net/ipv6/seg6_iptunnel.c

   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/lwtunnel.h>
  20 #include <net/netevent.h>
  21 #include <net/netns/generic.h>
  22 #include <net/ip6_fib.h>
  23 #include <net/route.h>
  24 #include <net/seg6.h>
  25 #include <linux/seg6.h>
  26 #include <linux/seg6_iptunnel.h>
  27 #include <net/addrconf.h>
  28 #include <net/ip6_route.h>
  29 #include <net/dst_cache.h>
  30 #ifdef CONFIG_IPV6_SEG6_HMAC
  31 #include <net/seg6_hmac.h>
  32 #endif
  33
  34 struct seg6_lwt {
  35         struct dst_cache cache;
  36         struct seg6_iptunnel_encap tuninfo[0];
  37 };
  38
  39 static inline struct seg6_lwt *seg6_lwt_lwtunnel(struct lwtunnel_state *lwt)
  40 {
  41         return (struct seg6_lwt *)lwt->data;
  42 }
  43
  44 static inline struct seg6_iptunnel_encap *
  45 seg6_encap_lwtunnel(struct lwtunnel_state *lwt)
  46 {
  47         return seg6_lwt_lwtunnel(lwt)->tuninfo;
  48 }
  49
  50 static const struct nla_policy seg6_iptunnel_policy[SEG6_IPTUNNEL_MAX + 1] = {
  51         [SEG6_IPTUNNEL_SRH]     = { .type = NLA_BINARY },
  52 };
  53
  54 static int nla_put_srh(struct sk_buff *skb, int attrtype,
  55                        struct seg6_iptunnel_encap *tuninfo)
  56 {
  57         struct seg6_iptunnel_encap *data;
  58         struct nlattr *nla;
  59         int len;
  60
  61         len = SEG6_IPTUN_ENCAP_SIZE(tuninfo);
  62
  63         nla = nla_reserve(skb, attrtype, len);
  64         if (!nla)
  65                 return -EMSGSIZE;
  66
  67         data = nla_data(nla);
  68         memcpy(data, tuninfo, len);
  69
  70         return 0;
  71 }
  72
  73 static void set_tun_src(struct net *net, struct net_device *dev,
  74                         struct in6_addr *daddr, struct in6_addr *saddr)
  75 {
  76         struct seg6_pernet_data *sdata = seg6_pernet(net);
  77         struct in6_addr *tun_src;
  78
  79         rcu_read_lock();
  80
  81         tun_src = rcu_dereference(sdata->tun_src);
  82
  83         if (!ipv6_addr_any(tun_src)) {
  84                 memcpy(saddr, tun_src, sizeof(struct in6_addr));
  85         } else {
  86                 ipv6_dev_get_saddr(net, dev, daddr, IPV6_PREFER_SRC_PUBLIC,
  87                                    saddr);
  88         }
  89
  90         rcu_read_unlock();
  91 }
  92
  93 /* encapsulate an IPv6 packet within an outer IPv6 header with a given SRH */
  94 static int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
  95 {
  96         struct net *net = dev_net(skb_dst(skb)->dev);
  97         struct ipv6hdr *hdr, *inner_hdr;
  98         struct ipv6_sr_hdr *isrh;
  99         int hdrlen, tot_len, err;
 100
 101         hdrlen = (osrh->hdrlen + 1) << 3;
 102         tot_len = hdrlen + sizeof(*hdr);
 103
 104         err = skb_cow_head(skb, tot_len);
 105         if (unlikely(err))
 106                 return err;
 107
 108         inner_hdr = ipv6_hdr(skb);
 109
 110         skb_push(skb, tot_len);
 111         skb_reset_network_header(skb);
 112         skb_mac_header_rebuild(skb);
 113         hdr = ipv6_hdr(skb);
 114
 115         /* inherit tc, flowlabel and hlim
 116          * hlim will be decremented in ip6_forward() afterwards and
 117          * decapsulation will overwrite inner hlim with outer hlim
 118          */
 119         ip6_flow_hdr(hdr, ip6_tclass(ip6_flowinfo(inner_hdr)),
 120                      ip6_flowlabel(inner_hdr));
 121         hdr->hop_limit = inner_hdr->hop_limit;
 122         hdr->nexthdr = NEXTHDR_ROUTING;
 123
 124         isrh = (void *)hdr + sizeof(*hdr);
