xref: /openbmc/linux/net/ipv6/seg6_iptunnel.c (revision b1a3e75e) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *  SR-IPv6 implementation
4  *
5  *  Author:
6  *  David Lebrun <david.lebrun@uclouvain.be>
7  */
8 
9 #include <linux/types.h>
10 #include <linux/skbuff.h>
11 #include <linux/net.h>
12 #include <linux/module.h>
13 #include <net/ip.h>
14 #include <net/ip_tunnels.h>
15 #include <net/lwtunnel.h>
16 #include <net/netevent.h>
17 #include <net/netns/generic.h>
18 #include <net/ip6_fib.h>
19 #include <net/route.h>
20 #include <net/seg6.h>
21 #include <linux/seg6.h>
22 #include <linux/seg6_iptunnel.h>
23 #include <net/addrconf.h>
24 #include <net/ip6_route.h>
25 #include <net/dst_cache.h>
26 #ifdef CONFIG_IPV6_SEG6_HMAC
27 #include <net/seg6_hmac.h>
28 #endif
29 
30 static size_t seg6_lwt_headroom(struct seg6_iptunnel_encap *tuninfo)
31 {
32 	int head = 0;
33 
34 	switch (tuninfo->mode) {
35 	case SEG6_IPTUN_MODE_INLINE:
36 		break;
37 	case SEG6_IPTUN_MODE_ENCAP:
38 		head = sizeof(struct ipv6hdr);
39 		break;
40 	case SEG6_IPTUN_MODE_L2ENCAP:
41 		return 0;
42 	}
43 
44 	return ((tuninfo->srh->hdrlen + 1) << 3) + head;
45 }
46 
47 struct seg6_lwt {
48 	struct dst_cache cache;
49 	struct seg6_iptunnel_encap tuninfo[];
50 };
51 
52 static inline struct seg6_lwt *seg6_lwt_lwtunnel(struct lwtunnel_state *lwt)
53 {
54 	return (struct seg6_lwt *)lwt->data;
55 }
56 
57 static inline struct seg6_iptunnel_encap *
58 seg6_encap_lwtunnel(struct lwtunnel_state *lwt)
59 {
60 	return seg6_lwt_lwtunnel(lwt)->tuninfo;
61 }
62 
63 static const struct nla_policy seg6_iptunnel_policy[SEG6_IPTUNNEL_MAX + 1] = {
64 	[SEG6_IPTUNNEL_SRH]	= { .type = NLA_BINARY },
65 };
66 
67 static int nla_put_srh(struct sk_buff *skb, int attrtype,
68 		       struct seg6_iptunnel_encap *tuninfo)
69 {
70 	struct seg6_iptunnel_encap *data;
71 	struct nlattr *nla;
72 	int len;
73 
74 	len = SEG6_IPTUN_ENCAP_SIZE(tuninfo);
75 
76 	nla = nla_reserve(skb, attrtype, len);
77 	if (!nla)
78 		return -EMSGSIZE;
79 
80 	data = nla_data(nla);
81 	memcpy(data, tuninfo, len);
82 
83 	return 0;
84 }
85 
86 static void set_tun_src(struct net *net, struct net_device *dev,
87 			struct in6_addr *daddr, struct in6_addr *saddr)
88 {
89 	struct seg6_pernet_data *sdata = seg6_pernet(net);
90 	struct in6_addr *tun_src;
91 
92 	rcu_read_lock();
93 
94 	tun_src = rcu_dereference(sdata->tun_src);
95 
96 	if (!ipv6_addr_any(tun_src)) {
97 		memcpy(saddr, tun_src, sizeof(struct in6_addr));
98 	} else {
99 		ipv6_dev_get_saddr(net, dev, daddr, IPV6_PREFER_SRC_PUBLIC,
100 				   saddr);
101 	}
102 
103 	rcu_read_unlock();
104 }
105 
106 /* Compute flowlabel for outer IPv6 header */
107 static __be32 seg6_make_flowlabel(struct net *net, struct sk_buff *skb,
108 				  struct ipv6hdr *inner_hdr)
109 {
110 	int do_flowlabel = net->ipv6.sysctl.seg6_flowlabel;
111 	__be32 flowlabel = 0;
112 	u32 hash;
113 
114 	if (do_flowlabel > 0) {
115 		hash = skb_get_hash(skb);
116 		hash = rol32(hash, 16);
117 		flowlabel = (__force __be32)hash & IPV6_FLOWLABEL_MASK;
118 	} else if (!do_flowlabel && skb->protocol == htons(ETH_P_IPV6)) {
119 		flowlabel = ip6_flowlabel(inner_hdr);
120 	}
121 	return flowlabel;
122 }
123 
124 /* encapsulate an IPv6 packet within an outer IPv6 header with a given SRH */
125 int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto)
126 {
127 	struct dst_entry *dst = skb_dst(skb);
128 	struct net *net = dev_net(dst->dev);
129 	struct ipv6hdr *hdr, *inner_hdr;
130 	struct ipv6_sr_hdr *isrh;
131 	int hdrlen, tot_len, err;
