dns.c

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#endif /* DNS_INCLUDED */

    return (NU_NULL);
} /* DNS_Find_Host_By_Name */

/******************************************************************************/
/* FUNCTION                                                                   */
/*                                                                            */
/*   DNS_Find_Host_By_Addr                                                    */
/*                                                                            */
/* DESCRIPTION                                                                */
/*                                                                            */
/*    This function searches the "hosts" file for a host with a matching addr.*/
/*    If the host is not found DNS is used to resolve the host address        */
/*    if possible.                                                            */
/*                                                                            */
/* AUTHOR                                                                     */
/*                                                                            */
/*    Glen Johnson,      Accelerated Technology Inc.                          */
/*                                                                            */
/* CALLED BY                                                                  */
/*                                                                            */
/*    NU_Get_Host_By_Addr       Retrieve host information based on an address.*/
/*                                                                            */
/* CALLS                                                                      */
/*                                                                            */
/*    DNS_Add_Host              Add a host to the "hosts file"                */
/*    DNS_Resolve               Resolve a host name or address                */
/*    NU_Retrieve_Clock         Get the current clock tick.                   */
/*                                                                            */
/* INPUTS                                                                     */
/*                                                                            */
/*    addr                      The address of the host to find.              */
/*                                                                            */
/* OUTPUTS                                                                    */
/*                                                                            */
/*    NULL is returned if the host is not found, otherwise a host pointer.    */
/*                                                                            */
/* HISTORY                                                                    */
/*                                                                            */
/*    NAME                DATE        REMARKS                                 */
/*                                                                            */
/*    Glen Johnson      06/17/97    Created initial version for NET 3.1       */
/*                                                                            */
/******************************************************************************/
DNS_HOST *DNS_Find_Host_By_Addr(CHAR *addr)
{
    DNS_HOST        *host;
    CHAR            name[255];
    UNSIGNED        ttl;


    /* Search for a matching host. */
    for ( host = DNS_Hosts.dns_head; host ; host = host->dns_next)
    {
        /* Is this one we're looking for. */
        if (*(uint32 *)host->dns_ipaddr == *(uint32 *)addr)
        {
            /* We found a match.  If this is a permanent entry, return it. */
            if (!host->dns_ttl)
                return host;
            else
            {
                /* If the ttl has not expired return the host.  Else this entry
                   should be updated, so break. */
                if (INT32_CMP(host->dns_ttl, NU_Retrieve_Clock()) > 0)
                    return host;
                else
                    break;
            }
        }
    }

#if DNS_INCLUDED

    /* If the host was not found in the local cache or it had expired, then try
       to resolve it through DNS. */
    if (DNS_Resolve(name, addr, &ttl, DNS_TYPE_PTR) == NU_SUCCESS)
        return (DNS_Add_Host(name, addr, ttl));

