xref: /openbmc/linux/net/ipv6/seg6_iptunnel.c (revision e0f6d1a5) 
1 /*
2  *  SR-IPv6 implementation
3  *
4  *  Author:
5  *  David Lebrun <david.lebrun@uclouvain.be>
6  *
7  *
8  *  This program is free software; you can redistribute it and/or
9  *        modify it under the terms of the GNU General Public License
10  *        as published by the Free Software Foundation; either version
11  *        2 of the License, or (at your option) any later version.
12  */
13 
14 #include <linux/types.h>
15 #include <linux/skbuff.h>
16 #include <linux/net.h>
17 #include <linux/module.h>
18 #include <net/ip.h>
19 #include <net/ip_tunnels.h>
20 #include <net/lwtunnel.h>
21 #include <net/netevent.h>
22 #include <net/netns/generic.h>
23 #include <net/ip6_fib.h>
24 #include <net/route.h>
25 #include <net/seg6.h>
26 #include <linux/seg6.h>
27 #include <linux/seg6_iptunnel.h>
28 #include <net/addrconf.h>
29 #include <net/ip6_route.h>
30 #include <net/dst_cache.h>
31 #ifdef CONFIG_IPV6_SEG6_HMAC
32 #include <net/seg6_hmac.h>
33 #endif
34 
35 struct seg6_lwt {
36 	struct dst_cache cache;
37 	struct seg6_iptunnel_encap tuninfo[0];
38 };
39 
40 static inline struct seg6_lwt *seg6_lwt_lwtunnel(struct lwtunnel_state *lwt)
41 {
42 	return (struct seg6_lwt *)lwt->data;
43 }
44 
45 static inline struct seg6_iptunnel_encap *
46 seg6_encap_lwtunnel(struct lwtunnel_state *lwt)
47 {
48 	return seg6_lwt_lwtunnel(lwt)->tuninfo;
49 }
50 
51 static const struct nla_policy seg6_iptunnel_policy[SEG6_IPTUNNEL_MAX + 1] = {
52 	[SEG6_IPTUNNEL_SRH]	= { .type = NLA_BINARY },
53 };
54 
55 static int nla_put_srh(struct sk_buff *skb, int attrtype,
56 		       struct seg6_iptunnel_encap *tuninfo)
57 {
58 	struct seg6_iptunnel_encap *data;
59 	struct nlattr *nla;
60 	int len;
61 
62 	len = SEG6_IPTUN_ENCAP_SIZE(tuninfo);
63 
64 	nla = nla_reserve(skb, attrtype, len);
65 	if (!nla)
66 		return -EMSGSIZE;
67 
68 	data = nla_data(nla);
69 	memcpy(data, tuninfo, len);
70 
71 	return 0;
72 }
73 
74 static void set_tun_src(struct net *net, struct net_device *dev,
75 			struct in6_addr *daddr, struct in6_addr *saddr)
76 {
77 	struct seg6_pernet_data *sdata = seg6_pernet(net);
78 	struct in6_addr *tun_src;
79 
80 	rcu_read_lock();
81 
82 	tun_src = rcu_dereference(sdata->tun_src);
83 
84 	if (!ipv6_addr_any(tun_src)) {
85 		memcpy(saddr, tun_src, sizeof(struct in6_addr));
86 	} else {
87 		ipv6_dev_get_saddr(net, dev, daddr, IPV6_PREFER_SRC_PUBLIC,
88 				   saddr);
89 	}
90 
91 	rcu_read_unlock();
92 }
93 
94 /* encapsulate an IPv6 packet within an outer IPv6 header with a given SRH */
95 int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto)
96 {
97 	struct dst_entry *dst = skb_dst(skb);
98 	struct net *net = dev_net(dst->dev);
99 	struct ipv6hdr *hdr, *inner_hdr;
100 	struct ipv6_sr_hdr *isrh;
101 	int hdrlen, tot_len, err;
102 
103 	hdrlen = (osrh->hdrlen + 1) << 3;
104 	tot_len = hdrlen + sizeof(*hdr);
105 
106 	err = skb_cow_head(skb, tot_len);
107 	if (unlikely(err))
108 		return err;
109 
110 	inner_hdr = ipv6_hdr(skb);
111 
112 	skb_push(skb, tot_len);
113 	skb_reset_network_header(skb);
114 	skb_mac_header_rebuild(skb);
115 	hdr = ipv6_hdr(skb);
116 
117 	/* inherit tc, flowlabel and hlim
118 	 * hlim will be decremented in ip6_forward() afterwards and
