net/core/lwt_bpf.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Copyright (c) 2016 Thomas Graf <tgraf@tgraf.ch>
   3  */
   4
   5 #include <linux/kernel.h>
   6 #include <linux/module.h>
   7 #include <linux/skbuff.h>
   8 #include <linux/types.h>
   9 #include <linux/bpf.h>
  10 #include <net/lwtunnel.h>
  11 #include <net/gre.h>
  12 #include <net/ip6_route.h>
  13 #include <net/ipv6_stubs.h>
  14
  15 struct bpf_lwt_prog {
  16         struct bpf_prog *prog;
  17         char *name;
  18 };
  19
  20 struct bpf_lwt {
  21         struct bpf_lwt_prog in;
  22         struct bpf_lwt_prog out;
  23         struct bpf_lwt_prog xmit;
  24         int family;
  25 };
  26
  27 #define MAX_PROG_NAME 256
  28
  29 static inline struct bpf_lwt *bpf_lwt_lwtunnel(struct lwtunnel_state *lwt)
  30 {
  31         return (struct bpf_lwt *)lwt->data;
  32 }
  33
  34 #define NO_REDIRECT false
  35 #define CAN_REDIRECT true
  36
  37 static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt,
  38                        struct dst_entry *dst, bool can_redirect)
  39 {
  40         int ret;
  41
  42         /* Preempt disable is needed to protect per-cpu redirect_info between
  43          * BPF prog and skb_do_redirect(). The call_rcu in bpf_prog_put() and
  44          * access to maps strictly require a rcu_read_lock() for protection,
  45          * mixing with BH RCU lock doesn't work.
  46          */
  47         preempt_disable();
  48         bpf_compute_data_pointers(skb);
  49         ret = bpf_prog_run_save_cb(lwt->prog, skb);
  50
  51         switch (ret) {
  52         case BPF_OK:
  53         case BPF_LWT_REROUTE:
  54                 break;
  55
  56         case BPF_REDIRECT:
  57                 if (unlikely(!can_redirect)) {
  58                         pr_warn_once("Illegal redirect return code in prog %s\n",
  59                                      lwt->name ? : "<unknown>");
  60                         ret = BPF_OK;
  61                 } else {
  62                         skb_reset_mac_header(skb);
  63                         ret = skb_do_redirect(skb);
  64                         if (ret == 0)
  65                                 ret = BPF_REDIRECT;
  66                 }
  67                 break;
  68
  69         case BPF_DROP:
  70                 kfree_skb(skb);
  71                 ret = -EPERM;
  72                 break;
  73
  74         default:
  75                 pr_warn_once("bpf-lwt: Illegal return value %u, expect packet loss\n", ret);
  76                 kfree_skb(skb);
  77                 ret = -EINVAL;
  78                 break;
  79         }
  80
  81         preempt_enable();
  82
  83         return ret;
  84 }
  85
  86 static int bpf_lwt_input_reroute(struct sk_buff *skb)
  87 {
  88         int err = -EINVAL;
  89
  90         if (skb->protocol == htons(ETH_P_IP)) {
  91                 struct net_device *dev = skb_dst(skb)->dev;
  92                 struct iphdr *iph = ip_hdr(skb);
  93
  94                 dev_hold(dev);
  95                 skb_dst_drop(skb);
  96                 err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
  97                                            iph->tos, dev);
  98                 dev_put(dev);
  99         } else if (skb->protocol == htons(ETH_P_IPV6)) {
 100                 skb_dst_drop(skb);
 101                 err = ipv6_stub->ipv6_route_input(skb);
 102         } else {
 103                 err = -EAFNOSUPPORT;
 104         }
 105
 106         if (err)
 107                 goto err;
 108         return dst_input(skb);
 109
 110 err:
 111         kfree_skb(skb);
 112         return err;
 113 }
 114
 115 static int bpf_input(struct sk_buff *skb)
 116 {
 117         struct dst_entry *dst = skb_dst(skb);
 118         struct bpf_lwt *bpf;
 119         int ret;
 120
 121         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 122         if (bpf->in.prog) {
 123                 ret = run_lwt_bpf(skb, &bpf->in, dst, NO_REDIRECT);
 124                 if (ret < 0)
 125                         return ret;
 126                 if (ret == BPF_LWT_REROUTE)
 127                         return bpf_lwt_input_reroute(skb);
 128         }
 129
 130         if (unlikely(!dst->lwtstate->orig_input)) {
 131                 kfree_skb(skb);
 132                 return -EINVAL;
