From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
To: kwiecienmaciek@gmail.com
Cc: linux-sctp@vger.kernel.org, netdev@vger.kernel.org,
alexander.sverdlin@nokia.com,
Maciej Kwiecien <maciej.kwiecien@nokia.com>
Subject: Re: [PATCH] sctp: don't compare hb_timer expire date before starting it
Date: Fri, 22 Feb 2019 09:49:13 -0300 [thread overview]
Message-ID: <20190222124913.GM10665@localhost.localdomain> (raw)
In-Reply-To: <20190222084526.8214-1-maciej.kwiecien@nokia.com>
On Fri, Feb 22, 2019 at 09:45:26AM +0100, kwiecienmaciek@gmail.com wrote:
> From: Maciej Kwiecien <maciej.kwiecien@nokia.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@nokia.com>
> Tested-by: Marcin Stojek <marcin.stojek@nokia.com>
> Signed-off-by: Maciej Kwiecien <maciej.kwiecien@nokia.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
> ---
> net/sctp/transport.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/sctp/transport.c b/net/sctp/transport.c
> index 033696e6f74f..ad158d311ffa 100644
> --- a/net/sctp/transport.c
> +++ b/net/sctp/transport.c
> @@ -207,7 +207,8 @@ void sctp_transport_reset_hb_timer(struct sctp_transport *transport)
>
> /* When a data chunk is sent, reset the heartbeat interval. */
> expires = jiffies + sctp_transport_timeout(transport);
> - if (time_before(transport->hb_timer.expires, expires) &&
> + if ((time_before(transport->hb_timer.expires, expires) ||
> + !timer_pending(&transport->hb_timer)) &&
> !mod_timer(&transport->hb_timer,
> expires + prandom_u32_max(transport->rto)))
> sctp_transport_hold(transport);
> --
> 2.14.1
>
next prev parent reply other threads:[~2019-02-22 12:49 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-22 8:45 [PATCH] sctp: don't compare hb_timer expire date before starting it kwiecienmaciek
2019-02-22 10:03 ` Sverdlin, Alexander (Nokia - DE/Ulm)
2019-02-22 12:49 ` Marcelo Ricardo Leitner [this message]
2019-02-22 19:22 ` David Miller
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