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1 /*
2  * IP Payload Compression Protocol (IPComp) for IPv6 - RFC3173
3  *
4  * Copyright (C)2003 USAGI/WIDE Project
5  *
6  * Author       Mitsuru KANDA  <mk@linux-ipv6.org>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License as published by
10  * the Free Software Foundation; either version 2 of the License, or
11  * (at your option) any later version.
12  *
13  * This program is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16  * GNU General Public License for more details.
17  *
18  * You should have received a copy of the GNU General Public License
19  * along with this program; if not, write to the Free Software
20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
21  */
22 /*
23  * [Memo]
24  *
25  * Outbound:
26  *  The compression of IP datagram MUST be done before AH/ESP processing,
27  *  fragmentation, and the addition of Hop-by-Hop/Routing header.
28  *
29  * Inbound:
30  *  The decompression of IP datagram MUST be done after the reassembly,
31  *  AH/ESP processing.
32  */
33 #include <linux/module.h>
34 #include <net/ip.h>
35 #include <net/xfrm.h>
36 #include <net/ipcomp.h>
37 #include <asm/scatterlist.h>
38 #include <asm/semaphore.h>
39 #include <linux/crypto.h>
40 #include <linux/pfkeyv2.h>
41 #include <linux/random.h>
42 #include <linux/percpu.h>
43 #include <linux/smp.h>
44 #include <linux/list.h>
45 #include <linux/vmalloc.h>
46 #include <linux/rtnetlink.h>
47 #include <net/icmp.h>
48 #include <net/ipv6.h>
49 #include <net/protocol.h>
50 #include <linux/ipv6.h>
51 #include <linux/icmpv6.h>
52 #include <linux/mutex.h>
53
54 struct ipcomp6_tfms {
55         struct list_head list;
56         struct crypto_comp **tfms;
57         int users;
58 };
59
60 static DEFINE_MUTEX(ipcomp6_resource_mutex);
61 static void **ipcomp6_scratches;
62 static int ipcomp6_scratch_users;
63 static LIST_HEAD(ipcomp6_tfms_list);
64
65 static int ipcomp6_input(struct xfrm_state *x, struct sk_buff *skb)
66 {
67         int err = -ENOMEM;
68         struct ipv6hdr *iph;
69         struct ipv6_comp_hdr *ipch;
70         int plen, dlen;
71         struct ipcomp_data *ipcd = x->data;
72         u8 *start, *scratch;
73         struct crypto_comp *tfm;
74         int cpu;
75
76         if (skb_linearize_cow(skb))
77                 goto out;
78
79         skb->ip_summed = CHECKSUM_NONE;
80
81         /* Remove ipcomp header and decompress original payload */
82         iph = ipv6_hdr(skb);
83         ipch = (void *)skb->data;
84         skb->transport_header = skb->network_header + sizeof(*ipch);
85         __skb_pull(skb, sizeof(*ipch));
86
87         /* decompression */
88         plen = skb->len;
89         dlen = IPCOMP_SCRATCH_SIZE;
90         start = skb->data;
91
92         cpu = get_cpu();
93         scratch = *per_cpu_ptr(ipcomp6_scratches, cpu);
94         tfm = *per_cpu_ptr(ipcd->tfms, cpu);
95
96         err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen);
97         if (err) {
98                 err = -EINVAL;
99                 goto out_put_cpu;
100         }
101
102         if (dlen < (plen + sizeof(struct ipv6_comp_hdr))) {
103                 err = -EINVAL;
104                 goto out_put_cpu;
105         }
106
107         err = pskb_expand_head(skb, 0, dlen - plen, GFP_ATOMIC);
108         if (err) {
109                 goto out_put_cpu;
110         }
111
112         skb->truesize += dlen - plen;
113         __skb_put(skb, dlen - plen);
114         skb_copy_to_linear_data(skb, scratch, dlen);
115         err = ipch->nexthdr;
116
117 out_put_cpu:
118         put_cpu();
119 out:
120         return err;
121 }
122
123 static int ipcomp6_output(struct xfrm_state *x, struct sk_buff *skb)
124 {
125         int err;
126         struct ipv6hdr *top_iph;
127         struct ipv6_comp_hdr *ipch;
128         struct ipcomp_data *ipcd = x->data;
129         int plen, dlen;
