net/core/lwt_bpf.c

   1 /* Copyright (c) 2016 Thomas Graf <tgraf@tgraf.ch>
   2  *
   3  * This program is free software; you can redistribute it and/or
   4  * modify it under the terms of version 2 of the GNU General Public
   5  * License as published by the Free Software Foundation.
   6  *
   7  * This program is distributed in the hope that it will be useful, but
   8  * WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  10  * General Public License for more details.
  11  */
  12
  13 #include <linux/kernel.h>
  14 #include <linux/module.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/types.h>
  17 #include <linux/bpf.h>
  18 #include <net/lwtunnel.h>
  19 #include <net/gre.h>
  20 #include <net/ip6_route.h>
  21 #include <net/ipv6_stubs.h>
  22
  23 struct bpf_lwt_prog {
  24         struct bpf_prog *prog;
  25         char *name;
  26 };
  27
  28 struct bpf_lwt {
  29         struct bpf_lwt_prog in;
  30         struct bpf_lwt_prog out;
  31         struct bpf_lwt_prog xmit;
  32         int family;
  33 };
  34
  35 #define MAX_PROG_NAME 256
  36
  37 static inline struct bpf_lwt *bpf_lwt_lwtunnel(struct lwtunnel_state *lwt)
  38 {
  39         return (struct bpf_lwt *)lwt->data;
  40 }
  41
  42 #define NO_REDIRECT false
  43 #define CAN_REDIRECT true
  44
  45 static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt,
  46                        struct dst_entry *dst, bool can_redirect)
  47 {
  48         int ret;
  49
  50         /* Preempt disable is needed to protect per-cpu redirect_info between
  51          * BPF prog and skb_do_redirect(). The call_rcu in bpf_prog_put() and
  52          * access to maps strictly require a rcu_read_lock() for protection,
  53          * mixing with BH RCU lock doesn't work.
  54          */
  55         preempt_disable();
  56         bpf_compute_data_pointers(skb);
  57         ret = bpf_prog_run_save_cb(lwt->prog, skb);
  58
  59         switch (ret) {
  60         case BPF_OK:
  61         case BPF_LWT_REROUTE:
  62                 break;
  63
  64         case BPF_REDIRECT:
  65                 if (unlikely(!can_redirect)) {
  66                         pr_warn_once("Illegal redirect return code in prog %s\n",
  67                                      lwt->name ? : "<unknown>");
  68                         ret = BPF_OK;
  69                 } else {
  70                         skb_reset_mac_header(skb);
  71                         ret = skb_do_redirect(skb);
  72                         if (ret == 0)
  73                                 ret = BPF_REDIRECT;
  74                 }
  75                 break;
  76
  77         case BPF_DROP:
  78                 kfree_skb(skb);
  79                 ret = -EPERM;
  80                 break;
  81
  82         default:
  83                 pr_warn_once("bpf-lwt: Illegal return value %u, expect packet loss\n", ret);
  84                 kfree_skb(skb);
  85                 ret = -EINVAL;
  86                 break;
  87         }
  88
  89         preempt_enable();
  90
  91         return ret;
  92 }
  93
  94 static int bpf_lwt_input_reroute(struct sk_buff *skb)
  95 {
  96         int err = -EINVAL;
  97
  98         if (skb->protocol == htons(ETH_P_IP)) {
  99                 struct iphdr *iph = ip_hdr(skb);
 100
 101                 err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
 102                                            iph->tos, skb_dst(skb)->dev);
 103         } else if (skb->protocol == htons(ETH_P_IPV6)) {
 104                 err = ipv6_stub->ipv6_route_input(skb);
 105         } else {
 106                 err = -EAFNOSUPPORT;
 107         }
 108
 109         if (err)
 110                 goto err;
 111         return dst_input(skb);
 112
 113 err:
 114         kfree_skb(skb);
 115         return err;
 116 }
 117
 118 static int bpf_input(struct sk_buff *skb)
 119 {
 120         struct dst_entry *dst = skb_dst(skb);
 121         struct bpf_lwt *bpf;
 122         int ret;
 123
 124         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 125         if (bpf->in.prog) {
 126                 ret = run_lwt_bpf(skb, &bpf->in, dst, NO_REDIRECT);
 127                 if (ret < 0)
 128                         return ret;
 129                 if (ret == BPF_LWT_REROUTE)
 130                         return bpf_lwt_input_reroute(skb);
 131         }
 132
 133         if (unlikely(!dst->lwtstate->orig_input)) {
