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Message-Id: <20190222.112222.1641489327512557605.davem@davemloft.net>
Date: Fri, 22 Feb 2019 11:22:22 -0800 (PST)
From: David Miller <davem@...emloft.net>
To: kwiecienmaciek@...il.com
Cc: linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
alexander.sverdlin@...ia.com, maciej.kwiecien@...ia.com
Subject: Re: [PATCH] sctp: don't compare hb_timer expire date before
starting it
From: kwiecienmaciek@...il.com
Date: Fri, 22 Feb 2019 09:45:26 +0100
> From: Maciej Kwiecien <maciej.kwiecien@...ia.com>
>
> hb_timer might not start at all for a particular transport because its
> start is conditional. In a result a node is not sending heartbeats.
>
> Function sctp_transport_reset_hb_timer has two roles:
> - initial start of hb_timer for a given transport,
> - update expire date of hb_timer for a given transport.
> The function is optimized to update timer's expire only if it is before
> a new calculated one but this comparison is invalid for a timer which
> has not yet started. Such a timer has expire == 0 and if a new expire
> value is bigger than (MAX_JIFFIES / 2 + 2) then "time_before" macro will
> fail and timer will not start resulting in no heartbeat packets send by
> the node.
>
> This was found when association was initialized within first 5 mins
> after system boot due to jiffies init value which is near to MAX_JIFFIES.
>
> Test kernel version: 4.9.154 (ARCH=arm)
> hb_timer.expire = 0; //initialized, not started timer
> new_expire = MAX_JIFFIES / 2 + 2; //or more
> time_before(hb_timer.expire, new_expire) == false
>
> Fixes: ba6f5e33bdbb ("sctp: avoid refreshing heartbeat timer too often")
> Reported-by: Marcin Stojek <marcin.stojek@...ia.com>
> Tested-by: Marcin Stojek <marcin.stojek@...ia.com>
> Signed-off-by: Maciej Kwiecien <maciej.kwiecien@...ia.com>
Applied and queued up for -stable, thank you.
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