xref: /openbmc/linux/net/ipv4/esp4.c (revision 0da85d1e) 
1 #define pr_fmt(fmt) "IPsec: " fmt
2 
3 #include <crypto/aead.h>
4 #include <crypto/authenc.h>
5 #include <linux/err.h>
6 #include <linux/module.h>
7 #include <net/ip.h>
8 #include <net/xfrm.h>
9 #include <net/esp.h>
10 #include <linux/scatterlist.h>
11 #include <linux/kernel.h>
12 #include <linux/pfkeyv2.h>
13 #include <linux/rtnetlink.h>
14 #include <linux/slab.h>
15 #include <linux/spinlock.h>
16 #include <linux/in6.h>
17 #include <net/icmp.h>
18 #include <net/protocol.h>
19 #include <net/udp.h>
20 
21 struct esp_skb_cb {
22 	struct xfrm_skb_cb xfrm;
23 	void *tmp;
24 };
25 
26 #define ESP_SKB_CB(__skb) ((struct esp_skb_cb *)&((__skb)->cb[0]))
27 
28 static u32 esp4_get_mtu(struct xfrm_state *x, int mtu);
29 
30 /*
31  * Allocate an AEAD request structure with extra space for SG and IV.
32  *
33  * For alignment considerations the IV is placed at the front, followed
34  * by the request and finally the SG list.
35  *
36  * TODO: Use spare space in skb for this where possible.
37  */
38 static void *esp_alloc_tmp(struct crypto_aead *aead, int nfrags, int seqhilen)
39 {
40 	unsigned int len;
41 
42 	len = seqhilen;
43 
44 	len += crypto_aead_ivsize(aead);
45 
46 	if (len) {
47 		len += crypto_aead_alignmask(aead) &
48 		       ~(crypto_tfm_ctx_alignment() - 1);
49 		len = ALIGN(len, crypto_tfm_ctx_alignment());
50 	}
51 
52 	len += sizeof(struct aead_givcrypt_request) + crypto_aead_reqsize(aead);
53 	len = ALIGN(len, __alignof__(struct scatterlist));
54 
55 	len += sizeof(struct scatterlist) * nfrags;
56 
57 	return kmalloc(len, GFP_ATOMIC);
58 }
59 
60 static inline __be32 *esp_tmp_seqhi(void *tmp)
61 {
62 	return PTR_ALIGN((__be32 *)tmp, __alignof__(__be32));
63 }
64 static inline u8 *esp_tmp_iv(struct crypto_aead *aead, void *tmp, int seqhilen)
65 {
66 	return crypto_aead_ivsize(aead) ?
67 	       PTR_ALIGN((u8 *)tmp + seqhilen,
68 			 crypto_aead_alignmask(aead) + 1) : tmp + seqhilen;
69 }
70 
71 static inline struct aead_givcrypt_request *esp_tmp_givreq(
72 	struct crypto_aead *aead, u8 *iv)
73 {
74 	struct aead_givcrypt_request *req;
75 
76 	req = (void *)PTR_ALIGN(iv + crypto_aead_ivsize(aead),
77 				crypto_tfm_ctx_alignment());
78 	aead_givcrypt_set_tfm(req, aead);
79 	return req;
80 }
81 
82 static inline struct aead_request *esp_tmp_req(struct crypto_aead *aead, u8 *iv)
83 {
84 	struct aead_request *req;
85 
86 	req = (void *)PTR_ALIGN(iv + crypto_aead_ivsize(aead),
87 				crypto_tfm_ctx_alignment());
88 	aead_request_set_tfm(req, aead);
89 	return req;
90 }
91 
92 static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead,
93 					     struct aead_request *req)
94 {
95 	return (void *)ALIGN((unsigned long)(req + 1) +
96 			     crypto_aead_reqsize(aead),
97 			     __alignof__(struct scatterlist));
98 }
99 
100 static inline struct scatterlist *esp_givreq_sg(
101 	struct crypto_aead *aead, struct aead_givcrypt_request *req)
102 {
103 	return (void *)ALIGN((unsigned long)(req + 1) +
104 			     crypto_aead_reqsize(aead),
105 			     __alignof__(struct scatterlist));
106 }
107 
108 static void esp_output_done(struct crypto_async_request *base, int err)
109 {
110 	struct sk_buff *skb = base->data;
111 
112 	kfree(ESP_SKB_CB(skb)->tmp);
113 	xfrm_output_resume(skb, err);
114 }
115 
116 static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
117 {
118 	int err;
