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/ip6_route.h>
  14 #include <net/ipv6_stubs.h>
  15
  16 struct bpf_lwt_prog {
  17         struct bpf_prog *prog;
  18         char *name;
  19 };
  20
  21 struct bpf_lwt {
  22         struct bpf_lwt_prog in;
  23         struct bpf_lwt_prog out;
  24         struct bpf_lwt_prog xmit;
  25         int family;
  26 };
  27
  28 #define MAX_PROG_NAME 256
  29
  30 static inline struct bpf_lwt *bpf_lwt_lwtunnel(struct lwtunnel_state *lwt)
  31 {
  32         return (struct bpf_lwt *)lwt->data;
  33 }
  34
  35 #define NO_REDIRECT false
  36 #define CAN_REDIRECT true
  37
  38 static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt,
  39                        struct dst_entry *dst, bool can_redirect)
  40 {
  41         int ret;
  42
  43         /* Migration disable and BH disable are needed to protect per-cpu
  44          * redirect_info between BPF prog and skb_do_redirect().
  45          */
  46         migrate_disable();
  47         local_bh_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                         skb_do_redirect(skb);
  64                         ret = BPF_REDIRECT;
  65                 }
  66                 break;
  67
  68         case BPF_DROP:
  69                 kfree_skb(skb);
  70                 ret = -EPERM;
  71                 break;
  72
  73         default:
  74                 pr_warn_once("bpf-lwt: Illegal return value %u, expect packet loss\n", ret);
  75                 kfree_skb(skb);
  76                 ret = -EINVAL;
  77                 break;
  78         }
  79
  80         local_bh_enable();
  81         migrate_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, int hh_len)
 162 {
 163         if (skb_headroom(skb) < hh_len) {
 164                 int nhead = HH_DATA_ALIGN(hh_len - skb_headroom(skb));
 165
 166                 if (pskb_expand_head(skb, nhead, 0, GFP_ATOMIC))
 167                         return -ENOMEM;
 168         }
 169
 170         return 0;
 171 }
 172
 173 static int bpf_lwt_xmit_reroute(struct sk_buff *skb)
 174 {
 175         struct net_device *l3mdev = l3mdev_master_dev_rcu(skb_dst(skb)->dev);
 176         int oif = l3mdev ? l3mdev->ifindex : 0;
 177         struct dst_entry *dst = NULL;
 178         int err = -EAFNOSUPPORT;
 179         struct sock *sk;
 180         struct net *net;
 181         bool ipv4;
 182
 183         if (skb->protocol == htons(ETH_P_IP))
 184                 ipv4 = true;
 185         else if (skb->protocol == htons(ETH_P_IPV6))
 186                 ipv4 = false;
 187         else
 188                 goto err;
 189
 190         sk = sk_to_full_sk(skb->sk);
 191         if (sk) {
 192                 if (sk->sk_bound_dev_if)
 193                         oif = sk->sk_bound_dev_if;
 194                 net = sock_net(sk);
 195         } else {
 196                 net = dev_net(skb_dst(skb)->dev);
 197         }
 198
 199         if (ipv4) {
 200                 struct iphdr *iph = ip_hdr(skb);
 201                 struct flowi4 fl4 = {};
 202                 struct rtable *rt;
 203
 204                 fl4.flowi4_oif = oif;
 205                 fl4.flowi4_mark = skb->mark;
 206                 fl4.flowi4_uid = sock_net_uid(net, sk);
 207                 fl4.flowi4_tos = RT_TOS(iph->tos);
 208                 fl4.flowi4_flags = FLOWI_FLAG_ANYSRC;
 209                 fl4.flowi4_proto = iph->protocol;
 210                 fl4.daddr = iph->daddr;
 211                 fl4.saddr = iph->saddr;
 212
 213                 rt = ip_route_output_key(net, &fl4);
 214                 if (IS_ERR(rt)) {
 215                         err = PTR_ERR(rt);
 216                         goto err;
 217                 }
 218                 dst = &rt->dst;
 219         } else {
 220                 struct ipv6hdr *iph6 = ipv6_hdr(skb);
 221                 struct flowi6 fl6 = {};
 222
 223                 fl6.flowi6_oif = oif;
 224                 fl6.flowi6_mark = skb->mark;
 225                 fl6.flowi6_uid = sock_net_uid(net, sk);
 226                 fl6.flowlabel = ip6_flowinfo(iph6);
 227                 fl6.flowi6_proto = iph6->nexthdr;
 228                 fl6.daddr = iph6->daddr;
 229                 fl6.saddr = iph6->saddr;
 230
 231                 dst = ipv6_stub->ipv6_dst_lookup_flow(net, skb->sk, &fl6, NULL);
 232                 if (IS_ERR(dst)) {
 233                         err = PTR_ERR(dst);
 234                         goto err;
 235                 }
 236         }
 237         if (unlikely(dst->error)) {
 238                 err = dst->error;
 239                 dst_release(dst);
 240                 goto err;
 241         }
 242
 243         /* Although skb header was reserved in bpf_lwt_push_ip_encap(), it
 244          * was done for the previous dst, so we are doing it here again, in
 245          * case the new dst needs much more space. The call below is a noop
 246          * if there is enough header space in skb.
