From: Judson Lester <judson@...2.com>
Date: 2002-10-25T02:44:04+09:00
Subject: Trouble with UDPSocket



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I've been fooling with a script to multiplex two snmp servers on one box.  The 
idea is to have xinetd connect to the script, and the script pass the packets 
on to servers in order until one of them can respond.  The script is 
attached.  This is running on a Linux box with Ruby 1.6.7.

This isn't working, even with the single existing server.  Normally, if you do 
an snmpget for OID 0, the response is that there is no such OID.  Ditto with 
0.0.  However, with the script in place, OID 0 gets no answer from the 
server, OID 0.0 hangs until OID 0 is sent, then I get an answer, but the 
script hangs in the decode (gleefully borrowed from the SNMP package from 
RAA).  Honestly, I'm not sure if this is a problem with xinetd, my script 
(and so the province of this list), or something with the server itself.  
But, xinetd seems to be behaving properly (from the log review of done if 
it), and the server responds as expected without the script in place.

Can anyone see any obvious errors I'm making?



-- 
Judson
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#!/usr/bin/ruby

require 'socket'
require 's2nmp'


def main()
	snmp = SNMPForward::new
#Add servers to forward to here
	snmp.addServer("localhost", 161)

	snmp.passAlong
end


class SNMPForward

	include Ber

	def initialize
		@snmpServers=Array::new
	end

	public
	def addServer (host, port)
		newServer=UDPSocket::new
		newServer.connect(host, port)

		@snmpServers << newServer
	end

	class SNMPSuccessException < Exception
	end

	def passAlong ()
		log=File::new("/tmp/snmp-utest.log", "a")
		snmpServers=Array::new

		log<<"\nStarting SNMP-Unified\n"


		log<<"Opened SNMP on localhost\n"
		log.flush
		begin	
		$stdin.each_line {|data|

			#data.chomp!	
			log<<"Question: #{data} \n"
			log.flush
			response=nil
			
			begin
			@snmpServers.each {|server|
				server.send(data, 0)
				if not select([server], nil, nil, 3)
					log << "Server didn't answer.\n"
					log.flush
					return
				end
				
				response=server.recv(2000,0)
				
				log<< "Answer: #{response}.  Checking error\n"
				log.flush

				tag,val,msg = tlv(reponse)
				log << "."
				log.flush

				tag,dummy,msg=tlv(val)
				log << "."
				log.flush

				tag,dummy,msg=tlv(msg)
				log << "."
				log.flush

				pdutype,pdu,msg=tlv(msg)
				log << "."
				log.flush

				tag,dummy,msg=tlv(pdu)
				log << "."
				log.flush

				tag,err,msg=tlv(msg)
				log << "."
				log.flush

				log << "Error code: #{dec_int(err)}"
  				log.flush
	
				if not [2, 5].include? dec_int(err)
					raise SNMPSuccessException
				end
				}
			rescue SNMPSuccessException
				print response
			end

		}
		rescue => e
			log<<"\nEXCEPTION: #{e.message} \n"
			raise
		end

		log << "Exiting.  Who knows why?\n"; log.flush

	end
end


main

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