xref: /linux/net/xfrm/xfrm_output.c (revision f86fd32d) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * xfrm_output.c - Common IPsec encapsulation code.
4  *
5  * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
6  */
7 
8 #include <linux/errno.h>
9 #include <linux/module.h>
10 #include <linux/netdevice.h>
11 #include <linux/netfilter.h>
12 #include <linux/skbuff.h>
13 #include <linux/slab.h>
14 #include <linux/spinlock.h>
15 #include <net/dst.h>
16 #include <net/inet_ecn.h>
17 #include <net/xfrm.h>
18 
19 #include "xfrm_inout.h"
20 
21 static int xfrm_output2(struct net *net, struct sock *sk, struct sk_buff *skb);
22 static int xfrm_inner_extract_output(struct xfrm_state *x, struct sk_buff *skb);
23 
24 static int xfrm_skb_check_space(struct sk_buff *skb)
25 {
26 	struct dst_entry *dst = skb_dst(skb);
27 	int nhead = dst->header_len + LL_RESERVED_SPACE(dst->dev)
28 		- skb_headroom(skb);
29 	int ntail = dst->dev->needed_tailroom - skb_tailroom(skb);
30 
31 	if (nhead <= 0) {
32 		if (ntail <= 0)
33 			return 0;
34 		nhead = 0;
35 	} else if (ntail < 0)
36 		ntail = 0;
37 
38 	return pskb_expand_head(skb, nhead, ntail, GFP_ATOMIC);
39 }
40 
41 /* Children define the path of the packet through the
42  * Linux networking.  Thus, destinations are stackable.
43  */
44 
45 static struct dst_entry *skb_dst_pop(struct sk_buff *skb)
46 {
47 	struct dst_entry *child = dst_clone(xfrm_dst_child(skb_dst(skb)));
48 
49 	skb_dst_drop(skb);
50 	return child;
51 }
52 
53 /* Add encapsulation header.
54  *
55  * The IP header will be moved forward to make space for the encapsulation
56  * header.
57  */
58 static int xfrm4_transport_output(struct xfrm_state *x, struct sk_buff *skb)
59 {
60 	struct iphdr *iph = ip_hdr(skb);
61 	int ihl = iph->ihl * 4;
62 
63 	skb_set_inner_transport_header(skb, skb_transport_offset(skb));
64 
65 	skb_set_network_header(skb, -x->props.header_len);
66 	skb->mac_header = skb->network_header +
67 			  offsetof(struct iphdr, protocol);
68 	skb->transport_header = skb->network_header + ihl;
69 	__skb_pull(skb, ihl);
70 	memmove(skb_network_header(skb), iph, ihl);
71 	return 0;
72 }
73 
74 /* Add encapsulation header.
75  *
76  * The IP header and mutable extension headers will be moved forward to make
77  * space for the encapsulation header.
78  */
79 static int xfrm6_transport_output(struct xfrm_state *x, struct sk_buff *skb)
80 {
81 #if IS_ENABLED(CONFIG_IPV6)
82 	struct ipv6hdr *iph;
83 	u8 *prevhdr;
84 	int hdr_len;
85 
86 	iph = ipv6_hdr(skb);
87 	skb_set_inner_transport_header(skb, skb_transport_offset(skb));
88 
89 	hdr_len = x->type->hdr_offset(x, skb, &prevhdr);
90 	if (hdr_len < 0)
91 		return hdr_len;
92 	skb_set_mac_header(skb,
93 			   (prevhdr - x->props.header_len) - skb->data);
94 	skb_set_network_header(skb, -x->props.header_len);
95 	skb->transport_header = skb->network_header + hdr_len;
96 	__skb_pull(skb, hdr_len);
97 	memmove(ipv6_hdr(skb), iph, hdr_len);
98 	return 0;
99 #else
100 	WARN_ON_ONCE(1);
101 	return -EAFNOSUPPORT;
102 #endif
103 }
104 
105 /* Add route optimization header space.
106  *
107  * The IP header and mutable extension headers will be moved forward to make
108  * space for the route optimization header.
