diff --git a/include/rxrpc/packet.h b/include/rxrpc/packet.h
new file mode 100644
index 0000000..1447f0a
--- /dev/null
+++ b/include/rxrpc/packet.h
@@ -0,0 +1,127 @@
+/* packet.h: Rx packet layout and definitions
+ *
+ * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifndef _LINUX_RXRPC_PACKET_H
+#define _LINUX_RXRPC_PACKET_H
+
+#include <rxrpc/types.h>
+
+#define RXRPC_IPUDP_SIZE		28
+extern size_t RXRPC_MAX_PACKET_SIZE;
+#define RXRPC_MAX_PACKET_DATA_SIZE	(RXRPC_MAX_PACKET_SIZE - sizeof(struct rxrpc_header))
+#define RXRPC_LOCAL_PACKET_SIZE		RXRPC_MAX_PACKET_SIZE
+#define RXRPC_REMOTE_PACKET_SIZE	(576 - RXRPC_IPUDP_SIZE)
+
+/*****************************************************************************/
+/*
+ * on-the-wire Rx packet header
+ * - all multibyte fields should be in network byte order
+ */
+struct rxrpc_header
+{
+	__be32		epoch;		/* client boot timestamp */
+
+	__be32		cid;		/* connection and channel ID */
+#define RXRPC_MAXCALLS		4			/* max active calls per conn */
+#define RXRPC_CHANNELMASK	(RXRPC_MAXCALLS-1)	/* mask for channel ID */
+#define RXRPC_CIDMASK		(~RXRPC_CHANNELMASK)	/* mask for connection ID */
+#define RXRPC_CIDSHIFT		2			/* shift for connection ID */
+
+	__be32		callNumber;	/* call ID (0 for connection-level packets) */
+#define RXRPC_PROCESS_MAXCALLS	(1<<2)	/* maximum number of active calls per conn (power of 2) */
+
+	__be32		seq;		/* sequence number of pkt in call stream */
+	__be32		serial;		/* serial number of pkt sent to network */
+
+	uint8_t		type;		/* packet type */
+#define RXRPC_PACKET_TYPE_DATA		1	/* data */
+#define RXRPC_PACKET_TYPE_ACK		2	/* ACK */
+#define RXRPC_PACKET_TYPE_BUSY		3	/* call reject */
+#define RXRPC_PACKET_TYPE_ABORT		4	/* call/connection abort */
+#define RXRPC_PACKET_TYPE_ACKALL	5	/* ACK all outstanding packets on call */
+#define RXRPC_PACKET_TYPE_CHALLENGE	6	/* connection security challenge (SRVR->CLNT) */
+#define RXRPC_PACKET_TYPE_RESPONSE	7	/* connection secutity response (CLNT->SRVR) */
+#define RXRPC_PACKET_TYPE_DEBUG		8	/* debug info request */
+#define RXRPC_N_PACKET_TYPES		9	/* number of packet types (incl type 0) */
+
+	uint8_t		flags;		/* packet flags */
+#define RXRPC_CLIENT_INITIATED	0x01		/* signifies a packet generated by a client */
+#define RXRPC_REQUEST_ACK	0x02		/* request an unconditional ACK of this packet */
+#define RXRPC_LAST_PACKET	0x04		/* the last packet from this side for this call */
+#define RXRPC_MORE_PACKETS	0x08		/* more packets to come */
+#define RXRPC_JUMBO_PACKET	0x20		/* [DATA] this is a jumbo packet */
+#define RXRPC_SLOW_START_OK	0x20		/* [ACK] slow start supported */
+
+	uint8_t		userStatus;	/* app-layer defined status */
+	uint8_t		securityIndex;	/* security protocol ID */
+	__be16		_rsvd;		/* reserved (used by kerberos security as cksum) */
+	__be16		serviceId;	/* service ID */
+
+} __attribute__((packed));
+
+#define __rxrpc_header_off(X) offsetof(struct rxrpc_header,X)
+
+extern const char *rxrpc_pkts[];
+
+/*****************************************************************************/
+/*
+ * jumbo packet secondary header
+ * - can be mapped to read header by:
+ *   - new_serial = serial + 1
+ *   - new_seq = seq + 1
+ *   - new_flags = j_flags
+ *   - new__rsvd = j__rsvd
+ *   - duplicating all other fields
+ */
+struct rxrpc_jumbo_header
+{
+	uint8_t		flags;		/* packet flags (as per rxrpc_header) */
+	uint8_t		pad;
+	__be16		_rsvd;		/* reserved (used by kerberos security as cksum) */
+};
+
+#define RXRPC_JUMBO_DATALEN	1412	/* non-terminal jumbo packet data length */
+
+/*****************************************************************************/
+/*
+ * on-the-wire Rx ACK packet data payload
+ * - all multibyte fields should be in network byte order
+ */
+struct rxrpc_ackpacket
+{
+	__be16		bufferSpace;	/* number of packet buffers available */
+	__be16		maxSkew;	/* diff between serno being ACK'd and highest serial no
+					 * received */
+	__be32		firstPacket;	/* sequence no of first ACK'd packet in attached list */
+	__be32		previousPacket;	/* sequence no of previous packet received */
+	__be32		serial;		/* serial no of packet that prompted this ACK */
+
+	uint8_t		reason;		/* reason for ACK */
+#define RXRPC_ACK_REQUESTED		1	/* ACK was requested on packet */
+#define RXRPC_ACK_DUPLICATE		2	/* duplicate packet received */
+#define RXRPC_ACK_OUT_OF_SEQUENCE	3	/* out of sequence packet received */
+#define RXRPC_ACK_EXCEEDS_WINDOW	4	/* packet received beyond end of ACK window */
+#define RXRPC_ACK_NOSPACE		5	/* packet discarded due to lack of buffer space */
+#define RXRPC_ACK_PING			6	/* keep alive ACK */
+#define RXRPC_ACK_PING_RESPONSE		7	/* response to RXRPC_ACK_PING */
+#define RXRPC_ACK_DELAY			8	/* nothing happened since received packet */
+#define RXRPC_ACK_IDLE			9	/* ACK due to fully received ACK window */
+
+	uint8_t		nAcks;		/* number of ACKs */
+#define RXRPC_MAXACKS	255
+
+	uint8_t		acks[0];	/* list of ACK/NAKs */
+#define RXRPC_ACK_TYPE_NACK		0
+#define RXRPC_ACK_TYPE_ACK		1
+
+} __attribute__((packed));
+
+#endif /* _LINUX_RXRPC_PACKET_H */