Re: if_vlan allow to set incorrect mtu

From: Marek Zarychta <>
Date: Tue, 07 Dec 2021 09:05:45 UTC
W dniu 7.12.2021 o 10:00, Zhenlei Huang pisze:
>> Can you please disable all vlan hardware offloading features and repeat the test again?
>> ifconfig igb0 -vlanmtu -vlanhwtag -vlanhwfilter -vlanhwtso -vlanhwcsum
> Disabling the capabilities listed above doesn't solve the issue, but assigning mtu 8996 to VLAN children does.
> Reproduced on the most recent 13-STABLE (13-n248421-3b936a8c889) while testing the fix[1]
> Try disabling all vlan hardware offloading features in rc.conf.
> ifconfig_igb0="mtu 9000 -vlanmtu -vlanhwtag -vlanhwfilter -vlanhwtso -vlanhwcsum up"
> ifconfig_igb1="mtu 9000 -vlanmtu -vlanhwtag -vlanhwfilter -vlanhwtso -vlanhwcsum up"

It doesn't change anything. I am using workaround since the early 
transition to 13 branch, but recently conducted small investigation and 
finally submitted the PR[1]


Marek Zarychta