...and just as an addendum, telnet shows the kind of behaviour I'd expect to see from squid telnet cs.co 80 Trying 2001:4800:13c1:10:222:19ff:fe00:cbb... Trying 67.192.93.178... Connected to cs.co. Escape character is '^]'. On 28/07/14 10:35, Jason Haar wrote: > Hi there > > I'm seeing a reliability issue with squid-3.1.10 through 3.4.6 accessing > ipv6 sites. > > The root cause is that the ipv6 "Internet" is still a lot less reliable > than the ipv4 "Internet". Lots of sites seem to have a "flappy" > relationship with ipv6 which is not reflected in their ipv4 realm. This > of course has nothing to do with squid directly - but impacts it > > So the issue I'm seeing is going to some websites that have both ipv6 > and ipv4 addresses, ipv6 "working" (ie no immediate "no route" type > errors), but when squid tries to connect to the ipv6 address first, it > hangs so long on "down" sites that it times out and never gets around to > trying the working ipv4 address. It also doesn't appear to remember the > issue, so that it continues to be down (ie the ipv6 address that is down > for a website isn't cached to stop squid going there again [for a > timeframe]) > > Shouldn't squid just treat all ipv6 and ipv4 addresses assigned to a DNS > name in a "round robin" fashion, keeping track of which ones are > working? (I think it already does that with ipv4, I guess it isn't with > ipv6?). As per Subject line, I suspect squid needs a ipv6 timeout that > is shorter than the overall timeout, so that it will fallback on ipv4? > > i.e. right now I can't get to http://cs.co/ as their ipv6 address is > down, but their ipv4 address is up and working - but squid won't try it > because it hangs so long trying the ipv6 address (and on the flip-side, > www.google.com is working fine over ipv6). To put it another way, > squid-3.1.10 and newer work fine if the ipv6 address allocated to a site > is up and responding, but cause issues if it is not > -- Cheers Jason Haar Corporate Information Security Manager, Trimble Navigation Ltd. Phone: +1 408 481 8171 PGP Fingerprint: 7A2E 0407 C9A6 CAF6 2B9F 8422 C063 5EBB FE1D 66D1
