[PATCH] qemu: match alias when looking for proper <interface> to detach.

[Martin Kletzander]

On Wed, Feb 10, 2021 at 04:33:21PM -0500, Laine Stump wrote:
>Previously we only checked MAC address and PCI address (or CCW
>address). This is not enough information in cases where PCI address
>isn't provided and multiple interfaces have the same MAC address (for
>example, a virtio + hostdev "teaming" pair - their MAC addresses are
>always the same).
>
>Resolves: https://bugzilla.redhat.com/1926190
>Signed-off-by: Laine Stump <laine at redhat.com>
>---
>
>Arguably, it would be nice to overhaul the device matching used for
>virDomainDeviceDetach for *all* the device types, as they could all be
>matched by looking at alias (and PCI address, for that matter). On the
>other hand, for all other device types there are already enough fields
>being matched to assure a unique match even without looking at
>alias/PCI address, and this patch is intended to fix a current problem
>being experienced in the wild, meaning it's likely that it will need
>to be backported to stable branches, and I'd rather not force
>backporting a sweeping change to stable branches just to bring in a
>fix for one corner case)
>

At first I thought this could be taken into account if and only if there were
multiple mac addresses, but it looks like all the other cases that could fail
are already taken care of, so it makes sense the way it is written.

Reviewed-by: Martin Kletzander <mkletzan at redhat.com>

>
> src/conf/domain_conf.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
>index 07e6f39256..8f2207bdf6 100644
>--- a/src/conf/domain_conf.c
>+++ b/src/conf/domain_conf.c
>@@ -16431,6 +16431,11 @@ virDomainNetFindIdx(virDomainDefPtr def, virDomainNetDefPtr net)
>                                             &net->info.addr.ccw))
>             continue;
>
>+        if (net->info.alias &&
>+            STRNEQ_NULLABLE(def->nets[i]->info.alias, net->info.alias)) {
>+            continue;
>+        }
>+
>         if (matchidx >= 0) {
>             /* there were multiple matches on mac address, and no
>              * qualifying guest-side PCI/CCW address was given, so we must
>-- 
>2.29.2
>
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