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Date:   Tue, 20 Aug 2019 13:58:03 -0700 (PDT)
Message-Id: <20190820.135803.846099092737191145.davem@davemloft.net>
To:     liudongxu3@huawei.com
Cc:     kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: Fix detection for IPv4 duplicate address.
From:   David Miller <davem@davemloft.net>
In-Reply-To: <20190820151905.13148-1-liudongxu3@huawei.com>
References: <20190820151905.13148-1-liudongxu3@huawei.com>
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From: Dongxu Liu <liudongxu3@huawei.com>
Date: Tue, 20 Aug 2019 23:19:05 +0800

> @@ -800,8 +800,11 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
>  			    iptunnel_metadata_reply(skb_metadata_dst(skb),
>  						    GFP_ATOMIC);
>  
> -	/* Special case: IPv4 duplicate address detection packet (RFC2131) */
> -	if (sip == 0) {
> +/* Special case: IPv4 duplicate address detection packet (RFC2131).
> + * Linux usually sends zero to detect duplication, and windows may
> + * send a same ip (not zero, sip equal to tip) to do this detection.
> + */
> +	if (sip == 0 || sip == tip) {

Regardless of whether this is a valid change or not, you've unindented the
comment which is completely inappropriate.