// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
#include "peer.h"
#include "device.h"
#include "queueing.h"
#include "timers.h"
#include "peerlookup.h"
#include "noise.h"
#include <linux/kref.h>
#include <linux/lockdep.h>
#include <linux/rcupdate.h>
#include <linux/list.h>
static atomic64_t peer_counter = ATOMIC64_INIT(0);
struct wg_peer *wg_peer_create(struct wg_device *wg,
const u8 public_key[NOISE_PUBLIC_KEY_LEN],
const u8 preshared_key[NOISE_SYMMETRIC_KEY_LEN])
{
struct wg_peer *peer;
int ret = -ENOMEM;
lockdep_assert_held(&wg->device_update_lock);
if (wg->num_peers >= MAX_PEERS_PER_DEVICE)
return ERR_PTR(ret);
peer = kzalloc(sizeof(*peer), GFP_KERNEL);
if (unlikely(!peer))
return ERR_PTR(ret);
peer->device = wg;
wg_noise_handshake_init(&peer->handshake, &wg->static_identity,
public_key, preshared_key, peer);
if (dst_cache_init(&peer->endpoint_cache, GFP_KERNEL))
goto err_1;
if (wg_packet_queue_init(&peer->tx_queue, wg_packet_tx_worker, false,
MAX_QUEUED_PACKETS))
goto err_2;
if (wg_packet_queue_init(&peer->rx_queue, NULL, false,
MAX_QUEUED_PACKETS))
goto err_3;
peer->internal_id = atomic64_inc_return(&peer_counter);
peer->serial_work_cpu = nr_cpumask_bits;
wg_cookie_init(&peer->latest_cookie);
wg_timers_init(peer);
wg_cookie_checker_precompute_peer_keys(peer);
spin_lock_init(&peer->keypairs.keypair_update_lock);
INIT_WORK(&peer->transmit_handshake_work,
wg_packet_handshake_send_worker);
rwlock_init(&peer->endpoint_lock);
kref_init(&peer->refcount);
skb_queue_head_init(&peer->staged_packet_queue);
wg_noise_reset_last_sent_handshake(&peer->last_sent_handshake);
set_bit(NAPI_STATE_NO_BUSY_POLL, &peer->napi.state);
netif_napi_add(wg->dev, &peer->napi, wg_packet_rx_poll,
NAPI_POLL_WEIGHT);
napi_enable(&peer->napi);
list_add_tail(&peer->peer_list, &wg->peer_list);
INIT_LIST_HEAD(&peer->allowedips_list);
wg_pubkey_hashtable_add(wg->peer_hashtable, peer);
++wg->num_peers;
pr_debug("%s: Peer %llu created\n", wg->dev->name, peer->internal_id);
return peer;
err_3:
wg_packet_queue_free(&peer->tx_queue, false);
err_2:
dst_cache_destroy(&peer->endpoint_cache);
err_1:
kfree(peer);
return ERR_PTR(ret);
}
struct wg_peer *wg_peer_get_maybe_zero(struct wg_peer *peer)
{
RCU_LOCKDEP_WARN(!rcu_read_lock_bh_held(),
"Taking peer reference without holding the RCU read lock");
if (unlikely(!peer || !kref_get_unless_zero(&peer->refcount)))
return NULL;
return peer;
}
static void peer_make_dead(struct wg_peer *peer)
{
/* Remove from configuration-time lookup structures. */
list_del_init(&peer->peer_list);
wg_allowedips_remove_by_peer(&peer->device->peer_allowedips, peer,
&peer->device->device_update_lock);
wg_pubkey_hashtable_remove(peer->device->peer_hashtable, peer);
/* Mark as dead, so that we don't allow jumping contexts after. */
WRITE_ONCE(peer->is_dead, true);
/* The caller must now synchronize_rcu() for this to take effect. */
}
static void peer_remove_after_dead(struct wg_peer *peer)
{
WARN_ON(!peer->is_dead);
/* No more keypairs can be created for this peer, since is_dead protects
* add_new_keypair, so we can now destroy existing ones.
*/
wg_noise_keypairs_clear(&peer->keypairs);
/* Destroy all ongoing timers that were in-flight at the beginning of
* this function.
