[Xcb] [PATCH] Bug: Can’t connect to localhost without global connectivity

[Rémi Denis-Courmont]

Le lundi 15 août 2011 18:45:02 Jamey Sharp, vous avez écrit :
> p.s. I'm not even sure why flags like this exist. Seems like it should
> be site policy, never per-application policy. How is the application
> supposed to know?

The whole point of the flag is to not try addess families that are expected to 
fail anyhow.

In the old days, the "default on-link" assumption in IPv6 made the flag vey 
much indispensable for dual-stack hosts on IPv4-only networks. Without it, 
there would be long timeouts trying non-existent IPv6 connectivity. Nowadays, 
this assumption has been flagged as historic bad practice by IETF, and hosts 
should have been updated to not make it anymore.

Then AI_ADDRCONFIG became mostly cosmetic: it avoids phony "Protocol family 
not supported" or "Host unreachable" errors while trying to connect to a dual-
stack mode from a host with no support for source address selection.

Nowadays, on up-to-date systems, this flag is completely useless. Then again,  
I understood only the very latest MacOS release is "up-to-date" with this 
definition.

-- 
Rémi Denis-Courmont
http://www.remlab.net/
http://fi.linkedin.com/in/remidenis