From owner-freebsd-net@freebsd.org  Thu Mar 16 18:26:31 2017
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Date: Thu, 16 Mar 2017 19:26:19 +0100
From: Harry Schmalzbauer <freebsd@omnilan.de>
Organization: OmniLAN
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Subject: if_igb(4) VLAN(4) and [RT]XCSUM_IPV6, TSO6
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 Hello,

I'm wondering if I really loose [RT]XCSUM_IPV6 on if_igb(4) vlan(4)
children.
My igb0 (Kawela, aka 82576) options end with
  "TSO6,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6"

The vlan(4) filtered interfaces show these:
  options=303<RXCSUM,TXCSUM,TSO4,TSO6>

So TSO6 is inherited, but RC/TXCSUM_IPV6 dropped?

In general, how is offloading implemented? If enabled, does the API
simply generate packets lacking the checksum header and NIC (silicon)
fills in the checksum if not adviesd not to do so (by the driver)?
Or is the driver utilizing NIC registers for calculation, but ensures
every packet will have a checksum?

Thanks,

-harry