How do I read kernel audit messages using NETLINK_AUDIT in user space

[Bhat, Jayalakshmi Manjunath]

Hi All,

I am trying to read kernel audit messages specially generated by XFRM in user 
space. I wrote Netlink client stub to read the audit message as below. But the 
call recvfrom gets blocked indefinite.
Can any one tell me what am I doing wrong?

Regards,
Jayalakshmi

#include <sys/socket.h>
#include <linux/netlink.h>
#include <stdio.h>
#include <malloc.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

int main() 
{
  int fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_AUDIT);

  if (fd < 0) {
    printf("Socket creation failed. try again\n");
  }
  else
  {
        struct sockaddr_nl src_addr;
        struct sockaddr_nl dest_addr;
        struct iovec iov;
        struct msghdr msg;
        struct nlmsghdr *nlh =(struct nlmsghdr *) malloc(NLMSG_SPACE(1024));
        
        memset(nlh, 0, NLMSG_SPACE(1024));
        memset(&iov, 0, sizeof(iov));

        nlh->nlmsg_len   = NLMSG_SPACE(1024);
        nlh->nlmsg_pid   = getpid();
        nlh->nlmsg_flags = 0;

        src_addr.nl_family  = AF_NETLINK;
        src_addr.nl_pid     = getpid();
        src_addr.nl_groups  = 0;

        bind(fd, (struct sockaddr *)&src_addr, sizeof(src_addr));

        iov.iov_base = (void *)nlh;  
        iov.iov_len = nlh->nlmsg_len;  

        msg.msg_name = (void *)&src_addr;
        msg.msg_namelen = sizeof(src_addr);
        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;
  
    recvfrom(fd, &msg,sizeof(msg),0,(struct sockaddr *) 
&dest_addr,sizeof(dest_addr));
    printf("Received message: %s\n", (char *)NLMSG_DATA(nlh));
    close(fd);
}