132 	__be32 flowlabel;
133 
134 	hdrlen = (osrh->hdrlen + 1) << 3;
135 	tot_len = hdrlen + sizeof(*hdr);
136 
137 	err = skb_cow_head(skb, tot_len + skb->mac_len);
138 	if (unlikely(err))
139 		return err;
140 
141 	inner_hdr = ipv6_hdr(skb);
142 	flowlabel = seg6_make_flowlabel(net, skb, inner_hdr);
143 
144 	skb_push(skb, tot_len);
145 	skb_reset_network_header(skb);
146 	skb_mac_header_rebuild(skb);
147 	hdr = ipv6_hdr(skb);
148 
149 	/* inherit tc, flowlabel and hlim
150 	 * hlim will be decremented in ip6_forward() afterwards and
151 	 * decapsulation will overwrite inner hlim with outer hlim
152 	 */
153 
154 	if (skb->protocol == htons(ETH_P_IPV6)) {
155 		ip6_flow_hdr(hdr, ip6_tclass(ip6_flowinfo(inner_hdr)),
156 			     flowlabel);
157 		hdr->hop_limit = inner_hdr->hop_limit;
158 	} else {
159 		ip6_flow_hdr(hdr, 0, flowlabel);
160 		hdr->hop_limit = ip6_dst_hoplimit(skb_dst(skb));
161 
162 		memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
163 	}
164 
165 	hdr->nexthdr = NEXTHDR_ROUTING;
166 
167 	isrh = (void *)hdr + sizeof(*hdr);
168 	memcpy(isrh, osrh, hdrlen);
169 
170 	isrh->nexthdr = proto;
171 
172 	hdr->daddr = isrh->segments[isrh->first_segment];
173 	set_tun_src(net, dst->dev, &hdr->daddr, &hdr->saddr);
174 
175 #ifdef CONFIG_IPV6_SEG6_HMAC
176 	if (sr_has_hmac(isrh)) {
177 		err = seg6_push_hmac(net, &hdr->saddr, isrh);
178 		if (unlikely(err))
179 			return err;
180 	}
181 #endif
182 
183 	skb_postpush_rcsum(skb, hdr, tot_len);
184 
185 	return 0;
186 }
187 EXPORT_SYMBOL_GPL(seg6_do_srh_encap);
188 
189 /* insert an SRH within an IPv6 packet, just after the IPv6 header */
190 int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
191 {
192 	struct ipv6hdr *hdr, *oldhdr;
193 	struct ipv6_sr_hdr *isrh;
194 	int hdrlen, err;
195 
196 	hdrlen = (osrh->hdrlen + 1) << 3;
197 
198 	err = skb_cow_head(skb, hdrlen + skb->mac_len);
199 	if (unlikely(err))
200 		return err;
201 
202 	oldhdr = ipv6_hdr(skb);
203 
204 	skb_pull(skb, sizeof(struct ipv6hdr));
205 	skb_postpull_rcsum(skb, skb_network_header(skb),
206 			   sizeof(struct ipv6hdr));
207 
208 	skb_push(skb, sizeof(struct ipv6hdr) + hdrlen);
209 	skb_reset_network_header(skb);
210 	skb_mac_header_rebuild(skb);
211 
212 	hdr = ipv6_hdr(skb);
213 
214 	memmove(hdr, oldhdr, sizeof(*hdr));
215 
216 	isrh = (void *)hdr + sizeof(*hdr);
217 	memcpy(isrh, osrh, hdrlen);
218 
219 	isrh->nexthdr = hdr->nexthdr;
220 	hdr->nexthdr = NEXTHDR_ROUTING;
221 
222 	isrh->segments[0] = hdr->daddr;
223 	hdr->daddr = isrh->segments[isrh->first_segment];
224 
225 #ifdef CONFIG_IPV6_SEG6_HMAC
226 	if (sr_has_hmac(isrh)) {
227 		struct net *net = dev_net(skb_dst(skb)->dev);
228 
229 		err = seg6_push_hmac(net, &hdr->saddr, isrh);
230 		if (unlikely(err))
231 			return err;
232 	}
233 #endif
234 
235 	skb_postpush_rcsum(skb, hdr, sizeof(struct ipv6hdr) + hdrlen);
236 
237 	return 0;
238 }
239 EXPORT_SYMBOL_GPL(seg6_do_srh_inline);
240 
241 static int seg6_do_srh(struct sk_buff *skb)
242 {
243 	struct dst_entry *dst = skb_dst(skb);
244 	struct seg6_iptunnel_encap *tinfo;
245 	int proto, err = 0;
246 
247 	tinfo = seg6_encap_lwtunnel(dst->lwtstate);
248 
249 	switch (tinfo->mode) {
250 	case SEG6_IPTUN_MODE_INLINE:
251 		if (skb->protocol != htons(ETH_P_IPV6))
252 			return -EINVAL;
253 
254 		err = seg6_do_srh_inline(skb, tinfo->srh);
255 		if (err)
256 			return err;
257 		break;
258 	case SEG6_IPTUN_MODE_ENCAP:
259 		err = iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6);
260 		if (err)
261 			return err;
