rxrpc: Clone received jumbo subpackets and queue separately

Split up received jumbo packets into separate skbuffs by cloning the
original skbuff for each subpacket and setting the offset and length of the
data in that subpacket in the skbuff's private data.  The subpackets are
then placed on the recvmsg queue separately.  The security class then gets
to revise the offset and length to remove its metadata.

If we fail to clone a packet, we just drop it and let the peer resend it.
The original packet gets used for the final subpacket.

This should make it easier to handle parallel decryption of the subpackets.
It also simplifies the handling of lost or misordered packets in the
queuing/buffering loop as the possibility of overlapping jumbo packets no
longer needs to be considered.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org

include/trace/events/rxrpc.h

@@ -18,6 +18,7 @@
  */
 #define rxrpc_skb_traces \
 	EM(rxrpc_skb_cleaned,			"CLN") \
+	EM(rxrpc_skb_cloned_jumbo,		"CLJ") \
 	EM(rxrpc_skb_freed,			"FRE") \
 	EM(rxrpc_skb_got,			"GOT") \
 	EM(rxrpc_skb_lost,			"*L*") \
@@ -630,16 +631,15 @@ TRACE_EVENT(rxrpc_transmit,
 
 TRACE_EVENT(rxrpc_rx_data,
 	    TP_PROTO(unsigned int call, rxrpc_seq_t seq,
-		     rxrpc_serial_t serial, u8 flags, u8 anno),
+		     rxrpc_serial_t serial, u8 flags),
 
-	    TP_ARGS(call, seq, serial, flags, anno),
+	    TP_ARGS(call, seq, serial, flags),
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,		call		)
 		    __field(rxrpc_seq_t,		seq		)
 		    __field(rxrpc_serial_t,		serial		)
 		    __field(u8,				flags		)
-		    __field(u8,				anno		)
 			     ),
 
 	    TP_fast_assign(
@@ -647,15 +647,13 @@ TRACE_EVENT(rxrpc_rx_data,
 		    __entry->seq = seq;
 		    __entry->serial = serial;
 		    __entry->flags = flags;
-		    __entry->anno = anno;
 			   ),
 
-	    TP_printk("c=%08x DATA %08x q=%08x fl=%02x a=%02x",
+	    TP_printk("c=%08x DATA %08x q=%08x fl=%02x",
 		      __entry->call,
 		      __entry->serial,
 		      __entry->seq,
-		      __entry->flags,
-		      __entry->anno)
+		      __entry->flags)
 	    );
 
 TRACE_EVENT(rxrpc_rx_ack,

net/rxrpc/ar-internal.h

@@ -195,17 +195,12 @@ struct rxrpc_host_header {
  * - max 48 bytes (struct sk_buff::cb)
  */
 struct rxrpc_skb_priv {
-	atomic_t	nr_ring_pins;		/* Number of rxtx ring pins */
-	u8		nr_subpackets;		/* Number of subpackets */
+	u16		remain;
+	u16		offset;		/* Offset of data */
+	u16		len;		/* Length of data */
 	u8		rx_flags;	/* Received packet flags */
-#define RXRPC_SKB_INCL_LAST	0x01		/* - Includes last packet */
-	union {
-		int		remain;		/* amount of space remaining for next write */
-
-		/* List of requested ACKs on subpackets */
-		unsigned long	rx_req_ack[(RXRPC_MAX_NR_JUMBO + BITS_PER_LONG - 1) /
-					   BITS_PER_LONG];
-	};
+	u8		flags;
+#define RXRPC_RX_VERIFIED	0x01
 
 	struct rxrpc_host_header hdr;	/* RxRPC packet header from this packet */
 };
@@ -252,16 +247,11 @@ struct rxrpc_security {
 	int (*secure_packet)(struct rxrpc_call *, struct sk_buff *, size_t);
 
 	/* verify the security on a received packet */
-	int (*verify_packet)(struct rxrpc_call *, struct sk_buff *,
-			     unsigned int, unsigned int, rxrpc_seq_t, u16);
+	int (*verify_packet)(struct rxrpc_call *, struct sk_buff *);
 
 	/* Free crypto request on a call */
 	void (*free_call_crypto)(struct rxrpc_call *);
 
