[dhcp] Omit ProxyDHCPREQUEST if PXE options are present in ProxyDHCPOFFER

Some ProxyDHCP implementations seem to violate the PXE specification
by expecting the client to retain options from the ProxyDHCPOFFER
rather than issuing a separate ProxyDHCPREQUEST.

Work around such broken clients by retaining the ProxyDHCPOFFER
packet, and proceeding to a ProxyDHCPREQUEST only if the
ProxyDHCPOFFER does not already contain PXE options.

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

src/net/udp/dhcp.c

 	int no_pxedhcp;
 	/** ProxyDHCP server */
 	struct in_addr proxy_server;
-	/** ProxyDHCP port */
-	uint16_t proxy_port;
-	/** ProxyDHCP server priority */
+	/** ProxyDHCP offer */
+	struct dhcp_packet *proxy_offer;
+	/** ProxyDHCP offer priority */
 	int proxy_priority;
 
 	/** PXE Boot Server type */
 		container_of ( refcnt, struct dhcp_session, refcnt );
 
 	netdev_put ( dhcp->netdev );
+	dhcppkt_put ( dhcp->proxy_offer );
 	free ( dhcp );
 }
 
 	start_timer_nodelay ( &dhcp->timer );
 }
 
+/**
+ * Check if DHCP packet contains PXE options
+ *
+ * @v dhcppkt		DHCP packet
+ * @ret has_pxeopts	DHCP packet contains PXE options
+ *
+ * It is assumed that the packet is already known to contain option 60
+ * set to "PXEClient".
+ */
+static int dhcp_has_pxeopts ( struct dhcp_packet *dhcppkt ) {
+
+	/* Check for a boot filename */
+	if ( dhcppkt_fetch ( dhcppkt, DHCP_BOOTFILE_NAME, NULL, 0 ) > 0 )
+		return 1;
+
+	/* Check for a PXE boot menu */
+	if ( dhcppkt_fetch ( dhcppkt, DHCP_PXE_BOOT_MENU, NULL, 0 ) > 0 )
+		return 1;
+
+	return 0;
+}
+
 /****************************************************************************
  *
  * DHCP state machine
 	char vci[9]; /* "PXEClient" */
 	int vci_len;
 	int has_pxeclient;
-	int pxeopts_len;
-	int has_pxeopts;
 	int8_t priority = 0;
 	uint8_t no_pxedhcp = 0;
 	unsigned long elapsed;
 				  vci, sizeof ( vci ) );
 	has_pxeclient = ( ( vci_len >= ( int ) sizeof ( vci ) ) &&
 			  ( strncmp ( "PXEClient", vci, sizeof (vci) ) == 0 ));
-
-	/* Identify presence of PXE-specific options */
-	pxeopts_len = dhcppkt_fetch ( dhcppkt, DHCP_PXE_BOOT_MENU, NULL, 0 );
-	has_pxeopts = ( pxeopts_len >= 0 );
-	if ( has_pxeclient )
-		DBGC ( dhcp, "%s", ( has_pxeopts ? " pxe" : " proxy" ) );
+	if ( has_pxeclient ) {
+		DBGC ( dhcp, "%s",
+		       ( dhcp_has_pxeopts ( dhcppkt ) ? " pxe" : " proxy" ) );
+	}
 
 	/* Identify priority */
 	dhcppkt_fetch ( dhcppkt, DHCP_EB_PRIORITY, &priority,
 	}
 
 	/* Select as ProxyDHCP offer, if applicable */
-	if ( has_pxeclient && ( msgtype == DHCPOFFER ) &&
+	if ( server_id.s_addr && has_pxeclient &&
 	     ( priority >= dhcp->proxy_priority ) ) {
-		/* If the offer already includes the PXE options, then
-		 * assume that we can send the ProxyDHCPREQUEST to
-		 * port 67 (since the DHCPDISCOVER that triggered this
-		 * ProxyDHCPOFFER was sent to port 67).  Otherwise,
-		 * send the ProxyDHCPREQUEST to port 4011.
-		 */
+		dhcppkt_put ( dhcp->proxy_offer );
 		dhcp->proxy_server = server_id;
-		dhcp->proxy_port = ( has_pxeopts ? htons ( BOOTPS_PORT )
-				     : htons ( PXE_PORT ) );
+		dhcp->proxy_offer = dhcppkt_get ( dhcppkt );
 		dhcp->proxy_priority = priority;
 	}
 
 
 	/* If we can't yet transition to DHCPREQUEST, do nothing */
 	elapsed = ( currticks() - dhcp->start );
-	if ( ! ( dhcp->no_pxedhcp || dhcp->proxy_server.s_addr ||
+	if ( ! ( dhcp->no_pxedhcp || dhcp->proxy_offer ||
 		 ( elapsed > PROXYDHCP_MAX_TIMEOUT ) ) )
 		return;
 
 			      struct in_addr server_id ) {
 	struct in_addr ip;
 	struct settings *parent;
+	struct settings *settings;
 	int rc;
 
