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                         ret = skb_do_redirect(skb);
  63                         if (ret == 0)
  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)
 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                 dst = ipv6_stub->ipv6_dst_lookup_flow(net, skb->sk, &fl6, NULL);
 234                 if (IS_ERR(dst)) {
 235                         err = PTR_ERR(dst);
 236                         goto err;
 237                 }
 238         }
 239         if (unlikely(dst->error)) {
 240                 err = dst->error;
 241                 dst_release(dst);
 242                 goto err;
 243         }
 244
 245         /* Although skb header was reserved in bpf_lwt_push_ip_encap(), it
 246          * was done for the previous dst, so we are doing it here again, in
 247          * case the new dst needs much more space. The call below is a noop
 248          * if there is enough header space in skb.
 249          */
 250         err = skb_cow_head(skb, LL_RESERVED_SPACE(dst->dev));
 251         if (unlikely(err))
 252                 goto err;
 253
 254         skb_dst_drop(skb);
 255         skb_dst_set(skb, dst);
 256
 257         err = dst_output(dev_net(skb_dst(skb)->dev), skb->sk, skb);
 258         if (unlikely(err))
 259                 return err;
 260
 261         /* ip[6]_finish_output2 understand LWTUNNEL_XMIT_DONE */
 262         return LWTUNNEL_XMIT_DONE;
 263
 264 err:
 265         kfree_skb(skb);
 266         return err;
 267 }
 268
 269 static int bpf_xmit(struct sk_buff *skb)
 270 {
 271         struct dst_entry *dst = skb_dst(skb);
 272         struct bpf_lwt *bpf;
 273
 274         bpf = bpf_lwt_lwtunnel(dst->lwtstate);
 275         if (bpf->xmit.prog) {
 276                 __be16 proto = skb->protocol;
 277                 int ret;
 278
 279                 ret = run_lwt_bpf(skb, &bpf->xmit, dst, CAN_REDIRECT);
 280                 switch (ret) {
 281                 case BPF_OK:
 282                         /* If the header changed, e.g. via bpf_lwt_push_encap,
 283                          * BPF_LWT_REROUTE below should have been used if the
 284                          * protocol was also changed.
 285                          */
 286                         if (skb->protocol != proto) {
 287                                 kfree_skb(skb);
 288                                 return -EINVAL;
 289                         }
 290                         /* If the header was expanded, headroom might be too
 291                          * small for L2 header to come, expand as needed.
 292                          */
 293                         ret = xmit_check_hhlen(skb);
 294                         if (unlikely(ret))
 295                                 return ret;
 296
 297                         return LWTUNNEL_XMIT_CONTINUE;
 298                 case BPF_REDIRECT:
 299                         return LWTUNNEL_XMIT_DONE;
 300                 case BPF_LWT_REROUTE:
 301                         return bpf_lwt_xmit_reroute(skb);
 302                 default:
 303                         return ret;
 304                 }
 305         }
 306
 307         return LWTUNNEL_XMIT_CONTINUE;
 308 }
 309
 310 static void bpf_lwt_prog_destroy(struct bpf_lwt_prog *prog)
 311 {
 312         if (prog->prog)
 313                 bpf_prog_put(prog->prog);
 314
 315         kfree(prog->name);
 316 }
 317
 318 static void bpf_destroy_state(struct lwtunnel_state *lwt)
 319 {
 320         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 321
 322         bpf_lwt_prog_destroy(&bpf->in);
 323         bpf_lwt_prog_destroy(&bpf->out);
 324         bpf_lwt_prog_destroy(&bpf->xmit);
 325 }
 326
 327 static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = {
 328         [LWT_BPF_PROG_FD]   = { .type = NLA_U32, },
 329         [LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
