rpc: avoid possible recursion in create_connection

There was a recursion in RPCClient.create_connection() which under rare
circumstances would not have an ending condition. This commit removes
it and cleans up the code a bit as well.

https://pagure.io/freeipa/issue/6796

Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>

ipalib/rpc.py

@@ -999,13 +999,18 @@ class RPCClient(Connectible):
             # No session key, do full Kerberos auth
             pass
         urls = self.get_url_list(rpc_uri)
-        serverproxy = None
-        for url in urls:
-            kw = {
+
+        proxy_kw = {
             'allow_none': True,
             'encoding': 'UTF-8',
             'verbose': verbose
         }
+
+        for url in urls:
+            # should we get ProtocolError (=> error in HTTP response) and
+            # 401 (=> Unauthorized), we'll be re-trying with new session
+            # cookies several times
+            for _try_num in range(0, 5):
                 if url.startswith('https://'):
                     if delegate:
                         transport_class = DelegatedKerbTransport
@@ -1013,11 +1018,11 @@ class RPCClient(Connectible):
                         transport_class = KerbTransport
                 else:
                     transport_class = LanguageAwareTransport
-            kw['transport'] = transport_class(protocol=self.protocol,
-                                              service='HTTP', ccache=ccache)
+                proxy_kw['transport'] = transport_class(
+                    protocol=self.protocol, service='HTTP', ccache=ccache)
                 self.log.info('trying %s' % url)
                 setattr(context, 'request_url', url)
-            serverproxy = self.server_proxy_class(url, **kw)
+                serverproxy = self.server_proxy_class(url, **proxy_kw)
                 if len(urls) == 1:
                     # if we have only 1 server and then let the
                     # main requester handle any errors. This also means it
@@ -1039,7 +1044,7 @@ class RPCClient(Connectible):
                                 server=url,
                             )
                     # We don't care about the response, just that we got one
-                break
+                    return serverproxy
                 except errors.KerberosError:
                     # kerberos error on one server is likely on all
                     raise
@@ -1050,26 +1055,29 @@ class RPCClient(Connectible):
                         try:
                             delete_persistent_client_session_data(principal)
                         except Exception:
-                        # This shouldn't happen if we have a session but it isn't fatal.
+                            # This shouldn't happen if we have a session but
+                            # it isn't fatal.
                             pass
-                    return self.create_connection(
-                        ccache, verbose, fallback, delegate)
+                        # try the same url once more with a new session cookie
+                        continue
                     if not fallback:
                         raise
                     else:
-                    self.log.info('Connection to %s failed with %s', url, e)
-                serverproxy = None
+                        self.log.info(
+                            'Connection to %s failed with %s', url, e)
+                    # try the next url
+                    break
                 except Exception as e:
                     if not fallback:
                         raise
                     else:
-                    self.log.info('Connection to %s failed with %s', url, e)
-                serverproxy = None
-
-        if serverproxy is None:
+                        self.log.info(
+                            'Connection to %s failed with %s', url, e)
+                    # try the next url
+                    break
+        # finished all tries but no serverproxy was found
         raise NetworkError(uri=_('any of the configured servers'),
                            error=', '.join(urls))
-        return serverproxy
 
     def destroy_connection(self):
         conn = getattr(context, self.id, None)