-	/* Locate the data in a received packet that has been verified. */
-	void (*locate_data)(struct rxrpc_call *, struct sk_buff *,
-			    unsigned int *, unsigned int *);
-
 	/* issue a challenge */
 	int (*issue_challenge)(struct rxrpc_connection *);
 
@@ -628,7 +618,6 @@ struct rxrpc_call {
 	int			debug_id;	/* debug ID for printks */
 	unsigned short		rx_pkt_offset;	/* Current recvmsg packet offset */
 	unsigned short		rx_pkt_len;	/* Current recvmsg packet len */
-	bool			rx_pkt_last;	/* Current recvmsg packet is last */
 
 	/* Rx/Tx circular buffer, depending on phase.
 	 *
@@ -652,8 +641,6 @@ struct rxrpc_call {
 #define RXRPC_TX_ANNO_LAST	0x04
 #define RXRPC_TX_ANNO_RESENT	0x08
 
-#define RXRPC_RX_ANNO_SUBPACKET	0x3f		/* Subpacket number in jumbogram */
-#define RXRPC_RX_ANNO_VERIFIED	0x80		/* Set if verified and decrypted */
 	rxrpc_seq_t		tx_hard_ack;	/* Dead slot in buffer; the first transmitted but
 						 * not hard-ACK'd packet follows this.
 						 */
@@ -681,7 +668,6 @@ struct rxrpc_call {
 	rxrpc_serial_t		rx_serial;	/* Highest serial received for this call */
 	u8			rx_winsize;	/* Size of Rx window */
 	u8			tx_winsize;	/* Maximum size of Tx window */
-	u8			nr_jumbo_bad;	/* Number of jumbo dups/exceeds-windows */
 
 	spinlock_t		input_lock;	/* Lock for packet input to this call */
 

net/rxrpc/insecure.c

@@ -31,10 +31,11 @@ static int none_secure_packet(struct rxrpc_call *call, struct sk_buff *skb,
 	return 0;
 }
 
-static int none_verify_packet(struct rxrpc_call *call, struct sk_buff *skb,
-			      unsigned int offset, unsigned int len,
-			      rxrpc_seq_t seq, u16 expected_cksum)
+static int none_verify_packet(struct rxrpc_call *call, struct sk_buff *skb)
 {
+	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
+
+	sp->flags |= RXRPC_RX_VERIFIED;
 	return 0;
 }
 
@@ -42,11 +43,6 @@ static void none_free_call_crypto(struct rxrpc_call *call)
 {
 }
 
-static void none_locate_data(struct rxrpc_call *call, struct sk_buff *skb,
-			     unsigned int *_offset, unsigned int *_len)
-{
-}
-
 static int none_respond_to_challenge(struct rxrpc_connection *conn,
 				     struct sk_buff *skb,
 				     u32 *_abort_code)
@@ -95,7 +91,6 @@ const struct rxrpc_security rxrpc_no_security = {
 	.how_much_data			= none_how_much_data,
 	.secure_packet			= none_secure_packet,
 	.verify_packet			= none_verify_packet,
-	.locate_data			= none_locate_data,
 	.respond_to_challenge		= none_respond_to_challenge,
 	.verify_response		= none_verify_response,
 	.clear				= none_clear,

net/rxrpc/output.c

@@ -121,7 +121,7 @@ static size_t rxrpc_fill_out_ack(struct rxrpc_connection *conn,
 
 	mtu = conn->params.peer->if_mtu;
 	mtu -= conn->params.peer->hdrsize;
-	jmax = (call->nr_jumbo_bad > 3) ? 1 : rxrpc_rx_jumbo_max;
+	jmax = rxrpc_rx_jumbo_max;
 	ackinfo.rxMTU		= htonl(rxrpc_rx_mtu);
 	ackinfo.maxMTU		= htonl(mtu);
 	ackinfo.rwind		= htonl(call->rx_winsize);

net/rxrpc/protocol.h

@@ -84,7 +84,7 @@ struct rxrpc_jumbo_header {
 		__be16	_rsvd;		/* reserved */
 		__be16	cksum;		/* kerberos security checksum */
 	};
-};
+} __packed;
 
