6to4/SIT and IP DF

I was trying out 6to4 and noticed that the v4 encapsulating header has DF
set, which RFC3056 says should not be set.

Because ICMPv4 won't, in general, include enough packet to determine the
original v6 sender, end-to-end PMTU won't work. The possible use I could
see is if the tunnel MTU is modified based on the PTMU (I didn't check),
but  that's probably not a good idea for any tunnels  that have "any" as
the remote v4 address. Doing that would force all MTU's to the lowest of
any v4 destination's path.

So, I think it's appropriate to always clear IP DF in the IPv4 header
generated by SIT, but I thought I'd see if anyone else has a comment on
that before I submit the trivial patch. :-)

Any thoughts?

            +-DLS