[netfpga] phase in ipv4 side of the code

p4src/minip4_solution.p4

@@ -131,8 +131,33 @@ control RealMain(
                 v4_networks.apply();       /* apply egress for IPv4 */
                 exit;                      /* no further v6 processing */
 
+            } else if(hdr.ipv4.isValid()) {
+                if(icmp.apply().hit) {
+                    v4_networks.apply();
+                    exit;
+                } else if(nat46.apply().hit) {
+                    if(hdr.icmp.isValid()) {
+                        nat46_icmp_generic();
+
+                        if(hdr.icmp.type == ICMP_ECHO_REPLY) {
+                            hdr.icmp6.type = ICMP6_ECHO_REPLY;
+                        }
+                        if(hdr.icmp.type == ICMP_ECHO_REQUEST) {
+                            hdr.icmp6.type = ICMP6_ECHO_REQUEST;
+                        }
+                    }
+                    if(hdr.udp.isValid()) {
+                        delta_udp_from_v4_to_v6
+                    }
+                    if(hdr.tcp.isValid()) {
+                        delta_tcp_from_v4_to_v6
+                    }
+
+                    v6_networks.apply();
+                    exit;
+                }
+                v4_networks.apply();             /* regular routing, egress */
             }
-        }
 
         lookup_table.apply();
     }