Why do we still need IPv4 when we are migrating to IPv6...

Phil Mayers p.mayers at imperial.ac.uk
Fri Feb 13 15:32:43 CET 2015

On 13/02/15 14:22, Steinar H. Gunderson wrote:
> On Fri, Feb 13, 2015 at 02:12:31PM +0000, Phil Mayers wrote:
>> As above, depends on how they're using the socket API. As a rule for
>> UDP connections, you actually have to put *more* work in to see ICMP
>> errors. It's certainly possible to ignore them.
> FWIW, at least on Linux, if you keep doing send() on an UDP connection where
> the other end sends ICMP destination unreachable, you'll get errors back
> (ECONNREFUSED) eventually, although typically not on every packet you send.

Quite right, sorry - I'm forgetting that. Whether the app code even 
*look* at the return value of send() on a UDP socket is another matter ;o)

I'd hope NAT traversing apps will know to ignore this, at least during 

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