So I'm configuring a QEMU guest on my Debian Wheezy server, using virt-manager.
As guest I've installed Ubuntu 14.04.1 server.
The server contains the following iptables rule:
iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 3080
iptables -t nat -I OUTPUT -p tcp -d 127.0.0.1 --dport 80 -j REDIRECT --to-ports 3080
This was taken from the serverfault question "How to run a server on port 80 as a normal user on Linux?"
So incoming HTTP requests on port 80 to the Debian host are being redirected to the correct application.
But, as a side effect, outgoing requests from my QEMU guest are also being redirected there. How can I fix that?