On 01/30/2012 08:15 AM, Hendrik Schwartke wrote:
Hi,
calling virDomainNetGetActualBridgeName on a bridge with type
VIR_DOMAIN_NET_TYPE_NETWORK seems to return NULL in any case, because
iface->data.network.actual is NULL. Is that intented?
Yes, that's how it was intended to work. It has a very narrow purpose,
only to be used for interfaces that end up being connected to host
bridges not managed by libvirt (i.e., either the interface type is
VIR_DOMAIN_NET_TYPE_BRIDGE, or the type is NETWORK, and the network has
<forward mode='bridge'>). It's an internal API, so that purpose could
change, but I would need to look and see if that would have any adverse
side effect.
What is the best way to determine the bridge the interface is
connected to?
I'm guessing you're writing the packet sniffing code you asked about the
other day. Do you really want the bridge device that the guest is
connecting to? I think the device you actually want to watch is the tap
device that connects the guest to the bridge. That is in net->ifname
("net" being the virDomainNetDef containing the configuration for the
interface); qemu uses that value directly when setting up the guests'
interfaces.
If you really do need to get the device that the guest tap is connected
to (which might be a bridge, or might be a physical ethernet, or might
be ???), where that is depends on the type of interface:
1) for interface "actualType"=VIR_DOMAIN_NET_TYPE_NETWORK, currently you
would need to call the public API virNetworkGetBridgeName (that requires
you to first call virNetworkLookupByName).
2) for interface actualType=VIR_DOMAIN_NET_TYPE_DIRECT you would want to
call virDomainNetGetActualDirectDev() - this gives you a physical
interface which the guest connects to in one of the mavctap modes.
3) for interface actualType=VIR_DOMAIN_NET_TYPE_BRIDGE you would call
virDomainNetGetActualBridgeName().
Note that in all cases, I'm talking about using the result of
virDomainNetGetActualType(net), *not* just looking at net->type. (the
latter is what's in the config, the former is what is figured out at
runtime based on the config).
(Still, I'm guessing what you really want is just net->ifname).
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