 247          */
 248         err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 249         if (unlikely(err))
 250                 goto err;
 251
 252         skb_dst_drop(skb);
 253         skb_dst_set(skb, dst);
 254
 255         err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb);
 256         if (unlikely(err))
 257                 return net_xmit_errno(err);
 258
 259         /* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */
 260         return LWTUNNEL_XMIT_DONE;
 261
 262 err:
 263         kfree_skb(skb);
 264         return err;
 265 }
 266
 267 static int bpf_xmit(struct sk_buff *skb)
 268 {
 269         struct dst_entry *dst = skb_dst(skb);
 270         struct bpf_lwt *bpf;
 271
 272         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 273         if (bpf->xmit.prog) {
 274                 int hh_len = dst->dev->hard_header_len;
 275                 __be16 proto = skb->protocol;
 276                 int ret;
 277
 278                 ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT);
 279                 switch (ret) {
 280                 case BPF_OK:
 281                         /* If the header changed, e.g. via bpf_lwt_push_encap,
 282                          * BPF_LWT_REROUTE below should have been used if the
 283                          * protocol was also changed.
 284                          */
 285                         if (skb->protocol != proto) {
 286                                 kfree_skb(skb);
 287                                 return -EINVAL;
 288                         }
 289                         /* If the header was expanded, headroom might be too
 290                          * small for L2 header to come, expand as needed.
 291                          */
 292                         ret = xmit_check_hhlen(skb, hh_len);
 293                         if (unlikely(ret))
 294                                 return ret;
 295
 296                         return LWTUNNEL_XMIT_CONTINUE;
 297                 case BPF_REDIRECT:
 298                         return LWTUNNEL_XMIT_DONE;
 299                 case BPF_LWT_REROUTE:
 300                         return bpf_lwt_xmit_reroute(skb);
 301                 default:
 302                         return ret;
 303                 }
 304         }
 305
 306         return LWTUNNEL_XMIT_CONTINUE;
 307 }
 308
 309 static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog)
 310 {
 311         if (prog->prog)
 312                 bpf_prog_put(prog->prog);
 313
 314         kfree(prog->name);
 315 }
 316
 317 static void bpf_destroy_state(struct lwtunnel_state *lwt)
 318 {
 319         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 320
 321         bpf_lwt_prog_destroy(&bpf->in);
 322         bpf_lwt_prog_destroy(&bpf->out);
 323         bpf_lwt_prog_destroy(&bpf->xmit);
 324 }
 325
 326 static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = {
 327         [LWT_BPF_PROG_FD]   = { .type = NLA_U32, },
 328         [LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
 329                                 .len = MAX_PROG_NAME },
 330 };
 331
 332 static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog,
 333                           enum bpf_prog_type type)
 334 {
 335         struct nlattr *tb[LWT_BPF_PROG_MAX + 1];
 336         struct bpf_prog *p;
 337         int ret;
 338         u32 fd;
 339
 340         ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr,
 341                                           bpf_prog_policy, NULL);
 342         if (ret < 0)
 343                 return ret;
 344
 345         if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME])
 346                 return -EINVAL;
 347
 348         prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC);
 349         if (!prog->name)
 350                 return -ENOMEM;
 351
 352         fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
 353         p = bpf_prog_get_type(fd, type);
 354         if (IS_ERR(p))
 355                 return PTR_ERR(p);
 356
 357         prog->prog = p;
 358
 359         return 0;
 360 }
 361
 362 static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = {
 363         [LWT_BPF_IN]            = { .type = NLA_NESTED, },
 364         [LWT_BPF_OUT]           = { .type = NLA_NESTED, },
 365         [LWT_BPF_XMIT]          = { .type = NLA_NESTED, },
 366         [LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 },
 367 };
 368
 369 static int bpf_build_state(struct net *net, struct nlattr *nla,
 370                            unsigned int family, const void *cfg,
 371                            struct lwtunnel_state **ts,
 372                            struct netlink_ext_ack *extack)
 373 {
 374         struct nlattr *tb[LWT_BPF_MAX + 1];
 375         struct lwtunnel_state *newts;
 376         struct bpf_lwt *bpf;
 377         int ret;
 378
 379         if (family != AF_INET && family != AF_INET6)
 380                 return -EAFNOSUPPORT;
 381
 382         ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy,
 383                                           extack);
 384         if (ret < 0)
 385                 return ret;
 386
 387         if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT])
 388                 return -EINVAL;
 389
 390         newts = lwtunnel_state_alloc(sizeof(*bpf));
 391         if (!newts)
 392                 return -ENOMEM;
