drbd: More random to the connect logic

Since the listening socket is open all the time, it was possible to
get into stable "initial packet S crossed" loops.

* when both sides realize in the drbd_socket_okay() call at the end
  of the loop that the other side closed the main socket you had
  the chance to get into a stable loop with repeated "packet S crossed"
  messages.

* when both sides do not realize with the drbd_socket_okay() call at the end
  of the loop that the other side closed the main socket you had
  the chance to get into a stable loop with alternating "packet S crossed"
  "packet M crossed" messages.

In order to break out these stable loops randomize the behaviour if
such a crossing of P_INITIAL_DATA or P_INITIAL_META packets is detected.

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

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 1567e9bb9bde..26c30fd64ecf 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -949,20 +949,25 @@ retry:
                                 if (sock.socket) {
                                         conn_warn(tconn, "initial packet S crossed\n");
                                         sock_release(sock.socket);
+                                        sock.socket = s;
+                                        goto randomize;
                                 }
                                 sock.socket = s;
                                 break;
                         case P_INITIAL_META:
+                                set_bit(DISCARD_CONCURRENT, &tconn->flags);
                                 if (msock.socket) {
                                         conn_warn(tconn, "initial packet M crossed\n");
                                         sock_release(msock.socket);
+                                        msock.socket = s;
+                                        goto randomize;
                                 }
                                 msock.socket = s;
-                                set_bit(DISCARD_CONCURRENT, &tconn->flags);
                                 break;
                         default:
                                 conn_warn(tconn, "Error receiving initial packet\n");
                                 sock_release(s);
+randomize:
                                 if (random32() & 1)
                                         goto retry;
                         }