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_skb_examine_untrusted_ip_hdr(skb) != skb->protocol ||
  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 = false;
 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         if (likely(keypair && READ_ONCE(keypair->sending.is_valid)) &&
 237             keypair->i_am_the_initiator &&
 238             unlikely(wg_birthdate_has_expired(keypair->sending.birthdate,
 239                         REJECT_AFTER_TIME - KEEPALIVE_TIMEOUT - REKEY_TIMEOUT)))
 240                 send = true;
 241         rcu_read_unlock_bh();
 242
 243         if (send) {
 244                 peer->sent_lastminute_handshake = true;
 245                 wg_packet_send_queued_handshake_initiation(peer, false);
 246         }
 247 }
 248
 249 static bool decrypt_packet(struct sk_buff *skb, struct noise_symmetric_key *key)
 250 {
 251         struct scatterlist sg[MAX_SKB_FRAGS + 8];
 252         struct sk_buff *trailer;
 253         unsigned int offset;
 254         int num_frags;
 255
 256         if (unlikely(!key))
 257                 return false;
 258
 259         if (unlikely(!READ_ONCE(key->is_valid) ||
 260                   wg_birthdate_has_expired(key->birthdate, REJECT_AFTER_TIME) ||
 261                   key->counter.receive.counter >= REJECT_AFTER_MESSAGES)) {
 262                 WRITE_ONCE(key->is_valid, false);
 263                 return false;
 264         }
 265
 266         PACKET_CB(skb)->nonce =
 267                 le64_to_cpu(((struct message_data *)skb->data)->counter);
 268
 269         /* We ensure that the network header is part of the packet before we
 270          * call skb_cow_data, so that there's no chance that data is removed
 271          * from the skb, so that later we can extract the original endpoint.
 272          */
 273         offset = skb->data - skb_network_header(skb);
 274         skb_push(skb, offset);
 275         num_frags = skb_cow_data(skb, 0, &trailer);
 276         offset += sizeof(struct message_data);
 277         skb_pull(skb, offset);
 278         if (unlikely(num_frags < 0 || num_frags > ARRAY_SIZE(sg)))
 279                 return false;
 280
 281         sg_init_table(sg, num_frags);
 282         if (skb_to_sgvec(skb, sg, 0, skb->len) <= 0)
 283                 return false;
 284
 285         if (!chacha20poly1305_decrypt_sg_inplace(sg, skb->len, NULL, 0,
 286                                                  PACKET_CB(skb)->nonce,
 287                                                  key->key))
 288                 return false;
 289
 290         /* Another ugly situation of pushing and pulling the header so as to
 291          * keep endpoint information intact.
 292          */
 293         skb_push(skb, offset);
 294         if (pskb_trim(skb, skb->len - noise_encrypted_len(0)))
 295                 return false;
 296         skb_pull(skb, offset);
 297
 298         return true;
 299 }
 300
 301 /* This is RFC6479, a replay detection bitmap algorithm that avoids bitshifts */
 302 static bool counter_validate(union noise_counter *counter, u64 their_counter)
 303 {
 304         unsigned long index, index_current, top, i;
 305         bool ret = false;
 306
 307         spin_lock_bh(&counter->receive.lock);
 308
 309         if (unlikely(counter->receive.counter >= REJECT_AFTER_MESSAGES + 1 ||
 310                      their_counter >= REJECT_AFTER_MESSAGES))
 311                 goto out;
 312
 313         ++their_counter;
 314
 315         if (unlikely((COUNTER_WINDOW_SIZE + their_counter) <
 316                      counter->receive.counter))
 317                 goto out;
 318
 319         index = their_counter >> ilog2(BITS_PER_LONG);
 320
 321         if (likely(their_counter > counter->receive.counter)) {
 322                 index_current = counter->receive.counter >> ilog2(BITS_PER_LONG);
 323                 top = min_t(unsigned long, index - index_current,
 324                             COUNTER_BITS_TOTAL / BITS_PER_LONG);
 325                 for (i = 1; i <= top; ++i)
 326                         counter->receive.backtrack[(i + index_current) &
 327                                 ((COUNTER_BITS_TOTAL / BITS_PER_LONG) - 1)] = 0;
 328                 counter->receive.counter = their_counter;
