[PATCH 2/2] net: ethernet: oa_tc6: Improvement in buffer overflow handling

[Selvamani Rajagopal via B4 Relay]

From: Selvamani Rajagopal <Selvamani.Rajagopal@xxxxxxxxxx>

When oversubscribed traffic causes lot of buffer overflow errors,
probably due to loss of data chunks, driver fails to find a
data chunk with end_valid bit set, before it runs out of sk buffer
space. As a result, assert is seen during skb_put.

Now check is made if tail + len > end, driver abandons the current
data and starts look for a data chunk with start_valid bit,
that is a new frame.

Fixes: d70a0d8f2f2d ("net: ethernet: oa_tc6: implement receive path to receive rx ethernet frames")
Signed-off-by: Selvamani Rajagopal <Selvamani.Rajagopal@xxxxxxxxxx>
---
 drivers/net/ethernet/oa_tc6.c | 53 +++++++++++++++++++++++++++----------------
 1 file changed, 34 insertions(+), 19 deletions(-)

diff --git a/drivers/net/ethernet/oa_tc6.c b/drivers/net/ethernet/oa_tc6.c
index 3fd4851ee66d..180fc47c30b3 100644
--- a/drivers/net/ethernet/oa_tc6.c
+++ b/drivers/net/ethernet/oa_tc6.c
@@ -692,6 +692,12 @@ static void oa_tc6_free_pending_skbs(struct oa_tc6 *tc6)
 	oa_tc6_cleanup_waiting_tx_skb(tc6);
 }
 
+static void oa_tc6_look_for_new_frame(struct oa_tc6 *tc6)
+{
+	tc6->rx_buf_overflow = true;
+	oa_tc6_cleanup_ongoing_rx_skb(tc6);
+}
+
 /* If the failure is at SPI interface level, masking and clearing
  * the interrupt of the device won't work. Since SPI interrupt is
  * disabled, it should stop the repeated interrupts.
@@ -729,8 +735,7 @@ static int oa_tc6_process_extended_status(struct oa_tc6 *tc6)
 	}
 
 	if (FIELD_GET(STATUS0_RX_BUFFER_OVERFLOW_ERROR, value)) {
-		tc6->rx_buf_overflow = true;
-		oa_tc6_cleanup_ongoing_rx_skb(tc6);
+		oa_tc6_look_for_new_frame(tc6);
 		net_err_ratelimited("%s: Receive buffer overflow error\n",
 				    tc6->netdev->name);
 		return -EAGAIN;
@@ -811,9 +816,15 @@ static void oa_tc6_submit_rx_skb(struct oa_tc6 *tc6)
 	tc6->rx_skb = NULL;
 }
 
-static void oa_tc6_update_rx_skb(struct oa_tc6 *tc6, u8 *payload, u8 length)
+static int oa_tc6_update_rx_skb(struct oa_tc6 *tc6, u8 *payload, u8 length)
 {
+	if ((tc6->rx_skb->tail + length) > tc6->rx_skb->end) {
+		oa_tc6_look_for_new_frame(tc6);
+		return -EAGAIN;
+	}
+
 	memcpy(skb_put(tc6->rx_skb, length), payload, length);
+	return 0;
 }
 
 static int oa_tc6_allocate_rx_skb(struct oa_tc6 *tc6)
@@ -837,7 +848,9 @@ static int oa_tc6_prcs_complete_rx_frame(struct oa_tc6 *tc6, u8 *payload,
 	if (ret)
 		return ret;
 
-	oa_tc6_update_rx_skb(tc6, payload, size);
+	ret = oa_tc6_update_rx_skb(tc6, payload, size);
+	if (ret)
+		return ret;
 
 	oa_tc6_submit_rx_skb(tc6);
 
@@ -852,22 +865,24 @@ static int oa_tc6_prcs_rx_frame_start(struct oa_tc6 *tc6, u8 *payload, u16 size)
 	if (ret)
 		return ret;
 
-	oa_tc6_update_rx_skb(tc6, payload, size);
-
-	return 0;
+	return oa_tc6_update_rx_skb(tc6, payload, size);
 }
 
-static void oa_tc6_prcs_rx_frame_end(struct oa_tc6 *tc6, u8 *payload, u16 size)
+static int oa_tc6_prcs_rx_frame_end(struct oa_tc6 *tc6, u8 *payload, u16 size)
 {
-	oa_tc6_update_rx_skb(tc6, payload, size);
+	int ret;
 
-	oa_tc6_submit_rx_skb(tc6);
+	ret = oa_tc6_update_rx_skb(tc6, payload, size);
+	if (!ret)
+		oa_tc6_submit_rx_skb(tc6);
+	return ret;
 }
 
-static void oa_tc6_prcs_ongoing_rx_frame(struct oa_tc6 *tc6, u8 *payload,
-					 u32 footer)
+static int oa_tc6_prcs_ongoing_rx_frame(struct oa_tc6 *tc6, u8 *payload,
+					u32 footer)
 {
-	oa_tc6_update_rx_skb(tc6, payload, OA_TC6_CHUNK_PAYLOAD_SIZE);
+	return oa_tc6_update_rx_skb(tc6, payload,
+				    OA_TC6_CHUNK_PAYLOAD_SIZE);
 }
 
 static int oa_tc6_prcs_rx_chunk_payload(struct oa_tc6 *tc6, u8 *data,
@@ -880,6 +895,7 @@ static int oa_tc6_prcs_rx_chunk_payload(struct oa_tc6 *tc6, u8 *data,
 	bool start_valid = FIELD_GET(OA_TC6_DATA_FOOTER_START_VALID, footer);
 	bool end_valid = FIELD_GET(OA_TC6_DATA_FOOTER_END_VALID, footer);
 	u16 size;
+	int ret;
 
 	/* Restart the new rx frame after receiving rx buffer overflow error */
 	if (start_valid && tc6->rx_buf_overflow)
@@ -907,8 +923,7 @@ static int oa_tc6_prcs_rx_chunk_payload(struct oa_tc6 *tc6, u8 *data,
 	/* Process the chunk with only rx frame end */
 	if (end_valid && !start_valid) {
 		size = end_byte_offset + 1;
-		oa_tc6_prcs_rx_frame_end(tc6, data, size);
-		return 0;
+		return oa_tc6_prcs_rx_frame_end(tc6, data, size);
 	}
 
 	/* Process the chunk with previous rx frame end and next rx frame
@@ -921,7 +936,9 @@ static int oa_tc6_prcs_rx_chunk_payload(struct oa_tc6 *tc6, u8 *data,
 		 */
 		if (tc6->rx_skb) {
 			size = end_byte_offset + 1;
-			oa_tc6_prcs_rx_frame_end(tc6, data, size);
+			ret = oa_tc6_prcs_rx_frame_end(tc6, data, size);
+			if (ret)
+				return ret;
 		}
 		size = OA_TC6_CHUNK_PAYLOAD_SIZE - start_byte_offset;
 		return oa_tc6_prcs_rx_frame_start(tc6,
@@ -930,9 +947,7 @@ static int oa_tc6_prcs_rx_chunk_payload(struct oa_tc6 *tc6, u8 *data,
 	}
 
 	/* Process the chunk with ongoing rx frame data */
-	oa_tc6_prcs_ongoing_rx_frame(tc6, data, footer);
-
-	return 0;
+	return oa_tc6_prcs_ongoing_rx_frame(tc6, data, footer);
 }
 
 static u32 oa_tc6_get_rx_chunk_footer(struct oa_tc6 *tc6, u16 footer_offset)

-- 
2.43.0