[squid-users] Squid doesn't do a fallback from ipv6 to ipv4, if the ipv6 connect fails

[Amos Jeffries]

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On 20/12/2014 2:08 a.m., Dieter Bloms wrote:
> 
> When I do a http://ssl.ratsinfo-online.net/ the fallback from ipv6
> to ipv4 works fine, but when I do a
> https://ssl.ratsinfo-online.net/ squid tries ipv6 only and doesn't
> do a fallback to ipv4.
> 
> I would be nice, if you can try it on your dial stack setup.
> 
> Thank you.
> 

It takes me 10-20 sec to receive any response on the very first DNS
lookup for that domain. After which all responses are quite fast for a
few minutes. Then repeat with the slow lookup.

Like you say it responds with 1 IPv4 and 1 IPv6. Which is not too
many, and none actually failing to resolve. So DNS is reasonable even
with the occasional delay.

I am seeing approx 40-90% packet loss on several of the NTT.net
transit hops between me and the site in IPv4. Not sure if that is
related in any way related to your access path.

My current colo provider blocks network measurements from end-servers
(but only on v6) so I cant adequately test the v6 connectivity
anymore. But your log entry indicates that probably a TCP SYN
handshake did not finish over either IP version.

Amos

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