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         /* Migration disable and BH disable are needed to protect per-cpu
  43          * redirect_info between BPF prog and skb_do_redirect().
  44          */
  45         migrate_disable();
  46         local_bh_disable();
  47         bpf_compute_data_pointers(skb);
  48         ret = bpf_prog_run_save_cb(lwt->prog, skb);
  49
  50         switch (ret) {
  51         case BPF_OK:
  52         case BPF_LWT_REROUTE:
  53                 break;
  54
  55         case BPF_REDIRECT:
  56                 if (unlikely(!can_redirect)) {
  57                         pr_warn_once("Illegal redirect return code in prog %s\n",
  58                                      lwt->name ? : "<unknown>");
  59                         ret = BPF_OK;
  60                 } else {
  61                         skb_reset_mac_header(skb);
  62                         skb_do_redirect(skb);
  63                         ret = BPF_REDIRECT;
  64                 }
  65                 break;
  66
  67         case BPF_DROP:
  68                 kfree_skb(skb);
  69                 ret = -EPERM;
  70                 break;
  71
  72         default:
  73                 pr_warn_once("bpf-lwt: Illegal return value %u, expect packet loss\n", ret);
  74                 kfree_skb(skb);
  75                 ret = -EINVAL;
  76                 break;
  77         }
  78
  79         local_bh_enable();
  80         migrate_enable();
  81
  82         return ret;
  83 }
  84
  85 static int bpf_lwt_input_reroute(struct sk_buff *skb)
  86 {
  87         int err = -EINVAL;
  88
  89         if (skb->protocol == htons(ETH_P_IP)) {
  90                 struct net_device *dev = skb_dst(skb)->dev;
  91                 struct iphdr *iph = ip_hdr(skb);
  92
  93                 dev_hold(dev);
  94                 skb_dst_drop(skb);
  95                 err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
  96                                            iph->tos, dev);
  97                 dev_put(dev);
  98         } else if (skb->protocol == htons(ETH_P_IPV6)) {
  99                 skb_dst_drop(skb);
 100                 err = ipv6_stub->ipv6_route_input(skb);
 101         } else {
 102                 err = -EAFNOSUPPORT;
 103         }
 104
 105         if (err)
 106                 goto err;
 107         return dst_input(skb);
 108
 109 err:
 110         kfree_skb(skb);
 111         return err;
 112 }
 113
 114 static int bpf_input(struct sk_buff *skb)
 115 {
 116         struct dst_entry *dst = skb_dst(skb);
 117         struct bpf_lwt *bpf;
 118         int ret;
 119
 120         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 121         if (bpf->in.prog) {
 122                 ret = run_lwt_bpf(skb, &bpf->in, dst, NO_REDIRECT);
 123                 if (ret < 0)
 124                         return ret;
 125                 if (ret == BPF_LWT_REROUTE)
 126                         return bpf_lwt_input_reroute(skb);
 127         }
 128
 129         if (unlikely(!dst->lwtstate->orig_input)) {
 130                 kfree_skb(skb);
 131                 return -EINVAL;
 132         }
 133
 134         return dst->lwtstate->orig_input(skb);
 135 }
 136
 137 static int bpf_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 138 {
 139         struct dst_entry *dst = skb_dst(skb);
 140         struct bpf_lwt *bpf;
 141         int ret;
 142
 143         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 144         if (bpf->out.prog) {
 145                 ret = run_lwt_bpf(skb, &bpf->out, dst, NO_REDIRECT);
 146                 if (ret < 0)
 147                         return ret;
 148         }
 149
 150         if (unlikely(!dst->lwtstate->orig_output)) {
 151                 pr_warn_once("orig_output not set on dst for prog %s\n",
 152                              bpf->out.name);
 153                 kfree_skb(skb);
 154                 return -EINVAL;
 155         }
 156
 157         return dst->lwtstate->orig_output(net, sk, skb);
 158 }
 159
 160 static int xmit_check_hhlen(struct sk_buff *skb, int hh_len)
 161 {
 162         if (skb_headroom(skb) < hh_len) {
 163                 int nhead = HH_DATA_ALIGN(hh_len - skb_headroom(skb));
 164
 165                 if (pskb_expand_head(skb, nhead, 0, GFP_ATOMIC))
 166                         return -ENOMEM;
