drivers/net/wireguard/receive.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
   4  */
   5
   6 #include "queueing.h"
   7 #include "device.h"
   8 #include "peer.h"
   9 #include "timers.h"
  10 #include "messages.h"
  11 #include "cookie.h"
  12 #include "socket.h"
  13
  14 #include <linux/ip.h>
  15 #include <linux/ipv6.h>
  16 #include <linux/udp.h>
  17 #include <net/ip_tunnels.h>
  18
  19 /* Must be called with bh disabled. */
  20 static void update_rx_stats(struct wg_peer *peer, size_t len)
  21 {
  22         struct pcpu_sw_netstats *tstats =
  23                 get_cpu_ptr(peer->device->dev->tstats);
  24
  25         u64_stats_update_begin(&tstats->syncp);
  26         ++tstats->rx_packets;
  27         tstats->rx_bytes += len;
  28         peer->rx_bytes += len;
  29         u64_stats_update_end(&tstats->syncp);
  30         put_cpu_ptr(tstats);
  31 }
  32
  33 #define SKB_TYPE_LE32(skb) (((struct message_header *)(skb)->data)->type)
  34
  35 static size_t validate_header_len(struct sk_buff *skb)
  36 {
  37         if (unlikely(skb->len < sizeof(struct message_header)))
  38                 return 0;
  39         if (SKB_TYPE_LE32(skb) == cpu_to_le32(MESSAGE_DATA) &&
  40             skb->len >= MESSAGE_MINIMUM_LENGTH)
  41                 return sizeof(struct message_data);
  42         if (SKB_TYPE_LE32(skb) == cpu_to_le32(MESSAGE_HANDSHAKE_INITIATION) &&
  43             skb->len == sizeof(struct message_handshake_initiation))
  44                 return sizeof(struct message_handshake_initiation);
  45         if (SKB_TYPE_LE32(skb) == cpu_to_le32(MESSAGE_HANDSHAKE_RESPONSE) &&
  46             skb->len == sizeof(struct message_handshake_response))
  47                 return sizeof(struct message_handshake_response);
  48         if (SKB_TYPE_LE32(skb) == cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE) &&
  49             skb->len == sizeof(struct message_handshake_cookie))
  50                 return sizeof(struct message_handshake_cookie);
  51         return 0;
  52 }
  53
  54 static int prepare_skb_header(struct sk_buff *skb, struct wg_device *wg)
  55 {
  56         size_t data_offset, data_len, header_len;
  57         struct udphdr *udp;
  58
  59         if (unlikely(!wg_check_packet_protocol(skb) ||
  60                      skb_transport_header(skb) < skb->head ||
  61                      (skb_transport_header(skb) + sizeof(struct udphdr)) >
  62                              skb_tail_pointer(skb)))
  63                 return -EINVAL; /* Bogus IP header */
  64         udp = udp_hdr(skb);
  65         data_offset = (u8 *)udp - skb->data;
  66         if (unlikely(data_offset > U16_MAX ||
  67                      data_offset + sizeof(struct udphdr) > skb->len))
  68                 /* Packet has offset at impossible location or isn't big enough
  69                  * to have UDP fields.
  70                  */
  71                 return -EINVAL;
  72         data_len = ntohs(udp->len);
  73         if (unlikely(data_len < sizeof(struct udphdr) ||
  74                      data_len > skb->len - data_offset))
  75                 /* UDP packet is reporting too small of a size or lying about
  76                  * its size.
  77                  */
  78                 return -EINVAL;
  79         data_len -= sizeof(struct udphdr);
  80         data_offset = (u8 *)udp + sizeof(struct udphdr) - skb->data;
  81         if (unlikely(!pskb_may_pull(skb,
  82                                 data_offset + sizeof(struct message_header)) ||
  83                      pskb_trim(skb, data_len + data_offset) < 0))
  84                 return -EINVAL;
  85         skb_pull(skb, data_offset);
  86         if (unlikely(skb->len != data_len))
  87                 /* Final len does not agree with calculated len */
  88                 return -EINVAL;
  89         header_len = validate_header_len(skb);
  90         if (unlikely(!header_len))
  91                 return -EINVAL;
  92         __skb_push(skb, data_offset);
  93         if (unlikely(!pskb_may_pull(skb, data_offset + header_len)))
  94                 return -EINVAL;
  95         __skb_pull(skb, data_offset);
  96         return 0;
  97 }
  98
  99 static void wg_receive_handshake_packet(struct wg_device *wg,
 100                                         struct sk_buff *skb)
 101 {
 102         enum cookie_mac_state mac_state;
 103         struct wg_peer *peer = NULL;
 104         /* This is global, so that our load calculation applies to the whole
 105          * system. We don't care about races with it at all.
