#include <stdio.h>
#include <memory.h>
#include <malloc.h>
#include <unistd.h>
#include <bits/sockaddr.h>
#include <linux/netlink.h>
#include <sys/socket.h>

/* Sollte in .../include/linux/netlink.h stehen */
#define NETLINK_TEST 25

#define MY_NL_COMMAND 0x11
#define MAX_PAYLOAD 1024

int main( int argc, char **argv )
{
  struct sockaddr_nl src_addr, dst_addr;
  struct nlmsghdr *nlh = NULL;
  struct msghdr msg;
  struct iovec iov;
  int sock_fd;

  /* Eigenen Endpoint erstellen */
  sock_fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_TEST);
  memset(&src_addr, 0, sizeof(src_addr));
  src_addr.nl_family = AF_NETLINK;
  src_addr.nl_pid = getpid();
  src_addr.nl_groups = 0; /* kein multicast */
  bind(sock_fd, (struct sockaddr*)&src_addr, sizeof(src_addr));

  /* Zieladresse vorbereiten */
  memset(&dst_addr, 0, sizeof(dst_addr));
  dst_addr.nl_family = AF_NETLINK;
  dst_addr.nl_pid = 0; /* 0 -> kernel */
  dst_addr.nl_groups = 0; /* kein multicast */

  /* Netlink-Header erstellen */
  nlh = (struct nlmsghdr *)calloc(1, NLMSG_SPACE(MAX_PAYLOAD));
  memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD));
  nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD);
  nlh->nlmsg_pid = getpid();
  printf("Absender: %d\n", nlh->nlmsg_pid);
  nlh->nlmsg_flags = NLM_F_REQUEST|NLM_F_ECHO;
  nlh->nlmsg_type = MY_NL_COMMAND;

  /* Daten einpacken */
  strcpy(NLMSG_DATA(nlh), "Hello World");

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

  memset(&msg,0,sizeof(msg));
  msg.msg_name = (void *)&dst_addr;
  msg.msg_namelen = sizeof(dst_addr);
  msg.msg_iov = &iov;
  msg.msg_iovlen = 1; /* Anzahl */
  sendmsg(sock_fd, &msg, 0);

  /* Read message from kernel */
  printf("Warte auf Antwort...\n");
  recvmsg(sock_fd, &msg, 0);
  printf("Antwort:\n\tflags %d\n\ttype %d\n\t%s\n",
    nlh->nlmsg_flags,
    nlh->nlmsg_type,
    (char *)NLMSG_DATA(nlh));
  close(sock_fd);
  return 0;
}