dns_relay_atmos.c

DNS 的实现代码

 *
 * Handler for MSG_N_TELL.
 *
 * Arguments:
 *   msg       Pointer to ATMOS TELL message containing command to handle.
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
static void dns_relay_handle_tell( ATMOS_MESSAGE *msg )
{
    static char last_cmd[80];
    MSG_D_TELL( tell, msg );
    char *cmd = tell->cmd;
    int i;

    foreground_output_begin();

    if ( '\0' != *cmd )
    {
        BOOL found = FALSE;

        if (0 == strcmp(".", cmd))
            cmd = last_cmd;
        else
            strncpy( last_cmd, cmd, sizeof(last_cmd) );

        for (i = 0; i < commands.count; i++)
        {
            size_t len = strlen( commands.name[i] );

            if (strncmp( cmd, commands.name[i], len ) == 0)
            {
                (*commands.handler[i]) (cmd + len, stdout );
                found = TRUE;
                break;
            }
        }

        if ( !found )
            printf( "%C: Unknown command '%s', try 'help'.\n", cmd );
    }

    foreground_output_end();
    sendreply(msg);
}

/*****************************************************************************
 *
 * dns_relay_add_command:
 *
 * Install a handler for a TELL command.
 *
 * Arguments:
 *   name      Name of command
 *   handler   Command handler function
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
static void dns_relay_add_command( const char *name, const char *help_text, 
                                   void (*handler) (char *, FILE *) )
{
    if (commands.count >= MAX_COMMANDS)
    {
        kprintf("%C: Failed to install handler for command %s\n\r", name);
    }
    else
    {
        commands.name[commands.count]      = name;
        commands.help_text[commands.count] = help_text;
        commands.handler[commands.count]   = handler;
        commands.count++;
    }
    return;
}

#ifdef AUTO_DISCOVERY_SUPPORTED
/*****************************************************************************
 * dns_relay_auto_command:
 *
 * Toggles auto-discovery of DNS server address via PPP (or otherwise).                      
 *
 * Arguments:
 *   arg       Tail of command string.
 *   fh        FILE* for display output.
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
void dns_relay_auto_command( char *arg, FILE *fh )
{
    UNUSED( arg );
    
    if( !config.automatic_discovery )
    {
        fprintf( fh, "Server address auto-discovery mode activated.\n" );

        if( config.connection_successful )
        {
            fprintf( fh, "Warning: abandoned working server connection.\n");
            config.connection_successful = FALSE;
        }

        /* Reset DNS server address to default */
        os_inet_aton( DNS_DEFAULT_SERVER_ADDR, &config.dns_server_address );
        config.retry_discovery = TRUE;
        config.rediscover_server = TRUE;
    }
    else
    {
        fprintf( fh, "Already in auto-discovery mode.\n" );
    } 

    config.automatic_discovery = TRUE;
    return;
}
#endif /* AUTO_DISCOVERY_SUPPORTED */

/*****************************************************************************
 *
 * dns_relay_config_command:
 *
 * Displays current DNS relay config.
 *
 * Arguments:
 *   arg       Tail of command string.
 *   fh        FILE* for display output.
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
void dns_relay_config_command( char *arg, FILE *fh )
{
    UNUSED( arg );
    UNUSED( fh );

    if( 0 == strcmp( " reset", arg ))
    {
        dns_relay_process_config( TRUE );
    }
    else
    {
        dns_relay_process_config( FALSE );
    }

    return;
}

/*****************************************************************************
 *
 * dns_relay_help_command:
 *
 * Displays quick help about valid commands, or detailed help on the specified
 * commands, or detailed help on all commands.
 *
 * Arguments:
 *   arg       Tail of command string.
 *   fh        FILE* for display output.
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
void dns_relay_help_command( char *arg, FILE *fh )
{
    int count;
    BOOL show_details = FALSE;
    BOOL command_found = FALSE;
    BOOL bad_command = TRUE;

    if ( '\0' != *arg )
    {
        /* Move beyond space between "help" command and argument */
        arg++;

        if (0 == strncmp( arg, "all", 3 ))
        {
            bad_command  = FALSE;
            show_details = TRUE;
        }
        else
        {
            /* Search for help on requested command */
            for ( count=0; count < commands.count; count++ )
            {
                if ( 0 == strncmp( arg, commands.name[count], strlen(commands.name[count])) )
                {
                    /* List details of requested command, if found */
                    fprintf( fh, "DNS relay '%s' command: \n", commands.name[count] );
                    fprintf( fh, " %12s - %s\n", commands.name[count], commands.help_text[count]);
                    command_found = TRUE;
                    break;
                }
            }
        }
    }
    else
    {
        bad_command = FALSE;
    }

