Fix computer IDs greater than 65535 crashing Rednet (#900)

illuaminate.sexp

@@ -61,6 +61,8 @@
       (table space)
       (index no-space))
 
+    (allow-clarifying-parens true)
+
     ;; colours imports from colors, and we don't handle that right now.
     ;; keys is entirely dynamic, so we skip it.
     (dynamic-modules colours keys _G)

src/main/resources/data/computercraft/lua/rom/apis/rednet.lua

@@ -25,10 +25,18 @@ CHANNEL_BROADCAST = 65535
 --- The channel used by the Rednet API to repeat messages.
 CHANNEL_REPEAT = 65533
 
+--- The number of channels rednet reserves for computer IDs. Computers with IDs
+-- greater or equal to this limit wrap around to 0.
+MAX_ID_CHANNELS = 65500
+
 local tReceivedMessages = {}
 local tReceivedMessageTimeouts = {}
 local tHostnames = {}
 
+local function id_as_channel(id)
+    return (id or os.getComputerID()) % MAX_ID_CHANNELS
+end
+
 --[[- Opens a modem with the given @{peripheral} name, allowing it to send and
 receive messages over rednet.
 
@@ -47,7 +55,7 @@ function open(modem)
     if peripheral.getType(modem) ~= "modem" then
         error("No such modem: " .. modem, 2)
     end
-    peripheral.call(modem, "open", os.getComputerID())
+    peripheral.call(modem, "open", id_as_channel())
     peripheral.call(modem, "open", CHANNEL_BROADCAST)
 end
 
@@ -64,7 +72,7 @@ function close(modem)
         if peripheral.getType(modem) ~= "modem" then
             error("No such modem: " .. modem, 2)
         end
-        peripheral.call(modem, "close", os.getComputerID())
+        peripheral.call(modem, "close", id_as_channel())
         peripheral.call(modem, "close", CHANNEL_BROADCAST)
     else
         -- Close all modems
@@ -87,7 +95,7 @@ function isOpen(modem)
     if modem then
         -- Check if a specific modem is open
         if peripheral.getType(modem) == "modem" then
-            return peripheral.call(modem, "isOpen", os.getComputerID()) and peripheral.call(modem, "isOpen", CHANNEL_BROADCAST)
+            return peripheral.call(modem, "isOpen", id_as_channel()) and peripheral.call(modem, "isOpen", CHANNEL_BROADCAST)
         end
     else
         -- Check if any modem is open
@@ -134,10 +142,11 @@ function send(nRecipient, message, sProtocol)
     tReceivedMessageTimeouts[os.startTimer(30)] = nMessageID
 
     -- Create the message
-    local nReplyChannel = os.getComputerID()
+    local nReplyChannel = id_as_channel()
     local tMessage = {
         nMessageID = nMessageID,
         nRecipient = nRecipient,
+        nSender = os.getComputerID(),
         message = message,
         sProtocol = sProtocol,
     }
@@ -145,10 +154,14 @@ function send(nRecipient, message, sProtocol)
     local sent = false
     if nRecipient == os.getComputerID() then
         -- Loopback to ourselves
-        os.queueEvent("rednet_message", nReplyChannel, message, sProtocol)
+        os.queueEvent("rednet_message", os.getComputerID(), message, sProtocol)
         sent = true
     else
         -- Send on all open modems, to the target and to repeaters
+        if nRecipient ~= CHANNEL_BROADCAST then
+            nRecipient = id_as_channel(nRecipient)
+        end
+
         for _, sModem in ipairs(peripheral.getNames()) do
             if isOpen(sModem) then
                 peripheral.call(sModem, "transmit", nRecipient, nReplyChannel, tMessage)
@@ -390,13 +403,14 @@ function run()
         if sEvent == "modem_message" then
             -- Got a modem message, process it and add it to the rednet event queue
             local sModem, nChannel, nReplyChannel, tMessage = p1, p2, p3, p4
-            if isOpen(sModem) and (nChannel == os.getComputerID() or nChannel == CHANNEL_BROADCAST) then
+            if isOpen(sModem) and (nChannel == id_as_channel() or nChannel == CHANNEL_BROADCAST) then
                 if type(tMessage) == "table" and type(tMessage.nMessageID) == "number"
                     and tMessage.nMessageID == tMessage.nMessageID and not tReceivedMessages[tMessage.nMessageID]
+                    and ((tMessage.nRecipient and tMessage.nRecipient == os.getComputerID()) or nChannel == CHANNEL_BROADCAST)
                 then
                     tReceivedMessages[tMessage.nMessageID] = true
                     tReceivedMessageTimeouts[os.startTimer(30)] = tMessage.nMessageID
-                    os.queueEvent("rednet_message", nReplyChannel, tMessage.message, tMessage.sProtocol)
+                    os.queueEvent("rednet_message", tMessage.nSender or nReplyChannel, tMessage.message, tMessage.sProtocol)
                 end
             end
 