 125         memcpy(isrh, osrh, hdrlen);
 126
 127         isrh->nexthdr = NEXTHDR_IPV6;
 128
 129         hdr->daddr = isrh->segments[isrh->first_segment];
 130         set_tun_src(net, skb->dev, &hdr->daddr, &hdr->saddr);
 131
 132 #ifdef CONFIG_IPV6_SEG6_HMAC
 133         if (sr_has_hmac(isrh)) {
 134                 err = seg6_push_hmac(net, &hdr->saddr, isrh);
 135                 if (unlikely(err))
 136                         return err;
 137         }
 138 #endif
 139
 140         skb_postpush_rcsum(skb, hdr, tot_len);
 141
 142         return 0;
 143 }
 144
 145 /* insert an SRH within an IPv6 packet, just after the IPv6 header */
 146 #ifdef CONFIG_IPV6_SEG6_INLINE
 147 static int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
 148 {
 149         struct ipv6hdr *hdr, *oldhdr;
 150         struct ipv6_sr_hdr *isrh;
 151         int hdrlen, err;
 152
 153         hdrlen = (osrh->hdrlen + 1) << 3;
 154
 155         err = skb_cow_head(skb, hdrlen);
 156         if (unlikely(err))
 157                 return err;
 158
 159         oldhdr = ipv6_hdr(skb);
 160
 161         skb_pull(skb, sizeof(struct ipv6hdr));
 162         skb_postpull_rcsum(skb, skb_network_header(skb),
 163                            sizeof(struct ipv6hdr));
 164
 165         skb_push(skb, sizeof(struct ipv6hdr) + hdrlen);
 166         skb_reset_network_header(skb);
 167         skb_mac_header_rebuild(skb);
 168
 169         hdr = ipv6_hdr(skb);
 170
 171         memmove(hdr, oldhdr, sizeof(*hdr));
 172
 173         isrh = (void *)hdr + sizeof(*hdr);
 174         memcpy(isrh, osrh, hdrlen);
 175
 176         isrh->nexthdr = hdr->nexthdr;
 177         hdr->nexthdr = NEXTHDR_ROUTING;
 178
 179         isrh->segments[0] = hdr->daddr;
 180         hdr->daddr = isrh->segments[isrh->first_segment];
 181
 182 #ifdef CONFIG_IPV6_SEG6_HMAC
 183         if (sr_has_hmac(isrh)) {
 184                 struct net *net = dev_net(skb_dst(skb)->dev);
 185
 186                 err = seg6_push_hmac(net, &hdr->saddr, isrh);
 187                 if (unlikely(err))
 188                         return err;
 189         }
 190 #endif
 191
 192         skb_postpush_rcsum(skb, hdr, sizeof(struct ipv6hdr) + hdrlen);
 193
 194         return 0;
 195 }
 196 #endif
 197
 198 static int seg6_do_srh(struct sk_buff *skb)
 199 {
 200         struct dst_entry *dst = skb_dst(skb);
 201         struct seg6_iptunnel_encap *tinfo;
 202         int err = 0;
 203
 204         tinfo = seg6_encap_lwtunnel(dst->lwtstate);
 205
 206         if (likely(!skb->encapsulation)) {
 207                 skb_reset_inner_headers(skb);
 208                 skb->encapsulation = 1;
 209         }
 210
 211         switch (tinfo->mode) {
 212 #ifdef CONFIG_IPV6_SEG6_INLINE
 213         case SEG6_IPTUN_MODE_INLINE:
 214                 err = seg6_do_srh_inline(skb, tinfo->srh);
 215                 skb_reset_inner_headers(skb);
 216                 break;
 217 #endif
 218         case SEG6_IPTUN_MODE_ENCAP:
 219                 err = seg6_do_srh_encap(skb, tinfo->srh);
 220                 break;
 221         }
 222
 223         if (err)
 224                 return err;
 225
 226         ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 227         skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 228
 229         skb_set_inner_protocol(skb, skb->protocol);
 230
 231         return 0;
 232 }
 233
 234 static int seg6_input(struct sk_buff *skb)
 235 {
 236         struct dst_entry *orig_dst = skb_dst(skb);
 237         struct dst_entry *dst = NULL;
 238         struct seg6_lwt *slwt;
