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

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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);

inetutils中tftpd不能独立运行的原因

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