119 	struct ip_esp_hdr *esph;
120 	struct crypto_aead *aead;
121 	struct aead_givcrypt_request *req;
122 	struct scatterlist *sg;
123 	struct scatterlist *asg;
124 	struct sk_buff *trailer;
125 	void *tmp;
126 	u8 *iv;
127 	u8 *tail;
128 	int blksize;
129 	int clen;
130 	int alen;
131 	int plen;
132 	int tfclen;
133 	int nfrags;
134 	int assoclen;
135 	int sglists;
136 	int seqhilen;
137 	__be32 *seqhi;
138 
139 	/* skb is pure payload to encrypt */
140 
141 	aead = x->data;
142 	alen = crypto_aead_authsize(aead);
143 
144 	tfclen = 0;
145 	if (x->tfcpad) {
146 		struct xfrm_dst *dst = (struct xfrm_dst *)skb_dst(skb);
147 		u32 padto;
148 
149 		padto = min(x->tfcpad, esp4_get_mtu(x, dst->child_mtu_cached));
150 		if (skb->len < padto)
151 			tfclen = padto - skb->len;
152 	}
153 	blksize = ALIGN(crypto_aead_blocksize(aead), 4);
154 	clen = ALIGN(skb->len + 2 + tfclen, blksize);
155 	plen = clen - skb->len - tfclen;
156 
157 	err = skb_cow_data(skb, tfclen + plen + alen, &trailer);
158 	if (err < 0)
159 		goto error;
160 	nfrags = err;
161 
162 	assoclen = sizeof(*esph);
163 	sglists = 1;
164 	seqhilen = 0;
165 
166 	if (x->props.flags & XFRM_STATE_ESN) {
167 		sglists += 2;
168 		seqhilen += sizeof(__be32);
169 		assoclen += seqhilen;
170 	}
171 
172 	tmp = esp_alloc_tmp(aead, nfrags + sglists, seqhilen);
173 	if (!tmp) {
174 		err = -ENOMEM;
175 		goto error;
176 	}
177 
178 	seqhi = esp_tmp_seqhi(tmp);
179 	iv = esp_tmp_iv(aead, tmp, seqhilen);
180 	req = esp_tmp_givreq(aead, iv);
181 	asg = esp_givreq_sg(aead, req);
182 	sg = asg + sglists;
183 
184 	/* Fill padding... */
185 	tail = skb_tail_pointer(trailer);
186 	if (tfclen) {
187 		memset(tail, 0, tfclen);
188 		tail += tfclen;
189 	}
190 	do {
191 		int i;
192 		for (i = 0; i < plen - 2; i++)
193 			tail[i] = i + 1;
194 	} while (0);
195 	tail[plen - 2] = plen - 2;
196 	tail[plen - 1] = *skb_mac_header(skb);
197 	pskb_put(skb, trailer, clen - skb->len + alen);
198 
199 	skb_push(skb, -skb_network_offset(skb));
200 	esph = ip_esp_hdr(skb);
201 	*skb_mac_header(skb) = IPPROTO_ESP;
202 
203 	/* this is non-NULL only with UDP Encapsulation */
204 	if (x->encap) {
205 		struct xfrm_encap_tmpl *encap = x->encap;
206 		struct udphdr *uh;
207 		__be32 *udpdata32;
208 		__be16 sport, dport;
209 		int encap_type;
210 
211 		spin_lock_bh(&x->lock);
212 		sport = encap->encap_sport;
213 		dport = encap->encap_dport;
214 		encap_type = encap->encap_type;
215 		spin_unlock_bh(&x->lock);
216 
217 		uh = (struct udphdr *)esph;
218 		uh->source = sport;
219 		uh->dest = dport;
220 		uh->len = htons(skb->len - skb_transport_offset(skb));
221 		uh->check = 0;
222 
223 		switch (encap_type) {
224 		default:
225 		case UDP_ENCAP_ESPINUDP:
226 			esph = (struct ip_esp_hdr *)(uh + 1);
227 			break;
228 		case UDP_ENCAP_ESPINUDP_NON_IKE:
229 			udpdata32 = (__be32 *)(uh + 1);
230 			udpdata32[0] = udpdata32[1] = 0;
231 			esph = (struct ip_esp_hdr *)(udpdata32 + 2);
232 			break;
233 		}
234 
235 		*skb_mac_header(skb) = IPPROTO_UDP;
236 	}
237 
238 	esph->spi = x->id.spi;
239 	esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
240 
241 	sg_init_table(sg, nfrags);
242 	skb_to_sgvec(skb, sg,
243 		     esph->enc_data + crypto_aead_ivsize(aead) - skb->data,
244 		     clen + alen);
245 
246 	if ((x->props.flags & XFRM_STATE_ESN)) {
247 		sg_init_table(asg, 3);
248 		sg_set_buf(asg, &esph->spi, sizeof(__be32));
