ipcomp.c revision e905a9edab7f4f14f9213b52234e4a346c690911 
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 == XFRM_MODE_TUNNEL)
180		ip_send_check(iph);
181	return 0;
182}
183
184static void ipcomp4_err(struct sk_buff *skb, u32 info)
185{
186	__be32 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	u8 mode = XFRM_MODE_TUNNEL;
210
211	t = xfrm_state_alloc();
212	if (t == NULL)
213		goto out;
214
215	t->id.proto = IPPROTO_IPIP;
216	t->id.spi = x->props.saddr.a4;
217	t->id.daddr.a4 = x->id.daddr.a4;
218	memcpy(&t->sel, &x->sel, sizeof(t->sel));
219	t->props.family = AF_INET;
220	if (x->props.mode == XFRM_MODE_BEET)
221		mode = x->props.mode;
222	t->props.mode = mode;
223	t->props.saddr.a4 = x->props.saddr.a4;
224	t->props.flags = x->props.flags;
225
226	if (xfrm_init_state(t))
227		goto error;
228
229	atomic_set(&t->tunnel_users, 1);
230out:
231	return t;
232
233error:
234	t->km.state = XFRM_STATE_DEAD;
235	xfrm_state_put(t);
236	t = NULL;
237	goto out;
238}
239
240/*
241 * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
242 * always incremented on success.
243 */
244static int ipcomp_tunnel_attach(struct xfrm_state *x)
245{
246	int err = 0;
247	struct xfrm_state *t;
248
249	t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr.a4,
250			      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
251	if (!t) {
252		t = ipcomp_tunnel_create(x);
253		if (!t) {
254			err = -EINVAL;
255			goto out;
256		}
257		xfrm_state_insert(t);
258		xfrm_state_hold(t);
259	}
260	x->tunnel = t;
261	atomic_inc(&t->tunnel_users);
262out:
263	return err;
264}
265
266static void ipcomp_free_scratches(void)
267{
268	int i;
269	void **scratches;
270
271	if (--ipcomp_scratch_users)
272		return;
273
274	scratches = ipcomp_scratches;
275	if (!scratches)
276		return;
277
278	for_each_possible_cpu(i)
279		vfree(*per_cpu_ptr(scratches, i));
280
281	free_percpu(scratches);
282}
283
284static void **ipcomp_alloc_scratches(void)
285{
286	int i;
287	void **scratches;
288
289	if (ipcomp_scratch_users++)
290		return ipcomp_scratches;
291
292	scratches = alloc_percpu(void *);
293	if (!scratches)
294		return NULL;
295
296	ipcomp_scratches = scratches;
297
298	for_each_possible_cpu(i) {
299		void *scratch = vmalloc(IPCOMP_SCRATCH_SIZE);
300		if (!scratch)
301			return NULL;
302		*per_cpu_ptr(scratches, i) = scratch;
303	}
304
305	return scratches;
306}
307
308static void ipcomp_free_tfms(struct crypto_comp **tfms)
309{
310	struct ipcomp_tfms *pos;
311	int cpu;
312
313	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
314		if (pos->tfms == tfms)
315			break;
316	}
317
318	BUG_TRAP(pos);
319
320	if (--pos->users)
321		return;
322
323	list_del(&pos->list);
324	kfree(pos);
325
326	if (!tfms)
327		return;
328
329	for_each_possible_cpu(cpu) {
330		struct crypto_comp *tfm = *per_cpu_ptr(tfms, cpu);
331		crypto_free_comp(tfm);
332	}
333	free_percpu(tfms);
334}
335
336static struct crypto_comp **ipcomp_alloc_tfms(const char *alg_name)
337{
338	struct ipcomp_tfms *pos;
339	struct crypto_comp **tfms;
340	int cpu;
341
342	/* This can be any valid CPU ID so we don't need locking. */
343	cpu = raw_smp_processor_id();
344
345	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
346		struct crypto_comp *tfm;
347
348		tfms = pos->tfms;
349		tfm = *per_cpu_ptr(tfms, cpu);
350
351		if (!strcmp(crypto_comp_name(tfm), alg_name)) {
352			pos->users++;
353			return tfms;
354		}
355	}
356
357	pos = kmalloc(sizeof(*pos), GFP_KERNEL);
358	if (!pos)
359		return NULL;