 239         int err;
 240
 241         err = seg6_do_srh(skb);
 242         if (unlikely(err)) {
 243                 kfree_skb(skb);
 244                 return err;
 245         }
 246
 247         slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
 248
 249         preempt_disable();
 250         dst = dst_cache_get(&slwt->cache);
 251         preempt_enable();
 252
 253         skb_dst_drop(skb);
 254
 255         if (!dst) {
 256                 ip6_route_input(skb);
 257                 dst = skb_dst(skb);
 258                 if (!dst->error) {
 259                         preempt_disable();
 260                         dst_cache_set_ip6(&slwt->cache, dst,
 261                                           &ipv6_hdr(skb)->saddr);
 262                         preempt_enable();
 263                 }
 264         } else {
 265                 skb_dst_set(skb, dst);
 266         }
 267
 268         err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 269         if (unlikely(err))
 270                 return err;
 271
 272         return dst_input(skb);
 273 }
 274
 275 static int seg6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 276 {
 277         struct dst_entry *orig_dst = skb_dst(skb);
 278         struct dst_entry *dst = NULL;
 279         struct seg6_lwt *slwt;
 280         int err = -EINVAL;
 281
 282         err = seg6_do_srh(skb);
 283         if (unlikely(err))
 284                 goto drop;
 285
 286         slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
 287
 288         preempt_disable();
 289         dst = dst_cache_get(&slwt->cache);
 290         preempt_enable();
 291
 292         if (unlikely(!dst)) {
 293                 struct ipv6hdr *hdr = ipv6_hdr(skb);
 294                 struct flowi6 fl6;
 295
 296                 fl6.daddr = hdr->daddr;
 297                 fl6.saddr = hdr->saddr;
 298                 fl6.flowlabel = ip6_flowinfo(hdr);
 299                 fl6.flowi6_mark = skb->mark;
 300                 fl6.flowi6_proto = hdr->nexthdr;
 301
 302                 dst = ip6_route_output(net, NULL, &fl6);
 303                 if (dst->error) {
 304                         err = dst->error;
 305                         dst_release(dst);
 306                         goto drop;
 307                 }
 308
 309                 preempt_disable();
 310                 dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
 311                 preempt_enable();
 312         }
 313
 314         skb_dst_drop(skb);
 315         skb_dst_set(skb, dst);
 316
 317         err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 318         if (unlikely(err))
 319                 goto drop;
 320
 321         return dst_output(net, sk, skb);
 322 drop:
 323         kfree_skb(skb);
 324         return err;
 325 }
 326
 327 static int seg6_build_state(struct nlattr *nla,
 328                             unsigned int family, const void *cfg,
 329                             struct lwtunnel_state **ts,
 330                             struct netlink_ext_ack *extack)
 331 {
 332         struct nlattr *tb[SEG6_IPTUNNEL_MAX + 1];
 333         struct seg6_iptunnel_encap *tuninfo;
 334         struct lwtunnel_state *newts;
 335         int tuninfo_len, min_size;
 336         struct seg6_lwt *slwt;
 337         int err;
 338
 339         err = nla_parse_nested(tb, SEG6_IPTUNNEL_MAX, nla,
 340                                seg6_iptunnel_policy, extack);
 341
 342         if (err < 0)
 343                 return err;
 344
 345         if (!tb[SEG6_IPTUNNEL_SRH])
