqno && (s32)(seqno - tunnel->i_seqno) < 0)) {
643                                 tunnel->stat.rx_fifo_errors++;
644                                 tunnel->stat.rx_errors++;
645                                 goto drop;
646                         }
647                         tunnel->i_seqno = seqno + 1;
648                 }
649                 tunnel->stat.rx_packets++;
650                 tunnel->stat.rx_bytes += skb->len;
651                 skb->dev = tunnel->dev;
652                 dst_release(skb->dst);
653                 skb->dst = NULL;
654                 nf_reset(skb);
655                 ipgre_ecn_decapsulate(iph, skb);
656                 netif_rx(skb);
657                 read_unlock(&ipgre_lock);
658                 return(0);
659         }
660         icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PROT_UNREACH, 0);
661
662 drop:
663         read_unlock(&ipgre_lock);
664 drop_nolock:
665         kfree_skb(skb);
666         return(0);
667 }
668
669 static int ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
670 {
671         struct ip_tunnel *tunnel = (struct ip_tunnel*)dev->priv;
672         struct net_device_stats *stats = &tunnel->stat;
673         struct iphdr  *old_iph = skb->nh.iph;
674         struct iphdr  *tiph;
675         u8     tos;
676         u16    df;
677         struct rtable *rt;                      /* Route to the other host */
678         struct net_device *tdev;                        /* Device to other host */
679         struct iphdr  *iph;                     /* Our new IP header */
680         int    max_headroom;                    /* The extra header space needed */
681         int    gre_hlen;
682         u32    dst;
683         int    mtu;
684
685         if (tunnel->recursion++) {
686                 tunnel->stat.collisions++;
687                 goto tx_error;
688         }
689
690         if (dev->hard_header) {
691                 gre_hlen = 0;
692                 tiph = (struct iphdr*)skb->data;
693         } else {
694                 gre_hlen = tunnel->hlen;
695                 tiph = &tunnel->parms.iph;
696         }
697
698         if ((dst = tiph->daddr) == 0) {
699                 /* NBMA tunnel */
700
701                 if (skb->dst == NULL) {
702                         tunnel->stat.tx_fifo_errors++;
703                         goto tx_error;
704                 }
705
706                 if (skb->protocol == htons(ETH_P_IP)) {
707                         rt = (struct rtable*)skb->dst;
708                         if ((dst = rt->rt_gateway) == 0)
709                                 goto tx_error_icmp;
710                 }
711 #ifdef CONFIG_IPV6
712                 else if (skb->protocol == htons(ETH_P_IPV6)) {
713                         struct in6_addr *addr6;
714                         int addr_type;
715                         struct neighbour *neigh = skb->dst->neighbour;
716
717                         if (neigh == NULL)
718                                 goto tx_error;
719
720                         addr6 = (struct in6_addr*)&neigh->primary_key;
721                         addr_type = ipv6_addr_type(addr6);
722
723                         if (addr_type == IPV6_ADDR_ANY) {
724                                 addr6 = &skb->nh.ipv6h->daddr;
725                                 addr_type = ipv6_addr_type(addr6);
726                         }
727
728                         if ((addr_type & IPV6_ADDR_COMPATv4) == 0)
729                                 goto tx_error_icmp;
730
731                         dst = addr6->s6_addr32[3];
732                 }
733 #endif
734                 else
735                         goto tx_error;
736         }
737
738         tos = tiph->tos;
739         if (tos&1) {
740                 if (skb->protocol == htons(ETH_P_IP))
741                         tos = old_iph->tos;
742                 tos &= ~1;
743         }
744
745         {
746                 struct flowi fl = { .oif = tunnel->parms.link,
747                                     .nl_u = { .ip4_u =
748                                               { .daddr = dst,
749                                                 .saddr = tiph->saddr,
750                                                 .tos = RT_TOS(tos) } },
751                                     .proto = IPPROTO_GRE };
752                 if (ip_route_output_key(&rt, &fl)) {
753                         tunnel->stat.tx_carrier_errors++;
754                         goto tx_error;
755                 }
756         }
757         tdev = rt->u.dst.dev;
758
759         if (tdev == dev) {
760                 ip_rt_put(rt);
761                 tunnel->stat.collisions++;
762                 goto tx_error;
763         }
764
765         df = tiph->frag_off;
766         if (df)
767                 mtu = dst_mtu(&rt->u.dst) - tunnel->hlen;
768         else
769                 mtu = skb->dst ? dst_mtu(skb->dst) : dev->mtu;
770
771         if (skb->dst)
772                 skb->dst->ops->update_pmtu(skb->dst, mtu);
773
774         if (skb->protocol == htons(ETH_P_IP)) {
