On 2/3/20 6:29 AM, Alexandre DERUMIER wrote: > Hi, > sorry to bump this thread, but I'm seeing users requesting this on the forum, > and I think I'll need it too for vxlan setup, when users can't increase the > mtu on physical interfaces > (and so, need to reduce it in the vms) > > > >>> As far as I can see, the guest sets the MTU to 1500 on the virtio >>> interface, unless qemu explicitly sets host_mtu for the adapter being >>> created, regardless of the MTU of the tap interface on the host. >>> This is essentially the normal behavior of the operating system and the >>> virtio driver if no additional information about the host system is >>> passed on. > >>> Thus, I think in the future it would be logical to add a patch that >>> would install host_mtu explicitly if the tap interface on the host >>> system is set to MTU different from 1500. The tap interface itself >>> inherits the MTU from the bridge interface in which it is "connected". > > I can adapt the patch to map the mtu in guest, to mtu of bridge/tap. > > >>> + mtu => { >>> + type => 'number', >>> + minimum => 576, maximum=> 65536, > > Not sure, is it possible to add an extra "1" value for "auto" ? > > or maybe, do we want to force it, if bridge mtu is < 1500 ? > (as guest mtu is 1500 by default, it will break anyway if bridge mtu < 1500)
sounds OK to me. We may also want to die for non virtio-net devices, as it won't silently work and that could be possibly confusing for users.. _______________________________________________ pve-devel mailing list pve-devel@pve.proxmox.com https://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-devel