360
361	pos->users = 1;
362	INIT_LIST_HEAD(&pos->list);
363	list_add(&pos->list, &ipcomp_tfms_list);
364
365	pos->tfms = tfms = alloc_percpu(struct crypto_comp *);
366	if (!tfms)
367		goto error;
368
369	for_each_possible_cpu(cpu) {
370		struct crypto_comp *tfm = crypto_alloc_comp(alg_name, 0,
371							    CRYPTO_ALG_ASYNC);
372		if (!tfm)
373			goto error;
374		*per_cpu_ptr(tfms, cpu) = tfm;
375	}
376
377	return tfms;
378
379error:
380	ipcomp_free_tfms(tfms);
381	return NULL;
382}
383
384static void ipcomp_free_data(struct ipcomp_data *ipcd)
385{
386	if (ipcd->tfms)
387		ipcomp_free_tfms(ipcd->tfms);
388	ipcomp_free_scratches();
389}
390
391static void ipcomp_destroy(struct xfrm_state *x)
392{
393	struct ipcomp_data *ipcd = x->data;
394	if (!ipcd)
395		return;
396	xfrm_state_delete_tunnel(x);
397	mutex_lock(&ipcomp_resource_mutex);
398	ipcomp_free_data(ipcd);
399	mutex_unlock(&ipcomp_resource_mutex);
400	kfree(ipcd);
401}
402
403static int ipcomp_init_state(struct xfrm_state *x)
404{
405	int err;
406	struct ipcomp_data *ipcd;
407	struct xfrm_algo_desc *calg_desc;
408
409	err = -EINVAL;
410	if (!x->calg)
411		goto out;
412
413	if (x->encap)
414		goto out;
415
416	err = -ENOMEM;
417	ipcd = kzalloc(sizeof(*ipcd), GFP_KERNEL);
418	if (!ipcd)
419		goto out;
420
421	x->props.header_len = 0;
422	if (x->props.mode == XFRM_MODE_TUNNEL)
423		x->props.header_len += sizeof(struct iphdr);
424
425	mutex_lock(&ipcomp_resource_mutex);
426	if (!ipcomp_alloc_scratches())
427		goto error;
428
429	ipcd->tfms = ipcomp_alloc_tfms(x->calg->alg_name);
430	if (!ipcd->tfms)
431		goto error;
432	mutex_unlock(&ipcomp_resource_mutex);
433
434	if (x->props.mode == XFRM_MODE_TUNNEL) {
435		err = ipcomp_tunnel_attach(x);
436		if (err)
437			goto error_tunnel;
438	}
439
440	calg_desc = xfrm_calg_get_byname(x->calg->alg_name, 0);
441	BUG_ON(!calg_desc);
442	ipcd->threshold = calg_desc->uinfo.comp.threshold;
443	x->data = ipcd;
444	err = 0;
445out:
446	return err;
447
448error_tunnel:
449	mutex_lock(&ipcomp_resource_mutex);
450error:
451	ipcomp_free_data(ipcd);
452	mutex_unlock(&ipcomp_resource_mutex);
453	kfree(ipcd);
454	goto out;
455}
456
457static struct xfrm_type ipcomp_type = {
458	.description	= "IPCOMP4",
459	.owner		= THIS_MODULE,
460	.proto	     	= IPPROTO_COMP,
461	.init_state	= ipcomp_init_state,
462	.destructor	= ipcomp_destroy,
463	.input		= ipcomp_input,
464	.output		= ipcomp_output
465};
466
467static struct net_protocol ipcomp4_protocol = {
468	.handler	=	xfrm4_rcv,
469	.err_handler	=	ipcomp4_err,
470	.no_policy	=	1,
471};
472
473static int __init ipcomp4_init(void)
474{
475	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
476		printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
477		return -EAGAIN;
478	}
479	if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
480		printk(KERN_INFO "ipcomp init: can't add protocol\n");
481		xfrm_unregister_type(&ipcomp_type, AF_INET);
482		return -EAGAIN;
483	}
484	return 0;
485}
486
487static void __exit ipcomp4_fini(void)
488{
489	if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
490		printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
491	if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
492		printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
493}
494
495module_init(ipcomp4_init);
496module_exit(ipcomp4_fini);
497
498MODULE_LICENSE("GPL");
499MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
500MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
501
502