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

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.