src/main/resources/data/computercraft/lua/rom/programs/rednet/repeat.lua

@@ -14,6 +14,10 @@ else
     print(#tModems .. " modems found.")
 end
 
+local function idAsChannel(id)
+    return (id or os.getComputerID()) % rednet.MAX_ID_CHANNELS
+end
+
 local function open(nChannel)
     for n = 1, #tModems do
         local sModem = tModems[n]
@@ -53,7 +57,7 @@ local ok, error = pcall(function()
                         for n = 1, #tModems do
                             local sOtherModem = tModems[n]
                             peripheral.call(sOtherModem, "transmit", rednet.CHANNEL_REPEAT, nReplyChannel, tMessage)
-                            peripheral.call(sOtherModem, "transmit", tMessage.nRecipient, nReplyChannel, tMessage)
+                            peripheral.call(sOtherModem, "transmit", idAsChannel(tMessage.nRecipient), nReplyChannel, tMessage)
                         end
 
                         -- Log the event

src/test/resources/test-rom/spec/apis/rednet_spec.lua

@@ -84,7 +84,7 @@ describe("The rednet library", function()
         end)
     end)
 
-    describe("on a fake computers", function()
+    describe("on fake computers", function()
         local fake_computer = require "support.fake_computer"
 
         local function computer_with_rednet(id, fn, options)
@@ -168,5 +168,24 @@ describe("The rednet library", function()
 
             fake_computer.run_all({ computer_1, computer_2, computer_3 }, { computer_1, computer_3 })
         end)
+
+        it("repeats messages between computers with massive ids", function()
+            local id_1, id_3 = 24283947, 93428798
+            local computer_1, modem_1 = computer_with_rednet(id_1, function(rednet, _ENV)
+                rednet.send(id_3, "Hello")
+                local id, message = rednet.receive()
+                expect { id, message }:same { id_3, "World" }
+            end, { open = true })
+            local computer_2, modem_2 = computer_with_rednet(2, nil, { open = true, rep = true })
+            local computer_3, modem_3 = computer_with_rednet(id_3, function(rednet)
+                rednet.send(id_1, "World")
+                local id, message = rednet.receive()
+                expect { id, message }:same { id_1, "Hello" }
+            end, { open = true })
+            fake_computer.add_modem_edge(modem_1, modem_2)
+            fake_computer.add_modem_edge(modem_2, modem_3)
+
+            fake_computer.run_all({ computer_1, computer_2, computer_3 }, { computer_1, computer_3 })
+        end)
     end)
 end)

src/test/resources/test-rom/spec/support/fake_computer.lua

@@ -70,15 +70,22 @@ local function make_computer(id, fn)
     return { env = env, peripherals = peripherals, queue_event = queue_event, step = step, co = co }
 end
 
+local function parse_channel(c)
+    if c < 0 or c > 65535 then error("Expected number in range 0-65535", 3) end
+    return c
+end
+
 --- Add a modem to a computer on a particular side
 local function add_modem(owner, side)
     local open, adjacent = {}, {}
     local peripheral = setmetatable({
-        open = function(channel) open[channel] = true end,
+        open = function(channel) open[parse_channel(channel)] = true end,
-        close = function(channel) open[channel] = false end,
+        close = function(channel) open[parse_channel(channel)] = false end,
         closeAll = function(channel) open = {} end,
-        isOpen = function(channel) return open[channel] == true end,
+        isOpen = function(channel) return open[parse_channel(channel)] == true end,
         transmit = function(channel, reply_channel, payload)
+            channel, reply_channel = parse_channel(channel), parse_channel(reply_channel)
+
             for _, adjacent in pairs(adjacent) do
                 if adjacent.open[channel] then
                     adjacent.owner.queue_event("modem_message", adjacent.side, channel, reply_channel, payload, 123)