vyos.ifconfig: T2738: can only read from a file when it exists

When IPv6 is disbaled on an interface also the sysfs files related to IPv6 for
this interface vanish. We need to check if the file exists before we read it.

(cherry picked from commit 672a70613aa6c987bca417f93b587eddccbfd53a)

1 files changed, 9 insertions, 10 deletions

diff --git a/python/vyos/ifconfig/control.py b/python/vyos/ifconfig/control.py
index 43136f361..6815074f8 100644
--- a/python/vyos/ifconfig/control.py
+++ b/python/vyos/ifconfig/control.py
@@ -18,11 +18,12 @@ import os
 from inspect import signature
 from inspect import _empty
 
-from vyos import debug
+from vyos.ifconfig.section import Section
 from vyos.util import popen
 from vyos.util import cmd
-from vyos.ifconfig.section import Section
-
+from vyos.util import read_file
+from vyos.util import write_file
+from vyos import debug
 
 class Control(Section):
     _command_get = {}
@@ -116,20 +117,18 @@ class Control(Section):
         Provide a single primitive w/ error checking for reading from sysfs.
         """
         value = None
-        with open(filename, 'r') as f:
-            value = f.read().rstrip('\n')
-
-        self._debug_msg("read '{}' < '{}'".format(value, filename))
+        if os.path.exists(filename):
+            value = read_file(filename)
+            self._debug_msg("read '{}' < '{}'".format(value, filename))
         return value
 
     def _write_sysfs(self, filename, value):
         """
         Provide a single primitive w/ error checking for writing to sysfs.
         """
-        self._debug_msg("write '{}' > '{}'".format(value, filename))
         if os.path.isfile(filename):
-            with open(filename, 'w') as f:
-                f.write(str(value))
+            write_file(filename, str(value))
+            self._debug_msg("write '{}' > '{}'".format(value, filename))
             return True
         return False