ipcomp.c revision 37fedd3aab6517daec628764c5d66dd8761fbe5f 
1/*
2 * IP Payload Compression Protocol (IPComp) - RFC3173.
3 *
4 * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the Free
8 * Software Foundation; either version 2 of the License, or (at your option)
9 * any later version.
10 *
11 * Todo:
12 *   - Tunable compression parameters.
13 *   - Compression stats.
14 *   - Adaptive compression.
15 */
16#include <linux/module.h>
17#include <asm/scatterlist.h>
18#include <asm/semaphore.h>
19#include <linux/crypto.h>
20#include <linux/pfkeyv2.h>
21#include <linux/percpu.h>
22#include <linux/smp.h>
23#include <linux/list.h>
24#include <linux/vmalloc.h>
25#include <linux/rtnetlink.h>
26#include <linux/mutex.h>
27#include <net/ip.h>
28#include <net/xfrm.h>
29#include <net/icmp.h>
30#include <net/ipcomp.h>
31#include <net/protocol.h>
32
33struct ipcomp_tfms {
34	struct list_head list;
35	struct crypto_comp **tfms;
36	int users;
37};
38
39static DEFINE_MUTEX(ipcomp_resource_mutex);
40static void **ipcomp_scratches;
41static int ipcomp_scratch_users;
42static LIST_HEAD(ipcomp_tfms_list);
43
44static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
45{
46	struct ipcomp_data *ipcd = x->data;
47	const int plen = skb->len;
48	int dlen = IPCOMP_SCRATCH_SIZE;
49	const u8 *start = skb->data;
50	const int cpu = get_cpu();
51	u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
52	struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu);
53	int err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen);
54
55	if (err)
56		goto out;
57
58	if (dlen < (plen + sizeof(struct ip_comp_hdr))) {
59		err = -EINVAL;
60		goto out;
61	}
62
63	err = pskb_expand_head(skb, 0, dlen - plen, GFP_ATOMIC);
64	if (err)
65		goto out;
66
67	skb->truesize += dlen - plen;
68	__skb_put(skb, dlen - plen);
69	skb_copy_to_linear_data(skb, scratch, dlen);
70out:
71	put_cpu();
72	return err;
73}
74
75static int ipcomp_input(struct xfrm_state *x, struct sk_buff *skb)
76{
77	int err = -ENOMEM;
78	struct iphdr *iph;
79	struct ip_comp_hdr *ipch;
80
81	if (skb_linearize_cow(skb))
82		goto out;
83
84	skb->ip_summed = CHECKSUM_NONE;
85
86	/* Remove ipcomp header and decompress original payload */
87	iph = ip_hdr(skb);
88	ipch = (void *)skb->data;
89	iph->protocol = ipch->nexthdr;
90	skb->transport_header = skb->network_header + sizeof(*ipch);
91	__skb_pull(skb, sizeof(*ipch));
92	err = ipcomp_decompress(x, skb);
93
94out:
95	return err;
96}
97
98static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
99{
100	struct ipcomp_data *ipcd = x->data;
101	const int ihlen = skb_transport_offset(skb);
102	const int plen = skb->len - ihlen;
103	int dlen = IPCOMP_SCRATCH_SIZE;
104	u8 *start = skb_transport_header(skb);
105	const int cpu = get_cpu();
106	u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
107	struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu);
108	int err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);
109
110	if (err)
111		goto out;
112
113	if ((dlen + sizeof(struct ip_comp_hdr)) >= plen) {
114		err = -EMSGSIZE;
115		goto out;
116	}
117
118	memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
119	put_cpu();
120
121	pskb_trim(skb, ihlen + dlen + sizeof(struct ip_comp_hdr));
122	return 0;
123
124out:
125	put_cpu();
126	return err;
127}
128
129static int ipcomp_output(struct xfrm_state *x, struct sk_buff *skb)
130{
131	int err;
132	struct ip_comp_hdr *ipch;
133	struct ipcomp_data *ipcd = x->data;
134	int hdr_len = 0;
135	struct iphdr *iph = ip_hdr(skb);
136
137	skb_push(skb, -skb_network_offset(skb));
138	iph->tot_len = htons(skb->len);
139	hdr_len = iph->ihl * 4;
140	if ((skb->len - hdr_len) < ipcd->threshold) {
141		/* Don't bother compressing */
142		goto out_ok;
143	}
144
145	if (skb_linearize_cow(skb))
146		goto out_ok;
147
148	err = ipcomp_compress(x, skb);
149	iph = ip_hdr(skb);
150
151	if (err) {
152		goto out_ok;
153	}
154
155	/* Install ipcomp header, convert into ipcomp datagram. */
