[pve-devel] [PATCH qemu-server] add mtu option to virtio-net device

[Alexandre DERUMIER]

>>I really dislike options that only works for specific cases ... 

Seem that it is needed for an user hosted at Hetzners

https://forum.proxmox.com/threads/set-mtu-on-guest.45078/


I think it could also help for vxlan, as we need 50bytes for vxlan, so we need to bump mtu on physical interfaces (1550),
or lowering it on guest. (If network don't support jumbo frame).

But yes, it can be solved too editing the configuration in the guest directly.

The forum user problem was at distro install where he can't choose mtu.


----- Mail original -----
De: "dietmar" <dietmar at proxmox.com>
À: "pve-devel" <pve-devel at pve.proxmox.com>, "aderumier" <aderumier at odiso.com>
Envoyé: Vendredi 31 Août 2018 15:02:03
Objet: Re: [pve-devel] [PATCH qemu-server] add mtu option to virtio-net device

I really dislike options that only works for specific cases ... 

> On August 31, 2018 at 1:11 PM Alexandre Derumier <aderumier at odiso.com> wrote: 
> 
> 
> This allow to setup mtu inside the guest, 
> only working with virtio-net. 
> --- 
> PVE/QemuServer.pm | 8 ++++++++ 
> 1 file changed, 8 insertions(+) 
> 
> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm 
> index 015f8f7..9bfb4a1 100644 
> --- a/PVE/QemuServer.pm 
> +++ b/PVE/QemuServer.pm 
> @@ -715,6 +715,12 @@ my $net_fmt = { 
> description => "Rate limit in mbps (megabytes per second) as floating point 
> number.", 
> optional => 1, 
> }, 
> + mtu => { 
> + type => 'number', 
> + minimum => 576, maximum=> 65536, 
> + description => "MTU (virtio-net only)", 
> + optional => 1, 
> + }, 
> tag => { 
> type => 'integer', 
> minimum => 1, maximum => 4094, 
> @@ -1839,6 +1845,7 @@ sub print_netdevice_full { 
> $tmpstr .= ",vectors=$vectors,mq=on"; 
> } 
> $tmpstr .= ",bootindex=$net->{bootindex}" if $net->{bootindex} ; 
> + $tmpstr .= ",host_mtu=$net->{mtu}" if $net->{mtu} && $device eq 
> 'virtio-net-pci'; 
> 
> if ($use_old_bios_files) { 
> my $romfile; 
> @@ -4619,6 +4626,7 @@ sub vmconfig_update_net { 
> if (&$safe_string_ne($oldnet->{model}, $newnet->{model}) || 
> &$safe_string_ne($oldnet->{macaddr}, $newnet->{macaddr}) || 
> &$safe_num_ne($oldnet->{queues}, $newnet->{queues}) || 
> + &$safe_num_ne($oldnet->{mtu}, $newnet->{mtu}) || 
> !($newnet->{bridge} && $oldnet->{bridge})) { # bridge/nat mode change 
> 
> # for non online change, we try to hot-unplug 
> -- 
> 2.11.0 
> 
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