From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jim Westfall Subject: [PATCH 0/2] ipv4: Make neigh lookup keys for loopback/point-to-point devices be INADDR_ANY Date: Sat, 13 Jan 2018 15:59:10 -0800 Message-ID: <20180113235910.GF740@surrealistic.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: netdev@vger.kernel.org Return-path: Received: from whipper.surrealistic.net ([50.251.204.81]:48404 "EHLO whipper.surrealistic.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751168AbeAMX7L (ORCPT ); Sat, 13 Jan 2018 18:59:11 -0500 Received: from localhost (whipper.surrealistic.net [local]) by whipper.surrealistic.net (OpenSMTPD) with ESMTPA id 86b6a7f7 for ; Sat, 13 Jan 2018 23:59:10 +0000 (UTC) Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: This used to be the previous behavior in older kernels but became broken in a263b3093641f (ipv4: Make neigh lookups directly in output packet path) and then later removed because it was broken in 0bb4087cbec0 (ipv4: Fix neighlookup keying over loopback/point-to-point devices) Not having this results in there being an arp entry for every remote ip address that the device talks to. Given a fairly active device it can cause the arp table to become huge and/or having to add/purge large number of entires to keep within table size thresholds. $ ip -4 neigh show nud noarp | grep tun | wc -l 55850 $ lnstat -k arp_cache:entries,arp_cache:allocs,arp_cache:destroys -c 10 arp_cach|arp_cach|arp_cach| entries| allocs|destroys| 81493|620166816|620126069| 101867| 10186| 0| 113854| 5993| 0| 118773| 2459| 0| 27937| 18579| 63998| 39256| 5659| 0| 56231| 8487| 0| 65602| 4685| 0| 79697| 7047| 0| 90733| 5517| 0| Jim Westfall (2): net: Allow neigh contructor functions ability to modify the primary_key ipv4: Make neigh lookup keys for loopback/point-to-point devices be INADDR_ANY include/net/arp.h | 3 +++ net/core/neighbour.c | 4 ++-- net/ipv4/arp.c | 7 ++++++- 3 files changed, 11 insertions(+), 3 deletions(-)