156	iph->tot_len = htons(skb->len);
157	ipch = (struct ip_comp_hdr *)skb_transport_header(skb);
158	ipch->nexthdr = *skb_mac_header(skb);
159	ipch->flags = 0;
160	ipch->cpi = htons((u16 )ntohl(x->id.spi));
161	*skb_mac_header(skb) = IPPROTO_COMP;
162	ip_send_check(iph);
163	return 0;
164
165out_ok:
166	if (x->props.mode == XFRM_MODE_TUNNEL)
167		ip_send_check(iph);
168	return 0;
169}
170
171static void ipcomp4_err(struct sk_buff *skb, u32 info)
172{
173	__be32 spi;
174	struct iphdr *iph = (struct iphdr *)skb->data;
175	struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
176	struct xfrm_state *x;
177
178	if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
179	    icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
180		return;
181
182	spi = htonl(ntohs(ipch->cpi));
183	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr,
184			      spi, IPPROTO_COMP, AF_INET);
185	if (!x)
186		return;
187	NETDEBUG(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%u.%u.%u.%u\n",
188		 spi, NIPQUAD(iph->daddr));
189	xfrm_state_put(x);
190}
191
192/* We always hold one tunnel user reference to indicate a tunnel */
193static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
194{
195	struct xfrm_state *t;
196	u8 mode = XFRM_MODE_TUNNEL;
197
198	t = xfrm_state_alloc();
199	if (t == NULL)
200		goto out;
201
202	t->id.proto = IPPROTO_IPIP;
203	t->id.spi = x->props.saddr.a4;
204	t->id.daddr.a4 = x->id.daddr.a4;
205	memcpy(&t->sel, &x->sel, sizeof(t->sel));
206	t->props.family = AF_INET;
207	if (x->props.mode == XFRM_MODE_BEET)
208		mode = x->props.mode;
209	t->props.mode = mode;
210	t->props.saddr.a4 = x->props.saddr.a4;
211	t->props.flags = x->props.flags;
212
213	if (xfrm_init_state(t))
214		goto error;
215
216	atomic_set(&t->tunnel_users, 1);
217out:
218	return t;
219
220error:
221	t->km.state = XFRM_STATE_DEAD;
222	xfrm_state_put(t);
223	t = NULL;
224	goto out;
225}
226
227/*
228 * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
229 * always incremented on success.
230 */
231static int ipcomp_tunnel_attach(struct xfrm_state *x)
232{
233	int err = 0;
234	struct xfrm_state *t;
235
236	t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr.a4,
237			      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
238	if (!t) {
239		t = ipcomp_tunnel_create(x);
240		if (!t) {
241			err = -EINVAL;
242			goto out;
243		}
244		xfrm_state_insert(t);
245		xfrm_state_hold(t);
246	}
247	x->tunnel = t;
248	atomic_inc(&t->tunnel_users);
249out:
250	return err;
251}
252
253static void ipcomp_free_scratches(void)
254{
255	int i;
256	void **scratches;
257
258	if (--ipcomp_scratch_users)
259		return;
260
261	scratches = ipcomp_scratches;
262	if (!scratches)
263		return;
264
265	for_each_possible_cpu(i)
266		vfree(*per_cpu_ptr(scratches, i));
267
268	free_percpu(scratches);
269}
270
271static void **ipcomp_alloc_scratches(void)
272{
273	int i;
274	void **scratches;
275
276	if (ipcomp_scratch_users++)
277		return ipcomp_scratches;
278
279	scratches = alloc_percpu(void *);
280	if (!scratches)
281		return NULL;
282
283	ipcomp_scratches = scratches;
284
285	for_each_possible_cpu(i) {
286		void *scratch = vmalloc(IPCOMP_SCRATCH_SIZE);
287		if (!scratch)
288			return NULL;
289		*per_cpu_ptr(scratches, i) = scratch;
290	}
291
292	return scratches;
293}
294
295static void ipcomp_free_tfms(struct crypto_comp **tfms)
296{
297	struct ipcomp_tfms *pos;
298	int cpu;
299
300	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
301		if (pos->tfms == tfms)
302			break;
303	}
304
305	BUG_TRAP(pos);
306
307	if (--pos->users)
308		return;
309
310	list_del(&pos->list);
311	kfree(pos);
312
313	if (!tfms)
314		return;
315
316	for_each_possible_cpu(cpu) {
317		struct crypto_comp *tfm = *per_cpu_ptr(tfms, cpu);
318		crypto_free_comp(tfm);
319	}
320	free_percpu(tfms);
321}
322
323static struct crypto_comp **ipcomp_alloc_tfms(const char *alg_name)
324{
325	struct ipcomp_tfms *pos;
326	struct crypto_comp **tfms;
327	int cpu;
328