775                 df |= (old_iph->frag_off&htons(IP_DF));
776
777                 if ((old_iph->frag_off&htons(IP_DF)) &&
778                     mtu < ntohs(old_iph->tot_len)) {
779                         icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
780                         ip_rt_put(rt);
781                         goto tx_error;
782                 }
783         }
784 #ifdef CONFIG_IPV6
785         else if (skb->protocol == htons(ETH_P_IPV6)) {
786                 struct rt6_info *rt6 = (struct rt6_info*)skb->dst;
787
788                 if (rt6 && mtu < dst_mtu(skb->dst) && mtu >= IPV6_MIN_MTU) {
789                         if ((tunnel->parms.iph.daddr && !MULTICAST(tunnel->parms.iph.daddr)) ||
790                             rt6->rt6i_dst.plen == 128) {
791                                 rt6->rt6i_flags |= RTF_MODIFIED;
792                                 skb->dst->metrics[RTAX_MTU-1] = mtu;
793                         }
794                 }
795
796                 if (mtu >= IPV6_MIN_MTU && mtu < skb->len - tunnel->hlen + gre_hlen) {
797                         icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, dev);
798                         ip_rt_put(rt);
799                         goto tx_error;
800                 }
801         }
802 #endif
803
804         if (tunnel->err_count > 0) {
805                 if (jiffies - tunnel->err_time < IPTUNNEL_ERR_TIMEO) {
806                         tunnel->err_count--;
807
808                         dst_link_failure(skb);
809                 } else
810                         tunnel->err_count = 0;
811         }
812
813         max_headroom = LL_RESERVED_SPACE(tdev) + gre_hlen;
814
815         if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) {
816                 struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
817                 if (!new_skb) {
818                         ip_rt_put(rt);
819                         stats->tx_dropped++;
820                         dev_kfree_skb(skb);
821                         tunnel->recursion--;
822                         return 0;
823                 }
824                 if (skb->sk)
825                         skb_set_owner_w(new_skb, skb->sk);
826                 dev_kfree_skb(skb);
827                 skb = new_skb;
828                 old_iph = skb->nh.iph;
829         }
830
831         skb->h.raw = skb->nh.raw;
832         skb->nh.raw = skb_push(skb, gre_hlen);
833         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
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                     =       skb->nh.iph;
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         ((u16*)(iph+1))[0] = tunnel->parms.o_flags;
862         ((u16*)(iph+1))[1] = skb->protocol;
863
864         if (tunnel->parms.o_flags&(GRE_KEY|GRE_CSUM|GRE_SEQ)) {
865                 u32 *ptr = (u32*)(((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                         *(__u16*)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 = (struct ip_tunnel*)dev->priv;
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 = (struct ip_tunnel*)dev->priv;
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 == ipgre_fb_tunnel_dev->priv)
1006                                 goto done;
1007                         dev = t->dev;
1008                 }
1009                 err = unregister_netdevice(dev);
1010                 break;
1011
1012         default:
1013                 err = -EINVAL;
1014         }
1015
1016 done:
1017         return err;
1018 }
1019
1020 static struct net_device_stats *ipgre_tunnel_get_stats(struct net_device *dev)
1021 {
1022         return &(((struct ip_tunnel*)dev->priv)->stat);
1023 }
1024
1025 static int ipgre_tunnel_change_mtu(struct net_device *dev, int new_mtu)
1026 {
1027         struct ip_tunnel *tunnel = (struct ip_tunnel*)dev->priv;
1028         if (new_mtu < 68 || new_mtu > 0xFFF8 - tunnel->hlen)
1029                 return -EINVAL;
1030         dev->mtu = new_mtu;
1031         return 0;
1032 }
1033
1034 #ifdef CONFIG_NET_IPGRE_BROADCAST
1035 /* Nice toy. Unfortunately, useless in real life :-)
1036    It allows to construct virtual multiprotocol broadcast "LAN"
1037    over the Internet, provided multicast routing is tuned.
1038
1039
1040    I have no idea was this bicycle invented before me,
1041    so that I had to set ARPHRD_IPGRE to a random value.
1042    I have an impression, that Cisco could make something similar,
1043    but this feature is apparently missing in IOS<=11.2(8).
1044    
1045    I set up 10.66.66/24 and fec0:6666:6666::0/96 as virtual networks
1046    with broadcast 224.66.66.66. If you have access to mbone, play with me :-)
1047
1048    ping -t 255 224.66.66.66
1049
1050    If nobody answers, mbone does not work.
1051
1052    ip tunnel add Universe mode gre remote 224.66.66.66 local <Your_real_addr> ttl 255
1053    ip addr add 10.66.66.<somewhat>/24 dev Universe
1054    ifconfig Universe up
1055    ifconfig Universe add fe80::<Your_real_addr>/10
1056    ifconfig Universe add fec0:6666:6666::<Your_real_addr>/96
1057    ftp 10.66.66.66
1058    ...
