Strange problems with tunnel's MTU on FreeBSD

[blacklion]

I have HE tunnel configured for my home network (gateway is FreeBSD). MTU on "gif0" interface is 1280, and my IPv4 internet connection is PPPoE, so "outer" IPv4 interface has MTU 1460.

Also, I have some servers with native IPv6 (Hetzner.de dedicated servers provider).

And I have problems with bulk transfer from servers to my home network: it stalls. Server sends 1420-byte packets (according to tcpdump), and nothing is received on gateway of my local network.

But, what is strange, ping6 with packet size 1420 works!

What should I do to fix this problem?

[broquea]

Log into the broker and try setting the MTU on HE's side of the tunnel to something other than 1480.

[blacklion]

Oh, I missed this option. Thank you!

But it seems to be workaround for bug in FreeBSD, IMHO, gif tunnel should work in such situation automatically...