 133         }
 134
 135         return dst->lwtstate->orig_input(skb);
 136 }
 137
 138 static int bpf_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 139 {
 140         struct dst_entry *dst = skb_dst(skb);
 141         struct bpf_lwt *bpf;
 142         int ret;
 143
 144         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 145         if (bpf->out.prog) {
 146                 ret = run_lwt_bpf(skb, &bpf->out, dst, NO_REDIRECT);
 147                 if (ret < 0)
 148                         return ret;
 149         }
 150
 151         if (unlikely(!dst->lwtstate->orig_output)) {
 152                 pr_warn_once("orig_output not set on dst for prog %s\n",
 153                              bpf->out.name);
 154                 kfree_skb(skb);
 155                 return -EINVAL;
 156         }
 157
 158         return dst->lwtstate->orig_output(net, sk, skb);
 159 }
 160
 161 static int xmit_check_hhlen(struct sk_buff *skb)
 162 {
 163         int hh_len = skb_dst(skb)->dev->hard_header_len;
 164
 165         if (skb_headroom(skb) < hh_len) {
 166                 int nhead = HH_DATA_ALIGN(hh_len - skb_headroom(skb));
 167
 168                 if (pskb_expand_head(skb, nhead, 0, GFP_ATOMIC))
 169                         return -ENOMEM;
 170         }
 171
 172         return 0;
 173 }
 174
 175 static int bpf_lwt_xmit_reroute(struct sk_buff *skb)
 176 {
 177         struct net_device *l3mdev = l3mdev_master_dev_rcu(skb_dst(skb)->dev);
 178         int oif = l3mdev ? l3mdev->ifindex : 0;
 179         struct dst_entry *dst = NULL;
 180         int err = -EAFNOSUPPORT;
 181         struct sock *sk;
 182         struct net *net;
 183         bool ipv4;
 184
 185         if (skb->protocol == htons(ETH_P_IP))
 186                 ipv4 = true;
 187         else if (skb->protocol == htons(ETH_P_IPV6))
 188                 ipv4 = false;
 189         else
 190                 goto err;
 191
 192         sk = sk_to_full_sk(skb->sk);
 193         if (sk) {
 194                 if (sk->sk_bound_dev_if)
 195                         oif = sk->sk_bound_dev_if;
 196                 net = sock_net(sk);
 197         } else {
 198                 net = dev_net(skb_dst(skb)->dev);
 199         }
 200
 201         if (ipv4) {
 202                 struct iphdr *iph = ip_hdr(skb);
 203                 struct flowi4 fl4 = {};
 204                 struct rtable *rt;
 205
 206                 fl4.flowi4_oif = oif;
 207                 fl4.flowi4_mark = skb->mark;
 208                 fl4.flowi4_uid = sock_net_uid(net, sk);
 209                 fl4.flowi4_tos = RT_TOS(iph->tos);
 210                 fl4.flowi4_flags = FLOWI_FLAG_ANYSRC;
 211                 fl4.flowi4_proto = iph->protocol;
 212                 fl4.daddr = iph->daddr;
 213                 fl4.saddr = iph->saddr;
 214
 215                 rt = ip_route_output_key(net, &fl4);
 216                 if (IS_ERR(rt)) {
 217                         err = PTR_ERR(rt);
 218                         goto err;
 219                 }
 220                 dst = &rt->dst;
 221         } else {
 222                 struct ipv6hdr *iph6 = ipv6_hdr(skb);
 223                 struct flowi6 fl6 = {};
 224
 225                 fl6.flowi6_oif = oif;
 226                 fl6.flowi6_mark = skb->mark;
 227                 fl6.flowi6_uid = sock_net_uid(net, sk);
 228                 fl6.flowlabel = ip6_flowinfo(iph6);
 229                 fl6.flowi6_proto = iph6->nexthdr;
 230                 fl6.daddr = iph6->daddr;
 231                 fl6.saddr = iph6->saddr;
 232
 233                 err = ipv6_stub->ipv6_dst_lookup(net, skb->sk, &dst, &fl6);
 234                 if (unlikely(err))
 235                         goto err;
 236                 if (IS_ERR(dst)) {
 237                         err = PTR_ERR(dst);
 238                         goto err;
 239                 }
 240         }
 241         if (unlikely(dst->error)) {
 242                 err = dst->error;
 243                 dst_release(dst);
 244                 goto err;
 245         }
 246
 247         /* Although skb header was reserved in bpf_lwt_push_ip_encap(), it
 248          * was done for the previous dst, so we are doing it here again, in
 249          * case the new dst needs much more space. The call below is a noop
 250          * if there is enough header space in skb.
