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 | 77 +++++++++++++++++ drivers/net/ovpn/io.h | 5 ++ drivers/net/ovpn/main.c | 3 + drivers/net/ovpn/ovpnstruct.h | 2 + drivers/net/ovpn/peer.c | 188 ++++++++++++++++++++++++++++++++++++++++++ drivers/net/ovpn/peer.h | 15 ++++ drivers/net/ovpn/proto.h | 2 - 7 files changed, 290 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c index deda19ab87391f86964ba43088b7847d22420eee..63c140138bf98e5d1df79a2565b666d86513323d 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. */ @@ -105,6 +132,9 @@ void ovpn_decrypt_post(void *data, int ret) goto drop; }
+ /* keep track of last received authenticated packet for keepalive */ + peer->last_recv = ktime_get_real_seconds(); + /* point to encapsulated IP packet */ __skb_pull(skb, payload_offset);
@@ -121,6 +151,12 @@ 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", + peer->ovpn->dev->name, peer->id); + goto drop; + } + net_info_ratelimited("%s: unsupported protocol received from peer %u\n", peer->ovpn->dev->name, peer->id); goto drop; @@ -221,6 +257,10 @@ void ovpn_encrypt_post(void *data, int ret) /* no transport configured yet */ goto err; } + + /* keep track of last sent packet for keepalive */ + peer->last_sent = ktime_get_real_seconds(); + /* skb passed down the stack - don't free it */ skb = NULL; err: @@ -361,3 +401,40 @@ 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 + */ +void ovpn_xmit_special(struct ovpn_peer *peer, const void *data, + const unsigned int len) +{ + struct ovpn_struct *ovpn; + struct sk_buff *skb; + + ovpn = peer->ovpn; + if (unlikely(!ovpn)) + return; + + skb = alloc_skb(256 + len, GFP_ATOMIC); + if (unlikely(!skb)) + return; + + skb_reserve(skb, 128); + skb->priority = TC_PRIO_BESTEFFORT; + __skb_put_data(skb, data, len); + + /* increase reference counter when passing peer to sending queue */ + if (!ovpn_peer_hold(peer)) { + netdev_dbg(ovpn->dev, "%s: cannot hold peer reference for sending special packet\n", + __func__); + kfree_skb(skb); + return; + } + + ovpn_send(ovpn, skb, peer); +} diff --git a/drivers/net/ovpn/io.h b/drivers/net/ovpn/io.h index ad81dd86924689309b3299573575a1705eddaf99..eb224114152c29f42aadf026212e8d278006b490 100644 --- a/drivers/net/ovpn/io.h +++ b/drivers/net/ovpn/io.h @@ -10,9 +10,14 @@ #ifndef _NET_OVPN_OVPN_H_ #define _NET_OVPN_OVPN_H_
+#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 c7453127ab640d7268c1ce919a87cc5419fac9ee..1bd563e3f16f49dd01c897fbe79cbd90f4b8e9aa 100644 --- a/drivers/net/ovpn/main.c +++ b/drivers/net/ovpn/main.c @@ -191,6 +191,7 @@ static int ovpn_newlink(struct net *src_net, 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);
err = ovpn_mp_alloc(ovpn); if (err < 0) @@ -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); + switch (ovpn->mode) { case OVPN_MODE_P2P: ovpn_peer_release_p2p(ovpn); diff --git a/drivers/net/ovpn/ovpnstruct.h b/drivers/net/ovpn/ovpnstruct.h index 12ed5e22c2108c9f143d1984048eb40c887cac63..4ac00d550ecb9f84c6c132dd2bdc0a3fc0ab342c 100644 --- a/drivers/net/ovpn/ovpnstruct.h +++ b/drivers/net/ovpn/ovpnstruct.h @@ -43,6 +43,7 @@ struct ovpn_peer_collection { * @peer: in P2P mode, this is the only remote peer * @dev_list: entry for the module wide device list * @gro_cells: pointer to the Generic Receive Offload cell + * @keepalive_work: struct used to schedule keepalive periodic job */ struct ovpn_struct { struct net_device *dev; @@ -54,6 +55,7 @@ struct ovpn_struct { struct ovpn_peer __rcu *peer; struct list_head dev_list; 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 c7dc9032c2b55fd42befc1f3e7a0eca893a96576..e8a42212af391916b5321e729f7e8a864d0a541f 100644 --- a/drivers/net/ovpn/peer.c +++ b/drivers/net/ovpn/peer.c @@ -22,6 +22,34 @@ #include "peer.h" #include "socket.h"
+/** + * 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, + "%s: scheduling keepalive for peer %u: interval=%u timeout=%u\n", + __func__, peer->id, interval, timeout); + + peer->keepalive_interval = interval; + peer->last_sent = now; + peer->keepalive_xmit_exp = now + interval; + + peer->keepalive_timeout = timeout; + 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_new - allocate and initialize a new peer object * @ovpn: the openvpn instance inside which the peer should be created @@ -815,6 +843,19 @@ int ovpn_peer_del(struct ovpn_peer *peer, enum ovpn_del_peer_reason reason) } }
