net/ipv6/seg6_iptunnel.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *  SR-IPv6 implementation
   4  *
   5  *  Author:
   6  *  David Lebrun <david.lebrun@uclouvain.be>
   7  */
   8
   9 #include <linux/types.h>
  10 #include <linux/skbuff.h>
  11 #include <linux/net.h>
  12 #include <linux/module.h>
  13 #include <net/ip.h>
  14 #include <net/ip_tunnels.h>
  15 #include <net/lwtunnel.h>
  16 #include <net/netevent.h>
  17 #include <net/netns/generic.h>
  18 #include <net/ip6_fib.h>
  19 #include <net/route.h>
  20 #include <net/seg6.h>
  21 #include <linux/seg6.h>
  22 #include <linux/seg6_iptunnel.h>
  23 #include <net/addrconf.h>
  24 #include <net/ip6_route.h>
  25 #include <net/dst_cache.h>
  26 #ifdef CONFIG_IPV6_SEG6_HMAC
  27 #include <net/seg6_hmac.h>
  28 #endif
  29
  30 static size_t seg6_lwt_headroom(struct seg6_iptunnel_encap *tuninfo)
  31 {
  32         int head = 0;
  33
  34         switch (tuninfo->mode) {
  35         case SEG6_IPTUN_MODE_INLINE:
  36                 break;
  37         case SEG6_IPTUN_MODE_ENCAP:
  38                 head = sizeof(struct ipv6hdr);
  39                 break;
  40         case SEG6_IPTUN_MODE_L2ENCAP:
  41                 return 0;
  42         }
  43
  44         return ((tuninfo->srh->hdrlen + 1) << 3) + head;
  45 }
  46
  47 struct seg6_lwt {
  48         struct dst_cache cache;
  49         struct seg6_iptunnel_encap tuninfo[];
  50 };
  51
  52 static inline struct seg6_lwt *seg6_lwt_lwtunnel(struct lwtunnel_state *lwt)
  53 {
  54         return (struct seg6_lwt *)lwt->data;
  55 }
  56
  57 static inline struct seg6_iptunnel_encap *
  58 seg6_encap_lwtunnel(struct lwtunnel_state *lwt)
  59 {
  60         return seg6_lwt_lwtunnel(lwt)->tuninfo;
  61 }
  62
  63 static const struct nla_policy seg6_iptunnel_policy[SEG6_IPTUNNEL_MAX + 1] = {
  64         [SEG6_IPTUNNEL_SRH]     = { .type = NLA_BINARY },
  65 };
  66
  67 static int nla_put_srh(struct sk_buff *skb, int attrtype,
  68                        struct seg6_iptunnel_encap *tuninfo)
  69 {
  70         struct seg6_iptunnel_encap *data;
  71         struct nlattr *nla;
  72         int len;
  73
  74         len = SEG6_IPTUN_ENCAP_SIZE(tuninfo);
  75
  76         nla = nla_reserve(skb, attrtype, len);
  77         if (!nla)
  78                 return -EMSGSIZE;
  79
  80         data = nla_data(nla);
  81         memcpy(data, tuninfo, len);
  82
  83         return 0;
  84 }
  85
  86 static void set_tun_src(struct net *net, struct net_device *dev,
  87                         struct in6_addr *daddr, struct in6_addr *saddr)
  88 {
  89         struct seg6_pernet_data *sdata = seg6_pernet(net);
  90         struct in6_addr *tun_src;
  91
  92         rcu_read_lock();
  93
  94         tun_src = rcu_dereference(sdata->tun_src);
  95
  96         if (!ipv6_addr_any(tun_src)) {
  97                 memcpy(saddr, tun_src, sizeof(struct in6_addr));
  98         } else {
  99                 ipv6_dev_get_saddr(net, dev, daddr, IPV6_PREFER_SRC_PUBLIC,
 100                                    saddr);
 101         }
 102
 103         rcu_read_unlock();
 104 }
 105
 106 /* Compute flowlabel for outer IPv6 header */
 107 static __be32 seg6_make_flowlabel(struct net *net, struct sk_buff *skb,
 108                                   struct ipv6hdr *inner_hdr)
 109 {
 110         int do_flowlabel = net->ipv6.sysctl.seg6_flowlabel;
 111         __be32 flowlabel = 0;
 112         u32 hash;
 113
 114         if (do_flowlabel > 0) {
 115                 hash = skb_get_hash(skb);
 116                 hash = rol32(hash, 16);
