persistent keepalive: add kernel mechanism

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

7 files changed, 42 insertions, 4 deletions

diff --git a/src/config.c b/src/config.c
index 3df5d9e..767d31a 100644
--- a/src/config.c
+++ b/src/config.c
@@ -103,6 +103,13 @@ static int set_peer(struct wireguard_device *wg, void __user *user_peer, size_t
 			break;
 	}
 
+	if (in_peer.persistent_keepalive_interval != (uint16_t)-1) {
+		if (in_peer.persistent_keepalive_interval && (in_peer.persistent_keepalive_interval < 10 || in_peer.persistent_keepalive_interval > 3600))
+			ret = -EINVAL;
+		else
+			peer->persistent_keepalive_interval = in_peer.persistent_keepalive_interval;
+	}
+
 	if (netdev_pub(wg)->flags & IFF_UP)
 		packet_send_queue(peer);
 
@@ -241,6 +248,7 @@ static int populate_peer(struct wireguard_peer *peer, void *ctx)
 	out_peer.last_handshake_time = peer->walltime_last_handshake;
 	out_peer.tx_bytes = peer->tx_bytes;
 	out_peer.rx_bytes = peer->rx_bytes;
+	out_peer.persistent_keepalive_interval = peer->persistent_keepalive_interval;
 
 	ipmasks_data.out_len = data->out_len;
 	ipmasks_data.data = data->data;
diff --git a/src/peer.h b/src/peer.h
index 05ee7bd..6d74385 100644
--- a/src/peer.h
+++ b/src/peer.h
@@ -27,8 +27,9 @@ struct wireguard_peer {
 	struct cookie latest_cookie;
 	struct hlist_node pubkey_hash;
 	uint64_t rx_bytes, tx_bytes;
-	struct timer_list timer_retransmit_handshake, timer_send_keepalive, timer_new_handshake, timer_kill_ephemerals;
+	struct timer_list timer_retransmit_handshake, timer_send_keepalive, timer_new_handshake, timer_kill_ephemerals, timer_persistent_keepalive;
 	unsigned int timer_handshake_attempts;
+	uint16_t persistent_keepalive_interval;
 	bool timer_need_another_keepalive;
 	struct timeval walltime_last_handshake;
 	struct sk_buff_head tx_packet_queue;
diff --git a/src/receive.c b/src/receive.c
index 1b86489..db19527 100644
--- a/src/receive.c
+++ b/src/receive.c
@@ -273,7 +273,7 @@ void packet_receive(struct wireguard_device *wg, struct sk_buff *skb)
 	static const u8 addr;
 #endif
 
-	if (skb_data_offset(skb, &offset, &len) < 0)
+	if (unlikely(skb_data_offset(skb, &offset, &len) < 0 || !len))
 		goto err;
 	switch (message_determine_type(skb->data + offset, len)) {
 	case MESSAGE_HANDSHAKE_INITIATION:
diff --git a/src/socket.c b/src/socket.c
index ac19a47..5b7bbf8 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -4,6 +4,7 @@
 #include "socket.h"
 #include "packets.h"
 #include "messages.h"
+#include "timers.h"
 
 #include <linux/net.h>
 #include <linux/if_vlan.h>
@@ -250,8 +251,10 @@ int socket_send_skb_to_peer(struct wireguard_peer *peer, struct sk_buff *skb, u8
 	read_lock_bh(&peer->endpoint_lock);
 
 	ret = send(dev, skb, dst, &peer->endpoint_flow.fl4, &peer->endpoint_flow.fl6, &peer->endpoint_addr, rcu_dereference(peer->device->sock4), rcu_dereference(peer->device->sock6), dscp);
-	if (!ret)
+	if (!ret) {
+		timers_any_packet_sent(peer);
 		peer->tx_bytes += skb_len;
+	}
 