+static int ovpn_peer_del_nolock(struct ovpn_peer *peer, + enum ovpn_del_peer_reason reason) +{ + switch (peer->ovpn->mode) { + case OVPN_MODE_MP: + return ovpn_peer_del_mp(peer, reason); + case OVPN_MODE_P2P: + return ovpn_peer_del_p2p(peer, reason); + default: + return -EOPNOTSUPP; + } +} + /** * ovpn_peers_free - free all peers in the instance * @ovpn: the instance whose peers should be released @@ -830,3 +871,150 @@ void ovpn_peers_free(struct ovpn_struct *ovpn) ovpn_peer_unhash(peer, OVPN_DEL_PEER_REASON_TEARDOWN); spin_unlock_bh(&ovpn->peers->lock); } + +static time64_t ovpn_peer_keepalive_work_single(struct ovpn_peer *peer, + time64_t now) +{ + time64_t next_run1, next_run2, delta; + 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; + delta = now - peer->last_recv; + if (delta < timeout) { + peer->keepalive_recv_exp = now + timeout - delta; + 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_del_nolock(peer, OVPN_DEL_PEER_REASON_EXPIRED); + return 0; + } + + /* check for peer keepalive */ + expired = false; + interval = peer->keepalive_interval; + delta = now - peer->last_sent; + if (delta < interval) { + peer->keepalive_xmit_exp = now + interval - delta; + 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); + ovpn_xmit_special(peer, ovpn_keepalive_message, + sizeof(ovpn_keepalive_message)); + } + + if (next_run1 < next_run2) + return next_run1; + + return next_run2; +} + +static time64_t ovpn_peer_keepalive_work_mp(struct ovpn_struct *ovpn, + time64_t now) +{ + time64_t tmp_next_run, next_run = 0; + struct hlist_node *tmp; + struct ovpn_peer *peer; + int bkt; + + spin_lock_bh(&ovpn->peers->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); + 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; + } + spin_unlock_bh(&ovpn->peers->lock); + + return next_run; +} + +static time64_t ovpn_peer_keepalive_work_p2p(struct ovpn_struct *ovpn, + time64_t now) +{ + struct ovpn_peer *peer; + time64_t next_run = 0; + + spin_lock_bh(&ovpn->lock); + peer = rcu_dereference_protected(ovpn->peer, + lockdep_is_held(&ovpn->lock)); + if (peer) + next_run = ovpn_peer_keepalive_work_single(peer, now); + spin_unlock_bh(&ovpn->lock); + + 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_struct *ovpn = container_of(work, struct ovpn_struct, + keepalive_work.work); + time64_t next_run = 0, now = ktime_get_real_seconds(); + + switch (ovpn->mode) { + case OVPN_MODE_MP: + next_run = ovpn_peer_keepalive_work_mp(ovpn, now); + break; + case OVPN_MODE_P2P: + next_run = ovpn_peer_keepalive_work_p2p(ovpn, now); + 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); + } +} diff --git a/drivers/net/ovpn/peer.h b/drivers/net/ovpn/peer.h index 942b90c84a0fb9e6fbb96f6df7f7842a9f738caf..952927ae78a3ab753aaf2c6cc6f77121bdac34be 100644 --- a/drivers/net/ovpn/peer.h +++ b/drivers/net/ovpn/peer.h @@ -43,6 +43,12 @@ * @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 * @halt: true if ovpn_peer_mark_delete was called * @vpn_stats: per-peer in-VPN TX/RX stays * @link_stats: per-peer link/transport TX/RX stats @@ -91,6 +97,12 @@ 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; bool halt; struct ovpn_peer_stats vpn_stats; struct ovpn_peer_stats link_stats; @@ -137,4 +149,7 @@ struct ovpn_peer *ovpn_peer_get_by_dst(struct ovpn_struct *ovpn, bool ovpn_peer_check_by_src(struct ovpn_struct *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_ */ diff --git a/drivers/net/ovpn/proto.h b/drivers/net/ovpn/proto.h index 32af6b8e574381fb719a1b3b9de3ae1071cc4846..0de8bafadc89ebb85ce40de95ef394588738a4ad 100644 --- a/drivers/net/ovpn/proto.h +++ b/drivers/net/ovpn/proto.h @@ -35,8 +35,6 @@ #define OVPN_OP_SIZE_V2 4 #define OVPN_PEER_ID_MASK 0x00FFFFFF #define OVPN_PEER_ID_UNDEF 0x00FFFFFF -/* first byte of keepalive message */ -#define OVPN_KEEPALIVE_FIRST_BYTE 0x2a /* first byte of exit message */ #define OVPN_EXPLICIT_EXIT_NOTIFY_FIRST_BYTE 0x28