1059    ftp fec0:6666:6666::193.233.7.65
1060    ...
1061
1062  */
1063
1064 static int ipgre_header(struct sk_buff *skb, struct net_device *dev, unsigned short type,
1065                         void *daddr, void *saddr, unsigned len)
1066 {
1067         struct ip_tunnel *t = (struct ip_tunnel*)dev->priv;
1068         struct iphdr *iph = (struct iphdr *)skb_push(skb, t->hlen);
1069         u16 *p = (u16*)(iph+1);
1070
1071         memcpy(iph, &t->parms.iph, sizeof(struct iphdr));
1072         p[0]            = t->parms.o_flags;
1073         p[1]            = htons(type);
1074
1075         /*
1076          *      Set the source hardware address. 
1077          */
1078          
1079         if (saddr)
1080                 memcpy(&iph->saddr, saddr, 4);
1081
1082         if (daddr) {
1083                 memcpy(&iph->daddr, daddr, 4);
1084                 return t->hlen;
1085         }
1086         if (iph->daddr && !MULTICAST(iph->daddr))
1087                 return t->hlen;
1088         
1089         return -t->hlen;
1090 }
1091
1092 static int ipgre_open(struct net_device *dev)
1093 {
1094         struct ip_tunnel *t = (struct ip_tunnel*)dev->priv;
1095
1096         if (MULTICAST(t->parms.iph.daddr)) {
1097                 struct flowi fl = { .oif = t->parms.link,
1098                                     .nl_u = { .ip4_u =
1099                                               { .daddr = t->parms.iph.daddr,
1100                                                 .saddr = t->parms.iph.saddr,
1101                                                 .tos = RT_TOS(t->parms.iph.tos) } },
1102                                     .proto = IPPROTO_GRE };
1103                 struct rtable *rt;
1104                 if (ip_route_output_key(&rt, &fl))
1105                         return -EADDRNOTAVAIL;
1106                 dev = rt->u.dst.dev;
1107                 ip_rt_put(rt);
1108                 if (__in_dev_get(dev) == NULL)
1109                         return -EADDRNOTAVAIL;
1110                 t->mlink = dev->ifindex;
1111                 ip_mc_inc_group(__in_dev_get(dev), t->parms.iph.daddr);
1112         }
1113         return 0;
1114 }
1115
1116 static int ipgre_close(struct net_device *dev)
1117 {
1118         struct ip_tunnel *t = (struct ip_tunnel*)dev->priv;
1119         if (MULTICAST(t->parms.iph.daddr) && t->mlink) {
1120                 struct in_device *in_dev = inetdev_by_index(t->mlink);
1121                 if (in_dev) {
1122                         ip_mc_dec_group(in_dev, t->parms.iph.daddr);
1123                         in_dev_put(in_dev);
1124                 }
1125         }
1126         return 0;
1127 }
1128
1129 #endif
1130
1131 static void ipgre_tunnel_setup(struct net_device *dev)
1132 {
1133         SET_MODULE_OWNER(dev);
1134         dev->uninit             = ipgre_tunnel_uninit;
1135         dev->destructor         = free_netdev;
1136         dev->hard_start_xmit    = ipgre_tunnel_xmit;
1137         dev->get_stats          = ipgre_tunnel_get_stats;
1138         dev->do_ioctl           = ipgre_tunnel_ioctl;
1139         dev->change_mtu         = ipgre_tunnel_change_mtu;
1140
1141         dev->type               = ARPHRD_IPGRE;
1142         dev->hard_header_len    = LL_MAX_HEADER + sizeof(struct iphdr) + 4;
1143         dev->mtu                = 1500 - sizeof(struct iphdr) - 4;
1144         dev->flags              = IFF_NOARP;
1145         dev->iflink             = 0;
1146         dev->addr_len           = 4;
1147 }
1148
1149 static int ipgre_tunnel_init(struct net_device *dev)
1150 {
1151         struct net_device *tdev = NULL;
1152         struct ip_tunnel *tunnel;
1153         struct iphdr *iph;
1154         int hlen = LL_MAX_HEADER;
1155         int mtu = 1500;
1156         int addend = sizeof(struct iphdr) + 4;
1157
1158         tunnel = (struct ip_tunnel*)dev->priv;
1159         iph = &tunnel->parms.iph;
1160
1161         tunnel->dev = dev;
1162         strcpy(tunnel->parms.name, dev->name);
1163
1164         memcpy(dev->dev_addr, &tunnel->parms.iph.saddr, 4);
1165         memcpy(dev->broadcast, &tunnel->parms.iph.daddr, 4);
1166
1167         /* Guess output device to choose reasonable mtu and hard_header_len */
1168
1169         if (iph->daddr) {