130         u8 *start, *scratch;
131         struct crypto_comp *tfm;
132         int cpu;
133         int hdr_len = skb_transport_offset(skb);
134
135         /* check whether datagram len is larger than threshold */
136         if ((skb->len - hdr_len) < ipcd->threshold) {
137                 goto out_ok;
138         }
139
140         if (skb_linearize_cow(skb))
141                 goto out_ok;
142
143         /* compression */
144         plen = skb->len - hdr_len;
145         dlen = IPCOMP_SCRATCH_SIZE;
146         start = skb_transport_header(skb);
147
148         cpu = get_cpu();
149         scratch = *per_cpu_ptr(ipcomp6_scratches, cpu);
150         tfm = *per_cpu_ptr(ipcd->tfms, cpu);
151
152         err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);
153         if (err || (dlen + sizeof(struct ipv6_comp_hdr)) >= plen) {
154                 put_cpu();
155                 goto out_ok;
156         }
157         memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
158         put_cpu();
159         pskb_trim(skb, hdr_len + dlen + sizeof(struct ip_comp_hdr));
160
161         /* insert ipcomp header and replace datagram */
162         top_iph = (struct ipv6hdr *)skb->data;
163
164         top_iph->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
165
166         ipch = (struct ipv6_comp_hdr *)start;
167         ipch->nexthdr = *skb_network_header(skb);
168         ipch->flags = 0;
169         ipch->cpi = htons((u16 )ntohl(x->id.spi));
170         *skb_network_header(skb) = IPPROTO_COMP;
171
172 out_ok:
173         return 0;
174 }
175
176 static void ipcomp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
177                                 int type, int code, int offset, __be32 info)
178 {
179         __be32 spi;
180         struct ipv6hdr *iph = (struct ipv6hdr*)skb->data;
181         struct ipv6_comp_hdr *ipcomph = (struct ipv6_comp_hdr*)(skb->data+offset);
182         struct xfrm_state *x;
183
184         if (type != ICMPV6_DEST_UNREACH && type != ICMPV6_PKT_TOOBIG)
185                 return;
186
187         spi = htonl(ntohs(ipcomph->cpi));
188         x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr, spi, IPPROTO_COMP, AF_INET6);
189         if (!x)
190                 return;
191
192         printk(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/" NIP6_FMT "\n",
193                         spi, NIP6(iph->daddr));
194         xfrm_state_put(x);
195 }
196
197 static struct xfrm_state *ipcomp6_tunnel_create(struct xfrm_state *x)
198 {
199         struct xfrm_state *t = NULL;
200         u8 mode = XFRM_MODE_TUNNEL;
201
202         t = xfrm_state_alloc();
203         if (!t)
204                 goto out;
205
206         t->id.proto = IPPROTO_IPV6;
207         t->id.spi = xfrm6_tunnel_alloc_spi((xfrm_address_t *)&x->props.saddr);
208         if (!t->id.spi)
209                 goto error;
210
211         memcpy(t->id.daddr.a6, x->id.daddr.a6, sizeof(struct in6_addr));
212         memcpy(&t->sel, &x->sel, sizeof(t->sel));
213         t->props.family = AF_INET6;
214         if (x->props.mode == XFRM_MODE_BEET)
215                 mode = x->props.mode;
216         t->props.mode = mode;
217         memcpy(t->props.saddr.a6, x->props.saddr.a6, sizeof(struct in6_addr));
218
219         if (xfrm_init_state(t))
220                 goto error;
221
222         atomic_set(&t->tunnel_users, 1);
223
224 out:
225         return t;
226
227 error:
228         t->km.state = XFRM_STATE_DEAD;
229         xfrm_state_put(t);
230         t = NULL;
231         goto out;
232 }
233
234 static int ipcomp6_tunnel_attach(struct xfrm_state *x)
235 {
236         int err = 0;
237         struct xfrm_state *t = NULL;
238         __be32 spi;
239
240         spi = xfrm6_tunnel_spi_lookup((xfrm_address_t *)&x->props.saddr);
241         if (spi)
242                 t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr,
