[libvirt] [PATCH] Account for defined networks when generating bridge names

[Cole Robinson]

Daniel P. Berrange wrote:
> On Mon, Feb 16, 2009 at 06:40:59PM -0500, Cole Robinson wrote:
>> diff --git a/src/network_driver.c b/src/network_driver.c
>> index d750565..d83f902 100644
>> --- a/src/network_driver.c
>> +++ b/src/network_driver.c
>> @@ -812,7 +812,12 @@ static int networkStartNetworkDaemon(virConnectPtr conn,
>>          return -1;
>>      }
>>  
>> -    if ((err = brAddBridge(driver->brctl, &network->def->bridge))) {
>> +    if (!network->def->bridge &&
>> +        !(network->def->bridge = virNetworkAllocateBridge(conn,
>> +                                                          &driver->networks)))
>> +        return -1;
>> +
>> +    if ((err = brAddBridge(driver->brctl, network->def->bridge))) {
> 
> This will cause a thread deadlock once you add the locking I describe
> for virNetworkBridgeInUse() in the previous patch. This is because
> the current virNetworkObjPtr 'network'  here will be locked, then
> the function you're calling with then try to lock it again. 
> 
> A deep called function like networkStartNetworkDaemon() shouldn't be
> iterating over all network objects, so this is the wrong place to try
> and fix this problem.
> 
> I'm guessing you're trying to fix up existing defined networks without
> a bridge here, so IMHO, this is better done at daemon startup, where
> we load all the configs off disk. This will avoid the locking trouble
> 
> Do it in 'networkStartup',m just after the virNetworkLoadAllConfigs
> call, but before autostart is done.
> 

Okay, I rolled these changes and the BridgeInUse changes into one patch
(along with Jim's suggestions).

I added a helper function SetBridgeName which basically does:

if user passed bridge name:
  verify it doesn't collide
else:
  generate bridge name

We call this in Define and CreateXML. When loading configs from a driver
restart, we only attempt to generate a bridge: if checking for
collisions failed, the network wouldn't even be defined, which would
only cause more pain for users.

Patch below.

Thanks,
Cole

-------------- next part --------------
A non-text attachment was scrubbed...
Name: libvirt-bridge-collisions-02.patch
Type: text/x-diff
Size: 8373 bytes
Desc: not available
URL: <http://listman.redhat.com/archives/libvir-list/attachments/20090227/1a9b3e67/attachment-0001.bin>