From 441d15a4825c44bfea70e6e2b8317f2691dbf1c6 Mon Sep 17 00:00:00 2001
From: Kristof Provost <kp@FreeBSD.org>
Date: Mon, 26 Jul 2021 13:51:22 +0200
Subject: [PATCH] bridge tests: verify that we can't change MTU of bridge
 member interfaces

Reviewed by:	donner
Sponsored by:	Rubicon Communications, LLC ("Netgate")
Differential Revision:	https://reviews.freebsd.org/D31305
---
 tests/sys/net/if_bridge_test.sh | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tests/sys/net/if_bridge_test.sh b/tests/sys/net/if_bridge_test.sh
index da797f4fd39..3c0a31ca107 100755
--- a/tests/sys/net/if_bridge_test.sh
+++ b/tests/sys/net/if_bridge_test.sh
@@ -577,6 +577,11 @@ mtu_body()
 	check_mtu ${bridge} 2000
 	check_mtu ${gif} 2000
 	check_mtu ${epair}a 2000
+
+	# We're not allowed to change the MTU of a member interface
+	atf_check -s exit:1 -e ignore \
+		ifconfig ${epair}a mtu 1900
+	check_mtu ${epair}a 2000
 }
 
 mtu_cleanup()