pknock: import userspace netlink listener program

extensions/pknock/.gitignore

@@ -0,0 +1 @@
+/pknlusr

extensions/pknock/Makefile.am

@@ -1,3 +1,5 @@
 # -*- Makefile -*-
 
 include ../../Makefile.extra
+
+noinst_PROGRAMS = pknlusr

extensions/pknock/pknlusr.c

@@ -0,0 +1,91 @@
+#include <sys/socket.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include <linux/netlink.h>
+#include <linux/connector.h>
+
+#include "xt_pknock.h"
+
+#define GROUP 1
+
+struct sockaddr_nl src_addr, dest_addr;
+struct msghdr msg;
+int sock_fd;
+
+unsigned char *buf = NULL;
+
+struct xt_pknock_nl_msg *nlmsg;
+
+int main() {
+	socklen_t addrlen;
+	int status;
+	int group = GROUP;
+	struct cn_msg *cnmsg;
+
+	int i, buf_size;
+
+	char *ip;
+
+	sock_fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR);
+
+	if (sock_fd == -1) {
+		perror("socket()");
+		return 1;
+	}
+
+	memset(&src_addr, 0, sizeof(src_addr));
+	src_addr.nl_family = AF_NETLINK;
+	src_addr.nl_pid = getpid();
+	src_addr.nl_groups = group;
+
+	status = bind(sock_fd, (struct sockaddr*)&src_addr, sizeof(src_addr));
+
+	if (status == -1) {
+		close(sock_fd);
+		perror("bind()");
+		return 1;
+	}
+
+	memset(&dest_addr, 0, sizeof(dest_addr));
+	dest_addr.nl_family = AF_NETLINK;
+	dest_addr.nl_pid = 0;
+	dest_addr.nl_groups = group;
+
+	buf_size = sizeof(struct xt_pknock_nl_msg) + sizeof(struct cn_msg) + sizeof(struct nlmsghdr);
+	buf = (unsigned char *) malloc(buf_size);
+
+	if (!buf) {
+		perror("malloc()");
+		return 1;
+	}
+
+	addrlen = sizeof(dest_addr);
+
+	while(1) {
+
+		memset(buf, 0, buf_size);
+
+		status = recvfrom(sock_fd, buf, buf_size, 0, (struct sockaddr *)&dest_addr, &addrlen);
+
+		if (status <= 0) {
+			perror("recvfrom()");
+			return 1;
+		}
+
+	nlmsg = (struct xt_pknock_nl_msg *) (buf + sizeof(struct cn_msg) + sizeof(struct nlmsghdr));
+
+	ip = (char *)inet_ntoa((struct in_addr *) htonl(nlmsg->peer_ip));
+		printf("rule_name: %s - ip %s\n", nlmsg->rule_name, ip);
+
+	}
+
+	close(sock_fd);
+
+	free(buf);
+
+	return 0;
+}