119 	 * decapsulation will overwrite inner hlim with outer hlim
120 	 */
121 
122 	if (skb->protocol == htons(ETH_P_IPV6)) {
123 		ip6_flow_hdr(hdr, ip6_tclass(ip6_flowinfo(inner_hdr)),
124 			     ip6_flowlabel(inner_hdr));
125 		hdr->hop_limit = inner_hdr->hop_limit;
126 	} else {
127 		ip6_flow_hdr(hdr, 0, 0);
128 		hdr->hop_limit = ip6_dst_hoplimit(skb_dst(skb));
129 	}
130 
131 	hdr->nexthdr = NEXTHDR_ROUTING;
132 
133 	isrh = (void *)hdr + sizeof(*hdr);
134 	memcpy(isrh, osrh, hdrlen);
135 
136 	isrh->nexthdr = proto;
137 
138 	hdr->daddr = isrh->segments[isrh->first_segment];
139 	set_tun_src(net, dst->dev, &hdr->daddr, &hdr->saddr);
140 
141 #ifdef CONFIG_IPV6_SEG6_HMAC
142 	if (sr_has_hmac(isrh)) {
143 		err = seg6_push_hmac(net, &hdr->saddr, isrh);
144 		if (unlikely(err))
145 			return err;
146 	}
147 #endif
148 
149 	skb_postpush_rcsum(skb, hdr, tot_len);
150 
151 	return 0;
152 }
153 EXPORT_SYMBOL_GPL(seg6_do_srh_encap);
154 
155 /* insert an SRH within an IPv6 packet, just after the IPv6 header */
156 int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
157 {
158 	struct ipv6hdr *hdr, *oldhdr;
159 	struct ipv6_sr_hdr *isrh;
160 	int hdrlen, err;
161 
162 	hdrlen = (osrh->hdrlen + 1) << 3;
163 
164 	err = skb_cow_head(skb, hdrlen);
165 	if (unlikely(err))
166 		return err;
167 
168 	oldhdr = ipv6_hdr(skb);
169 
170 	skb_pull(skb, sizeof(struct ipv6hdr));
171 	skb_postpull_rcsum(skb, skb_network_header(skb),
172 			   sizeof(struct ipv6hdr));
173 
174 	skb_push(skb, sizeof(struct ipv6hdr) + hdrlen);
175 	skb_reset_network_header(skb);
176 	skb_mac_header_rebuild(skb);
177 
178 	hdr = ipv6_hdr(skb);
179 
180 	memmove(hdr, oldhdr, sizeof(*hdr));
181 
182 	isrh = (void *)hdr + sizeof(*hdr);
183 	memcpy(isrh, osrh, hdrlen);
184 
185 	isrh->nexthdr = hdr->nexthdr;
186 	hdr->nexthdr = NEXTHDR_ROUTING;
187 
188 	isrh->segments[0] = hdr->daddr;
189 	hdr->daddr = isrh->segments[isrh->first_segment];
190 
191 #ifdef CONFIG_IPV6_SEG6_HMAC
192 	if (sr_has_hmac(isrh)) {
193 		struct net *net = dev_net(skb_dst(skb)->dev);
194 
195 		err = seg6_push_hmac(net, &hdr->saddr, isrh);
196 		if (unlikely(err))
197 			return err;
198 	}
199 #endif
200 
201 	skb_postpush_rcsum(skb, hdr, sizeof(struct ipv6hdr) + hdrlen);
202 
203 	return 0;
204 }
205 EXPORT_SYMBOL_GPL(seg6_do_srh_inline);
206 
207 static int seg6_do_srh(struct sk_buff *skb)
208 {
209 	struct dst_entry *dst = skb_dst(skb);
210 	struct seg6_iptunnel_encap *tinfo;
211 	int proto, err = 0;
212 
213 	tinfo = seg6_encap_lwtunnel(dst->lwtstate);
214 
215 	switch (tinfo->mode) {
216 	case SEG6_IPTUN_MODE_INLINE:
217 		if (skb->protocol != htons(ETH_P_IPV6))
218 			return -EINVAL;
219 
220 		err = seg6_do_srh_inline(skb, tinfo->srh);
221 		if (err)
222 			return err;
223 		break;
224 	case SEG6_IPTUN_MODE_ENCAP:
225 		err = iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6);
226 		if (err)
227 			return err;
228 
229 		if (skb->protocol == htons(ETH_P_IPV6))
230 			proto = IPPROTO_IPV6;
231 		else if (skb->protocol == htons(ETH_P_IP))
232 			proto = IPPROTO_IPIP;
233 		else
234 			return -EINVAL;
235 
236 		err = seg6_do_srh_encap(skb, tinfo->srh, proto);
237 		if (err)
238 			return err;
239 
240 		skb_set_inner_transport_header(skb, skb_transport_offset(skb));
241 		skb_set_inner_protocol(skb, skb->protocol);