243                                               spi, IPPROTO_IPV6, AF_INET6);
244         if (!t) {
245                 t = ipcomp6_tunnel_create(x);
246                 if (!t) {
247                         err = -EINVAL;
248                         goto out;
249                 }
250                 xfrm_state_insert(t);
251                 xfrm_state_hold(t);
252         }
253         x->tunnel = t;
254         atomic_inc(&t->tunnel_users);
255
256 out:
257         return err;
258 }
259
260 static void ipcomp6_free_scratches(void)
261 {
262         int i;
263         void **scratches;
264
265         if (--ipcomp6_scratch_users)
266                 return;
267
268         scratches = ipcomp6_scratches;
269         if (!scratches)
270                 return;
271
272         for_each_possible_cpu(i) {
273                 void *scratch = *per_cpu_ptr(scratches, i);
274
275                 vfree(scratch);
276         }
277
278         free_percpu(scratches);
279 }
280
281 static void **ipcomp6_alloc_scratches(void)
282 {
283         int i;
284         void **scratches;
285
286         if (ipcomp6_scratch_users++)
287                 return ipcomp6_scratches;
288
289         scratches = alloc_percpu(void *);
290         if (!scratches)
291                 return NULL;
292
293         ipcomp6_scratches = scratches;
294
295         for_each_possible_cpu(i) {
296                 void *scratch = vmalloc(IPCOMP_SCRATCH_SIZE);
297                 if (!scratch)
298                         return NULL;
299                 *per_cpu_ptr(scratches, i) = scratch;
300         }
301
302         return scratches;
303 }
304
305 static void ipcomp6_free_tfms(struct crypto_comp **tfms)
306 {
307         struct ipcomp6_tfms *pos;
308         int cpu;
309
310         list_for_each_entry(pos, &ipcomp6_tfms_list, list) {
311                 if (pos->tfms == tfms)
312                         break;
313         }
314
315         BUG_TRAP(pos);
316
317         if (--pos->users)
318                 return;
319
320         list_del(&pos->list);
321         kfree(pos);
322
323         if (!tfms)
324                 return;
325
326         for_each_possible_cpu(cpu) {
327                 struct crypto_comp *tfm = *per_cpu_ptr(tfms, cpu);
328                 crypto_free_comp(tfm);
329         }
330         free_percpu(tfms);
331 }
332
333 static struct crypto_comp **ipcomp6_alloc_tfms(const char *alg_name)
334 {
335         struct ipcomp6_tfms *pos;
336         struct crypto_comp **tfms;
337         int cpu;
338
339         /* This can be any valid CPU ID so we don't need locking. */
340         cpu = raw_smp_processor_id();
341
342         list_for_each_entry(pos, &ipcomp6_tfms_list, list) {
343                 struct crypto_comp *tfm;
344
345                 tfms = pos->tfms;
346                 tfm = *per_cpu_ptr(tfms, cpu);
347
348                 if (!strcmp(crypto_comp_name(tfm), alg_name)) {
349                         pos->users++;
350                         return tfms;
351                 }
352         }
353
354         pos = kmalloc(sizeof(*pos), GFP_KERNEL);
355         if (!pos)
356                 return NULL;
357
358         pos->users = 1;
359         INIT_LIST_HEAD(&pos->list);
360         list_add(&pos->list, &ipcomp6_tfms_list);
361
362         pos->tfms = tfms = alloc_percpu(struct crypto_comp *);
363         if (!tfms)
364                 goto error;
365
366         for_each_possible_cpu(cpu) {
367                 struct crypto_comp *tfm = crypto_alloc_comp(alg_name, 0,
368                                                             CRYPTO_ALG_ASYNC);
369                 if (!tfm)
370                         goto error;
371                 *per_cpu_ptr(tfms, cpu) = tfm;
372         }
373
374         return tfms;
375
376 error:
377         ipcomp6_free_tfms(tfms);
378         return NULL;
379 }
380
381 static void ipcomp6_free_data(struct ipcomp_data *ipcd)
382 {
383         if (ipcd->tfms)
