1/*
  2 * IP Payload Compression Protocol (IPComp) - RFC3173.
  3 *
  4 * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
  5 * Copyright (c) 2003-2008 Herbert Xu <herbert@gondor.apana.org.au>
  6 *
  7 * This program is free software; you can redistribute it and/or modify it
  8 * under the terms of the GNU General Public License as published by the Free
  9 * Software Foundation; either version 2 of the License, or (at your option)
 10 * any later version.
 11 *
 12 * Todo:
 13 *   - Tunable compression parameters.
 14 *   - Compression stats.
 15 *   - Adaptive compression.
 16 */
 17
 18#include <linux/crypto.h>
 19#include <linux/err.h>
 20#include <linux/list.h>
 21#include <linux/module.h>
 22#include <linux/mutex.h>
 23#include <linux/percpu.h>
 24#include <linux/slab.h>
 25#include <linux/smp.h>
 26#include <linux/vmalloc.h>
 27#include <net/ip.h>
 28#include <net/ipcomp.h>
 29#include <net/xfrm.h>
 30
 31struct ipcomp_tfms {
 32	struct list_head list;
 33	struct crypto_comp * __percpu *tfms;
 34	int users;
 35};
 36
 37static DEFINE_MUTEX(ipcomp_resource_mutex);
 38static void * __percpu *ipcomp_scratches;
 39static int ipcomp_scratch_users;
 40static LIST_HEAD(ipcomp_tfms_list);
 41
 42static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
 43{
 44	struct ipcomp_data *ipcd = x->data;
 45	const int plen = skb->len;
 46	int dlen = IPCOMP_SCRATCH_SIZE;
 47	const u8 *start = skb->data;
 48	const int cpu = get_cpu();
 49	u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
 50	struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu);
 51	int err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen);
 52	int len;
 53
 54	if (err)
 55		goto out;
 56
 57	if (dlen < (plen + sizeof(struct ip_comp_hdr))) {
 58		err = -EINVAL;
 59		goto out;
 60	}
 61
 62	len = dlen - plen;
 63	if (len > skb_tailroom(skb))
 64		len = skb_tailroom(skb);
 65
 66	__skb_put(skb, len);
 67
 68	len += plen;
 69	skb_copy_to_linear_data(skb, scratch, len);
 70
 71	while ((scratch += len, dlen -= len) > 0) {
 72		skb_frag_t *frag;
 73		struct page *page;
 74
 75		err = -EMSGSIZE;
 76		if (WARN_ON(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS))
 77			goto out;
 78
 79		frag = skb_shinfo(skb)->frags + skb_shinfo(skb)->nr_frags;
 80		page = alloc_page(GFP_ATOMIC);
 81
 82		err = -ENOMEM;
 83		if (!page)
 84			goto out;
 85
 86		__skb_frag_set_page(frag, page);
 87
 88		len = PAGE_SIZE;
 89		if (dlen < len)
 90			len = dlen;
 91
 92		frag->page_offset = 0;
 93		skb_frag_size_set(frag, len);
 94		memcpy(skb_frag_address(frag), scratch, len);
 95
 96		skb->truesize += len;
 97		skb->data_len += len;
 98		skb->len += len;
 99
100		skb_shinfo(skb)->nr_frags++;
101	}
102
103	err = 0;
104
105out:
106	put_cpu();
107	return err;
108}
109
110int ipcomp_input(struct xfrm_state *x, struct sk_buff *skb)
111{
112	int nexthdr;
113	int err = -ENOMEM;
114	struct ip_comp_hdr *ipch;
115
116	if (skb_linearize_cow(skb))
117		goto out;
118
119	skb->ip_summed = CHECKSUM_NONE;
120
121	/* Remove ipcomp header and decompress original payload */
122	ipch = (void *)skb->data;
123	nexthdr = ipch->nexthdr;
124
125	skb->transport_header = skb->network_header + sizeof(*ipch);
126	__skb_pull(skb, sizeof(*ipch));
127	err = ipcomp_decompress(x, skb);
128	if (err)
129		goto out;
130
131	err = nexthdr;
132
133out:
134	return err;
135}
136EXPORT_SYMBOL_GPL(ipcomp_input);
137
138static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
139{
140	struct ipcomp_data *ipcd = x->data;
141	const int plen = skb->len;
142	int dlen = IPCOMP_SCRATCH_SIZE;
143	u8 *start = skb->data;
144	const int cpu = get_cpu();
145	u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
146	struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu);
147	int err;
148
149	local_bh_disable();
150	err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);
151	local_bh_enable();
152	if (err)
153		goto out;
154
155	if ((dlen + sizeof(struct ip_comp_hdr)) >= plen) {
156		err = -EMSGSIZE;
157		goto out;
158	}
159
160	memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
161	put_cpu();
162
163	pskb_trim(skb, dlen + sizeof(struct ip_comp_hdr));
164	return 0;
165
166out:
167	put_cpu();
168	return err;
169}
170
171int ipcomp_output(struct xfrm_state *x, struct sk_buff *skb)
172{
173	int err;
174	struct ip_comp_hdr *ipch;
175	struct ipcomp_data *ipcd = x->data;
176
177	if (skb->len < ipcd->threshold) {
178		/* Don't bother compressing */
179		goto out_ok;
180	}
181
182	if (skb_linearize_cow(skb))
