tls: rx: factor SW handling out of tls_rx_one_record()

After recent changes the SW side of tls_rx_one_record() can
be nicely encapsulated in its own function. Move the pad handling
as well. This will be useful for ->zc handling in tls_decrypt_device().
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/tls/tls_sw.c

@@ -1409,7 +1409,7 @@ tls_alloc_clrtxt_skb(struct sock *sk, struct sk_buff *skb,
 
 /* Decrypt handlers
  *
- * tls_decrypt_sg() and tls_decrypt_device() are decrypt handlers.
+ * tls_decrypt_sw() and tls_decrypt_device() are decrypt handlers.
  * They must transform the darg in/out argument are as follows:
  *       |          Input            |         Output
  * -------------------------------------------------------------------
@@ -1589,49 +1589,22 @@ static int tls_decrypt_sg(struct sock *sk, struct iov_iter *out_iov,
 }
 
 static int
-tls_decrypt_device(struct sock *sk, struct tls_context *tls_ctx,
-		   struct tls_decrypt_arg *darg)
+tls_decrypt_sw(struct sock *sk, struct tls_context *tls_ctx,
+	       struct msghdr *msg, struct tls_decrypt_arg *darg)
 {
-	struct tls_sw_context_rx *ctx = tls_sw_ctx_rx(tls_ctx);
-	int err;
-
-	if (tls_ctx->rx_conf != TLS_HW)
-		return 0;
-
-	err = tls_device_decrypted(sk, tls_ctx);
-	if (err <= 0)
-		return err;
-
-	darg->zc = false;
-	darg->async = false;
-	darg->skb = tls_strp_msg(ctx);
-	ctx->recv_pkt = NULL;
-	return 1;
-}
-
-static int tls_rx_one_record(struct sock *sk, struct iov_iter *dest,
-			     struct tls_decrypt_arg *darg)
-{
-	struct tls_context *tls_ctx = tls_get_ctx(sk);
 	struct tls_sw_context_rx *ctx = tls_sw_ctx_rx(tls_ctx);
 	struct tls_prot_info *prot = &tls_ctx->prot_info;
 	struct strp_msg *rxm;
 	int pad, err;
 
-	err = tls_decrypt_device(sk, tls_ctx, darg);
-	if (err < 0)
-		return err;
-	if (err)
-		goto decrypt_done;
-
-	err = tls_decrypt_sg(sk, dest, NULL, darg);
+	err = tls_decrypt_sg(sk, &msg->msg_iter, NULL, darg);
 	if (err < 0) {
 		if (err == -EBADMSG)
 			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSDECRYPTERROR);
 		return err;
 	}
-	if (darg->async)
-		goto decrypt_done;
+	/* keep going even for ->async, the code below is TLS 1.3 */
+
 	/* If opportunistic TLS 1.3 ZC failed retry without ZC */
 	if (unlikely(darg->zc && prot->version == TLS_1_3_VERSION &&
 		     darg->tail != TLS_RECORD_TYPE_DATA)) {
@@ -1639,10 +1612,9 @@ static int tls_rx_one_record(struct sock *sk, struct iov_iter *dest,
 		if (!darg->tail)
 			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSRXNOPADVIOL);
 		TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSDECRYPTRETRY);
-		return tls_rx_one_record(sk, dest, darg);
+		return tls_decrypt_sw(sk, tls_ctx, msg, darg);
 	}
 
-decrypt_done:
 	if (darg->skb == ctx->recv_pkt)
 		ctx->recv_pkt = NULL;
 
@@ -1654,6 +1626,55 @@ static int tls_rx_one_record(struct sock *sk, struct iov_iter *dest,
 
 	rxm = strp_msg(darg->skb);
 	rxm->full_len -= pad;
+
+	return 0;
+}
+
+static int
+tls_decrypt_device(struct sock *sk, struct tls_context *tls_ctx,
+		   struct tls_decrypt_arg *darg)
+{
+	struct tls_sw_context_rx *ctx = tls_sw_ctx_rx(tls_ctx);
+	struct tls_prot_info *prot = &tls_ctx->prot_info;
+	struct strp_msg *rxm;
+	int pad, err;
+
+	if (tls_ctx->rx_conf != TLS_HW)
+		return 0;
+
+	err = tls_device_decrypted(sk, tls_ctx);
+	if (err <= 0)
+		return err;
+
+	pad = tls_padding_length(prot, tls_strp_msg(ctx), darg);
+	if (pad < 0)
+		return pad;
+
+	darg->zc = false;
+	darg->async = false;
+	darg->skb = tls_strp_msg(ctx);
+	ctx->recv_pkt = NULL;
+
+	rxm = strp_msg(darg->skb);
+	rxm->full_len -= pad;
+	return 1;
+}
+
+static int tls_rx_one_record(struct sock *sk, struct msghdr *msg,
+			     struct tls_decrypt_arg *darg)
+{
+	struct tls_context *tls_ctx = tls_get_ctx(sk);
+	struct tls_prot_info *prot = &tls_ctx->prot_info;
+	struct strp_msg *rxm;
+	int err;
+
+	err = tls_decrypt_device(sk, tls_ctx, darg);
+	if (!err)
+		err = tls_decrypt_sw(sk, tls_ctx, msg, darg);
+	if (err < 0)
+		return err;
+
+	rxm = strp_msg(darg->skb);
 	rxm->offset += prot->prepend_size;
 	rxm->full_len -= prot->overhead_size;
 	tls_advance_record_sn(sk, prot, &tls_ctx->rx);
@@ -1943,7 +1964,7 @@ int tls_sw_recvmsg(struct sock *sk,
 		else
 			darg.async = false;
 
-		err = tls_rx_one_record(sk, &msg->msg_iter, &darg);
+		err = tls_rx_one_record(sk, msg, &darg);
 		if (err < 0) {
 			tls_err_abort(sk, -EBADMSG);
 			goto recv_end;