 117                 flowlabel = (__force __be32)hash & IPV6_FLOWLABEL_MASK;
 118         } else if (!do_flowlabel && skb->protocol == htons(ETH_P_IPV6)) {
 119                 flowlabel = ip6_flowlabel(inner_hdr);
 120         }
 121         return flowlabel;
 122 }
 123
 124 /* encapsulate an IPv6 packet within an outer IPv6 header with a given SRH */
 125 int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh, int proto)
 126 {
 127         struct dst_entry *dst = skb_dst(skb);
 128         struct net *net = dev_net(dst->dev);
 129         struct ipv6hdr *hdr, *inner_hdr;
 130         struct ipv6_sr_hdr *isrh;
 131         int hdrlen, tot_len, err;
 132         __be32 flowlabel;
 133
 134         hdrlen = (osrh->hdrlen + 1) << 3;
 135         tot_len = hdrlen + sizeof(*hdr);
 136
 137         err = skb_cow_head(skb, tot_len + skb->mac_len);
 138         if (unlikely(err))
 139                 return err;
 140
 141         inner_hdr = ipv6_hdr(skb);
 142         flowlabel = seg6_make_flowlabel(net, skb, inner_hdr);
 143
 144         skb_push(skb, tot_len);
 145         skb_reset_network_header(skb);
 146         skb_mac_header_rebuild(skb);
 147         hdr = ipv6_hdr(skb);
 148
 149         /* inherit tc, flowlabel and hlim
 150          * hlim will be decremented in ip6_forward() afterwards and
 151          * decapsulation will overwrite inner hlim with outer hlim
 152          */
 153
 154         if (skb->protocol == htons(ETH_P_IPV6)) {
 155                 ip6_flow_hdr(hdr, ip6_tclass(ip6_flowinfo(inner_hdr)),
 156                              flowlabel);
 157                 hdr->hop_limit = inner_hdr->hop_limit;
 158         } else {
 159                 ip6_flow_hdr(hdr, 0, flowlabel);
 160                 hdr->hop_limit = ip6_dst_hoplimit(skb_dst(skb));
 161
 162                 memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
 163         }
 164
 165         hdr->nexthdr = NEXTHDR_ROUTING;
 166
 167         isrh = (void *)hdr + sizeof(*hdr);
 168         memcpy(isrh, osrh, hdrlen);
 169
 170         isrh->nexthdr = proto;
 171
 172         hdr->daddr = isrh->segments[isrh->first_segment];
 173         set_tun_src(net, dst->dev, &hdr->daddr, &hdr->saddr);
 174
 175 #ifdef CONFIG_IPV6_SEG6_HMAC
 176         if (sr_has_hmac(isrh)) {
 177                 err = seg6_push_hmac(net, &hdr->saddr, isrh);
 178                 if (unlikely(err))
 179                         return err;
 180         }
 181 #endif
 182
 183         skb_postpush_rcsum(skb, hdr, tot_len);
 184
 185         return 0;
 186 }
 187 EXPORT_SYMBOL_GPL(seg6_do_srh_encap);
 188
 189 /* insert an SRH within an IPv6 packet, just after the IPv6 header */
 190 int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh)
 191 {
 192         struct ipv6hdr *hdr, *oldhdr;
 193         struct ipv6_sr_hdr *isrh;
 194         int hdrlen, err;
 195
 196         hdrlen = (osrh->hdrlen + 1) << 3;
 197
 198         err = skb_cow_head(skb, hdrlen + skb->mac_len);
 199         if (unlikely(err))
 200                 return err;
 201
 202         oldhdr = ipv6_hdr(skb);
 203
 204         skb_pull(skb, sizeof(struct ipv6hdr));
 205         skb_postpull_rcsum(skb, skb_network_header(skb),
 206                            sizeof(struct ipv6hdr));
 207
 208         skb_push(skb, sizeof(struct ipv6hdr) + hdrlen);
 209         skb_reset_network_header(skb);
 210         skb_mac_header_rebuild(skb);
 211
 212         hdr = ipv6_hdr(skb);
 213
 214         memmove(hdr, oldhdr, sizeof(*hdr));
 215
 216         isrh = (void *)hdr + sizeof(*hdr);
