#include <linux/module.h>
#include <linux/init.h>
#include <linux/in.h>
#include <net/sock.h>

#define SERVER_PORT 5555
static struct socket *udpsocket=NULL;
static DECLARE_COMPLETION( threadcomplete );
static int com_thread_pid;

static int com_thread( void *data )
{
  struct sockaddr_in client;
  struct sockaddr *address;
  unsigned char buffer[100];
  int len;
  struct msghdr msg;
  struct iovec iov;
  mm_segment_t oldfs;

  daemonize( "udpserver" );
  allow_signal( SIGTERM );
  if( udpsocket->sk==NULL ) 
    return 0;
  msg.msg_name = &client;
  msg.msg_namelen = sizeof( struct sockaddr_in );
  msg.msg_control = NULL;
  msg.msg_controllen = 0;
  msg.msg_iov	 = &iov;
  msg.msg_iovlen = 1;
  while( !signal_pending(current) ) {
    iov.iov_base = buffer;
    iov.iov_len  = sizeof(buffer);
    oldfs = get_fs(); 
    set_fs( KERNEL_DS );
    len = sock_recvmsg( udpsocket, &msg, sizeof(buffer), 0 );
    set_fs( oldfs );
    if( len>0 ) {
      address = (struct sockaddr *)&client;
      printk(KERN_INFO "msg \"%s\" from %u.%u.%u.%u\n", buffer,
	     (unsigned char)address->sa_data[2],
	     (unsigned char)address->sa_data[3],
	     (unsigned char)address->sa_data[4],
	     (unsigned char)address->sa_data[5] );
    }
  }
  complete( &threadcomplete );
  return 0;
}

static int __init server_init( void )
{
  struct sockaddr_in server;
  int servererror;

  if( sock_create( PF_INET,SOCK_DGRAM,IPPROTO_UDP,&udpsocket)<0 ) {
    printk( KERN_ERR "server: Error creating udpsocket.\n" );
    return -EIO;
  }
  server.sin_family = AF_INET;
  server.sin_addr.s_addr = INADDR_ANY;
  server.sin_port = htons( (unsigned short)SERVER_PORT );
  servererror = udpsocket->ops->bind( udpsocket,
				      (struct sockaddr *) &server, sizeof( server ) );
  if( servererror ) {
    sock_release( udpsocket );
    return -EIO;
  }

  com_thread_pid=kernel_thread(com_thread,NULL, CLONE_KERNEL );
  if( com_thread_pid < 0 ) {
    sock_release( udpsocket );
    return -EIO;
  }
  return 0;
}

static void __exit server_exit( void )
{
  if( com_thread_pid ) {
    kill_proc( com_thread_pid, SIGTERM, 0 );
    wait_for_completion( &threadcomplete );
  }
  if( udpsocket )
    sock_release( udpsocket );
}

module_init( server_init );
module_exit( server_exit );
MODULE_LICENSE("GPL");