OpenVPN supports configuring a periodic keepalive packet. message to allow the remote endpoint detect link failures.
This change implements the keepalive sending and timer expiring logic.
Signed-off-by: Antonio Quartulli antonio@openvpn.net --- drivers/net/ovpn/io.c | 78 ++++++++++++++++- drivers/net/ovpn/io.h | 5 ++ drivers/net/ovpn/main.c | 3 + drivers/net/ovpn/ovpnpriv.h | 2 + drivers/net/ovpn/peer.c | 205 ++++++++++++++++++++++++++++++++++++++++++++ drivers/net/ovpn/peer.h | 21 ++++- 6 files changed, 311 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c index 9833d711070a4b476a02a96a6ad56030485c2048..680c7692b09b61247da3817c18d80ddfdc2814a4 100644 --- a/drivers/net/ovpn/io.c +++ b/drivers/net/ovpn/io.c @@ -27,6 +27,33 @@ #include "skb.h" #include "socket.h"
+const unsigned char ovpn_keepalive_message[OVPN_KEEPALIVE_SIZE] = { + 0x2a, 0x18, 0x7b, 0xf3, 0x64, 0x1e, 0xb4, 0xcb, + 0x07, 0xed, 0x2d, 0x0a, 0x98, 0x1f, 0xc7, 0x48 +}; + +/** + * ovpn_is_keepalive - check if skb contains a keepalive message + * @skb: packet to check + * + * Assumes that the first byte of skb->data is defined. + * + * Return: true if skb contains a keepalive or false otherwise + */ +static bool ovpn_is_keepalive(struct sk_buff *skb) +{ + if (*skb->data != ovpn_keepalive_message[0]) + return false; + + if (skb->len != OVPN_KEEPALIVE_SIZE) + return false; + + if (!pskb_may_pull(skb, OVPN_KEEPALIVE_SIZE)) + return false; + + return !memcmp(skb->data, ovpn_keepalive_message, OVPN_KEEPALIVE_SIZE); +} + /* Called after decrypt to write the IP packet to the device. * This method is expected to manage/free the skb. */ @@ -101,6 +128,9 @@ void ovpn_decrypt_post(void *data, int ret) goto drop; }
+ /* keep track of last received authenticated packet for keepalive */ + WRITE_ONCE(peer->last_recv, ktime_get_real_seconds()); + /* point to encapsulated IP packet */ __skb_pull(skb, payload_offset);
@@ -118,6 +148,15 @@ void ovpn_decrypt_post(void *data, int ret) goto drop; }
+ if (ovpn_is_keepalive(skb)) { + net_dbg_ratelimited("%s: ping received from peer %u\n", + netdev_name(peer->ovpn->dev), + peer->id); + /* we drop the packet, but this is not a failure */ + consume_skb(skb); + goto drop_nocount; + } + net_info_ratelimited("%s: unsupported protocol received from peer %u\n", netdev_name(peer->ovpn->dev), peer->id); goto drop; @@ -143,11 +182,12 @@ void ovpn_decrypt_post(void *data, int ret) drop: if (unlikely(skb)) dev_core_stats_rx_dropped_inc(peer->ovpn->dev); + kfree_skb(skb); +drop_nocount: if (likely(peer)) ovpn_peer_put(peer); if (likely(ks)) ovpn_crypto_key_slot_put(ks); - kfree_skb(skb); }
/* RX path entry point: decrypt packet and forward it to the device */ @@ -221,6 +261,8 @@ void ovpn_encrypt_post(void *data, int ret) }
ovpn_peer_stats_increment_tx(&peer->link_stats, orig_len); + /* keep track of last sent packet for keepalive */ + WRITE_ONCE(peer->last_sent, ktime_get_real_seconds()); /* skb passed down the stack - don't free it */ skb = NULL; err_unlock: @@ -346,3 +388,37 @@ netdev_tx_t ovpn_net_xmit(struct sk_buff *skb, struct net_device *dev) kfree_skb_list(skb); return NET_XMIT_DROP; } + +/** + * ovpn_xmit_special - encrypt and transmit an out-of-band message to peer + * @peer: peer to send the message to + * @data: message content + * @len: message length + * + * Assumes that caller holds a reference to peer, which will be + * passed to ovpn_send() + */ +void ovpn_xmit_special(struct ovpn_peer *peer, const void *data, + const unsigned int len) +{ + struct ovpn_priv *ovpn; + struct sk_buff *skb; + + ovpn = peer->ovpn; + if (unlikely(!ovpn)) { + ovpn_peer_put(peer); + return; + } + + skb = alloc_skb(256 + len, GFP_ATOMIC); + if (unlikely(!skb)) { + ovpn_peer_put(peer); + return; + } + + skb_reserve(skb, 128); + skb->priority = TC_PRIO_BESTEFFORT; + __skb_put_data(skb, data, len); + + ovpn_send(ovpn, skb, peer); +} diff --git a/drivers/net/ovpn/io.h b/drivers/net/ovpn/io.h index 5143104b2c4b896a030ec4a8c8aea7015f40ef02..db9e10f9077c4738ee79e5723e2a4bf5ef72f633 100644 --- a/drivers/net/ovpn/io.h +++ b/drivers/net/ovpn/io.h @@ -19,9 +19,14 @@ /* max padding required by encryption */ #define OVPN_MAX_PADDING 16
