Bug in transmitting packages between 6to4 networks

What steps will reproduce the problem?

Packages from one 6to4 network to another 6to4 network, e.g. from
2002:0102:0304:: to 2002:0506:0708:: are sent directly by relay server
1.2.3.4 to relay server 5.6.7.8, not by default gw 192.88.99.1. 

While when using as 6to4, TB-TUN wrongly restricted the source IPv4 address
to the default gw's(192.88.99.1) when receiving 6in4 packages. Causing
packages from other 6to4 networks to TB-TUN been dropped. 

What is the expected output? What do you see instead?

from 2002:xxxx:xxxx::xxxx:xxxx(Using linux tunnel) pinging
2002:yyyy:yyyy::yyyy:yyyy(Using TB-TUN)
Request timed out.

Please use labels and text to provide additional information.

According to RFC 3964, 6to4 routers and relays should ensure that:

    * either or both the source and destination addresses of any
encapsulated packet is within the 6to4 IPv6 prefix 2002::/16,
    * if the source IPv6 address is a 6to4 IPv6 address, its corresponding
6to4 router IPv4 address matches the IPv4 source address in the IPv4
encapsulation header,
    * similarly, if the destination IPv6 address is a 6to4 IPv6 address,
its corresponding 6to4 router IPv4 address matches the IPv4 destination
address in the IPv4 encapsulation header.

So address corresponding check should be added.

Tunnelbroker(Using TB-TUN with a specified relay server and static IPv6
address, such as tunnel porvided by http://tunnelbroker.net/) is not
affected by this bug.

Original issue reported on code.google.com by lostrive...@gmail.com on 5 Jun 2010 at 3:55

nomagick / tb-tun

Bug in transmitting packages between 6to4 networks #3