netdev - [PATCH v3] net: bcmgenet: Fix FCS generation for fragmented skbuffs

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Message-ID: <20231228135638.1339245-1-adriancinal1@gmail.com>
Date: Thu, 28 Dec 2023 14:56:38 +0100
From: Adrian Cinal <adriancinal1@...il.com>
To: netdev@...r.kernel.org
Cc: opendmb@...il.com,
	florian.fainelli@...adcom.com,
	bcm-kernel-feedback-list@...adcom.com,
	Adrian Cinal <adriancinal@...il.com>,
	Adrian Cinal <adriancinal1@...il.com>
Subject: [PATCH v3] net: bcmgenet: Fix FCS generation for fragmented skbuffs

From: Adrian Cinal <adriancinal@...il.com>

The flag DMA_TX_APPEND_CRC was only written to the first DMA descriptor
in the TX path, where each descriptor corresponds to a single skbuff
fragment (or the skbuff head). This led to packets with no FCS appearing
on the wire if the kernel allocated the packet in fragments, which would
always happen when using PACKET_MMAP/TPACKET (cf. tpacket_fill_skb() in
net/af_packet.c).

Fixes: 1c1008c793fa ("net: bcmgenet: add main driver file")
Signed-off-by: Adrian Cinal <adriancinal1@...il.com>
---
Differs from v2 in that now the flag DMA_TX_APPEND_CRC is set for all
fragments (so as to be in line with the specification requiring the flag
be set alongside DMA_SOP).

 drivers/net/ethernet/broadcom/genet/bcmgenet.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
index 1174684a7f23..d86e5da6e157 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -2140,8 +2140,10 @@ static netdev_tx_t bcmgenet_xmit(struct sk_buff *skb, struct net_device *dev)
 		/* Note: if we ever change from DMA_TX_APPEND_CRC below we
 		 * will need to restore software padding of "runt" packets
 		 */
+		len_stat |= DMA_TX_APPEND_CRC;
+
 		if (!i) {
-			len_stat |= DMA_TX_APPEND_CRC | DMA_SOP;
+			len_stat |= DMA_SOP;
 			if (skb->ip_summed == CHECKSUM_PARTIAL)
 				len_stat |= DMA_TX_DO_CSUM;
 		}
-- 
2.43.0