netdev - Re: [PATCH 09/16] netfilter: nft_meta: use 64-bit time arithmetic

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Date:   Sat, 9 Nov 2019 12:20:10 +0100
From:   Phil Sutter <phil@....cc>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     y2038@...ts.linaro.org, Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, Ander Juaristi <a@...risti.eus>,
        wenxu <wenxu@...oud.cn>, Thomas Gleixner <tglx@...utronix.de>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 09/16] netfilter: nft_meta: use 64-bit time arithmetic

On Fri, Nov 08, 2019 at 10:32:47PM +0100, Arnd Bergmann wrote:
> On 32-bit architectures, get_seconds() returns an unsigned 32-bit
> time value, which also matches the type used in the nft_meta
> code. This will not overflow in year 2038 as a time_t would, but
> it still suffers from the overflow problem later on in year 2106.

I wonder if the assumption that people will still use nft_meta 80 years
from now is an optimistic or pessimistic one. :)

> Change this instance to use the time64_t type consistently
> and avoid the deprecated get_seconds().
> 
> The nft_meta_weekday() calculation potentially gets a little slower
> on 32-bit architectures, but now it has the same behavior as on
> 64-bit architectures and does not overflow.
> 
> Fixes: 63d10e12b00d ("netfilter: nft_meta: support for time matching")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Acked-by: Phil Sutter <phil@....cc>