 134                 kfree_skb(skb);
 135                 return -EINVAL;
 136         }
 137
 138         return dst->lwtstate->orig_input(skb);
 139 }
 140
 141 static int bpf_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 142 {
 143         struct dst_entry *dst = skb_dst(skb);
 144         struct bpf_lwt *bpf;
 145         int ret;
 146
 147         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 148         if (bpf->out.prog) {
 149                 ret = run_lwt_bpf(skb, &bpf->out, dst, NO_REDIRECT);
 150                 if (ret < 0)
 151                         return ret;
 152         }
 153
 154         if (unlikely(!dst->lwtstate->orig_output)) {
 155                 pr_warn_once("orig_output not set on dst for prog %s\n",
 156                              bpf->out.name);
 157                 kfree_skb(skb);
 158                 return -EINVAL;
 159         }
 160
 161         return dst->lwtstate->orig_output(net, sk, skb);
 162 }
 163
 164 static int xmit_check_hhlen(struct sk_buff *skb)
 165 {
 166         int hh_len = skb_dst(skb)->dev->hard_header_len;
 167
 168         if (skb_headroom(skb) < hh_len) {
 169                 int nhead = HH_DATA_ALIGN(hh_len - skb_headroom(skb));
 170
 171                 if (pskb_expand_head(skb, nhead, 0, GFP_ATOMIC))
 172                         return -ENOMEM;
 173         }
 174
 175         return 0;
 176 }
 177
 178 static int bpf_lwt_xmit_reroute(struct sk_buff *skb)
 179 {
 180         struct net_device *l3mdev = l3mdev_master_dev_rcu(skb_dst(skb)->dev);
 181         int oif = l3mdev ? l3mdev->ifindex : 0;
 182         struct dst_entry *dst = NULL;
 183         int err = -EAFNOSUPPORT;
 184         struct sock *sk;
 185         struct net *net;
 186         bool ipv4;
 187
 188         if (skb->protocol == htons(ETH_P_IP))
 189                 ipv4 = true;
 190         else if (skb->protocol == htons(ETH_P_IPV6))
 191                 ipv4 = false;
 192         else
 193                 goto err;
 194
 195         sk = sk_to_full_sk(skb->sk);
 196         if (sk) {
 197                 if (sk->sk_bound_dev_if)
 198                         oif = sk->sk_bound_dev_if;
 199                 net = sock_net(sk);
 200         } else {
 201                 net = dev_net(skb_dst(skb)->dev);
 202         }
 203
 204         if (ipv4) {
 205                 struct iphdr *iph = ip_hdr(skb);
 206                 struct flowi4 fl4 = {};
 207                 struct rtable *rt;
 208
 209                 fl4.flowi4_oif = oif;
 210                 fl4.flowi4_mark = skb->mark;
 211                 fl4.flowi4_uid = sock_net_uid(net, sk);
 212                 fl4.flowi4_tos = RT_TOS(iph->tos);
 213                 fl4.flowi4_flags = FLOWI_FLAG_ANYSRC;
 214                 fl4.flowi4_proto = iph->protocol;
 215                 fl4.daddr = iph->daddr;
 216                 fl4.saddr = iph->saddr;
 217
 218                 rt = ip_route_output_key(net, &fl4);
 219                 if (IS_ERR(rt)) {
 220                         err = PTR_ERR(rt);
 221                         goto err;
 222                 }
 223                 dst = &rt->dst;
 224         } else {
 225                 struct ipv6hdr *iph6 = ipv6_hdr(skb);
 226                 struct flowi6 fl6 = {};
 227
 228                 fl6.flowi6_oif = oif;
 229                 fl6.flowi6_mark = skb->mark;
 230                 fl6.flowi6_uid = sock_net_uid(net, sk);
 231                 fl6.flowlabel = ip6_flowinfo(iph6);
 232                 fl6.flowi6_proto = iph6->nexthdr;
 233                 fl6.daddr = iph6->daddr;
 234                 fl6.saddr = iph6->saddr;
 235
 236                 err = ipv6_stub->ipv6_dst_lookup(net, skb->sk, &dst, &fl6);
 237                 if (unlikely(err))
 238                         goto err;
 239                 if (IS_ERR(dst)) {
 240                         err = PTR_ERR(dst);
 241                         goto err;
 242                 }
 243         }
 244         if (unlikely(dst->error)) {
 245                 err = dst->error;
 246                 dst_release(dst);
 247                 goto err;
 248         }
 249
 250         /* Although skb header was reserved in bpf_lwt_push_ip_encap(), it
 251          * was done for the previous dst, so we are doing it here again, in
 252          * case the new dst needs much more space. The call below is a noop
 253          * if there is enough header space in skb.
