[PATCH v3 1/3] net: Get pxe config file from dhcp option 209

[seanedmond@linux.microsoft.com]

From: Sean Edmond <seanedmond@microsoft.com>

Allow dhcp server pass pxe config file full path by using option 209
as specified in RFC5071.

Signed-off-by: Sean Edmond <seanedmond@microsoft.com>
---
 cmd/Kconfig |  4 ++++
 cmd/pxe.c   | 10 ++++++++++
 net/bootp.c | 21 +++++++++++++++++++++
 net/bootp.h |  2 ++
 4 files changed, 37 insertions(+)

diff --git a/cmd/Kconfig b/cmd/Kconfig
index fd16c3a48e5..df6d71c103f 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1840,6 +1840,10 @@ config BOOTP_PXE_CLIENTARCH
 	default 0x15 if ARM
 	default 0x0 if X86
 
+config BOOTP_PXE_DHCP_OPTION
+	bool "Request & store 'pxe_configfile' from BOOTP/DHCP server"
+	depends on BOOTP_PXE
+
 config BOOTP_VCI_STRING
 	string
 	depends on CMD_BOOTP
diff --git a/cmd/pxe.c b/cmd/pxe.c
index 704589702f2..9404f445187 100644
--- a/cmd/pxe.c
+++ b/cmd/pxe.c
@@ -65,6 +65,8 @@ static int pxe_dhcp_option_path(struct pxe_context *ctx, unsigned long pxefile_a
 	int ret = get_pxe_file(ctx, pxelinux_configfile, pxefile_addr_r);
 
 	free(pxelinux_configfile);
+	/* set to NULL to avoid double-free if DHCP is tried again */
+	pxelinux_configfile = NULL;
 
 	return ret;
 }
@@ -141,6 +143,14 @@ int pxe_get(ulong pxefile_addr_r, char **bootdirp, ulong *sizep, bool use_ipv6)
 			  env_get("bootfile"), use_ipv6))
 		return -ENOMEM;
 
+	if (IS_ENABLED(CONFIG_BOOTP_PXE_DHCP_OPTION) &&
+	    pxelinux_configfile && !use_ipv6) {
+		if (pxe_dhcp_option_path(&ctx, pxefile_addr_r) > 0)
+			goto done;
+
+		goto error_exit;
+	}
+
 	if (IS_ENABLED(CONFIG_DHCP6_PXE_DHCP_OPTION) &&
 	    pxelinux_configfile && use_ipv6) {
 		if (pxe_dhcp_option_path(&ctx, pxefile_addr_r) > 0)
diff --git a/net/bootp.c b/net/bootp.c
index 7b0f45e18a9..24547cf7bfd 100644
--- a/net/bootp.c
+++ b/net/bootp.c
@@ -26,6 +26,7 @@
 #ifdef CONFIG_BOOTP_RANDOM_DELAY
 #include "net_rand.h"
 #endif
+#include <malloc.h>
 
 #define BOOTP_VENDOR_MAGIC	0x63825363	/* RFC1048 Magic Cookie */
 
@@ -601,6 +602,10 @@ static int dhcp_extended(u8 *e, int message_type, struct in_addr server_ip,
 	*e++  = 42;
 	*cnt += 1;
 #endif
+	if (IS_ENABLED(CONFIG_BOOTP_PXE_DHCP_OPTION)) {
+		*e++ = DHCP_OPTION_PXE_CONFIG_FILE;	/* PXELINUX Config File */
+		*cnt += 1;
+	}
 	/* no options, so back up to avoid sending an empty request list */
 	if (*cnt == 0)
 		e -= 2;
@@ -909,6 +914,22 @@ static void dhcp_process_options(uchar *popt, uchar *end)
 				net_boot_file_name[size] = 0;
 			}
 			break;
+		case DHCP_OPTION_PXE_CONFIG_FILE:	/* PXELINUX Config File */
+			if (IS_ENABLED(CONFIG_BOOTP_PXE_DHCP_OPTION)) {
+				/* In case it has already been allocated when get DHCP Offer packet,
+				 * free first to avoid memory leak.
+				 */
+				if (pxelinux_configfile)
+					free(pxelinux_configfile);
+
+				pxelinux_configfile = (char *)malloc((oplen + 1) * sizeof(char));
+
+				if (pxelinux_configfile)
+					strlcpy(pxelinux_configfile, popt + 2, oplen + 1);
+				else
+					printf("Error: Failed to allocate pxelinux_configfile\n");
+			}
+			break;
 		default:
 #if defined(CONFIG_BOOTP_VENDOREX)
 			if (dhcp_vendorex_proc(popt))
diff --git a/net/bootp.h b/net/bootp.h
index 4e32b19d424..24b32c73f62 100644
--- a/net/bootp.h
+++ b/net/bootp.h
@@ -91,6 +91,8 @@ typedef enum { INIT,
 #define DHCP_NAK      6
 #define DHCP_RELEASE  7
 
+#define DHCP_OPTION_PXE_CONFIG_FILE	209	/* "ConfigFile" option according to rfc5071 */
+
 /**********************************************************************/
 
 #endif /* __BOOTP_H__ */
-- 
2.42.0