 393
 394         newts->type = LWTUNNEL_ENCAP_BPF;
 395         bpf = bpf_lwt_lwtunnel(newts);
 396
 397         if (tb[LWT_BPF_IN]) {
 398                 newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
 399                 ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in,
 400                                      BPF_PROG_TYPE_LWT_IN);
 401                 if (ret  < 0)
 402                         goto errout;
 403         }
 404
 405         if (tb[LWT_BPF_OUT]) {
 406                 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
 407                 ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out,
 408                                      BPF_PROG_TYPE_LWT_OUT);
 409                 if (ret < 0)
 410                         goto errout;
 411         }
 412
 413         if (tb[LWT_BPF_XMIT]) {
 414                 newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
 415                 ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit,
 416                                      BPF_PROG_TYPE_LWT_XMIT);
 417                 if (ret < 0)
 418                         goto errout;
 419         }
 420
 421         if (tb[LWT_BPF_XMIT_HEADROOM]) {
 422                 u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]);
 423
 424                 if (headroom > LWT_BPF_MAX_HEADROOM) {
 425                         ret = -ERANGE;
 426                         goto errout;
 427                 }
 428
 429                 newts->headroom = headroom;
 430         }
 431
 432         bpf->family = family;
 433         *ts = newts;
 434
 435         return 0;
 436
 437 errout:
 438         bpf_destroy_state(newts);
 439         kfree(newts);
 440         return ret;
 441 }
 442
 443 static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr,
 444                              struct bpf_lwt_prog *prog)
 445 {
 446         struct nlattr *nest;
 447
 448         if (!prog->prog)
 449                 return 0;
 450
 451         nest = nla_nest_start_noflag(skb, attr);
 452         if (!nest)
 453                 return -EMSGSIZE;
 454
 455         if (prog->name &&
 456             nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name))
 457                 return -EMSGSIZE;
 458
 459         return nla_nest_end(skb, nest);
 460 }
 461
 462 static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt)
 463 {
 464         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 465
 466         if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 ||
 467             bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 ||
 468             bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0)
 469                 return -EMSGSIZE;
 470
 471         return 0;
 472 }
 473
 474 static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate)
 475 {
 476         int nest_len = nla_total_size(sizeof(struct nlattr)) +
 477                        nla_total_size(MAX_PROG_NAME) + /* LWT_BPF_PROG_NAME */
 478                        0;
 479
 480         return nest_len + /* LWT_BPF_IN */
 481                nest_len + /* LWT_BPF_OUT */
 482                nest_len + /* LWT_BPF_XMIT */
 483                0;
 484 }
 485
 486 static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b)
 487 {
 488         /* FIXME:
 489          * The LWT state is currently rebuilt for delete requests which
 490          * results in a new bpf_prog instance. Comparing names for now.
 491          */
 492         if (!a->name && !b->name)
 493                 return 0;
 494
 495         if (!a->name || !b->name)
 496                 return 1;
 497
 498         return strcmp(a->name, b->name);
 499 }
 500
 501 static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 502 {
 503         struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a);
 504         struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b);
 505
 506         return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) ||
 507                bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) ||
 508                bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit);
 509 }
 510
 511 static const struct lwtunnel_encap_ops bpf_encap_ops = {
 512         .build_state    = bpf_build_state,
 513         .destroy_state  = bpf_destroy_state,
 514         .input          = bpf_input,
 515         .output         = bpf_output,
 516         .xmit           = bpf_xmit,
 517         .fill_encap     = bpf_fill_encap_info,
 518         .get_encap_size = bpf_encap_nlsize,
 519         .cmp_encap      = bpf_encap_cmp,
 520         .owner          = THIS_MODULE,
 521 };
 522
 523 static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type,
 524                            int encap_len)
 525 {
 526         struct skb_shared_info *shinfo = skb_shinfo(skb);
 527
 528         gso_type |= SKB_GSO_DODGY;
 529         shinfo->gso_type |= gso_type;
 530         skb_decrease_gso_size(shinfo, encap_len);
 531         shinfo->gso_segs = 0;
 532         return 0;
 533 }
 534
 535 static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len)
 536 {
 537         int next_hdr_offset;
 538         void *next_hdr;
 539         __u8 protocol;
 540
 541         /* SCTP and UDP_L4 gso need more nuanced handling than what
 542          * handle_gso_type() does above: skb_decrease_gso_size() is not enough.
