tests/netgraph: Add a test for races between if_detach() and vnet_if_return()

A ng_eiface(4) or physical interface does not involve the cloner hence
the detaching is a bit different with epair(4). Add more tests to cover
that.

PR:		292993
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D56609

tests/sys/netgraph/Makefile

@@ -17,6 +17,8 @@ ATF_TESTS_C+=	basic		\
 		socket		\
 		vlan_rotate	\
 
+ATF_TESTS_SH+=	eiface_test
+
 SRCS.basic=	basic.c util.c
 SRCS.bridge=	bridge.c util.c
 SRCS.hub=	hub.c util.c

tests/sys/netgraph/eiface_test.sh

@@ -0,0 +1,67 @@
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2026 Zhenlei Huang <zlei@FreeBSD.org>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+. $(atf_get_srcdir)/../common/vnet.subr
+
+atf_test_case "pr292993" "cleanup"
+pr292993_head()
+{
+	atf_set descr 'Test for PR 292993'
+	atf_set require.user root
+}
+
+pr292993_body()
+{
+	vnet_init
+
+	for i in `seq 1 10`
+	do
+		ngeth=$(ngctl -f - <<__EOF__ | awk '$1 == "Args:" {print substr($2, 2, length($2)-2)}')
+mkpeer . eiface path_$i ether
+msg .path_$i getifname
+__EOF__
+		# Sanity check
+		atf_check -s exit:0 -o ignore \
+			ifconfig $ngeth
+		jail -c vnet name="eiface_destroy_$i" path=/ \
+		    vnet.interface="$ngeth" exec.start="sleep 0.1" &
+		pid=$!
+		sleep 0.1
+		ngctl shutdown ${ngeth}:
+		wait $pid
+	done
+	true
+}
+
+pr292993_cleanup()
+{
+	vnet_cleanup
+}
+
+atf_init_test_cases()
+{
+	atf_add_test_case "pr292993"
+}