ipcomp.c revision 6fc8b9e7c60d4a3d4d7f1189f74e37651f5610e6 
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 <net/ip.h>
28#include <net/xfrm.h>
29#include <net/icmp.h>
30#include <net/ipcomp.h>
31
32struct ipcomp_tfms {
33	struct list_head list;
34	struct crypto_tfm **tfms;
35	int users;
36};
37
38static DECLARE_MUTEX(ipcomp_resource_sem);
39static void **ipcomp_scratches;
40static int ipcomp_scratch_users;
41static LIST_HEAD(ipcomp_tfms_list);
42
43static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
44{
45	int err, plen, dlen;
46	struct iphdr *iph;
47	struct ipcomp_data *ipcd = x->data;
48	u8 *start, *scratch;
49	struct crypto_tfm *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_put(skb, dlen - plen);
74	memcpy(skb->data, scratch, dlen);
75	iph = skb->nh.iph;
76	iph->tot_len = htons(dlen + iph->ihl * 4);
77out:
78	put_cpu();
79	return err;
80}
81
82static int ipcomp_input(struct xfrm_state *x,
83                        struct xfrm_decap_state *decap, struct sk_buff *skb)
84{
85	u8 nexthdr;
86	int err = 0;
87	struct iphdr *iph;
88	union {
89		struct iphdr	iph;
90		char 		buf[60];
91	} tmp_iph;
92
93
94	if ((skb_is_nonlinear(skb) || skb_cloned(skb)) &&
95	    skb_linearize(skb, GFP_ATOMIC) != 0) {
96	    	err = -ENOMEM;
97	    	goto out;
98	}
99
100	skb->ip_summed = CHECKSUM_NONE;
101
102	/* Remove ipcomp header and decompress original payload */
103	iph = skb->nh.iph;
104	memcpy(&tmp_iph, iph, iph->ihl * 4);
105	nexthdr = *(u8 *)skb->data;
106	skb_pull(skb, sizeof(struct ip_comp_hdr));
107	skb->nh.raw += sizeof(struct ip_comp_hdr);
108	memcpy(skb->nh.raw, &tmp_iph, tmp_iph.iph.ihl * 4);
109	iph = skb->nh.iph;
110	iph->tot_len = htons(ntohs(iph->tot_len) - sizeof(struct ip_comp_hdr));
111	iph->protocol = nexthdr;
112	skb->h.raw = skb->data;
113	err = ipcomp_decompress(x, skb);
114
115out:
116	return err;
117}
118
119static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
120{
121	int err, plen, dlen, ihlen;
122	struct iphdr *iph = skb->nh.iph;
123	struct ipcomp_data *ipcd = x->data;
124	u8 *start, *scratch;
125	struct crypto_tfm *tfm;
126	int cpu;
127
128	ihlen = iph->ihl * 4;
129	plen = skb->len - ihlen;
130	dlen = IPCOMP_SCRATCH_SIZE;
131	start = skb->data + ihlen;
132
133	cpu = get_cpu();
134	scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
135	tfm = *per_cpu_ptr(ipcd->tfms, cpu);
136
137	err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);
138	if (err)
139		goto out;
140
141	if ((dlen + sizeof(struct ip_comp_hdr)) >= plen) {
142		err = -EMSGSIZE;
143		goto out;
144	}
145
146	memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
147	put_cpu();
148
149	pskb_trim(skb, ihlen + dlen + sizeof(struct ip_comp_hdr));
150	return 0;
151
152out:
153	put_cpu();
154	return err;
155}
156
157static int ipcomp_output(struct xfrm_state *x, struct sk_buff *skb)
158{
159	int err;
160	struct iphdr *iph;
161	struct ip_comp_hdr *ipch;
162	struct ipcomp_data *ipcd = x->data;
163	int hdr_len = 0;
164
165	iph = skb->nh.iph;
166	iph->tot_len = htons(skb->len);
167	hdr_len = iph->ihl * 4;
168	if ((skb->len - hdr_len) < ipcd->threshold) {
169		/* Don't bother compressing */
170		goto out_ok;
171	}
172
173	if ((skb_is_nonlinear(skb) || skb_cloned(skb)) &&
174	    skb_linearize(skb, GFP_ATOMIC) != 0) {
175		goto out_ok;
176	}
177
178	err = ipcomp_compress(x, skb);
179	iph = skb->nh.iph;
180
181	if (err) {
182		goto out_ok;
183	}
184
185	/* Install ipcomp header, convert into ipcomp datagram. */
186	iph->tot_len = htons(skb->len);
187	ipch = (struct ip_comp_hdr *)((char *)iph + iph->ihl * 4);
188	ipch->nexthdr = iph->protocol;
189	ipch->flags = 0;
190	ipch->cpi = htons((u16 )ntohl(x->id.spi));
191	iph->protocol = IPPROTO_COMP;
192	ip_send_check(iph);
193	return 0;
194
195out_ok:
196	if (x->props.mode)
197		ip_send_check(iph);
198	return 0;
199}
200
201static void ipcomp4_err(struct sk_buff *skb, u32 info)
