generic/131: dynamically allocate tcp listen port to avoid port clashes

Current port selection algorithm is bound to have port clashes. To
eliminate clashes, let server pick an unused port and report it on
stdout.

Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

src/locktest.c

@@ -95,7 +95,7 @@ static char	*filename = 0;
 static int	debug = 0;
 static int	server = 1;
 static int	maxio = 8192;
-static int	port = 7890;
+static int	port = 0;
 static int 	testnumber = -1;
 static int	saved_errno = 0;
 
@@ -899,6 +899,20 @@ main(int argc, char *argv[])
 	    /*NOTREACHED*/
 	}
 
+	if (port == 0) {
+	        socklen_t addr_len = sizeof(myAddr);
+
+		if (getsockname(s_fd, &myAddr, &addr_len)) {
+		    perror("getsockname");
+		    exit(1);
+		}
+
+		port = ntohs(myAddr.sin_port);
+	}
+
+	printf("server port: %d\n", port);
+	fflush(stdout);
+
 	c_fd = accept(s_fd, NULL, NULL);
 	if (c_fd == INVALID_SOCKET) {
 	    perror("accept");

tests/generic/131

@@ -49,21 +49,18 @@ _require_test_fcntl_advisory_locks
 
 TESTFILE=$TEST_DIR/lock_file
 
-# Grab a port which is hopefully unused
-if [ $$ -gt 1024 -a $$ -lt 32000 ]; then
-    PORT=$$
-elif [ $$ -lt 1024 ]; then
-    PORT=$(($$+1024))
-elif [ $$ -gt 32000 ]; then
-    PORT=$(($$%30000+1024))
-fi
-
 # Start the server
-src/locktest -p $PORT $TESTFILE 2>&1 > $TEST_DIR/server.out &
+src/locktest $TESTFILE 2>&1 > $TEST_DIR/server.out &
 locktest_pid1=$!
 
 sleep 1
 
+PORT=$(cat $TEST_DIR/server.out | grep "^server port: " | awk '{print $3}')
+if [ -z $PORT ]; then
+	echo "Could not get server port"
+	exit 1
+fi
+
 # Start the client
 src/locktest -p $PORT -h localhost $TESTFILE 2>&1 > $TEST_DIR/client.out
 locktest_pid2=$!