ipcomp.c revision e4d5b79c661c7cfca9d8d5afd040a295f128d3cb 
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	int err, plen, dlen;
47	struct ipcomp_data *ipcd = x->data;
48	u8 *start, *scratch;
49	struct crypto_comp *tfm;
50	int cpu;
51
52	plen = skb->len;
53	dlen = IPCOMP_SCRATCH_SIZE;
54	start = skb->data;
55
56	cpu = get_cpu();
57	scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
58	tfm = *per_cpu_ptr(ipcd->tfms, cpu);
59
60	err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen);
61	if (err)
62		goto out;
63
64	if (dlen < (plen + sizeof(struct ip_comp_hdr))) {
65		err = -EINVAL;
66		goto out;
67	}
68
69	err = pskb_expand_head(skb, 0, dlen - plen, GFP_ATOMIC);
70	if (err)
71		goto out;
72
73	skb->truesize += dlen - plen;
74	__skb_put(skb, dlen - plen);
75	memcpy(skb->data, scratch, dlen);
76out:
77	put_cpu();
78	return err;
79}
80
81static int ipcomp_input(struct xfrm_state *x, struct sk_buff *skb)
82{
83	int err = -ENOMEM;
84	struct iphdr *iph;
85	struct ip_comp_hdr *ipch;
86
87	if (skb_linearize_cow(skb))
88	    	goto out;
89
90	skb->ip_summed = CHECKSUM_NONE;
91
92	/* Remove ipcomp header and decompress original payload */
93	iph = skb->nh.iph;
94	ipch = (void *)skb->data;
95	iph->protocol = ipch->nexthdr;
96	skb->h.raw = skb->nh.raw + sizeof(*ipch);
97	__skb_pull(skb, sizeof(*ipch));
98	err = ipcomp_decompress(x, skb);
99
100out:
101	return err;
102}
103
104static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
105{
106	int err, plen, dlen, ihlen;
107	struct iphdr *iph = skb->nh.iph;
108	struct ipcomp_data *ipcd = x->data;
109	u8 *start, *scratch;
110	struct crypto_comp *tfm;
111	int cpu;
112
113	ihlen = iph->ihl * 4;
114	plen = skb->len - ihlen;
115	dlen = IPCOMP_SCRATCH_SIZE;
116	start = skb->data + ihlen;
117
118	cpu = get_cpu();
119	scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
120	tfm = *per_cpu_ptr(ipcd->tfms, cpu);
121
122	err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);
123	if (err)
124		goto out;
125
126	if ((dlen + sizeof(struct ip_comp_hdr)) >= plen) {
127		err = -EMSGSIZE;
128		goto out;
129	}
130
131	memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
132	put_cpu();
133
134	pskb_trim(skb, ihlen + dlen + sizeof(struct ip_comp_hdr));
135	return 0;
136
137out:
138	put_cpu();
139	return err;
140}
141
142static int ipcomp_output(struct xfrm_state *x, struct sk_buff *skb)
143{
144	int err;
145	struct iphdr *iph;
146	struct ip_comp_hdr *ipch;
147	struct ipcomp_data *ipcd = x->data;
148	int hdr_len = 0;
149
150	iph = skb->nh.iph;
151	iph->tot_len = htons(skb->len);
152	hdr_len = iph->ihl * 4;
153	if ((skb->len - hdr_len) < ipcd->threshold) {
154		/* Don't bother compressing */
155		goto out_ok;
156	}
157
158	if (skb_linearize_cow(skb))
159		goto out_ok;
160
161	err = ipcomp_compress(x, skb);
162	iph = skb->nh.iph;
163
164	if (err) {
165		goto out_ok;
166	}
167
168	/* Install ipcomp header, convert into ipcomp datagram. */
169	iph->tot_len = htons(skb->len);
170	ipch = (struct ip_comp_hdr *)((char *)iph + iph->ihl * 4);
171	ipch->nexthdr = iph->protocol;
172	ipch->flags = 0;
173	ipch->cpi = htons((u16 )ntohl(x->id.spi));
174	iph->protocol = IPPROTO_COMP;
175	ip_send_check(iph);
176	return 0;
177
178out_ok:
179	if (x->props.mode)
180		ip_send_check(iph);
181	return 0;
182}
183
184static void ipcomp4_err(struct sk_buff *skb, u32 info)
185{
186	u32 spi;
187	struct iphdr *iph = (struct iphdr *)skb->data;
188	struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
189	struct xfrm_state *x;
190
191	if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
192	    skb->h.icmph->code != ICMP_FRAG_NEEDED)
193		return;
194
195	spi = htonl(ntohs(ipch->cpi));
196	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr,
197	                      spi, IPPROTO_COMP, AF_INET);
198	if (!x)
199		return;
200	NETDEBUG(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%u.%u.%u.%u\n",
201		 spi, NIPQUAD(iph->daddr));
202	xfrm_state_put(x);
203}
204
205/* We always hold one tunnel user reference to indicate a tunnel */
206static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
207{
208	struct xfrm_state *t;
209
210	t = xfrm_state_alloc();
211	if (t == NULL)
212		goto out;
213
214	t->id.proto = IPPROTO_IPIP;
215	t->id.spi = x->props.saddr.a4;
216	t->id.daddr.a4 = x->id.daddr.a4;
217	memcpy(&t->sel, &x->sel, sizeof(t->sel));
218	t->props.family = AF_INET;
219	t->props.mode = 1;
220	t->props.saddr.a4 = x->props.saddr.a4;
221	t->props.flags = x->props.flags;
222
223	if (xfrm_init_state(t))
224		goto error;
225
226	atomic_set(&t->tunnel_users, 1);
227out:
228	return t;
229
230error:
231	t->km.state = XFRM_STATE_DEAD;
232	xfrm_state_put(t);
233	t = NULL;
234	goto out;
235}
236
237/*
238 * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
239 * always incremented on success.