109  */
110 static int xfrm6_ro_output(struct xfrm_state *x, struct sk_buff *skb)
111 {
112 #if IS_ENABLED(CONFIG_IPV6)
113 	struct ipv6hdr *iph;
114 	u8 *prevhdr;
115 	int hdr_len;
116 
117 	iph = ipv6_hdr(skb);
118 
119 	hdr_len = x->type->hdr_offset(x, skb, &prevhdr);
120 	if (hdr_len < 0)
121 		return hdr_len;
122 	skb_set_mac_header(skb,
123 			   (prevhdr - x->props.header_len) - skb->data);
124 	skb_set_network_header(skb, -x->props.header_len);
125 	skb->transport_header = skb->network_header + hdr_len;
126 	__skb_pull(skb, hdr_len);
127 	memmove(ipv6_hdr(skb), iph, hdr_len);
128 
129 	x->lastused = ktime_get_real_seconds();
130 
131 	return 0;
132 #else
133 	WARN_ON_ONCE(1);
134 	return -EAFNOSUPPORT;
135 #endif
136 }
137 
138 /* Add encapsulation header.
139  *
140  * The top IP header will be constructed per draft-nikander-esp-beet-mode-06.txt.
141  */
142 static int xfrm4_beet_encap_add(struct xfrm_state *x, struct sk_buff *skb)
143 {
144 	struct ip_beet_phdr *ph;
145 	struct iphdr *top_iph;
146 	int hdrlen, optlen;
147 
148 	hdrlen = 0;
149 	optlen = XFRM_MODE_SKB_CB(skb)->optlen;
150 	if (unlikely(optlen))
151 		hdrlen += IPV4_BEET_PHMAXLEN - (optlen & 4);
152 
153 	skb_set_network_header(skb, -x->props.header_len - hdrlen +
154 			       (XFRM_MODE_SKB_CB(skb)->ihl - sizeof(*top_iph)));
155 	if (x->sel.family != AF_INET6)
156 		skb->network_header += IPV4_BEET_PHMAXLEN;
157 	skb->mac_header = skb->network_header +
158 			  offsetof(struct iphdr, protocol);
159 	skb->transport_header = skb->network_header + sizeof(*top_iph);
160 
161 	xfrm4_beet_make_header(skb);
162 
163 	ph = __skb_pull(skb, XFRM_MODE_SKB_CB(skb)->ihl - hdrlen);
164 
165 	top_iph = ip_hdr(skb);
166 
167 	if (unlikely(optlen)) {
168 		if (WARN_ON(optlen < 0))
169 			return -EINVAL;
170 
171 		ph->padlen = 4 - (optlen & 4);
172 		ph->hdrlen = optlen / 8;
173 		ph->nexthdr = top_iph->protocol;
174 		if (ph->padlen)
175 			memset(ph + 1, IPOPT_NOP, ph->padlen);
176 
177 		top_iph->protocol = IPPROTO_BEETPH;
178 		top_iph->ihl = sizeof(struct iphdr) / 4;
179 	}
180 
181 	top_iph->saddr = x->props.saddr.a4;
182 	top_iph->daddr = x->id.daddr.a4;
183 
184 	return 0;
185 }
186 
187 /* Add encapsulation header.
188  *
189  * The top IP header will be constructed per RFC 2401.