 251          */
 252         err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 253         if (unlikely(err))
 254                 goto err;
 255
 256         skb_dst_drop(skb);
 257         skb_dst_set(skb, dst);
 258
 259         err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb);
 260         if (unlikely(err))
 261                 return err;
 262
 263         /* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */
 264         return LWTUNNEL_XMIT_DONE;
 265
 266 err:
 267         kfree_skb(skb);
 268         return err;
 269 }
 270
 271 static int bpf_xmit(struct sk_buff *skb)
 272 {
 273         struct dst_entry *dst = skb_dst(skb);
 274         struct bpf_lwt *bpf;
 275
 276         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 277         if (bpf->xmit.prog) {
 278                 __be16 proto = skb->protocol;
 279                 int ret;
 280
 281                 ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT);
 282                 switch (ret) {
 283                 case BPF_OK:
 284                         /* If the header changed, e.g. via bpf_lwt_push_encap,
 285                          * BPF_LWT_REROUTE below should have been used if the
 286                          * protocol was also changed.
 287                          */
 288                         if (skb->protocol != proto) {
 289                                 kfree_skb(skb);
 290                                 return -EINVAL;
 291                         }
 292                         /* If the header was expanded, headroom might be too
 293                          * small for L2 header to come, expand as needed.
 294                          */
 295                         ret = xmit_check_hhlen(skb);
 296                         if (unlikely(ret))
 297                                 return ret;
 298
 299                         return LWTUNNEL_XMIT_CONTINUE;
 300                 case BPF_REDIRECT:
 301                         return LWTUNNEL_XMIT_DONE;
 302                 case BPF_LWT_REROUTE:
 303                         return bpf_lwt_xmit_reroute(skb);
 304                 default:
 305                         return ret;
 306                 }
 307         }
 308
 309         return LWTUNNEL_XMIT_CONTINUE;
 310 }
 311
 312 static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog)
 313 {
 314         if (prog->prog)
 315                 bpf_prog_put(prog->prog);
 316
 317         kfree(prog->name);
 318 }
 319
 320 static void bpf_destroy_state(struct lwtunnel_state *lwt)
 321 {
 322         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 323
 324         bpf_lwt_prog_destroy(&bpf->in);
 325         bpf_lwt_prog_destroy(&bpf->out);
 326         bpf_lwt_prog_destroy(&bpf->xmit);
 327 }
 328
 329 static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = {
 330         [LWT_BPF_PROG_FD]   = { .type = NLA_U32, },
 331         [LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
 332                                 .len = MAX_PROG_NAME },
 333 };
 334
 335 static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog,
 336                           enum bpf_prog_type type)
 337 {
 338         struct nlattr *tb[LWT_BPF_PROG_MAX + 1];
 339         struct bpf_prog *p;
 340         int ret;
 341         u32 fd;
 342
 343         ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr,
 344                                           bpf_prog_policy, NULL);
 345         if (ret < 0)
 346                 return ret;
 347
 348         if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME])
 349                 return -EINVAL;
 350
 351         prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC);
 352         if (!prog->name)
 353                 return -ENOMEM;
 354
 355         fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
 356         p = bpf_prog_get_type(fd, type);
 357         if (IS_ERR(p))
 358                 return PTR_ERR(p);
 359
 360         prog->prog = p;
 361
 362         return 0;
 363 }
 364
 365 static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = {
 366         [LWT_BPF_IN]            = { .type = NLA_NESTED, },
 367         [LWT_BPF_OUT]           = { .type = NLA_NESTED, },
 368         [LWT_BPF_XMIT]          = { .type = NLA_NESTED, },
 369         [LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 },
 370 };
 371
 372 static int bpf_build_state(struct nlattr *nla,
 373                            unsigned int family, const void *cfg,
 374                            struct lwtunnel_state **ts,
 375                            struct netlink_ext_ack *extack)
 376 {
 377         struct nlattr *tb[LWT_BPF_MAX + 1];
 378         struct lwtunnel_state *newts;
 379         struct bpf_lwt *bpf;
 380         int ret;
 381
 382         if (family != AF_INET && family != AF_INET6)
 383                 return -EAFNOSUPPORT;
 384
 385         ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy,
 386                                           extack);
 387         if (ret < 0)
 388                 return ret;
 389
 390         if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT])
 391                 return -EINVAL;
 392
 393         newts = lwtunnel_state_alloc(sizeof(*bpf));
 394         if (!newts)
 395                 return -ENOMEM;
 396
 397         newts->type = LWTUNNEL_ENCAP_BPF;