249 		*seqhi = htonl(XFRM_SKB_CB(skb)->seq.output.hi);
250 		sg_set_buf(asg + 1, seqhi, seqhilen);
251 		sg_set_buf(asg + 2, &esph->seq_no, sizeof(__be32));
252 	} else
253 		sg_init_one(asg, esph, sizeof(*esph));
254 
255 	aead_givcrypt_set_callback(req, 0, esp_output_done, skb);
256 	aead_givcrypt_set_crypt(req, sg, sg, clen, iv);
257 	aead_givcrypt_set_assoc(req, asg, assoclen);
258 	aead_givcrypt_set_giv(req, esph->enc_data,
259 			      XFRM_SKB_CB(skb)->seq.output.low);
260 
261 	ESP_SKB_CB(skb)->tmp = tmp;
262 	err = crypto_aead_givencrypt(req);
263 	if (err == -EINPROGRESS)
264 		goto error;
265 
266 	if (err == -EBUSY)
267 		err = NET_XMIT_DROP;
268 
269 	kfree(tmp);
270 
271 error:
272 	return err;
273 }
274 
275 static int esp_input_done2(struct sk_buff *skb, int err)
276 {
277 	const struct iphdr *iph;
278 	struct xfrm_state *x = xfrm_input_state(skb);
279 	struct crypto_aead *aead = x->data;
280 	int alen = crypto_aead_authsize(aead);
281 	int hlen = sizeof(struct ip_esp_hdr) + crypto_aead_ivsize(aead);
282 	int elen = skb->len - hlen;
283 	int ihl;
284 	u8 nexthdr[2];
285 	int padlen;
286 
287 	kfree(ESP_SKB_CB(skb)->tmp);
288 
289 	if (unlikely(err))
290 		goto out;
291 
292 	if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
293 		BUG();
294 
295 	err = -EINVAL;
296 	padlen = nexthdr[0];
297 	if (padlen + 2 + alen >= elen)
298 		goto out;
299 
300 	/* ... check padding bits here. Silly. :-) */
301 
302 	iph = ip_hdr(skb);
303 	ihl = iph->ihl * 4;
304 
305 	if (x->encap) {
306 		struct xfrm_encap_tmpl *encap = x->encap;
307 		struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);
308 
309 		/*
310 		 * 1) if the NAT-T peer's IP or port changed then
311 		 *    advertize the change to the keying daemon.
312 		 *    This is an inbound SA, so just compare
313 		 *    SRC ports.
314 		 */
315 		if (iph->saddr != x->props.saddr.a4 ||
316 		    uh->source != encap->encap_sport) {
317 			xfrm_address_t ipaddr;
318 
319 			ipaddr.a4 = iph->saddr;
320 			km_new_mapping(x, &ipaddr, uh->source);
321 
322 			/* XXX: perhaps add an extra
323 			 * policy check here, to see
324 			 * if we should allow or
325 			 * reject a packet from a
326 			 * different source
327 			 * address/port.
328 			 */
329 		}
330 
331 		/*
332 		 * 2) ignore UDP/TCP checksums in case
333 		 *    of NAT-T in Transport Mode, or
334 		 *    perform other post-processing fixes
335 		 *    as per draft-ietf-ipsec-udp-encaps-06,
336 		 *    section 3.1.2
337 		 */
338 		if (x->props.mode == XFRM_MODE_TRANSPORT)
339 			skb->ip_summed = CHECKSUM_UNNECESSARY;
340 	}
341 
342 	pskb_trim(skb, skb->len - alen - padlen - 2);
343 	__skb_pull(skb, hlen);
344 	if (x->props.mode == XFRM_MODE_TUNNEL)
345 		skb_reset_transport_header(skb);
346 	else
347 		skb_set_transport_header(skb, -ihl);
348 
349 	err = nexthdr[1];
350 
351 	/* RFC4303: Drop dummy packets without any error */
352 	if (err == IPPROTO_NONE)
353 		err = -EINVAL;
354 
355 out:
356 	return err;
357 }
358 
359 static void esp_input_done(struct crypto_async_request *base, int err)
360 {
361 	struct sk_buff *skb = base->data;
362 
363 	xfrm_input_resume(skb, esp_input_done2(skb, err));
364 }
365 
366 /*
367  * Note: detecting truncated vs. non-truncated authentication data is very
368  * expensive, so we only support truncated data, which is the recommended
369  * and common case.
