diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 69e6f4b20bad..a5c0bc917641 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -821,9 +821,11 @@ struct rxrpc_txbuf {
 	rxrpc_serial_t		serial;		/* Last serial number transmitted with */
 	unsigned int		call_debug_id;
 	unsigned int		debug_id;
-	unsigned int		len;		/* Amount of data in buffer */
-	unsigned int		space;		/* Remaining data space */
-	unsigned int		offset;		/* Offset of fill point */
+	unsigned short		len;		/* Amount of data in buffer */
+	unsigned short		space;		/* Remaining data space */
+	unsigned short		offset;		/* Offset of fill point */
+	unsigned short		pkt_len;	/* Size of packet content */
+	unsigned short		alloc_size;	/* Amount of bufferage allocated */
 	unsigned int		flags;
 #define RXRPC_TXBUF_WIRE_FLAGS	0xff		/* The wire protocol flags */
 #define RXRPC_TXBUF_RESENT	0x100		/* Set if has been resent */
diff --git a/net/rxrpc/insecure.c b/net/rxrpc/insecure.c
index 751eb621021d..d665f486be5f 100644
--- a/net/rxrpc/insecure.c
+++ b/net/rxrpc/insecure.c
@@ -24,6 +24,7 @@ static struct rxrpc_txbuf *none_alloc_txbuf(struct rxrpc_call *call, size_t rema
 
 static int none_secure_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 {
+	txb->pkt_len = txb->len;
 	return 0;
 }
 
diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index a91be871ad96..df9af4ad4260 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -383,11 +383,11 @@ static size_t rxrpc_prepare_data_subpacket(struct rxrpc_call *call, struct rxrpc
 	enum rxrpc_req_ack_trace why;
 	struct rxrpc_connection *conn = call->conn;
 	struct kvec *kv = &call->local->kvec[subpkt];
-	size_t len = txb->len;
+	size_t len = txb->pkt_len;
 	bool last, more;
 	u8 flags;
 
-	_enter("%x,{%d}", txb->seq, txb->len);
+	_enter("%x,%zd", txb->seq, len);
 
 	txb->serial = serial;
 
@@ -441,6 +441,7 @@ static size_t rxrpc_prepare_data_subpacket(struct rxrpc_call *call, struct rxrpc
 	whdr->cksum	= txb->cksum;
 	whdr->serviceId	= htons(conn->service_id);
 	kv->iov_base	= whdr;
+	len += sizeof(*whdr);
 	// TODO: Convert into a jumbo header for tail subpackets
 
 	trace_rxrpc_tx_data(call, txb->seq, txb->serial, flags, false);
@@ -509,7 +510,7 @@ static int rxrpc_send_data_packet(struct rxrpc_call *call, struct rxrpc_txbuf *t
 	size_t len;
 	int ret;
 
-	_enter("%x,{%d}", txb->seq, txb->len);
+	_enter("%x,{%d}", txb->seq, txb->pkt_len);
 
 	len = rxrpc_prepare_data_packet(call, txb);
 
diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c
index e3194d73dd84..755897fab626 100644
--- a/net/rxrpc/rxkad.c
+++ b/net/rxrpc/rxkad.c
@@ -148,14 +148,14 @@ static int rxkad_init_connection_security(struct rxrpc_connection *conn,
 static struct rxrpc_txbuf *rxkad_alloc_txbuf(struct rxrpc_call *call, size_t remain, gfp_t gfp)
 {
 	struct rxrpc_txbuf *txb;
-	size_t shdr, space;
+	size_t shdr, alloc, limit, part;
 
 	remain = umin(remain, 65535 - sizeof(struct rxrpc_wire_header));
 
 	switch (call->conn->security_level) {
 	default:
-		space = umin(remain, RXRPC_JUMBO_DATALEN);
-		return rxrpc_alloc_data_txbuf(call, space, 1, gfp);
+		alloc = umin(remain, RXRPC_JUMBO_DATALEN);
+		return rxrpc_alloc_data_txbuf(call, alloc, 1, gfp);
 	case RXRPC_SECURITY_AUTH:
 		shdr = sizeof(struct rxkad_level1_hdr);
 		break;
@@ -164,15 +164,21 @@ static struct rxrpc_txbuf *rxkad_alloc_txbuf(struct rxrpc_call *call, size_t rem
 		break;
 	}
 
-	space = umin(round_down(RXRPC_JUMBO_DATALEN, RXKAD_ALIGN), remain + shdr);
-	space = round_up(space, RXKAD_ALIGN);
+	limit = round_down(RXRPC_JUMBO_DATALEN, RXKAD_ALIGN) - shdr;
+	if (remain < limit) {
+		part = remain;
+		alloc = round_up(shdr + part, RXKAD_ALIGN);
+	} else {
+		part = limit;
+		alloc = RXRPC_JUMBO_DATALEN;
+	}
 
