On Mon, 2017-02-27 at 07:11 -0800, Tom Herbert wrote:

CHECKSUM_PARTIAL is the preferred mechanism on the transmit path this
defers defers the checksum computation as long as possible.
Unfortunately, if SCTP is encapsulated in UDP we will probably need to
run the SCTP CRC on the host which will be done with your changes to
skb_checksum_help.

right. Tunnel devices have NETIF_F_SCTP_CRC bit cleared and
NETIF_F_HW_CSUM bit set: so, in this case csum_not_inet can help
recovering non-GSO SCTP packets having ip_summed equal to
CHECKSUM_PARTIAL.

quoted

I'm not sure if setting CHECKSUM_UNNECESSARY fits my case, because this would
implicitly skip RX validation when using devices like veth or loopback.

CHECKSUM_UNNECESSARY can be used in the transmit path (really the
forwarding path), however this I think this must imply that the
checksum in the packet must be correct. Please see my post about
drivers that are mistakingly using CHECKSUM_UNNECESSARY with LRO since
the checksum in the packet sent into the stack is not correct.

Ok, now I'm more convinced to use CHECKSUM_NONE :-)

thank you for the attention!
regards