370  */
371 static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
372 {
373 	struct ip_esp_hdr *esph;
374 	struct crypto_aead *aead = x->data;
375 	struct aead_request *req;
376 	struct sk_buff *trailer;
377 	int elen = skb->len - sizeof(*esph) - crypto_aead_ivsize(aead);
378 	int nfrags;
379 	int assoclen;
380 	int sglists;
381 	int seqhilen;
382 	__be32 *seqhi;
383 	void *tmp;
384 	u8 *iv;
385 	struct scatterlist *sg;
386 	struct scatterlist *asg;
387 	int err = -EINVAL;
388 
389 	if (!pskb_may_pull(skb, sizeof(*esph) + crypto_aead_ivsize(aead)))
390 		goto out;
391 
392 	if (elen <= 0)
393 		goto out;
394 
395 	err = skb_cow_data(skb, 0, &trailer);
396 	if (err < 0)
397 		goto out;
398 
399 	nfrags = err;
400 
401 	assoclen = sizeof(*esph);
402 	sglists = 1;
403 	seqhilen = 0;
404 
405 	if (x->props.flags & XFRM_STATE_ESN) {
406 		sglists += 2;
407 		seqhilen += sizeof(__be32);
408 		assoclen += seqhilen;
409 	}
410 
411 	err = -ENOMEM;
412 	tmp = esp_alloc_tmp(aead, nfrags + sglists, seqhilen);
413 	if (!tmp)
414 		goto out;
415 
416 	ESP_SKB_CB(skb)->tmp = tmp;
417 	seqhi = esp_tmp_seqhi(tmp);
418 	iv = esp_tmp_iv(aead, tmp, seqhilen);
419 	req = esp_tmp_req(aead, iv);
420 	asg = esp_req_sg(aead, req);
421 	sg = asg + sglists;
422 
423 	skb->ip_summed = CHECKSUM_NONE;
424 
425 	esph = (struct ip_esp_hdr *)skb->data;
426 
427 	/* Get ivec. This can be wrong, check against another impls. */
428 	iv = esph->enc_data;
429 
430 	sg_init_table(sg, nfrags);
431 	skb_to_sgvec(skb, sg, sizeof(*esph) + crypto_aead_ivsize(aead), elen);
432 
433 	if ((x->props.flags & XFRM_STATE_ESN)) {
434 		sg_init_table(asg, 3);
435 		sg_set_buf(asg, &esph->spi, sizeof(__be32));
436 		*seqhi = XFRM_SKB_CB(skb)->seq.input.hi;
437 		sg_set_buf(asg + 1, seqhi, seqhilen);
438 		sg_set_buf(asg + 2, &esph->seq_no, sizeof(__be32));
439 	} else
440 		sg_init_one(asg, esph, sizeof(*esph));
441 
442 	aead_request_set_callback(req, 0, esp_input_done, skb);
443 	aead_request_set_crypt(req, sg, sg, elen, iv);
444 	aead_request_set_assoc(req, asg, assoclen);
445 
446 	err = crypto_aead_decrypt(req);
447 	if (err == -EINPROGRESS)
448 		goto out;
449 
450 	err = esp_input_done2(skb, err);
451 
452 out:
453 	return err;
454 }
455 
456 static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
457 {
458 	struct crypto_aead *aead = x->data;
459 	u32 blksize = ALIGN(crypto_aead_blocksize(aead), 4);
460 	unsigned int net_adj;
461 
462 	switch (x->props.mode) {
463 	case XFRM_MODE_TRANSPORT:
464 	case XFRM_MODE_BEET:
465 		net_adj = sizeof(struct iphdr);
466 		break;
467 	case XFRM_MODE_TUNNEL:
468 		net_adj = 0;
469 		break;
470 	default:
471 		BUG();
472 	}
473 
474 	return ((mtu - x->props.header_len - crypto_aead_authsize(aead) -
475 		 net_adj) & ~(blksize - 1)) + net_adj - 2;
476 }
477 
478 static int esp4_err(struct sk_buff *skb, u32 info)
479 {
480 	struct net *net = dev_net(skb->dev);
481 	const struct iphdr *iph = (const struct iphdr *)skb->data;
482 	struct ip_esp_hdr *esph = (struct ip_esp_hdr *)(skb->data+(iph->ihl<<2));
483 	struct xfrm_state *x;
484 
485 	switch (icmp_hdr(skb)->type) {
486 	case ICMP_DEST_UNREACH:
