childdial.c

unix环境高级编程的源代码

#include    "calld.h"

/* The child does the actual dialing and sends the fd back to
 * the client.  This function can't return to caller, must exit.
 * If successful, exit(0), else exit(1).
 * The child uses the following global variables, which are just
 * in the copy of the data space from the parent:
 *        cliptr->fd (to send DEBUG() output and fd back to client),
 *        cliptr->Debug (for all DEBUG() output), childptr->parity,
 *        systems, devices, dialers. */

void
child_dial(Client *cliptr)
{
    int        fd, n;

    Debug = cliptr->Debug;
    DEBUG("child, pid %d", getpid());

    if (strcmp(devices.dialer, "direct") == 0) { /* direct tty line */
        fd = tty_open(systems.class, devices.line, cliptr->parity, 0);
        if (fd < 0)
            goto die;
    } else {                    /* else assume dialing is needed */
        if (dial_find(&dialers, &devices) < 0)
            goto die;
        fd = tty_open(systems.class, devices.line, cliptr->parity, 1);
        if (fd < 0)
            goto die;
        if (tty_dial(fd, systems.phone, dialers.dialer,
                                dialers.sub, dialers.expsend) < 0)
            goto die;
    }

    DEBUG("done");
            /* send the open descriptor to client */
    if (send_fd(cliptr->fd, fd) < 0)
        log_sys("send_fd error");
    exit(0);    /* parent will see this */

die:
    /* The child can't call send_err() as that would send the final
       2-byte protocol to the client.  We just send our error message
       back to the client.  If the parent finally gives up, it'll
       call send_err(). */

    n = strlen(errmsg);
    if (writen(cliptr->fd, errmsg, n) != n)    /* send error to client */
        log_sys("send_err error");
    exit(1);    /* parent will see this, release lock, and try again */
}