netns_helper.sh: use 'ping -6' when ping6 is not avaliable

ping6 has been merged into ping since 2015 by using "ping -6" in some distrubiton like open embeded, they droped ping6 completely this patch will let both "ping -6" and ping6 work

---
 testcases/kernel/containers/netns/netns_helper.sh | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

index 6aea10b..e3f60e1 100755
@@ -168,7 +168,12 @@ netns_setup()
 	ipv6)
 		IFCONF_IN6_ARG="inet6 add"
 		IP0=$6; IP1=$7;
-		tping="ping6"; NETMASK=64
+		if which ping6 >/dev/null 2>&1; then
+		    tping="ping6" 
+		else
+		    tping="ping -6"
+		fi
+		NETMASK=64
 		;;
 	*)
 		tst_brkm TBROK "second argument must be an ip version (ipv4|ipv6)"

1.9.1

Hi Lei,

I raised similar patch for tst_ping() (tst_net.sh) in the past [1] (it wasn't accepted and I wouldn't be for accepting it now).

ping is used in many scripts (most of them are "network tests", which use tst_net.sh, netns_helper.sh is the only exception), so it'd be good to have general solution.

Old iputils versions (before s20150815) didn't have -4/-6 switches, new ones leave creating ping6 symlink to distros (see [2]). We could use simple
solution: just to require ping6 (tst_test_cmds ping6), as symlink can be done by user anywhere in the path (even with root access, which is expected anyway for many tests) + document it in testcases/network/README.md.
I'd prefer this solution.

Or we can create some helper, which does this check (not sure the name, tst_ping() is already used).

Kind regards,
Petr

[1] http://lists.linux.it/pipermail/ltp/2016-December/003312.html
[2] https://github.com/iputils/iputils/commit/ebad35fee3de851b809c7b72ccc654a72b6af61d

Hi Lei,

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