 217         memcpy(isrh, osrh, hdrlen);
 218
 219         isrh->nexthdr = hdr->nexthdr;
 220         hdr->nexthdr = NEXTHDR_ROUTING;
 221
 222         isrh->segments[0] = hdr->daddr;
 223         hdr->daddr = isrh->segments[isrh->first_segment];
 224
 225 #ifdef CONFIG_IPV6_SEG6_HMAC
 226         if (sr_has_hmac(isrh)) {
 227                 struct net *net = dev_net(skb_dst(skb)->dev);
 228
 229                 err = seg6_push_hmac(net, &hdr->saddr, isrh);
 230                 if (unlikely(err))
 231                         return err;
 232         }
 233 #endif
 234
 235         skb_postpush_rcsum(skb, hdr, sizeof(struct ipv6hdr) + hdrlen);
 236
 237         return 0;
 238 }
 239 EXPORT_SYMBOL_GPL(seg6_do_srh_inline);
 240
 241 static int seg6_do_srh(struct sk_buff *skb)
 242 {
 243         struct dst_entry *dst = skb_dst(skb);
 244         struct seg6_iptunnel_encap *tinfo;
 245         int proto, err = 0;
 246
 247         tinfo = seg6_encap_lwtunnel(dst->lwtstate);
 248
 249         switch (tinfo->mode) {
 250         case SEG6_IPTUN_MODE_INLINE:
 251                 if (skb->protocol != htons(ETH_P_IPV6))
 252                         return -EINVAL;
 253
 254                 err = seg6_do_srh_inline(skb, tinfo->srh);
 255                 if (err)
 256                         return err;
 257                 break;
 258         case SEG6_IPTUN_MODE_ENCAP:
 259                 err = iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6);
 260                 if (err)
 261                         return err;
 262
 263                 if (skb->protocol == htons(ETH_P_IPV6))
 264                         proto = IPPROTO_IPV6;
 265                 else if (skb->protocol == htons(ETH_P_IP))
 266                         proto = IPPROTO_IPIP;
 267                 else
 268                         return -EINVAL;
 269
 270                 err = seg6_do_srh_encap(skb, tinfo->srh, proto);
 271                 if (err)
 272                         return err;
 273
 274                 skb_set_inner_transport_header(skb, skb_transport_offset(skb));
 275                 skb_set_inner_protocol(skb, skb->protocol);
 276                 skb->protocol = htons(ETH_P_IPV6);
 277                 break;
 278         case SEG6_IPTUN_MODE_L2ENCAP:
 279                 if (!skb_mac_header_was_set(skb))
 280                         return -EINVAL;
 281
 282                 if (pskb_expand_head(skb, skb->mac_len, 0, GFP_ATOMIC) < 0)
 283                         return -ENOMEM;
 284
 285                 skb_mac_header_rebuild(skb);
 286                 skb_push(skb, skb->mac_len);
 287
 288                 err = seg6_do_srh_encap(skb, tinfo->srh, IPPROTO_ETHERNET);
 289                 if (err)
 290                         return err;
 291
 292                 skb->protocol = htons(ETH_P_IPV6);
 293                 break;
 294         }
 295
 296         ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 297         skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 298
 299         return 0;
 300 }
 301
 302 static int seg6_input(struct sk_buff *skb)
 303 {
 304         struct dst_entry *orig_dst = skb_dst(skb);
 305         struct dst_entry *dst = NULL;
 306         struct seg6_lwt *slwt;
 307         int err;
 308
 309         err = seg6_do_srh(skb);
 310         if (unlikely(err)) {
 311                 kfree_skb(skb);
 312                 return err;
 313         }
 314
 315         slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
 316
 317         preempt_disable();
 318         dst = dst_cache_get(&slwt->cache);