487 		if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
488 			return 0;
489 	case ICMP_REDIRECT:
490 		break;
491 	default:
492 		return 0;
493 	}
494 
495 	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
496 			      esph->spi, IPPROTO_ESP, AF_INET);
497 	if (!x)
498 		return 0;
499 
500 	if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
501 		ipv4_update_pmtu(skb, net, info, 0, 0, IPPROTO_ESP, 0);
502 	else
503 		ipv4_redirect(skb, net, 0, 0, IPPROTO_ESP, 0);
504 	xfrm_state_put(x);
505 
506 	return 0;
507 }
508 
509 static void esp_destroy(struct xfrm_state *x)
510 {
511 	struct crypto_aead *aead = x->data;
512 
513 	if (!aead)
514 		return;
515 
516 	crypto_free_aead(aead);
517 }
518 
519 static int esp_init_aead(struct xfrm_state *x)
520 {
521 	struct crypto_aead *aead;
522 	int err;
523 
524 	aead = crypto_alloc_aead(x->aead->alg_name, 0, 0);
525 	err = PTR_ERR(aead);
526 	if (IS_ERR(aead))
527 		goto error;
528 
529 	x->data = aead;
530 
531 	err = crypto_aead_setkey(aead, x->aead->alg_key,
532 				 (x->aead->alg_key_len + 7) / 8);
533 	if (err)
534 		goto error;
535 
536 	err = crypto_aead_setauthsize(aead, x->aead->alg_icv_len / 8);
537 	if (err)
538 		goto error;
539 
540 error:
541 	return err;
542 }
543 
544 static int esp_init_authenc(struct xfrm_state *x)
545 {
546 	struct crypto_aead *aead;
547 	struct crypto_authenc_key_param *param;
548 	struct rtattr *rta;
549 	char *key;
550 	char *p;
551 	char authenc_name[CRYPTO_MAX_ALG_NAME];
552 	unsigned int keylen;
553 	int err;
554 
555 	err = -EINVAL;
556 	if (!x->ealg)
557 		goto error;
558 
559 	err = -ENAMETOOLONG;
560 
561 	if ((x->props.flags & XFRM_STATE_ESN)) {
562 		if (snprintf(authenc_name, CRYPTO_MAX_ALG_NAME,
563 			     "authencesn(%s,%s)",
564 			     x->aalg ? x->aalg->alg_name : "digest_null",
565 			     x->ealg->alg_name) >= CRYPTO_MAX_ALG_NAME)
566 			goto error;
567 	} else {
568 		if (snprintf(authenc_name, CRYPTO_MAX_ALG_NAME,
569 			     "authenc(%s,%s)",
570 			     x->aalg ? x->aalg->alg_name : "digest_null",
571 			     x->ealg->alg_name) >= CRYPTO_MAX_ALG_NAME)
572 			goto error;
573 	}
574 
575 	aead = crypto_alloc_aead(authenc_name, 0, 0);
576 	err = PTR_ERR(aead);
577 	if (IS_ERR(aead))
578 		goto error;
579 
580 	x->data = aead;
581 
582 	keylen = (x->aalg ? (x->aalg->alg_key_len + 7) / 8 : 0) +
583 		 (x->ealg->alg_key_len + 7) / 8 + RTA_SPACE(sizeof(*param));
584 	err = -ENOMEM;
585 	key = kmalloc(keylen, GFP_KERNEL);
586 	if (!key)
587 		goto error;
588 
589 	p = key;
590 	rta = (void *)p;
591 	rta->rta_type = CRYPTO_AUTHENC_KEYA_PARAM;
592 	rta->rta_len = RTA_LENGTH(sizeof(*param));
593 	param = RTA_DATA(rta);
594 	p += RTA_SPACE(sizeof(*param));
595 
596 	if (x->aalg) {
597 		struct xfrm_algo_desc *aalg_desc;
598 
599 		memcpy(p, x->aalg->alg_key, (x->aalg->alg_key_len + 7) / 8);
600 		p += (x->aalg->alg_key_len + 7) / 8;
601 
602 		aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
603 		BUG_ON(!aalg_desc);
604 
605 		err = -EINVAL;
606 		if (aalg_desc->uinfo.auth.icv_fullbits / 8 !=
607 		    crypto_aead_authsize(aead)) {
608 			pr_info("ESP: %s digestsize %u != %hu\n",
609 				x->aalg->alg_name,
