[dhcp] Extract timing parameters out to config/dhcp.h
iPXE uses DHCP timeouts loosely based on values recommended by the specification, but often abbreviated to reduce timeouts for reliable and/or simple network topologies. Extract the DHCP timing parameters to config/dhcp.h and document them. The resulting default iPXE behavior is exactly the same, but downstreams are now afforded the opportunity to implement spec-compliant behavior via config file overrides. Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Modified-by: Michael Brown <mcb30@ipxe.org> Signed-off-by: Michael Brown <mcb30@ipxe.org>
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#ifndef CONFIG_DHCP_H
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#define CONFIG_DHCP_H
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/** @file
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*
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* DHCP configuration
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*
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*/
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FILE_LICENCE ( GPL2_OR_LATER );
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#include <config/defaults.h>
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/*
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* DHCP and PXE Boot Server timeout parameters
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*
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* Initial and final timeout for DHCP discovery
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*
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* The PXE spec indicates discover request are sent 4 times, with
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* timeouts of 4, 8, 16, 32 seconds. iPXE by default uses 1, 2, 4, 8.
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*/
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#define DHCP_DISC_START_TIMEOUT_SEC 1
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#define DHCP_DISC_END_TIMEOUT_SEC 10
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//#define DHCP_DISC_START_TIMEOUT_SEC 4 /* as per PXE spec */
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//#define DHCP_DISC_END_TIMEOUT_SEC 32 /* as per PXE spec */
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/*
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* ProxyDHCP offers are given precedence by continue to wait for them
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* after a valid DHCPOFFER is received. We'll wait through this
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* timeout for it. The PXE spec indicates waiting through the 4 & 8
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* second timeouts, iPXE by default stops after 2.
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*/
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#define DHCP_DISC_PROXY_TIMEOUT_SEC 2
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//#define DHCP_DISC_PROXY_TIMEOUT_SEC 11 /* as per PXE spec */
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/*
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* Per the PXE spec, requests are also tried 4 times, but at timeout
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* intervals of 1, 2, 3, 4 seconds. To adapt this to an exponential
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* backoff timer, we can either do 1, 2, 4, 8, ie. 4 retires with a
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* longer interval or start at 0 (0.25s) for 0.25, 0.5, 1, 2, 4,
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* ie. one extra try and shorter initial timeouts. iPXE by default
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* does a combination of both, starting at 0 and going through the 8
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* second timeout.
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*/
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#define DHCP_REQ_START_TIMEOUT_SEC 0
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#define DHCP_REQ_END_TIMEOUT_SEC 10
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//#define DHCP_REQ_END_TIMEOUT_SEC 4 /* as per PXE spec */
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/*
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* A ProxyDHCP offer without PXE options also goes through a request
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* phase using these same parameters, but note the early break below.
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*/
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#define DHCP_PROXY_START_TIMEOUT_SEC 0
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#define DHCP_PROXY_END_TIMEOUT_SEC 10
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//#define DHCP_PROXY_END_TIMEOUT_SEC 8 /* as per PXE spec */
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/*
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* A ProxyDHCP request timeout should not induce a failure condition,
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* so we always want to break before the above set of timers expire.
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* The iPXE default value of 2 breaks at the first timeout after 2
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* seconds, which will be after the 2 second timeout.
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*/
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#define DHCP_REQ_PROXY_TIMEOUT_SEC 2
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//#define DHCP_REQ_PROXY_TIMEOUT_SEC 7 /* as per PXE spec */
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/*
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* Per the PXE spec, a PXE boot server request is also be retried 4
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* times at timeouts of 1, 2, 3, 4. iPXE uses the same timeouts as
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* discovery, 1, 2, 4, 8, but will move on to the next server if
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* available after an elapsed time greater than 3 seconds, therefore
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* effectively only sending 3 tries at timeouts of 1, 2, 4.
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*/
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#define PXEBS_START_TIMEOUT_SEC 1
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#define PXEBS_END_TIMEOUT_SEC 10
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//#define PXEBS_START_TIMEOUT_SEC 0 /* as per PXE spec */
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//#define PXEBS_END_TIMEOUT_SEC 8 /* as per PXE spec */
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/*
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* Increment to the next PXE Boot server, if available, after this
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* this much time has elapsed.
