tcp: Encode checksum computation flags in a single parameter

tcp_fill_headers() takes a pointer to a previously computed IPv4 header
checksum to avoid recalculating it when the payload length doesn't
change, and a separate bool to skip TCP checksum computation.

Replace both parameters with a single uint32_t csum_flags that encodes:
- IP4_CSUM (bit 31): compute IPv4 header checksum from scratch
- TCP_CSUM (bit 30): compute TCP checksum
- IP4_CMASK (low 16 bits): cached IPv4 header checksum value

When IP4_CSUM is not set, the cached checksum is extracted from the low
16 bits.  This is cleaner than the pointer-based approach, and also
avoids a potential dangling pointer issue: a subsequent patch makes
tcp_fill_headers() access ip4h via with_header(), which scopes it to a
temporary variable, so a pointer to ip4h->check would become invalid
after the with_header() block.

Suggested-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Jon Maloy <jmaloy@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

0 files changed, 0 insertions, 0 deletions