[Openvpn-devel] [PATCH] cstp: Add workaround for netmask on windows

Gert Doering gert at greenie.muc.de
Mon Jun 23 04:33:26 PDT 2014


On Mon, Jun 23, 2014 at 12:12:38PM +0100, David Woodhouse wrote:
> > Another side effect is that if the TAP Windows driver is being
> > initialized with netmask then there's no way
> > to convince windows to route packets through that interface.
> If this isn't considered a bug in the Windows tap driver, (and I suspect
> it isn't, because they're working around some true horridness in the
> Windows network stack), 

Well, for Windows, a tap interface is an ethernet interface in good
standing - and not a point-to-point thing like a tun on other platforms
where there really is no "subnet" but "my IP, and what's on the other side".

So, as you can't put on normal ethernet interfaces, you
can't do that on the tap driver either.  I'm not sure whether .254 would
work - which is why OpenVPN's net30 always wasted a /30 in the old
days, or uses a larger subnet now.

There is not very much we can do to "fix" that in the tap driver, 
especially as the ifconfig is done outside the driver in the generic
IP part of the stack...

USENET is *not* the non-clickable part of WWW!
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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