selftests/bpf/xdp_redirect_multi: Use arping to accurate the arp number

The arp request number triggered by ping none exist address is not accurate,
which may lead the test false negative/positive. Change to use arping to
accurate the arp number. Also do not use grep pattern match for dot.

Fixes: d232924 ("selftests/bpf: Add xdp_redirect_multi test")
Suggested-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211027033553.962413-3-liuhangbin@gmail.com

tools/testing/selftests/bpf/test_xdp_redirect_multi.sh

@@ -127,7 +127,7 @@ do_ping_tests()
 	ip netns exec ns3 tcpdump -i veth0 -nn -l -e &> ${LOG_DIR}/ns1-3_${mode}.log &
 	sleep 0.5
 	# ARP test
-	ip netns exec ns1 ping 192.0.2.254 -i 0.1 -c 4 &> /dev/null
+	ip netns exec ns1 arping -q -c 2 -I veth0 192.0.2.254
 	# IPv4 test
 	ip netns exec ns1 ping 192.0.2.253 -i 0.1 -c 4 &> /dev/null
 	# IPv6 test
@@ -136,13 +136,13 @@ do_ping_tests()
 	pkill -9 tcpdump
 
 	# All netns should receive the redirect arp requests
-	[ $(grep -c "who-has 192.0.2.254" ${LOG_DIR}/ns1-1_${mode}.log) -gt 4 ] && \
+	[ $(grep -cF "who-has 192.0.2.254" ${LOG_DIR}/ns1-1_${mode}.log) -eq 4 ] && \
 		test_pass "$mode arp(F_BROADCAST) ns1-1" || \
 		test_fail "$mode arp(F_BROADCAST) ns1-1"
-	[ $(grep -c "who-has 192.0.2.254" ${LOG_DIR}/ns1-2_${mode}.log) -le 4 ] && \
+	[ $(grep -cF "who-has 192.0.2.254" ${LOG_DIR}/ns1-2_${mode}.log) -eq 2 ] && \
 		test_pass "$mode arp(F_BROADCAST) ns1-2" || \
 		test_fail "$mode arp(F_BROADCAST) ns1-2"
-	[ $(grep -c "who-has 192.0.2.254" ${LOG_DIR}/ns1-3_${mode}.log) -le 4 ] && \
+	[ $(grep -cF "who-has 192.0.2.254" ${LOG_DIR}/ns1-3_${mode}.log) -eq 2 ] && \
 		test_pass "$mode arp(F_BROADCAST) ns1-3" || \
 		test_fail "$mode arp(F_BROADCAST) ns1-3"