Hi, Tom & Paul:

1)    " ...   hand waved ...  ":    Through my line of work, I was trained to behave exactly the opposite. I am surprised at you jumping to the conclusion, even before challenging me about where did I get my viewpoint from. The fact is, it has been clearly documented in our IETF draft for the last couple years (since Rev-06 on 2019 Dec. 1)! For your convenience, please see below a copy of the potential target code fragment and critique. It appears to me that our software member suggested to comment out only one line (1047).


Regards,



Abe (2022-03-26 18:16) 


****************
D.1. Candidate Code for Modification

   The following short JavaScript function named "ifip" in the TP-Link
   Archer C20 V4 source code has been shown to selectively reject
   specific ranges of IP addresses. In particular, Line 1047 uses a "2's
   Complement" technique to identify the 240/4 netblock as "PRESERVED",
   thus rejecting it. A quick scan of the firmware code in the router
   indicates that this function is a popular utility because there are
   numerous processes calling for it. So, this should be the best
   candidate to start testing our concept.

   lib.js:1040:ifip: function(ip, unalert) {
   lib.js-1041-if ((ip = $.ip2num(ip)) === false) return $.alert(ERR_IP_FORMAT, unalert);
   lib.js-1042-if (ip == -1) return $.alert(ERR_IP_BROADCAST, unalert);
   lib.js-1043-var net = ip >> 24;
   lib.js-1044-if (net == 0) return $.alert(ERR_IP_SUBNETA_NET_0, unalert);
   lib.js-1045-if (net == 127) return $.alert(ERR_IP_LOOPBACK, unalert);
   lib.js-1046-if (net >= -32 && net < -16) return $.alert(ERR_IP_MULTICAST, unalert);
   lib.js-1047-if (net >= -16 && net < 0) return $.alert(ERR_IP_PRESERVED, unalert);
   lib.js-1048-return 0;
   lib.js-1049-},

D.2. Proposed Modification

   To stop rejecting the 240/4 netblock addressed packets, below is a
   modification that comments out Line 1047, a modification that has
   been shown to eliminate javascript pre-validation of 240/4 IP
   addresses, allowing them to be sent within the router, where a second
   layer of validation rejects them in a different way.

   lib.js:1040:   ifip: function(ip, unalert) {
   lib.js-1041- if ((ip = $.ip2num(ip)) === false) return $.alert(ERR_IP_FORMAT, unalert);
   lib.js-1042- if (ip == -1) return $.alert(ERR_IP_BROADCAST, unalert);
   lib.js-1043-   var net = ip >> 24;
   lib.js-1044- if (net == 0) return $.alert(ERR_IP_SUBNETA_NET_0, unalert);
   lib.js-1045- if (net == 127) return $.alert(ERR_IP_LOOPBACK, unalert);
   lib.js-1046- if (net >= -32 && net < -16) return $.alert(ERR_IP_MULTICAST, unalert);
   lib.js-1047- //if (net >= -16 && net < 0) return $.alert(ERR_IP_PRESERVED, unalert);
   lib.js-1048- return 0;
   lib.js-1049-},

****************

On 2022-03-26 12:37, Tom Beecher wrote:
Have you ever considered that this may be in fact:

*/writing/* and */deploying/* the code that will allow the use of 240/4 the
way you expect

While Mr. Chen may have considered that, he has repeatedly hand waved that it's 'not that big a deal.', so I don't think he adequately grasps the scale of that challenge. 

On Sat, Mar 26, 2022 at 9:53 AM Paul Rolland <rol@witbe.net> wrote:
Hello,

On Sat, 26 Mar 2022 09:35:30 -0400
"Abraham Y. Chen" <aychen@avinta.com> wrote:

> touching the hardware, by implementing the EzIP technique (*/disabling/*
> the program code that has been */disabling/* the use of the 240/4
> netblock), an existing CG-NAT module becomes a RAN! As to universal

Have you ever considered that this may be in fact:

*/writing/* and */deploying/* the code that will allow the use of 240/4 the
way you expect


Paul



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