[PATCH] net: fix IPv4 cksum simple function

[Morten Brørup]

> From: Robin Jarry [mailto:rjarry at redhat.com]
> Sent: Tuesday, 5 November 2024 10.37
> 
> Morten Brørup, Nov 05, 2024 at 10:09:
> > For consistency, could one of you - David or Robin - please also
> > 2-byte align the IPv6 header structure?
> 
> I can send a patch but I wonder if this is really necessary after the
> RC-1 has passed?

Yes, please.
And don't forget the extension headers (rte_ipv6_routing_ext and rte_ipv6_fragment_ext).

> 
> We don't have any gcc warning related to IPv6 unaligned access (except
> maybe in drivers).

I think both IPv4 and IPv6 headers are always 2-byte aligned IRL; so for consistency and to prevent potential future problems, the API should reflect this.

Consistency is important: If the alignment differs between IPv4 and IPv6 headers in the API, someone might think there is a good reason for this, and as time passes no one will be able to answer why there is a difference.

PS:
I am also pushing for 2-byte aligning Layer 4 headers (TCP, UDP, etc.), e.g. for checksumming purposes; but didn't get enough response to that RFC:
https://inbox.dpdk.org/dev/20241011160653.88028-1-mb@smartsharesystems.com/