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From: louie@sayshell.umd.edu (Louis A. Mamakos)
Newsgroups: comp.sys.next
Subject: Re: DialUpIP SLIP is available
Message-ID: <1991Jun14.211552.23806@ni.umd.edu>
Date: 14 Jun 91 21:15:52 GMT
References: <1991Jun13.170751.1743@ni.umd.edu> <HARDY.91Jun14125457@golem.ps.uci.edu>
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In article <HARDY.91Jun14125457@golem.ps.uci.edu> hardy@golem.ps.uci.edu (Meinhard E. Mayer (Hardy)) writes:
>I just downloaded and unpacked Louie's beautiful SLIP package.

Thanks!

>Reading part of the documentation I realized the rc.slip requires the hosts's
>and NeXT's IP  numbers.  In our setup at UCIrvine, the server
>issues an IP number when it goes into the SLIP mode. This means that
>either rc.slip needs to be edited before one fires up slip (I can
>imagine a  script using sed doing this), or making the assigned IP
>number into an environment variable which rc.slip reads. 

You are free to reconfigure the address of the slip0 interface at any
time by using the ifconfig command.  The addresses that are specified in
the rc.slip file are only there for convience, and not necessity.  But you
have to configure that addresses somewhere, sometime.  I wouldn't fool with
trying to edit the rc.slip file on the fly or play games with environment
variable.  

The rc.slip file is only intended to be run once (usually at boot
time) to get the /usr/dialupip/bin/diald process started up and
running.  You can set the addresses of the interfaces anytime that you
want.  The diald process is completely ignorant of any IP addresses
which might be assigned to the interfaces; it simply waits for a
message from the kernel driver that says, effectively:

	"bring up interface slip0, I got a packet from address 
	1.2.3.4 going to address 5.6.7.8 with protocol TCP"

where it then checks any access lists that you might have configured.
If it passes the test, it invokes the approprate script file to bring
the interface up.  You could use the access lists to prevent a casual
ICMP echo request (PING) from bringing up the line inadvertantly.  It
doesn't care what the addresses are; just the fact that a packet tried
to be transmitted on the slip interface (because of how the network
routes were set up; see 'netstat -r -n') will cause the interface to
be brought up.

>Our server expects BOOTP to get the number and configure SLIP.
>I have no previous experience with slip and would welcome any advice
>before I start experimenting with it.

Presumably you could write a BOOTP agent to transmit a packet out the
interface.  Any packets transmitted on a slip interface which isn't
active are queued, and transmitted once diald brings the tty up and
turns on the SLIP line discipline.  Thus, you could transmit the BOOTP
packet, which would cause the line to come up and then it would be
transmitted to your SLIP server.

louie