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Commit 776ee323 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'arp-always-override-existing-neigh-entries-with-gratuitous-ARP' 

Ihar Hrachyshka says:

====================
arp: always override existing neigh entries with gratuitous ARP

This patchset is spurred by discussion started at
https://patchwork.ozlabs.org/patch/760372/

 where we figured that there is no
real reason for enforcing override by gratuitous ARP packets only when
arp_accept is 1. Same should happen when it's 0 (the default value).

changelog v2: handled review comments by Julian Anastasov
- fixed a mistake in a comment;
- postponed addr_type calculation to as late as possible.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 499350a5 7d472a59

net/ipv4/arp.c

+39 −17
Original line number Diff line number Diff line
@@ -641,6 +641,32 @@ void arp_xmit(struct sk_buff *skb) 
}

EXPORT_SYMBOL(arp_xmit);



static bool arp_is_garp(struct net *net, struct net_device *dev,

			int *addr_type, __be16 ar_op,

			__be32 sip, __be32 tip,

			unsigned char *sha, unsigned char *tha)

{

	bool is_garp = tip == sip;



	/* Gratuitous ARP _replies_ also require target hwaddr to be

	 * the same as source.

	 */

	if (is_garp && ar_op == htons(ARPOP_REPLY))

		is_garp =

			/* IPv4 over IEEE 1394 doesn't provide target

			 * hardware address field in its ARP payload.

			 */

			tha &&

			!memcmp(tha, sha, dev->addr_len);



	if (is_garp) {

		*addr_type = inet_addr_type_dev_table(net, dev, sip);

		if (*addr_type != RTN_UNICAST)

			is_garp = false;

	}

	return is_garp;

}



/*

 *	Process an arp request.

 */
@@ -837,29 +863,25 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb) 


	n = __neigh_lookup(&arp_tbl, &sip, dev, 0);



	if (IN_DEV_ARP_ACCEPT(in_dev)) {

		unsigned int addr_type = inet_addr_type_dev_table(net, dev, sip);

	if (n || IN_DEV_ARP_ACCEPT(in_dev)) {

		addr_type = -1;

		is_garp = arp_is_garp(net, dev, &addr_type, arp->ar_op,

				      sip, tip, sha, tha);

	}



	if (IN_DEV_ARP_ACCEPT(in_dev)) {

		/* Unsolicited ARP is not accepted by default.

		   It is possible, that this option should be enabled for some

		   devices (strip is candidate)

		 */

		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 =

				/* IPv4 over IEEE 1394 doesn't provide target

				 * hardware address field in its ARP payload.

				 */

				tha &&

				!memcmp(tha, sha, dev->addr_len);



		if (!n &&

		    ((arp->ar_op == htons(ARPOP_REPLY)  &&

				addr_type == RTN_UNICAST) || is_garp))

		    (is_garp ||

		     (arp->ar_op == htons(ARPOP_REPLY) &&

		      (addr_type == RTN_UNICAST ||

		       (addr_type < 0 &&

			/* postpone calculation to as late as possible */

			inet_addr_type_dev_table(net, dev, sip) ==

				RTN_UNICAST)))))

			n = __neigh_lookup(&arp_tbl, &sip, dev, 1);

	}