On Tue, Aug 27, 2019 at 09:46:38PM -0400, Laine Stump wrote:
> libvirt creates its tap devices without the IFF_PERSIST flag, so they
> will be automatically deleted when qemu is finished with them. In the
> case of tap devices created outside of libvirt, if the creating entity
> wants the devices to be deleted, it will also omit IFF_PERSIST, but if
> it wants them to remain (e.g. for re-use), then it will use
> IFF_PERSIST when creating the device.
>
> Back when support was added for autocreation by libvirt of tap devices
> for <interface type='ethernet'> (commit 9c17d665), code was mistakenly
> put in qemuProcessStop to always delete tap devices for
> type='ethernet'. This should only be done on platforms that have
> VIR_NETDEV_TAP_REQUIRE_MANUAL_CLEANUP #defined (which is only
> FreeBSD).
This isn't right. The tap devices should *always* be deleted as we
don't trust that QEMU hasn't (possibly maliciously) set IFF_PERSIST
itself.
>
> This mistake has been corrected, along with the unnecessary check for
> non-null net->ifname (it must always be non-null), and erroneous
> VIR_FREE of net->ifname.
There could be a risk of net->ifname being NULL if qemuProcessStart
fails early in startup before all tap devices have finished being
created IIUC.
>
> Signed-off-by: Laine Stump <laine@xxxxxxxxxx>
> ---
> src/qemu/qemu_process.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
> index 11c1ba8fb9..3449abf2ec 100644
> --- a/src/qemu/qemu_process.c
> +++ b/src/qemu/qemu_process.c
> @@ -7548,10 +7548,10 @@ void qemuProcessStop(virQEMUDriverPtr driver,
> cfg->stateDir));
> break;
> case VIR_DOMAIN_NET_TYPE_ETHERNET:
> - if (net->managed_tap != VIR_TRISTATE_BOOL_NO && net->ifname) {
> +#ifdef VIR_NETDEV_TAP_REQUIRE_MANUAL_CLEANUP
> + if (net->managed_tap != VIR_TRISTATE_BOOL_NO)
> ignore_value(virNetDevTapDelete(net->ifname, net->backend.tap));
> - VIR_FREE(net->ifname);
> - }
> +#endif
> break;
> case VIR_DOMAIN_NET_TYPE_BRIDGE:
> case VIR_DOMAIN_NET_TYPE_NETWORK:
> --
> 2.21.0
>
> --
> libvir-list mailing list
> libvir-list@xxxxxxxxxx
> https://www.redhat.com/mailman/listinfo/libvir-list
Regards,
Daniel
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