Fix reconnecting, through a proxy, to a closed connection

treat closed connections as dropped
Since appengine (and possibly other) environments may not have
the conn.auto_open attribute, don't rely on its presence (use getattr to read
it).

urllib3/connection.py

@@ -101,6 +101,8 @@ def _prepare_conn(self, conn):
         if getattr(self, '_tunnel_host', None):
             # TODO: Fix tunnel so it doesn't depend on self.sock state.
             self._tunnel()
+            # mark connection as not reusable
+            self.auto_open = 0
 
     def connect(self):
         conn = self._new_conn()
@@ -177,6 +179,7 @@ def connect(self):
             # Calls self._set_hostport(), so self.host is
             # self._tunnel_host below.
             self._tunnel()
+            self.auto_open = 0
 
             # Override the host with the one we're requesting data from.
             hostname = self._tunnel_host

urllib3/connectionpool.py

@@ -218,6 +218,11 @@ def _get_conn(self, timeout=None):
         if conn and is_connection_dropped(conn):
             log.info("Resetting dropped connection: %s" % self.host)
             conn.close()
+            if getattr(conn, 'auto_open', 1) == 0:
+                # this is a proxied connection that has been mutated by
+                # httplib._tunnel() and cannot be reused (since it would
+                # attempt to bypass the proxy)
+                conn = None
 
         return conn or self._new_conn()
 

urllib3/util/connection.py

@@ -22,7 +22,7 @@ def is_connection_dropped(conn):  # Platform-specific
     if sock is False:  # Platform-specific: AppEngine
         return False
     if sock is None:  # Connection already closed (such as by httplib).
-        return False
+        return True
 
     if not poll:
         if not select:  # Platform-specific: AppEngine