net/mlx5e: kTLS, Do not send decrypted-marked SKBs via non-accel path

When TCP out-of-order is identified (unexpected tcp seq mismatch), driver
analyzes the packet and decides what handling should it get:
1. go to accelerated path (to be encrypted in HW),
2. go to regular xmit path (send w/o encryption),
3. drop.

Packets marked with skb->decrypted by the TLS stack in the TX flow skips
SW encryption, and rely on the HW offload.
Verify that such packets are never sent un-encrypted on the wire.
Add a WARN to catch such bugs, and prefer dropping the packet in these cases.

Fixes: 46a3ea98 ("net/mlx5e: kTLS, Enhance TX resync flow")
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Boris Pismenny <borisp@mellanox.com>
Reviewed-by: Boris Pismenny <borisp@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_accel/ktls_tx.c

@@ -458,12 +458,18 @@ struct sk_buff *mlx5e_ktls_handle_tx_skb(struct net_device *netdev,
 		enum mlx5e_ktls_sync_retval ret =
 			mlx5e_ktls_tx_handle_ooo(priv_tx, sq, datalen, seq);
 
-		if (likely(ret == MLX5E_KTLS_SYNC_DONE))
+		switch (ret) {
+		case MLX5E_KTLS_SYNC_DONE:
 			*wqe = mlx5e_sq_fetch_wqe(sq, sizeof(**wqe), pi);
-		else if (ret == MLX5E_KTLS_SYNC_FAIL)
-			goto err_out;
-		else /* ret == MLX5E_KTLS_SYNC_SKIP_NO_DATA */
+			break;
+		case MLX5E_KTLS_SYNC_SKIP_NO_DATA:
+			if (likely(!skb->decrypted))
 				goto out;
+			WARN_ON_ONCE(1);
+			/* fall-through */
+		default: /* MLX5E_KTLS_SYNC_FAIL */
+			goto err_out;
+		}
 	}
 
 	priv_tx->expected_seq = seq + datalen;