[pxe] Always retrieve cached DHCPACK and apply to relevant network device

When chainloading, always retrieve the cached DHCPACK packet from the
underlying PXE stack, and apply it as the original contents of the
"net<X>.dhcp" settings block.  This allows cached DHCP settings to be
used for any chainloaded iPXE binary (not just undionly.kkpxe).

This change eliminates the undocumented "use-cached" setting.  Issuing
the "dhcp" command will now always result in a fresh DHCP request.

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

1 files changed, 48 insertions, 3 deletions

diff --git a/src/arch/i386/prefix/pxeprefix.S b/src/arch/i386/prefix/pxeprefix.S
index 05db9894c..6e29c7949 100644
--- a/src/arch/i386/prefix/pxeprefix.S
+++ b/src/arch/i386/prefix/pxeprefix.S
@@ -5,6 +5,8 @@ FILE_LICENCE ( GPL2_OR_LATER )
 #define PXENV_UNDI_GET_IFACE_INFO	0x0013
 #define	PXENV_STOP_UNDI			0x0015
 #define PXENV_UNLOAD_STACK		0x0070
+#define PXENV_GET_CACHED_INFO		0x0071
+#define PXENV_PACKET_TYPE_DHCP_ACK		0x0002
 #define PXENV_FILE_CMDLINE		0x00e8
 
 #define PXE_HACK_EB54			0x0001
@@ -20,7 +22,18 @@ FILE_LICENCE ( GPL2_OR_LATER )
 #define EB_MAGIC_1 ( 'E' + ( 't' << 8 ) + ( 'h' << 16 ) + ( 'e' << 24 ) )
 #define EB_MAGIC_2 ( 'r' + ( 'b' << 8 ) + ( 'o' << 16 ) + ( 'o' << 24 ) )
 
+/* Prefix memory layout:
+ *
+ *     iPXE binary image
+ *     Temporary stack
+ *     Temporary copy of DHCPACK packet
+ *     Temporary copy of command line
+ */
 #define PREFIX_STACK_SIZE 2048
+#define PREFIX_TEMP_DHCPACK PREFIX_STACK_SIZE
+#define PREFIX_TEMP_DHCPACK_SIZE ( 1260 /* sizeof ( BOOTPLAYER_t ) */ )
+#define PREFIX_TEMP_CMDLINE ( PREFIX_TEMP_DHCPACK + PREFIX_TEMP_DHCPACK_SIZE )
+#define PREFIX_TEMP_CMDLINE_SIZE 4096
 
 /*****************************************************************************
  * Entry point:	set operating context, print welcome message
@@ -382,6 +395,32 @@ get_iface_type:
 99:	movb	$0x0a, %al
 	call	print_character
 
+/*****************************************************************************
+ * Get cached DHCP_ACK packet
+ *****************************************************************************
+ */
+get_dhcpack:
+	/* Issue PXENV_GET_CACHED_INFO */
+	xorl	%esi, %esi
+	movw	%ss, %si
+	movw	%si, ( pxe_parameter_structure + 0x08 )
+	movw	$PREFIX_TEMP_DHCPACK, ( pxe_parameter_structure + 0x06 )
+	movw	$PREFIX_TEMP_DHCPACK_SIZE, ( pxe_parameter_structure +0x04 )
+	movw	$PXENV_PACKET_TYPE_DHCP_ACK, ( pxe_parameter_structure + 0x02 )
+	movw	$PXENV_GET_CACHED_INFO, %bx
+	call	pxe_call
+	jnc	1f
+	call	print_pxe_error
+	jmp	99f
+1:	/* Store physical address of packet */
+	shll	$4, %esi
+	addl	$PREFIX_TEMP_DHCPACK, %esi
+	movl	%esi, pxe_cached_dhcpack
+99:
+	.section ".prefix.data", "aw", @progbits
+pxe_cached_dhcpack:
+	.long	0
+	.previous
 
 /*****************************************************************************
  * Check for a command line
@@ -392,8 +431,8 @@ get_cmdline:
 	xorl	%esi, %esi
 	movw	%ss, %si
 	movw	%si, ( pxe_parameter_structure + 0x06 )
-	movw	$PREFIX_STACK_SIZE, ( pxe_parameter_structure + 0x04 )
-	movw	$0xffff, ( pxe_parameter_structure + 0x02 )
+	movw	$PREFIX_TEMP_CMDLINE, ( pxe_parameter_structure + 0x04 )
+	movw	$PREFIX_TEMP_CMDLINE_SIZE, ( pxe_parameter_structure + 0x02 )
 	movw	$PXENV_FILE_CMDLINE, %bx
 	call	pxe_call
 	jc	99f  /* Suppress errors; this is an iPXE extension API call */
@@ -403,7 +442,7 @@ get_cmdline:
 	jz	99f
 	/* Record command line */
 	shll	$4, %esi
-	addl	$PREFIX_STACK_SIZE, %esi
+	addl	$PREFIX_TEMP_CMDLINE, %esi
 	movl	%esi, pxe_cmdline
 99:
 	.section ".prefix.data", "aw", @progbits
@@ -761,6 +800,9 @@ run_ipxe:
 	/* Retrieve PXE command line, if any */
 	movl	pxe_cmdline, %esi
 
+	/* Retrieve cached DHCPACK, if any */
+	movl	pxe_cached_dhcpack, %ecx
+
 	/* Jump to .text16 segment with %ds pointing to .data16 */
 	movw	%bx, %ds
 	pushw	%ax
@@ -774,6 +816,9 @@ run_ipxe:
 	/* Store command-line pointer */
 	movl	%esi, cmdline_phys
 
+	/* Store cached DHCPACK pointer */
+	movl	%ecx, cached_dhcpack_phys
+
 	/* Run main program */
 	pushl	$main
 	pushw	%cs