netdev - Re: [PATCH net-next] ipv6: use DST_NOCOUNT in ip6_rt_pcpu

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Message-ID: <92c6ab11-3022-a01a-95db-13f6da8637cc@gmail.com>
Date:   Fri, 8 May 2020 09:03:57 -0600
From:   David Ahern <dsahern@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>, Martin KaFai Lau <kafai@...com>,
        David Ahern <dsahern@...nel.org>, Wei Wang <weiwan@...gle.com>,
        Maciej Żenczykowski <maze@...gle.com>
Subject: Re: [PATCH net-next] ipv6: use DST_NOCOUNT in ip6_rt_pcpu_alloc()

On 5/8/20 8:43 AM, Eric Dumazet wrote:
> This patch can be backported without any pains ;)

sure, but you tagged it as net-next, not net.

> 
> Getting rid of limits, even for exceptions ?

Running through where dst entries are created in IPv6:
1. pcpu cache
2. uncached_list
3. exceptions like pmtu and redirect

All of those match IPv4 and as I recall IPv4 does not have any limits,
even on exceptions and redirect. If IPv4 does not have limits, why
should IPv6? And if the argument is uncontrolled memory consumption, is
there an expectation that IPv6 generates more exceptions?

My argument really just boils down to consistency between them. IPv4
does not use DST_NOCOUNT, so why put that burden on v6?