Current status of Linux IPv6


Linux supports IPv6 in 2.2.X kernel or later.
Glibc supports IPv6 functions in 2.1.X or later.
Some of tools and applications supports IPv6.

However the quality is....
TAHI Project tested Linux IPv6 stack.
They performed 239 test items.
82 items succeeded, 157 items failed.

For more analysis
http://www.linux-ipv6.org/linux-test-en/