ipcomp.c revision b0e380b1d8a8e0aca215df97702f99815f05c094 
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	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	memcpy(skb->data, 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 err = -ENOMEM;
78	struct iphdr *iph;
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	iph = ip_hdr(skb);
88	ipch = (void *)skb->data;
89	iph->protocol = ipch->nexthdr;
90	skb->transport_header = skb->network_header + sizeof(*ipch);
91	__skb_pull(skb, sizeof(*ipch));
92	err = ipcomp_decompress(x, skb);
93
94out:
95	return err;
96}
97
98static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
99{
100	struct ipcomp_data *ipcd = x->data;
101	const int ihlen = ip_hdrlen(skb);
102	const int plen = skb->len - ihlen;
103	int dlen = IPCOMP_SCRATCH_SIZE;
104	u8 *start = skb->data + ihlen;
105	const int cpu = get_cpu();
106	u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
107	struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu);
108	int err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);
109
110	if (err)
111		goto out;
112
113	if ((dlen + sizeof(struct ip_comp_hdr)) >= plen) {
114		err = -EMSGSIZE;
115		goto out;
116	}
117
118	memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
119	put_cpu();
120
121	pskb_trim(skb, ihlen + dlen + sizeof(struct ip_comp_hdr));
122	return 0;
123
124out:
125	put_cpu();
126	return err;
127}
128
129static int ipcomp_output(struct xfrm_state *x, struct sk_buff *skb)
130{
131	int err;
132	struct ip_comp_hdr *ipch;
133	struct ipcomp_data *ipcd = x->data;
134	int hdr_len = 0;
135	struct iphdr *iph = ip_hdr(skb);
136
137	iph->tot_len = htons(skb->len);
138	hdr_len = iph->ihl * 4;
139	if ((skb->len - hdr_len) < ipcd->threshold) {
140		/* Don't bother compressing */
141		goto out_ok;
142	}
143
144	if (skb_linearize_cow(skb))
145		goto out_ok;
146
147	err = ipcomp_compress(x, skb);
148	iph = ip_hdr(skb);
149
150	if (err) {
151		goto out_ok;
152	}
153
154	/* Install ipcomp header, convert into ipcomp datagram. */
155	iph->tot_len = htons(skb->len);
156	ipch = (struct ip_comp_hdr *)((char *)iph + iph->ihl * 4);
157	ipch->nexthdr = iph->protocol;
158	ipch->flags = 0;
159	ipch->cpi = htons((u16 )ntohl(x->id.spi));
160	iph->protocol = IPPROTO_COMP;
161	ip_send_check(iph);
162	return 0;
163
164out_ok:
165	if (x->props.mode == XFRM_MODE_TUNNEL)
166		ip_send_check(iph);
167	return 0;
168}
169
170static void ipcomp4_err(struct sk_buff *skb, u32 info)
171{
172	__be32 spi;
173	struct iphdr *iph = (struct iphdr *)skb->data;
174	struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
175	struct xfrm_state *x;
176
177	if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
178	    icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
179		return;
180
181	spi = htonl(ntohs(ipch->cpi));
182	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr,
183			      spi, IPPROTO_COMP, AF_INET);
184	if (!x)
185		return;
186	NETDEBUG(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%u.%u.%u.%u\n",
187		 spi, NIPQUAD(iph->daddr));
188	xfrm_state_put(x);
189}
190
191/* We always hold one tunnel user reference to indicate a tunnel */
192static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
193{
194	struct xfrm_state *t;
195	u8 mode = XFRM_MODE_TUNNEL;
196
197	t = xfrm_state_alloc();
198	if (t == NULL)
199		goto out;
200
201	t->id.proto = IPPROTO_IPIP;
202	t->id.spi = x->props.saddr.a4;
203	t->id.daddr.a4 = x->id.daddr.a4;
204	memcpy(&t->sel, &x->sel, sizeof(t->sel));
205	t->props.family = AF_INET;
206	if (x->props.mode == XFRM_MODE_BEET)
207		mode = x->props.mode;
208	t->props.mode = mode;
209	t->props.saddr.a4 = x->props.saddr.a4;
210	t->props.flags = x->props.flags;
211
212	if (xfrm_init_state(t))
213		goto error;
214
215	atomic_set(&t->tunnel_users, 1);
216out:
217	return t;
218
219error:
220	t->km.state = XFRM_STATE_DEAD;
221	xfrm_state_put(t);
222	t = NULL;
223	goto out;
224}
225
226/*
227 * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are
228 * always incremented on success.
