netdev - Re: [PATCH net] {pktgen, xfrm} re-caculate IPv4 checksum after transformation

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Message-Id: <20131130.161749.1028599462373827329.davem@davemloft.net>
Date:	Sat, 30 Nov 2013 16:17:49 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	fan.du@...driver.com
Cc:	steffen.klassert@...unet.com, netdev@...r.kernel.org
Subject: Re: [PATCH net] {pktgen, xfrm} re-caculate IPv4 checksum after
 transformation

From: Fan Du <fan.du@...driver.com>
Date: Fri, 29 Nov 2013 10:59:09 +0800

> @@ -2786,6 +2786,8 @@ static struct sk_buff *fill_packet_ipv4(struct net_device *odev,
>  #ifdef CONFIG_XFRM
>  	if (!process_ipsec(pkt_dev, skb, protocol))
>  		return NULL;
> +	iph = ip_hdr(skb);
> +	ip_send_check(iph);
>  #endif

This is rediculous.  You're computing the checksum _twice_ unconditionally,
even if process_ipsec() does _nothing_.

Make process_ipsec() fix the checksum, but only if it actually does
something which makes the recomputation even necessary.

Thanks.
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