ipcomp.c revision 2614fa59fa805cd488083c5602eb48533cdbc018 
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/semaphore.h>
18#include <linux/crypto.h>
19#include <linux/err.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 nexthdr;
78	int err = -ENOMEM;
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	ipch = (void *)skb->data;
88	nexthdr = ipch->nexthdr;
89
90	skb->transport_header = skb->network_header + sizeof(*ipch);
91	__skb_pull(skb, sizeof(*ipch));
92	err = ipcomp_decompress(x, skb);
93	if (err)
94		goto out;
95
96	err = nexthdr;
97
98out:
99	return err;
100}
101
102static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
103{
104	struct ipcomp_data *ipcd = x->data;
105	const int plen = skb->len;
106	int dlen = IPCOMP_SCRATCH_SIZE;
107	u8 *start = skb->data;
108	const int cpu = get_cpu();
109	u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
110	struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu);
111	int err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);
112
113	if (err)
114		goto out;
115
116	if ((dlen + sizeof(struct ip_comp_hdr)) >= plen) {
117		err = -EMSGSIZE;
118		goto out;
119	}
120
121	memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
122	put_cpu();
123
124	pskb_trim(skb, dlen + sizeof(struct ip_comp_hdr));
125	return 0;
126
127out:
128	put_cpu();
129	return err;
130}
131
132static int ipcomp_output(struct xfrm_state *x, struct sk_buff *skb)
133{
134	int err;
135	struct ip_comp_hdr *ipch;
136	struct ipcomp_data *ipcd = x->data;
137
138	if (skb->len < ipcd->threshold) {
139		/* Don't bother compressing */
140		goto out_ok;
141	}
142
143	if (skb_linearize_cow(skb))
144		goto out_ok;
145
146	err = ipcomp_compress(x, skb);
147
148	if (err) {
149		goto out_ok;
150	}
151
152	/* Install ipcomp header, convert into ipcomp datagram. */
153	ipch = ip_comp_hdr(skb);
154	ipch->nexthdr = *skb_mac_header(skb);
155	ipch->flags = 0;
156	ipch->cpi = htons((u16 )ntohl(x->id.spi));
157	*skb_mac_header(skb) = IPPROTO_COMP;
158out_ok:
159	skb_push(skb, -skb_network_offset(skb));
160	return 0;
161}
162
163static void ipcomp4_err(struct sk_buff *skb, u32 info)
164{
165	__be32 spi;
166	struct iphdr *iph = (struct iphdr *)skb->data;
167	struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
168	struct xfrm_state *x;
169
170	if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
171	    icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
172		return;
173
174	spi = htonl(ntohs(ipch->cpi));
175	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr,
176			      spi, IPPROTO_COMP, AF_INET);
177	if (!x)
178		return;
179	NETDEBUG(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%u.%u.%u.%u\n",
180		 spi, NIPQUAD(iph->daddr));
181	xfrm_state_put(x);
182}
183
184/* We always hold one tunnel user reference to indicate a tunnel */
185static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
186{
187	struct xfrm_state *t;
188
189	t = xfrm_state_alloc();
190	if (t == NULL)
191		goto out;
192
193	t->id.proto = IPPROTO_IPIP;
194	t->id.spi = x->props.saddr.a4;
195	t->id.daddr.a4 = x->id.daddr.a4;
196	memcpy(&t->sel, &x->sel, sizeof(t->sel));
197	t->props.family = AF_INET;
198	t->props.mode = x->props.mode;
199	t->props.saddr.a4 = x->props.saddr.a4;
200	t->props.flags = x->props.flags;
201
202	if (xfrm_init_state(t))
203		goto error;
204
205	atomic_set(&t->tunnel_users, 1);
206out:
207	return t;
208
209error:
210	t->km.state = XFRM_STATE_DEAD;
211	xfrm_state_put(t);
212	t = NULL;
213	goto out;
214}
215
216/*
217 * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
218 * always incremented on success.
219 */
220static int ipcomp_tunnel_attach(struct xfrm_state *x)
221{
222	int err = 0;
223	struct xfrm_state *t;
224
225	t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr.a4,
226			      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
227	if (!t) {
228		t = ipcomp_tunnel_create(x);
229		if (!t) {
230			err = -EINVAL;
231			goto out;
232		}
233		xfrm_state_insert(t);
234		xfrm_state_hold(t);
235	}
236	x->tunnel = t;
237	atomic_inc(&t->tunnel_users);
238out:
239	return err;
240}
241
242static void ipcomp_free_scratches(void)
243{
244	int i;
245	void **scratches;
246
247	if (--ipcomp_scratch_users)
248		return;
249
250	scratches = ipcomp_scratches;
251	if (!scratches)
252		return;
253
254	for_each_possible_cpu(i)
255		vfree(*per_cpu_ptr(scratches, i));
256
257	free_percpu(scratches);
258}
259
260static void **ipcomp_alloc_scratches(void)
261{
262	int i;
263	void **scratches;
264
265	if (ipcomp_scratch_users++)
266		return ipcomp_scratches;
267
268	scratches = alloc_percpu(void *);
269	if (!scratches)
270		return NULL;
271
272	ipcomp_scratches = scratches;
273
274	for_each_possible_cpu(i) {
275		void *scratch = vmalloc(IPCOMP_SCRATCH_SIZE);
276		if (!scratch)
277			return NULL;
278		*per_cpu_ptr(scratches, i) = scratch;
