Created attachment 205181 [details]
One line patch to set IFCAP_VLAN_MTU capability.
Do not drop the MTU from from 1500 to 1496 bytes when setting up a VLAN.
The chip is already configured for a maximum length of 1518 bytes.
See if_muge.c lines 1135ff at base r348020.
According to my tests adding IFCAP_VLAN_MTU to ifp->if_capabilities fixes this.
See also base r291953 for the same fix at the smsc(4) driver.
A commit references this bug:
Date: Tue Jul 2 16:44:05 UTC 2019
New revision: 349602
if_muge: set IFCAP_VLAN_MTU to maintain 1500 MTU with vlan use
Submitted by: Ralf <email@example.com>
MFC after: 1 week