[2/8] mesos git commit: Prevented a race when relinking with SSL downgrade enabled.

[jo...@apache.org]

Prevented a race when relinking with SSL downgrade enabled.

If there are two or more actors, on the same OS process, that try to
relink at the same time, there is a potential CHECK failure when SSL
downgrade is also enabled.  The following interleaving is problematic:
|             Actor A             |             Actor B             |
|---------------------------------+---------------------------------|
|        Starts to relink.        |        Starts to relink.        |
|        Creates socket A.        |                                 |
|   Replaces link with Socket A.  |                                 |
| Tries to connect with Socket A. |                                 |
|                                 |        Creates socket B.        |
|  Connection fails due to SSL.   |   Replaces link with Socket B.  |
|     Attempts to downgrade.      |                                 |
|     Tries to replace link.      |                                 |
The last step in the interleaving fails because we assert that the
socket we are swapping out exists in the `SocketManager`s state.

Review: https://reviews.apache.org/r/52182/


Project: http://git-wip-us.apache.org/repos/asf/mesos/repo
Commit: http://git-wip-us.apache.org/repos/asf/mesos/commit/be7d29a3
Tree: http://git-wip-us.apache.org/repos/asf/mesos/tree/be7d29a3
Diff: http://git-wip-us.apache.org/repos/asf/mesos/diff/be7d29a3

Branch: refs/heads/1.0.x
Commit: be7d29a3159d3e7d042a0e24476ed9d4a8cb5bcb
Parents: 152484b
Author: Joseph Wu <jo...@mesosphere.io>
Authored: Wed Sep 28 12:33:31 2016 -0700
Committer: Joseph Wu <jo...@apache.org>
Committed: Wed Sep 28 13:22:16 2016 -0700

----------------------------------------------------------------------
 3rdparty/libprocess/src/process.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/mesos/blob/be7d29a3/3rdparty/libprocess/src/process.cpp
----------------------------------------------------------------------
diff --git a/3rdparty/libprocess/src/process.cpp b/3rdparty/libprocess/src/process.cpp
index 5b7be3a..7a750a0 100644
--- a/3rdparty/libprocess/src/process.cpp
+++ b/3rdparty/libprocess/src/process.cpp
@@ -1453,6 +1453,14 @@ void SocketManager::link_connect(
     // POLL socket.
     if (attempt_downgrade) {
       synchronized (mutex) {
+        // It is possible that a prior call to `link()` with `RECONNECT`
+        // semantics has swapped out this socket before we finished
+        // connecting. In this case, we simply stop here and allow the
+        // latest created socket to complete the link.
+        if (sockets.count(socket) <= 0) {
+          return;
+        }
+
         Try<Socket> create = Socket::create(Socket::POLL);
         if (create.isError()) {
           VLOG(1) << "Failed to link, create socket: " << create.error();