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The only downside is that the tinyproxy that sits in Ubuntu 12.04 does not listen on both IPv4 and IPv6 at the same time 
2013-01-04 Shame on me... I didn't test properly , but tinyproxy does work on both protocols 
I assumed that this result:
netstat -tlnpvw | grep tinyproxytcp6 0 0 :::8888 :::* LISTEN 3946/tinyproxy
meant that it didn't listen on v4... but I was wrong.
Listen ::
#This will accept connections on IPv6, but also on IPv4: IPv4-mapped IPv6 addresses are used:
#CONNECT Jan 04 15:29:13 [23566]: Connect (file descriptor 6): host.terena.org [::ffff:192.87.30.2]
Listen 0.0.0.0
# This will listen on IPv4 only
Listen 2001:610:148:dead::666
# This will listen only on the specified IPv6 address. Not nice, but workable.
Hopefully this will be resolved soon...
Coda 2 drops support for IPv6
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