Add an (as of yet untested) OC implementation of a Hierarchial Gateway

cdlib.lua

@@ -35,7 +35,9 @@ return {
 	end,
 	decode = function (d)
 		if d:len() < 3 then return end
-		return d:byte(1), decodeNoHops(d:sub(2))
+		local src, dst, data = decodeNoHops(d:sub(2))
+		if not data then return end
+		return d:byte(1), src, dst, data
 	end,
 	decodeNoHops = decodeNoHops
 }

oc/hierarchi.lua

@@ -0,0 +1,108 @@
+-- I, 20kdc, release this into the public domain.
+-- No warranty is provided, implied or otherwise.
+
+-- Copper Hierarchial Gateway implementation for OpenComputers.
+-- Should be run in a Server Rack, with two servers, connected by Linked Cards.
+-- Each should be responsible for "it's" side.
+-- This is a piece of dedicated hardware for a specific purpose.
+-- The only reason it's not run on two microcontrollers is because 
+--  they're inconvenient to use and cdlib needs to be there -
+-- I'm sure you can port it yourself.
+
+local args = {...}
+
+-- Does the single modem connected to this server connect to the outside world?
+local outbound = false
+
+if #args ~= 2 then error("Expecting args: outbound ('true'/'false'), network-name") end
+
+if args[1] == "true" then
+	outbound = true
+elseif args[1] ~= "false" then
+	error("Only 'true' or 'false' are allowed for the 'outbound' argument.")
+end
+
+-- What is the name of this division, including forward-slash?
+local netname = args[2] .. "/"
+
+local event = require("event")
+local component = require("component")
+local cdlib = require("cdlib")
+
+local modem = component.modem
+local tunnel = component.tunnel
+
+-- It is possible that this is meant to be used
+--  on public wireless infrastructure -
+-- for example, if this was a server-level domain,
+--  perhaps solely connected via wireless...
+-- Oh well. It's the sysadmin's decision to connect it this way.
+-- Any wireless-abuse is the local regulator's decision.
+if modem.isWireless() then
+	modem.setStrength(400)
+end
+modem.open(4957)
+
+-- Rules used on messages coming in from the 'modem' side.
+-- (This implies Tunnel packets are trusted absolutely - which is correct.)
+local processFrom, processTo
+
+-- Implementation of the rules described in protocol.1 for more or 
+--  less unambiguous name translation.
+if outbound then
+	processFrom = function (from)
+		if from:sub(1, netname:len()) == netname then
+			return
+		end
+		return "<" .. from
+	end
+	processTo = function (nto)
+		if from:sub(1, netname:len()) ~= netname then
+			return
+		end
+		return from:sub(netname:len() + 1)
+	end
+else
+	processFrom = function (from)
+		if from:sub(1, 1) == "<" then
+			return
+		end
+		return netname .. from
+	end
+	processTo = function (nto)
+		if from:sub(1, 1) ~= "<" then
+			return
+		end
+		return from:sub(2)
+	end
+end
+
+local function checkLen(s)
+	if s:len() == 0 then return end
+	if s:len() > 256 then return end
+	return s
+end
+
+while true do
+	local e = {event.pull("modem_message")}
+	if e[1] == "modem_message" then
+		-- type, to, from, port, dist, data
+		if ((e[2] == tunnel.address) or (e[4] == 4957)) then
+			local hops, nfrom, nto, data = cdlib.decode(e[6])
+			if data then
+				if e[2] == tunnel.address then
+					-- Pass it on as given.
+					modem.broadcast(4957, e[6])
+				elseif e[2] == modem.address then
+					-- Process it, then give to tunnel
+					if hops ~= 255 then
+						local tfrom, tto = checkLen(processFrom(nfrom)), checkLen(processTo(nto))
+						if tfrom and tto then
+							tunnel.send(cdlib.encode(hops + 1, tfrom, tto, data))
+						end
+					end
+				end
+			end
+		end
+	end
+end