Fix server routes not working in topology subnet with --server [v3]

The IPv4 routing code needs an IPv4 address to point a route to, and
in --topology subnet mode, the *server* did not have one set by default.

So we now just default --route-gateway to the next address right after
the server address - the specific address doesn't matter, as the correct
next-hop will not be resolved by the host OS but by the OpenVPN daemon.
All that is needed is "it's in the subnet routed to the tun interface".

Using the server address itself would work on unix, but doesn't work with
the Windows TAP driver (as it does not spoof ARP responses for itself).

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1405254527-23833-1-git-send-email-gert@greenie.muc.de>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8904
(cherry picked from commit 4cc6a2595947a0e2f13b37637899bfc50f8509aa)
Add topology in sample server configuration file

This is an OpenPGP/MIME signed message (RFC 4880 and 3156)
On modern systems, topology subnet should always be set, but it's
missing in the configuration file.
Add it with a short explanation.

Signed-off-by: Philipp Hagemeister <phihag@phihag.de>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <53BF9998.5020906@phihag.de>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8878
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit c277757fcf7fb4c2713db154439f937d48cfae61)