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

On Thu, Feb 19, 2015 at 03:58:30PM -0700, Jim Fehlig wrote: > 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. > Is that true for libvirt generally (all drivers)? > Back to virDomainHasNet? :-) Or checking for the > duplicate directly in libxlDomainAttachNetDevice()? > What do you mean by "directly"? This is exactly what my patch did (until virDomainNetFindIdx stopped reporting duplicates).