netdev - Re: [PATCH] samples: bpf: xdp1: remove duplicate code to find protocol

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Date:   Sun, 8 Aug 2021 09:53:41 -0700
From:   Yonghong Song <yhs@...com>
To:     Muhammad Falak R Wani <falakreyaz@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
CC:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>,
        KP Singh <kpsingh@...nel.org>,
        Song Liu <songliubraving@...com>,
        Martin KaFai Lau <kafai@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] samples: bpf: xdp1: remove duplicate code to find
 protocol



On 8/8/21 5:24 AM, Muhammad Falak R Wani wrote:
> The code to find h_vlan_encapsulated_proto is duplicated.
> Remove the extra block.
> 
> Signed-off-by: Muhammad Falak R Wani <falakreyaz@...il.com>
> ---
>   samples/bpf/xdp1_kern.c | 9 ---------
>   1 file changed, 9 deletions(-)
> 
> diff --git a/samples/bpf/xdp1_kern.c b/samples/bpf/xdp1_kern.c
> index 34b64394ed9c..a35e064d7726 100644
> --- a/samples/bpf/xdp1_kern.c
> +++ b/samples/bpf/xdp1_kern.c
> @@ -57,15 +57,6 @@ int xdp_prog1(struct xdp_md *ctx)
>   
>   	h_proto = eth->h_proto;
>   
> -	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
> -		struct vlan_hdr *vhdr;
> -
> -		vhdr = data + nh_off;
> -		nh_off += sizeof(struct vlan_hdr);
> -		if (data + nh_off > data_end)
> -			return rc;
> -		h_proto = vhdr->h_vlan_encapsulated_proto;

No. This is not a duplicate. The h_proto in the above line will be used
in the below "if" condition.

> -	}
>   	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
>   		struct vlan_hdr *vhdr;
>   
>