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

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.