[PATCH xtables-addons 2/3] pknock: pknlusr: fix hard-coded netlink multicast group ID.

[Jeremy Sowden <jeremy@azazel.net>]

The group ID used by xt_pknock is configurable, but pknlusr hard-codes
it to 1.  Modify pknlusr to accept an optional ID from the command-line.

Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
---
 extensions/pknock/pknlusr.c | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/extensions/pknock/pknlusr.c b/extensions/pknock/pknlusr.c
index 161a9610a018..ca3af835c9a8 100644
--- a/extensions/pknock/pknlusr.c
+++ b/extensions/pknock/pknlusr.c
@@ -7,6 +7,8 @@
 #include <arpa/inet.h>
 #include <linux/netlink.h>
 #include <linux/connector.h>
+#include <libgen.h>
+#include <limits.h>
 
 #include "xt_pknock.h"
 
@@ -19,7 +21,19 @@ static unsigned char *buf;
 
 static struct xt_pknock_nl_msg *nlmsg;
 
-int main(void)
+static void
+usage(const char *argv0)
+{
+	char *prog;
+	if (!(prog = strdup (argv0))) {
+		perror("strdup()");
+	} else {
+		fprintf(stderr, "%s [ group-id ]\n", basename(prog));
+		free(prog);
+	}
+}
+
+int main(int argc, char **argv)
 {
 	socklen_t addrlen;
 	int status;
@@ -30,6 +44,23 @@ int main(void)
 	const char *ip;
 	char ipbuf[48];
 
+	if (argc > 2) {
+		usage(argv[0]);
+		exit(EXIT_FAILURE);
+	}
+
+	if (argc == 2) {
+		long n;
+		char *end;
+
+		n = strtol(argv[1], &end, 10);
+		if (*end || n < INT_MIN || n > INT_MAX) {
+			usage(argv[0]);
+			exit(EXIT_FAILURE);
+		}
+		group = n;
+	}
+
 	sock_fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR);
 
 	if (sock_fd == -1) {
-- 
2.28.0