 #define RXRPC_JUMBO_DATALEN	1412	/* non-terminal jumbo packet data length */
 #define RXRPC_JUMBO_SUBPKTLEN	(RXRPC_JUMBO_DATALEN + sizeof(struct rxrpc_jumbo_header))

net/rxrpc/recvmsg.c

@@ -222,7 +222,6 @@ static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
 	rxrpc_serial_t serial;
 	rxrpc_seq_t hard_ack, top;
 	bool last = false;
-	u8 subpacket;
 	int ix;
 
 	_enter("%d", call->debug_id);
@@ -237,11 +236,9 @@ static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
 	rxrpc_see_skb(skb, rxrpc_skb_rotated);
 	sp = rxrpc_skb(skb);
 
-	subpacket = call->rxtx_annotations[ix] & RXRPC_RX_ANNO_SUBPACKET;
-	serial = sp->hdr.serial + subpacket;
+	serial = sp->hdr.serial;
 
-	if (subpacket == sp->nr_subpackets - 1 &&
-	    sp->rx_flags & RXRPC_SKB_INCL_LAST)
+	if (sp->hdr.flags & RXRPC_LAST_PACKET)
 		last = true;
 
 	call->rxtx_buffer[ix] = NULL;
@@ -266,80 +263,15 @@ static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
 }
 
 /*
- * Decrypt and verify a (sub)packet.  The packet's length may be changed due to
- * padding, but if this is the case, the packet length will be resident in the
- * socket buffer.  Note that we can't modify the master skb info as the skb may
- * be the home to multiple subpackets.
- */
-static int rxrpc_verify_packet(struct rxrpc_call *call, struct sk_buff *skb,
-			       u8 annotation,
-			       unsigned int offset, unsigned int len)
-{
-	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
-	rxrpc_seq_t seq = sp->hdr.seq;
-	u16 cksum = sp->hdr.cksum;
-	u8 subpacket = annotation & RXRPC_RX_ANNO_SUBPACKET;
-
-	_enter("");
-
-	/* For all but the head jumbo subpacket, the security checksum is in a
-	 * jumbo header immediately prior to the data.
-	 */
-	if (subpacket > 0) {
-		__be16 tmp;
-		if (skb_copy_bits(skb, offset - 2, &tmp, 2) < 0)
-			BUG();
-		cksum = ntohs(tmp);
-		seq += subpacket;
-	}
-
-	return call->security->verify_packet(call, skb, offset, len,
-					     seq, cksum);
-}
-
-/*
- * Locate the data within a packet.  This is complicated by:
- *
- * (1) An skb may contain a jumbo packet - so we have to find the appropriate
- *     subpacket.
- *
- * (2) The (sub)packets may be encrypted and, if so, the encrypted portion
- *     contains an extra header which includes the true length of the data,
- *     excluding any encrypted padding.
+ * Decrypt and verify a DATA packet.
  */
-static int rxrpc_locate_data(struct rxrpc_call *call, struct sk_buff *skb,
-			     u8 *_annotation,
-			     unsigned int *_offset, unsigned int *_len,
-			     bool *_last)
+static int rxrpc_verify_data(struct rxrpc_call *call, struct sk_buff *skb)
 {
 	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
-	unsigned int offset = sizeof(struct rxrpc_wire_header);
-	unsigned int len;
-	bool last = false;
-	int ret;
-	u8 annotation = *_annotation;
-	u8 subpacket = annotation & RXRPC_RX_ANNO_SUBPACKET;
-
-	/* Locate the subpacket */
-	offset += subpacket * RXRPC_JUMBO_SUBPKTLEN;
-	len = skb->len - offset;
-	if (subpacket < sp->nr_subpackets - 1)
-		len = RXRPC_JUMBO_DATALEN;
-	else if (sp->rx_flags & RXRPC_SKB_INCL_LAST)
-		last = true;
-
-	if (!(annotation & RXRPC_RX_ANNO_VERIFIED)) {
-		ret = rxrpc_verify_packet(call, skb, annotation, offset, len);
-		if (ret < 0)
-			return ret;
-		*_annotation |= RXRPC_RX_ANNO_VERIFIED;
-	}
 
