[Cu-wireless] [dyoung@che.onthejob.net: SO_DONTROUTE clashes with arpresolve(9)]

[David Young]

All,

I figured out what would crash a workstation in one room when we screwed
on an antenna in the other room.  That was an easy bug to fix, but as
so often happens, one bug helps expose another:

Dave

----- Forwarded message from David Young <dyoung at che.onthejob.net> -----

Date: Tue, 19 Nov 2002 21:39:18 -0600
From: David Young <dyoung at che.onthejob.net>
To: tech-net at netbsd.org
Subject: SO_DONTROUTE clashes with arpresolve(9)
Reply-To: dyoung at pobox.com
Mail-Followup-To: David Young <dyoung at che.onthejob.net>,
	tech-net at netbsd.org
User-Agent: Mutt/1.2.5i


arpresolve(9) negates the effect I expect from SO_DONTROUTE when I try
to send a packet to a host with a non-local route. E.g.,

  # warning: do not run this before you read the whole e-mail
  ifconfig tlp0 inet 63.146.38.214/27
  route add -host 63.146.38.211 63.146.38.208
  ping -rn 63.146.38.211

makes the kernel log this:

  Nov 19 20:49:59 noam /netbsd: arplookup: unable to enter address for 63.146.38.211 at 01:01:e3:f5:3f:92:26:d6 on (null) (host is not on local network)
  Nov 19 20:49:59 noam /netbsd: arpresolve: can't allocate llinfo on tlp0 for 63.146.38.211

No ping reply is ever received, because no ping requests are ever sent,
because ARP never sends a request for 63.146.38.211. Darn.

(There is a worse bug than that: if you run the commands above, your
kernel will panic.  I will commit my one-line fix momentarily.)

This bug has an enormous impact on the multi-hop wireless network I am
building, so I urgently need to fix it. If you have any suggestions for
a fix, I am all ears.

Dave

-- 
David Young             OJC Technologies
dyoung at ojctech.com      Engineering from the Right Brain
                        Urbana, IL * (217) 278-3933

----- End forwarded message -----

-- 
David Young             OJC Technologies
dyoung at ojctech.com      Engineering from the Right Brain
                        Urbana, IL * (217) 278-3933