netdev - Re: [PATCH net-next] ip_gre: Make none-tunnel-dst gre port work with lwtunnel

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Message-Id: <20190118.110620.376531200797865804.davem@davemloft.net>
Date:   Fri, 18 Jan 2019 11:06:20 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     wenxu@...oud.cn
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next] ip_gre: Make none-tunnel-dst gre port work
 with lwtunnel

From: wenxu@...oud.cn
Date: Tue, 15 Jan 2019 10:44:35 +0800

> +		tun_info = skb_tunnel_info(skb);
> +		if (tun_info && (tun_info->mode & IP_TUNNEL_INFO_TX) &&
> +		    ip_tunnel_info_af(tun_info) == AF_INET &&
> +		    tun_info->key.u.ipv4.dst) {
> +			struct iphdr tnl_params_info;
> +
> +			memcpy(&tnl_params_info, tnl_params,
> +			       sizeof(tnl_params_info));

It is not at all reasonable to build and memcpy an entire extra iphdr
on the cpu stack, for every packet transmit.  That's terrible for
performance.

Please find a more minimal and efficient way to achieve the behavior
you are looking for.

Thank you.