[PATCH v2 10/22] tasst: Add helper to get network interface names for a site

Start adding convenience functions for handling sites as places with
network setup with a simple helper which lists the network interface names
for a site.

Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
 test/tasst/snh.py | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/test/tasst/snh.py b/test/tasst/snh.py
index dfbe2c84..8ee9802a 100644
--- a/test/tasst/snh.py
+++ b/test/tasst/snh.py
@@ -13,6 +13,7 @@ tasst/snh.py - Simulated network hosts for testing
 
 
 import contextlib
+import json
 import subprocess
 import sys
 
@@ -105,6 +106,10 @@ class SimNetHost(contextlib.AbstractContextManager):
               file=sys.stderr)
         return proc
 
+    def ifs(self):
+        info = json.loads(self.output('ip', '-j', 'link',
'show'))
+        return [i['ifname'] for i in info]
+
     # Internal tests
     def test_true(self):
         with self as snh:
@@ -157,9 +162,14 @@ class SimNetHost(contextlib.AbstractContextManager):
                     pass
             exeter.assert_raises(subprocess.TimeoutExpired, run_timeout)
 
+    def test_has_lo(self):
+        with self as snh:
+            assert 'lo' in snh.ifs()
+
     SELFTESTS = [test_true, test_false, test_echo, test_timeout,
                  test_bg_true, test_bg_false, test_bg_echo, test_bg_timeout,
-                 test_bg_context_timeout]
+                 test_bg_context_timeout,
+                 test_has_lo]
 
     @classmethod
     def selftest(cls, setup):
-- 
2.45.2