tree bf67101d9bb89475b89a781736e8a480b9af8ae8
parent 0f6093a9b27695414900b7ef66efd99977837e9b
author Simone Gotti <simone.gotti@gmail.com> 1402438551 +0200
committer Willy Tarreau <w@1wt.eu> 1402514854 +0200
encoding latin1

BUG/MEDIUM: Fix unhandled connections problem with systemd daemon mode and SO_REUSEPORT.

Using the systemd daemon mode the parent doesn't exits but waits for
his childs without closing its listening sockets.

As linux 3.9 introduced a SO_REUSEPORT option (always enabled in
haproxy if available) this will give unhandled connections problems
after an haproxy reload with open connections.

The problem is that when on reload a new parent is started (-Ds
$oldchildspids), in haproxy.c main there's a call to start_proxies
that, without SO_REUSEPORT, should fail (as the old processes are
already listening) and so a SIGTOU is sent to old processes. On this
signal the old childs will call (in pause_listener) a shutdown() on
the listening fd. From my tests (if I understand it correctly) this
affects the in kernel file (so the listen is really disabled for all
the processes, also the parent).

Instead, with SO_REUSEPORT, the call to start_proxies doesn't fail and
so SIGTOU is never sent. Only SIGUSR1 is sent and the listen isn't
disabled for the parent but only the childs will stop listening (with
a call to close())

So, with SO_REUSEPORT, the old childs will close their listening
sockets but will wait for the current connections to finish or
timeout, and, as their parent has its listening socket open, the
kernel will schedule some connections on it. These connections will
never be accepted by the parent as it's in the waitpid loop.

This fix will close all the listeners on the parent before entering the
waitpid loop.

Signed-off-by: Simone Gotti <simone.gotti@gmail.com>