610 				crypto_aead_authsize(aead),
611 				aalg_desc->uinfo.auth.icv_fullbits / 8);
612 			goto free_key;
613 		}
614 
615 		err = crypto_aead_setauthsize(
616 			aead, x->aalg->alg_trunc_len / 8);
617 		if (err)
618 			goto free_key;
619 	}
620 
621 	param->enckeylen = cpu_to_be32((x->ealg->alg_key_len + 7) / 8);
622 	memcpy(p, x->ealg->alg_key, (x->ealg->alg_key_len + 7) / 8);
623 
624 	err = crypto_aead_setkey(aead, key, keylen);
625 
626 free_key:
627 	kfree(key);
628 
629 error:
630 	return err;
631 }
632 
633 static int esp_init_state(struct xfrm_state *x)
634 {
635 	struct crypto_aead *aead;
636 	u32 align;
637 	int err;
638 
639 	x->data = NULL;
640 
641 	if (x->aead)
642 		err = esp_init_aead(x);
643 	else
644 		err = esp_init_authenc(x);
645 
646 	if (err)
647 		goto error;
648 
649 	aead = x->data;
650 
651 	x->props.header_len = sizeof(struct ip_esp_hdr) +
652 			      crypto_aead_ivsize(aead);
653 	if (x->props.mode == XFRM_MODE_TUNNEL)
654 		x->props.header_len += sizeof(struct iphdr);
655 	else if (x->props.mode == XFRM_MODE_BEET && x->sel.family != AF_INET6)
656 		x->props.header_len += IPV4_BEET_PHMAXLEN;
657 	if (x->encap) {
658 		struct xfrm_encap_tmpl *encap = x->encap;
659 
660 		switch (encap->encap_type) {
661 		default:
662 			goto error;
663 		case UDP_ENCAP_ESPINUDP:
664 			x->props.header_len += sizeof(struct udphdr);
665 			break;
666 		case UDP_ENCAP_ESPINUDP_NON_IKE:
667 			x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
668 			break;
669 		}
670 	}
671 
672 	align = ALIGN(crypto_aead_blocksize(aead), 4);
673 	x->props.trailer_len = align + 1 + crypto_aead_authsize(aead);
674 
675 error:
676 	return err;
677 }
678 
679 static int esp4_rcv_cb(struct sk_buff *skb, int err)
680 {
681 	return 0;
682 }
683 
684 static const struct xfrm_type esp_type =
685 {
686 	.description	= "ESP4",
687 	.owner		= THIS_MODULE,
688 	.proto	     	= IPPROTO_ESP,
689 	.flags		= XFRM_TYPE_REPLAY_PROT,
690 	.init_state	= esp_init_state,
691 	.destructor	= esp_destroy,
692 	.get_mtu	= esp4_get_mtu,
693 	.input		= esp_input,
694 	.output		= esp_output
695 };
696 
697 static struct xfrm4_protocol esp4_protocol = {
698 	.handler	=	xfrm4_rcv,
699 	.input_handler	=	xfrm_input,
700 	.cb_handler	=	esp4_rcv_cb,
701 	.err_handler	=	esp4_err,
702 	.priority	=	0,
703 };
704 
705 static int __init esp4_init(void)
706 {
707 	if (xfrm_register_type(&esp_type, AF_INET) < 0) {
708 		pr_info("%s: can't add xfrm type\n", __func__);
709 		return -EAGAIN;
710 	}
711 	if (xfrm4_protocol_register(&esp4_protocol, IPPROTO_ESP) < 0) {
712 		pr_info("%s: can't add protocol\n", __func__);
713 		xfrm_unregister_type(&esp_type, AF_INET);
714 		return -EAGAIN;
715 	}
716 	return 0;
717 }
718 
719 static void __exit esp4_fini(void)
720 {
721 	if (xfrm4_protocol_deregister(&esp4_protocol, IPPROTO_ESP) < 0)
722 		pr_info("%s: can't remove protocol\n", __func__);
723 	if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
724 		pr_info("%s: can't remove xfrm type\n", __func__);
725 }
726 
727 module_init(esp4_init);
728 module_exit(esp4_fini);
729 MODULE_LICENSE("GPL");
730 MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_ESP);
731