 106          */
 107         static u64 last_under_load;
 108         bool packet_needs_cookie;
 109         bool under_load;
 110
 111         if (SKB_TYPE_LE32(skb) == cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE)) {
 112                 net_dbg_skb_ratelimited("%s: Receiving cookie response from %pISpfsc\n",
 113                                         wg->dev->name, skb);
 114                 wg_cookie_message_consume(
 115                         (struct message_handshake_cookie *)skb->data, wg);
 116                 return;
 117         }
 118
 119         under_load = skb_queue_len(&wg->incoming_handshakes) >=
 120                      MAX_QUEUED_INCOMING_HANDSHAKES / 8;
 121         if (under_load) {
 122                 last_under_load = ktime_get_coarse_boottime_ns();
 123         } else if (last_under_load) {
 124                 under_load = !wg_birthdate_has_expired(last_under_load, 1);
 125                 if (!under_load)
 126                         last_under_load = 0;
 127         }
 128         mac_state = wg_cookie_validate_packet(&wg->cookie_checker, skb,
 129                                               under_load);
 130         if ((under_load && mac_state == VALID_MAC_WITH_COOKIE) ||
 131             (!under_load && mac_state == VALID_MAC_BUT_NO_COOKIE)) {
 132                 packet_needs_cookie = false;
 133         } else if (under_load && mac_state == VALID_MAC_BUT_NO_COOKIE) {
 134                 packet_needs_cookie = true;
 135         } else {
 136                 net_dbg_skb_ratelimited("%s: Invalid MAC of handshake, dropping packet from %pISpfsc\n",
 137                                         wg->dev->name, skb);
 138                 return;
 139         }
 140
 141         switch (SKB_TYPE_LE32(skb)) {
 142         case cpu_to_le32(MESSAGE_HANDSHAKE_INITIATION): {
 143                 struct message_handshake_initiation *message =
 144                         (struct message_handshake_initiation *)skb->data;
 145
 146                 if (packet_needs_cookie) {
 147                         wg_packet_send_handshake_cookie(wg, skb,
 148                                                         message->sender_index);
 149                         return;
 150                 }
 151                 peer = wg_noise_handshake_consume_initiation(message, wg);
 152                 if (unlikely(!peer)) {
 153                         net_dbg_skb_ratelimited("%s: Invalid handshake initiation from %pISpfsc\n",
 154                                                 wg->dev->name, skb);
 155                         return;
 156                 }
 157                 wg_socket_set_peer_endpoint_from_skb(peer, skb);
 158                 net_dbg_ratelimited("%s: Receiving handshake initiation from peer %llu (%pISpfsc)\n",
 159                                     wg->dev->name, peer->internal_id,
 160                                     &peer->endpoint.addr);
 161                 wg_packet_send_handshake_response(peer);
 162                 break;
 163         }
 164         case cpu_to_le32(MESSAGE_HANDSHAKE_RESPONSE): {
 165                 struct message_handshake_response *message =
 166                         (struct message_handshake_response *)skb->data;
 167
 168                 if (packet_needs_cookie) {
 169                         wg_packet_send_handshake_cookie(wg, skb,
 170                                                         message->sender_index);
 171                         return;
 172                 }
 173                 peer = wg_noise_handshake_consume_response(message, wg);
 174                 if (unlikely(!peer)) {
 175                         net_dbg_skb_ratelimited("%s: Invalid handshake response from %pISpfsc\n",
 176                                                 wg->dev->name, skb);
 177                         return;
 178                 }
 179                 wg_socket_set_peer_endpoint_from_skb(peer, skb);
 180                 net_dbg_ratelimited("%s: Receiving handshake response from peer %llu (%pISpfsc)\n",
 181                                     wg->dev->name, peer->internal_id,
 182                                     &peer->endpoint.addr);
 183                 if (wg_noise_handshake_begin_session(&peer->handshake,
 184                                                      &peer->keypairs)) {
 185                         wg_timers_session_derived(peer);
 186                         wg_timers_handshake_complete(peer);
 187                         /* Calling this function will either send any existing
 188                          * packets in the queue and not send a keepalive, which
 189                          * is the best case, Or, if there's nothing in the
 190                          * queue, it will send a keepalive, in order to give
 191                          * immediate confirmation of the session.