240 */
241static int ipcomp_tunnel_attach(struct xfrm_state *x)
242{
243	int err = 0;
244	struct xfrm_state *t;
245
246	t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr.a4,
247	                      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
248	if (!t) {
249		t = ipcomp_tunnel_create(x);
250		if (!t) {
251			err = -EINVAL;
252			goto out;
253		}
254		xfrm_state_insert(t);
255		xfrm_state_hold(t);
256	}
257	x->tunnel = t;
258	atomic_inc(&t->tunnel_users);
259out:
260	return err;
261}
262
263static void ipcomp_free_scratches(void)
264{
265	int i;
266	void **scratches;
267
268	if (--ipcomp_scratch_users)
269		return;
270
271	scratches = ipcomp_scratches;
272	if (!scratches)
273		return;
274
275	for_each_possible_cpu(i)
276		vfree(*per_cpu_ptr(scratches, i));
277
278	free_percpu(scratches);
279}
280
281static void **ipcomp_alloc_scratches(void)
282{
283	int i;
284	void **scratches;
285
286	if (ipcomp_scratch_users++)
287		return ipcomp_scratches;
288
289	scratches = alloc_percpu(void *);
290	if (!scratches)
291		return NULL;
292
293	ipcomp_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
305static void ipcomp_free_tfms(struct crypto_comp **tfms)
306{
307	struct ipcomp_tfms *pos;
308	int cpu;
309
310	list_for_each_entry(pos, &ipcomp_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
333static struct crypto_comp **ipcomp_alloc_tfms(const char *alg_name)
334{
335	struct ipcomp_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, &ipcomp_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, &ipcomp_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
376error:
377	ipcomp_free_tfms(tfms);
378	return NULL;
379}
380
381static void ipcomp_free_data(struct ipcomp_data *ipcd)
382{
383	if (ipcd->tfms)
384		ipcomp_free_tfms(ipcd->tfms);
385	ipcomp_free_scratches();
386}
387
388static void ipcomp_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(&ipcomp_resource_mutex);
395	ipcomp_free_data(ipcd);
396	mutex_unlock(&ipcomp_resource_mutex);
397	kfree(ipcd);
398}
399
400static int ipcomp_init_state(struct xfrm_state *x)
401{
402	int err;
403	struct ipcomp_data *ipcd;
404	struct xfrm_algo_desc *calg_desc;
405
406	err = -EINVAL;
407	if (!x->calg)
408		goto out;
409
410	if (x->encap)
411		goto out;
412
413	err = -ENOMEM;
414	ipcd = kzalloc(sizeof(*ipcd), GFP_KERNEL);
415	if (!ipcd)
416		goto out;
417
418	x->props.header_len = 0;
419	if (x->props.mode)
420		x->props.header_len += sizeof(struct iphdr);
421
422	mutex_lock(&ipcomp_resource_mutex);
423	if (!ipcomp_alloc_scratches())
424		goto error;
425
426	ipcd->tfms = ipcomp_alloc_tfms(x->calg->alg_name);
427	if (!ipcd->tfms)
428		goto error;
429	mutex_unlock(&ipcomp_resource_mutex);
430
431	if (x->props.mode) {
432		err = ipcomp_tunnel_attach(x);
433		if (err)
434			goto error_tunnel;
435	}
436
437	calg_desc = xfrm_calg_get_byname(x->calg->alg_name, 0);
438	BUG_ON(!calg_desc);
439	ipcd->threshold = calg_desc->uinfo.comp.threshold;
440	x->data = ipcd;
441	err = 0;
442out:
443	return err;
444
445error_tunnel:
446	mutex_lock(&ipcomp_resource_mutex);
447error:
448	ipcomp_free_data(ipcd);
449	mutex_unlock(&ipcomp_resource_mutex);
450	kfree(ipcd);
451	goto out;
452}
453
454static struct xfrm_type ipcomp_type = {
455	.description	= "IPCOMP4",
456	.owner		= THIS_MODULE,
457	.proto	     	= IPPROTO_COMP,
458	.init_state	= ipcomp_init_state,
459	.destructor	= ipcomp_destroy,
460	.input		= ipcomp_input,
461	.output		= ipcomp_output
462};
463
464static struct net_protocol ipcomp4_protocol = {
465	.handler	=	xfrm4_rcv,
466	.err_handler	=	ipcomp4_err,
467	.no_policy	=	1,
468};
469
470static int __init ipcomp4_init(void)
471{
472	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
473		printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
474		return -EAGAIN;
475	}
476	if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
477		printk(KERN_INFO "ipcomp init: can't add protocol\n");
478		xfrm_unregister_type(&ipcomp_type, AF_INET);
479		return -EAGAIN;
480	}
481	return 0;
482}
483
484static void __exit ipcomp4_fini(void)
485{
486	if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
487		printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
488	if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
489		printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
490}
491
492module_init(ipcomp4_init);
493module_exit(ipcomp4_fini);
494
495MODULE_LICENSE("GPL");
496MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
497MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
498
499