vyos.template: T3418: add new is_interface helper function

2 files changed, 15 insertions, 0 deletions

diff --git a/python/vyos/template.py b/python/vyos/template.py
index 85e4d12b3..7810f5edd 100644
--- a/python/vyos/template.py
+++ b/python/vyos/template.py
@@ -207,6 +207,11 @@ def network_from_ipv4(address):
     cidr_prefix = ip_interface(f'{address}/{netmask}').network
     return address_from_cidr(cidr_prefix)
 
+@register_filter('is_interface')
+def is_interface(interface):
+    """ Check if parameter is a valid local interface name """
+    return os.path.exists(f'/sys/class/net/{interface}')
+
 @register_filter('is_ip')
 def is_ip(addr):
     """ Check addr if it is an IPv4 or IPv6 address """
diff --git a/src/tests/test_template.py b/src/tests/test_template.py
index 7800d007f..67c0fe84a 100644
--- a/src/tests/test_template.py
+++ b/src/tests/test_template.py
@@ -14,13 +14,23 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+import os
 import vyos.template
+
 from unittest import TestCase
 
 class TestVyOSTemplate(TestCase):
     def setUp(self):
         pass
 
+    def test_is_interface(self):
+        for interface in ['lo', 'eth0']:
+            if os.path.exists(f'/sys/class/net/{interface}'):
+                self.assertTrue(vyos.template.is_interface(interface))
+            else:
+                self.assertFalse(vyos.template.is_interface(interface))
+        self.assertFalse(vyos.template.is_interface('non-existent'))
+
     def test_is_ip(self):
         self.assertTrue(vyos.template.is_ip('192.0.2.1'))
         self.assertTrue(vyos.template.is_ip('2001:db8::1'))