Steve> Look for "active-filter-in" and possibly
Steve> "active-filter-out". These allow you to specify which types of
Steve> packets should be ignored when deciding if the link is idle.

Martin> Unfortunately the in-kernel (if_spppsubr.c based) PPP
Martin> interfaces do not have such an option.

Would it make sense for the kernel to use the async PPP code for sync
PPP (and PPPoE)? It seems a little wasteful of effort to maintain two
PPP stacks (including 2 separate LCP, IPCP & authentication
layers). Of course, the cisco HDLC stuff would have to remain separate
from the async PPP stuff. Besides the more featureful on-demand
dialing, the sync PPP would also gain PPP compression.

If I remember correctly, this was considered as an option when the
ISDN code first made it into NetBSD. One problem mentioned at the time
was finding a way of passing the control packets between the kernel
and the userland PPP daemon. How about creating a pppctl cdev for
this?

- S