-	*_offset = offset;
-	*_len = len;
-	*_last = last;
-	call->security->locate_data(call, skb, _offset, _len);
+	if (sp->flags & RXRPC_RX_VERIFIED)
 		return 0;
+	return call->security->verify_packet(call, skb);
 }
 
 /*
@@ -356,13 +288,11 @@ static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call,
 	rxrpc_serial_t serial;
 	rxrpc_seq_t hard_ack, top, seq;
 	size_t remain;
-	bool rx_pkt_last;
 	unsigned int rx_pkt_offset, rx_pkt_len;
 	int ix, copy, ret = -EAGAIN, ret2;
 
 	rx_pkt_offset = call->rx_pkt_offset;
 	rx_pkt_len = call->rx_pkt_len;
-	rx_pkt_last = call->rx_pkt_last;
 
 	if (call->state >= RXRPC_CALL_SERVER_ACK_REQUEST) {
 		seq = call->rx_hard_ack;
@@ -391,7 +321,6 @@ static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call,
 
 		if (!(flags & MSG_PEEK)) {
 			serial = sp->hdr.serial;
-			serial += call->rxtx_annotations[ix] & RXRPC_RX_ANNO_SUBPACKET;
 			trace_rxrpc_receive(call, rxrpc_receive_front,
 					    serial, seq);
 		}
@@ -400,10 +329,9 @@ static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call,
 			sock_recv_timestamp(msg, sock->sk, skb);
 
 		if (rx_pkt_offset == 0) {
-			ret2 = rxrpc_locate_data(call, skb,
-						 &call->rxtx_annotations[ix],
-						 &rx_pkt_offset, &rx_pkt_len,
-						 &rx_pkt_last);
+			ret2 = rxrpc_verify_data(call, skb);
+			rx_pkt_offset = sp->offset;
+			rx_pkt_len = sp->len;
 			trace_rxrpc_recvdata(call, rxrpc_recvmsg_next, seq,
 					     rx_pkt_offset, rx_pkt_len, ret2);
 			if (ret2 < 0) {
@@ -443,16 +371,13 @@ static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call,
 		}
 
 		/* The whole packet has been transferred. */
-		if (!(flags & MSG_PEEK))
-			rxrpc_rotate_rx_window(call);
+		if (sp->hdr.flags & RXRPC_LAST_PACKET)
+			ret = 1;
 		rx_pkt_offset = 0;
 		rx_pkt_len = 0;
 
-		if (rx_pkt_last) {
-			ASSERTCMP(seq, ==, READ_ONCE(call->rx_top));
-			ret = 1;
-			goto out;
-		}
+		if (!(flags & MSG_PEEK))
+			rxrpc_rotate_rx_window(call);
 
 		seq++;
 	}
@@ -461,7 +386,6 @@ static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call,
 	if (!(flags & MSG_PEEK)) {
 		call->rx_pkt_offset = rx_pkt_offset;
 		call->rx_pkt_len = rx_pkt_len;
-		call->rx_pkt_last = rx_pkt_last;
 	}
 done:
 	trace_rxrpc_recvdata(call, rxrpc_recvmsg_data_return, seq,

net/rxrpc/rxkad.c

@@ -439,11 +439,11 @@ static int rxkad_secure_packet(struct rxrpc_call *call,
  * decrypt partial encryption on a packet (level 1 security)
  */
 static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
-				 unsigned int offset, unsigned int len,
 				 rxrpc_seq_t seq,
 				 struct skcipher_request *req)
 {
 	struct rxkad_level1_hdr sechdr;
+	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	struct rxrpc_crypt iv;
 	struct scatterlist sg[16];
 	bool aborted;
@@ -453,7 +453,7 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
 
 	_enter("");
 
-	if (len < 8) {
+	if (sp->len < 8) {
 		aborted = rxrpc_abort_eproto(call, skb, "rxkad_1_hdr", "V1H",
 					     RXKADSEALEDINCON);
 		goto protocol_error;
@@ -463,7 +463,7 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
 	 * directly into the target buffer.
 	 */
 	sg_init_table(sg, ARRAY_SIZE(sg));
-	ret = skb_to_sgvec(skb, sg, offset, 8);
+	ret = skb_to_sgvec(skb, sg, sp->offset, 8);
 	if (unlikely(ret < 0))
 		return ret;
 