190  */
191 static int xfrm4_tunnel_encap_add(struct xfrm_state *x, struct sk_buff *skb)
192 {
193 	struct dst_entry *dst = skb_dst(skb);
194 	struct iphdr *top_iph;
195 	int flags;
196 
197 	skb_set_inner_network_header(skb, skb_network_offset(skb));
198 	skb_set_inner_transport_header(skb, skb_transport_offset(skb));
199 
200 	skb_set_network_header(skb, -x->props.header_len);
201 	skb->mac_header = skb->network_header +
202 			  offsetof(struct iphdr, protocol);
203 	skb->transport_header = skb->network_header + sizeof(*top_iph);
204 	top_iph = ip_hdr(skb);
205 
206 	top_iph->ihl = 5;
207 	top_iph->version = 4;
208 
209 	top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);
210 
211 	/* DS disclosing depends on XFRM_SA_XFLAG_DONT_ENCAP_DSCP */
212 	if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)
213 		top_iph->tos = 0;
214 	else
215 		top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
216 	top_iph->tos = INET_ECN_encapsulate(top_iph->tos,
217 					    XFRM_MODE_SKB_CB(skb)->tos);
218 
219 	flags = x->props.flags;
220 	if (flags & XFRM_STATE_NOECN)
221 		IP_ECN_clear(top_iph);
222 
223 	top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
224 		0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
225 
226 	top_iph->ttl = ip4_dst_hoplimit(xfrm_dst_child(dst));
227 
228 	top_iph->saddr = x->props.saddr.a4;
229 	top_iph->daddr = x->id.daddr.a4;
230 	ip_select_ident(dev_net(dst->dev), skb, NULL);
231 
232 	return 0;
233 }
234 
235 #if IS_ENABLED(CONFIG_IPV6)
236 static int xfrm6_tunnel_encap_add(struct xfrm_state *x, struct sk_buff *skb)
237 {
238 	struct dst_entry *dst = skb_dst(skb);
239 	struct ipv6hdr *top_iph;
240 	int dsfield;
241 
242 	skb_set_inner_network_header(skb, skb_network_offset(skb));
243 	skb_set_inner_transport_header(skb, skb_transport_offset(skb));
244 
245 	skb_set_network_header(skb, -x->props.header_len);
246 	skb->mac_header = skb->network_header +
247 			  offsetof(struct ipv6hdr, nexthdr);
248 	skb->transport_header = skb->network_header + sizeof(*top_iph);
249 	top_iph = ipv6_hdr(skb);
250 
251 	top_iph->version = 6;
252 
253 	memcpy(top_iph->flow_lbl, XFRM_MODE_SKB_CB(skb)->flow_lbl,
254 	       sizeof(top_iph->flow_lbl));
255 	top_iph->nexthdr = xfrm_af2proto(skb_dst(skb)->ops->family);
256 
257 	if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)
258 		dsfield = 0;
259 	else
260 		dsfield = XFRM_MODE_SKB_CB(skb)->tos;
261 	dsfield = INET_ECN_encapsulate(dsfield, XFRM_MODE_SKB_CB(skb)->tos);
262 	if (x->props.flags & XFRM_STATE_NOECN)
263 		dsfield &= ~INET_ECN_MASK;
264 	ipv6_change_dsfield(top_iph, 0, dsfield);
265 	top_iph->hop_limit = ip6_dst_hoplimit(xfrm_dst_child(dst));
266 	top_iph->saddr = *(struct in6_addr *)&x->props.saddr;
267 	top_iph->daddr = *(struct in6_addr *)&x->id.daddr;
268 	return 0;
269 }
270 
271 static int xfrm6_beet_encap_add(struct xfrm_state *x, struct sk_buff *skb)
272 {
273 	struct ipv6hdr *top_iph;
274 	struct ip_beet_phdr *ph;
275 	int optlen, hdr_len;
276 
277 	hdr_len = 0;
278 	optlen = XFRM_MODE_SKB_CB(skb)->optlen;
279 	if (unlikely(optlen))
280 		hdr_len += IPV4_BEET_PHMAXLEN - (optlen & 4);
281 
282 	skb_set_network_header(skb, -x->props.header_len - hdr_len);
283 	if (x->sel.family != AF_INET6)
284 		skb->network_header += IPV4_BEET_PHMAXLEN;
285 	skb->mac_header = skb->network_header +
286 			  offsetof(struct ipv6hdr, nexthdr);
287 	skb->transport_header = skb->network_header + sizeof(*top_iph);
288 	ph = __skb_pull(skb, XFRM_MODE_SKB_CB(skb)->ihl - hdr_len);
289 
290 	xfrm6_beet_make_header(skb);
291 
292 	top_iph = ipv6_hdr(skb);
293 	if (unlikely(optlen)) {
294 		if (WARN_ON(optlen < 0))
295 			return -EINVAL;
296 
297 		ph->padlen = 4 - (optlen & 4);
298 		ph->hdrlen = optlen / 8;
299 		ph->nexthdr = top_iph->nexthdr;
300 		if (ph->padlen)
301 			memset(ph + 1, IPOPT_NOP, ph->padlen);
302 
303 		top_iph->nexthdr = IPPROTO_BEETPH;
304 	}
305 
306 	top_iph->saddr = *(struct in6_addr *)&x->props.saddr;
307 	top_iph->daddr = *(struct in6_addr *)&x->id.daddr;
308 	return 0;
309 }
310 #endif
311 
312 /* Add encapsulation header.