 254          */
 255         err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 256         if (unlikely(err))
 257                 goto err;
 258
 259         skb_dst_drop(skb);
 260         skb_dst_set(skb, dst);
 261
 262         err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb);
 263         if (unlikely(err))
 264                 return err;
 265
 266         /* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */
 267         return LWTUNNEL_XMIT_DONE;
 268
 269 err:
 270         kfree_skb(skb);
 271         return err;
 272 }
 273
 274 static int bpf_xmit(struct sk_buff *skb)
 275 {
 276         struct dst_entry *dst = skb_dst(skb);
 277         struct bpf_lwt *bpf;
 278
 279         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 280         if (bpf->xmit.prog) {
 281                 __be16 proto = skb->protocol;
 282                 int ret;
 283
 284                 ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT);
 285                 switch (ret) {
 286                 case BPF_OK:
 287                         /* If the header changed, e.g. via bpf_lwt_push_encap,
 288                          * BPF_LWT_REROUTE below should have been used if the
 289                          * protocol was also changed.
 290                          */
 291                         if (skb->protocol != proto) {
 292                                 kfree_skb(skb);
 293                                 return -EINVAL;
 294                         }
 295                         /* If the header was expanded, headroom might be too
 296                          * small for L2 header to come, expand as needed.
 297                          */
 298                         ret = xmit_check_hhlen(skb);
 299                         if (unlikely(ret))
 300                                 return ret;
 301
 302                         return LWTUNNEL_XMIT_CONTINUE;
 303                 case BPF_REDIRECT:
 304                         return LWTUNNEL_XMIT_DONE;
 305                 case BPF_LWT_REROUTE:
 306                         return bpf_lwt_xmit_reroute(skb);
 307                 default:
 308                         return ret;
 309                 }
 310         }
 311
 312         return LWTUNNEL_XMIT_CONTINUE;
 313 }
 314
 315 static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog)
 316 {
 317         if (prog->prog)
 318                 bpf_prog_put(prog->prog);
 319
 320         kfree(prog->name);
 321 }
 322
 323 static void bpf_destroy_state(struct lwtunnel_state *lwt)
 324 {
 325         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 326
 327         bpf_lwt_prog_destroy(&bpf->in);
 328         bpf_lwt_prog_destroy(&bpf->out);
 329         bpf_lwt_prog_destroy(&bpf->xmit);
 330 }
 331
 332 static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = {
 333         [LWT_BPF_PROG_FD]   = { .type = NLA_U32, },
 334         [LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
 335                                 .len = MAX_PROG_NAME },
 336 };
 337
 338 static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog,
 339                           enum bpf_prog_type type)
 340 {
 341         struct nlattr *tb[LWT_BPF_PROG_MAX + 1];
 342         struct bpf_prog *p;
 343         int ret;
 344         u32 fd;
 345
 346         ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr,
 347                                           bpf_prog_policy, NULL);
 348         if (ret < 0)
 349                 return ret;
 350
 351         if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME])
 352                 return -EINVAL;
 353
 354         prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC);
 355         if (!prog->name)
 356                 return -ENOMEM;
 357
 358         fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
 359         p = bpf_prog_get_type(fd, type);
 360         if (IS_ERR(p))
 361                 return PTR_ERR(p);
 362
 363         prog->prog = p;
 364
 365         return 0;
 366 }
 367
 368 static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = {
 369         [LWT_BPF_IN]            = { .type = NLA_NESTED, },
 370         [LWT_BPF_OUT]           = { .type = NLA_NESTED, },
 371         [LWT_BPF_XMIT]          = { .type = NLA_NESTED, },
 372         [LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 },
 373 };
 374
 375 static int bpf_build_state(struct nlattr *nla,
 376                            unsigned int family, const void *cfg,
 377                            struct lwtunnel_state **ts,
 378                            struct netlink_ext_ack *extack)
 379 {
 380         struct nlattr *tb[LWT_BPF_MAX + 1];
 381         struct lwtunnel_state *newts;
 382         struct bpf_lwt *bpf;
 383         int ret;
 384
 385         if (family != AF_INET && family != AF_INET6)
 386                 return -EAFNOSUPPORT;
 387
 388         ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy,
 389                                           extack);
 390         if (ret < 0)
 391                 return ret;
 392
 393         if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT])
 394                 return -EINVAL;
 395
 396         newts = lwtunnel_state_alloc(sizeof(*bpf));
 397         if (!newts)
 398                 return -ENOMEM;
 399
 400         newts->type = LWTUNNEL_ENCAP_BPF;