229 */
230static int ipcomp_tunnel_attach(struct xfrm_state *x)
231{
232	int err = 0;
233	struct xfrm_state *t;
234
235	t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr.a4,
236			      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);
237	if (!t) {
238		t = ipcomp_tunnel_create(x);
239		if (!t) {
240			err = -EINVAL;
241			goto out;
242		}
243		xfrm_state_insert(t);
244		xfrm_state_hold(t);
245	}
246	x->tunnel = t;
247	atomic_inc(&t->tunnel_users);
248out:
249	return err;
250}
251
252static void ipcomp_free_scratches(void)
253{
254	int i;
255	void **scratches;
256
257	if (--ipcomp_scratch_users)
258		return;
259
260	scratches = ipcomp_scratches;
261	if (!scratches)
262		return;
263
264	for_each_possible_cpu(i)
265		vfree(*per_cpu_ptr(scratches, i));
266
267	free_percpu(scratches);
268}
269
270static void **ipcomp_alloc_scratches(void)
271{
272	int i;
273	void **scratches;
274
275	if (ipcomp_scratch_users++)
276		return ipcomp_scratches;
277
278	scratches = alloc_percpu(void *);
279	if (!scratches)
280		return NULL;
281
282	ipcomp_scratches = scratches;
283
284	for_each_possible_cpu(i) {
285		void *scratch = vmalloc(IPCOMP_SCRATCH_SIZE);
286		if (!scratch)
287			return NULL;
288		*per_cpu_ptr(scratches, i) = scratch;
289	}
290
291	return scratches;
292}
293
294static void ipcomp_free_tfms(struct crypto_comp **tfms)
295{
296	struct ipcomp_tfms *pos;
297	int cpu;
298
299	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
300		if (pos->tfms == tfms)
301			break;
302	}
303
304	BUG_TRAP(pos);
305
306	if (--pos->users)
307		return;
308
309	list_del(&pos->list);
310	kfree(pos);
311
312	if (!tfms)
313		return;
314
315	for_each_possible_cpu(cpu) {
316		struct crypto_comp *tfm = *per_cpu_ptr(tfms, cpu);
317		crypto_free_comp(tfm);
318	}
319	free_percpu(tfms);
320}
321
322static struct crypto_comp **ipcomp_alloc_tfms(const char *alg_name)
323{
324	struct ipcomp_tfms *pos;
325	struct crypto_comp **tfms;
326	int cpu;
327
328	/* This can be any valid CPU ID so we don't need locking. */
329	cpu = raw_smp_processor_id();
330
331	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
332		struct crypto_comp *tfm;
333
334		tfms = pos->tfms;
335		tfm = *per_cpu_ptr(tfms, cpu);
336
337		if (!strcmp(crypto_comp_name(tfm), alg_name)) {
338			pos->users++;
339			return tfms;
340		}
341	}
342
343	pos = kmalloc(sizeof(*pos), GFP_KERNEL);
344	if (!pos)
345		return NULL;
346
347	pos->users = 1;
348	INIT_LIST_HEAD(&pos->list);
349	list_add(&pos->list, &ipcomp_tfms_list);
350
351	pos->tfms = tfms = alloc_percpu(struct crypto_comp *);
352	if (!tfms)
353		goto error;
354
355	for_each_possible_cpu(cpu) {
356		struct crypto_comp *tfm = crypto_alloc_comp(alg_name, 0,
357							    CRYPTO_ALG_ASYNC);
358		if (!tfm)
359			goto error;
360		*per_cpu_ptr(tfms, cpu) = tfm;
361	}
362
363	return tfms;
364
365error:
366	ipcomp_free_tfms(tfms);
367	return NULL;
368}
369
370static void ipcomp_free_data(struct ipcomp_data *ipcd)
