netdev - Re: [PATCH net-next 3/3] tcp: use monotonic timestamps for PAWS

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Date:   Mon, 18 Jun 2018 08:59:34 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Arnd Bergmann <arnd@...db.de>, Harsh Jain <harsh@...lsio.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Atul Gupta <atul.gupta@...lsio.com>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     y2038@...ts.linaro.org, Michael Werner <werner@...lsio.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Florian Westphal <fw@...len.de>,
        Christoph Paasch <cpaasch@...le.com>,
        Lawrence Brakmo <brakmo@...com>,
        Ursula Braun <ubraun@...ux.vnet.ibm.com>,
        Priyaranjan Jha <priyarjha@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Ivan Delalande <colona@...sta.com>,
        Maciej Żenczykowski <maze@...gle.com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next 3/3] tcp: use monotonic timestamps for PAWS



On 06/18/2018 08:22 AM, Arnd Bergmann wrote:
> Using get_seconds() for timestamps is deprecated since it can lead
> to overflows on 32-bit systems. While the interface generally doesn't
> overflow until year 2106, the specific implementation of the TCP PAWS
> algorithm breaks in 2038 when the intermediate signed 32-bit timestamps
> overflow.
>
...

>
>  
>  static inline u32 tcp_cookie_time(void)
> @@ -1361,7 +1362,7 @@ static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
>  {
>  	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
>  		return true;
> -	if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
> +	if (unlikely(ktime_get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
>  		return true;
>  	/*
>  	 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
> @@ -1391,7 +1392,7 @@ static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
>  
>  	   However, we can relax time bounds for RST segments to MSL.
>  	 */
> -	if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
> +	if (rst && ktime_get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
>  		return false;
>  	return true;



Please use the time_after32(), since ktime_get_seconds() is time64_t while ts_recent_stamp is int.

Same remark for tcp_twsk_unique()

Lets clean up this stuff, thanks !