network: minor fix

lib/network.py

@@ -835,7 +835,6 @@ class Network(util.DaemonThread):
             if b:
                 interface.mode = 'default'
                 interface.blockchain = b
-                #interface.print_error('passed checkpoint', b.filename)
                 self.queue_request('blockchain.headers.subscribe', [], interface)
             else:
                 interface.print_error("checkpoint failed")
@@ -849,13 +848,14 @@ class Network(util.DaemonThread):
                 interface.mode = 'binary'
                 interface.print_error("binary search")
                 next_height = (interface.bad + interface.good) // 2
+            else:
+                if height == 0:
+                    self.connection_down(interface.server)
+                    next_height = None
                 else:
                     interface.bad = height
                     delta = interface.tip - height
-                next_height = interface.tip - 2 * delta
+                    next_height = max(0, interface.tip - 2 * delta)
-                if next_height < 0:
-                    interface.print_error("header didn't connect, dismissing interface")
-                    self.connection_down(interface.server)
         elif interface.mode == 'binary':
             if can_connect:
                 interface.good = height