+#define OVPN_KEEPALIVE_SIZE 16 +extern const unsigned char ovpn_keepalive_message[OVPN_KEEPALIVE_SIZE]; + netdev_tx_t ovpn_net_xmit(struct sk_buff *skb, struct net_device *dev);
void ovpn_recv(struct ovpn_peer *peer, struct sk_buff *skb); +void ovpn_xmit_special(struct ovpn_peer *peer, const void *data, + const unsigned int len);
void ovpn_encrypt_post(void *data, int ret); void ovpn_decrypt_post(void *data, int ret); diff --git a/drivers/net/ovpn/main.c b/drivers/net/ovpn/main.c index 1b3d5b6c839999202743a15f38029251bf102f45..0e016d39c95e52515437313064e892aa3038adad 100644 --- a/drivers/net/ovpn/main.c +++ b/drivers/net/ovpn/main.c @@ -185,6 +185,7 @@ static int ovpn_newlink(struct net_device *dev, ovpn->dev = dev; ovpn->mode = mode; spin_lock_init(&ovpn->lock); + INIT_DELAYED_WORK(&ovpn->keepalive_work, ovpn_peer_keepalive_work);
/* turn carrier explicitly off after registration, this way state is * clearly defined @@ -244,6 +245,8 @@ static int ovpn_netdev_notifier_call(struct notifier_block *nb,
netif_carrier_off(dev); ovpn->registered = false; + + cancel_delayed_work_sync(&ovpn->keepalive_work); ovpn_peers_free(ovpn, NULL, OVPN_DEL_PEER_REASON_TEARDOWN); break; case NETDEV_POST_INIT: diff --git a/drivers/net/ovpn/ovpnpriv.h b/drivers/net/ovpn/ovpnpriv.h index b26ad97215a3d42242ba349b348c2749f570797c..5403cdc99a67ca91604d1c3cefdea76dca83a44a 100644 --- a/drivers/net/ovpn/ovpnpriv.h +++ b/drivers/net/ovpn/ovpnpriv.h @@ -41,6 +41,7 @@ struct ovpn_peer_collection { * @peers: data structures holding multi-peer references * @peer: in P2P mode, this is the only remote peer * @gro_cells: pointer to the Generic Receive Offload cell + * @keepalive_work: struct used to schedule keepalive periodic job */ struct ovpn_priv { struct net_device *dev; @@ -50,6 +51,7 @@ struct ovpn_priv { struct ovpn_peer_collection *peers; struct ovpn_peer __rcu *peer; struct gro_cells gro_cells; + struct delayed_work keepalive_work; };
#endif /* _NET_OVPN_OVPNSTRUCT_H_ */ diff --git a/drivers/net/ovpn/peer.c b/drivers/net/ovpn/peer.c index 2d6cecc28c5d1f7d5516f7f89bc0ba274c72d5e1..45e87ac155b554044388490a403f64c777d283a6 100644 --- a/drivers/net/ovpn/peer.c +++ b/drivers/net/ovpn/peer.c @@ -36,6 +36,52 @@ static void unlock_ovpn(struct ovpn_priv *ovpn, } }
+/** + * ovpn_peer_keepalive_set - configure keepalive values for peer + * @peer: the peer to configure + * @interval: outgoing keepalive interval + * @timeout: incoming keepalive timeout + */ +void ovpn_peer_keepalive_set(struct ovpn_peer *peer, u32 interval, u32 timeout) +{ + time64_t now = ktime_get_real_seconds(); + + netdev_dbg(peer->ovpn->dev, + "scheduling keepalive for peer %u: interval=%u timeout=%u\n", + peer->id, interval, timeout); + + peer->keepalive_interval = interval; + WRITE_ONCE(peer->last_sent, now); + peer->keepalive_xmit_exp = now + interval; + + peer->keepalive_timeout = timeout; + WRITE_ONCE(peer->last_recv, now); + peer->keepalive_recv_exp = now + timeout; + + /* now that interval and timeout have been changed, kick + * off the worker so that the next delay can be recomputed + */ + mod_delayed_work(system_wq, &peer->ovpn->keepalive_work, 0); +} + +/** + * ovpn_peer_keepalive_send - periodic worker sending keepalive packets + * @work: pointer to the work member of the related peer object + * + * NOTE: the reference to peer is not dropped because