 192                          */
 193                         wg_packet_send_keepalive(peer);
 194                 }
 195                 break;
 196         }
 197         }
 198
 199         if (unlikely(!peer)) {
 200                 WARN(1, "Somehow a wrong type of packet wound up in the handshake queue!\n");
 201                 return;
 202         }
 203
 204         local_bh_disable();
 205         update_rx_stats(peer, skb->len);
 206         local_bh_enable();
 207
 208         wg_timers_any_authenticated_packet_received(peer);
 209         wg_timers_any_authenticated_packet_traversal(peer);
 210         wg_peer_put(peer);
 211 }
 212
 213 void wg_packet_handshake_receive_worker(struct work_struct *work)
 214 {
 215         struct wg_device *wg = container_of(work, struct multicore_worker,
 216                                             work)->ptr;
 217         struct sk_buff *skb;
 218
 219         while ((skb = skb_dequeue(&wg->incoming_handshakes)) != NULL) {
 220                 wg_receive_handshake_packet(wg, skb);
 221                 dev_kfree_skb(skb);
 222                 cond_resched();
 223         }
 224 }
 225
 226 static void keep_key_fresh(struct wg_peer *peer)
 227 {
 228         struct noise_keypair *keypair;
 229         bool send;
 230
 231         if (peer->sent_lastminute_handshake)
 232                 return;
 233
 234         rcu_read_lock_bh();
 235         keypair = rcu_dereference_bh(peer->keypairs.current_keypair);
 236         send = keypair && READ_ONCE(keypair->sending.is_valid) &&
 237                keypair->i_am_the_initiator &&
 238                wg_birthdate_has_expired(keypair->sending.birthdate,
 239                         REJECT_AFTER_TIME - KEEPALIVE_TIMEOUT - REKEY_TIMEOUT);
 240         rcu_read_unlock_bh();
 241
 242         if (unlikely(send)) {
 243                 peer->sent_lastminute_handshake = true;
 244                 wg_packet_send_queued_handshake_initiation(peer, false);
 245         }
 246 }
 247
 248 static bool decrypt_packet(struct sk_buff *skb, struct noise_keypair *keypair)
 249 {
 250         struct scatterlist sg[MAX_SKB_FRAGS + 8];
 251         struct sk_buff *trailer;
 252         unsigned int offset;
 253         int num_frags;
 254
 255         if (unlikely(!keypair))
 256                 return false;
 257
 258         if (unlikely(!READ_ONCE(keypair->receiving.is_valid) ||
 259                   wg_birthdate_has_expired(keypair->receiving.birthdate, REJECT_AFTER_TIME) ||
 260                   keypair->receiving_counter.counter >= REJECT_AFTER_MESSAGES)) {
 261                 WRITE_ONCE(keypair->receiving.is_valid, false);
 262                 return false;
 263         }
 264
 265         PACKET_CB(skb)->nonce =
 266                 le64_to_cpu(((struct message_data *)skb->data)->counter);
 267
 268         /* We ensure that the network header is part of the packet before we
 269          * call skb_cow_data, so that there's no chance that data is removed
 270          * from the skb, so that later we can extract the original endpoint.
 271          */
 272         offset = skb->data - skb_network_header(skb);
 273         skb_push(skb, offset);
 274         num_frags = skb_cow_data(skb, 0, &trailer);
 275         offset += sizeof(struct message_data);
 276         skb_pull(skb, offset);
 277         if (unlikely(num_frags < 0 || num_frags > ARRAY_SIZE(sg)))
 278                 return false;
 279
 280         sg_init_table(sg, num_frags);
 281         if (skb_to_sgvec(skb, sg, 0, skb->len) <= 0)
 282                 return false;
 283
 284         if (!chacha20poly1305_decrypt_sg_inplace(sg, skb->len, NULL, 0,
 285                                                  PACKET_CB(skb)->nonce,
 286                                                  keypair->receiving.key))
 287                 return false;
 288
 289         /* Another ugly situation of pushing and pulling the header so as to
 290          * keep endpoint information intact.
