facebook/facebook-php-sdk — pull request #28 by psaab (2012-06-20 09:11:49+00:00)
Title: Fallback to IPv6 when there's no Global Scope IPv6 connectivity

Hosts which have IPv6 enabled, but no IPv6 connectivity will attempt to fall back to IPv6 if IPv4 connections fail and will get back an error 'Network is unreachable'. Handle this case and retry over IPv6 only rather than provide a cryptic message