net/mlx5e: kTLS, Fix corner-case checks in TX resync flow

There are the following cases:

1. Packet ends before start marker: bypass offload.
2. Packet starts before start marker and ends after it: drop,
   not supported, breaks contract with kernel.
3. packet ends before tls record info starts: drop,
   this packet was already acknowledged and its record info
   was released.

Add the above as comment in code.

Mind possible wraparounds of the TCP seq, replace the simple comparison
with a call to the TCP before() method.

In addition, remove logic that handles negative sync_len values,
as it became impossible.

Fixes: d2ead1f3 ("net/mlx5e: Add kTLS TX HW offload support")
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

@@ -180,7 +180,7 @@ mlx5e_ktls_tx_post_param_wqes(struct mlx5e_txqsq *sq,
 
 struct tx_sync_info {
 	u64 rcd_sn;
-	s32 sync_len;
+	u32 sync_len;
 	int nr_frags;
 	skb_frag_t frags[MAX_SKB_FRAGS];
 };
@@ -193,13 +193,14 @@ enum mlx5e_ktls_sync_retval {
 
 static enum mlx5e_ktls_sync_retval
 tx_sync_info_get(struct mlx5e_ktls_offload_context_tx *priv_tx,
-		 u32 tcp_seq, struct tx_sync_info *info)
+		 u32 tcp_seq, int datalen, struct tx_sync_info *info)
 {
 	struct tls_offload_context_tx *tx_ctx = priv_tx->tx_ctx;
 	enum mlx5e_ktls_sync_retval ret = MLX5E_KTLS_SYNC_DONE;
 	struct tls_record_info *record;
 	int remaining, i = 0;
 	unsigned long flags;
+	bool ends_before;
 
 	spin_lock_irqsave(&tx_ctx->lock, flags);
 	record = tls_get_record(tx_ctx, tcp_seq, &info->rcd_sn);
@@ -209,9 +210,21 @@ tx_sync_info_get(struct mlx5e_ktls_offload_context_tx *priv_tx,
 		goto out;
 	}
 
-	if (unlikely(tcp_seq < tls_record_start_seq(record))) {
-		ret = tls_record_is_start_marker(record) ?
-			MLX5E_KTLS_SYNC_SKIP_NO_DATA : MLX5E_KTLS_SYNC_FAIL;
+	/* There are the following cases:
+	 * 1. packet ends before start marker: bypass offload.
+	 * 2. packet starts before start marker and ends after it: drop,
+	 *    not supported, breaks contract with kernel.
+	 * 3. packet ends before tls record info starts: drop,
+	 *    this packet was already acknowledged and its record info
+	 *    was released.
+	 */
+	ends_before = before(tcp_seq + datalen, tls_record_start_seq(record));
+
+	if (unlikely(tls_record_is_start_marker(record))) {
+		ret = ends_before ? MLX5E_KTLS_SYNC_SKIP_NO_DATA : MLX5E_KTLS_SYNC_FAIL;
+		goto out;
+	} else if (ends_before) {
+		ret = MLX5E_KTLS_SYNC_FAIL;
 		goto out;
 	}
 
@@ -337,7 +350,7 @@ mlx5e_ktls_tx_handle_ooo(struct mlx5e_ktls_offload_context_tx *priv_tx,
 	u8 num_wqebbs;
 	int i = 0;
 
-	ret = tx_sync_info_get(priv_tx, seq, &info);
+	ret = tx_sync_info_get(priv_tx, seq, datalen, &info);
 	if (unlikely(ret != MLX5E_KTLS_SYNC_DONE)) {
 		if (ret == MLX5E_KTLS_SYNC_SKIP_NO_DATA) {
 			stats->tls_skip_no_sync_data++;
@@ -351,14 +364,6 @@ mlx5e_ktls_tx_handle_ooo(struct mlx5e_ktls_offload_context_tx *priv_tx,
 		goto err_out;
 	}
 
-	if (unlikely(info.sync_len < 0)) {
-		if (likely(datalen <= -info.sync_len))
-			return MLX5E_KTLS_SYNC_DONE;
-
-		stats->tls_drop_bypass_req++;
-		goto err_out;
-	}
-
 	stats->tls_ooo++;
 
 	tx_post_resync_params(sq, priv_tx, info.rcd_sn);