183		goto out_ok;
184
185	err = ipcomp_compress(x, skb);
186
187	if (err) {
188		goto out_ok;
189	}
190
191	/* Install ipcomp header, convert into ipcomp datagram. */
192	ipch = ip_comp_hdr(skb);
193	ipch->nexthdr = *skb_mac_header(skb);
194	ipch->flags = 0;
195	ipch->cpi = htons((u16 )ntohl(x->id.spi));
196	*skb_mac_header(skb) = IPPROTO_COMP;
197out_ok:
198	skb_push(skb, -skb_network_offset(skb));
199	return 0;
200}
201EXPORT_SYMBOL_GPL(ipcomp_output);
202
203static void ipcomp_free_scratches(void)
204{
205	int i;
206	void * __percpu *scratches;
207
208	if (--ipcomp_scratch_users)
209		return;
210
211	scratches = ipcomp_scratches;
212	if (!scratches)
213		return;
214
215	for_each_possible_cpu(i)
216		vfree(*per_cpu_ptr(scratches, i));
217
218	free_percpu(scratches);
219}
220
221static void * __percpu *ipcomp_alloc_scratches(void)
222{
223	int i;
224	void * __percpu *scratches;
225
226	if (ipcomp_scratch_users++)
227		return ipcomp_scratches;
228
229	scratches = alloc_percpu(void *);
230	if (!scratches)
231		return NULL;
232
233	ipcomp_scratches = scratches;
234
235	for_each_possible_cpu(i) {
236		void *scratch = vmalloc(IPCOMP_SCRATCH_SIZE);
237		if (!scratch)
238			return NULL;
239		*per_cpu_ptr(scratches, i) = scratch;
240	}
241
242	return scratches;
243}
244
245static void ipcomp_free_tfms(struct crypto_comp * __percpu *tfms)
246{
247	struct ipcomp_tfms *pos;
248	int cpu;
249
250	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
251		if (pos->tfms == tfms)
252			break;
253	}
254
255	WARN_ON(!pos);
256
257	if (--pos->users)
258		return;
259
260	list_del(&pos->list);
261	kfree(pos);
262
263	if (!tfms)
264		return;
265
266	for_each_possible_cpu(cpu) {
267		struct crypto_comp *tfm = *per_cpu_ptr(tfms, cpu);
268		crypto_free_comp(tfm);
269	}
270	free_percpu(tfms);
271}
272
273static struct crypto_comp * __percpu *ipcomp_alloc_tfms(const char *alg_name)
274{
275	struct ipcomp_tfms *pos;
276	struct crypto_comp * __percpu *tfms;
277	int cpu;
278
279	/* This can be any valid CPU ID so we don't need locking. */
280	cpu = raw_smp_processor_id();
281
282	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
283		struct crypto_comp *tfm;
284
285		tfms = pos->tfms;
286		tfm = *per_cpu_ptr(tfms, cpu);
287
288		if (!strcmp(crypto_comp_name(tfm), alg_name)) {
289			pos->users++;
290			return tfms;
291		}
292	}
293
294	pos = kmalloc(sizeof(*pos), GFP_KERNEL);
295	if (!pos)
296		return NULL;
297
298	pos->users = 1;
299	INIT_LIST_HEAD(&pos->list);
300	list_add(&pos->list, &ipcomp_tfms_list);
301
302	pos->tfms = tfms = alloc_percpu(struct crypto_comp *);
303	if (!tfms)
304		goto error;
305
306	for_each_possible_cpu(cpu) {
307		struct crypto_comp *tfm = crypto_alloc_comp(alg_name, 0,
308							    CRYPTO_ALG_ASYNC);
309		if (IS_ERR(tfm))
310			goto error;
311		*per_cpu_ptr(tfms, cpu) = tfm;
312	}
313
314	return tfms;
315
316error:
317	ipcomp_free_tfms(tfms);
318	return NULL;
319}
320
321static void ipcomp_free_data(struct ipcomp_data *ipcd)
322{
323	if (ipcd->tfms)
324		ipcomp_free_tfms(ipcd->tfms);
325	ipcomp_free_scratches();
326}
327
328void ipcomp_destroy(struct xfrm_state *x)
329{
330	struct ipcomp_data *ipcd = x->data;
331	if (!ipcd)
332		return;
333	xfrm_state_delete_tunnel(x);
334	mutex_lock(&ipcomp_resource_mutex);
335	ipcomp_free_data(ipcd);
336	mutex_unlock(&ipcomp_resource_mutex);
337	kfree(ipcd);
338}
339EXPORT_SYMBOL_GPL(ipcomp_destroy);
340
341int ipcomp_init_state(struct xfrm_state *x)
342{
343	int err;
344	struct ipcomp_data *ipcd;
345	struct xfrm_algo_desc *calg_desc;
346
347	err = -EINVAL;
348	if (!x->calg)
349		goto out;
350
351	if (x->encap)
352		goto out;
353
354	err = -ENOMEM;
355	ipcd = kzalloc(sizeof(*ipcd), GFP_KERNEL);
356	if (!ipcd)
357		goto out;
358
359	mutex_lock(&ipcomp_resource_mutex);
360	if (!ipcomp_alloc_scratches())
361		goto error;
362
363	ipcd->tfms = ipcomp_alloc_tfms(x->calg->alg_name);
364	if (!ipcd->tfms)
365		goto error;
366	mutex_unlock(&ipcomp_resource_mutex);
367
368	calg_desc = xfrm_calg_get_byname(x->calg->alg_name, 0);
369	BUG_ON(!calg_desc);
370	ipcd->threshold = calg_desc->uinfo.comp.threshold;
371	x->data = ipcd;
372	err = 0;
373out:
374	return err;
375
376error:
377	ipcomp_free_data(ipcd);
378	mutex_unlock(&ipcomp_resource_mutex);
379	kfree(ipcd);
380	goto out;
381}
382EXPORT_SYMBOL_GPL(ipcomp_init_state);
383
384MODULE_LICENSE("GPL");
385MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
386MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");