-	txb = rxrpc_alloc_data_txbuf(call, space, RXKAD_ALIGN, gfp);
+	txb = rxrpc_alloc_data_txbuf(call, alloc, RXKAD_ALIGN, gfp);
 	if (!txb)
 		return NULL;
 
 	txb->offset += shdr;
-	txb->space -= shdr;
+	txb->space = part;
 	return txb;
 }
 
@@ -263,13 +269,13 @@ static int rxkad_secure_packet_auth(const struct rxrpc_call *call,
 	check = txb->seq ^ call->call_id;
 	hdr->data_size = htonl((u32)check << 16 | txb->len);
 
-	txb->len += sizeof(struct rxkad_level1_hdr);
-	pad = txb->len;
+	txb->pkt_len = sizeof(struct rxkad_level1_hdr) + txb->len;
+	pad = txb->pkt_len;
 	pad = RXKAD_ALIGN - pad;
 	pad &= RXKAD_ALIGN - 1;
 	if (pad) {
 		memset(txb->kvec[0].iov_base + txb->offset, 0, pad);
-		txb->len += pad;
+		txb->pkt_len += pad;
 	}
 
 	/* start the encryption afresh */
@@ -298,7 +304,7 @@ static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
 	struct rxkad_level2_hdr *rxkhdr = (void *)(whdr + 1);
 	struct rxrpc_crypt iv;
 	struct scatterlist sg;
-	size_t pad;
+	size_t content, pad;
 	u16 check;
 	int ret;
 
@@ -309,23 +315,20 @@ static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
 	rxkhdr->data_size = htonl(txb->len | (u32)check << 16);
 	rxkhdr->checksum = 0;
 
-	txb->len += sizeof(struct rxkad_level2_hdr);
-	pad = txb->len;
-	pad = RXKAD_ALIGN - pad;
-	pad &= RXKAD_ALIGN - 1;
-	if (pad) {
+	content = sizeof(struct rxkad_level2_hdr) + txb->len;
+	txb->pkt_len = round_up(content, RXKAD_ALIGN);
+	pad = txb->pkt_len - content;
+	if (pad)
 		memset(txb->kvec[0].iov_base + txb->offset, 0, pad);
-		txb->len += pad;
-	}
 
 	/* encrypt from the session key */
 	token = call->conn->key->payload.data[0];
 	memcpy(&iv, token->kad->session_key, sizeof(iv));
 
-	sg_init_one(&sg, rxkhdr, txb->len);
+	sg_init_one(&sg, rxkhdr, txb->pkt_len);
 	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, txb->len, iv.x);
+	skcipher_request_set_crypt(req, &sg, &sg, txb->pkt_len, iv.x);
 	ret = crypto_skcipher_encrypt(req);
 	skcipher_request_zero(req);
 	return ret;
@@ -384,6 +387,7 @@ static int rxkad_secure_packet(struct rxrpc_call *call, struct rxrpc_txbuf *txb)
 
 	switch (call->conn->security_level) {
 	case RXRPC_SECURITY_PLAIN:
+		txb->pkt_len = txb->len;
 		ret = 0;
 		break;
 	case RXRPC_SECURITY_AUTH:
diff --git a/net/rxrpc/sendmsg.c b/net/rxrpc/sendmsg.c
index 546abb463c3f..786c1fb1369a 100644
--- a/net/rxrpc/sendmsg.c
+++ b/net/rxrpc/sendmsg.c
@@ -391,7 +391,6 @@ static int rxrpc_send_data(struct rxrpc_sock *rx,
 				goto out;
 
 			txb->kvec[0].iov_len += txb->len;
-			txb->len = txb->kvec[0].iov_len;
 			rxrpc_queue_packet(rx, call, txb, notify_end_tx);
 			txb = NULL;
 		}
diff --git a/net/rxrpc/txbuf.c b/net/rxrpc/txbuf.c
index 2a4291617d40..8b7c854ed3d7 100644
--- a/net/rxrpc/txbuf.c
+++ b/net/rxrpc/txbuf.c
@@ -24,7 +24,7 @@ struct rxrpc_txbuf *rxrpc_alloc_data_txbuf(struct rxrpc_call *call, size_t data_
 	size_t total, hoff;
 	void *buf;
 
-	txb = kmalloc(sizeof(*txb), gfp);
+	txb = kzalloc(sizeof(*txb), gfp);
 	if (!txb)
 		return NULL;
 
@@ -49,14 +49,11 @@ struct rxrpc_txbuf *rxrpc_alloc_data_txbuf(struct rxrpc_call *call, size_t data_
 	txb->last_sent		= KTIME_MIN;
 	txb->call_debug_id	= call->debug_id;
 	txb->debug_id		= atomic_inc_return(&rxrpc_txbuf_debug_ids);
+	txb->alloc_size		= data_size;
 	txb->space		= data_size;
-	txb->len		= 0;
 	txb->offset		= sizeof(*whdr);
 	txb->flags		= call->conn->out_clientflag;
-	txb->ack_why		= 0;
 	txb->seq		= call->tx_prepared + 1;
-	txb->serial		= 0;
-	txb->cksum		= 0;
 	txb->nr_kvec		= 1;
 	txb->kvec[0].iov_base	= whdr;
 	txb->kvec[0].iov_len	= sizeof(*whdr);