313  *
314  * On exit, the transport header will be set to the start of the
315  * encapsulation header to be filled in by x->type->output and the mac
316  * header will be set to the nextheader (protocol for IPv4) field of the
317  * extension header directly preceding the encapsulation header, or in
318  * its absence, that of the top IP header.
319  * The value of the network header will always point to the top IP header
320  * while skb->data will point to the payload.
321  */
322 static int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
323 {
324 	int err;
325 
326 	err = xfrm_inner_extract_output(x, skb);
327 	if (err)
328 		return err;
329 
330 	IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
331 	skb->protocol = htons(ETH_P_IP);
332 
333 	switch (x->outer_mode.encap) {
334 	case XFRM_MODE_BEET:
335 		return xfrm4_beet_encap_add(x, skb);
336 	case XFRM_MODE_TUNNEL:
337 		return xfrm4_tunnel_encap_add(x, skb);
338 	}
339 
340 	WARN_ON_ONCE(1);
341 	return -EOPNOTSUPP;
342 }
343 
344 static int xfrm6_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
345 {
346 #if IS_ENABLED(CONFIG_IPV6)
347 	int err;
348 
349 	err = xfrm_inner_extract_output(x, skb);
350 	if (err)
351 		return err;
352 
353 	skb->ignore_df = 1;
354 	skb->protocol = htons(ETH_P_IPV6);
355 
356 	switch (x->outer_mode.encap) {
357 	case XFRM_MODE_BEET:
358 		return xfrm6_beet_encap_add(x, skb);
359 	case XFRM_MODE_TUNNEL:
360 		return xfrm6_tunnel_encap_add(x, skb);
361 	default:
362 		WARN_ON_ONCE(1);
363 		return -EOPNOTSUPP;
364 	}
365 #endif
366 	WARN_ON_ONCE(1);
367 	return -EAFNOSUPPORT;
368 }
369 
370 static int xfrm_outer_mode_output(struct xfrm_state *x, struct sk_buff *skb)
371 {
372 	switch (x->outer_mode.encap) {
373 	case XFRM_MODE_BEET:
374 	case XFRM_MODE_TUNNEL:
375 		if (x->outer_mode.family == AF_INET)
376 			return xfrm4_prepare_output(x, skb);
377 		if (x->outer_mode.family == AF_INET6)
378 			return xfrm6_prepare_output(x, skb);
379 		break;
380 	case XFRM_MODE_TRANSPORT:
381 		if (x->outer_mode.family == AF_INET)
382 			return xfrm4_transport_output(x, skb);
383 		if (x->outer_mode.family == AF_INET6)
384 			return xfrm6_transport_output(x, skb);
385 		break;
386 	case XFRM_MODE_ROUTEOPTIMIZATION:
387 		if (x->outer_mode.family == AF_INET6)
388 			return xfrm6_ro_output(x, skb);
389 		WARN_ON_ONCE(1);
390 		break;
391 	default:
392 		WARN_ON_ONCE(1);
393 		break;
394 	}
395 
396 	return -EOPNOTSUPP;
397 }
398 
399 #if IS_ENABLED(CONFIG_NET_PKTGEN)
400 int pktgen_xfrm_outer_mode_output(struct xfrm_state *x, struct sk_buff *skb)
401 {
402 	return xfrm_outer_mode_output(x, skb);
403 }
404 EXPORT_SYMBOL_GPL(pktgen_xfrm_outer_mode_output);
405 #endif
406 
407 static int xfrm_output_one(struct sk_buff *skb, int err)
408 {
409 	struct dst_entry *dst = skb_dst(skb);
410 	struct xfrm_state *x = dst->xfrm;
411 	struct net *net = xs_net(x);
412 
413 	if (err <= 0)
414 		goto resume;
415 
416 	do {