 543          * So at the moment only TCP GSO packets are let through.
 544          */
 545         if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
 546                 return -ENOTSUPP;
 547
 548         if (ipv4) {
 549                 protocol = ip_hdr(skb)->protocol;
 550                 next_hdr_offset = sizeof(struct iphdr);
 551                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 552         } else {
 553                 protocol = ipv6_hdr(skb)->nexthdr;
 554                 next_hdr_offset = sizeof(struct ipv6hdr);
 555                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 556         }
 557
 558         switch (protocol) {
 559         case IPPROTO_GRE:
 560                 next_hdr_offset += sizeof(struct gre_base_hdr);
 561                 if (next_hdr_offset > encap_len)
 562                         return -EINVAL;
 563
 564                 if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM)
 565                         return handle_gso_type(skb, SKB_GSO_GRE_CSUM,
 566                                                encap_len);
 567                 return handle_gso_type(skb, SKB_GSO_GRE, encap_len);
 568
 569         case IPPROTO_UDP:
 570                 next_hdr_offset += sizeof(struct udphdr);
 571                 if (next_hdr_offset > encap_len)
 572                         return -EINVAL;
 573
 574                 if (((struct udphdr *)next_hdr)->check)
 575                         return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM,
 576                                                encap_len);
 577                 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len);
 578
 579         case IPPROTO_IP:
 580         case IPPROTO_IPV6:
 581                 if (ipv4)
 582                         return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len);
 583                 else
 584                         return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len);
 585
 586         default:
 587                 return -EPROTONOSUPPORT;
 588         }
 589 }
 590
 591 int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress)
 592 {
 593         struct iphdr *iph;
 594         bool ipv4;
 595         int err;
 596
 597         if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM))
 598                 return -EINVAL;
 599
 600         /* validate protocol and length */
 601         iph = (struct iphdr *)hdr;
 602         if (iph->version == 4) {
 603                 ipv4 = true;
 604                 if (unlikely(len < iph->ihl * 4))
 605                         return -EINVAL;
 606         } else if (iph->version == 6) {
 607                 ipv4 = false;
 608                 if (unlikely(len < sizeof(struct ipv6hdr)))
 609                         return -EINVAL;
 610         } else {
 611                 return -EINVAL;
 612         }
 613
 614         if (ingress)
 615                 err = skb_cow_head(skb, len + skb->mac_len);
 616         else
 617                 err = skb_cow_head(skb,
 618                                    len + LL_RESERVED_SPACE(skb_dst(skb)->dev));
 619         if (unlikely(err))
 620                 return err;
 621
 622         /* push the encap headers and fix pointers */
 623         skb_reset_inner_headers(skb);
 624         skb_reset_inner_mac_header(skb);  /* mac header is not yet set */
 625         skb_set_inner_protocol(skb, skb->protocol);
 626         skb->encapsulation = 1;
 627         skb_push(skb, len);
 628         if (ingress)
 629                 skb_postpush_rcsum(skb, iph, len);
 630         skb_reset_network_header(skb);
 631         memcpy(skb_network_header(skb), hdr, len);
 632         bpf_compute_data_pointers(skb);
 633         skb_clear_hash(skb);
 634
 635         if (ipv4) {
 636                 skb->protocol = htons(ETH_P_IP);
 637                 iph = ip_hdr(skb);
 638
 639                 if (!iph->check)
 640                         iph->check = ip_fast_csum((unsigned char *)iph,
 641                                                   iph->ihl);
 642         } else {
 643                 skb->protocol = htons(ETH_P_IPV6);
 644         }
 645
 646         if (skb_is_gso(skb))
 647                 return handle_gso_encap(skb, ipv4, len);
 648
 649         return 0;
 650 }
 651
 652 static int __init bpf_lwt_init(void)
 653 {
 654         return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF);
 655 }
 656
 657 subsys_initcall(bpf_lwt_init)