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Date: Wed, 14 Oct 2026 11:40:48 +0200
From: Gabriel Goller <g.goller@proxmox.com>
To: =?utf-8?B?UsOpbWk=?= PAETA <remi.paeta@comaite.com>
Subject: Re: [PATCH qemu-server] fix #6490: network: add bridge fdb entries
 when hotplugging a nic
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On 13.10.2026 11:58, Rémi PAETA wrote:
> [snip]
> diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
> index 74772fdd..4c2bd334 100644
> --- a/src/PVE/QemuServer.pm
> +++ b/src/PVE/QemuServer.pm
> @@ -5126,6 +5126,8 @@ sub vmconfig_update_net {
>                      $newnet->{trunks},
>                      $newnet->{rate},
>                  );
> +                # unplugging the interface dropped its forwarding database entries
> +                PVE::QemuServer::Network::add_nets_bridge_fdb({ $opt => $value }, $vmid);
>  
>              } elsif (safe_num_ne($oldnet->{rate}, $newnet->{rate})) {
>                  # Rate can be applied on its own but any change above needs to
> @@ -5155,6 +5157,7 @@ sub vmconfig_update_net {
>              $newnet->{bridge}, $newnet->{macaddr}, $vmid, $conf->{name},
>          );
>          vm_deviceplug($storecfg, $conf, $vmid, $opt, $newnet, $arch, $machine_type);
> +        PVE::QemuServer::Network::add_nets_bridge_fdb({ $opt => $value }, $vmid);
>      } else {
>          die "skip\n";
>      }

Not a qemu-server expert, but one thing I noticed:

I think we need an eval around the two calls, otherwise when the `bridge fdb
add` fails, the tap interface is created but the hotplug fails (which means we
have a diverging config).

I think we also should relax a bit the del_nets_bridge_fdb() function so that a
missing entry doesn't die (again add an eval around the `bridge fdb del`).

@Fiona what do you think? :)