p2p: use /16 filtering on IPv4-within-IPv6 addresses

IPv6 addresses include a range that can map IPv4 addresses,
which allowed those mapped addresses to bypass filtering.

This filter should be replaced by AS filtering at some point.

src/p2p/net_node.inl

@@ -1436,6 +1436,20 @@ namespace nodetool
             const uint32_t actual_ip = na.as<const epee::net_utils::ipv4_network_address>().ip();
             classB.insert(actual_ip & 0x0000ffff);
           }
+#if BOOST_VERSION > 106600
+          else if (cntxt.m_remote_address.get_type_id() == epee::net_utils::ipv6_network_address::get_type_id())
+          {
+            const epee::net_utils::network_address na = cntxt.m_remote_address;
+            const boost::asio::ip::address_v6 &actual_ip = na.as<const epee::net_utils::ipv6_network_address>().ip();
+            if (actual_ip.is_v4_mapped())
+            {
+              boost::asio::ip::address_v4 v4ip = make_address_v4(boost::asio::ip::v4_mapped, actual_ip);
+              uint32_t actual_ipv4;
+              memcpy(&actual_ipv4, v4ip.to_bytes().data(), sizeof(actual_ipv4));
+              classB.insert(actual_ipv4 & ntohl(0xffff0000));
+            }
+          }
+#endif
           return true;
         });
       }
@@ -1471,6 +1485,20 @@ namespace nodetool
             uint32_t actual_ip = na.as<const epee::net_utils::ipv4_network_address>().ip();
             skip = classB.find(actual_ip & 0x0000ffff) != classB.end();
           }
+#if BOOST_VERSION > 106600
+          else if (skip_duplicate_class_B && pe.adr.get_type_id() == epee::net_utils::ipv6_network_address::get_type_id())
+          {
+            const epee::net_utils::network_address na = pe.adr;
+            const boost::asio::ip::address_v6 &actual_ip = na.as<const epee::net_utils::ipv6_network_address>().ip();
+            if (actual_ip.is_v4_mapped())
+            {
+              boost::asio::ip::address_v4 v4ip = make_address_v4(boost::asio::ip::v4_mapped, actual_ip);
+              uint32_t actual_ipv4;
+              memcpy(&actual_ipv4, v4ip.to_bytes().data(), sizeof(actual_ipv4));
+              skip = classB.find(actual_ipv4 & ntohl(0xffff0000)) != classB.end();
+            }
+          }
+#endif
 
           // consider each host once, to avoid giving undue inflence to hosts running several nodes
           if (!skip)
@@ -1493,11 +1521,11 @@ namespace nodetool
         if (skipped == 0 || !filtered.empty())
           break;
         if (skipped)
-          MINFO("Skipping " << skipped << " possible peers as they share a class B with existing peers");
+          MDEBUG("Skipping " << skipped << " possible peers as they share a class B with existing peers");
       }
       if (filtered.empty())
       {
-        MDEBUG("No available peer in " << (use_white_list ? "white" : "gray") << " list filtered by " << next_needed_pruning_stripe);
+        MINFO("No available peer in " << (use_white_list ? "white" : "gray") << " list filtered by " << next_needed_pruning_stripe);
         return false;
       }
       if (use_white_list)