 329         }
 330
 331         index &= (COUNTER_BITS_TOTAL / BITS_PER_LONG) - 1;
 332         ret = !test_and_set_bit(their_counter & (BITS_PER_LONG - 1),
 333                                 &counter->receive.backtrack[index]);
 334
 335 out:
 336         spin_unlock_bh(&counter->receive.lock);
 337         return ret;
 338 }
 339
 340 #include "selftest/counter.c"
 341
 342 static void wg_packet_consume_data_done(struct wg_peer *peer,
 343                                         struct sk_buff *skb,
 344                                         struct endpoint *endpoint)
 345 {
 346         struct net_device *dev = peer->device->dev;
 347         unsigned int len, len_before_trim;
 348         struct wg_peer *routed_peer;
 349
 350         wg_socket_set_peer_endpoint(peer, endpoint);
 351
 352         if (unlikely(wg_noise_received_with_keypair(&peer->keypairs,
 353                                                     PACKET_CB(skb)->keypair))) {
 354                 wg_timers_handshake_complete(peer);
 355                 wg_packet_send_staged_packets(peer);
 356         }
 357
 358         keep_key_fresh(peer);
 359
 360         wg_timers_any_authenticated_packet_received(peer);
 361         wg_timers_any_authenticated_packet_traversal(peer);
 362
 363         /* A packet with length 0 is a keepalive packet */
 364         if (unlikely(!skb->len)) {
 365                 update_rx_stats(peer, message_data_len(0));
 366                 net_dbg_ratelimited("%s: Receiving keepalive packet from peer %llu (%pISpfsc)\n",
 367                                     dev->name, peer->internal_id,
 368                                     &peer->endpoint.addr);
 369                 goto packet_processed;
 370         }
 371
 372         wg_timers_data_received(peer);
 373
 374         if (unlikely(skb_network_header(skb) < skb->head))
 375                 goto dishonest_packet_size;
 376         if (unlikely(!(pskb_network_may_pull(skb, sizeof(struct iphdr)) &&
 377                        (ip_hdr(skb)->version == 4 ||
 378                         (ip_hdr(skb)->version == 6 &&
 379                          pskb_network_may_pull(skb, sizeof(struct ipv6hdr)))))))
 380                 goto dishonest_packet_type;
 381
 382         skb->dev = dev;
 383         /* We've already verified the Poly1305 auth tag, which means this packet
 384          * was not modified in transit. We can therefore tell the networking
 385          * stack that all checksums of every layer of encapsulation have already
 386          * been checked "by the hardware" and therefore is unnecessary to check
 387          * again in software.
 388          */
 389         skb->ip_summed = CHECKSUM_UNNECESSARY;
 390         skb->csum_level = ~0; /* All levels */
 391         skb->protocol = wg_skb_examine_untrusted_ip_hdr(skb);
 392         if (skb->protocol == htons(ETH_P_IP)) {
 393                 len = ntohs(ip_hdr(skb)->tot_len);
 394                 if (unlikely(len < sizeof(struct iphdr)))
 395                         goto dishonest_packet_size;
 396                 if (INET_ECN_is_ce(PACKET_CB(skb)->ds))
 397                         IP_ECN_set_ce(ip_hdr(skb));
 398         } else if (skb->protocol == htons(ETH_P_IPV6)) {
 399                 len = ntohs(ipv6_hdr(skb)->payload_len) +
 400                       sizeof(struct ipv6hdr);
 401                 if (INET_ECN_is_ce(PACKET_CB(skb)->ds))
 402                         IP6_ECN_set_ce(skb, ipv6_hdr(skb));
 403         } else {
 404                 goto dishonest_packet_type;
 405         }
 406
 407         if (unlikely(len > skb->len))
 408                 goto dishonest_packet_size;
 409         len_before_trim = skb->len;
 410         if (unlikely(pskb_trim(skb, len)))
 411                 goto packet_processed;
 412
 413         routed_peer = wg_allowedips_lookup_src(&peer->device->peer_allowedips,
 414                                                skb);
 415         wg_peer_put(routed_peer); /* We don't need the extra reference. */
 416
 417         if (unlikely(routed_peer != peer))
 418                 goto dishonest_packet_peer;
 419
 420         if (unlikely(napi_gro_receive(&peer->napi, skb) == GRO_DROP)) {
 421                 ++dev->stats.rx_dropped;
