linux-kernel - Sending ARP requests to the peer over PF

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Date:	Mon, 22 Sep 2008 17:28:33 -0400
From:	"Mahesh Kelkar" <maheshkelkar@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Sending ARP requests to the peer over PF_PACKET socket

IP utility "arping" uses PF_PACKET socket to send the arp_request to
the peer. When peer responds with arp_reply, one copy is sent to the
PF_PACKET socket and other to the linux kernel. As a result, linux
kernel creates the new ARP entry.

In this case, kernel doesn't know about the arp_request, hence it
should treat the arp_reply as unsolicited. Linux Kernel (v2.6.21) by
default does not accept unsolicited ARP replies, then how what makes
kernel accept the ARP reply?

Is kernel snooping in the packet with arp_request going out over the
PF_PACKET socket?

Any response is appreciated.

Thanks
Mahesh
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