1170                 struct flowi fl = { .oif = tunnel->parms.link,
1171                                     .nl_u = { .ip4_u =
1172                                               { .daddr = iph->daddr,
1173                                                 .saddr = iph->saddr,
1174                                                 .tos = RT_TOS(iph->tos) } },
1175                                     .proto = IPPROTO_GRE };
1176                 struct rtable *rt;
1177                 if (!ip_route_output_key(&rt, &fl)) {
1178                         tdev = rt->u.dst.dev;
1179                         ip_rt_put(rt);
1180                 }
1181
1182                 dev->flags |= IFF_POINTOPOINT;
1183
1184 #ifdef CONFIG_NET_IPGRE_BROADCAST
1185                 if (MULTICAST(iph->daddr)) {
1186                         if (!iph->saddr)
1187                                 return -EINVAL;
1188                         dev->flags = IFF_BROADCAST;
1189                         dev->hard_header = ipgre_header;
1190                         dev->open = ipgre_open;
1191                         dev->stop = ipgre_close;
1192                 }
1193 #endif
1194         }
1195
1196         if (!tdev && tunnel->parms.link)
1197                 tdev = __dev_get_by_index(tunnel->parms.link);
1198
1199         if (tdev) {
1200                 hlen = tdev->hard_header_len;
1201                 mtu = tdev->mtu;
1202         }
1203         dev->iflink = tunnel->parms.link;
1204
1205         /* Precalculate GRE options length */
1206         if (tunnel->parms.o_flags&(GRE_CSUM|GRE_KEY|GRE_SEQ)) {
1207                 if (tunnel->parms.o_flags&GRE_CSUM)
1208                         addend += 4;
1209                 if (tunnel->parms.o_flags&GRE_KEY)
1210                         addend += 4;
1211                 if (tunnel->parms.o_flags&GRE_SEQ)
1212                         addend += 4;
1213         }
1214         dev->hard_header_len = hlen + addend;
1215         dev->mtu = mtu - addend;
1216         tunnel->hlen = addend;
1217         return 0;
1218 }
1219
1220 int __init ipgre_fb_tunnel_init(struct net_device *dev)
1221 {
1222         struct ip_tunnel *tunnel = (struct ip_tunnel*)dev->priv;
1223         struct iphdr *iph = &tunnel->parms.iph;
1224
1225         tunnel->dev = dev;
1226         strcpy(tunnel->parms.name, dev->name);
1227
1228         iph->version            = 4;
1229         iph->protocol           = IPPROTO_GRE;
1230         iph->ihl                = 5;
1231         tunnel->hlen            = sizeof(struct iphdr) + 4;
1232
1233         dev_hold(dev);
1234         tunnels_wc[0]           = tunnel;
1235         return 0;
1236 }
1237
1238
1239 static struct net_protocol ipgre_protocol = {
1240         .handler        =       ipgre_rcv,
1241         .err_handler    =       ipgre_err,
1242 };
1243
1244
1245 /*
1246  *      And now the modules code and kernel interface.
1247  */
1248
1249 static int __init ipgre_init(void)
1250 {
1251         int err;
1252
1253         printk(KERN_INFO "GRE over IPv4 tunneling driver\n");
1254
1255         if (inet_add_protocol(&ipgre_protocol, IPPROTO_GRE) < 0) {
1256                 printk(KERN_INFO "ipgre init: can't add protocol\n");
1257                 return -EAGAIN;
1258         }
1259
1260         ipgre_fb_tunnel_dev = alloc_netdev(sizeof(struct ip_tunnel), "gre0",
1261                                            ipgre_tunnel_setup);
1262         if (!ipgre_fb_tunnel_dev) {
1263                 err = -ENOMEM;
1264                 goto err1;
1265         }
1266
1267         ipgre_fb_tunnel_dev->init = ipgre_fb_tunnel_init;
1268
1269         if ((err = register_netdev(ipgre_fb_tunnel_dev)))
1270                 goto err2;
1271 out:
1272         return err;
1273 err2:
1274         free_netdev(ipgre_fb_tunnel_dev);
1275 err1:
1276         inet_del_protocol(&ipgre_protocol, IPPROTO_GRE);
1277         goto out;
1278 }
1279
1280 static void ipgre_fini(void)
1281 {
1282         if (inet_del_protocol(&ipgre_protocol, IPPROTO_GRE) < 0)
1283                 printk(KERN_INFO "ipgre close: can't remove protocol\n");
1284
1285         unregister_netdev(ipgre_fb_tunnel_dev);
1286 }
1287
1288 module_init(ipgre_init);
1289 module_exit(ipgre_fini);
1290 MODULE_LICENSE("GPL");