Let ConnectionMaker report the reason the connection broke

router/connection.go

@@ -402,7 +402,7 @@ func (conn *LocalConnection) shutdown(err error) {
 	// try to send any more
 	conn.stopForwarders()
 
-	conn.Router.ConnectionMaker.ConnectionTerminated(conn.remoteTCPAddr)
+	conn.Router.ConnectionMaker.ConnectionTerminated(conn.remoteTCPAddr, err)
 }
 
 // Helpers

router/connection_maker.go

@@ -26,6 +26,7 @@ type ConnectionMaker struct {
 // Information about an address where we may find a peer
 type Target struct {
 	attempting  bool          // are we currently attempting to connect there?
+	lastError   error         // reason for disconnection last time
 	tryAfter    time.Time     // next time to try this address
 	tryInterval time.Duration // backoff time on next failure
 }
@@ -64,10 +65,11 @@ func (cm *ConnectionMaker) ForgetConnection(address string) {
 	}
 }
 
-func (cm *ConnectionMaker) ConnectionTerminated(address string) {
+func (cm *ConnectionMaker) ConnectionTerminated(address string, err error) {
 	cm.actionChan <- func() bool {
 		if target, found := cm.targets[address]; found {
 			target.attempting = false
+			target.lastError = err
 			target.tryAfter, target.tryInterval = tryAfter(target.tryInterval)
 		}
 		return true
@@ -89,13 +91,15 @@ func (cm *ConnectionMaker) String() string {
 	cm.actionChan <- func() bool {
 		var buf bytes.Buffer
 		for address, target := range cm.targets {
-			var fmtStr string
+			fmt.Fprint(&buf, address)
+			if target.lastError != nil {
+				fmt.Fprintf(&buf, " (%s)", target.lastError)
+			}
 			if target.attempting {
-				fmtStr = "%s (trying since %v)\n"
+				fmt.Fprintf(&buf, " (trying since %v)\n", target.tryAfter)
 			} else {
-				fmtStr = "%s (next try at %v)\n"
+				fmt.Fprintf(&buf, " (next try at %v)\n", target.tryAfter)
 			}
-			fmt.Fprintf(&buf, fmtStr, address, target.tryAfter)
 		}
 		resultChan <- buf.String()
 		return false
@@ -201,7 +205,7 @@ func (cm *ConnectionMaker) attemptConnection(address string, acceptNewPeer bool)
 	log.Printf("->[%s] attempting connection\n", address)
 	if err := cm.ourself.CreateConnection(address, acceptNewPeer); err != nil {
 		log.Printf("->[%s] error during connection attempt: %v\n", address, err)
-		cm.ConnectionTerminated(address)
+		cm.ConnectionTerminated(address, err)
 	}
 }
 

site/troubleshooting.md

@@ -79,7 +79,7 @@ broadcast:
 7a:f4:56:87:76:3b -> [7a:16:dd:5b:83:de]
 7a:16:dd:5b:83:de -> []
 Reconnects:
-192.168.32.1:6783 (next try at 2014-10-23 16:39:50.585932102 +0000 UTC)
+192.168.32.1:6783 (dial tcp4 192.168.32.1:6783: connection timed out) (next try at 2014-10-23 16:39:50.585932102 +0000 UTC)
 
 weavedns container is not present; have you launched it?
 ````
@@ -121,8 +121,8 @@ for a full explanation.
 
 The 'Reconnects' section lists peers that this router is aware of, but is
 not currently connected to.  Each line contains some information about
-whether it is attempting to connect or is waiting for a while before
-connecting again.
+what went wrong the last time; whether it is attempting to connect or
+is waiting for a while before connecting again.
 
 Finally, status information from weave DNS is included. In this example,
 the DNS container has not been launched so no status information is