ng_one2many heartbeat algorithm for LAN fault tolerance

[Evgeny Dolgopiat]

Hi all,

The link to the patches and some docs:
http://www.watson.org/~ilmar/download/ng_one2many.tbz

What is it
Link failure determination for one2many netgraph node.
	
How it works
It is implemented as "heartbeat" packet counters on all one2many tranked
interfaces. If the number of packest hook received is less for some
specified value than max number of packest, received by another hooks of the
node, then interface is marked as failed (subnet or link failure). If this
difference is less than this value and interface is marked as failed, then
interface is up and working.

How to setup
Algorithm number is 2, so to configure node one should issue "setconfig 
{xmitAlg=1 failAlg=2}" message for ng_one2many node.

There are two params of algorithm:
	timeout - time between sending of hearbeat packets (integer number of 1/10 
sec)
	period - number of timeouts for failure determination statistics
Default values are timeout=10 and period=10.

Two new node messages: "gethbconfig" and 
"sethbconfig {timeout=X period=Y}" for getting and 
setting heartbeat algorithm params.

Author:	Evgeny Dolgopiat <dolgop at mccinet.ru>