virtualbox.org

I'm running virtualbox 3.0.4 on a winXP SP3 host and opensuse11.1 as a guest OS.
From within opensuse11.1, I do a "ping www.google.com" and ping reports a 52% packet loss. However, when I captured and analyzed the icmp traffic (using "tcpdump icmp > /tmp/dump" and then "grep reply /tmp/dump | wc -l" ), I found out that there was no packet loss!!!

Whenever I ping a host, ping reports a serious packet loss, but tcpdump shows there wasn't actually a packet loss.

Same thing happening with a trixbox CE 2.8.0.1 as a guest OS.

Any ideas?

opensuse11.1 has a 2.6.27.25-0.1-pae SMP kernel while trixbox CE 2.8.0.1 has a 2.6.18-128.1.10.el5 SMP kernel, I've set up both using NAT networking.

PS: I'm aware that my method of quickly analyzing tcpdump output is not absolutely accurate but then I manually checked (and verified) the "seq" field in the dump

UPDATE: I tried using bridged networking and the packet loss disappeared, so I guess that this is an issue of virtualbox in nat networking. Still, it really puzzles me how a packet could show in tcpdump but never reach the application layer (ping)...

after some more troubleshooting, i've found out that the reply packets have messed up MAC addresses.

When, I do "tcpdump -p" (ie not enter promiscious mode) then the output of tcpdump matches the one from ping. I've also verified with wireshark that most of the icmp replies have various other mac addresses.

So, there's a bug in the NAT mode of virtualbox that messes up the MAC address. Should I open a ticket?

Btw, is there a way to have a linux system accept any packet that matches its IP regardless if it has the correct MAC address?

Yes open a ticket and include those traces.