don't reconnect to ourself

When we discover that a connection target address leads to ourself we
set the retry time to the zero time.Time value - the only special
time.Time value. We use that marker to a) suppress subsequent
connection attempts, and b) display the next retry as 'never' in
`weave status|report`.

Closes #1305.

router/connection.go

@@ -2,6 +2,7 @@ package router
 
 import (
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"net"
 	"strconv"
@@ -28,6 +29,8 @@ const (
 	TieBreakTied
 )
 
+var ErrConnectToSelf = errors.New("Cannot connect to ourself")
+
 type RemoteConnection struct {
 	local         *Peer
 	remote        *Peer
@@ -437,7 +440,7 @@ func (conn *LocalConnection) registerRemote(remote *Peer, acceptNewPeer bool) er
 	}
 
 	if conn.remote == conn.local {
-		return fmt.Errorf("Cannot connect to ourself")
+		return ErrConnectToSelf
 	}
 
 	return nil

router/connection_maker.go

@@ -231,6 +231,9 @@ func (cm *ConnectionMaker) connectToTargets(validTarget map[string]struct{}, dir
 			delete(cm.targets, address)
 			continue
 		}
+		if target.tryAfter.IsZero() {
+			continue
+		}
 		switch duration := target.tryAfter.Sub(now); {
 		case duration <= 0:
 			target.attempting = true
@@ -259,6 +262,11 @@ func (t *Target) tryNow() {
 // The delay at the nth retry is a random value in the range
 // [i-i/2,i+i/2], where i = InitialInterval * 1.5^(n-1).
 func (t *Target) retry() {
+	if t.lastError == ErrConnectToSelf {
+		t.tryAfter = time.Time{}
+		t.tryInterval = MaxInterval
+		return
+	}
 	t.tryAfter = time.Now().Add(t.tryInterval/2 + time.Duration(rand.Int63n(int64(t.tryInterval))))
 	t.tryInterval = t.tryInterval * 3 / 2
 	if t.tryInterval > MaxInterval {

router/status.go

@@ -197,7 +197,11 @@ func NewLocalConnectionStatusSlice(cm *ConnectionMaker) []LocalConnectionStatus
 				info = target.lastError.Error()
 			default:
 				state = "failed"
-				info = target.lastError.Error() + ", retry: " + target.tryAfter.String()
+				retry := "never"
+				if !target.tryAfter.IsZero() {
+					retry = target.tryAfter.String()
+				}
+				info = target.lastError.Error() + ", retry: " + retry
 			}
 			slice = append(slice, LocalConnectionStatus{address, true, state, info})
 		}