On Mon, Mar 03, 2025 at 08:29:11PM -0500, Jon Maloy wrote:
> v2: - Added patch breaking out udp header creation from function
>       tap_udp4_send().
>     - Updated the ICMP creation by using the new function.
>     - Added logics to find correct flow, depending on origin.
>     - All done after feedback from David Gibson.
> v3: - More changes after feedback from David Gibson.
> v4: - Even more changes after feedback from D. Gibson
> v5: - Added corresponding patches for IPv6
> v6: - Fixed some small nits after comments from D. Gibson.
> v7: - Added handling of all rejected ICMP messages
>     - Returning correct user data amount if IPv6 as per RFC 4884.
> v8: - Added MTU to ICMPv4 ICMP_FRAG_NEEDED messages.
>     - Added ASSERT() validation to message creation functions.
> v9: - Using real source address of ICMP to complement destination
>       address for originial UDP message when needed.

I think the changes for this are fine as far as they go.  It does
raise an additional wrinkle for when we try to do this for "listening"
sockets: since the ICMP may be coming from somewhere other than the
destination of the triggering message, we can't rely on the source
address to find the correct flow.  I think we'll need to use
EE_OFFENDER() to get the information we need, which will also mean
extended our cmsg buffers a bit: looks like the kernel puts a sockaddr
after the extended_err structure.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson