[PATCH] net: Add the same IP detection for duplicate address.

[Dongxu Liu]

The network sends an ARP REQUEST packet to determine
whether there is a host with the same IP.
Windows and some other hosts may send the source IP
address instead of 0.
When IN_DEV_ORCONF(in_dev, DROP_GRATUITOUS_ARP) is enable,
the REQUEST will be dropped.
When IN_DEV_ORCONF(in_dev, DROP_GRATUITOUS_ARP) is disable,
The case should be added to the IP conflict handling process.

Signed-off-by: Dongxu Liu <liudongxu3@xxxxxxxxxx>
---
 net/ipv4/arp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 05eb42f..a51c921 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -801,7 +801,7 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
 						    GFP_ATOMIC);
 
 	/* Special case: IPv4 duplicate address detection packet (RFC2131) */
-	if (sip == 0) {
+	if (sip == 0 || sip == tip) {
 		if (arp->ar_op == htons(ARPOP_REQUEST) &&
 		    inet_addr_type_dev_table(net, dev, tip) == RTN_LOCAL &&
 		    !arp_ignore(in_dev, sip, tip))
-- 
2.12.3