Just wondering if anyone has techniques for working around MTU
problems on a NetBSD router. Specifically, I'm interested in
at least one of the following for transit traffic into a tunnel:
  a. clamping MSS on initial SYN
  b. clearing the DF flag
Newer versions of IOS can do this sort of thing.

Searching has revealed tcpmssd for FreeBSD
  http://www.freebsd.org/cgi/pds.cgi?ports/net/tcpmssd
an orphan posting on the ipfilter list
  http://false.net/ipfilter/2000_11/0184.html
and Itojun's fix for NetBSD client(s)
  http://mail-index.netbsd.org/tech-net/2001/05/01/0002.html

Background - we are having very good results multihoming two sites to
the Internet using NetBSD and Zebra's bgpd. We use a gif tunnel for
the iBGP session between exit routers over private inter-site links.
This is fine except for occasional instances of MTU black-holing
(rfc2923, etc.) which we would like to resolve. Of course the
idealogically pure solution is to LART the remote admins...

TIA.