[Xen-devel] question about guest-to-guest networking

[Aravind Menon <aravind.menon@xxxxxxx>]

As I understand, the network backend driver uses page-remapping to map
packets to be transmitted by the guest domain, and uses page transfer to
transfer page ownership of the packet to be received by the guest
domain.

I was wondering how this would work when one guest domain wanted to
communicate with another guest domain.

The backend driver would remap the packet to be transmitted from the
source guest domain, and then later transfer the ownership of this page
to the target guest domain. However, at the end of transmission, the
source guest domain is notified that it can free the page containing the
network packet.

So, wouldn't this lead to the packet page being owned by the target
domain, while the source domain still believes that it owns the page?

I am referring to a somewhat dated implementation of the network drivers
(Xen version 2.0.6), so I am not aware if this `problem' also exists in
Xen version 3.0.

Any comments or explanations would be helpful.

Thanks,

Aravind



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