From mboxrd@z Thu Jan 1 00:00:00 1970 From: Murali Karicheri Subject: Does arping update arp table? Date: Tue, 27 Jan 2015 14:23:33 -0500 Message-ID: <54C7E5B5.8060401@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Cc: David Miller To: Return-path: Received: from arroyo.ext.ti.com ([192.94.94.40]:46982 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757900AbbA0TXf (ORCPT ); Tue, 27 Jan 2015 14:23:35 -0500 Sender: netdev-owner@vger.kernel.org List-ID: Experts, The ARP code (net/ipv4/arp.c) seems to treat arp response resulting from a arping as an unsolicited response and doesn't update the arp table. This get updated if the per interface accept sys ctrl is enabled. This command seems to have been updating the arp table in older kernel. For example on a Ubuntu 12.04 based kernel I see a0868495@ula0868495 ~/Project/linux-keystone $ sudo arping 192.168.1.10 -c 1 -f ARPING 192.168.1.10 from 192.168.1.9 eth0 Unicast reply from 192.168.1.10 [00:1B:A9:02:26:10] 5.411ms Sent 1 probes (1 broadcast(s)) Received 1 response(s) a0868495@ula0868495 ~/Project/linux-keystone $ arp -n -a ? (192.168.1.10) at 00:1b:a9:02:26:10 [ether] on eth0 ? (192.168.1.1) at 00:1f:90:6d:5c:a8 [ether] on eth0 a0868495@ula0868495 ~/Project/linux-keystone $ uname -a Linux ula0868495 3.2.0-23-generic #36-Ubuntu SMP Tue Apr 10 20:41:14 UTC 2012 i686 i686 i386 GNU/Linux However this command doesn't update the arp table on my Keystone EVM based on v3.19.x and also newer ubuntu machine based on v3.11. Is this expected behavior? I believe the arp response resulting from a arping command is controlled through per interface accept sys control like as in gratuitous arp. Please repond. Thanks and regards, -- Murali Karicheri Linux Kernel, Texas Instruments