 167         }
 168
 169         return 0;
 170 }
 171
 172 static int bpf_lwt_xmit_reroute(struct sk_buff *skb)
 173 {
 174         struct net_device *l3mdev = l3mdev_master_dev_rcu(skb_dst(skb)->dev);
 175         int oif = l3mdev ? l3mdev->ifindex : 0;
 176         struct dst_entry *dst = NULL;
 177         int err = -EAFNOSUPPORT;
 178         struct sock *sk;
 179         struct net *net;
 180         bool ipv4;
 181
 182         if (skb->protocol == htons(ETH_P_IP))
 183                 ipv4 = true;
 184         else if (skb->protocol == htons(ETH_P_IPV6))
 185                 ipv4 = false;
 186         else
 187                 goto err;
 188
 189         sk = sk_to_full_sk(skb->sk);
 190         if (sk) {
 191                 if (sk->sk_bound_dev_if)
 192                         oif = sk->sk_bound_dev_if;
 193                 net = sock_net(sk);
 194         } else {
 195                 net = dev_net(skb_dst(skb)->dev);
 196         }
 197
 198         if (ipv4) {
 199                 struct iphdr *iph = ip_hdr(skb);
 200                 struct flowi4 fl4 = {};
 201                 struct rtable *rt;
 202
 203                 fl4.flowi4_oif = oif;
 204                 fl4.flowi4_mark = skb->mark;
 205                 fl4.flowi4_uid = sock_net_uid(net, sk);
 206                 fl4.flowi4_tos = RT_TOS(iph->tos);
 207                 fl4.flowi4_flags = FLOWI_FLAG_ANYSRC;
 208                 fl4.flowi4_proto = iph->protocol;
 209                 fl4.daddr = iph->daddr;
 210                 fl4.saddr = iph->saddr;
 211
 212                 rt = ip_route_output_key(net, &fl4);
 213                 if (IS_ERR(rt)) {
 214                         err = PTR_ERR(rt);
 215                         goto err;
 216                 }
 217                 dst = &rt->dst;
 218         } else {
 219                 struct ipv6hdr *iph6 = ipv6_hdr(skb);
 220                 struct flowi6 fl6 = {};
 221
 222                 fl6.flowi6_oif = oif;
 223                 fl6.flowi6_mark = skb->mark;
 224                 fl6.flowi6_uid = sock_net_uid(net, sk);
 225                 fl6.flowlabel = ip6_flowinfo(iph6);
 226                 fl6.flowi6_proto = iph6->nexthdr;
 227                 fl6.daddr = iph6->daddr;
 228                 fl6.saddr = iph6->saddr;
 229
 230                 dst = ipv6_stub->ipv6_dst_lookup_flow(net, skb->sk, &fl6, NULL);
 231                 if (IS_ERR(dst)) {
 232                         err = PTR_ERR(dst);
 233                         goto err;
 234                 }
 235         }
 236         if (unlikely(dst->error)) {
 237                 err = dst->error;
 238                 dst_release(dst);
 239                 goto err;
 240         }
 241
 242         /* Although skb header was reserved in bpf_lwt_push_ip_encap(), it
 243          * was done for the previous dst, so we are doing it here again, in
 244          * case the new dst needs much more space. The call below is a noop
 245          * if there is enough header space in skb.
 246          */
 247         err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 248         if (unlikely(err))
 249                 goto err;
 250
 251         skb_dst_drop(skb);
 252         skb_dst_set(skb, dst);
 253
 254         err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb);
 255         if (unlikely(err))
 256                 return net_xmit_errno(err);
 257
 258         /* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */
 259         return LWTUNNEL_XMIT_DONE;
 260
 261 err:
 262         kfree_skb(skb);
 263         return err;
 264 }
 265
 266 static int bpf_xmit(struct sk_buff *skb)
 267 {
 268         struct dst_entry *dst = skb_dst(skb);
 269         struct bpf_lwt *bpf;
 270
 271         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 272         if (bpf->xmit.prog) {
 273                 int hh_len = dst->dev->hard_header_len;
 274                 __be16 proto = skb->protocol;
 275                 int ret;
 276
 277                 ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT);
 278                 switch (ret) {
 279                 case BPF_OK:
 280                         /* If the header changed, e.g. via bpf_lwt_push_encap,
 281                          * BPF_LWT_REROUTE below should have been used if the
 282                          * protocol was also changed.