@@ -477,12 +477,13 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
 	skcipher_request_zero(req);
 
 	/* Extract the decrypted packet length */
-	if (skb_copy_bits(skb, offset, &sechdr, sizeof(sechdr)) < 0) {
+	if (skb_copy_bits(skb, sp->offset, &sechdr, sizeof(sechdr)) < 0) {
 		aborted = rxrpc_abort_eproto(call, skb, "rxkad_1_len", "XV1",
 					     RXKADDATALEN);
 		goto protocol_error;
 	}
-	len -= sizeof(sechdr);
+	sp->offset += sizeof(sechdr);
+	sp->len    -= sizeof(sechdr);
 
 	buf = ntohl(sechdr.data_size);
 	data_size = buf & 0xffff;
@@ -496,11 +497,12 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
 		goto protocol_error;
 	}
 
-	if (data_size > len) {
+	if (data_size > sp->len) {
 		aborted = rxrpc_abort_eproto(call, skb, "rxkad_1_datalen", "V1L",
 					     RXKADDATALEN);
 		goto protocol_error;
 	}
+	sp->len = data_size;
 
 	_leave(" = 0 [dlen=%x]", data_size);
 	return 0;
@@ -515,12 +517,12 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
  * wholly decrypt a packet (level 2 security)
  */
 static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
-				 unsigned int offset, unsigned int len,
 				 rxrpc_seq_t seq,
 				 struct skcipher_request *req)
 {
 	const struct rxrpc_key_token *token;
 	struct rxkad_level2_hdr sechdr;
+	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	struct rxrpc_crypt iv;
 	struct scatterlist _sg[4], *sg;
 	bool aborted;
@@ -528,9 +530,9 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
 	u16 check;
 	int nsg, ret;
 
-	_enter(",{%d}", skb->len);
+	_enter(",{%d}", sp->len);
 
-	if (len < 8) {
+	if (sp->len < 8) {
 		aborted = rxrpc_abort_eproto(call, skb, "rxkad_2_hdr", "V2H",
 					     RXKADSEALEDINCON);
 		goto protocol_error;
@@ -550,7 +552,7 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
 	}
 
 	sg_init_table(sg, nsg);
-	ret = skb_to_sgvec(skb, sg, offset, len);
+	ret = skb_to_sgvec(skb, sg, sp->offset, sp->len);
 	if (unlikely(ret < 0)) {
 		if (sg != _sg)
 			kfree(sg);
@@ -563,19 +565,20 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
 
 	skcipher_request_set_sync_tfm(req, call->conn->rxkad.cipher);
 	skcipher_request_set_callback(req, 0, NULL, NULL);
-	skcipher_request_set_crypt(req, sg, sg, len, iv.x);
+	skcipher_request_set_crypt(req, sg, sg, sp->len, iv.x);
 	crypto_skcipher_decrypt(req);
 	skcipher_request_zero(req);
 	if (sg != _sg)
 		kfree(sg);
 
 	/* Extract the decrypted packet length */
-	if (skb_copy_bits(skb, offset, &sechdr, sizeof(sechdr)) < 0) {
+	if (skb_copy_bits(skb, sp->offset, &sechdr, sizeof(sechdr)) < 0) {
 		aborted = rxrpc_abort_eproto(call, skb, "rxkad_2_len", "XV2",
 					     RXKADDATALEN);
 		goto protocol_error;
 	}
-	len -= sizeof(sechdr);
+	sp->offset += sizeof(sechdr);
+	sp->len    -= sizeof(sechdr);
 
 	buf = ntohl(sechdr.data_size);
 	data_size = buf & 0xffff;
@@ -589,12 +592,13 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
 		goto protocol_error;
 	}
 
-	if (data_size > len) {
+	if (data_size > sp->len) {
 		aborted = rxrpc_abort_eproto(call, skb, "rxkad_2_datalen", "V2L",
 					     RXKADDATALEN);
 		goto protocol_error;
 	}
 
+	sp->len = data_size;
 	_leave(" = 0 [dlen=%x]", data_size);
 	return 0;
 