 330                                 .len = MAX_PROG_NAME },
 331 };
 332
 333 static int bpf_parse_prog(struct nlattr *attr, struct bpf_lwt_prog *prog,
 334                           enum bpf_prog_type type)
 335 {
 336         struct nlattr *tb[LWT_BPF_PROG_MAX + 1];
 337         struct bpf_prog *p;
 338         int ret;
 339         u32 fd;
 340
 341         ret = nla_parse_nested_deprecated(tb, LWT_BPF_PROG_MAX, attr,
 342                                           bpf_prog_policy, NULL);
 343         if (ret < 0)
 344                 return ret;
 345
 346         if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME])
 347                 return -EINVAL;
 348
 349         prog->name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_ATOMIC);
 350         if (!prog->name)
 351                 return -ENOMEM;
 352
 353         fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
 354         p = bpf_prog_get_type(fd, type);
 355         if (IS_ERR(p))
 356                 return PTR_ERR(p);
 357
 358         prog->prog = p;
 359
 360         return 0;
 361 }
 362
 363 static const struct nla_policy bpf_nl_policy[LWT_BPF_MAX + 1] = {
 364         [LWT_BPF_IN]            = { .type = NLA_NESTED, },
 365         [LWT_BPF_OUT]           = { .type = NLA_NESTED, },
 366         [LWT_BPF_XMIT]          = { .type = NLA_NESTED, },
 367         [LWT_BPF_XMIT_HEADROOM] = { .type = NLA_U32 },
 368 };
 369
 370 static int bpf_build_state(struct net *net, struct nlattr *nla,
 371                            unsigned int family, const void *cfg,
 372                            struct lwtunnel_state **ts,
 373                            struct netlink_ext_ack *extack)
 374 {
 375         struct nlattr *tb[LWT_BPF_MAX + 1];
 376         struct lwtunnel_state *newts;
 377         struct bpf_lwt *bpf;
 378         int ret;
 379
 380         if (family != AF_INET && family != AF_INET6)
 381                 return -EAFNOSUPPORT;
 382
 383         ret = nla_parse_nested_deprecated(tb, LWT_BPF_MAX, nla, bpf_nl_policy,
 384                                           extack);
 385         if (ret < 0)
 386                 return ret;
 387
 388         if (!tb[LWT_BPF_IN] && !tb[LWT_BPF_OUT] && !tb[LWT_BPF_XMIT])
 389                 return -EINVAL;
 390
 391         newts = lwtunnel_state_alloc(sizeof(*bpf));
 392         if (!newts)
 393                 return -ENOMEM;
 394
 395         newts->type = LWTUNNEL_ENCAP_BPF;
 396         bpf = bpf_lwt_lwtunnel(newts);
 397
 398         if (tb[LWT_BPF_IN]) {
 399                 newts->flags |= LWTUNNEL_STATE_INPUT_REDIRECT;
 400                 ret = bpf_parse_prog(tb[LWT_BPF_IN], &bpf->in,
 401                                      BPF_PROG_TYPE_LWT_IN);
 402                 if (ret  < 0)
 403                         goto errout;
 404         }
 405
 406         if (tb[LWT_BPF_OUT]) {
 407                 newts->flags |= LWTUNNEL_STATE_OUTPUT_REDIRECT;
 408                 ret = bpf_parse_prog(tb[LWT_BPF_OUT], &bpf->out,
 409                                      BPF_PROG_TYPE_LWT_OUT);
 410                 if (ret < 0)
 411                         goto errout;
 412         }
 413
 414         if (tb[LWT_BPF_XMIT]) {
 415                 newts->flags |= LWTUNNEL_STATE_XMIT_REDIRECT;
 416                 ret = bpf_parse_prog(tb[LWT_BPF_XMIT], &bpf->xmit,
 417                                      BPF_PROG_TYPE_LWT_XMIT);
 418                 if (ret < 0)
 419                         goto errout;
 420         }
 421
 422         if (tb[LWT_BPF_XMIT_HEADROOM]) {
 423                 u32 headroom = nla_get_u32(tb[LWT_BPF_XMIT_HEADROOM]);
 424
 425                 if (headroom > LWT_BPF_MAX_HEADROOM) {
 426                         ret = -ERANGE;
 427                         goto errout;
 428                 }
 429
 430                 newts->headroom = headroom;