279	}
280
281	return scratches;
282}
283
284static void ipcomp_free_tfms(struct crypto_comp **tfms)
285{
286	struct ipcomp_tfms *pos;
287	int cpu;
288
289	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
290		if (pos->tfms == tfms)
291			break;
292	}
293
294	BUG_TRAP(pos);
295
296	if (--pos->users)
297		return;
298
299	list_del(&pos->list);
300	kfree(pos);
301
302	if (!tfms)
303		return;
304
305	for_each_possible_cpu(cpu) {
306		struct crypto_comp *tfm = *per_cpu_ptr(tfms, cpu);
307		crypto_free_comp(tfm);
308	}
309	free_percpu(tfms);
310}
311
312static struct crypto_comp **ipcomp_alloc_tfms(const char *alg_name)
313{
314	struct ipcomp_tfms *pos;
315	struct crypto_comp **tfms;
316	int cpu;
317
318	/* This can be any valid CPU ID so we don't need locking. */
319	cpu = raw_smp_processor_id();
320
321	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
322		struct crypto_comp *tfm;
323
324		tfms = pos->tfms;
325		tfm = *per_cpu_ptr(tfms, cpu);
326
327		if (!strcmp(crypto_comp_name(tfm), alg_name)) {
328			pos->users++;
329			return tfms;
330		}
331	}
332
333	pos = kmalloc(sizeof(*pos), GFP_KERNEL);
334	if (!pos)
335		return NULL;
336
337	pos->users = 1;
338	INIT_LIST_HEAD(&pos->list);
339	list_add(&pos->list, &ipcomp_tfms_list);
340
341	pos->tfms = tfms = alloc_percpu(struct crypto_comp *);
342	if (!tfms)
343		goto error;
344
345	for_each_possible_cpu(cpu) {
346		struct crypto_comp *tfm = crypto_alloc_comp(alg_name, 0,
347							    CRYPTO_ALG_ASYNC);
348		if (IS_ERR(tfm))
349			goto error;
350		*per_cpu_ptr(tfms, cpu) = tfm;
351	}
352
353	return tfms;
354
355error:
356	ipcomp_free_tfms(tfms);
357	return NULL;
358}
359
360static void ipcomp_free_data(struct ipcomp_data *ipcd)
361{
362	if (ipcd->tfms)
363		ipcomp_free_tfms(ipcd->tfms);
364	ipcomp_free_scratches();
365}
366
367static void ipcomp_destroy(struct xfrm_state *x)
368{
369	struct ipcomp_data *ipcd = x->data;
370	if (!ipcd)
371		return;
372	xfrm_state_delete_tunnel(x);
373	mutex_lock(&ipcomp_resource_mutex);
374	ipcomp_free_data(ipcd);
375	mutex_unlock(&ipcomp_resource_mutex);
376	kfree(ipcd);
377}
378
379static int ipcomp_init_state(struct xfrm_state *x)
380{
381	int err;
382	struct ipcomp_data *ipcd;
383	struct xfrm_algo_desc *calg_desc;
384
385	err = -EINVAL;
386	if (!x->calg)
387		goto out;
388
389	if (x->encap)
390		goto out;
391
392	x->props.header_len = 0;
393	switch (x->props.mode) {
394	case XFRM_MODE_TRANSPORT:
395		break;
396	case XFRM_MODE_TUNNEL:
397		x->props.header_len += sizeof(struct iphdr);
398		break;
399	default:
400		goto out;
401	}
402
403	err = -ENOMEM;
404	ipcd = kzalloc(sizeof(*ipcd), GFP_KERNEL);
405	if (!ipcd)
406		goto out;
407
408	mutex_lock(&ipcomp_resource_mutex);
409	if (!ipcomp_alloc_scratches())
410		goto error;
411
412	ipcd->tfms = ipcomp_alloc_tfms(x->calg->alg_name);
413	if (!ipcd->tfms)
414		goto error;
415	mutex_unlock(&ipcomp_resource_mutex);
416
417	if (x->props.mode == XFRM_MODE_TUNNEL) {
418		err = ipcomp_tunnel_attach(x);
419		if (err)
420			goto error_tunnel;
421	}
422
423	calg_desc = xfrm_calg_get_byname(x->calg->alg_name, 0);
424	BUG_ON(!calg_desc);
425	ipcd->threshold = calg_desc->uinfo.comp.threshold;
426	x->data = ipcd;
427	err = 0;
428out:
429	return err;
430
431error_tunnel:
432	mutex_lock(&ipcomp_resource_mutex);
433error:
434	ipcomp_free_data(ipcd);
435	mutex_unlock(&ipcomp_resource_mutex);
436	kfree(ipcd);
437	goto out;
438}
439
440static struct xfrm_type ipcomp_type = {
441	.description	= "IPCOMP4",
442	.owner		= THIS_MODULE,
443	.proto	     	= IPPROTO_COMP,
444	.init_state	= ipcomp_init_state,
445	.destructor	= ipcomp_destroy,
446	.input		= ipcomp_input,
447	.output		= ipcomp_output
448};
449
450static struct net_protocol ipcomp4_protocol = {
451	.handler	=	xfrm4_rcv,
452	.err_handler	=	ipcomp4_err,
453	.no_policy	=	1,
454};
455
456static int __init ipcomp4_init(void)
457{
458	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
459		printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
460		return -EAGAIN;
461	}
462	if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
463		printk(KERN_INFO "ipcomp init: can't add protocol\n");
464		xfrm_unregister_type(&ipcomp_type, AF_INET);
465		return -EAGAIN;
466	}
467	return 0;
468}
469
470static void __exit ipcomp4_fini(void)
471{
472	if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
473		printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
474	if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
475		printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
476}
477
478module_init(ipcomp4_init);
479module_exit(ipcomp4_fini);
480
481MODULE_LICENSE("GPL");
482MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
483MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
484
485MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);
486