ip/netaddress: add reachability score.

lib/primitives/netaddress.js

@@ -168,6 +168,16 @@ NetAddress.prototype.isOnion = function isOnion() {
   return IP.isOnion(this.raw);
 };
 
+/**
+ * Get reachable score to destination.
+ * @param {NetAddress} dest
+ * @returns {Number}
+ */
+
+NetAddress.prototype.getReachability = function getReachability(dest) {
+  return IP.getReachability(this.raw, dest.raw);
+};
+
 /**
  * Set null host.
  */

lib/utils/ip.js

@@ -52,7 +52,8 @@ IP.types = {
   DNS: -1,
   IPV4: 4,
   IPV6: 6,
-  ONION: 10
+  ONION: 10,
+  TEREDO: 11
 };
 
 /**
@@ -493,6 +494,20 @@ IP.getType = function getType(raw) {
   assert(false, 'Unknown type.');
 };
 
+/**
+ * Get addr network. Similar to
+ * type, but includes teredo.
+ * @param {Buffer} raw
+ * @returns {Number}
+ */
+
+IP.getNetwork = function getNetwork(raw) {
+  if (IP.isRFC4380(raw))
+    return IP.types.TEREDO;
+
+  return IP.getType(raw);
+};
+
 /**
  * Test whether the host is null.
  * @returns {Boolean}
@@ -832,6 +847,94 @@ IP.isRoutable = function isRoutable(raw) {
   return true;
 };
 
+/**
+ * Calculate reachable score from source to destination.
+ * @param {Buffer} src
+ * @param {Buffer} dest
+ * @returns {Number} Ranges from 0-6.
+ */
+
+IP.getReachability = function getReachability(src, dest) {
+  var srcNet = IP.getNetwork(src);
+  var destNet = IP.getNetwork(dest);
+  var types = IP.types;
+  var UNREACHABLE = 0;
+  var DEFAULT = 1;
+  var TEREDO = 2;
+  var IPV6_WEAK = 3;
+  var IPV4 = 4;
+  var IPV6_STRONG = 5;
+  var PRIVATE = 6;
+
+  if (!IP.isRoutable(src))
+    return UNREACHABLE;
+
+  switch (destNet) {
+    case types.IPV4:
+      switch (srcNet) {
+        case types.IPV4:
+          return IPV4;
+        default:
+          return DEFAULT;
+      }
+      break;
+    case types.IPV6:
+      switch (srcNet) {
+        case types.TEREDO:
+          return TEREDO;
+        case types.IPV4:
+          return IPV4;
+        case types.IPV6:
+          if (IP.isRFC3964(src)
+              || IP.isRFC6052(src)
+              || IP.isRFC6145(src)) {
+            // tunnel
+            return IPV6_WEAK;
+          }
+          return IPV6_STRONG;
+        default:
+          return DEFAULT;
+      }
+      break;
+    case types.ONION:
+      switch (srcNet) {
+        case types.IPV4:
+          return IPV4;
+        case types.ONION:
+          return PRIVATE;
+        default:
+          return DEFAULT;
+      }
+      break;
+    case types.TEREDO:
+      switch (srcNet) {
+        case types.TEREDO:
+          return TEREDO;
+        case types.IPV6:
+          return IPV6_WEAK;
+        case types.IPV4:
+          return IPV4;
+        default:
+          return DEFAULT;
+      }
+      break;
+    default:
+      switch (srcNet) {
+        case types.TEREDO:
+          return TEREDO;
+        case types.IPV6:
+          return IPV6_WEAK;
+        case types.IPV4:
+          return IPV4;
+        case types.ONION:
+          return PRIVATE;
+        default:
+          return DEFAULT;
+      }
+      break;
+  }
+};
+
 /**
  * Test whether an IP has a prefix.
  * @param {Buffer} raw