Comment 6 for bug 2002834

Ubuntu 20.04.5 LTS
xen-hypervisor-4.11-amd64 4.11.3+24-g14b62ab3e5-1ubuntu2.3

Reverted back to kernel 5.4.0-135 and bridging with Xen VMs is working again.

Spent the day trying to work out why bridging suddenly stopped working. Guest is 18.04.6 LTS.

I'm pretty sure that under 137, the path cost was 100 for enp6s0f0, instead of the 19 it shows now.

brctl showstp xenbr1
xenbr1
 bridge id 8000.90e2ba065da8
 designated root 8000.90e2ba065da8
 root port 0 path cost 0
 max age 20.00 bridge max age 20.00
 hello time 2.00 bridge hello time 2.00
 forward delay 15.00 bridge forward delay 15.00
 ageing time 300.00
 hello timer 0.00 tcn timer 0.00
 topology change timer 0.00 gc timer 230.64
 flags

enp6s0f0 (1)
 port id 8001 state forwarding
 designated root 8000.90e2ba065da8 path cost 19
 designated bridge 8000.90e2ba065da8 message age timer 0.00
 designated port 8001 forward delay timer 0.00
 designated cost 0 hold timer 0.00
 flags

vif1.0 (2)
 port id 8002 state forwarding
 designated root 8000.90e2ba065da8 path cost 100
 designated bridge 8000.90e2ba065da8 message age timer 0.00
 designated port 8002 forward delay timer 0.00
 designated cost 0 hold timer 0.00
 flags