linux-kernel - Re: [PATCH net-next] net: account for encap headers in qdisc pkt len

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Message-ID: <aGdZFhGu40UD6UDU@pop-os.localdomain>
Date: Thu, 3 Jul 2025 21:31:18 -0700
From: Cong Wang <xiyou.wangcong@...il.com>
To: Fengyuan Gong <gfengyuan@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, toke@...e.dk, edumazet@...gle.com,
	"David S . Miller" <davem@...emloft.net>,
	Jamal Hadi Salim <jhs@...atatu.com>, Jiri Pirko <jiri@...nulli.us>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Kuniyuki Iwashima <kuniyu@...gle.com>,
	Ahmed Zaki <ahmed.zaki@...el.com>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	cake@...ts.bufferbloat.net, willemb@...gle.com
Subject: Re: [PATCH net-next] net: account for encap headers in qdisc pkt len

On Wed, Jul 02, 2025 at 04:07:41PM +0000, Fengyuan Gong wrote:
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 11da1e272ec20..dfec541f68e3a 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -3944,7 +3944,10 @@ static void qdisc_pkt_len_init(struct sk_buff *skb)
>  		unsigned int hdr_len;
>  
>  		/* mac layer + network layer */
> -		hdr_len = skb_transport_offset(skb);
> +		if (!skb->encapsulation)
> +			hdr_len = skb_transport_offset(skb);
> +		else
> +			hdr_len = skb_inner_transport_offset(skb);

This pattern seems repeated in a few places, other than the two you are
patching, I saw another one:

2465 static netdev_features_t hns3_features_check(struct sk_buff *skb,
2466                                              struct net_device *dev,
2467                                              netdev_features_t features)
2468 {
2469 #define HNS3_MAX_HDR_LEN        480U
2470 #define HNS3_MAX_L4_HDR_LEN     60U
2471 
2472         size_t len;
2473 
2474         if (skb->ip_summed != CHECKSUM_PARTIAL)
2475                 return features;
2476 
2477         if (skb->encapsulation)
2478                 len = skb_inner_transport_offset(skb);
2479         else
2480                 len = skb_transport_offset(skb);


Maybe worth a helper now?

Thanks!