[tor-dev] Dealing with frequent suspends on Android

Michael Rogers michael at briarproject.org
Tue Nov 6 18:10:42 UTC 2018

On 06/11/2018 01:58, Roger Dingledine wrote:
> On Tue, Nov 06, 2018 at 11:38:33AM +1000, teor wrote:
>>>  so if we could ask the guard for
>>> regular keepalives, we might be able to promise that the CPU will wake
>>> once every keepalive interval, unless the guard connection's lost, in
>>> which case it will wake once every 15 minutes. But keepalives from the
>>> guard would require a protocol change, which would take time to roll
>>> out, and would let the guard know (if it doesn't already) that the
>>> client's running on Android.
>> Tor implemented netflow padding in (May 2017):
>> https://gitweb.torproject.org/torspec.git/tree/padding-spec.txt
>> Connection padding may act like a keepalive, we should consider this
>> use case as we improve our padding designs.
> Relays already send a keepalive (padding) cell every 5 minutes: see
> the KeepalivePeriod config option. That's separate from any of the new
> netflow padding. Clients send them too.

Ah, thanks! I didn't realise keepalives were sent from relays to clients
as well as vice versa.

That gives us a max sleep of 5 minutes when a guard connection's open
and 15 minutes when it's not, which is a great improvement.

Would it have much impact on the network to reduce the default keepalive
interval to, say, one minute?

> The netflow padding is more interesting for the Briar case, since it
> comes way way more often than keepalives: so if you're trying for deep
> sleep but you wake up for network activity every several seconds, you'll
> probably end up sad.

Unfortunately we've disabled netflow padding due to bandwidth and
battery usage.

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