selftests/net: convert arp_ndisc_untracked_subnets.sh to run it in unique namespace

Here is the test result after conversion.

2 tests also failed without this patch

]# ./arp_ndisc_untracked_subnets.sh
TEST: test_arp: accept_arp=0 [ OK ]
TEST: test_arp: accept_arp=1 [ OK ]
TEST: test_arp: accept_arp=2 same_subnet=0 [ OK ]
TEST: test_arp: accept_arp=2 same_subnet=1 [ OK ]
TEST: test_ndisc: accept_untracked_na=0 [ OK ]
TEST: test_ndisc: accept_untracked_na=1 [ OK ]
TEST: test_ndisc: accept_untracked_na=2 same_subnet=0 [ OK ]
TEST: test_ndisc: accept_untracked_na=2 same_subnet=1 [ OK ]

Acked-by: David Ahern <[e-mail]>
Signed-off-by: Hangbin Liu <[e-mail]>
Signed-off-by: Paolo Abeni <[e-mail]>

tools/testing/selftests/net/arp_ndisc_untracked_subnets.sh

···
 # garp to the router. Router accepts or ignores based on its arp_accept
 # or accept_untracked_na configuration.
 
+source lib.sh
+
 TESTS="arp ndisc"
 
-ROUTER_NS="ns-router"
-ROUTER_NS_V6="ns-router-v6"
 ROUTER_INTF="veth-router"
 ROUTER_ADDR="10.0.10.1"
 ROUTER_ADDR_V6="2001:db8:abcd:0012::1"
 
-HOST_NS="ns-host"
-HOST_NS_V6="ns-host-v6"
 HOST_INTF="veth-host"
 HOST_ADDR="10.0.10.2"
 HOST_ADDR_V6="2001:db8:abcd:0012::2"
···
 PREFIX_WIDTH_V6=64
 
 cleanup() {
-	ip netns del ${HOST_NS}
-	ip netns del ${ROUTER_NS}
+	cleanup_ns ${HOST_NS} ${ROUTER_NS}
 }
 
 cleanup_v6() {
-	ip netns del ${HOST_NS_V6}
-	ip netns del ${ROUTER_NS_V6}
+	cleanup_ns ${HOST_NS_V6} ${ROUTER_NS_V6}
 }
 
 setup() {
···
 	local arp_accept=$1
 
 	# Set up two namespaces
-	ip netns add ${ROUTER_NS}
-	ip netns add ${HOST_NS}
+	setup_ns HOST_NS ROUTER_NS
 
 	# Set up interfaces veth0 and veth1, which are pairs in separate
 	# namespaces. veth0 is veth-router, veth1 is veth-host.
···
 	local accept_untracked_na=$1
 
 	# Set up two namespaces
-	ip netns add ${ROUTER_NS_V6}
-	ip netns add ${HOST_NS_V6}
+	setup_ns HOST_NS_V6 ROUTER_NS_V6
 
 	# Set up interfaces veth0 and veth1, which are pairs in separate
 	# namespaces. veth0 is veth-router, veth1 is veth-host.