417 		err = xfrm_skb_check_space(skb);
418 		if (err) {
419 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
420 			goto error_nolock;
421 		}
422 
423 		skb->mark = xfrm_smark_get(skb->mark, x);
424 
425 		err = xfrm_outer_mode_output(x, skb);
426 		if (err) {
427 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEMODEERROR);
428 			goto error_nolock;
429 		}
430 
431 		spin_lock_bh(&x->lock);
432 
433 		if (unlikely(x->km.state != XFRM_STATE_VALID)) {
434 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEINVALID);
435 			err = -EINVAL;
436 			goto error;
437 		}
438 
439 		err = xfrm_state_check_expire(x);
440 		if (err) {
441 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEEXPIRED);
442 			goto error;
443 		}
444 
445 		err = x->repl->overflow(x, skb);
446 		if (err) {
447 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATESEQERROR);
448 			goto error;
449 		}
450 
451 		x->curlft.bytes += skb->len;
452 		x->curlft.packets++;
453 
454 		spin_unlock_bh(&x->lock);
455 
456 		skb_dst_force(skb);
457 		if (!skb_dst(skb)) {
458 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
459 			err = -EHOSTUNREACH;
460 			goto error_nolock;
461 		}
462 
463 		if (xfrm_offload(skb)) {
464 			x->type_offload->encap(x, skb);
465 		} else {
466 			/* Inner headers are invalid now. */
467 			skb->encapsulation = 0;
468 
469 			err = x->type->output(x, skb);
470 			if (err == -EINPROGRESS)
471 				goto out;
472 		}
473 
474 resume:
475 		if (err) {
476 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTSTATEPROTOERROR);
477 			goto error_nolock;
478 		}
479 
480 		dst = skb_dst_pop(skb);
481 		if (!dst) {
482 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
483 			err = -EHOSTUNREACH;
484 			goto error_nolock;
485 		}
486 		skb_dst_set(skb, dst);
487 		x = dst->xfrm;
488 	} while (x && !(x->outer_mode.flags & XFRM_MODE_FLAG_TUNNEL));
489 
490 	return 0;
491 
492 error:
493 	spin_unlock_bh(&x->lock);
494 error_nolock:
495 	kfree_skb(skb);
496 out:
497 	return err;
498 }
499 
500 int xfrm_output_resume(struct sk_buff *skb, int err)
501 {
502 	struct net *net = xs_net(skb_dst(skb)->xfrm);
503 
504 	while (likely((err = xfrm_output_one(skb, err)) == 0)) {
505 		nf_reset_ct(skb);
506 
507 		err = skb_dst(skb)->ops->local_out(net, skb->sk, skb);
508 		if (unlikely(err != 1))
509 			goto out;
510 
511 		if (!skb_dst(skb)->xfrm)
512 			return dst_output(net, skb->sk, skb);
513 
514 		err = nf_hook(skb_dst(skb)->ops->family,
515 			      NF_INET_POST_ROUTING, net, skb->sk, skb,
516 			      NULL, skb_dst(skb)->dev, xfrm_output2);
517 		if (unlikely(err != 1))
518 			goto out;
519 	}
520 
521 	if (err == -EINPROGRESS)
522 		err = 0;
523 
524 out:
525 	return err;
526 }
527 EXPORT_SYMBOL_GPL(xfrm_output_resume);
528 
529 static int xfrm_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
530 {
531 	return xfrm_output_resume(skb, 1);
532 }
533 
534 static int xfrm_output_gso(struct net *net, struct sock *sk, struct sk_buff *skb)