 319         preempt_enable();
 320
 321         skb_dst_drop(skb);
 322
 323         if (!dst) {
 324                 ip6_route_input(skb);
 325                 dst = skb_dst(skb);
 326                 if (!dst->error) {
 327                         preempt_disable();
 328                         dst_cache_set_ip6(&slwt->cache, dst,
 329                                           &ipv6_hdr(skb)->saddr);
 330                         preempt_enable();
 331                 }
 332         } else {
 333                 skb_dst_set(skb, dst);
 334         }
 335
 336         err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 337         if (unlikely(err))
 338                 return err;
 339
 340         return dst_input(skb);
 341 }
 342
 343 static int seg6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 344 {
 345         struct dst_entry *orig_dst = skb_dst(skb);
 346         struct dst_entry *dst = NULL;
 347         struct seg6_lwt *slwt;
 348         int err = -EINVAL;
 349
 350         err = seg6_do_srh(skb);
 351         if (unlikely(err))
 352                 goto drop;
 353
 354         slwt = seg6_lwt_lwtunnel(orig_dst->lwtstate);
 355
 356         preempt_disable();
 357         dst = dst_cache_get(&slwt->cache);
 358         preempt_enable();
 359
 360         if (unlikely(!dst)) {
 361                 struct ipv6hdr *hdr = ipv6_hdr(skb);
 362                 struct flowi6 fl6;
 363
 364                 memset(&fl6, 0, sizeof(fl6));
 365                 fl6.daddr = hdr->daddr;
 366                 fl6.saddr = hdr->saddr;
 367                 fl6.flowlabel = ip6_flowinfo(hdr);
 368                 fl6.flowi6_mark = skb->mark;
 369                 fl6.flowi6_proto = hdr->nexthdr;
 370
 371                 dst = ip6_route_output(net, NULL, &fl6);
 372                 if (dst->error) {
 373                         err = dst->error;
 374                         dst_release(dst);
 375                         goto drop;
 376                 }
 377
 378                 preempt_disable();
 379                 dst_cache_set_ip6(&slwt->cache, dst, &fl6.saddr);
 380                 preempt_enable();
 381         }
 382
 383         skb_dst_drop(skb);
 384         skb_dst_set(skb, dst);
 385
 386         err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 387         if (unlikely(err))
 388                 goto drop;
 389
 390         return dst_output(net, sk, skb);
 391 drop:
 392         kfree_skb(skb);
 393         return err;
 394 }
 395
 396 static int seg6_build_state(struct net *net, struct nlattr *nla,
 397                             unsigned int family, const void *cfg,
 398                             struct lwtunnel_state **ts,
 399                             struct netlink_ext_ack *extack)
 400 {
 401         struct nlattr *tb[SEG6_IPTUNNEL_MAX + 1];
 402         struct seg6_iptunnel_encap *tuninfo;
 403         struct lwtunnel_state *newts;
 404         int tuninfo_len, min_size;
 405         struct seg6_lwt *slwt;
 406         int err;
 407
 408         if (family != AF_INET && family != AF_INET6)
 409                 return -EINVAL;
 410
 411         err = nla_parse_nested_deprecated(tb, SEG6_IPTUNNEL_MAX, nla,
 412                                           seg6_iptunnel_policy, extack);
 413
 414         if (err < 0)
 415                 return err;
 416
 417         if (!tb[SEG6_IPTUNNEL_SRH])
 418                 return -EINVAL;
 419
 420         tuninfo = nla_data(tb[SEG6_IPTUNNEL_SRH]);
 421         tuninfo_len = nla_len(tb[SEG6_IPTUNNEL_SRH]);
 422
 423         /* tuninfo must contain at least the iptunnel encap structure,
