drbd: fix disconnect/reconnect loop, if ping-timeout == ping-int

If there is no replication traffic within the idle timeout
(ping-int seconds), DRBD will send a P_PING,
and adjust the timeout to ping-timeout.

If there is no P_PING_ACK received within this ping-timeout,
DRBD finally drops the connection, and tries to re-establish it.

To decide which timeout was active, we compared the current timeout
with the ping-timeout, and dropped the connection, if that was the case.

By default, ping-int is 10 seconds, ping-timeout is 500 ms.

Unfortunately, if you configure ping-timeout to be the same as ping-int,
expiry of the idle-timeout had been mistaken for a missing ping ack,
and caused an immediate reconnection attempt.

Fix:
Allow both timeouts to be equal, use a local variable
to store which timeout is active.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index fd26666c0b08..0b17d426c32b 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -4554,6 +4554,7 @@ int drbd_asender(struct drbd_thread *thi)
         int received = 0;
         int expect   = sizeof(struct p_header80);
         int empty;
+        int ping_timeout_active = 0;
 
         sprintf(current->comm, "drbd%d_asender", mdev_to_minor(mdev));
 
@@ -4566,6 +4567,7 @@ int drbd_asender(struct drbd_thread *thi)
                         ERR_IF(!drbd_send_ping(mdev)) goto reconnect;
                         mdev->meta.socket->sk->sk_rcvtimeo =
                                 mdev->net_conf->ping_timeo*HZ/10;
+                        ping_timeout_active = 1;
                 }
 
                 /* conditionally cork;
@@ -4620,8 +4622,7 @@ int drbd_asender(struct drbd_thread *thi)
                         dev_err(DEV, "meta connection shut down by peer.\n");
                         goto reconnect;
                 } else if (rv == -EAGAIN) {
-                        if (mdev->meta.socket->sk->sk_rcvtimeo ==
-                            mdev->net_conf->ping_timeo*HZ/10) {
+                        if (ping_timeout_active) {
                                 dev_err(DEV, "PingAck did not arrive in time.\n");
                                 goto reconnect;
                         }
@@ -4660,6 +4661,11 @@ int drbd_asender(struct drbd_thread *thi)
                         if (!cmd->process(mdev, h))
                                 goto reconnect;
 
+                        /* the idle_timeout (ping-int)
+                         * has been restored in got_PingAck() */
+                        if (cmd == get_asender_cmd(P_PING_ACK))
+                                ping_timeout_active = 0;
+
                         buf      = h;
                         received = 0;
                         expect   = sizeof(struct p_header80);