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