 346                 return -EINVAL;
 347
 348         tuninfo = nla_data(tb[SEG6_IPTUNNEL_SRH]);
 349         tuninfo_len = nla_len(tb[SEG6_IPTUNNEL_SRH]);
 350
 351         /* tuninfo must contain at least the iptunnel encap structure,
 352          * the SRH and one segment
 353          */
 354         min_size = sizeof(*tuninfo) + sizeof(struct ipv6_sr_hdr) +
 355                    sizeof(struct in6_addr);
 356         if (tuninfo_len < min_size)
 357                 return -EINVAL;
 358
 359         switch (tuninfo->mode) {
 360 #ifdef CONFIG_IPV6_SEG6_INLINE
 361         case SEG6_IPTUN_MODE_INLINE:
 362                 break;
 363 #endif
 364         case SEG6_IPTUN_MODE_ENCAP:
 365                 break;
 366         default:
 367                 return -EINVAL;
 368         }
 369
 370         /* verify that SRH is consistent */
 371         if (!seg6_validate_srh(tuninfo->srh, tuninfo_len - sizeof(*tuninfo)))
 372                 return -EINVAL;
 373
 374         newts = lwtunnel_state_alloc(tuninfo_len + sizeof(*slwt));
 375         if (!newts)
 376                 return -ENOMEM;
 377
 378         slwt = seg6_lwt_lwtunnel(newts);
 379
 380         err = dst_cache_init(&slwt->cache, GFP_KERNEL);
 381         if (err) {
 382                 kfree(newts);
 383                 return err;
 384         }
 385
 386         memcpy(&slwt->tuninfo, tuninfo, tuninfo_len);
 387
 388         newts->type = LWTUNNEL_ENCAP_SEG6;
 389         newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT |
 390                         LWTUNNEL_STATE_INPUT_REDIRECT;
 391         newts->headroom = seg6_lwt_headroom(tuninfo);
 392
 393         *ts = newts;
 394
 395         return 0;
 396 }
 397
 398 static void seg6_destroy_state(struct lwtunnel_state *lwt)
 399 {
 400         dst_cache_destroy(&seg6_lwt_lwtunnel(lwt)->cache);
 401 }
 402
 403 static int seg6_fill_encap_info(struct sk_buff *skb,
 404                                 struct lwtunnel_state *lwtstate)
 405 {
 406         struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);
 407
 408         if (nla_put_srh(skb, SEG6_IPTUNNEL_SRH, tuninfo))
 409                 return -EMSGSIZE;
 410
 411         return 0;
 412 }
 413
 414 static int seg6_encap_nlsize(struct lwtunnel_state *lwtstate)
 415 {
 416         struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);
 417
 418         return nla_total_size(SEG6_IPTUN_ENCAP_SIZE(tuninfo));
 419 }
 420
 421 static int seg6_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 422 {
 423         struct seg6_iptunnel_encap *a_hdr = seg6_encap_lwtunnel(a);
 424         struct seg6_iptunnel_encap *b_hdr = seg6_encap_lwtunnel(b);
 425         int len = SEG6_IPTUN_ENCAP_SIZE(a_hdr);
 426
 427         if (len != SEG6_IPTUN_ENCAP_SIZE(b_hdr))
 428                 return 1;
 429
 430         return memcmp(a_hdr, b_hdr, len);
 431 }
 432
 433 static const struct lwtunnel_encap_ops seg6_iptun_ops = {
 434         .build_state = seg6_build_state,
 435         .destroy_state = seg6_destroy_state,
 436         .output = seg6_output,
 437         .input = seg6_input,
 438         .fill_encap = seg6_fill_encap_info,
 439         .get_encap_size = seg6_encap_nlsize,
 440         .cmp_encap = seg6_encap_cmp,
 441         .owner = THIS_MODULE,
 442 };
 443
 444 int __init seg6_iptunnel_init(void)
 445 {
 446         return lwtunnel_encap_add_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
 447 }
 448
 449 void seg6_iptunnel_exit(void)
 450 {
 451         lwtunnel_encap_del_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
 452 }