[cachedhcp] Retain cached DHCPACK after startup if not already consumed

We currently free an unclaimed cached DHCPACK immediately after
startup, in order to free up memory.  This prevents the cached DHCPACK
from being applied to a device that is created after startup, such as
a VLAN device created via the "vcreate" command.

Retain any unclaimed DHCPACK after startup to allow it to be matched
against (and applied to) any device that gets created at runtime.
Free the DHCPACK during shutdown if it still remains unclaimed, in
order to exit with memory cleanly freed.

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

1 files changed, 22 insertions, 4 deletions

diff --git a/src/core/cachedhcp.c b/src/core/cachedhcp.c
index ef214662..60213f02 100644
--- a/src/core/cachedhcp.c
+++ b/src/core/cachedhcp.c
@@ -246,31 +246,49 @@ int cachedhcp_record ( struct cached_dhcp_packet *cache, unsigned int vlan,
 }
 
 /**
- * Cached DHCPACK startup function
+ * Cached DHCP packet startup function
  *
  */
 static void cachedhcp_startup ( void ) {
 
 	/* Apply cached ProxyDHCPOFFER, if any */
 	cachedhcp_apply ( &cached_proxydhcp, NULL );
+	cachedhcp_free ( &cached_proxydhcp );
 
 	/* Apply cached PXEBSACK, if any */
 	cachedhcp_apply ( &cached_pxebs, NULL );
+	cachedhcp_free ( &cached_pxebs );
 
-	/* Free any remaining cached packets */
+	/* Report unclaimed DHCPACK, if any.  Do not free yet, since
+	 * it may still be claimed by a dynamically created device
+	 * such as a VLAN device.
+	 */
 	if ( cached_dhcpack.dhcppkt ) {
 		DBGC ( colour, "CACHEDHCP %s unclaimed\n",
 		       cached_dhcpack.name );
 	}
+}
+
+/**
+ * Cached DHCP packet shutdown function
+ *
+ * @v booting		System is shutting down for OS boot
+ */
+static void cachedhcp_shutdown ( int booting __unused ) {
+
+	/* Free cached DHCPACK, if any */
+	if ( cached_dhcpack.dhcppkt ) {
+		DBGC ( colour, "CACHEDHCP %s never claimed\n",
+		       cached_dhcpack.name );
+	}
 	cachedhcp_free ( &cached_dhcpack );
-	cachedhcp_free ( &cached_proxydhcp );
-	cachedhcp_free ( &cached_pxebs );
 }
 
 /** Cached DHCPACK startup function */
 struct startup_fn cachedhcp_startup_fn __startup_fn ( STARTUP_LATE ) = {
 	.name = "cachedhcp",
 	.startup = cachedhcp_startup,
+	.shutdown = cachedhcp_shutdown,
 };
 
 /**