    if ( !command_found )
    {
        /* The request command is unknown, or the user wanted to know details
         * of all commands
         */
        if( bad_command ) fprintf( fh, "Unrecognised command. " );
        fprintf( fh, "Valid DNS relay commands are: \n" );
        
        for ( count=0; count < commands.count; count++ )
        {
            if( show_details )
            { 
                /* Show detailed list of available commands */
                fprintf( fh, " %12s - %s\n", commands.name[count], commands.help_text[count]);
            }
            else
            {
                /* Show brief list of available commands */
                fprintf( fh, "%12s", commands.name[count] );
                if (4 == (count % 5)) fprintf( fh, "\n" );
            }
        }
        
        if (0 != (count % 5)) fprintf( fh, "\n" );
    }

    return;
}

/*****************************************************************************
 *
 * dns_relay_retry_command:
 *
 * Alters the number of transmission retries the relay will attempt (UDP
 * only) when trying to contact a DNS server.
 *
 * Arguments:
 *   arg       Tail of command string.
 *   fh        FILE* for display output.
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
void dns_relay_retry_command( char *arg, FILE *fh )
{
    int new_retry_value;

    UNUSED( fh );

    new_retry_value = atoi( arg );
    dns_relay_process_retry( new_retry_value );

    return;
}
        
/*****************************************************************************
 *
 * dns_relay_server_command:
 *
 * Command handler to manually tell the DNS relay which server to contact.
 *
 * Arguments:
 *   arg       Tail of command string.
 *   fh        FILE* for display output.
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
void dns_relay_server_command( char *arg, FILE *fh )
{
    UNUSED( fh );

    arg++; /* move beyond argument space */
    dns_relay_process_server( arg , MANUALLY_CONFIGURED_DNS_SERVER);

    return;
}

/*****************************************************************************
 *
 * dns_relay_status_command:
 *
 * Command handler to show DNS relay activation and connection status. 
 *
 * Arguments:
 *   arg       Tail of command string.
 *   fh        FILE* for display output.
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/

void dns_relay_status_command( char *arg, FILE *fh )
{
    UNUSED( arg );
    UNUSED( fh );

    dns_relay_process_status();

    return;
}

/*****************************************************************************
 *
 * dns_relay_showdb_command:
 *
 * Command handler to tell DNS relay to list the contents of the LAN database
 *
 * Arguments:
 *   arg       Tail of command string.
 *   fh        FILE* for display output.
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
void dns_relay_showdb_command( char *arg, FILE *fh )
{
    UNUSED( fh );
    UNUSED( arg );

    dump_lan_entries();

    return;
}
/*****************************************************************************
 *
 * dns_relay_trace_command:
 *
 * Command handler to set trace flags (and display current settings)
 *
 * Arguments:
 *   arg       Tail of command string.
 *   fh        FILE* for display output.
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
void dns_relay_trace_command( char *arg, FILE *fh )
{
    UNUSED( fh );

    dns_relay_process_trace( arg );

    return;
}

/*****************************************************************************
 *
 * dns_relay_untrace_command:
 *
 * Command handler to clear trace flags (and display current settings)
 *
 * Arguments:
 *   arg       Tail of command string.
 *   fh        FILE* for display output.
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
void dns_relay_untrace_command( char *arg, FILE *fh )
{
    UNUSED( fh );

    dns_relay_process_untrace( arg );

    return;
}

/*****************************************************************************
 *
 * dns_relay_version_command:
 *
 * Command handler to display current software version.
 *
 * Arguments:
 *   arg       Tail of command string.
 *   fh        FILE* for display output.
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
void dns_relay_version_command( char *arg, FILE *fh )
{
    UNUSED( arg );
    UNUSED( fh );
    
    dns_relay_process_version();

    return;
}

/*****************************************************************************
 *
 * dns_relay_bailout
 *
 * Emergency bailout function only to be called if there are no other options. 
 * This function effectively suspends the process, allowing it only to
 * respond to messages. ATMOS version which uses messages.
 *    
 * Arguments:
 *   none
 *
 * Returns:
 *   Nothing
 *
 *****************************************************************************/
void dns_relay_bailout( void )
{
    ATMOS_MESSAGE *m;

    foreground_output_begin();

    while( TRUE )
    {
        m = awaitmessage();

        if( (m->code) == MSG_N_TELL )
        {
            printf("%C: DNS relay has suspended due to critical failure.\n");
        }

        if (!(m->code & MSG_REPLY_BIT))
        {
            sendreply( m );
        }
    }

    /* never reached */
    return;
}