myinetd.cpp

伯克利做的SFTP安全文件传输协议

// myinetd.cpp
// program to start a server the same way inetd does
// copyright SafeTP Development Group, Inc., 2000  Terms of use are as specified in license.txt

#include "sockutil.h"      // listen_socket, etc.
#include "test.h"          // ARGS_MAIN
#include <stdlib.h>        // atoi
#include <stdio.h>         // perror
#include <sys/types.h>     // waitpid (argument macros?)
#include <sys/wait.h>      // waitpid

#define FD_STDIN 0
#define FD_STDOUT 1
#define FD_STDERR 2

int entry(int argc, char *argv[])
{
  if (argc < 3) {
    printf("usage: %s [interface:]port prog-to-run [prog's arguments]\n", argv[0]);
    printf("  (note: must run as root if port < 1024)\n");
    return 0;
  }

  // interpret arguments
  IPAddress interface;
  int port;
  parseAddrAndPort(interface, port, argv[1]);
  char const *progToRun = argv[2];

  // listen for a connection
  SOCKET listener = interface_listen_socket(interface, port);

  // declare socket to carry info outside loop
  SOCKET conn;

  // loop until killed
  for (;;) {
    // reap up to two zombie children on each pass, just to
    // keep the total # of zombies reasonable (around 1-2)
    loopi(2) {
      int status;    // dummy, don't care
      waitpid(-1 /*any child*/, &status, WNOHANG /*nonblocking*/);
        // ignore return; may not be any children to reap, I don't care
    }

    // wait for incoming, and make a new socket for it when it arrives
    fprintf(stderr, "%s: listening for incoming connection at %s...\n",
                    argv[0], formatAddress(interface, port).pcharc());
    conn = accept_socket(listener);
    fprintf(stderr, "%s: received connection %s, starting %s\n",
                    argv[0], sockInfo(conn).pcharc(),
                    progToRun);

    // fork a child to finish up and run the real server
    int forkRet = fork();
    if (forkRet == -1) {
      perror("fork");
    }
    else if (forkRet != 0) {
      // this is the parent, will go back to the top of the loop
    }
    else {
      // this is the child

      // we don't need to have a handle to the listener; the parent
      // still has it and should continue using it
      close(listener);

      // break out of the loop and exec the server
      break;
    }

    // if we're here because of an error, we close because we can't start
    // the server, and don't want whoever connected just hanging around;
    // if we're here on the normal path, the child now has a duplicate
    // of this socket, and so we can close it
    close(conn);
  }


  // this is the child's normal path

  #if 1
    // replace *my* stdin, stdout, stderr with the new connection
    if (dup2(conn, FD_STDIN) < 0 ||
	dup2(conn, FD_STDOUT) < 0 ||
       	//dup2(conn, FD_STDERR) < 0 ||
        false) {
      perror("dup2");
      return 2;
    }
  #else
    // since my current version of sftpd doesn't have the full logging
    // facilities I want, and I know it only uses fd 0 (stdin) as the
    // client connection, I'll just put the conn on FD_STDIN, and let
    // the debugging output just go to the same place as this program's
    if (dup2(conn, FD_STDIN) < 0) {
      perror("dup2");
      return 2;
    }
  #endif


  // having duplicated it now, the original file descriptor is redundant
  close(conn);

  // exec the other program, with the remaining arguments to this program
  execv(argv[2], argv+2);

  // if execv returns, an error occurred
  perror("execv");
  return 4;
}


ARGS_MAIN