 424          * the SRH and one segment
 425          */
 426         min_size = sizeof(*tuninfo) + sizeof(struct ipv6_sr_hdr) +
 427                    sizeof(struct in6_addr);
 428         if (tuninfo_len < min_size)
 429                 return -EINVAL;
 430
 431         switch (tuninfo->mode) {
 432         case SEG6_IPTUN_MODE_INLINE:
 433                 if (family != AF_INET6)
 434                         return -EINVAL;
 435
 436                 break;
 437         case SEG6_IPTUN_MODE_ENCAP:
 438                 break;
 439         case SEG6_IPTUN_MODE_L2ENCAP:
 440                 break;
 441         default:
 442                 return -EINVAL;
 443         }
 444
 445         /* verify that SRH is consistent */
 446         if (!seg6_validate_srh(tuninfo->srh, tuninfo_len - sizeof(*tuninfo), false))
 447                 return -EINVAL;
 448
 449         newts = lwtunnel_state_alloc(tuninfo_len + sizeof(*slwt));
 450         if (!newts)
 451                 return -ENOMEM;
 452
 453         slwt = seg6_lwt_lwtunnel(newts);
 454
 455         err = dst_cache_init(&slwt->cache, GFP_ATOMIC);
 456         if (err) {
 457                 kfree(newts);
 458                 return err;
 459         }
 460
 461         memcpy(&slwt->tuninfo, tuninfo, tuninfo_len);
 462
 463         newts->type = LWTUNNEL_ENCAP_SEG6;
 464         newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
 465
 466         if (tuninfo->mode != SEG6_IPTUN_MODE_L2ENCAP)
 467                 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
 468
 469         newts->headroom = seg6_lwt_headroom(tuninfo);
 470
 471         *ts = newts;
 472
 473         return 0;
 474 }
 475
 476 static void seg6_destroy_state(struct lwtunnel_state *lwt)
 477 {
 478         dst_cache_destroy(&seg6_lwt_lwtunnel(lwt)->cache);
 479 }
 480
 481 static int seg6_fill_encap_info(struct sk_buff *skb,
 482                                 struct lwtunnel_state *lwtstate)
 483 {
 484         struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);
 485
 486         if (nla_put_srh(skb, SEG6_IPTUNNEL_SRH, tuninfo))
 487                 return -EMSGSIZE;
 488
 489         return 0;
 490 }
 491
 492 static int seg6_encap_nlsize(struct lwtunnel_state *lwtstate)
 493 {
 494         struct seg6_iptunnel_encap *tuninfo = seg6_encap_lwtunnel(lwtstate);
 495
 496         return nla_total_size(SEG6_IPTUN_ENCAP_SIZE(tuninfo));
 497 }
 498
 499 static int seg6_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 500 {
 501         struct seg6_iptunnel_encap *a_hdr = seg6_encap_lwtunnel(a);
 502         struct seg6_iptunnel_encap *b_hdr = seg6_encap_lwtunnel(b);
 503         int len = SEG6_IPTUN_ENCAP_SIZE(a_hdr);
 504
 505         if (len != SEG6_IPTUN_ENCAP_SIZE(b_hdr))
 506                 return 1;
 507
 508         return memcmp(a_hdr, b_hdr, len);
 509 }
 510
 511 static const struct lwtunnel_encap_ops seg6_iptun_ops = {
 512         .build_state = seg6_build_state,
 513         .destroy_state = seg6_destroy_state,
 514         .output = seg6_output,
 515         .input = seg6_input,
 516         .fill_encap = seg6_fill_encap_info,
 517         .get_encap_size = seg6_encap_nlsize,
 518         .cmp_encap = seg6_encap_cmp,
 519         .owner = THIS_MODULE,
 520 };
 521
 522 int __init seg6_iptunnel_init(void)
 523 {
 524         return lwtunnel_encap_add_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
 525 }
 526
 527 void seg6_iptunnel_exit(void)
 528 {
 529         lwtunnel_encap_del_ops(&seg6_iptun_ops, LWTUNNEL_ENCAP_SEG6);
 530 }