netdev - [PATCH net] net: mctp: usb: initialise mac header in RX path

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Message-Id: <20250829-mctp-usb-mac-header-v1-1-338ad725e183@codeconstruct.com.au>
Date: Fri, 29 Aug 2025 15:40:23 +0800
From: Jeremy Kerr <jk@...econstruct.com.au>
To: Matt Johnston <matt@...econstruct.com.au>, 
 Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org
Subject: [PATCH net] net: mctp: usb: initialise mac header in RX path

We're not currently setting skb->mac_header on ingress, and the netdev
core rx path expects it. Without it, we'll hit a warning on DEBUG_NETDEV
from commit 1e4033b53db4 ("net: skb_reset_mac_len() must check if
mac_header was set")

Initialise the mac_header to refer to the USB transport header.

Fixes: 0791c0327a6e ("net: mctp: Add MCTP USB transport driver")
Signed-off-by: Jeremy Kerr <jk@...econstruct.com.au>
---
 drivers/net/mctp/mctp-usb.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/mctp/mctp-usb.c b/drivers/net/mctp/mctp-usb.c
index 775a386d0aca1242e5d3c8a750c1d0825341caa6..36ccc53b17975912c7d310fe8d58eb91fe482732 100644
--- a/drivers/net/mctp/mctp-usb.c
+++ b/drivers/net/mctp/mctp-usb.c
@@ -183,6 +183,7 @@ static void mctp_usb_in_complete(struct urb *urb)
 		struct mctp_usb_hdr *hdr;
 		u8 pkt_len; /* length of MCTP packet, no USB header */

+		skb_reset_mac_header(skb);
 		hdr = skb_pull_data(skb, sizeof(*hdr));
 		if (!hdr)
 			break;

---
base-commit: 007a5ffadc4fd51739527f1503b7cf048f31c413
change-id: 20250829-mctp-usb-mac-header-7b6894234dbf

Best regards,
-- 
Jeremy Kerr <jk@...econstruct.com.au>