Re: [Qemu-devel] Connection breaks for macvtap

[Anthony Liguori <anthony@codemonkey.ws>]

Richa Marwaha <rmarwah@us.ibm.com> writes:

> Hi
>
> I am trying to run some KVM fuzz testing where I have a tool called scapy
> running on my host and guest which changes the data in the IP header
> of the

FWIW, I don't think you'll gain a lot from this.  QEMU does not ever
look at a packet beyond the MAC address (and perhaps any vlan tags in
the ethernet header).  That far up the stack is strictly
application/network infrastructure land.

So if your goal is to fuzz test the Linux networking code, then this
approach is fine.  But it's unlikely to do anything useful with QEMU itself.

> packages and send it out to the host and vice versa. I have macvtap setup
> on my host (have tried both VEPA and Bridge mode).

Unless you have an explicit reason to use it, I'd steer away from
macvtap.  It's not commonly used.

> My ssh connection to my guest breaks down after having send just 22
> packets

If you're munging random IP packets, you're going to lose connections
:-)  That's pretty much a given.  I'm not surprised at all it happens
this quickly.

> and also the gnome crashes. I see the following message in the dmesg
>
> dbus[545]: [system] Rejected send message, 2 matched rules;
> type="method_return", sender=":1.0" (uid=0 pid=499
> comm="/usr/lib/systemd/systemd-logind ") interface="(unset)"
> member="(unset)" error name="(unset)" requested_reply="0"
> destination=":1.17" (uid=42 pid=658 comm="/usr/bin/gnome-session -f --debug
> ")

I don't know what this is but if you were doing something like remoting
X over an ssh session, this wouldn't be much of a surprise.

Regards,

Anthony Liguori

>
> The connection to the guest restart but wanted to know what makes it
> breakdown.
>
> Regards,
> Richa Marwaha