6 files changed, 38 insertions, 10 deletions
diff --git a/node/Constants.hpp b/node/Constants.hpp
index 8803ecee..ac1919b3 100644
--- a/node/Constants.hpp
+++ b/node/Constants.hpp
@@ -321,6 +321,11 @@
 #define ZT_MIN_UNITE_INTERVAL 30000
 
 /**
+ * How often should peers try memorized or statically defined paths?
+ */
+#define ZT_TRY_MEMORIZED_PATH_INTERVAL 30000
+
+/**
  * Sanity limit on maximum bridge routes
  *
  * If the number of bridge routes exceeds this, we cull routes from the
diff --git a/node/Node.cpp b/node/Node.cpp
index a180766b..11f76365 100644
--- a/node/Node.cpp
+++ b/node/Node.cpp
@@ -683,7 +683,7 @@ void Node::postTrace(const char *module,unsigned int line,const char *fmt,...)
 
 uint64_t Node::prng()
 {
-	unsigned int p = (++_prngStreamPtr % (sizeof(_prngStream) / sizeof(uint64_t)));
+	unsigned int p = (++_prngStreamPtr % ZT_NODE_PRNG_BUF_SIZE);
 	if (!p)
 		_prng.encrypt12(_prngStream,_prngStream,sizeof(_prngStream));
 	return _prngStream[p];
diff --git a/node/Node.hpp b/node/Node.hpp
index 7d99ff09..eb46527d 100644
--- a/node/Node.hpp
+++ b/node/Node.hpp
@@ -49,6 +49,9 @@
 #define ZT_EXPECTING_REPLIES_BUCKET_MASK1 255
 #define ZT_EXPECTING_REPLIES_BUCKET_MASK2 31
 
+// Size of PRNG stream buffer
+#define ZT_NODE_PRNG_BUF_SIZE 64
+
 namespace ZeroTier {
 
 /**
@@ -195,7 +198,7 @@ public:
 #endif
 
 	bool shouldUsePathForZeroTierTraffic(const Address &ztaddr,const InetAddress &localAddress,const InetAddress &remoteAddress);
-	inline bool getPathHint(const Address &ztaddr,int family,InetAddress &addr) { return ( (_cb.pathLookupFunction) ? (_cb.pathLookupFunction(reinterpret_cast<ZT_Node *>(this),_uPtr,ztaddr.toInt(),family,reinterpret_cast<struct sockaddr_storage *>(&addr)) != 0) : false ); }
+	inline bool externalPathLookup(const Address &ztaddr,int family,InetAddress &addr) { return ( (_cb.pathLookupFunction) ? (_cb.pathLookupFunction(reinterpret_cast<ZT_Node *>(this),_uPtr,ztaddr.toInt(),family,reinterpret_cast<struct sockaddr_storage *>(&addr)) != 0) : false ); }
 
 	uint64_t prng();
 	void postCircuitTestReport(const ZT_CircuitTestReport *report);
@@ -284,7 +287,7 @@ private:
 
 	unsigned int _prngStreamPtr;
 	Salsa20 _prng;
-	uint64_t _prngStream[16]; // repeatedly encrypted with _prng to yield a high-quality non-crypto PRNG stream
+	uint64_t _prngStream[ZT_NODE_PRNG_BUF_SIZE]; // repeatedly encrypted with _prng to yield a high-quality non-crypto PRNG stream
 
 	uint64_t _now;
 	uint64_t _lastPingCheck;
diff --git a/node/Peer.cpp b/node/Peer.cpp
index e0bd0eac..2ef139e1 100644
--- a/node/Peer.cpp
+++ b/node/Peer.cpp
@@ -43,6 +43,7 @@ static uint32_t _natKeepaliveBuf = 0;
 Peer::Peer(const RuntimeEnvironment *renv,const Identity &myIdentity,const Identity &peerIdentity) :
 	_lastReceive(0),
 	_lastNontrivialReceive(0),
+	_lastTriedMemorizedPath(0),
 	_lastDirectPathPushSent(0),
 	_lastDirectPathPushReceive(0),
 	_lastCredentialRequestSent(0),
@@ -373,6 +374,16 @@ void Peer::attemptToContactAt(const InetAddress &localAddr,const InetAddress &at
 	}
 }
 