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*/
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#define PXEBS_MAX_TIMEOUT_SEC 3
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//#define PXEBS_MAX_TIMEOUT_SEC 7 /* as per PXE spec */
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#include <config/local/dhcp.h>
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#endif /* CONFIG_DHCP_H */
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@ -639,16 +639,6 @@ struct dhcphdr {
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*/
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#define DHCP_MIN_LEN 552
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/** Timeouts for sending DHCP packets */
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#define DHCP_MIN_TIMEOUT ( 1 * TICKS_PER_SEC )
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#define DHCP_MAX_TIMEOUT ( 10 * TICKS_PER_SEC )
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/** Maximum time that we will wait for ProxyDHCP responses */
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#define PROXYDHCP_MAX_TIMEOUT ( 2 * TICKS_PER_SEC )
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/** Maximum time that we will wait for Boot Server responses */
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#define PXEBS_MAX_TIMEOUT ( 3 * TICKS_PER_SEC )
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/** Settings block name used for DHCP responses */
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#define DHCP_SETTINGS_NAME "dhcp"
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@ -44,6 +44,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
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#include <ipxe/dhcppkt.h>
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#include <ipxe/dhcp_arch.h>
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#include <ipxe/features.h>
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#include <config/dhcp.h>
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/** @file
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*
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@ -171,8 +172,9 @@ struct dhcp_session_state {
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void ( * expired ) ( struct dhcp_session *dhcp );
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/** Transmitted message type */
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uint8_t tx_msgtype;
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/** Apply minimum timeout */
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uint8_t apply_min_timeout;
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/** Timeout parameters */
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uint8_t min_timeout_sec;
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uint8_t max_timeout_sec;
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};
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static struct dhcp_session_state dhcp_state_discover;
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@ -272,9 +274,8 @@ static void dhcp_set_state ( struct dhcp_session *dhcp,
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dhcp->state = state;
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dhcp->start = currticks();
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stop_timer ( &dhcp->timer );
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dhcp->timer.min_timeout =
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( state->apply_min_timeout ? DHCP_MIN_TIMEOUT : 0 );
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dhcp->timer.max_timeout = DHCP_MAX_TIMEOUT;
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dhcp->timer.min_timeout = state->min_timeout_sec * TICKS_PER_SEC;
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dhcp->timer.max_timeout = state->max_timeout_sec * TICKS_PER_SEC;
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start_timer_nodelay ( &dhcp->timer );
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}
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@ -415,7 +416,7 @@ static void dhcp_discovery_rx ( struct dhcp_session *dhcp,
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/* If we can't yet transition to DHCPREQUEST, do nothing */
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elapsed = ( currticks() - dhcp->start );
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if ( ! ( dhcp->no_pxedhcp || dhcp->proxy_offer ||
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( elapsed > PROXYDHCP_MAX_TIMEOUT ) ) )
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( elapsed > DHCP_DISC_PROXY_TIMEOUT_SEC * TICKS_PER_SEC ) ) )
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return;
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/* Transition to DHCPREQUEST */
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@ -431,7 +432,8 @@ static void dhcp_discovery_expired ( struct dhcp_session *dhcp ) {
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unsigned long elapsed = ( currticks() - dhcp->start );
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/* Give up waiting for ProxyDHCP before we reach the failure point */
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if ( dhcp->offer.s_addr && ( elapsed > PROXYDHCP_MAX_TIMEOUT ) ) {
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if ( dhcp->offer.s_addr &&
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( elapsed > DHCP_DISC_PROXY_TIMEOUT_SEC * TICKS_PER_SEC ) ) {
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dhcp_set_state ( dhcp, &dhcp_state_request );
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return;
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}
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@ -447,7 +449,8 @@ static struct dhcp_session_state dhcp_state_discover = {
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.rx = dhcp_discovery_rx,
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.expired = dhcp_discovery_expired,
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.tx_msgtype = DHCPDISCOVER,
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.apply_min_timeout = 1,
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.min_timeout_sec = DHCP_DISC_START_TIMEOUT_SEC,
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.max_timeout_sec = DHCP_DISC_END_TIMEOUT_SEC,
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};
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/**
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@ -584,7 +587,8 @@ static struct dhcp_session_state dhcp_state_request = {
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.rx = dhcp_request_rx,
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.expired = dhcp_request_expired,
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.tx_msgtype = DHCPREQUEST,
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.apply_min_timeout = 0,
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.min_timeout_sec = DHCP_REQ_START_TIMEOUT_SEC,
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.max_timeout_sec = DHCP_REQ_END_TIMEOUT_SEC,
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};
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/**
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@ -669,7 +673,7 @@ static void dhcp_proxy_expired ( struct dhcp_session *dhcp ) {
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unsigned long elapsed = ( currticks() - dhcp->start );
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/* Give up waiting for ProxyDHCP before we reach the failure point */
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if ( elapsed > PROXYDHCP_MAX_TIMEOUT ) {
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if ( elapsed > DHCP_REQ_PROXY_TIMEOUT_SEC * TICKS_PER_SEC ) {
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dhcp_finished ( dhcp, 0 );
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return;
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}
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@ -685,7 +689,8 @@ static struct dhcp_session_state dhcp_state_proxy = {
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.rx = dhcp_proxy_rx,
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.expired = dhcp_proxy_expired,
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.tx_msgtype = DHCPREQUEST,
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.apply_min_timeout = 0,
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.min_timeout_sec = DHCP_PROXY_START_TIMEOUT_SEC,
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.max_timeout_sec = DHCP_PROXY_END_TIMEOUT_SEC,
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};
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/**
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/* Give up waiting before we reach the failure point, and fail
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* over to the next server in the attempt list
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*/
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if ( elapsed > PXEBS_MAX_TIMEOUT ) {
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if ( elapsed > PXEBS_MAX_TIMEOUT_SEC * TICKS_PER_SEC ) {
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dhcp->pxe_attempt++;
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if ( dhcp->pxe_attempt->s_addr ) {
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dhcp_set_state ( dhcp, &dhcp_state_pxebs );
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.rx = dhcp_pxebs_rx,
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.expired = dhcp_pxebs_expired,
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.tx_msgtype = DHCPREQUEST,
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.apply_min_timeout = 1,
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.min_timeout_sec = PXEBS_START_TIMEOUT_SEC,
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.max_timeout_sec = PXEBS_END_TIMEOUT_SEC,
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};
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/****************************************************************************
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