Re: [libvirt] [PATCH 07/10] libxl: prevent attaching multiple netdevs with the same MAC

Marek Marczykowski-Górecki wrote: > On Thu, Feb 19, 2015 at 03:10:13PM -0700, Jim Fehlig wrote: >> Jim Fehlig wrote: >>> Marek Marczykowski-Górecki wrote: >>>> On Thu, Feb 19, 2015 at 01:58:02PM -0700, Jim Fehlig wrote: >>>>> Marek Marczykowski-Górecki wrote: >>>>>> On Thu, Feb 19, 2015 at 11:43:15AM -0700, Jim Fehlig wrote: >>>>>>> Marek Marczykowski-Górecki wrote: >>>>>>>> It will not be possible to detach such device later. Also improve >>>>>>>> logging in such cases. >>>>>>>> >>>>>>>> Signed-off-by: Marek Marczykowski-Górecki <marmarek(a)invisiblethingslab.com&gt; >>>>>>>> --- >>>>>>>> src/libxl/libxl_driver.c | 41 +++++++++++++++++++++++++++++++++++++++-- >>>>>>>> 1 file changed, 39 insertions(+), 2 deletions(-) >>>>>>>> >>>>>>>> diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c >>>>>>>> index ce3a99b..005cc96 100644 >>>>>>>> --- a/src/libxl/libxl_driver.c >>>>>>>> +++ b/src/libxl/libxl_driver.c >>>>>>>> @@ -2787,6 +2787,7 @@ libxlDomainAttachNetDevice(libxlDriverPrivatePtr driver, >>>>>>>> int actualType; >>>>>>>> libxl_device_nic nic; >>>>>>>> int ret = -1; >>>>>>>> + char mac[VIR_MAC_STRING_BUFLEN]; >>>>>>>> >>>>>>>> /* preallocate new slot for device */ >>>>>>>> if (VIR_REALLOC_N(vm->def->nets, vm->def->nnets + 1) < 0) >>>>>>>> @@ -2801,6 +2802,14 @@ libxlDomainAttachNetDevice(libxlDriverPrivatePtr driver, >>>>>>>> >>>>>>>> actualType = virDomainNetGetActualType(net); >>>>>>>> >>>>>>>> + /* -2 means "multiple matches" so then fail also */ >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> No longer true after commit 2fbae1b2. I think you just want to check if >>>>>>> virDomainNetFindIdx() >= 0, meaning the def already contains a net >>>>>>> device with the same mac address. >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>> But here the error is when the device *is* found, so the opposite case >>>>>> than already reported as an error by virDomainNetFindIdx. >>>>>> >>>>>> >>>>>> >>>>> If you find an idx >= 0, then the domain def already contains a net >>>>> device with the same mac address, right? In that case, you report an >>>>> error and return failure from libxlDomainAttachNetDevice(). >>>>> >>>>> >>>>> >>>> Right, but if I do not find one (idx == -1), I will proceed with >>>> (possibly successful) adding the device, while the error was already >>>> reported by virDomainNetFindIdx. >>>> >>>> >>>> >>> Ah, right :-/. >>> >>> Another option: introduce virDomainHasNet() to detect if the domain def >>> already contains the net device. >>> >>> >> A better option would be to fix this in libxl, for the benefit of other >> libxl apps. >> > > Actually libxl has no problem with duplicated mac addresses, its libvirt > that makes problem. Yeah, it appears duplicate mac addresses are only valid if on different PCI devices.

Back to virDomainHasNet? :-) Or checking for the duplicate directly in libxlDomainAttachNetDevice()?