 283                          */
 284                         if (skb->protocol != proto) {
 285                                 kfree_skb(skb);
 286                                 return -EINVAL;
 287                         }
 288                         /* If the header was expanded, headroom might be too
 289                          * small for L2 header to come, expand as needed.
 290                          */
 291                         ret = xmit_check_hhlen(skb, hh_len);
 292                         if (unlikely(ret))
 293                                 return ret;
 294
 295                         return LWTUNNEL_XMIT_CONTINUE;
 296                 case BPF_REDIRECT:
 297                         return LWTUNNEL_XMIT_DONE;
 298                 case BPF_LWT_REROUTE:
 299                         return bpf_lwt_xmit_reroute(skb);
 300                 default:
 301                         return ret;
 302                 }
 303         }
 304
 305         return LWTUNNEL_XMIT_CONTINUE;
 306 }
 307
 308 static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog)
 309 {
 310         if (prog->prog)
 311                 bpf_prog_put(prog->prog);
 312
 313         kfree(prog->name);
 314 }
 315
 316 static void bpf_destroy_state(struct lwtunnel_state *lwt)
 317 {
 318         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 319
 320         bpf_lwt_prog_destroy(&bpf->in);
 321         bpf_lwt_prog_destroy(&bpf->out);
 322         bpf_lwt_prog_destroy(&bpf->xmit);
 323 }
 324
 325 static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = {
 326         [LWT_BPF_PROG_FD]   = { .type = NLA_U32, },
 327         [LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
 328                                 .len = MAX_PROG_NAME },
 329 };
 330
 331 static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog,
 332                           enum bpf_prog_type type)
 333 {
 334         struct nlattr *tb[LWT_BPF_PROG_MAX + 1];
 335         struct bpf_prog *p;
 336         int ret;
 337         u32 fd;
 338
 339         ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr,
 340                                           bpf_prog_policy, NULL);
 341         if (ret < 0)
 342                 return ret;
 343
 344         if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME])
 345                 return -EINVAL;
 346
 347         prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC);
 348         if (!prog->name)
 349                 return -ENOMEM;
 350
 351         fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
 352         p = bpf_prog_get_type(fd, type);
 353         if (IS_ERR(p))
 354                 return PTR_ERR(p);
 355
 356         prog->prog = p;
 357
 358         return 0;
 359 }
 360
 361 static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = {
 362         [LWT_BPF_IN]            = { .type = NLA_NESTED, },
 363         [LWT_BPF_OUT]           = { .type = NLA_NESTED, },
 364         [LWT_BPF_XMIT]          = { .type = NLA_NESTED, },
 365         [LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 },
 366 };
 367
 368 static int bpf_build_state(struct net *net, struct nlattr *nla,
 369                            unsigned int family, const void *cfg,
 370                            struct lwtunnel_state **ts,
 371                            struct netlink_ext_ack *extack)
 372 {
 373         struct nlattr *tb[LWT_BPF_MAX + 1];
 374         struct lwtunnel_state *newts;
 375         struct bpf_lwt *bpf;
 376         int ret;
 377
 378         if (family != AF_INET && family != AF_INET6)
 379                 return -EAFNOSUPPORT;
 380
 381         ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy,
 382                                           extack);
 383         if (ret < 0)
 384                 return ret;
 385
 386         if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT])
 387                 return -EINVAL;
 388
 389         newts = lwtunnel_state_alloc(sizeof(*bpf));
 390         if (!newts)
 391                 return -ENOMEM;
 392
 393         newts->type = LWTUNNEL_ENCAP_BPF;
 394         bpf = bpf_lwt_lwtunnel(newts);
 395
 396         if (tb[LWT_BPF_IN]) {
 397                 newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
 398                 ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in,
 399                                      BPF_PROG_TYPE_LWT_IN);
 400                 if (ret  < 0)
 401                         goto errout;
 402         }
 403
 404         if (tb[LWT_BPF_OUT]) {
 405                 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
 406                 ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out,
