Add skb_csum_offload_chk driver helper function to determine if a
device with limited checksum offload capabilities is able to offload the
checksum for a given packet.
This patch includes:
- The skb_csum_offload_chk function. Returns true if checksum is
offloadable, else false. Optionally, in the case that the checksum
is not offloable, the function can call skb_checksum_help to resolve
the checksum. skb_csum_offload_chk also returns whether the checksum
refers to an encapsulated checksum.
- Definition of skb_csum_offl_spec structure that caller uses to
indicate rules about what it can offload (e.g. IPv4/v6, TCP/UDP only,
whether encapsulated checksums can be offloaded, whether checksum with
IPv6 extension headers can be offloaded).
- Ancilary functions called skb_csum_offload_chk_help,
skb_csum_off_chk_help_cmn, skb_csum_off_chk_help_cmn_v4_only.
Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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