263.htm

unix高级编程原吗

    hostaddr.sin_port = servp->s_port; <br>
  else if (atoi(pargs.service_name) > 0) <br>
    hostaddr.sin_port = htons(atoi(pargs.service_name)); <br>
  else { <br>
    printf("%s: invalid/unknown service name or port number\r\n", <br>
           pargs.service_name); <br>

    exit(1); <br>
  } <br>
} <br>
  <br>
  <br>
  <br>
/**************************************************************************** <br>
  function:      daemonize <br>
  description:   detach the server process from the current context, <br>
                 creating a pristine, predictable environment in which it <br>
                 will execute. <br>
  arguments: <br>
    servfd       file descriptor in use by server. <br>
  <br>
  return value:  none. <br>
  calls:         none. <br>
  globals:       none. <br>
 ****************************************************************************/ <br>
  <br>
void daemonize (servfd) <br>
int servfd; <br>
{ <br>
{ <br>
  int childpid, fd, fdtablesize; <br>
  <br>
  /* ignore terminal I/O, stop signals */ <br>
  signal(SIGTTOU,SIG_IGN); <br>
  signal(SIGTTIN,SIG_IGN); <br>
  signal(SIGTSTP,SIG_IGN); <br>
  <br>
  /* fork to put us in the background (whether or not the user <br>
     specified '&' on the command line */ <br>
  <br>
  if ((childpid = fork()) < 0) { <br>
    fputs("failed to fork first child\r\n",stderr); <br>
    exit(1); <br>
  } <br>
  else if (childpid > 0) <br>
    exit(0);    /* terminate parent, continue in child */ <br>
  <br>
  /* dissociate from process group */ <br>
  if (setpgrp(0,getpid()) < 0) { <br>
    fputs("failed to become process group leader\r\n",stderr); <br>
    exit(1); <br>
  } <br>
  } <br>
  <br>
  /* lose controlling terminal */ <br>
  if ((fd = open("/dev/tty",O_RDWR)) >= 0) { <br>
    ioctl(fd,TIOCNOTTY,NULL); <br>
    close(fd); <br>
  } <br>
  <br>
  /* close any open file descriptors */ <br>
  for (fd = 0, fdtablesize = getdtablesize();  fd < fdtablesize;  fd++) <br>
    if (fd != servfd) <br>
      close(fd); <br>
  <br>
  /* set working directory to / to allow filesystems to be unmounted */ <br>
  chdir("/"); <br>
  <br>
  /* clear the inherited umask */ <br>
  umask(0); <br>
  <br>
  /* setup zombie prevention */ <br>
  signal(SIGCLD,reap_status); <br>
  <br>
} <br>
} <br>
  <br>
  <br>
  <br>
/**************************************************************************** <br>
  function:      do_proxy <br>
  description:   does the actual work of virtually connecting a client to <br>
                 the telnet service on the isolated host. <br>
  arguments: <br>
    usersockfd   socket to which the client is connected. <br>
  <br>
  return value:  none. <br>
  calls:         none. <br>
  globals:       reads hostaddr. <br>
 ****************************************************************************/ <br>
  <br>
void do_proxy (usersockfd) <br>
int usersockfd; <br>
{ <br>
  int isosockfd; <br>
  fd_set rdfdset; <br>
  int connstat; <br>
  int iolen; <br>
  int iolen; <br>
  char buf [2048]; <br>
  <br>
  /* open a socket to connect to the isolated host */ <br>
  if ((isosockfd = socket(AF_INET,SOCK_STREAM,0)) < 0) <br>
    errorout("failed to create socket to host"); <br>
  <br>
  /* attempt a connection */ <br>
  connstat = connect(isosockfd, <br>
                     (struct sockaddr *) &hostaddr, <br>
                     sizeof(hostaddr)); <br>
  switch (connstat) { <br>
    case 0: <br>
      break; <br>
    case ETIMEDOUT: <br>
    case ECONNREFUSED: <br>
    case ENETUNREACH: <br>
      strcpy(buf,sys_errlist[errno]); <br>
      strcat(buf,"\r\n"); <br>
      write(usersockfd,buf,strlen(buf)); <br>
      close(usersockfd); <br>
      exit(1);  /* die peacefully if we can't establish a connection */ <br>
      break; <br>
      break; <br>
    default: <br>
      errorout("failed to connect to host"); <br>
  } <br>
  <br>
  <br>
  /* now we're connected, serve fall into the data echo loop */ <br>
  while (1) { <br>
    /* Select for readability on either of our two sockets */ <br>
    FD_ZERO(&rdfdset); <br>
    FD_SET(usersockfd,&rdfdset); <br>
    FD_SET(isosockfd,&rdfdset); <br>
    if (select(FD_SETSIZE,&rdfdset,NULL,NULL,NULL) < 0) <br>
      errorout("select failed"); <br>
  <br>
    /* is the client sending data? */ <br>
    if (FD_ISSET(usersockfd,&rdfdset)) { <br>
      if ((iolen = read(usersockfd,buf,sizeof(buf))) <= 0) <br>
        break;   /* zero length means the client disconnected */ <br>
  <br>
      write(isosockfd,buf,iolen);   /* copy to host -- blocking semantics */ <br>
    } <br>
  <br>
  <br>
    /* is the host sending data? */ <br>
    if (FD_ISSET(isosockfd,&rdfdset)) { <br>
      if ((iolen = read(isosockfd,buf,sizeof(buf))) <= 0) <br>
        break;   /* zero length means the host disconnected */ <br>
  <br>
      write(usersockfd,buf,iolen);  /* copy to client -- blocking semantics */ <br>
    } <br>
  } <br>
  <br>
  /* we're done with the sockets */ <br>
  close(isosockfd); <br>
  close(usersockfd); <br>
} <br>
  <br>
  <br>
  <br>
/**************************************************************************** <br>
  function:      errorout <br>
  description:   displays an error message on the console and kills the <br>
                 current process. <br>
  arguments: <br>
    msg          message to be displayed. <br>

  <br>
  return value:  none -- does not return. <br>
  calls:         none. <br>
  globals:       none. <br>
 ****************************************************************************/ <br>
  <br>
void errorout (msg) <br>
char *msg; <br>
{ <br>
  FILE *console; <br>
  <br>
  console = fopen("/dev/console","a"); <br>
  fprintf(console,"proxyd: %s\r\n",msg); <br>
  fclose(console); <br>
  exit(1); <br>
} <br>
  <br>
  <br>
  <br>
/**************************************************************************** <br>
  function:      reap_status <br>
  description:   handle a SIGCLD signal by reaping the exit status of the <br>

                 perished child, and discarding it. <br>
  arguments:     none. <br>
  return value:  none. <br>
  calls:         none. <br>
  globals:       none. <br>
 ****************************************************************************/ <br>
  <br>
void reap_status () <br>
{ <br>
  int pid; <br>
  union wait status; <br>
  <br>
  while ((pid = wait3(&status,WNOHANG,NULL)) > 0) <br>
    ;  /* loop while there are more dead children */ <br>
} <br>
  <br>
  <br>
-- <br>
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