 398         bpf = bpf_lwt_lwtunnel(newts);
 399
 400         if (tb[LWT_BPF_IN]) {
 401                 newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
 402                 ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in,
 403                                      BPF_PROG_TYPE_LWT_IN);
 404                 if (ret  < 0)
 405                         goto errout;
 406         }
 407
 408         if (tb[LWT_BPF_OUT]) {
 409                 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
 410                 ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out,
 411                                      BPF_PROG_TYPE_LWT_OUT);
 412                 if (ret < 0)
 413                         goto errout;
 414         }
 415
 416         if (tb[LWT_BPF_XMIT]) {
 417                 newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
 418                 ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit,
 419                                      BPF_PROG_TYPE_LWT_XMIT);
 420                 if (ret < 0)
 421                         goto errout;
 422         }
 423
 424         if (tb[LWT_BPF_XMIT_HEADROOM]) {
 425                 u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]);
 426
 427                 if (headroom > LWT_BPF_MAX_HEADROOM) {
 428                         ret = -ERANGE;
 429                         goto errout;
 430                 }
 431
 432                 newts->headroom = headroom;
 433         }
 434
 435         bpf->family = family;
 436         *ts = newts;
 437
 438         return 0;
 439
 440 errout:
 441         bpf_destroy_state(newts);
 442         kfree(newts);
 443         return ret;
 444 }
 445
 446 static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr,
 447                              struct bpf_lwt_prog *prog)
 448 {
 449         struct nlattr *nest;
 450
 451         if (!prog->prog)
 452                 return 0;
 453
 454         nest = nla_nest_start_noflag(skb, attr);
 455         if (!nest)
 456                 return -EMSGSIZE;
 457
 458         if (prog->name &&
 459             nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name))
 460                 return -EMSGSIZE;
 461
 462         return nla_nest_end(skb, nest);
 463 }
 464
 465 static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt)
 466 {
 467         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 468
 469         if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 ||
 470             bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 ||
 471             bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0)
 472                 return -EMSGSIZE;
 473
 474         return 0;
 475 }
 476
 477 static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate)
 478 {
 479         int nest_len = nla_total_size(sizeof(struct nlattr)) +
 480                        nla_total_size(MAX_PROG_NAME) + /* LWT_BPF_PROG_NAME */
 481                        0;
 482
 483         return nest_len + /* LWT_BPF_IN */
 484                nest_len + /* LWT_BPF_OUT */
 485                nest_len + /* LWT_BPF_XMIT */
 486                0;
 487 }
 488
 489 static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b)
 490 {
 491         /* FIXME:
 492          * The LWT state is currently rebuilt for delete requests which
 493          * results in a new bpf_prog instance. Comparing names for now.
 494          */
 495         if (!a->name && !b->name)
 496                 return 0;
 497
 498         if (!a->name || !b->name)
 499                 return 1;
 500
 501         return strcmp(a->name, b->name);
 502 }
 503
 504 static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 505 {
 506         struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a);
 507         struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b);
 508
 509         return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) ||
 510                bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) ||
 511                bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit);
 512 }
 513
 514 static const struct lwtunnel_encap_ops bpf_encap_ops = {
 515         .build_state    = bpf_build_state,
 516         .destroy_state  = bpf_destroy_state,
 517         .input          = bpf_input,
 518         .output         = bpf_output,
 519         .xmit           = bpf_xmit,
 520         .fill_encap     = bpf_fill_encap_info,
 521         .get_encap_size = bpf_encap_nlsize,
 522         .cmp_encap      = bpf_encap_cmp,
 523         .owner          = THIS_MODULE,
 524 };
 525
 526 static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type,
 527                            int encap_len)
 528 {
 529         struct skb_shared_info *shinfo = skb_shinfo(skb);
 530
 531         gso_type |= SKB_GSO_DODGY;
 532         shinfo->gso_type |= gso_type;
 533         skb_decrease_gso_size(shinfo, encap_len);
 534         shinfo->gso_segs = 0;
 535         return 0;
 536 }
 537
 538 static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len)
 539 {
 540         int next_hdr_offset;
 541         void *next_hdr;
 542         __u8 protocol;
 543
 544         /* SCTP and UDP_L4 gso need more nuanced handling than what
 545          * handle_gso_type() does above: skb_decrease_gso_size() is not enough.
