Bug#861115: Please consider increasing net.ipv6.route.max_size default value

From	Vincent Bernat <bernat@debian.org>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#861115: Please consider increasing net.ipv6.route.max_size default value
Date	2020-01-22 07:00 +0100
Message-ID	<zrhdv-8uB-3@gated-at.bofh.it> (permalink)
References	(1 earlier) <zr7e9-2A1-1@gated-at.bofh.it> <zr7Hb-2JJ-7@gated-at.bofh.it> <zrbB7-542-7@gated-at.bofh.it> <tzR3X-26a-9@gated-at.bofh.it> <zrbB7-542-7@gated-at.bofh.it>
Organization	Debian

Cross-posted to 2 groups.

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 ❦ 21 janvier 2020 23:51 +00, Tim Bray <tim@provu.co.uk>:

>> This setting is for the size of the route cache. You can have far more
>> routes. In the past, there were bugs where each lookup will be put in
>> cache, but since 4.2, only the PMTU exceptions are stored in cache. See
>> <https://vincent.bernat.ch/en/blog/2017-ipv6-route-lookup-linux#caching>
>>
>> Do you have a lot of entries in `ip -6 route show cache`?
>
>
> No entries at all in
> `ip -6 route show cache`
>
> and none in `ip -6 route show table cache`
>
> It is a quiet time of day, so I'll check again.
>
> What prompted me to look at net.ipv6.route.max_size was because I built my own newer kernel (in desperation).
>
> Linux version 5.4.11 (from kernel.org, .config from debian buster, make olddefconfig) gives out in dmesg:
>
> Route cache is full: consider increasing sysctl net.ipv[4|6].route.max_size.
>
>
> I've never seen this message on 4.19 Debian buster, but increasing
> net.ipv6.route.max_size made all the network hangs go away, both on
> 5.4.11 and 4.19

The message was addeed in 5.1. I'll test later today to check if "ip -6
route show cache" still works.
-- 
Parenthesise to avoid ambiguity.
            - The Elements of Programming Style (Kernighan & Plauger)

Thread

Bug#861115: Please consider increasing net.ipv6.route.max_size default value Tim Bray <tim@provu.co.uk> - 2020-01-21 20:20 +0100
  Bug#861115: Please consider increasing net.ipv6.route.max_size default value Vincent Bernat <bernat@debian.org> - 2020-01-21 20:50 +0100
    Bug#861115: Please consider increasing net.ipv6.route.max_size default value Tim Bray <tim@provu.co.uk> - 2020-01-22 01:00 +0100
      Bug#861115: Please consider increasing net.ipv6.route.max_size default value Vincent Bernat <bernat@debian.org> - 2020-01-22 07:00 +0100
  Bug#861115: Please consider increasing net.ipv6.route.max_size default value Asbjørn Sloth Tønnesen <ast@fiberby.net> - 2020-02-27 15:50 +0100

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