IPv6 MTU discrovery -- how should it work?

[Lev Serebryakov]

Hello, Seth.
You wrote 29 апреля 2012 г., 20:20:54:

SM> Make sure you do not block icmp6. Or atleast make sure that
SM> unreachable and toobig packets come through even if you do not want echo.
 icmp6 enabled in firewall. It seems to be problem in "gif" interface,
which has this words in BUGS section in man page:

     If the outer protocol is IPv4, gif does not try to perform path MTU dis-
     covery for the encapsulated packet (DF bit is set to 0).

     If the outer protocol is IPv6, path MTU discovery for encapsulated pack-
     ets may affect communication over the interface.  The first bigger-than-
     pmtu packet may be lost.  To avoid the problem, you may want to set the
     interface MTU for gif to 1240 or smaller, when the outer header is IPv6
     and the inner header is IPv4.

 I have MTU 1460 on my "outer" interface (it is PPPoE connection to my
 IPv4 provider), and gif0 doesn't allow me to set mtu 1240 on it.


-- 
// Black Lion AKA Lev Serebryakov <lev at FreeBSD.org>