First version, based on the concepts in linux/skbuff.h

src/include/gpxe/pkbuff.h

@@ -0,0 +1,80 @@
+#ifndef _PKBUFF_H
+#define _PKBUFF_H
+
+/** @file
+ *
+ * Packet buffers
+ *
+ * Packet buffers are used to contain network packets.  Methods are
+ * provided for appending, prepending, etc. data.
+ *
+ */
+
+#include <stdint.h>
+#include <assert.h>
+
+/** A packet buffer
+ *
+ * This structure is used to represent a network packet within gPXE.
+ */
+struct pk_buff {
+	/** Head of the buffer */
+	void *head;
+	/** Start of data */
+	void *data;
+	/** End of data */
+	void *tail;
+	/** End of the buffer */
+        void *end;
+};
+
+/**
+ * Add data to start of packet buffer
+ *
+ * @v pkb	Packet buffer
+ * @v len	Length to add
+ * @ret data	Pointer to new start of buffer
+ */
+static inline void * pkb_push ( struct pk_buff *pkb, size_t len ) {
+	pkb->data -= len;
+	assert ( pkb->data >= pkb->head );
+	return pkb->data;
+}
+
+/**
+ * Remove data from start of packet buffer
+ *
+ * @v pkb	Packet buffer
+ * @v len	Length to remove
+ * @ret data	Pointer to new start of buffer
+ */
+static inline void * pkb_pull ( struct pk_buff *pkb, size_t len ) {
+	pkb->data += len;
+	assert ( pkb->data >= pkb->tail );
+	return pkb->data;
+}
+
+/**
+ * Add data to end of packet buffer
+ *
+ * @v pkb	Packet buffer
+ * @v len	Length to add
+ * @ret data	Pointer to newly added space
+ */
+static inline void * pkb_put ( struct pk_buff *pkb, size_t len ) {
+	void *old_tail = pkb->tail;
+	pkb->tail += len;
+	assert ( pkb->tail <= pkb->end );
+	return old_tail;
+}
+
+/**
+ * Empty a packet buffer
+ *
+ * @v pkb	Packet buffer
+ */
+static inline void pkb_empty ( struct pk_buff *pkb ) {
+	pkb->tail = pkb->data;
+}
+
+#endif /* _PKBUFF_H */