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Linux/net/ipv6/seg6_iptunnel.c

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

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