 	read_unlock_bh(&peer->endpoint_lock);
 	rcu_read_unlock();
@@ -265,7 +268,8 @@ int socket_send_buffer_to_peer(struct wireguard_peer *peer, void *buffer, size_t
 	if (!skb)
 		return -ENOMEM;
 	skb_reserve(skb, SKB_HEADER_LEN);
-	memcpy(skb_put(skb, len), buffer, len);
+	if (likely(buffer))
+		memcpy(skb_put(skb, len), buffer, len);
 	return socket_send_skb_to_peer(peer, skb, dscp);
 }
 
diff --git a/src/timers.c b/src/timers.c
index 47d7854..01933a8 100644
--- a/src/timers.c
+++ b/src/timers.c
@@ -76,6 +76,15 @@ static void queued_expired_kill_ephemerals(struct work_struct *work)
 	peer_put(peer);
 }
 
+static void expired_send_persistent_keepalive(unsigned long ptr)
+{
+	struct wireguard_peer *peer = (struct wireguard_peer *)ptr;
+
+	if (unlikely(!peer->persistent_keepalive_interval))
+		return;
+	socket_send_buffer_to_peer(peer, NULL, 0, 0);
+}
+
 void timers_data_sent(struct wireguard_peer *peer)
 {
 	if (likely(peer->timer_send_keepalive.data))
@@ -121,6 +130,12 @@ void timers_ephemeral_key_created(struct wireguard_peer *peer)
 	do_gettimeofday(&peer->walltime_last_handshake);
 }
 
+void timers_any_packet_sent(struct wireguard_peer *peer)
+{
+	if (peer->persistent_keepalive_interval && likely(peer->timer_persistent_keepalive.data))
+		mod_timer(&peer->timer_persistent_keepalive, jiffies + HZ * peer->persistent_keepalive_interval);
+}
+
 void timers_init_peer(struct wireguard_peer *peer)
 {
 	init_timer(&peer->timer_retransmit_handshake);
@@ -139,6 +154,10 @@ void timers_init_peer(struct wireguard_peer *peer)
 	peer->timer_kill_ephemerals.function = expired_kill_ephemerals;
 	peer->timer_kill_ephemerals.data = (unsigned long)peer;
 
+	init_timer(&peer->timer_persistent_keepalive);
+	peer->timer_persistent_keepalive.function = expired_send_persistent_keepalive;
+	peer->timer_persistent_keepalive.data = (unsigned long)peer;
+
 	INIT_WORK(&peer->clear_peer_work, queued_expired_kill_ephemerals);
 }
 
@@ -160,6 +179,10 @@ void timers_uninit_peer(struct wireguard_peer *peer)
 		del_timer(&peer->timer_kill_ephemerals);
 		peer->timer_kill_ephemerals.data = 0;
 	}
+	if (peer->timer_persistent_keepalive.data) {
+		del_timer(&peer->timer_persistent_keepalive);
+		peer->timer_persistent_keepalive.data = 0;
+	}
 }
 void timers_uninit_peer_wait(struct wireguard_peer *peer)
 {
diff --git a/src/timers.h b/src/timers.h
index c5e9678..e8acba3 100644
--- a/src/timers.h
+++ b/src/timers.h
@@ -15,5 +15,6 @@ void timers_any_authorized_packet_received(struct wireguard_peer *peer);
 void timers_handshake_initiated(struct wireguard_peer *peer);
 void timers_handshake_complete(struct wireguard_peer *peer);
 void timers_ephemeral_key_created(struct wireguard_peer *peer);
+void timers_any_packet_sent(struct wireguard_peer *peer);
 
 #endif
diff --git a/src/uapi.h b/src/uapi.h
index 21d4af1..6e3662f 100644
--- a/src/uapi.h
+++ b/src/uapi.h
@@ -98,6 +98,7 @@ struct wgpeer {
 	__u32 replace_ipmasks : 1; /* Set */
 
 	__u16 num_ipmasks; /* Get/Set */
+	__u16 persistent_keepalive_interval; /* Get/Set -- 0 = off, 0xffff = unset */
 };
 
 struct wgdevice {