From: Michael Brown <mcb30@ipxe.org>
Date: Tue, 19 Jan 2021 12:21:28 +0000 (+0000)
Subject: [dhcp] Continue transmitting DHCPDISCOVER while link is blocked
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=860620459589444fd3c7c329aa7b177b5c9a4039;p=thirdparty%2Fipxe.git

[dhcp] Continue transmitting DHCPDISCOVER while link is blocked

Continue to transmit DHCPDISCOVER while waiting for a blocked link, in
order to support mechanisms such as Cisco MAC Authentication Bypass
that require repeated transmission attempts in order to trigger the
action that will result in the link becoming unblocked.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
---

diff --git a/src/net/udp/dhcp.c b/src/net/udp/dhcp.c
index 3a3666c9a..4ebd38bbb 100644
--- a/src/net/udp/dhcp.c
+++ b/src/net/udp/dhcp.c
@@ -451,17 +451,6 @@ static void dhcp_discovery_rx ( struct dhcp_session *dhcp,
 static void dhcp_discovery_expired ( struct dhcp_session *dhcp ) {
 	unsigned long elapsed = ( currticks() - dhcp->start );
 
-	/* If link is blocked, defer DHCP discovery (and reset timeout) */
-	if ( netdev_link_blocked ( dhcp->netdev ) &&
-	     ( dhcp->count <= DHCP_DISC_MAX_DEFERRALS ) ) {
-		DBGC ( dhcp, "DHCP %p deferring discovery\n", dhcp );
-		dhcp->start = currticks();
-		start_timer_fixed ( &dhcp->timer,
-				    ( DHCP_DISC_START_TIMEOUT_SEC *
-				      TICKS_PER_SEC ) );
-		return;
-	}
-
 	/* Give up waiting for ProxyDHCP before we reach the failure point */
 	if ( dhcp->offer.s_addr &&
 	     ( elapsed > DHCP_DISC_PROXY_TIMEOUT_SEC * TICKS_PER_SEC ) ) {
@@ -469,8 +458,18 @@ static void dhcp_discovery_expired ( struct dhcp_session *dhcp ) {
 		return;
 	}
 
-	/* Otherwise, retransmit current packet */
+	/* Retransmit current packet */
 	dhcp_tx ( dhcp );
+
+	/* If link is blocked, defer DHCP discovery timeout */
+	if ( netdev_link_blocked ( dhcp->netdev ) &&
+	     ( dhcp->count <= DHCP_DISC_MAX_DEFERRALS ) ) {
+		DBGC ( dhcp, "DHCP %p deferring discovery timeout\n", dhcp );
+		dhcp->start = currticks();
+		start_timer_fixed ( &dhcp->timer,
+				    ( DHCP_DISC_START_TIMEOUT_SEC *
+				      TICKS_PER_SEC ) );
+	}
 }
 
 /** DHCP discovery state operations */