+void Peer::tryMemorizedPath(uint64_t now)
+{
+	if ((now - _lastTriedMemorizedPath) >= ZT_TRY_MEMORIZED_PATH_INTERVAL) {
+		_lastTriedMemorizedPath = now;
+		InetAddress mp;
+		if (RR->node->externalPathLookup(_id.address(),-1,mp))
+			attemptToContactAt(InetAddress(),mp,now);
+	}
+}
+
 bool Peer::doPingAndKeepalive(uint64_t now,int inetAddressFamily)
 {
 	Mutex::Lock _l(_paths_m);
diff --git a/node/Peer.hpp b/node/Peer.hpp
index a7240cb4..78b345b9 100644
--- a/node/Peer.hpp
+++ b/node/Peer.hpp
@@ -165,6 +165,13 @@ public:
 	void attemptToContactAt(const InetAddress &localAddr,const InetAddress &atAddress,uint64_t now);
 
 	/**
+	 * Try a memorized or statically defined path if any are known
+	 *
+	 * Under the hood this is done periodically based on ZT_TRY_MEMORIZED_PATH_INTERVAL.
+	 */
+	void tryMemorizedPath(uint64_t now);
+
+	/**
 	 * Send pings or keepalives depending on configured timeouts
 	 *
 	 * @param now Current time
@@ -435,6 +442,7 @@ private:
 	uint8_t _remoteClusterOptimal6[16];
 	uint64_t _lastReceive; // direct or indirect
 	uint64_t _lastNontrivialReceive; // frames, things like netconf, etc.
+	uint64_t _lastTriedMemorizedPath;
 	uint64_t _lastDirectPathPushSent;
 	uint64_t _lastDirectPathPushReceive;
 	uint64_t _lastCredentialRequestSent;
diff --git a/node/Switch.cpp b/node/Switch.cpp
index 881d7b92..7c94d438 100644
--- a/node/Switch.cpp
+++ b/node/Switch.cpp
@@ -710,12 +710,12 @@ bool Switch::_trySend(const Packet &packet,bool encrypt)
 	if (peer) {
 		const uint64_t now = RR->node->now();
 
-		// First get the best path, and if it's dead (and this is not a root)
-		// we attempt to re-activate that path but this packet will flow
-		// upstream. If the path comes back alive, it will be used in the future.
-		// For roots we don't do the alive check since roots are not required
-		// to send heartbeats "down" and because we have to at least try to
-		// go somewhere.
+		/* First get the best path, and if it's dead (and this is not a root)
+		 * we attempt to re-activate that path but this packet will flow
+		 * upstream. If the path comes back alive, it will be used in the future.
+		 * For roots we don't do the alive check since roots are not required
+		 * to send heartbeats "down" and because we have to at least try to
+		 * go somewhere. */
 
 		SharedPtr<Path> viaPath(peer->getBestPath(now,false));
 		if ( (viaPath) && (!viaPath->alive(now)) && (!RR->topology->isRoot(peer->identity())) ) {
@@ -724,7 +724,8 @@ bool Switch::_trySend(const Packet &packet,bool encrypt)
 			viaPath.zero();
 		}
 		if (!viaPath) {
-			SharedPtr<Peer> relay(RR->topology->getUpstreamPeer());
+			peer->tryMemorizedPath(now); // periodically attempt memorized or statically defined paths, if any are known
+			const SharedPtr<Peer> relay(RR->topology->getUpstreamPeer());
 			if ( (!relay) || (!(viaPath = relay->getBestPath(now,false))) ) {
 				if (!(viaPath = peer->getBestPath(now,true)))
 					return false;