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 /* 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 + skb->mac_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 + skb->mac_len);
 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 }