 401         bpf = bpf_lwt_lwtunnel(newts);
 402
 403         if (tb[LWT_BPF_IN]) {
 404                 newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
 405                 ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in,
 406                                      BPF_PROG_TYPE_LWT_IN);
 407                 if (ret  < 0)
 408                         goto errout;
 409         }
 410
 411         if (tb[LWT_BPF_OUT]) {
 412                 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
 413                 ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out,
 414                                      BPF_PROG_TYPE_LWT_OUT);
 415                 if (ret < 0)
 416                         goto errout;
 417         }
 418
 419         if (tb[LWT_BPF_XMIT]) {
 420                 newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
 421                 ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit,
 422                                      BPF_PROG_TYPE_LWT_XMIT);
 423                 if (ret < 0)
 424                         goto errout;
 425         }
 426
 427         if (tb[LWT_BPF_XMIT_HEADROOM]) {
 428                 u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]);
 429
 430                 if (headroom > LWT_BPF_MAX_HEADROOM) {
 431                         ret = -ERANGE;
 432                         goto errout;
 433                 }
 434
 435                 newts->headroom = headroom;
 436         }
 437
 438         bpf->family = family;
 439         *ts = newts;
 440
 441         return 0;
 442
 443 errout:
 444         bpf_destroy_state(newts);
 445         kfree(newts);
 446         return ret;
 447 }
 448
 449 static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr,
 450                              struct bpf_lwt_prog *prog)
 451 {
 452         struct nlattr *nest;
 453
 454         if (!prog->prog)
 455                 return 0;
 456
 457         nest = nla_nest_start_noflag(skb, attr);
 458         if (!nest)
 459                 return -EMSGSIZE;
 460
 461         if (prog->name &&
 462             nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name))
 463                 return -EMSGSIZE;
 464
 465         return nla_nest_end(skb, nest);
 466 }
 467
 468 static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt)
 469 {
 470         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 471
 472         if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 ||
 473             bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 ||
 474             bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0)
 475                 return -EMSGSIZE;
 476
 477         return 0;
 478 }
 479
 480 static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate)
 481 {
 482         int nest_len = nla_total_size(sizeof(struct nlattr)) +
 483                        nla_total_size(MAX_PROG_NAME) + /* LWT_BPF_PROG_NAME */
 484                        0;
 485
 486         return nest_len + /* LWT_BPF_IN */
 487                nest_len + /* LWT_BPF_OUT */
 488                nest_len + /* LWT_BPF_XMIT */
 489                0;
 490 }
 491
 492 static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b)
 493 {
 494         /* FIXME:
 495          * The LWT state is currently rebuilt for delete requests which
 496          * results in a new bpf_prog instance. Comparing names for now.
 497          */
 498         if (!a->name && !b->name)
 499                 return 0;
 500
 501         if (!a->name || !b->name)
 502                 return 1;
 503
 504         return strcmp(a->name, b->name);
 505 }
 506
 507 static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 508 {
 509         struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a);
 510         struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b);
 511
 512         return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) ||
 513                bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) ||
 514                bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit);
 515 }
 516
 517 static const struct lwtunnel_encap_ops bpf_encap_ops = {
 518         .build_state    = bpf_build_state,
 519         .destroy_state  = bpf_destroy_state,
 520         .input          = bpf_input,
 521         .output         = bpf_output,
 522         .xmit           = bpf_xmit,
 523         .fill_encap     = bpf_fill_encap_info,
 524         .get_encap_size = bpf_encap_nlsize,
 525         .cmp_encap      = bpf_encap_cmp,
 526         .owner          = THIS_MODULE,
 527 };
 528
 529 static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type,
 530                            int encap_len)
 531 {
 532         struct skb_shared_info *shinfo = skb_shinfo(skb);
 533
 534         gso_type |= SKB_GSO_DODGY;
 535         shinfo->gso_type |= gso_type;
 536         skb_decrease_gso_size(shinfo, encap_len);
 537         shinfo->gso_segs = 0;
 538         return 0;
 539 }
 540
 541 static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len)
 542 {
 543         int next_hdr_offset;
 544         void *next_hdr;
 545         __u8 protocol;
 546
 547         /* SCTP and UDP_L4 gso need more nuanced handling than what
 548          * handle_gso_type() does above: skb_decrease_gso_size() is not enough.
