From 6c50564724bcce292fbe76010d637390c17d407a Mon Sep 17 00:00:00 2001
From: Michael Brown <mcb30@etherboot.org>
Date: Sat, 27 May 2006 13:39:45 +0000
Subject: [PATCH] Make PKB_ZLEN the minimum possible size of packet buffer (to
 allow for hardware that can't autopad).

---
 src/include/gpxe/pkbuff.h | 9 +++++++++
 src/net/pkbuff.c          | 4 ++++
 2 files changed, 13 insertions(+)

diff --git a/src/include/gpxe/pkbuff.h b/src/include/gpxe/pkbuff.h
index 92244fd5..6c504029 100644
--- a/src/include/gpxe/pkbuff.h
+++ b/src/include/gpxe/pkbuff.h
@@ -28,6 +28,15 @@ struct ll_protocol;
  */
 #define PKBUFF_ALIGN 2048
 
+/**
+ * Minimum packet buffer length
+ *
+ * alloc_pkb() will round up the allocated length to this size if
+ * necessary.  This is used on behalf of hardware that is not capable
+ * of auto-padding.
+ */
+#define PKB_ZLEN 64
+
 /** A packet buffer
  *
  * This structure is used to represent a network packet within gPXE.
diff --git a/src/net/pkbuff.c b/src/net/pkbuff.c
index 964fbf62..ac308830 100644
--- a/src/net/pkbuff.c
+++ b/src/net/pkbuff.c
@@ -39,6 +39,10 @@ struct pk_buff * alloc_pkb ( size_t len ) {
 	struct pk_buff *pkb = NULL;
 	void *data;
 
+	/* Pad to minimum length */
+	if ( len < PKB_ZLEN )
+		len = PKB_ZLEN;
+
 	/* Align buffer length */
 	len = ( len + __alignof__( *pkb ) - 1 ) & ~( __alignof__( *pkb ) - 1 );