net/core/lwt_bpf.c

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