it gets inherited + * by ovpn_xmit_special() + */ +static void ovpn_peer_keepalive_send(struct work_struct *work) +{ + struct ovpn_peer *peer = container_of(work, struct ovpn_peer, + keepalive_work); + + local_bh_disable(); + ovpn_xmit_special(peer, ovpn_keepalive_message, + sizeof(ovpn_keepalive_message)); + local_bh_enable(); +} + /** * ovpn_peer_new - allocate and initialize a new peer object * @ovpn: the openvpn instance inside which the peer should be created @@ -65,6 +111,7 @@ struct ovpn_peer *ovpn_peer_new(struct ovpn_priv *ovpn, u32 id) kref_init(&peer->refcount); ovpn_peer_stats_init(&peer->vpn_stats); ovpn_peer_stats_init(&peer->link_stats); + INIT_WORK(&peer->keepalive_work, ovpn_peer_keepalive_send);
ret = dst_cache_init(&peer->dst_cache, GFP_KERNEL); if (ret < 0) { @@ -948,3 +995,161 @@ void ovpn_peers_free(struct ovpn_priv *ovpn, struct sock *sk, break; } } + +static time64_t ovpn_peer_keepalive_work_single(struct ovpn_peer *peer, + time64_t now, + struct llist_head *release_list) +{ + time64_t last_recv, last_sent, next_run1, next_run2; + unsigned long timeout, interval; + bool expired; + + spin_lock_bh(&peer->lock); + /* we expect both timers to be configured at the same time, + * therefore bail out if either is not set + */ + if (!peer->keepalive_timeout || !peer->keepalive_interval) { + spin_unlock_bh(&peer->lock); + return 0; + } + + /* check for peer timeout */ + expired = false; + timeout = peer->keepalive_timeout; + last_recv = READ_ONCE(peer->last_recv); + if (now < last_recv + timeout) { + peer->keepalive_recv_exp = last_recv + timeout; + next_run1 = peer->keepalive_recv_exp; + } else if (peer->keepalive_recv_exp > now) { + next_run1 = peer->keepalive_recv_exp; + } else { + expired = true; + } + + if (expired) { + /* peer is dead -> kill it and move on */ + spin_unlock_bh(&peer->lock); + netdev_dbg(peer->ovpn->dev, "peer %u expired\n", + peer->id); + ovpn_peer_remove(peer, OVPN_DEL_PEER_REASON_EXPIRED, + release_list); + return 0; + } + + /* check for peer keepalive */ + expired = false; + interval = peer->keepalive_interval; + last_sent = READ_ONCE(peer->last_sent); + if (now < last_sent + interval) { + peer->keepalive_xmit_exp = last_sent + interval; + next_run2 = peer->keepalive_xmit_exp; + } else if (peer->keepalive_xmit_exp > now) { + next_run2 = peer->keepalive_xmit_exp; + } else { + expired = true; + next_run2 = now + interval; + } + spin_unlock_bh(&peer->lock); + + if (expired) { + /* a keepalive packet is required */ + netdev_dbg(peer->ovpn->dev, + "sending keepalive to peer %u\n", + peer->id); + if (schedule_work(&peer->keepalive_work)) + ovpn_peer_hold(peer); + } + + if (next_run1 < next_run2) + return next_run1; + + return next_run2; +} + +static time64_t ovpn_peer_keepalive_work_mp(struct ovpn_priv *ovpn, + time64_t now, + struct llist_head *release_list) +{ + time64_t tmp_next_run, next_run = 0; + struct hlist_node *tmp; + struct ovpn_peer *peer; + int bkt; + + lockdep_assert_held(&ovpn->lock); + + hash_for_each_safe(ovpn->peers->by_id, bkt, tmp, peer, hash_entry_id) { + tmp_next_run = ovpn_peer_keepalive_work_single(peer, now, + release_list); + if (!tmp_next_run) + continue; + + /* the next worker run will be scheduled based on the shortest + * required interval across all peers + */ + if (!next_run || tmp_next_run < next_run) + next_run = tmp_next_run; + } + + return next_run; +} + +static time64_t ovpn_peer_keepalive_work_p2p(struct ovpn_priv *ovpn, + time64_t now, + struct llist_head *release_list) +{ + struct ovpn_peer *peer; + time64_t next_run = 0; + + lockdep_assert_held(&ovpn->lock); + + peer = rcu_dereference_protected(ovpn->peer, + lockdep_is_held(&ovpn->lock)); + if (peer) + next_run = ovpn_peer_keepalive_work_single(peer, now, + release_list); + + return