The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Thursday, July 22, 2010

An update to a quick note on embedding languages within languages

In making this comment I came across this old post of mine from 2007 where I lament the amount of code required to query SNMP values in C. I took one look at the code I wanted:

OID sys = SNMPv2-MIB::sysObjectID.0;
  
if (sys == SNMPv2-SMI::enterprises.5567.1.1)  /* riverstone */
{
  IpAddress destination[] = IP-MIB::ip.24.4.1.1;
  IpAddress mask[]        = IP-MIB::ip.24.4.1.2;
  IpAddress nexthop[]     = IP-MIB::ip.24.4.1.4;
  int       protocol[]    = IP-MIB::ip.24.4.1.7;
  int       age[]         = IP-MIB::ip.24.4.1.8;
  int       metric[]      = IP-MIB::ip.24.4.1.11;
  int       type[]        = IP-MIB::ip.24.4.1.6;
}
else if (sys == SNMPv2-SMI::enterprises.9.1)  /* cisco */
{
  IpAddress destination[] = RFC1213-MIB::ipRouteDest;
  IpAddress mask[]        = RFC1213-MIB::ipRouteMask;
  IpAddress nexthop[]     = RFC1213-MIB::ipRouteNextHop;
  int       protocol[]    = RFC1213-MIB::ipRouteProto;
  int       age[]         = RFC1213-MIB::ipRouteAge;
  int       metric[]      = RFC1213-MIB::ipRouteMetric1;
  int       type[]        = RFC1213-MIB::ipRouteType;
}

for (i = 0 ; i < destination.length; i++)
{
    print(
        destination[i],
        mask[i],
        nexthop[i],
        snmp.protocol(protocol[i]),
        metric[i],
        age[i]
    );
}

and remembered—I did that!

Yup. Back in September of 2009 when I first started playing around with Lua. I installed the SNMP bindings for Lua and wrote the following:

#!/usr/local/bin/lua

-- http://luasnmp.luaforge.net/snmp.html

snmp = require "snmp"
OID  = snmp.mib.oid

routeprotos = 
{
  "other    ",  "local    ",  "netmgmt  ",  "redirect ",
  "egp      ",  "ggp      ",  "hello    ",  "rip      ",
  "is-is    ",  "es-is    ",  "igrp     ",  "bbnspf   ",
  "ospf     ",  "bgp      "
}

print("  Dest           Mask           NextHop         Proto   Metric Age")
print("-------------------------------------------------------------------------------")

router = assert(snmp.open{
                peer      = arg[1] or "XXXXXXXXXXXXXXXXXXXXXXXXX" , 
                community = arg[2] or "XXXXXXXXX"
                })

cisco      = OID "SNMPv2-SMI::enterprises.9.1"
riverstone = OID "SNMPv2-SMI::enterprises.5567.1.1"
sysid      = router["SNMPv2-MIB::sysObjectID.0"]

if string.find(sysid,cisco,1,true) then
  shouldbe = OID "RFC1213-MIB::ipRouteDest"
  result   = 
  {
    { oid = "RFC1213-MIB::ipRouteDest" } ,
    { oid = "RFC1213-MIB::ipRouteMask" } ,
    { oid = "RFC1213-MIB::ipRouteNextHop" } ,
    { oid = "RFC1213-MIB::ipRouteProto" } ,
    { oid = "RFC1213-MIB::ipRouteMetric1" } ,
    { oid = "RFC1213-MIB::ipRouteAge" } ,
  }
elseif string.find(sysid,riverstone,1,true) then
  shouldbe = OID "IP-MIB::ip.24.4.1.1"
  result = 
  {
    { oid = "IP-MIB::ip.24.4.1.1"  } ,
    { oid = "IP-MIB::ip.24.4.1.2"  } ,
    { oid = "IP-MIB::ip.24.4.1.4"  } ,
    { oid = "IP-MIB::ip.24.4.1.7"  } ,
    { oid = "IP-MIB::ip.24.4.1.11" } ,
    { oid = "IP-MIB::ip.24.4.1.8" } ,
  }
end

repeat
  result,err = snmp.getnext(router,result);

  if result ~= nil then
    if string.find(result[1].oid,shouldbe,1,true) == nil then break end

    print(string.format("%-16s",result[1].value)
        .. string.format("%-16s",result[2].value)
        .. string.format("%-16s",result[3].value)
        .. routeprotos[result[4].value]
        .. string.format("%-6d",result[5].value)
        .. string.format("%-6d",result[6].value)
    )    
  end
until false
os.exit(0)

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