From d724a65ca08d5b1c16da1f2ce3fd0b50bd519dec Mon Sep 17 00:00:00 2001
From: Ivan Alejandro <ivanalejandro0@gmail.com>
Date: Mon, 10 Mar 2014 17:29:52 -0300
Subject: Check for DNS resolution after connecting EIP.

[Closes #5301]
---
 changes/feature_check-for-dns-resolution |  1 +
 src/leap/bitmask/gui/mainwindow.py       | 52 +++++++++++++++++++++++++++++++-
 2 files changed, 52 insertions(+), 1 deletion(-)
 create mode 100644 changes/feature_check-for-dns-resolution

diff --git a/changes/feature_check-for-dns-resolution b/changes/feature_check-for-dns-resolution
new file mode 100644
index 00000000..f0e2bf3e
--- /dev/null
+++ b/changes/feature_check-for-dns-resolution
@@ -0,0 +1 @@
+- After connecting EIP check for DNS resolution and warn the user on error. Closes #5301.
diff --git a/src/leap/bitmask/gui/mainwindow.py b/src/leap/bitmask/gui/mainwindow.py
index 7cec4831..758bff4e 100644
--- a/src/leap/bitmask/gui/mainwindow.py
+++ b/src/leap/bitmask/gui/mainwindow.py
@@ -18,13 +18,14 @@
 Main window for Bitmask.
 """
 import logging
+import socket
 
 from threading import Condition
 from datetime import datetime
 
 from PySide import QtCore, QtGui
 from zope.proxy import ProxyBase, setProxiedObject
-from twisted.internet import threads
+from twisted.internet import reactor, threads
 from twisted.internet.defer import CancelledError
 
 from leap.bitmask import __version__ as VERSION
@@ -1456,6 +1457,55 @@ class MainWindow(QtGui.QMainWindow):
         """
         self._eip_connection.qtsigs.connected_signal.emit()
 
+        # check for connectivity
+        provider_config = self._get_best_provider_config()
+        domain = provider_config.get_domain()
+        self._check_name_resolution(domain)
+
+    def _check_name_resolution(self, domain):
+        """
+        Check if we can resolve the given domain name.
+
+        :param domain: the domain to check.
+        :type domain: str
+        """
+        def do_check():
+            """
+            Try to resolve the domain name.
+            """
+            socket.gethostbyname(domain.encode('idna'))
+
+        def check_err(failure):
+            """
+            Errback handler for `do_check`.
+
+            :param failure: the failure that triggered the errback.
+            :type failure: twisted.python.failure.Failure
+            """
+            logger.error(repr(failure))
+            logger.error("Can't resolve hostname.")
+
+            msg = self.tr(
+                "The server at {0} can't be found, because the DNS lookup "
+                "failed. DNS is the network service that translates a "
+                "website's name to its Internet address. Either your computer "
+                "is having trouble connecting to the network, or you are "
+                "missing some helper files that are needed to securely use "
+                "DNS while {1} is active. To install these helper files, quit "
+                "this application and start it again."
+            ).format(domain, self._eip_name)
+
+            show_err = lambda: QtGui.QMessageBox.critical(
+                self, self.tr("Connection Error"), msg)
+            reactor.callLater(0, show_err)
+
+            # python 2.7.4 raises socket.error
+            # python 2.7.5 raises socket.gaierror
+            failure.trap(socket.gaierror, socket.error)
+
+        d = threads.deferToThread(do_check)
+        d.addErrback(check_err)
+
     def _try_autostart_eip(self):
         """
         Tries to autostart EIP
-- 
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