Re: [lwip-users] add ICMP Destination unreachable

[Leon Woestenberg]

Hello Andreas,

Andreas Becker wrote:
> Hi all,
>
> I'm thinking about to extend LWIP with the processing of a 
> ICMP-destination-unreachable Message.
Just to make sure we understand: you mean handling incoming
ICMP destination unreachable messages?

I would really investigate how the BSD stack handles this.

My first idea would be to have a route cache (identical to
the ARP cache) that holds IP addresses that got ICMP
unreachable, with entries like these:

<dest address>,<dest port>,<flags>

flags = { dest_unreachable, port_unreachable }

<dest port> only is used if (flags & port_unreachable)


I was already thinking about how to add outgoing ICMP
dest unreachable messages BTW.

I dislike implementing callbacks into user space for things that
the stack should handle, btw. This burdens a lot of complexity
on the application, whereas unreachable destinations can be
as simple as a return code indicating so.

Regards,

Leon.