Re: [PATCH v3 0/2] Reconstruct ICMP headers for failed UDP connect

[Jon Maloy <jmaloy@redhat.com>]

On 2025-02-19 22:47, David Gibson wrote:
> On Wed, Feb 19, 2025 at 02:30:05PM -0500, Jon Maloy wrote:
>> Reconstruct incoming ICMP headers for failed UDP connect and forward back
>> to local peer.
>>
>> 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.
> 

[...]

> "listening" socket.
> 
> The only way I can see to fix this would be to create connect()ed
> sockets for both ends of a flow when we establish it.  I _think_ we can
> have the listening and connected socket concurrently (at least with
> REUSEADDR) with the connect()ed socket taking priority when it
> matches.
> 
> However, it does have a complication: there's a brief time window
> between bind() and connect() on the new socket, when it might pick up
> packets that should go to the original listening socket.  We'd need to
> decide what to do with that case.
> 
> In any case, it kind of looks like there's not much point trying to
> handle error events on the listening socket (beyond a debug()
> message), since I'm not sure such events are ever delivered.
> 

I eliminated the handling of listener sockets ICMPs in my latest version.
I can create a separate connected socket in a separate patch,
if you agree that is the way to go.

///jon