retry.c File Reference

Retry timers. More...

#include <stddef.h>
#include <ipxe/timer.h>
#include <ipxe/list.h>
#include <ipxe/process.h>
#include <ipxe/init.h>
#include <ipxe/retry.h>

Go to the source code of this file.

Macros
#define	MIN_TIMEOUT   7

Functions
	FILE_LICENCE (GPL2_OR_LATER_OR_UBDL)
static	LIST_HEAD (timers)
	List of running timers. More...
void	start_timer_fixed (struct retry_timer *timer, unsigned long timeout)
	Start timer with a specified timeout. More...
void	start_timer (struct retry_timer *timer)
	Start timer. More...
void	stop_timer (struct retry_timer *timer)
	Stop timer. More...
static void	timer_expired (struct retry_timer *timer)
	Handle expired timer. More...
void	retry_poll (void)
	Poll the retry timer list. More...
static void	retry_step (struct process *process __unused)
	Single-step the retry timer list. More...
	PERMANENT_PROCESS (retry_process, retry_step)
	Retry timer process. More...

Detailed Description

Retry timers.

A retry timer is a binary exponential backoff timer. It can be used to build automatic retransmission into network protocols.

This implementation of the timer is designed to satisfy RFC 2988 and therefore be usable as a TCP retransmission timer.

Definition in file retry.c.

Macro Definition Documentation

MIN_TIMEOUT

#define MIN_TIMEOUT   7

Definition at line 49 of file retry.c.

Function Documentation

FILE_LICENCE()

FILE_LICENCE

(

GPL2_OR_LATER_OR_UBDL

)

LIST_HEAD()

static LIST_HEAD ( timers  )

static

List of running timers.

start_timer_fixed()

void start_timer_fixed	(	struct retry_timer *	timer,
		unsigned long	timeout
	)

Start timer with a specified timeout.

Parameters

timer	Retry timer
timeout	Timeout, in ticks

This starts the timer running with the specified timeout value. If stop_timer() is not called before the timer expires, the timer will be stopped and the timer's callback function will be called.

Definition at line 64 of file retry.c.

                                                                            {

        /* Add to list of running timers (if applicable) */
        if ( ! timer->running ) {
                list_add ( &timer->list, &timers );
                ref_get ( timer->refcnt );
                timer->running = 1;
        }

        /* Record start time */
        timer->start = currticks();

        /* Record timeout */
        timer->timeout = timeout;

        DBGC2 ( timer, "Timer %p started at time %ld (expires at %ld)\n",
                timer, timer->start, ( timer->start + timer->timeout ) );
}

References currticks(), DBGC2, list_add, ref_get, and timeout().

Referenced by dhcp_defer(), eapol_eap_rx(), eapol_expired(), efi_watchdog_expired(), exanic_expired(), exanic_open(), fc_link_err(), fc_link_expired(), fc_xchg_rx(), fc_xchg_tx(), fcoe_expired(), fragment_reassemble(), http_transfer_complete(), ipair_rx_pair_error(), iphone_expired(), ipv6conf_expired(), netdev_link_block(), peerblk_open(), peerblk_raw_open(), peerblk_raw_rx(), peerblk_retrieval_open(), peerblk_retrieval_rx(), peerdisc_expired(), pinger_expired(), pool_add(), sandev_command(), slam_mc_socket_deliver(), slam_open(), start_timer(), start_timer_nodelay(), tcp_keepalive_expired(), tcp_rx(), tcp_rx_ack(), xcm_keepalive(), xcm_reopen(), xsigo_discover(), xsigo_ib_open(), and xsigo_xcm_complete().

start_timer()

void start_timer

(

struct retry_timer *

timer

)

Start timer.

Parameters

timer

Retry timer

This starts the timer running with the current timeout value (rounded up to the minimum timeout value). If stop_timer() is not called before the timer expires, the timer will be stopped and the timer's callback function will be called.

Definition at line 93 of file retry.c.

                                               {
        unsigned long timeout = timer->timeout;
        unsigned long min;

        /* Calculate minimum timeout */
        min = ( timer->min ? timer->min : DEFAULT_MIN_TIMEOUT );
        if ( min < MIN_TIMEOUT )
                min = MIN_TIMEOUT;

        /* Ensure timeout is at least the minimum */
        if ( timeout < min )
                timeout = min;

        /* Start timer with this timeout */
        start_timer_fixed ( timer, timeout );
}

References DEFAULT_MIN_TIMEOUT, min, MIN_TIMEOUT, start_timer_fixed(), and timeout().

Referenced by aoecmd_tx(), dhcp_tx(), dhcpv6_timer_expired(), dns_send_packet(), ib_mi_timer_expired(), ipv6conf_expired(), neighbour_expired(), ntp_expired(), slam_master_timer_expired(), slam_slave_timer_expired(), slam_socket_deliver(), tcp_xmit_sack(), tftp_send_packet(), xcm_close(), and xcm_reopen().

stop_timer()

void stop_timer

(

struct retry_timer *

timer

)

Stop timer.

