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                 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 }