Re: [Qemu-discuss] User-mode Networking stack - how to allow incoming connections

[Mike Lovell]

On 05/15/2012 02:26 AM, address@hidden wrote:
> Hello,
> In the QEMU's documentation, concerning networking 
> (http://en.wikibooks.org/wiki/QEMU/Networking), for the user-mode 
> stack it's said that "By default, however, it acts as a firewall and 
> does not permit any incoming traffic.". Such default configuration, in 
> my experience (I'm using QEMU 1.0.1 with WinXP as guest OS) 
> effectively prevents web pages to be accessed. The wording suggest the 
> possibility the incoming traffic to be allowed in user-mode 
> networking. If this indeed is possible, how exactly it could be done?

user-mode networking works by having a small IP stack running in the 
qemu guest. using the default options, it will NAT traffic coming from 
the guest through the host. return traffic should work since the qemu 
guest is opening sockets and connecting to the outside and return 
packets will be delivered to those sockets. (probably bad wording there. 
hopefully you get my point.)

using user-mode networking, hosts outside of the guest cannot initiate a 
connection to the guest normally. this can be modified by using the 
-redir or -net user,hostfwd= options. these will cause the qemu process 
to open sockets listening on the host ports and NAT traffic received by 
them to the guest ports. this is similar in concept to configuring port 
forwarding on a home router.

hopefully that provides some insight to how user-mode networking works. 
since you said your using 1.0.1 on windows, i'll point you at the 
changelog like i did in an email a few minutes ago. 
http://wiki.qemu.org/ChangeLog/Next says that user-mode networking was 
broken on windows from 0.14 and fixed in 1.1-rc1. so if you networking 
isn't working, i'd recommend trying updating to 1.1-rc1.

mike