netdev - Re: [PATCH net v3] sched: consistently handle layer3 header accesses in the presence of VLANs

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Date:   Sat, 4 Jul 2020 12:24:41 +0900
From:   Toshiaki Makita <toshiaki.makita1@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, bpf@...r.kernel.org,
        cake@...ts.bufferbloat.net, Davide Caratti <dcaratti@...hat.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Roman Mashak <mrv@...atatu.com>,
        Lawrence Brakmo <brakmo@...com>,
        Ilya Ponetayev <i.ponetaev@...systems.com>
Subject: Re: [PATCH net v3] sched: consistently handle layer3 header accesses
 in the presence of VLANs

On 2020/07/04 5:26, Toke Høiland-Jørgensen wrote:
...
> +/* A getter for the SKB protocol field which will handle VLAN tags consistently
> + * whether VLAN acceleration is enabled or not.
> + */
> +static inline __be16 skb_protocol(const struct sk_buff *skb, bool skip_vlan)
> +{
> +	unsigned int offset = skb_mac_offset(skb) + sizeof(struct ethhdr);
> +	__be16 proto = skb->protocol;
> +
> +	if (!skip_vlan)
> +		/* VLAN acceleration strips the VLAN header from the skb and
> +		 * moves it to skb->vlan_proto
> +		 */
> +		return skb_vlan_tag_present(skb) ? skb->vlan_proto : proto;
> +
> +	while (eth_type_vlan(proto)) {
> +		struct vlan_hdr vhdr, *vh;
> +
> +		vh = skb_header_pointer(skb, offset, sizeof(vhdr), &vhdr);
> +		if (!vh)
> +			break;
> +
> +		proto = vh->h_vlan_encapsulated_proto;
> +		offset += sizeof(vhdr);
> +	}

Why don't you use __vlan_get_protocol() here? It looks quite similar.
Is there any problem with using that?

Toshiaki Makita