net/core/lwt_bpf.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Copyright (c) 2016 Thomas Graf <[email protected]>
   3  */
   4
   5 #include <linux/filter.h>
   6 #include <linux/kernel.h>
   7 #include <linux/module.h>
   8 #include <linux/skbuff.h>
   9 #include <linux/types.h>
  10 #include <linux/bpf.h>
  11 #include <net/lwtunnel.h>
  12 #include <net/gre.h>
  13 #include <net/ip.h>
  14 #include <net/ip6_route.h>
  15 #include <net/ipv6_stubs.h>
  16 #include <net/inet_dscp.h>
  17
  18 struct bpf_lwt_prog {
  19         struct bpf_prog *prog;
  20         char *name;
  21 };
  22
  23 struct bpf_lwt {
  24         struct bpf_lwt_prog in;
  25         struct bpf_lwt_prog out;
  26         struct bpf_lwt_prog xmit;
  27         int family;
  28 };
  29
  30 #define MAX_PROG_NAME 256
  31
  32 static inline struct bpf_lwt *bpf_lwt_lwtunnel(struct lwtunnel_state *lwt)
  33 {
  34         return (struct bpf_lwt *)lwt->data;
  35 }
  36
  37 #define NO_REDIRECT false
  38 #define CAN_REDIRECT true
  39
  40 static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt,
  41                        struct dst_entry *dst, bool can_redirect)
  42 {
  43         struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
  44         int ret;
  45
  46         /* Disabling BH is needed to protect per-CPU bpf_redirect_info between
  47          * BPF prog and skb_do_redirect().
  48          */
  49         local_bh_disable();
  50         bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
  51         bpf_compute_data_pointers(skb);
  52         ret = bpf_prog_run_save_cb(lwt->prog, skb);
  53
  54         switch (ret) {
  55         case BPF_OK:
  56         case BPF_LWT_REROUTE:
  57                 break;
  58
  59         case BPF_REDIRECT:
  60                 if (unlikely(!can_redirect)) {
  61                         pr_warn_once("Illegal redirect return code in prog %s\n",
  62                                      lwt->name ? : "<unknown>");
  63                         ret = BPF_OK;
  64                 } else {
  65                         skb_reset_mac_header(skb);
  66                         skb_do_redirect(skb);
  67                         ret = BPF_REDIRECT;
  68                 }
  69                 break;
  70
  71         case BPF_DROP:
  72                 kfree_skb(skb);
  73                 ret = -EPERM;
  74                 break;
  75
  76         default:
  77                 pr_warn_once("bpf-lwt: Illegal return value %u, expect packet loss\n", ret);
  78                 kfree_skb(skb);
  79                 ret = -EINVAL;
  80                 break;
  81         }
  82
  83         bpf_net_ctx_clear(bpf_net_ctx);
  84         local_bh_enable();
  85
  86         return ret;
  87 }
  88
  89 static int bpf_lwt_input_reroute(struct sk_buff *skb)
  90 {
  91         enum skb_drop_reason reason;
  92         int err = -EINVAL;
  93
  94         if (skb->protocol == htons(ETH_P_IP)) {
  95                 struct net_device *dev = skb_dst(skb)->dev;
  96                 const struct iphdr *iph = ip_hdr(skb);
  97
  98                 dev_hold(dev);
  99                 skb_dst_drop(skb);
 100                 reason = ip_route_input_noref(skb, iph->daddr, iph->saddr,
 101                                               ip4h_dscp(iph), dev);
 102                 err = reason ? -EINVAL : 0;
 103                 dev_put(dev);
 104         } else if (skb->protocol == htons(ETH_P_IPV6)) {
 105                 skb_dst_drop(skb);
 106                 err = ipv6_stub->ipv6_route_input(skb);
 107         } else {
 108                 err = -EAFNOSUPPORT;
 109         }
 110
 111         if (err)
 112                 goto err;
 113         return dst_input(skb);
 114
 115 err:
 116         kfree_skb(skb);
 117         return err;
 118 }
 119
 120 static int bpf_input(struct sk_buff *skb)
 121 {
 122         struct dst_entry *dst = skb_dst(skb);
 123         struct bpf_lwt *bpf;
 124         int ret;
 125
 126         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 127         if (bpf->in.prog) {
 128                 ret = run_lwt_bpf(skb, &bpf->in, dst, NO_REDIRECT);
 129                 if (ret < 0)
 130                         return ret;
 131                 if (ret == BPF_LWT_REROUTE)
 132                         return bpf_lwt_input_reroute(skb);
 133         }
 134
 135         if (unlikely(!dst->lwtstate->orig_input)) {
 136                 kfree_skb(skb);
 137                 return -EINVAL;
 138         }
 139
 140         return dst->lwtstate->orig_input(skb);
 141 }
 142
 143 static int bpf_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 144 {
 145         struct dst_entry *dst = skb_dst(skb);
 146         struct bpf_lwt *bpf;
 147         int ret;
 148
 149         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 150         if (bpf->out.prog) {
 151                 ret = run_lwt_bpf(skb, &bpf->out, dst, NO_REDIRECT);
 152                 if (ret < 0)
 153                         return ret;
 154         }
 155