#endif /* DNS_INCLUDED */

    return (NU_NULL);
} /* DNS_Find_Host_By_Addr */

#if DNS_INCLUDED
/******************************************************************************/
/* FUNCTION                                                                   */
/*                                                                            */
/*   DNS_Resolve                                                              */
/*                                                                            */
/* DESCRIPTION                                                                */
/*                                                                            */
/*    This routine will handle domain based name lookup.  It can hadle both   */
/*    queries for names and quiries for IP addresses.  Either the name and ttl*/
/*    are returned or an IP address and ttl are returned.                     */
/*                                                                            */
/* AUTHOR                                                                     */
/*                                                                            */
/*    Glen Johnson,      Accelerated Technology Inc.                          */
/*                                                                            */
/* CALLED BY                                                                  */
/*                                                                            */
/*    DNS_Find_Host_By_Name             Given a name find a host.             */
/*    DNS_Find_Host_By_Addr             Given an address find a host.         */
/*                                                                            */
/* CALLS                                                                      */
/*                                                                            */
/*    NU_Deallocate_Memory      Deallocate a block of memory.                 */
/*    DNS_Build_Query           Create a DNS query packet.                    */
/*    DNS_Query                 Send the DNS query.                           */
/*    DNS_Extract_Data          Extract an IP address or name from the        */
/*                                response.                                   */
/*                                                                            */
/* INPUTS                                                                     */
/*                                                                            */
/*    name                      A host name.                                  */
/*    ip_addr                   The host IP address, filled in by this        */
/*                                function.                                   */
/*    ttl                       Time To Live, length of time the host info.   */
/*                                can be cached.  Filled in here.             */
/*    type                      Type of query, name or address.               */
/*                                                                            */
/* OUTPUTS                                                                    */
/*                                                                            */
/*    NU_SUCCESS                Indicates successful operation.               */
/*    a negative value            Indicates failure.                          */
/*                                                                            */
/* HISTORY                                                                    */
/*                                                                            */
/*    NAME                DATE        REMARKS                                 */
/*                                                                            */
/*    Glen Johnson      06/16/97    Created initial version for NET 3.1       */
/*                                                                            */
/******************************************************************************/
STATUS DNS_Resolve(CHAR *name, CHAR *ip_addr, UNSIGNED *ttl, INT type)
{
    STATUS                  stat;
    CHAR                    *buffer;
    int16                   q_size;


    /* Is there a DNS Server. */
    if ( !(*(uint32 *)DNS_Server) )
    {
        /* SGJ:  Make this a more meanigful return value. */
        return (-1);
    }

    /* Build the DNS query. */
    switch (type)
    {
        case DNS_TYPE_A :

            if ((q_size = DNS_Build_Query(name, (VOID **)&buffer, type)) < 0)
                return -1;

            break;

        case DNS_TYPE_PTR :

            if ((q_size = DNS_Build_Query(ip_addr, (VOID **)&buffer, type)) < 0)
                return -1;

            break;

        default:

            return -1;
    }

    /* Query the DNS server.  Upon returning the buffer will contain the
       response to our query. */
    if (DNS_Query(buffer, q_size) < 0)
    {
        NU_Deallocate_Memory(buffer);

        return -1;
    }

    /* Now process the response. */
    switch (type)
    {
        case DNS_TYPE_A :

            stat = DNS_Extract_Data ((DNS_PKT_HEADER *)buffer, ip_addr, ttl,
                                      type);
            break;

        case DNS_TYPE_PTR :

            stat = DNS_Extract_Data ((DNS_PKT_HEADER *)buffer, name, ttl, type);
            break;

        default:

            return -1;
    }

    /* Deallocate the memory buffer. */
    NU_Deallocate_Memory(buffer);

    if (stat != NU_SUCCESS)
        return (NU_DNS_ERROR);
    else
        return (stat);

}  /* DNS_Resolve */

/******************************************************************************/
/* FUNCTION                                                                   */
/*                                                                            */
/*   DNS_Build_Query                                                          */
/*                                                                            */
/* DESCRIPTION                                                                */
/*                                                                            */
/*    This function will build a DNS query packet.                            */
/*                                                                            */
/* AUTHOR                                                                     */
/*                                                                            */
/*    Glen Johnson,      Accelerated Technology Inc.                          */
/*                                                                            */
/* CALLED BY                                                                  */
/*                                                                            */
/*    DNS_Resolve            Resolve a host IP address.                       */
/*                                                                            */
/* CALLS                                                                      */
/*                                                                            */
/*    NU_Allocate_Memory        Allocate memory.                              */
/*    DNS_Pack_Domain_Name      Convert a host name into format expected by   */
/*                                a DNS server.                               */
/*    DNS_Addr_To_String        Convert an IP address into a character string.*/
/*    intswap                   Swap the bytes in an integer.                 */
/*                                                                            */
/* INPUTS                                                                     */
/*                                                                            */
/*    name                      A host name.                                  */
/*    buffer                    A pointer to a buffer pointer.                */
/*    type                      A query type.                                 */
/*                                                                            */
/* OUTPUTS                                                                    */
/*                                                                            */
/*    > 0                       The size of the packed name.                  */