[PATCH 18/27] 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/exesite.py   | 11 ++++++++++-
 test/tasst/meta/veth.py |  9 ++++++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/test/tasst/exesite.py b/test/tasst/exesite.py
index 246f9b3f..63872c34 100644
--- a/test/tasst/exesite.py
+++ b/test/tasst/exesite.py
@@ -124,6 +124,11 @@ class Site(contextlib.AbstractContextManager):
                 for ai in self.addrinfos(ifname, **criteria)
                 if 'tentative' not in ai]
 
+    def mtu(self, ifname):
+        self.require_cmds('ip')
+        (info,) = json.loads(self.output(f'ip -j link show {ifname}'))
+        return info['mtu']
+
 
 def test_site(sitefn):
     def test_true(s):
@@ -184,10 +189,14 @@ def test_site(sitefn):
         with s as site:
             assert_eq_unordered(site.addrs('lo'), expected)
 
+    def test_lo_mtu(s):
+        with s as site:
+            assert_eq(site.mtu('lo'), 65536)
+
     return test_output(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)(sitefn)
+                       test_has_lo, test_lo_addrs, test_lo_mtu)(sitefn)
 
 
 def test_isolated_site(sitefn):
diff --git a/test/tasst/meta/veth.py b/test/tasst/meta/veth.py
index 9cef6271..053bd9c8 100644
--- a/test/tasst/meta/veth.py
+++ b/test/tasst/meta/veth.py
@@ -13,7 +13,7 @@ meta/veth.py - Test various veth configurations
 
 import contextlib
 
-from avocado_classless.test import assert_eq_unordered, test
+from avocado_classless.test import assert_eq, assert_eq_unordered, test
 
 from tasst.nstool import unshare_site
 
@@ -31,3 +31,10 @@ def test_ifs():
     with unconfigured_veth() as (ns1, ns2):
         assert_eq_unordered(ns1.ifs(), ['lo', 'veth1'])
         assert_eq_unordered(ns2.ifs(), ['lo', 'veth2'])
+
+
+@test
+def test_mtu():
+    with unconfigured_veth() as (ns1, ns2):
+        assert_eq(ns1.mtu('veth1'), 1500)
+        assert_eq(ns2.mtu('veth2'), 1500)
-- 
@@ -13,7 +13,7 @@ meta/veth.py - Test various veth configurations
 
 import contextlib
 
-from avocado_classless.test import assert_eq_unordered, test
+from avocado_classless.test import assert_eq, assert_eq_unordered, test
 
 from tasst.nstool import unshare_site
 
@@ -31,3 +31,10 @@ def test_ifs():
     with unconfigured_veth() as (ns1, ns2):
         assert_eq_unordered(ns1.ifs(), ['lo', 'veth1'])
         assert_eq_unordered(ns2.ifs(), ['lo', 'veth2'])
+
+
+@test
+def test_mtu():
+    with unconfigured_veth() as (ns1, ns2):
+        assert_eq(ns1.mtu('veth1'), 1500)
+        assert_eq(ns2.mtu('veth2'), 1500)
-- 
2.41.0