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

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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: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2017-05-21 13:26:46 -04:00
commit 776ee323dd
1 changed files with 39 additions and 17 deletions
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56
net/ipv4/arp.c
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@ -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);
}