From: Sean Edmond <seanedm...@microsoft.com>

Addresses feedback from latest review:
- Enable option 209 by default
- Set pxelinux_configfile to NULL to avoid potential double free
- change hardcoced 209 to a define

Signed-off-by: Sean Edmond <seanedm...@microsoft.com>
---

changes in v4:
- rebase master and resolve conflicts
- change commit description for this patch (this is now
  an enhancement patch)
- default y for BOOTP_PXE_DHCP_OPTION (feedback from review)

changes in v3:
- add define for option 209 and rfc5071 reference

 cmd/Kconfig | 1 +
 cmd/pxe.c   | 2 ++
 net/bootp.c | 4 ++--
 net/bootp.h | 2 ++
 4 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/cmd/Kconfig b/cmd/Kconfig
index df6d71c103f..ae846b204dc 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1842,6 +1842,7 @@ config BOOTP_PXE_CLIENTARCH
 
 config BOOTP_PXE_DHCP_OPTION
        bool "Request & store 'pxe_configfile' from BOOTP/DHCP server"
+       default y
        depends on BOOTP_PXE
 
 config BOOTP_VCI_STRING
diff --git a/cmd/pxe.c b/cmd/pxe.c
index 21134eb7a30..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;
 }
diff --git a/net/bootp.c b/net/bootp.c
index 68002909634..24547cf7bfd 100644
--- a/net/bootp.c
+++ b/net/bootp.c
@@ -603,7 +603,7 @@ static int dhcp_extended(u8 *e, int message_type, struct 
in_addr server_ip,
        *cnt += 1;
 #endif
        if (IS_ENABLED(CONFIG_BOOTP_PXE_DHCP_OPTION)) {
-               *e++ = 209;     /* PXELINUX Config File */
+               *e++ = DHCP_OPTION_PXE_CONFIG_FILE;     /* PXELINUX Config File 
*/
                *cnt += 1;
        }
        /* no options, so back up to avoid sending an empty request list */
@@ -914,7 +914,7 @@ static void dhcp_process_options(uchar *popt, uchar *end)
                                net_boot_file_name[size] = 0;
                        }
                        break;
-               case 209:       /* PXELINUX Config File */
+               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.
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

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