 407                                      BPF_PROG_TYPE_LWT_OUT);
 408                 if (ret < 0)
 409                         goto errout;
 410         }
 411
 412         if (tb[LWT_BPF_XMIT]) {
 413                 newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
 414                 ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit,
 415                                      BPF_PROG_TYPE_LWT_XMIT);
 416                 if (ret < 0)
 417                         goto errout;
 418         }
 419
 420         if (tb[LWT_BPF_XMIT_HEADROOM]) {
 421                 u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]);
 422
 423                 if (headroom > LWT_BPF_MAX_HEADROOM) {
 424                         ret = -ERANGE;
 425                         goto errout;
 426                 }
 427
 428                 newts->headroom = headroom;
 429         }
 430
 431         bpf->family = family;
 432         *ts = newts;
 433
 434         return 0;
 435
 436 errout:
 437         bpf_destroy_state(newts);
 438         kfree(newts);
 439         return ret;
 440 }
 441
 442 static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr,
 443                              struct bpf_lwt_prog *prog)
 444 {
 445         struct nlattr *nest;
 446
 447         if (!prog->prog)
 448                 return 0;
 449
 450         nest = nla_nest_start_noflag(skb, attr);
 451         if (!nest)
 452                 return -EMSGSIZE;
 453
 454         if (prog->name &&
 455             nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name))
 456                 return -EMSGSIZE;
 457
 458         return nla_nest_end(skb, nest);
 459 }
 460
 461 static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt)
 462 {
 463         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 464
 465         if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 ||
 466             bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 ||
 467             bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0)
 468                 return -EMSGSIZE;
 469
 470         return 0;
 471 }
 472
 473 static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate)
 474 {
 475         int nest_len = nla_total_size(sizeof(struct nlattr)) +
 476                        nla_total_size(MAX_PROG_NAME) + /* LWT_BPF_PROG_NAME */
 477                        0;
 478
 479         return nest_len + /* LWT_BPF_IN */
 480                nest_len + /* LWT_BPF_OUT */
 481                nest_len + /* LWT_BPF_XMIT */
 482                0;
 483 }
 484
 485 static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b)
 486 {
 487         /* FIXME:
 488          * The LWT state is currently rebuilt for delete requests which
 489          * results in a new bpf_prog instance. Comparing names for now.
 490          */
 491         if (!a->name && !b->name)
 492                 return 0;
 493
 494         if (!a->name || !b->name)
 495                 return 1;
 496
 497         return strcmp(a->name, b->name);
 498 }
 499
 500 static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 501 {
 502         struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a);
 503         struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b);
 504
 505         return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) ||
 506                bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) ||
 507                bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit);
 508 }
 509
 510 static const struct lwtunnel_encap_ops bpf_encap_ops = {
 511         .build_state    = bpf_build_state,
 512         .destroy_state  = bpf_destroy_state,
 513         .input          = bpf_input,
 514         .output         = bpf_output,
 515         .xmit           = bpf_xmit,
 516         .fill_encap     = bpf_fill_encap_info,
 517         .get_encap_size = bpf_encap_nlsize,
 518         .cmp_encap      = bpf_encap_cmp,
 519         .owner          = THIS_MODULE,
 520 };
 521
 522 static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type,
 523                            int encap_len)
 524 {
 525         struct skb_shared_info *shinfo = skb_shinfo(skb);
 526
 527         gso_type |= SKB_GSO_DODGY;
 528         shinfo->gso_type |= gso_type;
 529         skb_decrease_gso_size(shinfo, encap_len);
 530         shinfo->gso_segs = 0;
 531         return 0;
 532 }
 533
 534 static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len)
 535 {
 536         int next_hdr_offset;
 537         void *next_hdr;
 538         __u8 protocol;
 539
 540         /* SCTP and UDP_L4 gso need more nuanced handling than what
 541          * handle_gso_type() does above: skb_decrease_gso_size() is not enough.
