[libvirt] Possible bug in OpenVZ guest interface name assignment

[ALVARO POLO VALDENEBRO]

Hi,

I think I've found a possible bug in the way OpenVZ is assigning the guest interface names when network is bridged. It's manifested at least in 1.0.5 version and master branch.

As we can see in openvzDomainSetNetwork() function (openvz/openvz_driver.c:822), the field data.ethernet.dev of virDomainNetDefPtr type is used as guest interface name. If not found, then it generates a new one as ethX, calculating the next X value appropriate for the target domain.

That's fine for network types other than VIR_DOMAIN_NET_TYPE_BRIDGE. But with bridged networks, there is no chance to populate data.ethernet.dev from the XML descriptor. We could guest that in such circumstance the code will detect that no name is given to data.ethernet.dev, so it will generate a new one. But that's incorrect. The virDomainNetDef.data field is a union, so data.ethernet.dev and data.bridge.brname are located in the same memory offset. That makes the openvzDomainSetNetwork() function to assign the bridge name as guest interface name every time it's invoked for bridged networks.

Ideally, for bridged networking openvzDomainSetNetwork() should assign a random ethX device name instead of using the bridge name.

Could somebody confirm all this? If so, I could open a new ticket in bugzilla and submit a patch.

Best,

Alvaro Polo Valdenebro
Product Development & Innovation / Telefónica Digital
C/ Don Ramón de la Cruz 82-84
Madrid 28006
(+34) 609 087 054
apv at tid.es


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