 549          * So at the moment only TCP GSO packets are let through.
 550          */
 551         if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
 552                 return -ENOTSUPP;
 553
 554         if (ipv4) {
 555                 protocol = ip_hdr(skb)->protocol;
 556                 next_hdr_offset = sizeof(struct iphdr);
 557                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 558         } else {
 559                 protocol = ipv6_hdr(skb)->nexthdr;
 560                 next_hdr_offset = sizeof(struct ipv6hdr);
 561                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 562         }
 563
 564         switch (protocol) {
 565         case IPPROTO_GRE:
 566                 next_hdr_offset += sizeof(struct gre_base_hdr);
 567                 if (next_hdr_offset > encap_len)
 568                         return -EINVAL;
 569
 570                 if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM)
 571                         return handle_gso_type(skb, SKB_GSO_GRE_CSUM,
 572                                                encap_len);
 573                 return handle_gso_type(skb, SKB_GSO_GRE, encap_len);
 574
 575         case IPPROTO_UDP:
 576                 next_hdr_offset += sizeof(struct udphdr);
 577                 if (next_hdr_offset > encap_len)
 578                         return -EINVAL;
 579
 580                 if (((struct udphdr *)next_hdr)->check)
 581                         return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM,
 582                                                encap_len);
 583                 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len);
 584
 585         case IPPROTO_IP:
 586         case IPPROTO_IPV6:
 587                 if (ipv4)
 588                         return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len);
 589                 else
 590                         return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len);
 591
 592         default:
 593                 return -EPROTONOSUPPORT;
 594         }
 595 }
 596
 597 int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress)
 598 {
 599         struct iphdr *iph;
 600         bool ipv4;
 601         int err;
 602
 603         if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM))
 604                 return -EINVAL;
 605
 606         /* validate protocol and length */
 607         iph = (struct iphdr *)hdr;
 608         if (iph->version == 4) {
 609                 ipv4 = true;
 610                 if (unlikely(len < iph->ihl * 4))
 611                         return -EINVAL;
 612         } else if (iph->version == 6) {
 613                 ipv4 = false;
 614                 if (unlikely(len < sizeof(struct ipv6hdr)))
 615                         return -EINVAL;
 616         } else {
 617                 return -EINVAL;
 618         }
 619
 620         if (ingress)
 621                 err = skb_cow_head(skb, len + skb->mac_len);
 622         else
 623                 err = skb_cow_head(skb,
 624                                    len + LL_RESERVED_SPACE(skb_dst(skb)->dev));
 625         if (unlikely(err))
 626                 return err;
 627
 628         /* push the encap headers and fix pointers */
 629         skb_reset_inner_headers(skb);
 630         skb_reset_inner_mac_header(skb);  /* mac header is not yet set */
 631         skb_set_inner_protocol(skb, skb->protocol);
 632         skb->encapsulation = 1;
 633         skb_push(skb, len);
 634         if (ingress)
 635                 skb_postpush_rcsum(skb, iph, len);
 636         skb_reset_network_header(skb);
 637         memcpy(skb_network_header(skb), hdr, len);
 638         bpf_compute_data_pointers(skb);
 639         skb_clear_hash(skb);
 640
 641         if (ipv4) {
 642                 skb->protocol = htons(ETH_P_IP);
 643                 iph = ip_hdr(skb);
 644
 645                 if (!iph->check)
 646                         iph->check = ip_fast_csum((unsigned char *)iph,
 647                                                   iph->ihl);
 648         } else {
 649                 skb->protocol = htons(ETH_P_IPV6);
 650         }
 651
 652         if (skb_is_gso(skb))
 653                 return handle_gso_encap(skb, ipv4, len);
 654
 655         return 0;
 656 }
 657
 658 static int __init bpf_lwt_init(void)
 659 {
 660         return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF);
 661 }
 662
 663 subsys_initcall(bpf_lwt_init)