 291          */
 292         skb_push(skb, offset);
 293         if (pskb_trim(skb, skb->len - noise_encrypted_len(0)))
 294                 return false;
 295         skb_pull(skb, offset);
 296
 297         return true;
 298 }
 299
 300 /* This is RFC6479, a replay detection bitmap algorithm that avoids bitshifts */
 301 static bool counter_validate(struct noise_replay_counter *counter, u64 their_counter)
 302 {
 303         unsigned long index, index_current, top, i;
 304         bool ret = false;
 305
 306         spin_lock_bh(&counter->lock);
 307
 308         if (unlikely(counter->counter >= REJECT_AFTER_MESSAGES + 1 ||
 309                      their_counter >= REJECT_AFTER_MESSAGES))
 310                 goto out;
 311
 312         ++their_counter;
 313
 314         if (unlikely((COUNTER_WINDOW_SIZE + their_counter) <
 315                      counter->counter))
 316                 goto out;
 317
 318         index = their_counter >> ilog2(BITS_PER_LONG);
 319
 320         if (likely(their_counter > counter->counter)) {
 321                 index_current = counter->counter >> ilog2(BITS_PER_LONG);
 322                 top = min_t(unsigned long, index - index_current,
 323                             COUNTER_BITS_TOTAL / BITS_PER_LONG);
 324                 for (i = 1; i <= top; ++i)
 325                         counter->backtrack[(i + index_current) &
 326                                 ((COUNTER_BITS_TOTAL / BITS_PER_LONG) - 1)] = 0;
 327                 counter->counter = their_counter;
 328         }
 329
 330         index &= (COUNTER_BITS_TOTAL / BITS_PER_LONG) - 1;
 331         ret = !test_and_set_bit(their_counter & (BITS_PER_LONG - 1),
 332                                 &counter->backtrack[index]);
 333
 334 out:
 335         spin_unlock_bh(&counter->lock);
 336         return ret;
 337 }
 338
 339 #include "selftest/counter.c"
 340
 341 static void wg_packet_consume_data_done(struct wg_peer *peer,
 342                                         struct sk_buff *skb,
 343                                         struct endpoint *endpoint)
 344 {
 345         struct net_device *dev = peer->device->dev;
 346         unsigned int len, len_before_trim;
 347         struct wg_peer *routed_peer;
 348
 349         wg_socket_set_peer_endpoint(peer, endpoint);
 350
 351         if (unlikely(wg_noise_received_with_keypair(&peer->keypairs,
 352                                                     PACKET_CB(skb)->keypair))) {
 353                 wg_timers_handshake_complete(peer);
 354                 wg_packet_send_staged_packets(peer);
 355         }
 356
 357         keep_key_fresh(peer);
 358
 359         wg_timers_any_authenticated_packet_received(peer);
 360         wg_timers_any_authenticated_packet_traversal(peer);
 361
 362         /* A packet with length 0 is a keepalive packet */
 363         if (unlikely(!skb->len)) {
 364                 update_rx_stats(peer, message_data_len(0));
 365                 net_dbg_ratelimited("%s: Receiving keepalive packet from peer %llu (%pISpfsc)\n",
 366                                     dev->name, peer->internal_id,
 367                                     &peer->endpoint.addr);
 368                 goto packet_processed;
 369         }
 370
 371         wg_timers_data_received(peer);
 372
 373         if (unlikely(skb_network_header(skb) < skb->head))
 374                 goto dishonest_packet_size;
 375         if (unlikely(!(pskb_network_may_pull(skb, sizeof(struct iphdr)) &&
 376                        (ip_hdr(skb)->version == 4 ||
 377                         (ip_hdr(skb)->version == 6 &&
 378                          pskb_network_may_pull(skb, sizeof(struct ipv6hdr)))))))
 379                 goto dishonest_packet_type;
 380
 381         skb->dev = dev;
 382         /* We've already verified the Poly1305 auth tag, which means this packet
 383          * was not modified in transit. We can therefore tell the networking
 384          * stack that all checksums of every layer of encapsulation have already
 385          * been checked "by the hardware" and therefore is unnecessary to check
 386          * again in software.
