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