I work for a very large corporation. That sort of companies is not inherently evil, but it is both powerful and soulless – a dangerous combination. Thus when dealing with it, better err on the side of caution. For that reason, all of my browsing from the obligatory corporate Microsoft Windows workstation is done trough a SSH tunnel established using Putty to a trusted host and used by Mozilla Firefox as a SOCKS proxy. If you do that, don’t forget to set network.proxy.socks remote DNS to true so that you don’t leak queries to the local DNS server.
In addition to the privacy benefits, a tunnel also gets you around the immensely annoying arbitrary filtering or throttling of perfectly reasonable sites which mysterious bureaucracies add to opaquely managed exclusion lists used by censorship systems. The site hosting the article you are currently reading is filtered by the brain-damaged Websense filtering gateway as part of the “violence” category – go figure !
Anyway, back on topic – this morning my browsing took me to Internode’s IPv6 site and to my great surprise I read “Congratulations! You’re viewing this page using IPv6 ( 2001:470:1f12:425::2 ) !!!!!”. A quick visit to the KAME turtle confirmed : the turtle was dancing. The surprising part is that our office LAN is IPv4 only and the obligatory corporate Microsoft Windows workstation has no clue about IPv6 – how could those sites believe I was connecting through IPv6 ? A quick ‘dig -x 2001:470:1f12:425::2’ cleared the mystery : the reverse DNS record reminded me that this address is the one my trusted host gets from Hurricane Electric’s IPv6 tunnel server.
So browsing trough a SOCKS proxy backed by a SSH tunnel to a host with both IPv4 and IPv6 connectivity will use IPv6 by default and IPv4 if no AAAA record is available for the requested address. This behaviour has many implications – good or bad depending on how you look at it, and fun in any case. As we are all getting used to IPv6, we are going to encounter many more surprises such as this one. From a security point of view, surprises are of course not a good thing.