bug#23658: 25.1.50; make-network-connection fails to connect to IPv6 address on Windows

[Ken Brown <kbrown@cornell.edu>]

On 6/1/2016 3:57 PM, Fran wrote:
> Removing the ":nowait t" makes it connect successfully to the IPv6
> address. In that case, it works regardless of whether ":family 'ipv6"
> is present. If this were my personal code that would be a sufficient
> workaround, but I found this bug in ERC (the Emacs IRC client), and I
> think it is designed so that make-network-process has to connect
> asynchronously.

This sounds similar to the situation I faced in bug#23606.  (But in that 
case specifying :family solved the problem).  Here's what I suspect is 
happening:

In src/process.c there's a loop starting at line 3138 in which the code 
runs through a list of possible addrinfo structures in the hopes of 
finding one it can connect to.  In the asynchronous case, it doesn't 
wait to see if the connection is successful; this is only discovered 
later (around line 5495).  At this point it's too late to try another 
addrinfo structure, and a "failed" message is generated (line 5523) if 
the connection didn't succeed.

I think it would be better if the loop would delay making the connection 
asynchronous (line 3160 or 3171) until it's known that the connection 
has succeeded.

Lars, is there any reason not to do it that way?

Ken