ipcomp.c revision 6f912042256c12b0927438122594f5379b364f5d 
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/config.h>
17#include <linux/module.h>
18#include <asm/scatterlist.h>
19#include <asm/semaphore.h>
20#include <linux/crypto.h>
21#include <linux/pfkeyv2.h>
22#include <linux/percpu.h>
23#include <linux/smp.h>
24#include <linux/list.h>
25#include <linux/vmalloc.h>
26#include <linux/rtnetlink.h>
27#include <linux/mutex.h>
28#include <net/ip.h>
29#include <net/xfrm.h>
30#include <net/icmp.h>
31#include <net/ipcomp.h>
32#include <net/protocol.h>
33
34struct ipcomp_tfms {
35	struct list_head list;
36	struct crypto_tfm **tfms;
37	int users;
38};
39
40static DEFINE_MUTEX(ipcomp_resource_mutex);
41static void **ipcomp_scratches;
42static int ipcomp_scratch_users;
43static LIST_HEAD(ipcomp_tfms_list);
44
45static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
46{
47	int err, plen, dlen;
48	struct iphdr *iph;
49	struct ipcomp_data *ipcd = x->data;
50	u8 *start, *scratch;
51	struct crypto_tfm *tfm;
52	int cpu;
53
54	plen = skb->len;
55	dlen = IPCOMP_SCRATCH_SIZE;
56	start = skb->data;
57
58	cpu = get_cpu();
59	scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
60	tfm = *per_cpu_ptr(ipcd->tfms, cpu);
61
62	err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen);
63	if (err)
64		goto out;
65
66	if (dlen < (plen + sizeof(struct ip_comp_hdr))) {
67		err = -EINVAL;
68		goto out;
69	}
70
71	err = pskb_expand_head(skb, 0, dlen - plen, GFP_ATOMIC);
72	if (err)
73		goto out;
74
75	skb_put(skb, dlen - plen);
76	memcpy(skb->data, scratch, dlen);
77	iph = skb->nh.iph;
78	iph->tot_len = htons(dlen + iph->ihl * 4);
79out:
80	put_cpu();
81	return err;
82}
83
84static int ipcomp_input(struct xfrm_state *x, struct sk_buff *skb)
85{
86	u8 nexthdr;
87	int err = 0;
88	struct iphdr *iph;
89	union {
90		struct iphdr	iph;
91		char 		buf[60];
92	} tmp_iph;
93
94
95	if ((skb_is_nonlinear(skb) || skb_cloned(skb)) &&
96	    skb_linearize(skb, GFP_ATOMIC) != 0) {
97	    	err = -ENOMEM;
98	    	goto out;
99	}
100
101	skb->ip_summed = CHECKSUM_NONE;
102
103	/* Remove ipcomp header and decompress original payload */
104	iph = skb->nh.iph;
105	memcpy(&tmp_iph, iph, iph->ihl * 4);
106	nexthdr = *(u8 *)skb->data;
107	skb_pull(skb, sizeof(struct ip_comp_hdr));
108	skb->nh.raw += sizeof(struct ip_comp_hdr);
109	memcpy(skb->nh.raw, &tmp_iph, tmp_iph.iph.ihl * 4);
110	iph = skb->nh.iph;
111	iph->tot_len = htons(ntohs(iph->tot_len) - sizeof(struct ip_comp_hdr));
112	iph->protocol = nexthdr;
113	skb->h.raw = skb->data;
114	err = ipcomp_decompress(x, skb);
115
116out:
117	return err;
118}
119
120static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
121{
122	int err, plen, dlen, ihlen;
123	struct iphdr *iph = skb->nh.iph;
124	struct ipcomp_data *ipcd = x->data;
125	u8 *start, *scratch;
126	struct crypto_tfm *tfm;
127	int cpu;
128
129	ihlen = iph->ihl * 4;
130	plen = skb->len - ihlen;
131	dlen = IPCOMP_SCRATCH_SIZE;
132	start = skb->data + ihlen;
133
134	cpu = get_cpu();
135	scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
136	tfm = *per_cpu_ptr(ipcd->tfms, cpu);
137
138	err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);
139	if (err)
140		goto out;
141
142	if ((dlen + sizeof(struct ip_comp_hdr)) >= plen) {
143		err = -EMSGSIZE;
144		goto out;
145	}
146
147	memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
148	put_cpu();
149
150	pskb_trim(skb, ihlen + dlen + sizeof(struct ip_comp_hdr));
151	return 0;
152
153out:
154	put_cpu();
155	return err;
156}
157
158static int ipcomp_output(struct xfrm_state *x, struct sk_buff *skb)
159{
160	int err;
161	struct iphdr *iph;
162	struct ip_comp_hdr *ipch;
163	struct ipcomp_data *ipcd = x->data;
164	int hdr_len = 0;
165
166	iph = skb->nh.iph;
167	iph->tot_len = htons(skb->len);
168	hdr_len = iph->ihl * 4;
169	if ((skb->len - hdr_len) < ipcd->threshold) {
170		/* Don't bother compressing */
171		goto out_ok;
172	}
173
174	if ((skb_is_nonlinear(skb) || skb_cloned(skb)) &&
175	    skb_linearize(skb, GFP_ATOMIC) != 0) {
