[Qemu-discuss] QEMU TAP networking on Windows XP host.

[alarson]

I am trying to setup a QEMU client on a windows host using TAP
networking.  My only interesting requirement is that applications on
the host be able to connect to the client on effectively arbitrary
ports (the client will be running several TCP based services).  This
rules out the use of "-net user" and TCP redirects.

I am able to get my client up and running using TCP redirects (-net
user), but I can't get either bridged or routed TAP networking to
work.  In both TAP cases the client sees packets from the host
(Windows), but the host doesn't see any of the responses.

I am able to use user, TAP bridged and TAP routed networking on a Unix
host, so the problem I'm seeing appears to be restricted to using a
Windows host.  The host is Window XP SP3 with latest patches.  The
client is a home grown app using LwIP, although I've tried
damnsmallinux with equivalent results.

My network config (all statically assigned):

Host LAN:   192.168.0.x
Host TAP:   10.0.2.1
Client TAP: 10.0.2.15
netmask:    255.255.255.0 (all interfaces).

I'm using the TAP driver from openVPN 2.2, although I've also tried
2.2.2, and 2.3 alpha.  Windows firewall is "off", and I've tried
putting the TAP driver into promiscuous mode, with no change to the
symptoms.  My client is using the rtl8139 network emulation, and I've
not added any routes (on either end).  The TAP driver is as installed 
by openvpn except for setting the IP address and netmask.

qemu-system-mips -net tap,ifname=tap0 -net nic,model=rtl8139 -kernel 
mykern.exe

I must be doing something basic wrong, but I can't see it.