 431         }
 432
 433         bpf->family = family;
 434         *ts = newts;
 435
 436         return 0;
 437
 438 errout:
 439         bpf_destroy_state(newts);
 440         kfree(newts);
 441         return ret;
 442 }
 443
 444 static int bpf_fill_lwt_prog(struct sk_buff *skb, int attr,
 445                              struct bpf_lwt_prog *prog)
 446 {
 447         struct nlattr *nest;
 448
 449         if (!prog->prog)
 450                 return 0;
 451
 452         nest = nla_nest_start_noflag(skb, attr);
 453         if (!nest)
 454                 return -EMSGSIZE;
 455
 456         if (prog->name &&
 457             nla_put_string(skb, LWT_BPF_PROG_NAME, prog->name))
 458                 return -EMSGSIZE;
 459
 460         return nla_nest_end(skb, nest);
 461 }
 462
 463 static int bpf_fill_encap_info(struct sk_buff *skb, struct lwtunnel_state *lwt)
 464 {
 465         struct bpf_lwt *bpf = bpf_lwt_lwtunnel(lwt);
 466
 467         if (bpf_fill_lwt_prog(skb, LWT_BPF_IN, &bpf->in) < 0 ||
 468             bpf_fill_lwt_prog(skb, LWT_BPF_OUT, &bpf->out) < 0 ||
 469             bpf_fill_lwt_prog(skb, LWT_BPF_XMIT, &bpf->xmit) < 0)
 470                 return -EMSGSIZE;
 471
 472         return 0;
 473 }
 474
 475 static int bpf_encap_nlsize(struct lwtunnel_state *lwtstate)
 476 {
 477         int nest_len = nla_total_size(sizeof(struct nlattr)) +
 478                        nla_total_size(MAX_PROG_NAME) + /* LWT_BPF_PROG_NAME */
 479                        0;
 480
 481         return nest_len + /* LWT_BPF_IN */
 482                nest_len + /* LWT_BPF_OUT */
 483                nest_len + /* LWT_BPF_XMIT */
 484                0;
 485 }
 486
 487 static int bpf_lwt_prog_cmp(struct bpf_lwt_prog *a, struct bpf_lwt_prog *b)
 488 {
 489         /* FIXME:
 490          * The LWT state is currently rebuilt for delete requests which
 491          * results in a new bpf_prog instance. Comparing names for now.
 492          */
 493         if (!a->name && !b->name)
 494                 return 0;
 495
 496         if (!a->name || !b->name)
 497                 return 1;
 498
 499         return strcmp(a->name, b->name);
 500 }
 501
 502 static int bpf_encap_cmp(struct lwtunnel_state *a, struct lwtunnel_state *b)
 503 {
 504         struct bpf_lwt *a_bpf = bpf_lwt_lwtunnel(a);
 505         struct bpf_lwt *b_bpf = bpf_lwt_lwtunnel(b);
 506
 507         return bpf_lwt_prog_cmp(&a_bpf->in, &b_bpf->in) ||
 508                bpf_lwt_prog_cmp(&a_bpf->out, &b_bpf->out) ||
 509                bpf_lwt_prog_cmp(&a_bpf->xmit, &b_bpf->xmit);
 510 }
 511
 512 static const struct lwtunnel_encap_ops bpf_encap_ops = {
 513         .build_state    = bpf_build_state,
 514         .destroy_state  = bpf_destroy_state,
 515         .input          = bpf_input,
 516         .output         = bpf_output,
 517         .xmit           = bpf_xmit,
 518         .fill_encap     = bpf_fill_encap_info,
 519         .get_encap_size = bpf_encap_nlsize,
 520         .cmp_encap      = bpf_encap_cmp,
 521         .owner          = THIS_MODULE,
 522 };
 523
 524 static int handle_gso_type(struct sk_buff *skb, unsigned int gso_type,
 525                            int encap_len)
 526 {
 527         struct skb_shared_info *shinfo = skb_shinfo(skb);
 528
 529         gso_type |= SKB_GSO_DODGY;
 530         shinfo->gso_type |= gso_type;
 531         skb_decrease_gso_size(shinfo, encap_len);
 532         shinfo->gso_segs = 0;
 533         return 0;
 534 }
 535
 536 static int handle_gso_encap(struct sk_buff *skb, bool ipv4, int encap_len)
 537 {
 538         int next_hdr_offset;
 539         void *next_hdr;
 540         __u8 protocol;
 541
 542         /* SCTP and UDP_L4 gso need more nuanced handling than what
 543          * handle_gso_type() does above: skb_decrease_gso_size() is not enough.
 544          * So at the moment only TCP GSO packets are let through.