176		goto out_ok;
177	}
178
179	err = ipcomp_compress(x, skb);
180	iph = skb->nh.iph;
181
182	if (err) {
183		goto out_ok;
184	}
185
186	/* Install ipcomp header, convert into ipcomp datagram. */
187	iph->tot_len = htons(skb->len);
188	ipch = (struct ip_comp_hdr *)((char *)iph + iph->ihl * 4);
189	ipch->nexthdr = iph->protocol;
190	ipch->flags = 0;
191	ipch->cpi = htons((u16 )ntohl(x->id.spi));
192	iph->protocol = IPPROTO_COMP;
193	ip_send_check(iph);
194	return 0;
195
196out_ok:
197	if (x->props.mode)
198		ip_send_check(iph);
199	return 0;
200}
201
202static void ipcomp4_err(struct sk_buff *skb, u32 info)
203{
204	u32 spi;
205	struct iphdr *iph = (struct iphdr *)skb->data;
206	struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
207	struct xfrm_state *x;
208
209	if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
210	    skb->h.icmph->code != ICMP_FRAG_NEEDED)
211		return;
212
213	spi = ntohl(ntohs(ipch->cpi));
214	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr,
215	                      spi, IPPROTO_COMP, AF_INET);
216	if (!x)
217		return;
218	NETDEBUG(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%u.%u.%u.%u\n",
219		 spi, NIPQUAD(iph->daddr));
220	xfrm_state_put(x);
221}
222
223/* We always hold one tunnel user reference to indicate a tunnel */
224static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
225{
226	struct xfrm_state *t;
227
228	t = xfrm_state_alloc();
229	if (t == NULL)
230		goto out;
231
232	t->id.proto = IPPROTO_IPIP;
233	t->id.spi = x->props.saddr.a4;
234	t->id.daddr.a4 = x->id.daddr.a4;
235	memcpy(&t->sel, &x->sel, sizeof(t->sel));
236	t->props.family = AF_INET;
237	t->props.mode = 1;
238	t->props.saddr.a4 = x->props.saddr.a4;
239	t->props.flags = x->props.flags;
240
241	if (xfrm_init_state(t))
242		goto error;
243
244	atomic_set(&t->tunnel_users, 1);
245out:
246	return t;
247
248error:
249	t->km.state = XFRM_STATE_DEAD;
250	xfrm_state_put(t);
251	t = NULL;
252	goto out;
253}
254
255/*
256 * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
257 * always incremented on success.
258 */
259static int ipcomp_tunnel_attach(struct xfrm_state *x)
260{
261	int err = 0;
262	struct xfrm_state *t;
263
264	t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr.a4,
265	                      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
266	if (!t) {
267		t = ipcomp_tunnel_create(x);
268		if (!t) {
269			err = -EINVAL;
270			goto out;
271		}
272		xfrm_state_insert(t);
273		xfrm_state_hold(t);
274	}
275	x->tunnel = t;
276	atomic_inc(&t->tunnel_users);
277out:
278	return err;
279}
280
281static void ipcomp_free_scratches(void)
282{
283	int i;
284	void **scratches;
285
286	if (--ipcomp_scratch_users)
287		return;
288
289	scratches = ipcomp_scratches;
290	if (!scratches)
291		return;
292
293	for_each_possible_cpu(i) {
294		void *scratch = *per_cpu_ptr(scratches, i);
295		if (scratch)
296			vfree(scratch);
297	}
298
299	free_percpu(scratches);
300}
301
302static void **ipcomp_alloc_scratches(void)
303{
304	int i;
305	void **scratches;
306
307	if (ipcomp_scratch_users++)
308		return ipcomp_scratches;
309
310	scratches = alloc_percpu(void *);
311	if (!scratches)
312		return NULL;
313
314	ipcomp_scratches = scratches;
315
316	for_each_possible_cpu(i) {
317		void *scratch = vmalloc(IPCOMP_SCRATCH_SIZE);
318		if (!scratch)
319			return NULL;
320		*per_cpu_ptr(scratches, i) = scratch;
321	}
322
323	return scratches;
324}
325
326static void ipcomp_free_tfms(struct crypto_tfm **tfms)
327{
328	struct ipcomp_tfms *pos;
329	int cpu;
330
331	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
332		if (pos->tfms == tfms)
333			break;
334	}
335
336	BUG_TRAP(pos);
337
338	if (--pos->users)
339		return;
340
341	list_del(&pos->list);
342	kfree(pos);
343
344	if (!tfms)
345		return;
346
347	for_each_possible_cpu(cpu) {
348		struct crypto_tfm *tfm = *per_cpu_ptr(tfms, cpu);
349		crypto_free_tfm(tfm);
350	}
351	free_percpu(tfms);
352}
353
354static struct crypto_tfm **ipcomp_alloc_tfms(const char *alg_name)
