netdev - Re: [PATCH] arp: honour gratuitous ARP _replies

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Message-Id: <20170515.140832.354922796595622860.davem@davemloft.net>
Date:   Mon, 15 May 2017 14:08:32 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     ihrachys@...hat.com
Cc:     jmorris@...ei.org, yoshfuji@...ux-ipv6.org, kaber@...sh.net,
        netdev@...r.kernel.org
Subject: Re: [PATCH] arp: honour gratuitous ARP _replies_

From: Ihar Hrachyshka <ihrachys@...hat.com>
Date: Tue,  9 May 2017 17:16:07 -0700

> @@ -842,8 +844,20 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
>  		   It is possible, that this option should be enabled for some
>  		   devices (strip is candidate)
>  		 */
> -		is_garp = arp->ar_op == htons(ARPOP_REQUEST) && tip == sip &&
> -			  addr_type == RTN_UNICAST;
> +		is_garp = tip == sip && addr_type == RTN_UNICAST;
> +
> +		/* Unsolicited ARP _replies_ also require target hwaddr to be
> +		 * the same as source.
> +		 */
> +		if (is_garp && arp->ar_op == htons(ARPOP_REPLY))
> +			is_garp =
> +#if IS_ENABLED(CONFIG_FIREWIRE_NET)
> +				/* IPv4 over IEEE 1394 doesn't provide target
> +				 * hardware address field in its ARP payload.
> +				 */
> +				tha &&
> +#endif
> +				!memcmp(tha, sha, dev->addr_len);
>  

The ifdefs here make the test harder to understand.

I would suggest removing the ifdef and letting the compiler remove the 'tha'
check if it can.

Thank you.