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([2601:282:800:fd80:3913:d4da:8ed6:bdf3]) by smtp.googlemail.com with ESMTPSA id c81sm3588065iof.28.2019.07.10.12.13.03 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Jul 2019 12:13:04 -0700 (PDT) Subject: Re: Question about linux kernel commit: "net/ipv6: move metrics from dst to rt6_info" To: Stefano Brivio , Jan Szewczyk Cc: "davem@davemloft.net" , "netdev@vger.kernel.org" , Wei Wang , Martin KaFai Lau , Eric Dumazet References: <20190710210954.530d72a5@elisabeth> From: David Ahern Message-ID: <5981b8d0-cfdf-d230-fa22-cfcfaa5ee4b9@gmail.com> Date: Wed, 10 Jul 2019 13:13:03 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190710210954.530d72a5@elisabeth> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 7/10/19 1:09 PM, Stefano Brivio wrote: > Jan, > > On Wed, 10 Jul 2019 12:59:41 +0000 > Jan Szewczyk wrote: > >> Hi! >> I digged up a little further and maybe it's not a problem with MTU >> itself. I checked every entry I get from RTM_GETROUTE netlink message >> and after triggering "too big packet" by pinging ipv6address I get >> exactly the same messages on 4.12 and 4.18, except that the one with >> that pinged ipv6address is missing on 4.18 at all. What is weird - >> it's visible when running "ip route get to ipv6address". Do you know >> why there is a mismatch there? > > If I understand you correctly, an implementation equivalent to 'ip -6 > route list show' (using the NLM_F_DUMP flag) won't show the so-called > route exception, while 'ip -6 route get' shows it. > > If that's the case: that was broken by commit 2b760fcf5cfb ("ipv6: hook > up exception table to store dst cache") that landed in 4.15, and fixed > by net-next commit 1e47b4837f3b ("ipv6: Dump route exceptions if > requested"). For more details, see the log of this commit itself. > ah, good point. My mind locked on RTM_GETROUTE as a specific route request not a dump.