 542          * So at the moment only TCP GSO packets are let through.
 543          */
 544         if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
 545                 return -ENOTSUPP;
 546
 547         if (ipv4) {
 548                 protocol = ip_hdr(skb)->protocol;
 549                 next_hdr_offset = sizeof(struct iphdr);
 550                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 551         } else {
 552                 protocol = ipv6_hdr(skb)->nexthdr;
 553                 next_hdr_offset = sizeof(struct ipv6hdr);
 554                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 555         }
 556
 557         switch (protocol) {
 558         case IPPROTO_GRE:
 559                 next_hdr_offset += sizeof(struct gre_base_hdr);
 560                 if (next_hdr_offset > encap_len)
 561                         return -EINVAL;
 562
 563                 if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM)
 564                         return handle_gso_type(skb, SKB_GSO_GRE_CSUM,
 565                                                encap_len);
 566                 return handle_gso_type(skb, SKB_GSO_GRE, encap_len);
 567
 568         case IPPROTO_UDP:
 569                 next_hdr_offset += sizeof(struct udphdr);
 570                 if (next_hdr_offset > encap_len)
 571                         return -EINVAL;
 572
 573                 if (((struct udphdr *)next_hdr)->check)
 574                         return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM,
 575                                                encap_len);
 576                 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len);
 577
 578         case IPPROTO_IP:
 579         case IPPROTO_IPV6:
 580                 if (ipv4)
 581                         return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len);
 582                 else
 583                         return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len);
 584
 585         default:
 586                 return -EPROTONOSUPPORT;
 587         }
 588 }
 589
 590 int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress)
 591 {
 592         struct iphdr *iph;
 593         bool ipv4;
 594         int err;
 595
 596         if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM))
 597                 return -EINVAL;
 598
 599         /* validate protocol and length */
 600         iph = (struct iphdr *)hdr;
 601         if (iph->version == 4) {
 602                 ipv4 = true;
 603                 if (unlikely(len < iph->ihl * 4))
 604                         return -EINVAL;
 605         } else if (iph->version == 6) {
 606                 ipv4 = false;
 607                 if (unlikely(len < sizeof(struct ipv6hdr)))
 608                         return -EINVAL;
 609         } else {
 610                 return -EINVAL;
 611         }
 612
 613         if (ingress)
 614                 err = skb_cow_head(skb, len + skb->mac_len);
 615         else
 616                 err = skb_cow_head(skb,
 617                                    len + LL_RESERVED_SPACE(skb_dst(skb)->dev));
 618         if (unlikely(err))
 619                 return err;
 620
 621         /* push the encap headers and fix pointers */
 622         skb_reset_inner_headers(skb);
 623         skb_reset_inner_mac_header(skb);  /* mac header is not yet set */
 624         skb_set_inner_protocol(skb, skb->protocol);
 625         skb->encapsulation = 1;
 626         skb_push(skb, len);
 627         if (ingress)
 628                 skb_postpush_rcsum(skb, iph, len);
 629         skb_reset_network_header(skb);
 630         memcpy(skb_network_header(skb), hdr, len);
 631         bpf_compute_data_pointers(skb);
 632         skb_clear_hash(skb);
 633
 634         if (ipv4) {
 635                 skb->protocol = htons(ETH_P_IP);
 636                 iph = ip_hdr(skb);
 637
 638                 if (!iph->check)
 639                         iph->check = ip_fast_csum((unsigned char *)iph,
 640                                                   iph->ihl);
 641         } else {
 642                 skb->protocol = htons(ETH_P_IPV6);
 643         }
 644
 645         if (skb_is_gso(skb))
 646                 return handle_gso_encap(skb, ipv4, len);
 647
 648         return 0;
 649 }
 650
 651 static int __init bpf_lwt_init(void)
 652 {
 653         return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF);
 654 }
 655
 656 subsys_initcall(bpf_lwt_init)