384                 ipcomp6_free_tfms(ipcd->tfms);
385         ipcomp6_free_scratches();
386 }
387
388 static void ipcomp6_destroy(struct xfrm_state *x)
389 {
390         struct ipcomp_data *ipcd = x->data;
391         if (!ipcd)
392                 return;
393         xfrm_state_delete_tunnel(x);
394         mutex_lock(&ipcomp6_resource_mutex);
395         ipcomp6_free_data(ipcd);
396         mutex_unlock(&ipcomp6_resource_mutex);
397         kfree(ipcd);
398
399         xfrm6_tunnel_free_spi((xfrm_address_t *)&x->props.saddr);
400 }
401
402 static int ipcomp6_init_state(struct xfrm_state *x)
403 {
404         int err;
405         struct ipcomp_data *ipcd;
406         struct xfrm_algo_desc *calg_desc;
407
408         err = -EINVAL;
409         if (!x->calg)
410                 goto out;
411
412         if (x->encap)
413                 goto out;
414
415         err = -ENOMEM;
416         ipcd = kzalloc(sizeof(*ipcd), GFP_KERNEL);
417         if (!ipcd)
418                 goto out;
419
420         x->props.header_len = 0;
421         if (x->props.mode == XFRM_MODE_TUNNEL)
422                 x->props.header_len += sizeof(struct ipv6hdr);
423
424         mutex_lock(&ipcomp6_resource_mutex);
425         if (!ipcomp6_alloc_scratches())
426                 goto error;
427
428         ipcd->tfms = ipcomp6_alloc_tfms(x->calg->alg_name);
429         if (!ipcd->tfms)
430                 goto error;
431         mutex_unlock(&ipcomp6_resource_mutex);
432
433         if (x->props.mode == XFRM_MODE_TUNNEL) {
434                 err = ipcomp6_tunnel_attach(x);
435                 if (err)
436                         goto error_tunnel;
437         }
438
439         calg_desc = xfrm_calg_get_byname(x->calg->alg_name, 0);
440         BUG_ON(!calg_desc);
441         ipcd->threshold = calg_desc->uinfo.comp.threshold;
442         x->data = ipcd;
443         err = 0;
444 out:
445         return err;
446 error_tunnel:
447         mutex_lock(&ipcomp6_resource_mutex);
448 error:
449         ipcomp6_free_data(ipcd);
450         mutex_unlock(&ipcomp6_resource_mutex);
451         kfree(ipcd);
452
453         goto out;
454 }
455
456 static struct xfrm_type ipcomp6_type =
457 {
458         .description    = "IPCOMP6",
459         .owner          = THIS_MODULE,
460         .proto          = IPPROTO_COMP,
461         .init_state     = ipcomp6_init_state,
462         .destructor     = ipcomp6_destroy,
463         .input          = ipcomp6_input,
464         .output         = ipcomp6_output,
465         .hdr_offset     = xfrm6_find_1stfragopt,
466 };
467
468 static struct inet6_protocol ipcomp6_protocol =
469 {
470         .handler        = xfrm6_rcv,
471         .err_handler    = ipcomp6_err,
472         .flags          = INET6_PROTO_NOPOLICY,
473 };
474
475 static int __init ipcomp6_init(void)
476 {
477         if (xfrm_register_type(&ipcomp6_type, AF_INET6) < 0) {
478                 printk(KERN_INFO "ipcomp6 init: can't add xfrm type\n");
479                 return -EAGAIN;
480         }
481         if (inet6_add_protocol(&ipcomp6_protocol, IPPROTO_COMP) < 0) {
482                 printk(KERN_INFO "ipcomp6 init: can't add protocol\n");
483                 xfrm_unregister_type(&ipcomp6_type, AF_INET6);
484                 return -EAGAIN;
485         }
486         return 0;
487 }
488
489 static void __exit ipcomp6_fini(void)
490 {
491         if (inet6_del_protocol(&ipcomp6_protocol, IPPROTO_COMP) < 0)
492                 printk(KERN_INFO "ipv6 ipcomp close: can't remove protocol\n");
493         if (xfrm_unregister_type(&ipcomp6_type, AF_INET6) < 0)
494                 printk(KERN_INFO "ipv6 ipcomp close: can't remove xfrm type\n");
495 }
496
497 module_init(ipcomp6_init);
498 module_exit(ipcomp6_fini);
499 MODULE_LICENSE("GPL");
500 MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) for IPv6 - RFC3173");
501 MODULE_AUTHOR("Mitsuru KANDA <mk@linux-ipv6.org>");
502
503