pknlusr: use NLMSG macros and proper types, rather than arithmetic on char pointers

Signed-off-by: Jeremy Sowden <jeremy@azazel.net>

diff --git a/extensions/pknock/pknlusr.c b/extensions/pknock/pknlusr.c
index b53dc648515ea1cd5052a0e4877e3b2dd4603656..6fe1d4a337e708b2cd9faa6ab5aa37f860443d13 100644 (file)
--- a/extensions/pknock/pknlusr.c
+++ b/extensions/pknock/pknlusr.c
@@ -17,8 +17,11 @@ int main(void)
        int status;
        int group = GROUP;
        struct sockaddr_nl local_addr = {.nl_family = AF_NETLINK};
-       int sock_fd, buf_size;
-       unsigned char *buf;
+       int sock_fd;
+       size_t nlmsg_size;
+       struct nlmgrhdr *nlmsg;
+       struct cn_msg *cn_msg;
+       struct xt_pknock_nl_msg *pknock_msg;
 
        sock_fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR);
 
@@ -35,34 +38,30 @@ int main(void)
                return 1;
        }
 
-       buf_size = sizeof(struct xt_pknock_nl_msg) + sizeof(struct cn_msg) + sizeof(struct nlmsghdr);
-       buf = malloc(buf_size);
-
-       if (!buf) {
+       nlmsg_size = NLMSG_SPACE(sizeof(*cn_msg) + sizeof(*pknock_msg));
+       nlmsg = malloc(nlmsg_size);
+       if (!nlmsg) {
                perror("malloc()");
                return 1;
        }
 
        while(1) {
-               struct xt_pknock_nl_msg *nlmsg;
                const char *ip;
                char ipbuf[48];
 
-               memset(buf, 0, buf_size);
-               status = recv(sock_fd, buf, buf_size, 0);
+               memset(nlmsg, 0, nlmsg_size);
+               status = recv(sock_fd, nlmsg, nlmsg_size, 0);
                if (status <= 0) {
                        perror("recv()");
                        return 1;
                }
-               nlmsg = (struct xt_pknock_nl_msg *)(buf + sizeof(struct cn_msg) + sizeof(struct nlmsghdr));
-               ip = inet_ntop(AF_INET, &nlmsg->peer_ip, ipbuf, sizeof(ipbuf));
-               printf("rule_name: %s - ip %s\n", nlmsg->rule_name, ip);
-
+               cn_msg = NLMSG_DATA(nlmsg);
+               pknock_msg = (struct xt_pknock_nl_msg *)(cn_msg->data);
+               ip = inet_ntop(AF_INET, &pknock_msg->peer_ip, ipbuf, sizeof(ipbuf));
+               printf("rule_name: %s - ip %s\n", pknock_msg->rule_name, ip);
        }
 
        close(sock_fd);
-
-       free(buf);
-
+       free(nlmsg);
        return 0;
 }