WRT120N Latest firmware BUG & PATCH

Question

Hello,
I just bought a WRT120N Wireless Access Point. I upgraded its firmware to the latest available (v1.0.04) but there is a BUG in the "Applications & Gaming" section. In particular, in the "Single Port Forwarding": two applications with the same internal port, even with different IP addresses, can be added and the error message is "Port Number is duplicate.".
This behavior is incorrect and can be explained with an example: let us assume we have two web server behind the NAT. Both are listening on the default port 80/tcp and have address 192.168.1.2 and 192.168.1.3. It is possible to forward the data received by the router on port 80/tcp to the web server 192.168.1.2 and the data received by the router on port 8080/tcp to the web server 192.168.1.3. This is allowed because everything is unique: if the router receive a packet on port 80/tcp it have to rewrite the destination IP address and insert 192.168.1.2 while if it receive a packet on port 8080/tcp it have to rewrite the destination IP address and tcp port (192.168.1.3 and 80). It is irrelevant that final port destination is the same. Of course, it is important that the two rules have a different external port: otherwise the router could not distinguish between them but the internal port is irrelevant (as long as two rules are not identical).
The BUG is circumscribed in the JavaScript since I tried to "nop" the wrong check with Firefox/Firebug and the rules are correctly memorized in the configuration and they works without issues.
I Fixed the JavaScript and, in the following, there is the patch. Actually, this patch does not solve another minor BUG: theoretically it is possible to redirect two different external ports to the same couple internal IP/port. The solution is trivial too, but this would require rewrite a larger portion of code, so I decided to not fix this minor BUG because it is less severe and the scenario is less common.
This BUG seems tightly related to http://forums.linksysbycisco.com/linksys/board/message?board.id=Wireless_Routers&message.id=85768&query.id=245618#M85768 but that one is on another router/firmware (that I do not own) so I do not know if this patch apply to that BUG too.
Please let me know if you need further informations
Marco Papa Manzillo
----------- Patch -------------
 diff -ur 192.168.167.1 2/index.htm 192.168.167.1/index.htm
--- 192.168.167.1 2/index.htm   2010-01-05 13:39:59.000000000 +0100
+++ 192.168.167.1/index.htm     2010-01-05 14:32:00.000000000 +0100
@@ -535,9 +535,10 @@
 var fNameHead = "gport_external";
 var fNameTail = "gport_internal";
+var fNameIP   = "private_ip4_";
 var applicationName = "application";
 var appname = "";
-var i, rs, rs2, j, index, numProtocol, temp;
+var i, rs, rs2, j, index, numProtocol, ipv4_private, temp, temp2;
  for (i = 0; i < F.elements.length; i++) {
 f = F.elements[i];
@@ -548,11 +549,15 @@
 continue;
        }else {
 temp = "protocol" + f.name.substring (fNameTail.length, fNameTail.length + 2);
+temp2 = fNameIP + f.name.substring (fNameTail.length, fNameTail.length + 2);
 }else {
 temp = "protocol" + f.name.substring (fNameHead.length, fNameHead.length + 2);
+temp2 = fNameIP + f.name.substring (fNameHead.length, fNameHead.length + 2);
 numProtocol = document.getElementsByName(temp)[0].value;
+ipv4_private = document.getElementsByName(temp2)[0].value;
+
 if (f.value.length == 0)continue;
@@ -584,7 +589,7 @@
 if(rs2=="1") break;}
-rs = checkDuplication_PortRange3 (F, f, numProtocol, fNameHead, fNameTail, 0, 15);
+rs = checkDuplication_PortRange3 (F, f, numProtocol, ipv4_private, fNameHead, fNameTail, fNameIP, 0, 15);
 if (rs == true||rs2 == "1") {
 alert (msg_alert_0038);
 //f.value = f.defaultValue;
diff -ur 192.168.167.1 2/jslib.js 192.168.167.1/jslib.js
--- 192.168.167.1 2/jslib.js    2010-01-05 13:35:03.000000000 +0100
+++ 192.168.167.1/jslib.js      2010-01-05 15:27:11.000000000 +0100
@@ -549,19 +549,21 @@
        return false;
 //rob. 2009.0325 also check protocol type when submit form.
-function checkDuplication_PortRange3 (F, f, numProtocol, fNameHead, fNameTail, startCount, maxItem)
+// Marco Papa Manzillo 2009.0105 also check internal IPv4 for internal port when submit form
+function checkDuplication_PortRange3 (F, f, numProtocol, ipv4_private,fNameHead, fNameTail, fNameIP, startCount, maxItem)
        if (fNameHead.length == 0)      return false;
        if (fNameTail.length == 0)      return false;
        if (f.value.length   == 0)      return false;
        var fPort1 = new Array (null, null, null, null);
-       var tmpName1, tmpName2;
+       var tmpName1, tmpName2, tmpName3;
        var fProtocol = "protocol";
        var tmpProtocol;
-       var a, a2, b1, b2, ck=0,rs;
+       var a, a2, a3, b1, b2, b4, ck=0,rs;
        a= parseInt (f.value);
        a2=parseInt (numProtocol);
+       a3=parseInt (ipv4_private);
        tmpName1 = "";
        if (f.name.substring (0, fNameHead.length) == fNameHead)
@@ -575,19 +577,21 @@
                tmpName1 = fNameHead + i;
                tmpName2 = fNameTail + i;
                tmpProtocol = fProtocol + i;
+               tmpName3 = fNameIP + i;
                if (f.name == tmpName1 || f.name == tmpName2)   continue;
-               rs = DynamicGetField (F, 3, tmpName1, tmpName2, tmpProtocol, "", fPort1);
+               rs = DynamicGetField (F, 4, tmpName1, tmpName2, tmpProtocol, tmpName3, fPort1);
                if (rs == false)        continue;
                b1 = (fPort1[0].value.length == 0) ? 0: parseInt (fPort1[0].value);
                b2 = (fPort1[1].value.length == 0) ? 0: parseInt (fPort1[1].value);
                b3 = (fPort1[2].value.length == 0) ? 0: parseInt (fPort1[2].value);
+               b4 = (fPort1[3].value.length == 0) ? 0: parseInt (fPort1[3].value);
                if (ck==0)//check tail
-                       if (a == b2)
+                       if (a == b2 && a3==b4 ) // Internal IP must be checked only for internal ports.
                                if ((a2 == 99)||(a2 == b3)) return true;

Answer 1

First of all I would suggest you to reset the router for 45 seconds and reconfigure all the settings again as you have upgraded the router's firmware.
What is the IP address you are getting from the modem...?
What happen when you connect the computer directly to the Modem..?
Do not load the backup config file on the router.After resetting the router,reconfigure all the settings again.