rfscomm.c

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/* rfscomm.c - rfscomm */

#include <xinu.h>

/*------------------------------------------------------------------------
 * rfscomm  -  Handle communication with RFS server (send request and
 *      receive a reply, including sequencing and retries)
 *------------------------------------------------------------------------
 */
int32   rfscomm (
     struct rf_msg_hdr *msg,    /* Message to send      */
     int32  mlen,           /* Message length       */
     struct rf_msg_hdr *reply,  /* Buffer for reply     */
     int32  rlen            /* Size of reply buffer     */
    )
{
    int32   i;          /* Counts retries       */
    int32   retval;         /* Return value         */
    int32   seq;            /* Sequence for this exchange   */
    int16   rtype;          /* Reply type in host byte order*/
    int32   slot;           /* UDP slot         */

    /* For the first time after reboot, register the server port */

    if ( ! Rf_data.rf_registered ) {
        if ( (slot = udp_register(Rf_data.rf_ser_ip,
                Rf_data.rf_ser_port,
                Rf_data.rf_loc_port)) == SYSERR) {
            return SYSERR;
        }
        Rf_data.rf_udp_slot = slot;
        Rf_data.rf_registered = TRUE;
    }

    /* Assign message next sequence number */

    seq = Rf_data.rf_seq++;
    msg->rf_seq = htonl(seq);

    /* Repeat RF_RETRIES times: send message and receive reply */

    for (i=0; i<RF_RETRIES; i++) {

        /* Send a copy of the message */

        retval = udp_send(Rf_data.rf_udp_slot, (char *)msg,
            mlen);
        if (retval == SYSERR) {
            kprintf("Cannot send to remote file server\n");
            return SYSERR;
        }

        /* Receive a reply */

        retval = udp_recv(Rf_data.rf_udp_slot, (char *)reply,
            rlen, RF_TIMEOUT);

        if (retval == TIMEOUT) {
            continue;
        } else if (retval == SYSERR) {
            kprintf("Error reading remote file reply\n");
            return SYSERR;
        }

        /* Verify that sequence in reply matches request */

        if (ntohl(reply->rf_seq) != seq) {
            continue;
        }

        /* Verify the type in the reply matches the request */

        rtype = ntohs(reply->rf_type);
        if (rtype != ( ntohs(msg->rf_type) | RF_MSG_RESPONSE) ) {
            continue;
        }

        return retval;      /* Return length to caller */
    }

    /* Retries exhausted without success */

    kprintf("Timeout on exchange with remote file server\n");
    return TIMEOUT;
}