 	DBGC ( dhcp, "DHCP %p %s from %s:%d", dhcp,
 
 	/* Register settings */
 	parent = netdev_settings ( dhcp->netdev );
-	if ( ( rc = register_settings ( &dhcppkt->settings, parent ) ) != 0 ){
+	settings = &dhcppkt->settings;
+	if ( ( rc = register_settings ( settings, parent ) ) != 0 ) {
 		DBGC ( dhcp, "DHCP %p could not register settings: %s\n",
 		       dhcp, strerror ( rc ) );
 		dhcp_finished ( dhcp, rc );
 		return;
 	}
 
-	/* Start ProxyDHCPREQUEST if applicable */
-	if ( dhcp->proxy_server.s_addr /* Have ProxyDHCP server */ &&
-	     ( ! dhcp->no_pxedhcp ) /* ProxyDHCP not disabled */ &&
-	     ( /* ProxyDHCP server is not just the DHCP server itself */
-	       ( dhcp->proxy_server.s_addr != dhcp->server.s_addr ) ||
-	       ( dhcp->proxy_port != htons ( BOOTPS_PORT ) ) ) ) {
-		dhcp_set_state ( dhcp, &dhcp_state_proxy );
-		return;
+	/* Perform ProxyDHCP if applicable */
+	if ( dhcp->proxy_offer /* Have ProxyDHCP offer */ &&
+	     ( ! dhcp->no_pxedhcp ) /* ProxyDHCP not disabled */ ) {
+		if ( dhcp_has_pxeopts ( dhcp->proxy_offer ) ) {
+			/* PXE options already present; register settings
+			 * without performing a ProxyDHCPREQUEST
+			 */
+			settings = &dhcp->proxy_offer->settings;
+			settings->name = PROXYDHCP_SETTINGS_NAME;
+			if ( ( rc = register_settings ( settings,
+							NULL ) ) != 0 ) {
+				DBGC ( dhcp, "DHCP %p could not register "
+				       "proxy settings: %s\n",
+				       dhcp, strerror ( rc ) );
+				dhcp_finished ( dhcp, rc );
+				return;
+			}
+		} else {
+			/* PXE options not present; use a ProxyDHCPREQUEST */
+			dhcp_set_state ( dhcp, &dhcp_state_proxy );
+			return;
+		}
 	}
 
 	/* Terminate DHCP */
 			   struct sockaddr_in *peer ) {
 	int rc;
 
-	DBGC ( dhcp, "DHCP %p ProxyDHCP REQUEST to %s:%d\n", dhcp,
-	       inet_ntoa ( dhcp->proxy_server ), ntohs ( dhcp->proxy_port ) );
+	DBGC ( dhcp, "DHCP %p ProxyDHCP REQUEST to %s\n", dhcp,
+	       inet_ntoa ( dhcp->proxy_server ) );
 
 	/* Set server ID */
 	if ( ( rc = dhcppkt_store ( dhcppkt, DHCP_SERVER_IDENTIFIER,
 
 	/* Set server address */
 	peer->sin_addr = dhcp->proxy_server;
-	peer->sin_port = dhcp->proxy_port;
+	peer->sin_port = htons ( PXE_PORT );
 
 	return 0;
 }
 			    struct dhcp_packet *dhcppkt,
 			    struct sockaddr_in *peer, uint8_t msgtype,
 			    struct in_addr server_id ) {
+	struct settings *settings = &dhcppkt->settings;
 	int rc;
 
 	DBGC ( dhcp, "DHCP %p %s from %s:%d", dhcp,
 	DBGC ( dhcp, "\n" );
 
 	/* Filter out unacceptable responses */
-	if ( peer->sin_port != dhcp->proxy_port )
+	if ( peer->sin_port != ntohs ( PXE_PORT ) )
 		return;
 	if ( ( msgtype != DHCPOFFER ) && ( msgtype != DHCPACK ) )
 		return;
 		return;
 
 	/* Register settings */
-	dhcppkt->settings.name = PROXYDHCP_SETTINGS_NAME;
-	if ( ( rc = register_settings ( &dhcppkt->settings, NULL ) ) != 0 ) {
-		DBGC ( dhcp, "DHCP %p could not register settings: %s\n",
+	settings->name = PROXYDHCP_SETTINGS_NAME;
+	if ( ( rc = register_settings ( settings, NULL ) ) != 0 ) {
+		DBGC ( dhcp, "DHCP %p could not register proxy settings: %s\n",
 		       dhcp, strerror ( rc ) );
 		dhcp_finished ( dhcp, rc );
 		return;