*/
wg_timers_stop(peer);
/* The transition between packet encryption/decryption queues isn't
* guarded by is_dead, but each reference's life is strictly bounded by
* two generations: once for parallel crypto and once for serial
* ingestion, so we can simply flush twice, and be sure that we no
* longer have references inside these queues.
*/
/* a) For encrypt/decrypt. */
flush_workqueue(peer->device->packet_crypt_wq);
/* b.1) For send (but not receive, since that's napi). */
flush_workqueue(peer->device->packet_crypt_wq);
/* b.2.1) For receive (but not send, since that's wq). */
napi_disable(&peer->napi);
/* b.2.1) It's now safe to remove the napi struct, which must be done
* here from process context.
*/
netif_napi_del(&peer->napi);
/* Ensure any workstructs we own (like transmit_handshake_work or
* clear_peer_work) no longer are in use.
*/
flush_workqueue(peer->device->handshake_send_wq);
/* After the above flushes, a peer might still be active in a few
* different contexts: 1) from xmit(), before hitting is_dead and
* returning, 2) from wg_packet_consume_data(), before hitting is_dead
* and returning, 3) from wg_receive_handshake_packet() after a point
* where it has processed an incoming handshake packet, but where
* all calls to pass it off to timers fails because of is_dead. We won't
* have new references in (1) eventually, because we're removed from
* allowedips; we won't have new references in (2) eventually, because
* wg_index_hashtable_lookup will always return NULL, since we removed
* all existing keypairs and no more can be created; we won't have new
* references in (3) eventually, because we're removed from the pubkey
* hash table, which allows for a maximum of one handshake response,
* via the still-uncleared index hashtable entry, but not more than one,
* and in wg_cookie_message_consume, the lookup eventually gets a peer
* with a refcount of zero, so no new reference is taken.
*/
--peer->device->num_peers;
wg_peer_put(peer);
}
/* We have a separate "remove" function make sure that all active places where
* a peer is currently operating will eventually come to an end and not pass
* their reference onto another context.
*/
void wg_peer_remove(struct wg_peer *peer)
{
if (unlikely(!peer))
return;
lockdep_assert_held(&peer->device->device_update_lock);
peer_make_dead(peer);
synchronize_rcu();
peer_remove_after_dead(peer);
}
void wg_peer_remove_all(struct wg_device *wg)
{
struct wg_peer *peer, *temp;
LIST_HEAD(dead_peers);
lockdep_assert_held(&wg->device_update_lock);
/* Avoid having to traverse individually for each one. */
wg_allowedips_free(&wg->peer_allowedips, &wg->device_update_lock);
list_for_each_entry_safe(peer, temp, &wg->peer_list, peer_list) {
peer_make_dead(peer);
list_add_tail(&peer->peer_list, &dead_peers);
}
synchronize_rcu();
list_for_each_entry_safe(peer, temp, &dead_peers, peer_list)
peer_remove_after_dead(peer);
}
static void rcu_release(struct rcu_head *rcu)
{
struct wg_peer *peer = container_of(rcu, struct wg_peer, rcu);
dst_cache_destroy(&peer->endpoint_cache);
wg_packet_queue_free(&peer->rx_queue, false);
wg_packet_queue_free(&peer->tx_queue, false);
/* The final zeroing takes care of clearing any remaining handshake key
* material and other potentially sensitive information.
*/
kfree_sensitive(peer);
}
static void kref_release(struct kref *refcount)
{
struct wg_peer *peer = container_of(refcount, struct wg_peer, refcount);
pr_debug("%s: Peer %llu (%pISpfsc) destroyed\n",
peer->device->dev->name, peer->internal_id,
&peer->endpoint.addr);
/* Remove ourself from dynamic runtime lookup structures, now that the
* last reference is gone.
*/
wg_index_hashtable_remove(peer->device->index_hashtable,
&peer->handshake.entry);
/* Remove any lingering packets that didn't have a chance to be
* transmitted.
*/
wg_packet_purge_staged_packets(peer);
/* Free the memory used. */
call_rcu(&peer->rcu, rcu_release);
}
void wg_peer_put(struct wg_peer *peer)
{
if (unlikely(!peer))
return;
kref_put(&peer->refcount, kref_release);
}
