Test IPv6 over IPv6

[Samuli Seppänen]

This is a testing task for those who might be interested in helping out. The description below is taken from ​Gert's email.

On Fri, Sep 25, 2015 at 03:01:01PM +0300, Samuli Seppänen wrote:
> We'd need some help build-testing a patched[*] OpenVPN version with 
> Cygwin and Visual Studio:
>
> <http://build.openvpn.net/downloads/temp/openvpn-2.3_git.tar.gz>
>
> This tree already builds fine on mingw_w64 which is enough for doing the 
> official builds.

Heiko tested on Cygwin, Lev made it work on MSVC2013 (and the necessary
changes for that have been merged).

So, now this needs people to actually run IPv6-over-IPv6 to *use* the
functionality and report whether it breaks in their setup.

What you need: IPv6 connectivity between OpenVPN client and server, and
IPv6 routing *into* the tunnel, with a route that overlaps the IPv6 address
of the server - either using "redirect-gateway ipv6", or pushing things
like "route-ipv6 2000::/3" with a server inside 2000::/3...  if you do
this, you should see something like this in the log:

Tue Oct  6 13:28:57 2015 GDG6: remote_host_ipv6=2607:fc50:1001:5200::4
Tue Oct  6 13:28:57 2015 ROUTE6_GATEWAY 2001:608:4::1 IFACE=eth0
Tue Oct  6 13:28:57 2015 ROUTE6: 2607:fc50:1001::/48 overlaps IPv6 remote
 2607:fc50:1001:5200::4, adding host route to VPN endpoint
Tue Oct  6 13:28:57 2015 add_route_ipv6(2607:fc50:1001:5200::4/128 -> 2001:608:4::1
 metric 1) dev eth0
Tue Oct  6 13:28:57 2015 /bin/route -A inet6 add 2607:fc50:1001:5200::4/128 dev eth0 gw 
2001:608:4::1 metric 1

the first line is "this is the IPv6 address of the VPN server", the
"ROUTE6_GATEWAY" line is "this is the gateway and interface we have
discovered!".  The "overlap" notice means the feature will actually
kick in - it won't, if you have no overlapping routes into the tunnel,
or connect over IPv4 - and the last two lines are the installing of
the /128 host route, which better should work as well 

I tested this for 6 scenarios on 9 (!) platforms, so I'm reasonably sure
it works for the common case - but there will be unexpected cases...

gert

[ValdikSS]

Can you please compile it for Windows and provide an exe?

[Gert Döring]

All the more recent snapshots had this... nobody ever complained, so I just assume this works.

If not, we'll hear more about this as soon as 2.4 hits the shelves :-)