To: '' <>
From: Sundstrom, Per <>
List: tech-net
Date: 05/02/2000 23:20:29

We have a need for a daemon based arp resolver in a firewall-like
application where we need to have full control over the arp resolution.

The idea is to 
  1) set the interface to 'ifconfig -arp'
  2) set the interface route to XRESOLVE and 
  3) use the routing sockets RTM_RESOLVE messages to
      get notification on misses and finally
  4) use the routing sockets LL address RTM_ADD to set the MAC address
      on the route after the daemon has somehow gotten hold of it.

Now, there are a few things in the networking code that breaks
this idea.

  a) the ifconfig -arp sets the IFF_NOARP flag but this is not honored
      in the code.

  b) there is currently no syncronization between a RTM_RESOLVE
      and a corresponding RTM_ADD resulting in a drop of the first
      packet sent to a specific IP address.

Suggested solution:

  Add checks for the IFF_NOARP in the arp code. 
  Move the generation of RTM_RESOLVE for interface routes to
  Use 'llinfo_arp.la_hold' to hold the pending packet and match that
  on a RTM_ADD with a LL address.

What do you think ? Doable, feasable or just plain dumb ?...