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From: Arne Schwabe <arne@...1227...>
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Date: Sat, 2 Jul 2016 12:32:57 +0200
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In-Reply-To: <1467430368-25437-1-git-send-email-selva.nair@...277...>
Subject: Re: [Openvpn-devel] [PATCH] Exponentially backoff on repeated
 connect retries
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To: Selva Nair <selva.nair@...277...>, openvpn-devel@lists.sourceforge.net

Am 02.07.16 um 05:32 schrieb Selva Nair:
> - When the number of retries per remote exceeds a limit
>   (hard coded to 5), double the restart pause interval
>   for each additional retry per remote.
> - Trigger a SIGHUP to reset the retry count when the pause
>   interval exceeds 1024 times the base value of restart pause.
> 
> The base value of restart pause is set using --connect-retry
> (5 seconds by default). If it is set to zero no slow-down
> will happen.
> 
> Signed-off-by: Selva Nair <selva.nair@...277...>
> ---
>  src/openvpn/init.c |   12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/src/openvpn/init.c b/src/openvpn/init.c
> index 498d36f..45e8878 100644
> --- a/src/openvpn/init.c
> +++ b/src/openvpn/init.c
> @@ -1955,6 +1955,7 @@ static void
>  socket_restart_pause (struct context *c)
>  {
>    int sec = 2;
> +  int backoff = 0;
>  
>    switch (c->options.ce.proto)
>      {
> @@ -1977,6 +1978,17 @@ socket_restart_pause (struct context *c)
>      sec = 10;
>  #endif
>  
> +  /* Slow down reconnection after 5 retries per remote */
> +  backoff = (c->options.unsuccessful_attempts / c->options.connection_list->len) - 5;
> +  if (backoff > 0)
> +    sec <<= min_int (backoff, 10);
> +
> +  if (backoff > 10 && sec > 0)
> +    {
> +      register_signal (c, SIGHUP, "Too many restarts");
> +      return;
> +    }

And why sighup? Shouldn't just limiting sec be enought. SIGHUP has many
side effects. I don't think we should trigger these for connection time.


With default setting this results in a SIGHUP after some hours and also
the last intervals with 5120s are too big for default settings. I would
aim for something lower like five or ten minutes.

Arne