535 {
536 	struct sk_buff *segs, *nskb;
537 
538 	BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);
539 	BUILD_BUG_ON(sizeof(*IP6CB(skb)) > SKB_SGO_CB_OFFSET);
540 	segs = skb_gso_segment(skb, 0);
541 	kfree_skb(skb);
542 	if (IS_ERR(segs))
543 		return PTR_ERR(segs);
544 	if (segs == NULL)
545 		return -EINVAL;
546 
547 	skb_list_walk_safe(segs, segs, nskb) {
548 		int err;
549 
550 		skb_mark_not_on_list(segs);
551 		err = xfrm_output2(net, sk, segs);
552 
553 		if (unlikely(err)) {
554 			kfree_skb_list(nskb);
555 			return err;
556 		}
557 	}
558 
559 	return 0;
560 }
561 
562 int xfrm_output(struct sock *sk, struct sk_buff *skb)
563 {
564 	struct net *net = dev_net(skb_dst(skb)->dev);
565 	struct xfrm_state *x = skb_dst(skb)->xfrm;
566 	int err;
567 
568 	secpath_reset(skb);
569 
570 	if (xfrm_dev_offload_ok(skb, x)) {
571 		struct sec_path *sp;
572 
573 		sp = secpath_set(skb);
574 		if (!sp) {
575 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
576 			kfree_skb(skb);
577 			return -ENOMEM;
578 		}
579 		skb->encapsulation = 1;
580 
581 		sp->olen++;
582 		sp->xvec[sp->len++] = x;
583 		xfrm_state_hold(x);
584 
585 		if (skb_is_gso(skb)) {
586 			skb_shinfo(skb)->gso_type |= SKB_GSO_ESP;
587 
588 			return xfrm_output2(net, sk, skb);
589 		}
590 
591 		if (x->xso.dev && x->xso.dev->features & NETIF_F_HW_ESP_TX_CSUM)
592 			goto out;
593 	}
594 
595 	if (skb_is_gso(skb))
596 		return xfrm_output_gso(net, sk, skb);
597 
598 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
599 		err = skb_checksum_help(skb);
600 		if (err) {
601 			XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR);
602 			kfree_skb(skb);
603 			return err;
604 		}
605 	}
606 
607 out:
608 	return xfrm_output2(net, sk, skb);
609 }
610 EXPORT_SYMBOL_GPL(xfrm_output);
611 
612 static int xfrm_inner_extract_output(struct xfrm_state *x, struct sk_buff *skb)
613 {
614 	const struct xfrm_state_afinfo *afinfo;
615 	const struct xfrm_mode *inner_mode;
616 	int err = -EAFNOSUPPORT;
617 
618 	if (x->sel.family == AF_UNSPEC)
619 		inner_mode = xfrm_ip2inner_mode(x,
620 				xfrm_af2proto(skb_dst(skb)->ops->family));
621 	else
622 		inner_mode = &x->inner_mode;
623 
624 	if (inner_mode == NULL)
625 		return -EAFNOSUPPORT;
626 
627 	rcu_read_lock();
628 	afinfo = xfrm_state_afinfo_get_rcu(inner_mode->family);
629 	if (likely(afinfo))
630 		err = afinfo->extract_output(x, skb);
631 	rcu_read_unlock();
632 
633 	return err;
634 }
635 
636 void xfrm_local_error(struct sk_buff *skb, int mtu)
637 {
638 	unsigned int proto;
639 	struct xfrm_state_afinfo *afinfo;
640 
641 	if (skb->protocol == htons(ETH_P_IP))
642 		proto = AF_INET;
643 	else if (skb->protocol == htons(ETH_P_IPV6))
644 		proto = AF_INET6;
645 	else
646 		return;
647 
648 	afinfo = xfrm_state_get_afinfo(proto);
649 	if (afinfo) {
650 		afinfo->local_error(skb, mtu);
651 		rcu_read_unlock();
652 	}
653 }
654 EXPORT_SYMBOL_GPL(xfrm_local_error);
655