 545          */
 546         if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
 547                 return -ENOTSUPP;
 548
 549         if (ipv4) {
 550                 protocol = ip_hdr(skb)->protocol;
 551                 next_hdr_offset = sizeof(struct iphdr);
 552                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 553         } else {
 554                 protocol = ipv6_hdr(skb)->nexthdr;
 555                 next_hdr_offset = sizeof(struct ipv6hdr);
 556                 next_hdr = skb_network_header(skb) + next_hdr_offset;
 557         }
 558
 559         switch (protocol) {
 560         case IPPROTO_GRE:
 561                 next_hdr_offset += sizeof(struct gre_base_hdr);
 562                 if (next_hdr_offset > encap_len)
 563                         return -EINVAL;
 564
 565                 if (((struct gre_base_hdr *)next_hdr)->flags & GRE_CSUM)
 566                         return handle_gso_type(skb, SKB_GSO_GRE_CSUM,
 567                                                encap_len);
 568                 return handle_gso_type(skb, SKB_GSO_GRE, encap_len);
 569
 570         case IPPROTO_UDP:
 571                 next_hdr_offset += sizeof(struct udphdr);
 572                 if (next_hdr_offset > encap_len)
 573                         return -EINVAL;
 574
 575                 if (((struct udphdr *)next_hdr)->check)
 576                         return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL_CSUM,
 577                                                encap_len);
 578                 return handle_gso_type(skb, SKB_GSO_UDP_TUNNEL, encap_len);
 579
 580         case IPPROTO_IP:
 581         case IPPROTO_IPV6:
 582                 if (ipv4)
 583                         return handle_gso_type(skb, SKB_GSO_IPXIP4, encap_len);
 584                 else
 585                         return handle_gso_type(skb, SKB_GSO_IPXIP6, encap_len);
 586
 587         default:
 588                 return -EPROTONOSUPPORT;
 589         }
 590 }
 591
 592 int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len, bool ingress)
 593 {
 594         struct iphdr *iph;
 595         bool ipv4;
 596         int err;
 597
 598         if (unlikely(len < sizeof(struct iphdr) || len > LWT_BPF_MAX_HEADROOM))
 599                 return -EINVAL;
 600
 601         /* validate protocol and length */
 602         iph = (struct iphdr *)hdr;
 603         if (iph->version == 4) {
 604                 ipv4 = true;
 605                 if (unlikely(len < iph->ihl * 4))
 606                         return -EINVAL;
 607         } else if (iph->version == 6) {
 608                 ipv4 = false;
 609                 if (unlikely(len < sizeof(struct ipv6hdr)))
 610                         return -EINVAL;
 611         } else {
 612                 return -EINVAL;
 613         }
 614
 615         if (ingress)
 616                 err = skb_cow_head(skb, len + skb->mac_len);
 617         else
 618                 err = skb_cow_head(skb,
 619                                    len + LL_RESERVED_SPACE(skb_dst(skb)->dev));
 620         if (unlikely(err))
 621                 return err;
 622
 623         /* push the encap headers and fix pointers */
 624         skb_reset_inner_headers(skb);
 625         skb_reset_inner_mac_header(skb);  /* mac header is not yet set */
 626         skb_set_inner_protocol(skb, skb->protocol);
 627         skb->encapsulation = 1;
 628         skb_push(skb, len);
 629         if (ingress)
 630                 skb_postpush_rcsum(skb, iph, len);
 631         skb_reset_network_header(skb);
 632         memcpy(skb_network_header(skb), hdr, len);
 633         bpf_compute_data_pointers(skb);
 634         skb_clear_hash(skb);
 635
 636         if (ipv4) {
 637                 skb->protocol = htons(ETH_P_IP);
 638                 iph = ip_hdr(skb);
 639
 640                 if (!iph->check)
 641                         iph->check = ip_fast_csum((unsigned char *)iph,
 642                                                   iph->ihl);
 643         } else {
 644                 skb->protocol = htons(ETH_P_IPV6);
 645         }
 646
 647         if (skb_is_gso(skb))
 648                 return handle_gso_encap(skb, ipv4, len);
 649
 650         return 0;
 651 }
 652
 653 static int __init bpf_lwt_init(void)
 654 {
 655         return lwtunnel_encap_add_ops(&bpf_encap_ops, LWTUNNEL_ENCAP_BPF);
 656 }
 657
 658 subsys_initcall(bpf_lwt_init)