[retry] Added configurable timeouts to retry timer

New min_timeout and max_timeout fields in struct retry_timer allow
users of this timer to set their own desired minimum and maximum
timeouts, without being constrained to a single global minimum and
maximum. Users of the timer can still elect to use the default global
values by leaving the min_timeout and max_timeout fields as 0.

src/include/gpxe/dhcp.h

 /** Maximum time that we will wait for ProxyDHCP responses */
 #define PROXYDHCP_WAIT_TIME ( TICKS_PER_SEC * 1 )
 
+/** Timeouts for sending DHCP packets */
+#define DHCP_MIN_TIMEOUT ( 1 * TICKS_PER_SEC )
+#define DHCP_MAX_TIMEOUT ( 10 * TICKS_PER_SEC )
+
 /** Settings block name used for DHCP responses */
 #define DHCP_SETTINGS_NAME "dhcp"
 

src/include/gpxe/retry.h

 
 #include <gpxe/list.h>
 
+/** Default timeout value */
+#define DEFAULT_MIN_TIMEOUT ( TICKS_PER_SEC / 4 )
+
+/** Limit after which the timeout will be deemed permanent */
+#define DEFAULT_MAX_TIMEOUT ( 10 * TICKS_PER_SEC )
+
 /** A retry timer */
 struct retry_timer {
 	/** List of active timers */
 	struct list_head list;
 	/** Timeout value (in ticks) */
 	unsigned long timeout;
+	/** Minimum timeout value (in ticks)
+	 *
+	 * A value of zero means "use default timeout."
+	 */
+	unsigned long min_timeout;
+	/** Maximum timeout value before failure (in ticks)
+	 *
+	 * A value of zero means "use default timeout."
+	 */
+	unsigned long max_timeout;
 	/** Start time (in ticks)
 	 *
 	 * A start time of zero indicates a stopped timer.

src/net/retry.c

  * 
  */
 
-/** Default timeout value */
-#define MIN_TIMEOUT ( TICKS_PER_SEC / 4 )
-
-/** Limit after which the timeout will be deemed permanent */
-#define MAX_TIMEOUT ( 10 * TICKS_PER_SEC )
-
 /* The theoretical minimum that the algorithm in stop_timer() can
  * adjust the timeout back down to is seven ticks, so set the minimum
  * timeout to at least that value for the sake of consistency.
  */
-#if MIN_TIMEOUT < 7
-#undef MIN_TIMEOUT
 #define MIN_TIMEOUT 7
-#endif
 
 /** List of running timers */
 static LIST_HEAD ( timers );
 	if ( ! timer_running ( timer ) )
 		list_add ( &timer->list, &timers );
 	timer->start = currticks();
-	if ( timer->timeout < MIN_TIMEOUT )
-		timer->timeout = MIN_TIMEOUT;
+
+	/* 0 means "use default timeout" */
+	if ( timer->min_timeout == 0 )
+		timer->min_timeout = DEFAULT_MIN_TIMEOUT;
+	/* We must never be less than MIN_TIMEOUT under any circumstances */
+	if ( timer->min_timeout < MIN_TIMEOUT )
+		timer->min_timeout = MIN_TIMEOUT;
+	/* Honor user-specified minimum timeout */
+	if ( timer->timeout < timer->min_timeout )
+		timer->timeout = timer->min_timeout;
+
 	DBG2 ( "Timer %p started at time %ld (expires at %ld)\n",
 	       timer, timer->start, ( timer->start + timer->timeout ) );
 }
 
 	/* Back off the timeout value */
 	timer->timeout <<= 1;
-	if ( ( fail = ( timer->timeout > MAX_TIMEOUT ) ) )
-		timer->timeout = MAX_TIMEOUT;
+	if ( timer->max_timeout == 0 ) /* 0 means "use default timeout" */
+		timer->max_timeout = DEFAULT_MAX_TIMEOUT;
+	if ( ( fail = ( timer->timeout > timer->max_timeout ) ) )
+		timer->timeout = timer->max_timeout;
 	DBG ( "Timer %p timeout backed off to %ld\n",
 	      timer, timer->timeout );
 

src/net/udp/dhcp.c

 	xfer_init ( &dhcp->xfer, &dhcp_xfer_operations, &dhcp->refcnt );
 	dhcp->netdev = netdev_get ( netdev );
 	dhcp->timer.expired = dhcp_timer_expired;
+	dhcp->timer.min_timeout = DHCP_MIN_TIMEOUT;
+	dhcp->timer.max_timeout = DHCP_MAX_TIMEOUT;
 	dhcp->start = currticks();
 
 	/* Instantiate child objects and attach to our interfaces */