329	/* This can be any valid CPU ID so we don't need locking. */
330	cpu = raw_smp_processor_id();
331
332	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
333		struct crypto_comp *tfm;
334
335		tfms = pos->tfms;
336		tfm = *per_cpu_ptr(tfms, cpu);
337
338		if (!strcmp(crypto_comp_name(tfm), alg_name)) {
339			pos->users++;
340			return tfms;
341		}
342	}
343
344	pos = kmalloc(sizeof(*pos), GFP_KERNEL);
345	if (!pos)
346		return NULL;
347
348	pos->users = 1;
349	INIT_LIST_HEAD(&pos->list);
350	list_add(&pos->list, &ipcomp_tfms_list);
351
352	pos->tfms = tfms = alloc_percpu(struct crypto_comp *);
353	if (!tfms)
354		goto error;
355
356	for_each_possible_cpu(cpu) {
357		struct crypto_comp *tfm = crypto_alloc_comp(alg_name, 0,
358							    CRYPTO_ALG_ASYNC);
359		if (!tfm)
360			goto error;
361		*per_cpu_ptr(tfms, cpu) = tfm;
362	}
363
364	return tfms;
365
366error:
367	ipcomp_free_tfms(tfms);
368	return NULL;
369}
370
371static void ipcomp_free_data(struct ipcomp_data *ipcd)
372{
373	if (ipcd->tfms)
374		ipcomp_free_tfms(ipcd->tfms);
375	ipcomp_free_scratches();
376}
377
378static void ipcomp_destroy(struct xfrm_state *x)
379{
380	struct ipcomp_data *ipcd = x->data;
381	if (!ipcd)
382		return;
383	xfrm_state_delete_tunnel(x);
384	mutex_lock(&ipcomp_resource_mutex);
385	ipcomp_free_data(ipcd);
386	mutex_unlock(&ipcomp_resource_mutex);
387	kfree(ipcd);
388}
389
390static int ipcomp_init_state(struct xfrm_state *x)
391{
392	int err;
393	struct ipcomp_data *ipcd;
394	struct xfrm_algo_desc *calg_desc;
395
396	err = -EINVAL;
397	if (!x->calg)
398		goto out;
399
400	if (x->encap)
401		goto out;
402
403	err = -ENOMEM;
404	ipcd = kzalloc(sizeof(*ipcd), GFP_KERNEL);
405	if (!ipcd)
406		goto out;
407
408	x->props.header_len = 0;
409	if (x->props.mode == XFRM_MODE_TUNNEL)
410		x->props.header_len += sizeof(struct iphdr);
411
412	mutex_lock(&ipcomp_resource_mutex);
413	if (!ipcomp_alloc_scratches())
414		goto error;
415
416	ipcd->tfms = ipcomp_alloc_tfms(x->calg->alg_name);
417	if (!ipcd->tfms)
418		goto error;
419	mutex_unlock(&ipcomp_resource_mutex);
420
421	if (x->props.mode == XFRM_MODE_TUNNEL) {
422		err = ipcomp_tunnel_attach(x);
423		if (err)
424			goto error_tunnel;
425	}
426
427	calg_desc = xfrm_calg_get_byname(x->calg->alg_name, 0);
428	BUG_ON(!calg_desc);
429	ipcd->threshold = calg_desc->uinfo.comp.threshold;
430	x->data = ipcd;
431	err = 0;
432out:
433	return err;
434
435error_tunnel:
436	mutex_lock(&ipcomp_resource_mutex);
437error:
438	ipcomp_free_data(ipcd);
439	mutex_unlock(&ipcomp_resource_mutex);
440	kfree(ipcd);
441	goto out;
442}
443
444static struct xfrm_type ipcomp_type = {
445	.description	= "IPCOMP4",
446	.owner		= THIS_MODULE,
447	.proto	     	= IPPROTO_COMP,
448	.init_state	= ipcomp_init_state,
449	.destructor	= ipcomp_destroy,
450	.input		= ipcomp_input,
451	.output		= ipcomp_output
452};
453
454static struct net_protocol ipcomp4_protocol = {
455	.handler	=	xfrm4_rcv,
456	.err_handler	=	ipcomp4_err,
457	.no_policy	=	1,
458};
459
460static int __init ipcomp4_init(void)
461{
462	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
463		printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
464		return -EAGAIN;
465	}
466	if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
467		printk(KERN_INFO "ipcomp init: can't add protocol\n");
468		xfrm_unregister_type(&ipcomp_type, AF_INET);
469		return -EAGAIN;
470	}
471	return 0;
472}
473
474static void __exit ipcomp4_fini(void)
475{
476	if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
477		printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
478	if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
479		printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
480}
481
482module_init(ipcomp4_init);
483module_exit(ipcomp4_fini);
484
485MODULE_LICENSE("GPL");
486MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
487MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
488
489MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);
490