Fix avahi-daemon when running on kernel < 3.9 (patch taken from Ubuntu).

Upstream-Status: Pending (unmaintained upstream)
Signed-off-by: Ross Burton <ross.burton@intel.com>

Description: SO_REUSEPORT may not exist in running kernel
 When userspace defines SO_REUSEPORT we will attempt to enable socket
 port number reuse.  However if the running kernel does not support
 this call it will fail preventing daemon startup.  If this call is
 present but fails ENOPROTOOPT then we know that actually the kernel
 does not support it and we should continue as if we did not have the
 call at all.  (LP: #1228204)
 .
 This patch could be removed from the debian package after jessie release.
Author: Andy Whitcroft <apw@canonical.com>

Index: avahi-0.6.31/avahi-core/socket.c
===================================================================
--- avahi-0.6.31.orig/avahi-core/socket.c	2013-09-20 16:36:50.000000000 +0100
+++ avahi-0.6.31/avahi-core/socket.c	2013-09-20 16:38:23.781863644 +0100
@@ -177,7 +177,8 @@
     yes = 1;
     if (setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &yes, sizeof(yes)) < 0) {
         avahi_log_warn("SO_REUSEPORT failed: %s", strerror(errno));
-        return -1;
+        if (errno != ENOPROTOOPT)
+            return -1;
     }
 #endif