servaccept.c

ARM9-2410教学实验系统下Linux下minigui程序

/*
** $Id: servaccept.c,v 1.5 2003/09/04 06:02:53 weiym Exp $
** 
** servaccept.c: accept connection from clients.
** 
** Copyright (C) 2003 Feynman Software
** Copyright (C) 2000 ~ 2002 Wei Yongming.
**
** Current maintainer: Wei Yongming.
**
** Create date: 2000/12/19
**
** NOTE: The idea comes from sample code in APUE.
*/

/*
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/*
** TODO:
*/

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <stddef.h>
#include <time.h>
#include <unistd.h>
#include "ourhdr.h"

#define    STALE    30    /* client's name can't be older than this (sec) */

/* Wait for a client connection to arrive, and accept it.
 * We also obtain the client's pid from the pathname
 * that it must bind before calling us. */

/* returns new fd if all OK, < 0 on error */
int serv_accept (int listenfd, pid_t *pidptr, uid_t *uidptr)
{
    int                clifd, len;
    time_t             staletime;
    struct sockaddr_un unix_addr;
    struct stat        statbuf;
    const char*        pid_str;

    len = sizeof (unix_addr);
    if ( (clifd = accept (listenfd, (struct sockaddr *) &unix_addr, &len)) < 0)
        return (-1);        /* often errno=EINTR, if signal caught */

    /* obtain the client's uid from its calling address */
    len -= /* th sizeof(unix_addr.sun_len) - */ sizeof(unix_addr.sun_family);
                    /* len of pathname */
    unix_addr.sun_path[len] = 0;            /* null terminate */
    if (stat(unix_addr.sun_path, &statbuf) < 0)
        return(-2);
#ifdef    S_ISSOCK    /* not defined for SVR4 */
    if (S_ISSOCK(statbuf.st_mode) == 0)
        return(-3);        /* not a socket */
#endif
    if ((statbuf.st_mode & (S_IRWXG | S_IRWXO)) ||
        (statbuf.st_mode & S_IRWXU) != S_IRWXU)
          return(-4);    /* is not rwx------ */

    staletime = time(NULL) - STALE;
    if (statbuf.st_atime < staletime ||
        statbuf.st_ctime < staletime ||
        statbuf.st_mtime < staletime)
          return(-5);    /* i-node is too old */

    if (uidptr != NULL)
        *uidptr = statbuf.st_uid;    /* return uid of caller */

    /* get pid of client from sun_path */
    pid_str = strrchr (unix_addr.sun_path, '/');
    pid_str++;

    *pidptr = atoi (pid_str);
    
    unlink (unix_addr.sun_path);        /* we're done with pathname now */
    return (clifd);
}