servaccept.c

unix环境高级编程的源代码

#include    <sys/types.h>
#include    <sys/socket.h>
#include    <sys/stat.h>
#include    <sys/un.h>
#include    <stddef.h>
#include    <time.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 user ID from the pathname
 * that it must bind before calling us. */

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

    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 */
#ifdef    SCM_RIGHTS    /* 4.3BSD Reno and later */
    len -= sizeof(unix_addr.sun_len) - sizeof(unix_addr.sun_family);
#else                /* vanilla 4.3BSD */
    len -= sizeof(unix_addr.sun_family);    /* len of pathname */
#endif
    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 */

    unlink(unix_addr.sun_path);        /* we're done with pathname now */

    return(clifd);
}