262 
263 		if (skb->protocol == htons(ETH_P_IPV6))
264 			proto = IPPROTO_IPV6;
265 		else if (skb->protocol == htons(ETH_P_IP))
266 			proto = IPPROTO_IPIP;
267 		else
268 			return -EINVAL;
269 
270 		err = seg6_do_srh_encap(skb, tinfo->srh, proto);
271 		if (err)
272 			return err;
273 
274 		skb_set_inner_transport_header(skb, skb_transport_offset(skb));
275 		skb_set_inner_protocol(skb, skb->protocol);
276 		skb->protocol = htons(ETH_P_IPV6);
277 		break;
278 	case SEG6_IPTUN_MODE_L2ENCAP:
279 		if (!skb_mac_header_was_set(skb))
280 			return -EINVAL;
281 
282 		if (pskb_expand_head(skb, skb->mac_len, 0, GFP_ATOMIC) < 0)
283 			return -ENOMEM;
284 
285 		skb_mac_header_rebuild(skb);
286 		skb_push(skb, skb->mac_len);
287 
288 		err = seg6_do_srh_encap(skb, tinfo->srh, IPPROTO_ETHERNET);
289 		if (err)
290 			return err;
291 
292 		skb->protocol = htons(ETH_P_IPV6);
293 		break;
294 	}
295 
296 	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
297 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
298 
299 	return 0;
300 }
301 
302 static int seg6_input(struct sk_buff *skb)
303 {
304 	struct dst_entry *orig_dst = skb_dst(skb);
305 	struct dst_entry *dst = NULL;
306 	struct seg6_lwt *slwt;
307 	int err;
308 
309 	err = seg6_do_srh(skb);
310 	if (unlikely(err)) {
311 		kfree_skb(skb);
312 		return err;
313 	}
314 
315 	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
316 
317 	preempt_disable();
318 	dst = dst_cache_get(&slwt->cache);
319 	preempt_enable();
320 
321 	skb_dst_drop(skb);
322 
323 	if (!dst) {
324 		ip6_route_input(skb);
325 		dst = skb_dst(skb);
326 		if (!dst->error) {
327 			preempt_disable();
328 			dst_cache_set_ip6(&slwt->cache, dst,
329 					  &ipv6_hdr(skb)->saddr);
330 			preempt_enable();
331 		}
332 	} else {
333 		skb_dst_set(skb, dst);
334 	}
335 
336 	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
337 	if (unlikely(err))
338 		return err;
339 
340 	return dst_input(skb);
341 }
342 
343 static int seg6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
344 {
345 	struct dst_entry *orig_dst = skb_dst(skb);
346 	struct dst_entry *dst = NULL;
347 	struct seg6_lwt *slwt;
348 	int err = -EINVAL;
349 
350 	err = seg6_do_srh(skb);
351 	if (unlikely(err))
352 		goto drop;
353 
354 	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
355 
356 	preempt_disable();
357 	dst = dst_cache_get(&slwt->cache);
358 	preempt_enable();
359 
360 	if (unlikely(!dst)) {
361 		struct ipv6hdr *hdr = ipv6_hdr(skb);
362 		struct flowi6 fl6;
363 
364 		memset(&fl6, 0, sizeof(fl6));
365 		fl6.daddr = hdr->daddr;
366 		fl6.saddr = hdr->saddr;
367 		fl6.flowlabel = ip6_flowinfo(hdr);
368 		fl6.flowi6_mark = skb->mark;
369 		fl6.flowi6_proto = hdr->nexthdr;
370 
371 		dst = ip6_route_output(net, NULL, &fl6);
372 		if (dst->error) {
373 			err = dst->error;
374 			dst_release(dst);
375 			goto drop;
376 		}
377 
378 		preempt_disable();
379 		dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
380 		preempt_enable();
381 	}
382 
383 	skb_dst_drop(skb);
384 	skb_dst_set(skb, dst);
385 
386 	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
387 	if (unlikely(err))
388 		goto drop;
389 
390 	return dst_output(net, sk, skb);
391 drop:
392 	kfree_skb(skb);
393 	return err;
394 }
395 
396 static int seg6_build_state(struct net *net, struct nlattr *nla,
397 			    unsigned int family, const void *cfg,
398 			    struct lwtunnel_state **ts,
399 			    struct netlink_ext_ack *extack)
400 {
401 	struct nlattr *tb[SEG6_IPTUNNEL_MAX + 1];