355{
356	struct ipcomp_tfms *pos;
357	struct crypto_tfm **tfms;
358	int cpu;
359
360	/* This can be any valid CPU ID so we don't need locking. */
361	cpu = raw_smp_processor_id();
362
363	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
364		struct crypto_tfm *tfm;
365
366		tfms = pos->tfms;
367		tfm = *per_cpu_ptr(tfms, cpu);
368
369		if (!strcmp(crypto_tfm_alg_name(tfm), alg_name)) {
370			pos->users++;
371			return tfms;
372		}
373	}
374
375	pos = kmalloc(sizeof(*pos), GFP_KERNEL);
376	if (!pos)
377		return NULL;
378
379	pos->users = 1;
380	INIT_LIST_HEAD(&pos->list);
381	list_add(&pos->list, &ipcomp_tfms_list);
382
383	pos->tfms = tfms = alloc_percpu(struct crypto_tfm *);
384	if (!tfms)
385		goto error;
386
387	for_each_possible_cpu(cpu) {
388		struct crypto_tfm *tfm = crypto_alloc_tfm(alg_name, 0);
389		if (!tfm)
390			goto error;
391		*per_cpu_ptr(tfms, cpu) = tfm;
392	}
393
394	return tfms;
395
396error:
397	ipcomp_free_tfms(tfms);
398	return NULL;
399}
400
401static void ipcomp_free_data(struct ipcomp_data *ipcd)
402{
403	if (ipcd->tfms)
404		ipcomp_free_tfms(ipcd->tfms);
405	ipcomp_free_scratches();
406}
407
408static void ipcomp_destroy(struct xfrm_state *x)
409{
410	struct ipcomp_data *ipcd = x->data;
411	if (!ipcd)
412		return;
413	xfrm_state_delete_tunnel(x);
414	mutex_lock(&ipcomp_resource_mutex);
415	ipcomp_free_data(ipcd);
416	mutex_unlock(&ipcomp_resource_mutex);
417	kfree(ipcd);
418}
419
420static int ipcomp_init_state(struct xfrm_state *x)
421{
422	int err;
423	struct ipcomp_data *ipcd;
424	struct xfrm_algo_desc *calg_desc;
425
426	err = -EINVAL;
427	if (!x->calg)
428		goto out;
429
430	if (x->encap)
431		goto out;
432
433	err = -ENOMEM;
434	ipcd = kmalloc(sizeof(*ipcd), GFP_KERNEL);
435	if (!ipcd)
436		goto out;
437
438	memset(ipcd, 0, sizeof(*ipcd));
439	x->props.header_len = 0;
440	if (x->props.mode)
441		x->props.header_len += sizeof(struct iphdr);
442
443	mutex_lock(&ipcomp_resource_mutex);
444	if (!ipcomp_alloc_scratches())
445		goto error;
446
447	ipcd->tfms = ipcomp_alloc_tfms(x->calg->alg_name);
448	if (!ipcd->tfms)
449		goto error;
450	mutex_unlock(&ipcomp_resource_mutex);
451
452	if (x->props.mode) {
453		err = ipcomp_tunnel_attach(x);
454		if (err)
455			goto error_tunnel;
456	}
457
458	calg_desc = xfrm_calg_get_byname(x->calg->alg_name, 0);
459	BUG_ON(!calg_desc);
460	ipcd->threshold = calg_desc->uinfo.comp.threshold;
461	x->data = ipcd;
462	err = 0;
463out:
464	return err;
465
466error_tunnel:
467	mutex_lock(&ipcomp_resource_mutex);
468error:
469	ipcomp_free_data(ipcd);
470	mutex_unlock(&ipcomp_resource_mutex);
471	kfree(ipcd);
472	goto out;
473}
474
475static struct xfrm_type ipcomp_type = {
476	.description	= "IPCOMP4",
477	.owner		= THIS_MODULE,
478	.proto	     	= IPPROTO_COMP,
479	.init_state	= ipcomp_init_state,
480	.destructor	= ipcomp_destroy,
481	.input		= ipcomp_input,
482	.output		= ipcomp_output
483};
484
485static struct net_protocol ipcomp4_protocol = {
486	.handler	=	xfrm4_rcv,
487	.err_handler	=	ipcomp4_err,
488	.no_policy	=	1,
489};
490
491static int __init ipcomp4_init(void)
492{
493	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
494		printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
495		return -EAGAIN;
496	}
497	if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
498		printk(KERN_INFO "ipcomp init: can't add protocol\n");
499		xfrm_unregister_type(&ipcomp_type, AF_INET);
500		return -EAGAIN;
501	}
502	return 0;
503}
504
505static void __exit ipcomp4_fini(void)
506{
507	if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
508		printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
509	if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
510		printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
511}
512
513module_init(ipcomp4_init);
514module_exit(ipcomp4_fini);
515
516MODULE_LICENSE("GPL");
517MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
518MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
519
520