Add blockmanager.current with extra checks for whether we are up to date.

This uses peer state to confirm if we are up to date, as well as what
chain thinks.

blockmanager.go

@@ -304,6 +304,31 @@ func (b *blockManager) handleTxMsg(tmsg *txMsg) {
 	}
 }
 
+// current returns true if we believe we are synced with our peers, false if we
+// still have blocks to check
+func (b *blockManager) current() bool {
+	if !b.blockChain.IsCurrent() {
+		return false
+	}
+
+	// if blockChain thinks we are current and we have no syncPeer it
+	// is probably right.
+	if b.syncPeer == nil {
+		return true
+	}
+
+	_, height, err := b.server.db.NewestSha()
+	// No matter what chain thinks, if we are below the block we are
+	// syncing to we are not current.
+	// TODO(oga) we can get chain to return the height of each block when we
+	// parse an orphan, which would allow us to update the height of peers
+	// from what it was at initial handshake.
+	if err != nil || height < int64(b.syncPeer.lastBlock) {
+		return false
+	}
+	return true
+}
+
 // handleBlockMsg handles block messages from all peers.
 func (b *blockManager) handleBlockMsg(bmsg *blockMsg) {
 	// Keep track of which peer the block was sent from so the notification
@@ -407,7 +432,7 @@ func (b *blockManager) haveInventory(invVect *btcwire.InvVect) bool {
 func (b *blockManager) handleInvMsg(imsg *invMsg) {
 	// Ignore invs from peers that aren't the sync if we are not current.
 	// Helps prevent fetching a mass of orphans.
-	if imsg.peer != b.syncPeer && !b.blockChain.IsCurrent() {
+	if imsg.peer != b.syncPeer && !b.current() {
 		return
 	}
 
@@ -595,7 +620,8 @@ func (b *blockManager) handleNotifyMsg(notification *btcchain.Notification) {
 	case btcchain.NTBlockAccepted:
 		// Don't relay if we are not current. Other peers that are
 		// current should already know about it.
-		if !b.blockChain.IsCurrent() {
+
+		if !b.current() {
 			return
 		}