 156         if (unlikely(!dst->lwtstate->orig_output)) {
 157                 pr_warn_once("orig_output not set on dst for prog %s\n",
 158                              bpf->out.name);
 159                 kfree_skb(skb);
 160                 return -EINVAL;
 161         }
 162
 163         return dst->lwtstate->orig_output(net, sk, skb);
 164 }
 165
 166 static int xmit_check_hhlen(struct sk_buff *skb, int hh_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 = inet_dscp_to_dsfield(ip4h_dscp(iph));
 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                 dst = ipv6_stub->ipv6_dst_lookup_flow(net, skb->sk, &fl6, NULL);
 237                 if (IS_ERR(dst)) {
 238                         err = PTR_ERR(dst);
 239                         goto err;
 240                 }
 241         }
 242         if (unlikely(dst->error)) {
 243                 err = dst->error;
 244                 dst_release(dst);
 245                 goto err;
 246         }
 247
 248         /* Although skb header was reserved in bpf_lwt_push_ip_encap(), it
 249          * was done for the previous dst, so we are doing it here again, in
 250          * case the new dst needs much more space. The call below is a noop
 251          * if there is enough header space in skb.
 252          */
 253         err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 254         if (unlikely(err))
 255                 goto err;
 256
 257         skb_dst_drop(skb);
 258         skb_dst_set(skb, dst);
 259
 260         err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb);
 261         if (unlikely(err))
 262                 return net_xmit_errno(err);
 263
 264         /* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */
 265         return LWTUNNEL_XMIT_DONE;
 266
 267 err:
 268         kfree_skb(skb);
 269         return err;
 270 }
 271
 272 static int bpf_xmit(struct sk_buff *skb)
 273 {
 274         struct dst_entry *dst = skb_dst(skb);
 275         struct bpf_lwt *bpf;
 276
 277         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 278         if (bpf->xmit.prog) {
 279                 int hh_len = dst->dev->hard_header_len;
 280                 __be16 proto = skb->protocol;
 281                 int ret;
 282
 283                 ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT);
 284                 switch (ret) {
 285                 case BPF_OK:
 286                         /* If the header changed, e.g. via bpf_lwt_push_encap,
 287                          * BPF_LWT_REROUTE below should have been used if the
 288                          * protocol was also changed.
 289                          */
 290                         if (skb->protocol != proto) {
 291                                 kfree_skb(skb);
 292                                 return -EINVAL;
 293                         }
 294                         /* If the header was expanded, headroom might be too
 295                          * small for L2 header to come, expand as needed.
 296                          */
 297                         ret = xmit_check_hhlen(skb, hh_len);
 298                         if (unlikely(ret))
 299                                 return ret;
 300
 301                         return LWTUNNEL_XMIT_CONTINUE;
 302                 case BPF_REDIRECT:
 303                         return LWTUNNEL_XMIT_DONE;
 304                 case BPF_LWT_REROUTE:
 305                         return bpf_lwt_xmit_reroute(skb);
 306                 default:
 307                         return ret;
 308                 }
 309         }
 310
 311         return LWTUNNEL_XMIT_CONTINUE;
 312 }
 313
 314 static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog)
 315 {
 316         if (prog->prog)
 317                 bpf_prog_put(prog->prog);
 318
 319         kfree(prog->name);
 320 }
 321
 322 static void bpf_destroy_state(struct lwtunnel_state *lwt)
 323 {
 324         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 325
 326         bpf_lwt_prog_destroy(&bpf->in);
 327         bpf_lwt_prog_destroy(&bpf->out);
 328         bpf_lwt_prog_destroy(&bpf->xmit);
 329 }
 330
 331 static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = {
 332         [LWT_BPF_PROG_FD]   = { .type = NLA_U32, },
 333         [LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
 334                                 .len = MAX_PROG_NAME },
 335 };
 336
 337 static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog,
 338                           enum bpf_prog_type type)
 339 {
 340         struct nlattr *tb[LWT_BPF_PROG_MAX + 1];
 341         struct bpf_prog *p;
 342         int ret;
 343         u32 fd;
 344
 345         ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr,
 346                                           bpf_prog_policy, NULL);
 347         if (ret < 0)
 348                 return ret;
 349
 350         if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME])
 351                 return -EINVAL;
 352
 353         prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC);
 354         if (!prog->name)