202{
203	u32 spi;
204	struct iphdr *iph = (struct iphdr *)skb->data;
205	struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
206	struct xfrm_state *x;
207
208	if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
209	    skb->h.icmph->code != ICMP_FRAG_NEEDED)
210		return;
211
212	spi = ntohl(ntohs(ipch->cpi));
213	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr,
214	                      spi, IPPROTO_COMP, AF_INET);
215	if (!x)
216		return;
217	NETDEBUG(printk(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%u.%u.%u.%u\n",
218	       spi, NIPQUAD(iph->daddr)));
219	xfrm_state_put(x);
220}
221
222/* We always hold one tunnel user reference to indicate a tunnel */
223static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
224{
225	struct xfrm_state *t;
226
227	t = xfrm_state_alloc();
228	if (t == NULL)
229		goto out;
230
231	t->id.proto = IPPROTO_IPIP;
232	t->id.spi = x->props.saddr.a4;
233	t->id.daddr.a4 = x->id.daddr.a4;
234	memcpy(&t->sel, &x->sel, sizeof(t->sel));
235	t->props.family = AF_INET;
236	t->props.mode = 1;
237	t->props.saddr.a4 = x->props.saddr.a4;
238	t->props.flags = x->props.flags;
239
240	if (xfrm_init_state(t))
241		goto error;
242
243	atomic_set(&t->tunnel_users, 1);
244out:
245	return t;
246
247error:
248	t->km.state = XFRM_STATE_DEAD;
249	xfrm_state_put(t);
250	t = NULL;
251	goto out;
252}
253
254/*
255 * Must be protected by xfrm_cfg_sem.  State and tunnel user references are
256 * always incremented on success.
257 */
258static int ipcomp_tunnel_attach(struct xfrm_state *x)
259{
260	int err = 0;
261	struct xfrm_state *t;
262
263	t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr.a4,
264	                      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
265	if (!t) {
266		t = ipcomp_tunnel_create(x);
267		if (!t) {
268			err = -EINVAL;
269			goto out;
270		}
271		xfrm_state_insert(t);
272		xfrm_state_hold(t);
273	}
274	x->tunnel = t;
275	atomic_inc(&t->tunnel_users);
276out:
277	return err;
278}
279
280static void ipcomp_free_scratches(void)
281{
282	int i;
283	void **scratches;
284
285	if (--ipcomp_scratch_users)
286		return;
287
288	scratches = ipcomp_scratches;
289	if (!scratches)
290		return;
291
292	for_each_cpu(i) {
293		void *scratch = *per_cpu_ptr(scratches, i);
294		if (scratch)
295			vfree(scratch);
296	}
297
298	free_percpu(scratches);
299}
300
301static void **ipcomp_alloc_scratches(void)
302{
303	int i;
304	void **scratches;
305
306	if (ipcomp_scratch_users++)
307		return ipcomp_scratches;
308
309	scratches = alloc_percpu(void *);
310	if (!scratches)
311		return NULL;
312
313	ipcomp_scratches = scratches;
314
315	for_each_cpu(i) {
316		void *scratch = vmalloc(IPCOMP_SCRATCH_SIZE);
317		if (!scratch)
318			return NULL;
319		*per_cpu_ptr(scratches, i) = scratch;
320	}
321
322	return scratches;
323}
324
325static void ipcomp_free_tfms(struct crypto_tfm **tfms)
326{
327	struct ipcomp_tfms *pos;
328	int cpu;
329
330	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
331		if (pos->tfms == tfms)
332			break;
333	}
334
335	BUG_TRAP(pos);
336
337	if (--pos->users)
338		return;
339
340	list_del(&pos->list);
341	kfree(pos);
342
343	if (!tfms)
344		return;
345
346	for_each_cpu(cpu) {
347		struct crypto_tfm *tfm = *per_cpu_ptr(tfms, cpu);
348		if (tfm)
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_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	down(&ipcomp_resource_sem);
415	ipcomp_free_data(ipcd);
416	up(&ipcomp_resource_sem);
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	down(&ipcomp_resource_sem);
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	up(&ipcomp_resource_sem);
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	down(&ipcomp_resource_sem);
468error:
469	ipcomp_free_data(ipcd);
470	up(&ipcomp_resource_sem);
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