Document double/triple matching

doc/plan.org

@@ -123,12 +123,16 @@
 |            | Parsing on wrong field detected by unset fields in wireshark               |       |
 |            | Correcting parser->leads to incorrect checksum                             |       |
 |            | - NDP is answered to, but icmp6 echo request isn't -> extend table         |       |
+|            |                                                                            |       |
 |            | Problem with multiple LPM keys in table                                    |       |
 |            | - logical problem, overlapping length matches                              |       |
 |            | - priority / ordering would be helpful                                     |       |
 |            |                                                                            |       |
 |            |                                                                            |       |
 | 2019-03-25 |                                                                            |       |
+|            | Writing down double LPM problem                                            |       |
+|            | Removing source network support, documenting limitation                    |       |
+|            | Rewriting code to use multiple NAT64 destinations                          |       |
 |            |                                                                            |       |
 |            |                                                                            |       |
 |            |                                                                            |       |
@@ -1281,7 +1285,7 @@ Code:
     }
 #+END_SRC
 
-**** (current) Limitations
+**** (current) Implementation limitations
 ***** No fragmentation support (yet)
 ***** No session handling (yet)
 1:1 mappings. No (automatic) session.
@@ -1292,6 +1296,10 @@ has already been solved in a different domain - could even do
 transparent / in network modification
 ***** Incomplete NDP
       Very limited option support
+***** NAT64 mappings not source network dependent
+Only the destination network is matched for deciding on NAT64, as
+priority based double LPM is not supported. This limits a prefix to be
+used only in one network.
 *** References / Follow up
 **** RFC 2460 IPv6 (Checksum https://tools.ietf.org/html/rfc2460#section-8.1)
 **** RFC 3810 MLD2 https://tools.ietf.org/html/rfc3810

p4app/controller.py

@@ -55,7 +55,12 @@ class L2Controller(object):
 
         self.info['v6_mask'] = 64
         self.info['v6_base'] = ipaddress.ip_network("2001:db8::/32")
-        self.info['v6_gen'] = self.info['v6_base'].subnets(new_prefix=self.info['v6_mask'])
+        self.info['v6_base_hostnet'] = ipaddress.ip_network("2001:db8::/48")
+
+        # possible new range for NAT64 prefixes
+        self.info['v6_base_nat64']   = ipaddress.ip_network("2001:db8:1::/48")
+
+        self.info['v6_gen'] = self.info['v6_base_hostnet'].subnets(new_prefix=self.info['v6_mask'])
 
         self.info['v4_mask'] = 24
         self.info['v4_base'] = ipaddress.ip_network("10.0.0.0/8")

p4debug/double-lpm.md

@@ -13,7 +13,6 @@ In other words:
   should be mapped to 10.1.1.0/24
 
 ## What I tried to do
-
 ### 2 LPM keys
 
 I tried to use one table with two LPM keys, which I would like to
@@ -46,6 +45,8 @@ This results into the compiler problem
           ^^^^^
 ```
 
+## How it could be solved
+
 ### 2 tables (recommendation of Nate)
 
 It does not work, when matching the source address first:
@@ -113,4 +114,11 @@ testing / development, it does not work for a production setup.
 
 ### Ternary matching (recommendation of Andy)
 
-    - Have to investigate
+Could be a solution, because it offers priorities. Is not exactly what
+I want to achieve, because I want to do LPM matching, but it could be
+misused for it.
+
+### Double table with using ID of first match (Andy + Nate ideas)
+
+Use the handle of the source network to match again on exact in the
+2nd table. This might be a very reasonable approach.