@@ -609,16 +613,15 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
 }
 
 /*
- * Verify the security on a received packet or subpacket (if part of a
- * jumbo packet).
+ * Verify the security on a received packet and the subpackets therein.
  */
-static int rxkad_verify_packet(struct rxrpc_call *call, struct sk_buff *skb,
-			       unsigned int offset, unsigned int len,
-			       rxrpc_seq_t seq, u16 expected_cksum)
+static int rxkad_verify_packet(struct rxrpc_call *call, struct sk_buff *skb)
 {
+	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 	struct skcipher_request	*req;
 	struct rxrpc_crypt iv;
 	struct scatterlist sg;
+	rxrpc_seq_t seq = sp->hdr.seq;
 	bool aborted;
 	u16 cksum;
 	u32 x, y;
@@ -654,7 +657,7 @@ static int rxkad_verify_packet(struct rxrpc_call *call, struct sk_buff *skb,
 	if (cksum == 0)
 		cksum = 1; /* zero checksums are not permitted */
 
-	if (cksum != expected_cksum) {
+	if (cksum != sp->hdr.cksum) {
 		aborted = rxrpc_abort_eproto(call, skb, "rxkad_csum", "VCK",
 					     RXKADSEALEDINCON);
 		goto protocol_error;
@@ -664,9 +667,9 @@ static int rxkad_verify_packet(struct rxrpc_call *call, struct sk_buff *skb,
 	case RXRPC_SECURITY_PLAIN:
 		return 0;
 	case RXRPC_SECURITY_AUTH:
-		return rxkad_verify_packet_1(call, skb, offset, len, seq, req);
+		return rxkad_verify_packet_1(call, skb, seq, req);
 	case RXRPC_SECURITY_ENCRYPT:
-		return rxkad_verify_packet_2(call, skb, offset, len, seq, req);
+		return rxkad_verify_packet_2(call, skb, seq, req);
 	default:
 		return -ENOANO;
 	}
@@ -677,52 +680,6 @@ static int rxkad_verify_packet(struct rxrpc_call *call, struct sk_buff *skb,
 	return -EPROTO;
 }
 
-/*
- * Locate the data contained in a packet that was partially encrypted.
- */
-static void rxkad_locate_data_1(struct rxrpc_call *call, struct sk_buff *skb,
-				unsigned int *_offset, unsigned int *_len)
-{
-	struct rxkad_level1_hdr sechdr;
-
-	if (skb_copy_bits(skb, *_offset, &sechdr, sizeof(sechdr)) < 0)
-		BUG();
-	*_offset += sizeof(sechdr);
-	*_len = ntohl(sechdr.data_size) & 0xffff;
-}
-
-/*
- * Locate the data contained in a packet that was completely encrypted.
- */
-static void rxkad_locate_data_2(struct rxrpc_call *call, struct sk_buff *skb,
-				unsigned int *_offset, unsigned int *_len)
-{
-	struct rxkad_level2_hdr sechdr;
-
-	if (skb_copy_bits(skb, *_offset, &sechdr, sizeof(sechdr)) < 0)
-		BUG();
-	*_offset += sizeof(sechdr);
-	*_len = ntohl(sechdr.data_size) & 0xffff;
-}
-
-/*
- * Locate the data contained in an already decrypted packet.
- */
-static void rxkad_locate_data(struct rxrpc_call *call, struct sk_buff *skb,
-			      unsigned int *_offset, unsigned int *_len)
-{
-	switch (call->conn->params.security_level) {
-	case RXRPC_SECURITY_AUTH:
-		rxkad_locate_data_1(call, skb, _offset, _len);
-		return;
-	case RXRPC_SECURITY_ENCRYPT:
-		rxkad_locate_data_2(call, skb, _offset, _len);
-		return;
-	default:
-		return;
-	}
-}
-
 /*
  * issue a challenge
  */
@@ -1397,7 +1354,6 @@ const struct rxrpc_security rxkad = {
 	.secure_packet			= rxkad_secure_packet,
 	.verify_packet			= rxkad_verify_packet,
 	.free_call_crypto		= rxkad_free_call_crypto,
-	.locate_data			= rxkad_locate_data,
 	.issue_challenge		= rxkad_issue_challenge,
 	.respond_to_challenge		= rxkad_respond_to_challenge,
 	.verify_response		= rxkad_verify_response,