[Cu-wireless] project: merge Internet-connected, non-Internet connected software

[David Young]

I have some programming I would like to enlist a volunteer to do.

If you've looked recently at our downloads page,
<http://www.cuwireless.net/downloads.html>, you know that we have two
software distributions.  One is for Internet-connected nodes, and the
other is for nodes without an Internet connection.  This is an undesirable
complication from the standpoint of usability and software maintenance.
I want to have one software distribution that can do both: it seeks an
available Internet connection with DHCP, and if it does not find one,
it assigns IP numbers with on the subscriber's net using DHCP.

The nodes used to do this, badly: a wireless node tried *once* to get a
DHCP lease.  If that didn't work, it turned into a DHCP server.  The IMC
node worked that way.  It did the right thing about 90% of the time.
The other 10% of the time, after a power failure or something, the IMC
node would boot up quicker than the DHCP server at IMC, it would try
(and fail) to get a lease, and then turn into a DHCP server.  Disaster!
The node did not advertise an Internet connection, and the two DHCP
servers raced with each other to assign IP numbers to the computers
at IMC.

The old IMC solution was not too far from being correct.  It just
needs to try more than once for a DHCP lease.  There should be a shell
script that runs at boot and "daemonizes" itself.  After it turns into a
daemon, it tries to get a DHCP lease with "dhclient -1."  Failing that,
it starts the DHCP server, dhcpd, sleeps for three minutes, shuts down
dhcpd, dhclient -1's again, starts dhcpd and sleeps for six minutes if
it does not get a lease, and so on, until it sleeps for 96 minutes at a
time before trying again to get a DHCP lease.  In this way, if no DHCP
server is reachable when a node boots, it will still detect a server
that becomes available later.

If dhclient -1 does get a lease, then the script should sleep.  There is
a script called something like /etc/dhclient-exit-hooks that dhclient
calls when events occur (lease received, lease renewed, lease denied,
lease expired).  If a lease expires and renewal fails, then your -hooks
script should wake the script that controls dhclient/dhcpd by, say,
sending it a signal.  The script should start its "try dhclient, run
dhcpd" cycle again.

That's a pretty sophisticated script I have described.  I known from
experience that it needs to be at least that sophisticated.  I don't
think it will take more than about a week to program and test.

Dave

-- 
David Young             OJC Technologies
dyoung at ojctech.com      Urbana, IL * (217) 278-3933