[PATCH 6/5] lxc: skip the netdev autogenerated name counter past existing devices

[Michal Privoznik]

On 12/16/20 9:13 PM, Laine Stump wrote:
> the lxc driver uses virNetDevGenerateName() for its veth device names
> since patch 2dd0fb492, so it should be using virNetDevReserveName()
> during daemon restart/reconnect to skip over the device names that are
> in use.
> 
> Signed-off-by: Laine Stump <laine at redhat.com>
> ---
> 
> I meant to mention this during review of the abovementioned patch, but forgot.
> 
> (NB: a couple days ago I *removed* similar code from this same spot,
> but it was trying to reserve the name of macvlan devices; a macvlan
> device is moved into the container's namespace at startup, so it is
> not visible to the host anyway. This new case is for the 1/2 of a veth
> pair that does remain in the host's namespace
> (type='bridge|network|ethernet' use a veth pair)
> 
> 
>   src/lxc/lxc_process.c | 24 ++++++++++++++++++++++++
>   1 file changed, 24 insertions(+)
> 
> diff --git a/src/lxc/lxc_process.c b/src/lxc/lxc_process.c
> index 0f7c929535..a842ac91c5 100644
> --- a/src/lxc/lxc_process.c
> +++ b/src/lxc/lxc_process.c
> @@ -1640,6 +1640,30 @@ virLXCProcessReconnectNotifyNets(virDomainDefPtr def)
>       for (i = 0; i < def->nnets; i++) {
>           virDomainNetDefPtr net = def->nets[i];
>   
> +        /* type='bridge|network|ethernet' interfaces may be using an
> +         * autogenerated netdev name, so we should update the counter
> +         * for autogenerated names to skip past this one.
> +         */
> +        switch (virDomainNetGetActualType(net)) {
> +        case VIR_DOMAIN_NET_TYPE_BRIDGE:
> +        case VIR_DOMAIN_NET_TYPE_NETWORK:
> +        case VIR_DOMAIN_NET_TYPE_ETHERNET:
> +            virNetDevReserveName(net->ifname);
> +            break;
> +        case VIR_DOMAIN_NET_TYPE_DIRECT:
> +        case VIR_DOMAIN_NET_TYPE_USER:
> +        case VIR_DOMAIN_NET_TYPE_VHOSTUSER:
> +        case VIR_DOMAIN_NET_TYPE_SERVER:
> +        case VIR_DOMAIN_NET_TYPE_CLIENT:
> +        case VIR_DOMAIN_NET_TYPE_MCAST:
> +        case VIR_DOMAIN_NET_TYPE_INTERNAL:
> +        case VIR_DOMAIN_NET_TYPE_HOSTDEV:
> +        case VIR_DOMAIN_NET_TYPE_UDP:
> +        case VIR_DOMAIN_NET_TYPE_VDPA:
> +        case VIR_DOMAIN_NET_TYPE_LAST:
> +            break;
> +        }
> +

I remember Peter being picky about switch()-es and (almost) always he 
wanted me to add the default case with virReportEnumRangeError() despite 
the variable passed to switch() being verified earlier. IIUC his 
reasoning was that if we had a memory being overwritten somewhere it's 
better to error out (I say it's better to crash), but since I don't care 
that much, this could have:

         default:
             virReportEnumRangeError(virDomainNetType, 
virDomainNetGetActualType(net));
             return;


At your discretion.

>           if (net->type == VIR_DOMAIN_NET_TYPE_NETWORK) {
>               if (!conn && !(conn = virGetConnectNetwork()))
>                   continue;
> 

Michal