I have also had this problem. OpenBSD is using a very old version of ppp which don't support peerdns. I've solved this by updating to version 2.4.7. (not to hard) and updated the ppp(4) in the kernel accordingly. I've done that based on obsd ver 5.7 so my patches are maybe a little out of date.
-- Sent from: http://openbsd-archive.7691.n7.nabble.com/openbsd-user-misc-f3.html