242 		skb->protocol = htons(ETH_P_IPV6);
243 		break;
244 	case SEG6_IPTUN_MODE_L2ENCAP:
245 		if (!skb_mac_header_was_set(skb))
246 			return -EINVAL;
247 
248 		if (pskb_expand_head(skb, skb->mac_len, 0, GFP_ATOMIC) < 0)
249 			return -ENOMEM;
250 
251 		skb_mac_header_rebuild(skb);
252 		skb_push(skb, skb->mac_len);
253 
254 		err = seg6_do_srh_encap(skb, tinfo->srh, NEXTHDR_NONE);
255 		if (err)
256 			return err;
257 
258 		skb->protocol = htons(ETH_P_IPV6);
259 		break;
260 	}
261 
262 	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
263 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
264 
265 	return 0;
266 }
267 
268 static int seg6_input(struct sk_buff *skb)
269 {
270 	struct dst_entry *orig_dst = skb_dst(skb);
271 	struct dst_entry *dst = NULL;
272 	struct seg6_lwt *slwt;
273 	int err;
274 
275 	err = seg6_do_srh(skb);
276 	if (unlikely(err)) {
277 		kfree_skb(skb);
278 		return err;
279 	}
280 
281 	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
282 
283 	preempt_disable();
284 	dst = dst_cache_get(&slwt->cache);
285 	preempt_enable();
286 
287 	skb_dst_drop(skb);
288 
289 	if (!dst) {
290 		ip6_route_input(skb);
291 		dst = skb_dst(skb);
292 		if (!dst->error) {
293 			preempt_disable();
294 			dst_cache_set_ip6(&slwt->cache, dst,
295 					  &ipv6_hdr(skb)->saddr);
296 			preempt_enable();
297 		}
298 	} else {
299 		skb_dst_set(skb, dst);
300 	}
301 
302 	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
303 	if (unlikely(err))
304 		return err;
305 
306 	return dst_input(skb);
307 }
308 
309 static int seg6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
310 {
311 	struct dst_entry *orig_dst = skb_dst(skb);
312 	struct dst_entry *dst = NULL;
313 	struct seg6_lwt *slwt;
314 	int err = -EINVAL;
315 
316 	err = seg6_do_srh(skb);
317 	if (unlikely(err))
318 		goto drop;
319 
320 	slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
321 
322 	preempt_disable();
323 	dst = dst_cache_get(&slwt->cache);
324 	preempt_enable();
325 
326 	if (unlikely(!dst)) {
327 		struct ipv6hdr *hdr = ipv6_hdr(skb);
328 		struct flowi6 fl6;
329 
330 		fl6.daddr = hdr->daddr;
331 		fl6.saddr = hdr->saddr;
332 		fl6.flowlabel = ip6_flowinfo(hdr);
333 		fl6.flowi6_mark = skb->mark;
334 		fl6.flowi6_proto = hdr->nexthdr;
335 
336 		dst = ip6_route_output(net, NULL, &fl6);
337 		if (dst->error) {
338 			err = dst->error;
339 			dst_release(dst);
340 			goto drop;
341 		}
342 
343 		preempt_disable();
344 		dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
345 		preempt_enable();
346 	}
347 
348 	skb_dst_drop(skb);
349 	skb_dst_set(skb, dst);
350 
351 	err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
352 	if (unlikely(err))
353 		goto drop;
354 
355 	return dst_output(net, sk, skb);
356 drop:
357 	kfree_skb(skb);
358 	return err;
359 }
360 
361 static int seg6_build_state(struct nlattr *nla,
362 			    unsigned int family, const void *cfg,
363 			    struct lwtunnel_state **ts,
364 			    struct netlink_ext_ack *extack)
365 {
366 	struct nlattr *tb[SEG6_IPTUNNEL_MAX + 1];
367 	struct seg6_iptunnel_encap *tuninfo;
368 	struct lwtunnel_state *newts;
369 	int tuninfo_len, min_size;
370 	struct seg6_lwt *slwt;
371 	int err;
372 
373 	if (family != AF_INET && family != AF_INET6)
374 		return -EINVAL;
375 
