[PATCH v2 14/22] tasst: Add helper for getting MTU of a network interface

[David Gibson <david@gibson.dropbear.id.au>]

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 test/tasst/selftest/veth.py |  7 +++++++
 test/tasst/snh.py           | 11 ++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/test/tasst/selftest/veth.py b/test/tasst/selftest/veth.py
index 3c0b3f5b..5c8f0c0b 100644
--- a/test/tasst/selftest/veth.py
+++ b/test/tasst/selftest/veth.py
@@ -31,3 +31,10 @@ def test_ifs():
     with unconfigured_veth() as (ns1, ns2):
         exeter.assert_eq(set(ns1.ifs()), set(['lo', 'veth1']))
         exeter.assert_eq(set(ns2.ifs()), set(['lo', 'veth2']))
+
+
+@exeter.test
+def test_mtu():
+    with unconfigured_veth() as (ns1, ns2):
+        exeter.assert_eq(ns1.mtu('veth1'), 1500)
+        exeter.assert_eq(ns2.mtu('veth2'), 1500)
diff --git a/test/tasst/snh.py b/test/tasst/snh.py
index fd8f6f13..0554fbd0 100644
--- a/test/tasst/snh.py
+++ b/test/tasst/snh.py
@@ -130,6 +130,11 @@ class SimNetHost(contextlib.AbstractContextManager):
                 for ai in self.addrinfos(ifname, **criteria)
                 if 'tentative' not in ai]
 
+    def mtu(self, ifname):
+        cmd = ['ip', '-j', 'link', 'show', f'{ifname}']
+        (info,) = json.loads(self.output(*cmd))
+        return info['mtu']
+
     # Internal tests
     def test_true(self):
         with self as snh:
@@ -192,10 +197,14 @@ class SimNetHost(contextlib.AbstractContextManager):
         with self as snh:
             assert set(snh.addrs('lo')) == expected
 
+    def test_lo_mtu(self):
+        with self as snh:
+            exeter.assert_eq(snh.mtu('lo'), 65536)
+
     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_has_lo, test_lo_addrs]
+                 test_has_lo, test_lo_addrs, test_lo_mtu]
 
     @classmethod
     def selftest(cls, setup):
-- 
@@ -130,6 +130,11 @@ class SimNetHost(contextlib.AbstractContextManager):
                 for ai in self.addrinfos(ifname, **criteria)
                 if 'tentative' not in ai]
 
+    def mtu(self, ifname):
+        cmd = ['ip', '-j', 'link', 'show', f'{ifname}']
+        (info,) = json.loads(self.output(*cmd))
+        return info['mtu']
+
     # Internal tests
     def test_true(self):
         with self as snh:
@@ -192,10 +197,14 @@ class SimNetHost(contextlib.AbstractContextManager):
         with self as snh:
             assert set(snh.addrs('lo')) == expected
 
+    def test_lo_mtu(self):
+        with self as snh:
+            exeter.assert_eq(snh.mtu('lo'), 65536)
+
     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_has_lo, test_lo_addrs]
+                 test_has_lo, test_lo_addrs, test_lo_mtu]
 
     @classmethod
     def selftest(cls, setup):
-- 
2.45.2