Rewrite manpage section about --multihome

Part of the information was confusing, part was outdated, and part was
just not making sense.  Pointed out in trac#348.

Also add note about Linux IPv4-mapped issues as per trac#306.

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <1398453555-19706-1-git-send-email-gert@greenie.muc.de>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8635

diff --git a/doc/openvpn.8 b/doc/openvpn.8
index ae3a4e0e25a58426be210f67a810660da05b8c45..f4925f1850f8110c7721dd2975a031b90dc12847 100644 (file)
--- a/doc/openvpn.8
+++ b/doc/openvpn.8
@@ -2343,18 +2343,22 @@ is NOT specified.
 .\"*********************************************************
 .TP
 .B \-\-multihome
-Configure a multi-homed UDP server.  This option can be used when
-OpenVPN has been configured to listen on all interfaces, and will
-attempt to bind client sessions to the interface on which packets
-are being received, so that outgoing packets will be sent out
-of the same interface.  Note that this option is only relevant for
-UDP servers and currently is only implemented on Linux.
-
-Note: clients connecting to a
-.B \-\-multihome
-server should always use the
-.B \-\-nobind
-option.
+Configure a multi-homed UDP server.  This option needs to be used when
+a server has more than one IP address (e.g. multiple interfaces, or
+secondary IP addresses), and is not using
+.B \-\-local
+to force binding to one specific address only.  This option will
+add some extra lookups to the packet path to ensure that the UDP reply
+packets are always sent from the address that the client is
+talking to. This is not supported on all platforms, and it adds more
+processing, so it's not enabled by default.
+
+Note: this option is only relevant for UDP servers.
+
+Note 2: if you do an IPv6+IPv4 dual-stack bind on a Linux machine with
+multiple IPv4 address, connections to IPv4 addresses will not work
+right on kernels before 3.14, due to missing kernel support for the
+IPv4-mapped case.
 .\"*********************************************************
 .TP
 .B \-\-echo [parms...]