 546          * So at the moment only TCP GSO packets are let through.
 547          */
 548         if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
 549                 return -ENOTSUPP;
 550
 551         if (ipv4) {
 552                 protocol = ip_hdr(skb)->protocol;
 553                 next_hdr_offset = sizeof(struct iphdr);
 554                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 555         } else {
 556                 protocol = ipv6_hdr(skb)->nexthdr;
 557                 next_hdr_offset = sizeof(struct ipv6hdr);
 558                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 559         }
 560
 561         switch (protocol) {
 562         case IPPROTO_GRE:
 563                 next_hdr_offset += sizeof(struct gre_base_hdr);
 564                 if (next_hdr_offset > encap_len)
 565                         return -EINVAL;
 566
 567                 if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM)
 568                         return handle_gso_type(skb, SKB_GSO_GRE_CSUM,
 569                                                encap_len);
 570                 return handle_gso_type(skb, SKB_GSO_GRE, encap_len);
 571
 572         case IPPROTO_UDP:
 573                 next_hdr_offset += sizeof(struct udphdr);
 574                 if (next_hdr_offset > encap_len)
 575                         return -EINVAL;
 576
 577                 if (((struct udphdr *)next_hdr)->check)
 578                         return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM,
 579                                                encap_len);
 580                 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len);
 581
 582         case IPPROTO_IP:
 583         case IPPROTO_IPV6:
 584                 if (ipv4)
 585                         return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len);
 586                 else
 587                         return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len);
 588
 589         default:
 590                 return -EPROTONOSUPPORT;
 591         }
 592 }
 593
 594 int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress)
 595 {
 596         struct iphdr *iph;
 597         bool ipv4;
 598         int err;
 599
 600         if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM))
 601                 return -EINVAL;
 602
 603         /* validate protocol and length */
 604         iph = (struct iphdr *)hdr;
 605         if (iph->version == 4) {
 606                 ipv4 = true;
 607                 if (unlikely(len < iph->ihl * 4))
 608                         return -EINVAL;
 609         } else if (iph->version == 6) {
 610                 ipv4 = false;
 611                 if (unlikely(len < sizeof(struct ipv6hdr)))
 612                         return -EINVAL;
 613         } else {
 614                 return -EINVAL;
 615         }
 616
 617         if (ingress)
 618                 err = skb_cow_head(skb, len + skb->mac_len);
 619         else
 620                 err = skb_cow_head(skb,
 621                                    len + LL_RESERVED_SPACE(skb_dst(skb)->dev));
 622         if (unlikely(err))
 623                 return err;
 624
 625         /* push the encap headers and fix pointers */
 626         skb_reset_inner_headers(skb);
 627         skb_reset_inner_mac_header(skb);  /* mac header is not yet set */
 628         skb_set_inner_protocol(skb, skb->protocol);
 629         skb->encapsulation = 1;
 630         skb_push(skb, len);
 631         if (ingress)
 632                 skb_postpush_rcsum(skb, iph, len);
 633         skb_reset_network_header(skb);
 634         memcpy(skb_network_header(skb), hdr, len);
 635         bpf_compute_data_pointers(skb);
 636         skb_clear_hash(skb);
 637
 638         if (ipv4) {
 639                 skb->protocol = htons(ETH_P_IP);
 640                 iph = ip_hdr(skb);
 641
 642                 if (!iph->check)
 643                         iph->check = ip_fast_csum((unsigned char *)iph,
 644                                                   iph->ihl);
 645         } else {
 646                 skb->protocol = htons(ETH_P_IPV6);
 647         }
 648
 649         if (skb_is_gso(skb))
 650                 return handle_gso_encap(skb, ipv4, len);
 651
 652         return 0;
 653 }
 654
 655 static int __init bpf_lwt_init(void)
 656 {
 657         return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF);
 658 }
 659
 660 subsys_initcall(bpf_lwt_init)