[pve-devel] BUG in vlan aware bridge

VELARTIS Philipp Dürhammer p.duerhammer at velartis.at
Tue Oct 12 12:48:22 CEST 2021


i am playing around since days because we have strange packet losses.
Finally I can report following (Linux 5.11.22-4-pve, Proxmox 7, all devices MTU 1500):

Packet with sizes > 1500 without VLAN working well but at the moment they are Tagged they are dropped by the bond device.
Netfilter (set to 1) always reassembles the packets when they arrive a bridge. But they don't get fragmented again I they are VLAN tagged. So the bond device drops them. If the bridge is NOT Vlan aware they also get fragmented and it works well.

Setup not working:

tapX (tagged) <- -> vmbr0 <- - > bond0

Setup working:

tapX (tagged) <- -> vmbr0 <- - > bond0

Setup also working:

tapX < - - > vmbr0v350 < -- > bond0.350 < -- > bond0

Have you got any idea where to search? I don't understand who is in charge of fragmenting packages again if they get reassembled by netfilter. (and why it is not working with vlan aware bridges)

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