 387          */
 388         skb->ip_summed = CHECKSUM_UNNECESSARY;
 389         skb->csum_level = ~0; /* All levels */
 390         skb->protocol = ip_tunnel_parse_protocol(skb);
 391         if (skb->protocol == htons(ETH_P_IP)) {
 392                 len = ntohs(ip_hdr(skb)->tot_len);
 393                 if (unlikely(len < sizeof(struct iphdr)))
 394                         goto dishonest_packet_size;
 395                 INET_ECN_decapsulate(skb, PACKET_CB(skb)->ds, ip_hdr(skb)->tos);
 396         } else if (skb->protocol == htons(ETH_P_IPV6)) {
 397                 len = ntohs(ipv6_hdr(skb)->payload_len) +
 398                       sizeof(struct ipv6hdr);
 399                 INET_ECN_decapsulate(skb, PACKET_CB(skb)->ds, ipv6_get_dsfield(ipv6_hdr(skb)));
 400         } else {
 401                 goto dishonest_packet_type;
 402         }
 403
 404         if (unlikely(len > skb->len))
 405                 goto dishonest_packet_size;
 406         len_before_trim = skb->len;
 407         if (unlikely(pskb_trim(skb, len)))
 408                 goto packet_processed;
 409
 410         routed_peer = wg_allowedips_lookup_src(&peer->device->peer_allowedips,
 411                                                skb);
 412         wg_peer_put(routed_peer); /* We don't need the extra reference. */
 413
 414         if (unlikely(routed_peer != peer))
 415                 goto dishonest_packet_peer;
 416
 417         napi_gro_receive(&peer->napi, skb);
 418         update_rx_stats(peer, message_data_len(len_before_trim));
 419         return;
 420
 421 dishonest_packet_peer:
 422         net_dbg_skb_ratelimited("%s: Packet has unallowed src IP (%pISc) from peer %llu (%pISpfsc)\n",
 423                                 dev->name, skb, peer->internal_id,
 424                                 &peer->endpoint.addr);
 425         ++dev->stats.rx_errors;
 426         ++dev->stats.rx_frame_errors;
 427         goto packet_processed;
 428 dishonest_packet_type:
 429         net_dbg_ratelimited("%s: Packet is neither ipv4 nor ipv6 from peer %llu (%pISpfsc)\n",
 430                             dev->name, peer->internal_id, &peer->endpoint.addr);
 431         ++dev->stats.rx_errors;
 432         ++dev->stats.rx_frame_errors;
 433         goto packet_processed;
 434 dishonest_packet_size:
 435         net_dbg_ratelimited("%s: Packet has incorrect size from peer %llu (%pISpfsc)\n",
 436                             dev->name, peer->internal_id, &peer->endpoint.addr);
 437         ++dev->stats.rx_errors;
 438         ++dev->stats.rx_length_errors;
 439         goto packet_processed;
 440 packet_processed:
 441         dev_kfree_skb(skb);
 442 }
 443
 444 int wg_packet_rx_poll(struct napi_struct *napi, int budget)
 445 {
 446         struct wg_peer *peer = container_of(napi, struct wg_peer, napi);
 447         struct crypt_queue *queue = &peer->rx_queue;
 448         struct noise_keypair *keypair;
 449         struct endpoint endpoint;
 450         enum packet_state state;
 451         struct sk_buff *skb;
 452         int work_done = 0;
 453         bool free;
 454
 455         if (unlikely(budget <= 0))
 456                 return 0;
 457
 458         while ((skb = __ptr_ring_peek(&queue->ring)) != NULL &&
 459                (state = atomic_read_acquire(&PACKET_CB(skb)->state)) !=
 460                        PACKET_STATE_UNCRYPTED) {
 461                 __ptr_ring_discard_one(&queue->ring);
 462                 peer = PACKET_PEER(skb);
 463                 keypair = PACKET_CB(skb)->keypair;
 464                 free = true;
 465
 466                 if (unlikely(state != PACKET_STATE_CRYPTED))
 467                         goto next;
 468
 469                 if (unlikely(!counter_validate(&keypair->receiving_counter,
 470                                                PACKET_CB(skb)->nonce))) {
 471                         net_dbg_ratelimited("%s: Packet has invalid nonce %llu (max %llu)\n",
 472                                             peer->device->dev->name,
 473                                             PACKET_CB(skb)->nonce,
 474                                             keypair->receiving_counter.counter);
 475                         goto next;
 476                 }
 477
 478                 if (unlikely(wg_socket_endpoint_from_skb(&endpoint, skb)))
 479                         goto next;
 480
 481                 wg_reset_packet(skb, false);
 482                 wg_packet_consume_data_done(peer, skb, &endpoint);
 483                 free = false;
 484
 485 next:
 486                 wg_noise_keypair_put(keypair, false);
 487                 wg_peer_put(peer);
 488                 if (unlikely(free))
 489                         dev_kfree_skb(skb);
 490
 491                 if (++work_done >= budget)
 492                         break;
 493         }
 494
 495         if (work_done < budget)
 496                 napi_complete_done(napi, work_done);
 497
 498         return work_done;
 499 }
 500
 501 void wg_packet_decrypt_worker(struct work_struct *work)
 502 {
 503         struct crypt_queue *queue = container_of(work, struct multicore_worker,
 504                                                  work)->ptr;
 505         struct sk_buff *skb;
 506
 507         while ((skb = ptr_ring_consume_bh(&queue->ring)) != NULL) {
 508                 enum packet_state state =
 509                         likely(decrypt_packet(skb, PACKET_CB(skb)->keypair)) ?
