Prevent memory drain for long lasting floating sessions

Prevent memory drain for long lasting floating sessions

For every float event we generate prefix, which allocates 256 + 64
bytes. That memory is reclaimed when client disconnects, so long lasting
and constantly floating sessions drain memory.

As a fix use preallocated buffer inside multi_instance for storing
multi_prefix.

Signed-off-by: Lev Stipakov <lstipakov@gmail.com>
Acked-by: Steffan Karger <steffan.karger@fox-it.com>
Message-Id: 1418057325-13265-1-git-send-email-lstipakov@gmail.com
URL: http://article.gmane.org/gmane.network.openvpn.devel/9321
Signed-off-by: David Sommerseth <davids@redhat.com>