next_run; +} + +/** + * ovpn_peer_keepalive_work - run keepalive logic on each known peer + * @work: pointer to the work member of the related ovpn object + * + * Each peer has two timers (if configured): + * 1. peer timeout: when no data is received for a certain interval, + * the peer is considered dead and it gets killed. + * 2. peer keepalive: when no data is sent to a certain peer for a + * certain interval, a special 'keepalive' packet is explicitly sent. + * + * This function iterates across the whole peer collection while + * checking the timers described above. + */ +void ovpn_peer_keepalive_work(struct work_struct *work) +{ + struct ovpn_priv *ovpn = container_of(work, struct ovpn_priv, + keepalive_work.work); + time64_t next_run = 0, now = ktime_get_real_seconds(); + LLIST_HEAD(release_list); + + spin_lock_bh(&ovpn->lock); + switch (ovpn->mode) { + case OVPN_MODE_MP: + next_run = ovpn_peer_keepalive_work_mp(ovpn, now, + &release_list); + break; + case OVPN_MODE_P2P: + next_run = ovpn_peer_keepalive_work_p2p(ovpn, now, + &release_list); + break; + } + + /* prevent rearming if the interface is being destroyed */ + if (next_run > 0 && ovpn->registered) { + netdev_dbg(ovpn->dev, + "scheduling keepalive work: now=%llu next_run=%llu delta=%llu\n", + next_run, now, next_run - now); + schedule_delayed_work(&ovpn->keepalive_work, + (next_run - now) * HZ); + } + unlock_ovpn(ovpn, &release_list); +} diff --git a/drivers/net/ovpn/peer.h b/drivers/net/ovpn/peer.h index 2a3b1031f58dd73925a9ed74aed7ac4cb7b8c4c5..e747c4b210642db990222986a80bb37c9a0413fe 100644 --- a/drivers/net/ovpn/peer.h +++ b/drivers/net/ovpn/peer.h @@ -45,13 +45,20 @@ * @crypto: the crypto configuration (ciphers, keys, etc..) * @dst_cache: cache for dst_entry used to send to peer * @bind: remote peer binding + * @keepalive_interval: seconds after which a new keepalive should be sent + * @keepalive_xmit_exp: future timestamp when next keepalive should be sent + * @last_sent: timestamp of the last successfully sent packet + * @keepalive_timeout: seconds after which an inactive peer is considered dead + * @keepalive_recv_exp: future timestamp when the peer should expire + * @last_recv: timestamp of the last authenticated received packet * @vpn_stats: per-peer in-VPN TX/RX stats * @link_stats: per-peer link/transport TX/RX stats * @delete_reason: why peer was deleted (i.e. timeout, transport error, ..) - * @lock: protects binding to peer (bind) + * @lock: protects binding to peer (bind) and keepalive* fields * @refcount: reference counter * @rcu: used to free peer in an RCU safe way * @release_entry: entry for the socket release list + * @keepalive_work: used to schedule keepalive sending */ struct ovpn_peer { struct ovpn_priv *ovpn; @@ -91,13 +98,20 @@ struct ovpn_peer { struct ovpn_crypto_state crypto; struct dst_cache dst_cache; struct ovpn_bind __rcu *bind; + unsigned long keepalive_interval; + unsigned long keepalive_xmit_exp; + time64_t last_sent; + unsigned long keepalive_timeout; + unsigned long keepalive_recv_exp; + time64_t last_recv; struct ovpn_peer_stats vpn_stats; struct ovpn_peer_stats link_stats; enum ovpn_del_peer_reason delete_reason; - spinlock_t lock; /* protects bind */ + spinlock_t lock; /* protects bind and keepalive* */ struct kref refcount; struct rcu_head rcu; struct llist_node release_entry; + struct work_struct keepalive_work; };
/** @@ -136,4 +150,7 @@ struct ovpn_peer *ovpn_peer_get_by_dst(struct ovpn_priv *ovpn, bool ovpn_peer_check_by_src(struct ovpn_priv *ovpn, struct sk_buff *skb, struct ovpn_peer *peer);
+void ovpn_peer_keepalive_set(struct ovpn_peer *peer, u32 interval, u32 timeout); +void ovpn_peer_keepalive_work(struct work_struct *work); + #endif /* _NET_OVPN_OVPNPEER_H_ */