 422                 net_dbg_ratelimited("%s: Failed to give packet to userspace from peer %llu (%pISpfsc)\n",
 423                                     dev->name, peer->internal_id,
 424                                     &peer->endpoint.addr);
 425         } else {
 426                 update_rx_stats(peer, message_data_len(len_before_trim));
 427         }
 428         return;
 429
 430 dishonest_packet_peer:
 431         net_dbg_skb_ratelimited("%s: Packet has unallowed src IP (%pISc) from peer %llu (%pISpfsc)\n",
 432                                 dev->name, skb, peer->internal_id,
 433                                 &peer->endpoint.addr);
 434         ++dev->stats.rx_errors;
 435         ++dev->stats.rx_frame_errors;
 436         goto packet_processed;
 437 dishonest_packet_type:
 438         net_dbg_ratelimited("%s: Packet is neither ipv4 nor ipv6 from peer %llu (%pISpfsc)\n",
 439                             dev->name, peer->internal_id, &peer->endpoint.addr);
 440         ++dev->stats.rx_errors;
 441         ++dev->stats.rx_frame_errors;
 442         goto packet_processed;
 443 dishonest_packet_size:
 444         net_dbg_ratelimited("%s: Packet has incorrect size from peer %llu (%pISpfsc)\n",
 445                             dev->name, peer->internal_id, &peer->endpoint.addr);
 446         ++dev->stats.rx_errors;
 447         ++dev->stats.rx_length_errors;
 448         goto packet_processed;
 449 packet_processed:
 450         dev_kfree_skb(skb);
 451 }
 452
 453 int wg_packet_rx_poll(struct napi_struct *napi, int budget)
 454 {
 455         struct wg_peer *peer = container_of(napi, struct wg_peer, napi);
 456         struct crypt_queue *queue = &peer->rx_queue;
 457         struct noise_keypair *keypair;
 458         struct endpoint endpoint;
 459         enum packet_state state;
 460         struct sk_buff *skb;
 461         int work_done = 0;
 462         bool free;
 463
 464         if (unlikely(budget <= 0))
 465                 return 0;
 466
 467         while ((skb = __ptr_ring_peek(&queue->ring)) != NULL &&
 468                (state = atomic_read_acquire(&PACKET_CB(skb)->state)) !=
 469                        PACKET_STATE_UNCRYPTED) {
 470                 __ptr_ring_discard_one(&queue->ring);
 471                 peer = PACKET_PEER(skb);
 472                 keypair = PACKET_CB(skb)->keypair;
 473                 free = true;
 474
 475                 if (unlikely(state != PACKET_STATE_CRYPTED))
 476                         goto next;
 477
 478                 if (unlikely(!counter_validate(&keypair->receiving.counter,
 479                                                PACKET_CB(skb)->nonce))) {
 480                         net_dbg_ratelimited("%s: Packet has invalid nonce %llu (max %llu)\n",
 481                                             peer->device->dev->name,
 482                                             PACKET_CB(skb)->nonce,
 483                                             keypair->receiving.counter.receive.counter);
 484                         goto next;
 485                 }
 486
 487                 if (unlikely(wg_socket_endpoint_from_skb(&endpoint, skb)))
 488                         goto next;
 489
 490                 wg_reset_packet(skb);
 491                 wg_packet_consume_data_done(peer, skb, &endpoint);
 492                 free = false;
 493
 494 next:
 495                 wg_noise_keypair_put(keypair, false);
 496                 wg_peer_put(peer);
 497                 if (unlikely(free))
 498                         dev_kfree_skb(skb);
 499
 500                 if (++work_done >= budget)
 501                         break;
 502         }
 503
 504         if (work_done < budget)
 505                 napi_complete_done(napi, work_done);
 506
 507         return work_done;
 508 }
 509
 510 void wg_packet_decrypt_worker(struct work_struct *work)
 511 {
 512         struct crypt_queue *queue = container_of(work, struct multicore_worker,
 513                                                  work)->ptr;
 514         struct sk_buff *skb;
 515
 516         while ((skb = ptr_ring_consume_bh(&queue->ring)) != NULL) {
 517                 enum packet_state state = likely(decrypt_packet(skb,
 518                                 &PACKET_CB(skb)->keypair->receiving)) ?
