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([2601:282:803:7700:54d7:a956:162c:3e8]) by smtp.googlemail.com with ESMTPSA id p189sm1717117iof.17.2020.03.08.19.15.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 08 Mar 2020 19:15:15 -0700 (PDT) Subject: Re: IPv6 regression introduced by commit 3b6761d18bc11f2af2a6fc494e9026d39593f22c To: Alarig Le Lay Cc: netdev@vger.kernel.org, jack@basilfillan.uk, Vincent Bernat References: <20200305081747.tullbdlj66yf3w2w@mew.swordarmor.fr> <20200308105729.72pbglywnahbl7hs@mew.swordarmor.fr> From: David Ahern Message-ID: <27457094-b62a-f029-e259-f7a274fee49d@gmail.com> Date: Sun, 8 Mar 2020 20:15:14 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200308105729.72pbglywnahbl7hs@mew.swordarmor.fr> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 3/8/20 4:57 AM, Alarig Le Lay wrote: > On sam. 7 mars 17:52:10 2020, David Ahern wrote: >> On 3/5/20 1:17 AM, Alarig Le Lay wrote: >> Kernel version? > > I’ve seen this from 4.19 on my experience, it works at least until 4.15. > >> you are monitoring neighbor states with 'ip monitor' or something else? > > Yes, 'ip -ts monitor neigh' to be exact. > >> The above does not reproduce for me on 5.6 or 4.19, and I would have >> been really surprised if it had, so I have to question the git bisect >> result. > > My personal experience is that, while routing is activated (and having a > full-view, I don’t have any soft router without it), the neighbors are > flapping, thus causing a blackhole. > It doesn’t happen with a limit traffic processing. The limit is around > 20 Mbps from what I can see. If you are using x86 based CPU you can do this: perf probe ip6_dst_alloc%return ret=%ax perf record -e probe:* -a -g -- sleep 10 --> run this during the flapping perf script this will show if the flapping is due to dst alloc failures. Other things to try: perf probe ip6_dst_gc perf stat -e probe:* -a -I 1000 --> will show calls/sec to running dst gc perf probe __ip6_rt_update_pmtu perf stat -e probe:* -a -I 1000 --> will show calls/sec to mtu updating perf probe rt6_insert_exception perf state -e probe:* -a -I 1000 --> shows calls/sec to inserting exceptions (in each you can remove the previous probe using 'perf probe -d ' or use -e to only see data for the one event). > I have the problem with 5.3 (proxmox 6), so unless FIB handling has been > changed since then, I doubt that it will works, but I will try on > Monday. > a fair amount of changes went in through 5.4 including improvements to neighbor handling. 5.4 (I think) also had changes around dumping the route cache.