402 	struct seg6_iptunnel_encap *tuninfo;
403 	struct lwtunnel_state *newts;
404 	int tuninfo_len, min_size;
405 	struct seg6_lwt *slwt;
406 	int err;
407 
408 	if (family != AF_INET && family != AF_INET6)
409 		return -EINVAL;
410 
411 	err = nla_parse_nested_deprecated(tb, SEG6_IPTUNNEL_MAX, nla,
412 					  seg6_iptunnel_policy, extack);
413 
414 	if (err < 0)
415 		return err;
416 
417 	if (!tb[SEG6_IPTUNNEL_SRH])
418 		return -EINVAL;
419 
420 	tuninfo = nla_data(tb[SEG6_IPTUNNEL_SRH]);
421 	tuninfo_len = nla_len(tb[SEG6_IPTUNNEL_SRH]);
422 
423 	/* tuninfo must contain at least the iptunnel encap structure,
424 	 * the SRH and one segment
425 	 */
426 	min_size = sizeof(*tuninfo) + sizeof(struct ipv6_sr_hdr) +
427 		   sizeof(struct in6_addr);
428 	if (tuninfo_len < min_size)
429 		return -EINVAL;
430 
431 	switch (tuninfo->mode) {
432 	case SEG6_IPTUN_MODE_INLINE:
433 		if (family != AF_INET6)
434 			return -EINVAL;
435 
436 		break;
437 	case SEG6_IPTUN_MODE_ENCAP:
438 		break;
439 	case SEG6_IPTUN_MODE_L2ENCAP:
440 		break;
441 	default:
442 		return -EINVAL;
443 	}
444 
445 	/* verify that SRH is consistent */
446 	if (!seg6_validate_srh(tuninfo->srh, tuninfo_len - sizeof(*tuninfo), false))
447 		return -EINVAL;
448 
449 	newts = lwtunnel_state_alloc(tuninfo_len + sizeof(*slwt));
450 	if (!newts)
451 		return -ENOMEM;
452 
453 	slwt = seg6_lwt_lwtunnel(newts);
454 
455 	err = dst_cache_init(&slwt->cache, GFP_ATOMIC);
456 	if (err) {
457 		kfree(newts);
458 		return err;
459 	}
460 
461 	memcpy(&slwt->tuninfo, tuninfo, tuninfo_len);
462 
463 	newts->type = LWTUNNEL_ENCAP_SEG6;
464 	newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
465 
466 	if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP)
467 		newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
468 
469 	newts->headroom = seg6_lwt_headroom(tuninfo);
470 
471 	*ts = newts;
472 
473 	return 0;
474 }
475 
476 static void seg6_destroy_state(struct lwtunnel_state *lwt)
477 {
478 	dst_cache_destroy(&seg6_lwt_lwtunnel(lwt)->cache);
479 }
480 
481 static int seg6_fill_encap_info(struct sk_buff *skb,
482 				struct lwtunnel_state *lwtstate)
483 {
484 	struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);
485 
486 	if (nla_put_srh(skb, SEG6_IPTUNNEL_SRH, tuninfo))
487 		return -EMSGSIZE;
488 
489 	return 0;
490 }
491 
492 static int seg6_encap_nlsize(struct lwtunnel_state *lwtstate)
493 {
494 	struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);
495 
496 	return nla_total_size(SEG6_IPTUN_ENCAP_SIZE(tuninfo));
497 }
498 
499 static int seg6_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
500 {
501 	struct seg6_iptunnel_encap *a_hdr = seg6_encap_lwtunnel(a);
502 	struct seg6_iptunnel_encap *b_hdr = seg6_encap_lwtunnel(b);
503 	int len = SEG6_IPTUN_ENCAP_SIZE(a_hdr);
504 
505 	if (len != SEG6_IPTUN_ENCAP_SIZE(b_hdr))
506 		return 1;
507 
508 	return memcmp(a_hdr, b_hdr, len);
509 }
510 
511 static const struct lwtunnel_encap_ops seg6_iptun_ops = {
512 	.build_state = seg6_build_state,
513 	.destroy_state = seg6_destroy_state,
514 	.output = seg6_output,
515 	.input = seg6_input,
516 	.fill_encap = seg6_fill_encap_info,
517 	.get_encap_size = seg6_encap_nlsize,
518 	.cmp_encap = seg6_encap_cmp,
519 	.owner = THIS_MODULE,
520 };
521 
522 int __init seg6_iptunnel_init(void)
523 {
524 	return lwtunnel_encap_add_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
525 }
526 
527 void seg6_iptunnel_exit(void)
528 {
529 	lwtunnel_encap_del_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
530 }
531