 519                                 PACKET_STATE_CRYPTED : PACKET_STATE_DEAD;
 520                 wg_queue_enqueue_per_peer_napi(skb, state);
 521         }
 522 }
 523
 524 static void wg_packet_consume_data(struct wg_device *wg, struct sk_buff *skb)
 525 {
 526         __le32 idx = ((struct message_data *)skb->data)->key_idx;
 527         struct wg_peer *peer = NULL;
 528         int ret;
 529
 530         rcu_read_lock_bh();
 531         PACKET_CB(skb)->keypair =
 532                 (struct noise_keypair *)wg_index_hashtable_lookup(
 533                         wg->index_hashtable, INDEX_HASHTABLE_KEYPAIR, idx,
 534                         &peer);
 535         if (unlikely(!wg_noise_keypair_get(PACKET_CB(skb)->keypair)))
 536                 goto err_keypair;
 537
 538         if (unlikely(READ_ONCE(peer->is_dead)))
 539                 goto err;
 540
 541         ret = wg_queue_enqueue_per_device_and_peer(&wg->decrypt_queue,
 542                                                    &peer->rx_queue, skb,
 543                                                    wg->packet_crypt_wq,
 544                                                    &wg->decrypt_queue.last_cpu);
 545         if (unlikely(ret == -EPIPE))
 546                 wg_queue_enqueue_per_peer_napi(skb, PACKET_STATE_DEAD);
 547         if (likely(!ret || ret == -EPIPE)) {
 548                 rcu_read_unlock_bh();
 549                 return;
 550         }
 551 err:
 552         wg_noise_keypair_put(PACKET_CB(skb)->keypair, false);
 553 err_keypair:
 554         rcu_read_unlock_bh();
 555         wg_peer_put(peer);
 556         dev_kfree_skb(skb);
 557 }
 558
 559 void wg_packet_receive(struct wg_device *wg, struct sk_buff *skb)
 560 {
 561         if (unlikely(prepare_skb_header(skb, wg) < 0))
 562                 goto err;
 563         switch (SKB_TYPE_LE32(skb)) {
 564         case cpu_to_le32(MESSAGE_HANDSHAKE_INITIATION):
 565         case cpu_to_le32(MESSAGE_HANDSHAKE_RESPONSE):
 566         case cpu_to_le32(MESSAGE_HANDSHAKE_COOKIE): {
 567                 int cpu;
 568
 569                 if (skb_queue_len(&wg->incoming_handshakes) >
 570                             MAX_QUEUED_INCOMING_HANDSHAKES ||
 571                     unlikely(!rng_is_initialized())) {
 572                         net_dbg_skb_ratelimited("%s: Dropping handshake packet from %pISpfsc\n",
 573                                                 wg->dev->name, skb);
 574                         goto err;
 575                 }
 576                 skb_queue_tail(&wg->incoming_handshakes, skb);
 577                 /* Queues up a call to packet_process_queued_handshake_
 578                  * packets(skb):
 579                  */
 580                 cpu = wg_cpumask_next_online(&wg->incoming_handshake_cpu);
 581                 queue_work_on(cpu, wg->handshake_receive_wq,
 582                         &per_cpu_ptr(wg->incoming_handshakes_worker, cpu)->work);
 583                 break;
 584         }
 585         case cpu_to_le32(MESSAGE_DATA):
 586                 PACKET_CB(skb)->ds = ip_tunnel_get_dsfield(ip_hdr(skb), skb);
 587                 wg_packet_consume_data(wg, skb);
 588                 break;
 589         default:
 590                 net_dbg_skb_ratelimited("%s: Invalid packet from %pISpfsc\n",
 591                                         wg->dev->name, skb);
 592                 goto err;
 593         }
 594         return;
 595
 596 err:
 597         dev_kfree_skb(skb);
 598 }