 510                                 PACKET_STATE_CRYPTED : PACKET_STATE_DEAD;
 511                 wg_queue_enqueue_per_peer_napi(skb, state);
 512                 if (need_resched())
 513                         cond_resched();
 514         }
 515 }
 516
 517 static void wg_packet_consume_data(struct wg_device *wg, struct sk_buff *skb)
 518 {
 519         __le32 idx = ((struct message_data *)skb->data)->key_idx;
 520         struct wg_peer *peer = NULL;
 521         int ret;
 522
 523         rcu_read_lock_bh();
 524         PACKET_CB(skb)->keypair =
 525                 (struct noise_keypair *)wg_index_hashtable_lookup(
 526                         wg->index_hashtable, INDEX_HASHTABLE_KEYPAIR, idx,
 527                         &peer);
 528         if (unlikely(!wg_noise_keypair_get(PACKET_CB(skb)->keypair)))
 529                 goto err_keypair;
 530
 531         if (unlikely(READ_ONCE(peer->is_dead)))
 532                 goto err;
 533
 534         ret = wg_queue_enqueue_per_device_and_peer(&wg->decrypt_queue,
 535                                                    &peer->rx_queue, skb,
 536                                                    wg->packet_crypt_wq,
 537                                                    &wg->decrypt_queue.last_cpu);
 538         if (unlikely(ret == -EPIPE))
 539                 wg_queue_enqueue_per_peer_napi(skb, PACKET_STATE_DEAD);
 540         if (likely(!ret || ret == -EPIPE)) {
 541                 rcu_read_unlock_bh();
 542                 return;
 543         }
 544 err:
 545         wg_noise_keypair_put(PACKET_CB(skb)->keypair, false);
 546 err_keypair:
 547         rcu_read_unlock_bh();
 548         wg_peer_put(peer);
 549         dev_kfree_skb(skb);
 550 }
 551
 552 void wg_packet_receive(struct wg_device *wg, struct sk_buff *skb)
 553 {
 554         if (unlikely(prepare_skb_header(skb, wg) < 0))
 555                 goto err;
 556         switch (SKB_TYPE_LE32(skb)) {
 557         case cpu_to_le32(MESSAGE_HANDSHAKE_INITIATION):
 558         case cpu_to_le32(MESSAGE_HANDSHAKE_RESPONSE):
 559         case cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE): {
 560                 int cpu;
 561
 562                 if (skb_queue_len(&wg->incoming_handshakes) >
 563                             MAX_QUEUED_INCOMING_HANDSHAKES ||
 564                     unlikely(!rng_is_initialized())) {
 565                         net_dbg_skb_ratelimited("%s: Dropping handshake packet from %pISpfsc\n",
 566                                                 wg->dev->name, skb);
 567                         goto err;
 568                 }
 569                 skb_queue_tail(&wg->incoming_handshakes, skb);
 570                 /* Queues up a call to packet_process_queued_handshake_
 571                  * packets(skb):
 572                  */
 573                 cpu = wg_cpumask_next_online(&wg->incoming_handshake_cpu);
 574                 queue_work_on(cpu, wg->handshake_receive_wq,
 575                         &per_cpu_ptr(wg->incoming_handshakes_worker, cpu)->work);
 576                 break;
 577         }
 578         case cpu_to_le32(MESSAGE_DATA):
 579                 PACKET_CB(skb)->ds = ip_tunnel_get_dsfield(ip_hdr(skb), skb);
 580                 wg_packet_consume_data(wg, skb);
 581                 break;
 582         default:
 583                 WARN(1, "Non-exhaustive parsing of packet header lead to unknown packet type!\n");
 584                 goto err;
 585         }
 586         return;
 587
 588 err:
 589         dev_kfree_skb(skb);
 590 }