Parameters

timer

Retry timer

This stops the timer and updates the timer's timeout value.

Definition at line 117 of file retry.c.

                                              {
        unsigned long old_timeout = timer->timeout;
        unsigned long now = currticks();
        unsigned long runtime;

        /* If timer was already stopped, do nothing */
        if ( ! timer->running )
                return;

        list_del ( &timer->list );
        runtime = ( now - timer->start );
        timer->running = 0;
        DBGC2 ( timer, "Timer %p stopped at time %ld (ran for %ld)\n",
                timer, now, runtime );

        /* Update timer.  Variables are:
         *
         *   r = round-trip time estimate (i.e. runtime)
         *   t = timeout value (i.e. timer->timeout)
         *   s = smoothed round-trip time
         *
         * By choice, we set t = 4s, i.e. allow for four times the
         * normal round-trip time to pass before retransmitting.
         *
         * We want to smooth according to s := ( 7 s + r ) / 8
         *
         * Since we don't actually store s, this reduces to
         * t := ( 7 t / 8 ) + ( r / 2 )
         *
         */
        if ( timer->count ) {
                timer->count--;
        } else {
                timer->timeout -= ( timer->timeout >> 3 );
                timer->timeout += ( runtime >> 1 );
                if ( timer->timeout != old_timeout ) {
                        DBGC ( timer, "Timer %p timeout updated to %ld\n",
                               timer, timer->timeout );
                }
        }

        ref_put ( timer->refcnt );
}

References currticks(), DBGC, DBGC2, list_del, and ref_put.

Referenced by aoecmd_close(), dhcp_finished(), dhcp_set_state(), dhcpv6_finished(), dns_done(), dns_xfer_deliver(), eapol_eap_rx(), eapol_notify(), efi_watchdog_stop(), exanic_close(), fc_link_stop(), fc_link_up(), fc_xchg_close(), fcoe_close(), fcoe_expired(), fcoe_reset(), fragment_reassemble(), http_close(), ib_destroy_madx(), ipair_close(), iphone_close(), ipv6conf_done(), ipv6conf_rx_router_advertisement(), neighbour_destroy(), neighbour_discovered(), netdev_close(), netdev_link_err(), netdev_link_unblock(), ntp_close(), peerblk_reset(), peerblk_retrieval_close(), peerdisc_destroy(), pinger_close(), pool_del(), sandev_command_close(), slam_finished(), slam_mc_socket_deliver(), slam_socket_deliver(), tcp_close(), tcp_rx(), tcp_rx_ack(), tftp_done(), tftp_send_packet(), xcm_close(), xcm_destroy(), xcm_reopen(), xsigo_ib_notify(), and xsigo_ib_remove().

timer_expired()

static void timer_expired ( struct retry_timer *  timer )

static

Handle expired timer.

Parameters

timer

Retry timer

Definition at line 166 of file retry.c.

                                                        {
        struct refcnt *refcnt = timer->refcnt;
        unsigned long max = ( timer->max ? timer->max : DEFAULT_MAX_TIMEOUT );
        int fail;

        /* Stop timer without performing RTT calculations */
        DBGC2 ( timer, "Timer %p stopped at time %ld on expiry\n",
                timer, currticks() );
        assert ( timer->running );
        list_del ( &timer->list );
        timer->running = 0;
        timer->count++;

        /* Back off the timeout value */
        timer->timeout <<= 1;
        if ( ( fail = ( timer->timeout > max ) ) )
                timer->timeout = max;
        DBGC ( timer, "Timer %p timeout backed off to %ld\n",
               timer, timer->timeout );

        /* Call expiry callback */
        timer->expired ( timer, fail );
        /* If refcnt is NULL, then timer may already have been freed */

        ref_put ( refcnt );
}

References assert(), currticks(), DBGC, DBGC2, DEFAULT_MAX_TIMEOUT, list_del, max, and ref_put.

Referenced by retry_poll().

retry_poll()

void retry_poll

(

void

)

Poll the retry timer list.

Definition at line 197 of file retry.c.

                         {
        struct retry_timer *timer;
        unsigned long now = currticks();
        unsigned long used;

        /* Process at most one timer expiry.  We cannot process
         * multiple expiries in one pass, because one timer expiring
         * may end up triggering another timer's deletion from the
         * list.
         */
        list_for_each_entry ( timer, &timers, list ) {
                used = ( now - timer->start );
                if ( used >= timer->timeout ) {
                        timer_expired ( timer );
                        break;
                }
        }
}

References currticks(), retry_timer::list, list_for_each_entry, timer, and timer_expired().

Referenced by eoib_poll(), ipoib_poll(), and retry_step().

retry_step()

static void retry_step ( struct process *process  __unused )

static

Single-step the retry timer list.

Parameters

process

Retry timer process

Definition at line 221 of file retry.c.

                                                            {
        retry_poll();
}

References retry_poll().

PERMANENT_PROCESS()

PERMANENT_PROCESS	(	retry_process	,
		retry_step
	)

Retry timer process.