selftests: netfilter: fix udpclash tool hang

Yi Chen reports that 'udpclash' loops forever depending on compiler
(and optimization level used); while (x == 1) gets optimized into
for (;;).  Add volatile qualifier to avoid that.

While at it, also run it under timeout(1) and fix the resize script
to not ignore the timeout passed as second parameter to insert_flood.

Reported-by: Yi Chen <yiche@redhat.com>
Suggested-by: Yi Chen <yiche@redhat.com>
Fixes: 78a5883635 ("selftests: netfilter: add conntrack clash resolution test case")
Signed-off-by: Florian Westphal <fw@strlen.de>

tools/testing/selftests/net/netfilter/conntrack_clash.sh

@@ -99,7 +99,7 @@ run_one_clash_test()
 	local entries
 	local cre
 
-	if ! ip netns exec "$ns" ./udpclash $daddr $dport;then
+	if ! ip netns exec "$ns" timeout 30 ./udpclash $daddr $dport;then
 		echo "INFO: did not receive expected number of replies for $daddr:$dport"
 		ip netns exec "$ctns" conntrack -S
 		# don't fail: check if clash resolution triggered after all.

tools/testing/selftests/net/netfilter/conntrack_resize.sh

@@ -187,7 +187,7 @@ ct_udpclash()
 	[ -x udpclash ] || return
 
         while [ $now -lt $end ]; do
-		ip netns exec "$ns" ./udpclash 127.0.0.1 $((RANDOM%65536)) > /dev/null 2>&1
+		ip netns exec "$ns" timeout 30 ./udpclash 127.0.0.1 $((RANDOM%65536)) > /dev/null 2>&1
 
 		now=$(date +%s)
 	done
@@ -277,6 +277,7 @@ check_taint()
 insert_flood()
 {
 	local n="$1"
+	local timeout="$2"
 	local r=0
 
 	r=$((RANDOM%$insert_count))
@@ -302,7 +303,7 @@ test_floodresize_all()
 	read tainted_then < /proc/sys/kernel/tainted
 
 	for n in "$nsclient1" "$nsclient2";do
-		insert_flood "$n" &
+		insert_flood "$n" "$timeout" &
 	done
 
 	# resize table constantly while flood/insert/dump/flushs

tools/testing/selftests/net/netfilter/udpclash.c

@@ -29,7 +29,7 @@ struct thread_args {
 	int sockfd;
 };
 
-static int wait = 1;
+static volatile int wait = 1;
 
 static void *thread_main(void *varg)
 {