tools: hv: introduce -n/--no-daemon option

All tools/hv daemons do mandatory daemon() on startup. However, no pidfile
is created, this make it difficult for an init system to track such daemons.
Modern linux distros use systemd as their init system. It can handle the
daemonizing by itself, however, it requires a daemon to stay in foreground
for that. Some distros already carry distro-specific patch for hv tools
which switches off daemon().

Introduce -n/--no-daemon option for all 3 daemons in hv/tools. Parse options
with getopt() to make this part easily expandable.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tools/hv/hv_kvp_daemon.c

@@ -43,6 +43,7 @@
 #include <fcntl.h>
 #include <dirent.h>
 #include <net/if.h>
+#include <getopt.h>
 
 /*
  * KVP protocol: The user mode component first registers with the
@@ -1417,7 +1418,15 @@ netlink_send(int fd, struct cn_msg *msg)
 	return sendmsg(fd, &message, 0);
 }
 
-int main(void)
+void print_usage(char *argv[])
+{
+	fprintf(stderr, "Usage: %s [options]\n"
+		"Options are:\n"
+		"  -n, --no-daemon        stay in foreground, don't daemonize\n"
+		"  -h, --help             print this help\n", argv[0]);
+}
+
+int main(int argc, char *argv[])
 {
 	int fd, len, nl_group;
 	int error;
@@ -1435,9 +1444,30 @@ int main(void)
 	struct hv_kvp_ipaddr_value *kvp_ip_val;
 	char *kvp_recv_buffer;
 	size_t kvp_recv_buffer_len;
+	int daemonize = 1, long_index = 0, opt;
 
-	if (daemon(1, 0))
+	static struct option long_options[] = {
+		{"help",	no_argument,	   0,  'h' },
+		{"no-daemon",	no_argument,	   0,  'n' },
+		{0,		0,		   0,  0   }
+	};
+
+	while ((opt = getopt_long(argc, argv, "hn", long_options,
+				  &long_index)) != -1) {
+		switch (opt) {
+		case 'n':
+			daemonize = 0;
+			break;
+		case 'h':
+		default:
+			print_usage(argv);
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	if (daemonize && daemon(1, 0))
 		return 1;
+
 	openlog("KVP", 0, LOG_USER);
 	syslog(LOG_INFO, "KVP starting; pid is:%d", getpid());