Running a small howm-brewn router with only vanilla and standard FreeBSD on-board utilities on a PCEngines APU2C4, the built-in i210 Intel NICs stop working when they have VLAN tags assigned and enabling "vlanhwtag" on the base device (i.e., igb1 is the main device, igb1.10, igb1.100 and igb1.1000 are the VLAN devices).
This phenomenon/bug seems also present on Intel i350 NIcs (I use a server with a dual port PCIe NIC of that kind).
I have very similar problem: igb/I210, FreeBSD 12-ALPHA8 (r339009).
When I enable "vlanhwtag" on server, clients on this VLAN receive UDP with broken checksums.
For example, client can not obtain address via DHCP from server with enabled "vlanhwtag", because DHCP client doesn't seen answers, because they are dropped by kernel due to invalid checksum: tcpdump sees DHCPOFFER on cleint's interface but dhclient doesn't receive anything.
I'm unclear if this is related to PR231416 or not. There needs to be a bit more clarification in what the vlanhwtag needs to do or if setting this flag somehow breaks what the udp stack is expecting.
(In reply to Sean Bruno from comment #2)
My case is PR231416 for sure. Looks like TCP works with tis capability enabled, for example. I'm not sure about non-bpf originated UDP, though.