Re: [Qemu-devel] usermode-networking problem

[James Ascroft-Leigh <jwal@declarative.co.uk>]

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On Sun, 2004-05-23 at 21:28 +0100, Carlos Valiente wrote:
> On Sun, 2004-05-23 at 19:58, Adrian Smarzewski wrote:
> > sh-2.05b# ping -c 3 212.77.100.101
> > PING 212.77.100.101 (212.77.100.101) 56(84) bytes of data.
> > 
> > --- 212.77.100.101 ping statistics ---
> > 3 packets transmitted, 0 received, 100% packet loss, time 2018ms
> > 
> > 
> > I don't know why. Should I configure something on host os?
> 
> Yes: On your host you have to:
> 
> 1. Enable IP forwarding:
[...]
> 2. Enable masquerading
[...]

Not sure but I thought that the purpose of the the -user-net feature was
to remove the need for any superuser privileges or special host
configuration.

From what I understand user-mode networking is quite a feat to pull off,
with ICMP (e.g. ping(8)) being probably harder than TCP or UDP due to
the interfaces made available by the system to non-superusers.  I have
not looked at the code but the suggestion has been made that it may even
be necessary to fork and exec the (setuid) /usr/ping executable.

I would suspect that, as previously mentioned, UDP is working but the
connection tracking of the TCP implementation is broken/incomplete in
some way.

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