selftests: net: udpgro_fwd.sh: explicitly checking the available ping…

… feature

As Paolo pointed out, the result of ping IPv6 address depends on
the running distro. So explicitly checking the available ping feature,
as e.g. do the bareudp.sh self-tests.

Fixes: 8b3170e ("selftests: net: using ping6 for IPv6 in udpgro_fwd.sh")
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
Link: https://lore.kernel.org/r/825ee22b-4245-dbf7-d2f7-a230770d6e21@163.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/udpgro_fwd.sh

@@ -193,7 +193,8 @@ for family in 4 6; do
 		SUFFIX="64 nodad"
 		VXDEV=vxlan6
 		IPT=ip6tables
-		PING="ping6"
+		# Use ping6 on systems where ping doesn't handle IPv6
+		ping -w 1 -c 1 ::1 > /dev/null 2>&1 || PING="ping6"
 	fi
 
 	echo "IPv$family"