inetutils中tftpd不能独立运行的原因

int

main (int argc, char *argv[])

{

  int index;

  register struct tftphdr *tp;

  int on, n;

  struct sockaddr_storage sin;

  char  *temp;

  int tempint;

  struct stat stbuf;

  user = xstrdup (DEFAULT_USER);

  set_program_name (argv[0]);

  iu_argp_init ("tftpd", default_program_authors);

  argp_parse (&argp, argc, argv, 0, &index, NULL);

  openlog ("tftpd", LOG_PID, LOG_FTP);

  if (index < argc)

    {

      struct dirlist *dirp;

      /* Get list of directory prefixes. Skip relative pathnames. */

      for (dirp = dirs; index < argc && dirp < &dirs[MAXDIRS]; index++)

    {

      if (argv[index][0] == '/')

        {

          dirp->name = argv[index];

          dirp->len = strlen (dirp->name);

          dirp++;

        }

    }

    }

  on = 1;

  if (ioctl (0, FIONBIO, &on) < 0)

    {

      syslog (LOG_ERR, "ioctl(FIONBIO): %m");

      exit (EXIT_FAILURE);

    }

  fstat(0,&stbuf);

  if ((stbuf.st_mode & S_IFMT) == S_IFSOCK)

    syslog (LOG_INFO, "stbuf.st_mode = S_IFSOCK" );

  fromlen = sizeof (from);

  n = recvfrom (0, buf, sizeof (buf), 0, (struct sockaddr *) &from, &fromlen);

temp=inet_ntoa(((struct sockaddr_in*)&from)->sin_addr);

tempint=ntohs (((struct sockaddr_in *)&from)->sin_port);

    syslog (LOG_INFO, "sin_addr = %s,sin_port = %d" ,temp,tempint);

  if (n < 0)

    {

      syslog (LOG_ERR, "recvfrom: %m\n");
  if ((stbuf.st_mode & S_IFMT) == S_IFCHR)

    syslog (LOG_INFO, "stbuf.st_mode = S_IFCHR" );

  fprintf(stderr,"fd = 0 is not a socket\n");

      exit (EXIT_FAILURE);

    }

蓝色部分是自己加的。

如果不加，查看/var/log/syslog只会看到一条信息

Dec 13 08:57:14 ch-Founder-PC tftpd[10451]: recvfrom: Socket operation on non-socket

意思是recvfrom函数的参数0不是一个套接字。

再然后就exit了。如果用ps也看不到tftpd进程。

下面是加了蓝色部分的日志信息

Dec 13 08:57:14 ch-Founder-PC tftpd[10451]: sin_addr = 0.0.0.0,sin_port = 0

Dec 13 08:57:14 ch-Founder-PC tftpd[10451]: recvfrom: Socket operation on non-socket

Dec 13 08:57:14 ch-Founder-PC tftpd[10451]: stbuf.st_mode = S_IFCHR

如果用./inetd -d来启动tftpd服务的话，日志信息是：

Dec 13 08:38:27 ch-Founder-PC tftpd[10221]: stbuf.st_mode = S_IFSOCK

Dec 13 08:38:27 ch-Founder-PC tftpd[10221]: sin_addr = 172.22.24.150,sin_port = 34722

Dec 13 08:38:27 ch-Founder-PC tftpd[10222]: 172.22.24.150 (IPv4): read request for /home/ch/tftpboot/test: success

看来inetd.c中肯定有dup2函数把stdin设置为了一个socket。

果然是这样，相关的代码是：

void

run_service (int ctrl, struct servtab *sep)

{

  struct passwd *pwd;

  struct group *grp = NULL;

  char buf[50];

  if (sep->se_bi)

    {

      (*sep->se_bi->bi_fn) (ctrl, sep);

    }

  else

    {

      if (debug)

    fprintf (stderr, "%d execl %s\n", (int) getpid (), sep->se_server);
      dup2 (ctrl, 0);

      close (ctrl);

      dup2 (0, 1);

      dup2 (0, 2);