[pve-devel] [PATCH common] fix #4547: set MTU on dynamically created vlan bridges

[pve-devel] [PATCH common] fix #4547: set MTU on dynamically created vlan bridges

[Dominik Csapak]

Otherwise the created vlan bridge has the default MTU, which is
unexpected when the original bridge has some other MTU configured.

We already do this for the firewall bridges, so we should do so too for
the vlan bridges.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
technically this is a breaking change i think, since someone might
depend on the fact that the vlan bridges always have the default mtu,
but there is no way to configure that besides from manually modifying
the /etc/network/interfaces file, so not completely sure
if we want to do that now, or with the next major release

 src/PVE/Network.pm | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/PVE/Network.pm b/src/PVE/Network.pm
index 355637b..22ca5b3 100644
--- a/src/PVE/Network.pm
+++ b/src/PVE/Network.pm
@@ -620,6 +620,9 @@ sub activate_bridge_vlan {
 	    iface_create($bridgevlan, 'bridge');
 	}
 
+	my $bridgemtu = read_bridge_mtu($bridge);
+	eval { run_command(['/sbin/ip', 'link', 'set', $bridgevlan, 'mtu', $bridgemtu]) };
+
 	# for each physical interface (eth or bridge) bind them to bridge vlan
 	foreach my $iface (@ifaces) {
 	    activate_bridge_vlan_slave($bridgevlan, $iface, $tag);
-- 
2.30.2

[pve-devel] applied: Re: [PATCH common] fix #4547: set MTU on dynamically created vlan bridges

[Thomas Lamprecht]

On 24/02/2023 12:06, Dominik Csapak wrote:
> Otherwise the created vlan bridge has the default MTU, which is
> unexpected when the original bridge has some other MTU configured.
> 
> We already do this for the firewall bridges, so we should do so too for
> the vlan bridges.
> 
> Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
> ---
> technically this is a breaking change i think, since someone might
> depend on the fact that the vlan bridges always have the default mtu,
> but there is no way to configure that besides from manually modifying
> the /etc/network/interfaces file, so not completely sure
> if we want to do that now, or with the next major release

meh, if we adopt that view on what a breaking change is we wouldn't
be allowed to fix any bug ;-)  

> 
>  src/PVE/Network.pm | 3 +++
>  1 file changed, 3 insertions(+)
> 
>

applied, thanks!