 355                 return -ENOMEM;
 356
 357         fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
 358         p = bpf_prog_get_type(fd, type);
 359         if (IS_ERR(p))
 360                 return PTR_ERR(p);
 361
 362         prog->prog = p;
 363
 364         return 0;
 365 }
 366
 367 static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = {
 368         [LWT_BPF_IN]            = { .type = NLA_NESTED, },
 369         [LWT_BPF_OUT]           = { .type = NLA_NESTED, },
 370         [LWT_BPF_XMIT]          = { .type = NLA_NESTED, },
 371         [LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 },
 372 };
 373
 374 static int bpf_build_state(struct net *net, struct nlattr *nla,
 375                            unsigned int family, const void *cfg,
 376                            struct lwtunnel_state **ts,
 377                            struct netlink_ext_ack *extack)
 378 {
 379         struct nlattr *tb[LWT_BPF_MAX + 1];
 380         struct lwtunnel_state *newts;
 381         struct bpf_lwt *bpf;
 382         int ret;
 383
 384         if (family != AF_INET && family != AF_INET6)
 385                 return -EAFNOSUPPORT;
 386
 387         ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy,
 388                                           extack);
 389         if (ret < 0)
 390                 return ret;
 391
 392         if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT])
 393                 return -EINVAL;
 394
 395         newts = lwtunnel_state_alloc(sizeof(*bpf));
 396         if (!newts)
 397                 return -ENOMEM;
 398
 399         newts->type = LWTUNNEL_ENCAP_BPF;
 400         bpf = bpf_lwt_lwtunnel(newts);
 401
 402         if (tb[LWT_BPF_IN]) {
 403                 newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
 404                 ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in,
 405                                      BPF_PROG_TYPE_LWT_IN);
 406                 if (ret  < 0)
 407                         goto errout;
 408         }
 409
 410         if (tb[LWT_BPF_OUT]) {
 411                 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
 412                 ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out,
 413                                      BPF_PROG_TYPE_LWT_OUT);
 414                 if (ret < 0)
 415                         goto errout;
 416         }
 417
 418         if (tb[LWT_BPF_XMIT]) {
 419                 newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
 420                 ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit,
 421                                      BPF_PROG_TYPE_LWT_XMIT);
 422                 if (ret < 0)
 423                         goto errout;
 424         }
 425
 426         if (tb[LWT_BPF_XMIT_HEADROOM]) {
 427                 u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]);
 428
 429                 if (headroom > LWT_BPF_MAX_HEADROOM) {
 430                         ret = -ERANGE;
 431                         goto errout;
 432                 }
 433
 434                 newts->headroom = headroom;
 435         }
 436
 437         bpf->family = family;
 438         *ts = newts;
 439
 440         return 0;
 441
 442 errout:
 443         bpf_destroy_state(newts);
 444         kfree(newts);
 445         return ret;
 446 }
 447
 448 static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr,
 449                              struct bpf_lwt_prog *prog)
 450 {
 451         struct nlattr *nest;
 452
 453         if (!prog->prog)
 454                 return 0;
 455
 456         nest = nla_nest_start_noflag(skb, attr);
 457         if (!nest)
 458                 return -EMSGSIZE;
 459
 460         if (prog->name &&
 461             nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name))
 462                 return -EMSGSIZE;
 463
 464         return nla_nest_end(skb, nest);
 465 }
 466
 467 static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt)
 468 {
 469         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 470
 471         if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 ||
 472             bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 ||
 473             bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0)
 474                 return -EMSGSIZE;
 475
 476         return 0;
 477 }
 478
 479 static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate)
 480 {
 481         int nest_len = nla_total_size(sizeof(struct nlattr)) +
 482                        nla_total_size(MAX_PROG_NAME) + /* LWT_BPF_PROG_NAME */
 483                        0;
 484
 485         return nest_len + /* LWT_BPF_IN */
 486                nest_len + /* LWT_BPF_OUT */
 487                nest_len + /* LWT_BPF_XMIT */
 488                0;
 489 }
 490
 491 static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b)
 492 {
 493         /* FIXME:
 494          * The LWT state is currently rebuilt for delete requests which
 495          * results in a new bpf_prog instance. Comparing names for now.
