Every once in a while I get a panic in exit1() when a pppd exits.

It appears that for some reason sp->s_ttyvp != 0 but sp->s_ttyp == 0.
The SESS_LEADER() test passes, and sp->sp_ttyvp is != 0, but
sp->s_ttyp == 0.  I can't see how this can happen...

The pppd does make the serial device the controlling terminal (so it
will get SIGHUPs), so the sp_ttyvp should point to the specfs vnode
for the serial device.  I don't understand how the s_ttyp can end up
zero.

I thought it might be possible that setting the process group after
settting the controlling terminal might cause this, but examing the
code did not bear this out.

[I am running a slightly modified pppd which allows one to point to a
different interface than ppp0, ppp1, etc... and I'm using an SDL
communications sync card.  I plan to put the SDL driver up for anon
ftp shortly.]

-brad