netdev - Re: [PATCH v4 net-next RFC] net: Generic XDP

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Message-Id: <20170419.214049.2190624657363276447.davem@davemloft.net>
Date:   Wed, 19 Apr 2017 21:40:49 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     andy@...yhouse.net
Cc:     alexei.starovoitov@...il.com, michael.chan@...adcom.com,
        netdev@...r.kernel.org, xdp-newbies@...r.kernel.org
Subject: Re: [PATCH v4 net-next RFC] net: Generic XDP

From: Andy Gospodarek <andy@...yhouse.net>
Date: Wed, 19 Apr 2017 10:29:03 -0400

> So I tried a variety of things and the simplest change on top of yours that
> works well for xdp1, xdp2, and xdp_tx_iptunnel. 
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index b3d3a6e..1bab3dc 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -4316,11 +4316,11 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
>  
>  	off = xdp.data - orig_data;
>  	if (off)
> -		__skb_push(skb, off);
> +		__skb_push(skb, -off);

We have to handle both pushing and popping headers, so could you
please test the snippet I asked you to try?

> 	if (off > 0)
> 		__skb_pull(skb, off);
> 	else if (off < 0)
> 		__skb_push(skb, -off);

Thanks.