PPP support

[Igor Khavkine <i_khavki@alcor.concordia.ca>]

I decided to take a look at pppd sources and see what would need to be done
to port it. From first glance, the platform dependent parts of the code deal 
with the following: add an entry to the network interface table, get low level 
info from the interface, send/receive data from an interface and configure the 
tty (the serial port, or anything that emulates it like a pppoe daemon).

First what's completely lacking in pfinet is the ability to add and configure 
new interfaces, like for a second network card for example. The file 
hurd/pfinet.defs contains a stub for such a call, but I didn't see it 
implemented anywhere. Also the only type of interfaces that's supported by 
pfinet is ethernet and loopback. This functionality will have to be 
implemented any way in order to support utilities like ifconfig.

A thought that crossed my mind was instead of trying to add support for ppp0 
like interfaces to pfinet, one could support a generic "tunneling" interface 
that would be used as a bridge between the linux networking code in pfinet and 
an outside daemon like pppd or a translator.

Aside from the above, would there be any other problems in the way of porint 
pppd? I remember that gnumach was lacking support for character devices (or 
something simmilar) which was needed by ppp, is that still the case?

Igor