netdev - [PATCH v1 net 2/4] net: ena: Fix xdp drops handling due to multibuf packets

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Message-ID: <20231210083056.30357-3-darinzon@amazon.com>
Date: Sun, 10 Dec 2023 08:30:54 +0000
From: <darinzon@...zon.com>
To: David Miller <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
	<netdev@...r.kernel.org>
CC: David Arinzon <darinzon@...zon.com>, "Woodhouse, David" <dwmw@...zon.com>,
	"Machulsky, Zorik" <zorik@...zon.com>, "Matushevsky, Alexander"
	<matua@...zon.com>, Saeed Bshara <saeedb@...zon.com>, "Wilson, Matt"
	<msw@...zon.com>, "Liguori, Anthony" <aliguori@...zon.com>, "Bshara, Nafea"
	<nafea@...zon.com>, "Belgazal, Netanel" <netanel@...zon.com>, "Saidi, Ali"
	<alisaidi@...zon.com>, "Herrenschmidt, Benjamin" <benh@...zon.com>,
	"Kiyanovski, Arthur" <akiyano@...zon.com>, "Dagan, Noam" <ndagan@...zon.com>,
	"Agroskin, Shay" <shayagr@...zon.com>, "Itzko, Shahar" <itzko@...zon.com>,
	"Abboud, Osama" <osamaabb@...zon.com>, "Ostrovsky, Evgeny"
	<evostrov@...zon.com>
Subject: [PATCH v1 net 2/4] net: ena: Fix xdp drops handling due to multibuf packets

From: David Arinzon <darinzon@...zon.com>

Current xdp code drops packets larger than ENA_XDP_MAX_MTU.
This is an incorrect condition since the problem is not the
size of the packet, rather the number of buffers it contains.

This commit:

1. Identifies and drops XDP multi-buffer packets at the
   beginning of the function.
2. Increases the xdp drop statistic when this drop occurs.
3. Adds a one-time print that such drops are happening to
   give better indication to the user.

Fixes: 838c93dc5449 ("net: ena: implement XDP drop support")
Signed-off-by: Arthur Kiyanovski <akiyano@...zon.com>
---
 drivers/net/ethernet/amazon/ena/ena_netdev.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index 9884ef3..c7bc572 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -1672,20 +1672,23 @@ static void ena_set_rx_hash(struct ena_ring *rx_ring,
 	}
 }
 
-static int ena_xdp_handle_buff(struct ena_ring *rx_ring, struct xdp_buff *xdp)
+static int ena_xdp_handle_buff(struct ena_ring *rx_ring, struct xdp_buff *xdp, u16 num_descs)
 {
 	struct ena_rx_buffer *rx_info;
 	int ret;
 
+	/* XDP multi-buffer packets not supported */
+	if (unlikely(num_descs > 1)) {
+		netdev_err_once(rx_ring->adapter->netdev,
+				"xdp: dropped unsupported multi-buffer packets\n");
+		ena_increase_stat(&rx_ring->rx_stats.xdp_drop, 1, &rx_ring->syncp);
+		return ENA_XDP_DROP;
+	}
+
 	rx_info = &rx_ring->rx_buffer_info[rx_ring->ena_bufs[0].req_id];
 	xdp_prepare_buff(xdp, page_address(rx_info->page),
 			 rx_info->buf_offset,
 			 rx_ring->ena_bufs[0].len, false);
-	/* If for some reason we received a bigger packet than
-	 * we expect, then we simply drop it
-	 */
-	if (unlikely(rx_ring->ena_bufs[0].len > ENA_XDP_MAX_MTU))
-		return ENA_XDP_DROP;
 
 	ret = ena_xdp_execute(rx_ring, xdp);
 
@@ -1754,7 +1757,7 @@ static int ena_clean_rx_irq(struct ena_ring *rx_ring, struct napi_struct *napi,
 			  ena_rx_ctx.l4_proto, ena_rx_ctx.hash);
 
 		if (ena_xdp_present_ring(rx_ring))
-			xdp_verdict = ena_xdp_handle_buff(rx_ring, &xdp);
+			xdp_verdict = ena_xdp_handle_buff(rx_ring, &xdp, ena_rx_ctx.descs);
 
 		/* allocate skb and fill it */
 		if (xdp_verdict == ENA_XDP_PASS)
-- 
2.40.1