376 	err = nla_parse_nested(tb, SEG6_IPTUNNEL_MAX, nla,
377 			       seg6_iptunnel_policy, extack);
378 
379 	if (err < 0)
380 		return err;
381 
382 	if (!tb[SEG6_IPTUNNEL_SRH])
383 		return -EINVAL;
384 
385 	tuninfo = nla_data(tb[SEG6_IPTUNNEL_SRH]);
386 	tuninfo_len = nla_len(tb[SEG6_IPTUNNEL_SRH]);
387 
388 	/* tuninfo must contain at least the iptunnel encap structure,
389 	 * the SRH and one segment
390 	 */
391 	min_size = sizeof(*tuninfo) + sizeof(struct ipv6_sr_hdr) +
392 		   sizeof(struct in6_addr);
393 	if (tuninfo_len < min_size)
394 		return -EINVAL;
395 
396 	switch (tuninfo->mode) {
397 	case SEG6_IPTUN_MODE_INLINE:
398 		if (family != AF_INET6)
399 			return -EINVAL;
400 
401 		break;
402 	case SEG6_IPTUN_MODE_ENCAP:
403 		break;
404 	case SEG6_IPTUN_MODE_L2ENCAP:
405 		break;
406 	default:
407 		return -EINVAL;
408 	}
409 
410 	/* verify that SRH is consistent */
411 	if (!seg6_validate_srh(tuninfo->srh, tuninfo_len - sizeof(*tuninfo)))
412 		return -EINVAL;
413 
414 	newts = lwtunnel_state_alloc(tuninfo_len + sizeof(*slwt));
415 	if (!newts)
416 		return -ENOMEM;
417 
418 	slwt = seg6_lwt_lwtunnel(newts);
419 
420 	err = dst_cache_init(&slwt->cache, GFP_ATOMIC);
421 	if (err) {
422 		kfree(newts);
423 		return err;
424 	}
425 
426 	memcpy(&slwt->tuninfo, tuninfo, tuninfo_len);
427 
428 	newts->type = LWTUNNEL_ENCAP_SEG6;
429 	newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
430 
431 	if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP)
432 		newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
433 
434 	newts->headroom = seg6_lwt_headroom(tuninfo);
435 
436 	*ts = newts;
437 
438 	return 0;
439 }
440 
441 static void seg6_destroy_state(struct lwtunnel_state *lwt)
442 {
443 	dst_cache_destroy(&seg6_lwt_lwtunnel(lwt)->cache);
444 }
445 
446 static int seg6_fill_encap_info(struct sk_buff *skb,
447 				struct lwtunnel_state *lwtstate)
448 {
449 	struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);
450 
451 	if (nla_put_srh(skb, SEG6_IPTUNNEL_SRH, tuninfo))
452 		return -EMSGSIZE;
453 
454 	return 0;
455 }
456 
457 static int seg6_encap_nlsize(struct lwtunnel_state *lwtstate)
458 {
459 	struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);
460 
461 	return nla_total_size(SEG6_IPTUN_ENCAP_SIZE(tuninfo));
462 }
463 
464 static int seg6_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
465 {
466 	struct seg6_iptunnel_encap *a_hdr = seg6_encap_lwtunnel(a);
467 	struct seg6_iptunnel_encap *b_hdr = seg6_encap_lwtunnel(b);
468 	int len = SEG6_IPTUN_ENCAP_SIZE(a_hdr);
469 
470 	if (len != SEG6_IPTUN_ENCAP_SIZE(b_hdr))
471 		return 1;
472 
473 	return memcmp(a_hdr, b_hdr, len);
474 }
475 
476 static const struct lwtunnel_encap_ops seg6_iptun_ops = {
477 	.build_state = seg6_build_state,
478 	.destroy_state = seg6_destroy_state,
479 	.output = seg6_output,
480 	.input = seg6_input,
481 	.fill_encap = seg6_fill_encap_info,
482 	.get_encap_size = seg6_encap_nlsize,
483 	.cmp_encap = seg6_encap_cmp,
484 	.owner = THIS_MODULE,
485 };
486 
487 int __init seg6_iptunnel_init(void)
488 {
489 	return lwtunnel_encap_add_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
490 }
491 
492 void seg6_iptunnel_exit(void)
493 {
494 	lwtunnel_encap_del_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
495 }
496