[ipv4] Generalise fragment reassembly mechanism

Generalise the concept of fragment reassembly to allow for code
sharing between IPv4 and IPv6 protocols.

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

src/include/ipxe/fragment.h

@@ -0,0 +1,68 @@
+#ifndef _IPXE_FRAGMENT_H
+#define _IPXE_FRAGMENT_H
+
+/** @file
+ *
+ * Fragment reassembly
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <ipxe/list.h>
+#include <ipxe/iobuf.h>
+#include <ipxe/retry.h>
+
+/** Fragment reassembly timeout */
+#define FRAGMENT_TIMEOUT ( TICKS_PER_SEC / 2 )
+
+/** A fragment reassembly buffer */
+struct fragment {
+	/* List of fragment reassembly buffers */
+	struct list_head list;
+	/** Reassembled packet */
+	struct io_buffer *iobuf;
+	/** Length of non-fragmentable portion of reassembled packet */
+	size_t hdrlen;
+	/** Reassembly timer */
+	struct retry_timer timer;
+};
+
+/** A fragment reassembler */
+struct fragment_reassembler {
+	/** List of fragment reassembly buffers */
+	struct list_head list;
+	/**
+	 * Check if fragment matches fragment reassembly buffer
+	 *
+	 * @v fragment		Fragment reassembly buffer
+	 * @v iobuf		I/O buffer
+	 * @v hdrlen		Length of non-fragmentable potion of I/O buffer
+	 * @ret is_fragment	Fragment matches this reassembly buffer
+	 */
+	int ( * is_fragment ) ( struct fragment *fragment,
+				struct io_buffer *iobuf, size_t hdrlen );
+	/**
+	 * Get fragment offset
+	 *
+	 * @v iobuf		I/O buffer
+	 * @v hdrlen		Length of non-fragmentable potion of I/O buffer
+	 * @ret offset		Offset
+	 */
+	size_t ( * fragment_offset ) ( struct io_buffer *iobuf, size_t hdrlen );
+	/**
+	 * Check if more fragments exist
+	 *
+	 * @v iobuf		I/O buffer
+	 * @v hdrlen		Length of non-fragmentable potion of I/O buffer
+	 * @ret more_frags	More fragments exist
+	 */
+	int ( * more_fragments ) ( struct io_buffer *iobuf, size_t hdrlen );
+};
+
+extern struct io_buffer *
+fragment_reassemble ( struct fragment_reassembler *fragments,
+		      struct io_buffer *iobuf, size_t *hdrlen );
+
+#endif /* _IPXE_FRAGMENT_H */

src/include/ipxe/ip.h

@@ -70,18 +70,6 @@ struct ipv4_miniroute {
 	struct in_addr gateway;
 };
 
-/* IPv4 fragment reassembly buffer */
-struct ipv4_fragment {
-	/* List of fragment reassembly buffers */
-	struct list_head list;
-	/** Reassembled packet */
-	struct io_buffer *iobuf;
-	/** Current offset */
-	size_t offset;
-	/** Reassembly timer */
-	struct retry_timer timer;
-};
-
 extern struct list_head ipv4_miniroutes;
 
 extern struct net_protocol ipv4_protocol __net_protocol;