[Qemu-devel] [Bug 577908] Re: qemu 0.12.3 default networking DNS broken

[Irek Szczesniak]

Thanks for your instructions, Stefan.

Wireshark showed me that in DHCPOFFER and DHCPACK there are given the
DNS server and the router addresses.  Then I saw that the CentOS
installer uses the assigned IP address to query the 10.0.2.3 DNS server.
So the CentOS insaller got the DNS address and uses it to try to
reverse-resolve its IP (10.0.2.15) address.

Why the installer logs "DHCPv4 eth0 - option routers: ", i.e. no
routers, that I don't know.

Moreover, why the installer logs "no DNS servers, can't look up
hostname" I also don't know.  It was given the address, and it even used
the server.  I interpreted "can't look up hostname" as "can't look up
some hostname", while it probably means "can't figure out my hostname".

In my previous tests I didn't continue, because I assumed something went
wrong, but now I tried again, and things just work: the installer can
resolve names and reach the Internet.

In conclusion, I raised a false alarm based on the CentOS installer
messages, and with more debugging, it turns out that QEMU works fine.

Thank you, Stefan, for your help.  I'm happy now.


Best,
Irek
(irkos.org)

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https://bugs.launchpad.net/bugs/577908

Title:
  qemu 0.12.3 default networking DNS broken

Status in QEMU:
  Incomplete

Bug description:
  This might be something simple and known, but I don't find such 
information... I installed qemu 0.12.3 from source on a Linux/x86-64 host and 
observe that, running a debian testing guest (squeeze netinst, also the 
installed system), the DNS setup that qemu's  DHCP provides is not working.

Namely, nameserver 10.0.2.3 in /etc/resolv.conf (as created by DHCP) does not 
help name resolution, but replacing the IP with my actual DNS server does work. 
Now this is still unfortunate as it is very cumbersome to replace the DNS for 
every system I run in qemu for testing... it used to work before with earlier 
versions.

If there is some easy means to help debug this, I'll try to help... but right 
now I am rather clueless.