371{
372	if (ipcd->tfms)
373		ipcomp_free_tfms(ipcd->tfms);
374	ipcomp_free_scratches();
375}
376
377static void ipcomp_destroy(struct xfrm_state *x)
378{
379	struct ipcomp_data *ipcd = x->data;
380	if (!ipcd)
381		return;
382	xfrm_state_delete_tunnel(x);
383	mutex_lock(&ipcomp_resource_mutex);
384	ipcomp_free_data(ipcd);
385	mutex_unlock(&ipcomp_resource_mutex);
386	kfree(ipcd);
387}
388
389static int ipcomp_init_state(struct xfrm_state *x)
390{
391	int err;
392	struct ipcomp_data *ipcd;
393	struct xfrm_algo_desc *calg_desc;
394
395	err = -EINVAL;
396	if (!x->calg)
397		goto out;
398
399	if (x->encap)
400		goto out;
401
402	err = -ENOMEM;
403	ipcd = kzalloc(sizeof(*ipcd), GFP_KERNEL);
404	if (!ipcd)
405		goto out;
406
407	x->props.header_len = 0;
408	if (x->props.mode == XFRM_MODE_TUNNEL)
409		x->props.header_len += sizeof(struct iphdr);
410
411	mutex_lock(&ipcomp_resource_mutex);
412	if (!ipcomp_alloc_scratches())
413		goto error;
414
415	ipcd->tfms = ipcomp_alloc_tfms(x->calg->alg_name);
416	if (!ipcd->tfms)
417		goto error;
418	mutex_unlock(&ipcomp_resource_mutex);
419
420	if (x->props.mode == XFRM_MODE_TUNNEL) {
421		err = ipcomp_tunnel_attach(x);
422		if (err)
423			goto error_tunnel;
424	}
425
426	calg_desc = xfrm_calg_get_byname(x->calg->alg_name, 0);
427	BUG_ON(!calg_desc);
428	ipcd->threshold = calg_desc->uinfo.comp.threshold;
429	x->data = ipcd;
430	err = 0;
431out:
432	return err;
433
434error_tunnel:
435	mutex_lock(&ipcomp_resource_mutex);
436error:
437	ipcomp_free_data(ipcd);
438	mutex_unlock(&ipcomp_resource_mutex);
439	kfree(ipcd);
440	goto out;
441}
442
443static struct xfrm_type ipcomp_type = {
444	.description	= "IPCOMP4",
445	.owner		= THIS_MODULE,
446	.proto	     	= IPPROTO_COMP,
447	.init_state	= ipcomp_init_state,
448	.destructor	= ipcomp_destroy,
449	.input		= ipcomp_input,
450	.output		= ipcomp_output
451};
452
453static struct net_protocol ipcomp4_protocol = {
454	.handler	=	xfrm4_rcv,
455	.err_handler	=	ipcomp4_err,
456	.no_policy	=	1,
457};
458
459static int __init ipcomp4_init(void)
460{
461	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
462		printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
463		return -EAGAIN;
464	}
465	if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
466		printk(KERN_INFO "ipcomp init: can't add protocol\n");
467		xfrm_unregister_type(&ipcomp_type, AF_INET);
468		return -EAGAIN;
469	}
470	return 0;
471}
472
473static void __exit ipcomp4_fini(void)
474{
475	if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
476		printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
477	if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
478		printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
479}
480
481module_init(ipcomp4_init);
482module_exit(ipcomp4_fini);
483
484MODULE_LICENSE("GPL");
485MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
486MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
487
488