 496          */
 497         if (!a->name && !b->name)
 498                 return 0;
 499
 500         if (!a->name || !b->name)
 501                 return 1;
 502
 503         return strcmp(a->name, b->name);
 504 }
 505
 506 static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 507 {
 508         struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a);
 509         struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b);
 510
 511         return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) ||
 512                bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) ||
 513                bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit);
 514 }
 515
 516 static const struct lwtunnel_encap_ops bpf_encap_ops = {
 517         .build_state    = bpf_build_state,
 518         .destroy_state  = bpf_destroy_state,
 519         .input          = bpf_input,
 520         .output         = bpf_output,
 521         .xmit           = bpf_xmit,
 522         .fill_encap     = bpf_fill_encap_info,
 523         .get_encap_size = bpf_encap_nlsize,
 524         .cmp_encap      = bpf_encap_cmp,
 525         .owner          = THIS_MODULE,
 526 };
 527
 528 static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type,
 529                            int encap_len)
 530 {
 531         struct skb_shared_info *shinfo = skb_shinfo(skb);
 532
 533         gso_type |= SKB_GSO_DODGY;
 534         shinfo->gso_type |= gso_type;
 535         skb_decrease_gso_size(shinfo, encap_len);
 536         shinfo->gso_segs = 0;
 537         return 0;
 538 }
 539
 540 static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len)
 541 {
 542         int next_hdr_offset;
 543         void *next_hdr;
 544         __u8 protocol;
 545
 546         /* SCTP and UDP_L4 gso need more nuanced handling than what
 547          * handle_gso_type() does above: skb_decrease_gso_size() is not enough.
 548          * So at the moment only TCP GSO packets are let through.
 549          */
 550         if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
 551                 return -ENOTSUPP;
 552
 553         if (ipv4) {
 554                 protocol = ip_hdr(skb)->protocol;
 555                 next_hdr_offset = sizeof(struct iphdr);
 556                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 557         } else {
 558                 protocol = ipv6_hdr(skb)->nexthdr;
 559                 next_hdr_offset = sizeof(struct ipv6hdr);
 560                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 561         }
 562
 563         switch (protocol) {
 564         case IPPROTO_GRE:
 565                 next_hdr_offset += sizeof(struct gre_base_hdr);
 566                 if (next_hdr_offset > encap_len)
 567                         return -EINVAL;
 568
 569                 if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM)
 570                         return handle_gso_type(skb, SKB_GSO_GRE_CSUM,
 571                                                encap_len);
 572                 return handle_gso_type(skb, SKB_GSO_GRE, encap_len);
 573
 574         case IPPROTO_UDP:
 575                 next_hdr_offset += sizeof(struct udphdr);
 576                 if (next_hdr_offset > encap_len)
 577                         return -EINVAL;
 578
 579                 if (((struct udphdr *)next_hdr)->check)
 580                         return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM,
 581                                                encap_len);
 582                 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len);
 583
 584         case IPPROTO_IP:
 585         case IPPROTO_IPV6:
 586                 if (ipv4)
 587                         return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len);
 588                 else
 589                         return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len);
 590
 591         default:
 592                 return -EPROTONOSUPPORT;
 593         }
 594 }
 595
 596 int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress)
 597 {
 598         struct iphdr *iph;
 599         bool ipv4;
 600         int err;
 601
 602         if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM))
 603                 return -EINVAL;
 604
 605         /* validate protocol and length */
 606         iph = (struct iphdr *)hdr;
 607         if (iph->version == 4) {
 608                 ipv4 = true;
 609                 if (unlikely(len < iph->ihl * 4))
 610                         return -EINVAL;
 611         } else if (iph->version == 6) {
 612                 ipv4 = false;
 613                 if (unlikely(len < sizeof(struct ipv6hdr)))
 614                         return -EINVAL;
 615         } else {
 616                 return -EINVAL;
 617         }
 618
 619         if (ingress)
 620                 err = skb_cow_head(skb, len + skb->mac_len);
 621         else
 622                 err = skb_cow_head(skb,
 623                                    len + LL_RESERVED_SPACE(skb_dst(skb)->dev));
 624         if (unlikely(err))
 625                 return err;
 626
 627         /* push the encap headers and fix pointers */
 628         skb_reset_inner_headers(skb);
 629         skb_reset_inner_mac_header(skb);  /* mac header is not yet set */
 630         skb_set_inner_protocol(skb, skb->protocol);
 631         skb->encapsulation = 1;
 632         skb_push(skb, len);
 633         if (ingress)
 634                 skb_postpush_rcsum(skb, iph, len);
 635         skb_reset_network_header(skb);
 636         memcpy(skb_network_header(skb), hdr, len);
 637         bpf_compute_data_pointers(skb);
 638         skb_clear_hash(skb);
 639
 640         if (ipv4) {
 641                 skb->protocol = htons(ETH_P_IP);
 642                 iph = ip_hdr(skb);
 643
 644                 if (!iph->check)
 645                         iph->check = ip_fast_csum((unsigned char *)iph,
 646                                                   iph->ihl);
 647         } else {
 648                 skb->protocol = htons(ETH_P_IPV6);
 649         }
 650
 651         if (skb_is_gso(skb))
 652                 return handle_gso_encap(skb, ipv4, len);
 653
 654         return 0;
 655 }
 656
 657 static int __init bpf_lwt_init(void)
 658 {
 659         return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF);
 660 }
 661
 662 subsys_initcall(bpf_lwt_init)