[BRLTTY] Virtual driver is not reading the socket

[Jaroslav Skarvada]

----- Original Message -----
> 
> 
> ----- Original Message -----
> > ----- Original Message -----
> > > Hi,
> > > 
> > > for me the Virtual driver (vr) doesn't work, reproducer:
> > > 
> > > $ brltty -b vr -d server:127.0.0.1 -x a2 -A auth=none
> > > $ telnet 127.0.0.1 35752
> > > cells 20
> > > 
> > > And nothing happened. It seems the 'vr' driver thinks there is
> > > no data on the socket received, i.e. the awaitSocketInput check in
> > > readNetworkSocket never succeed.
> > > 
> > > I didn't debug the complex underlying machinery, but the attached
> > > patch that bypassed it and used MSG_DONTWAIT recv flag (which is
> > > available since kernel 2.2) works for me and the Virtual driver
> > > started to work again. I tested it on Fedora 23 (kernel 4.4.7)
> > > 
> > > thanks & regards
> > > 
> > > Jaroslav
> > > 
> > 
> > I bisected the problem to the following commit:
> > https://github.com/brltty/brltty/commit/cd62215b643b486c93fb28c3fe02e3727cdf3f91
> > 
> > and simply reverting the commit for the asyncAwaitCondtition resolved the
> > problem
> > for me
> > 
> > regards
> > 
> > Jaroslav
> > 
> 
> The source of the problem is the following:
> In Drivers/Braille/Virtual/braille.c:125
>   if (awaitSocketInput(descriptor, 0)) {
> 
> i.e. it uses timeout = 0, but in Programs/async_wait.c:151
> the
> if (afterTimePeriod(&period, &elapsed)) return 0;
> returned immediately due to timeout = 0 without checking the
> condition.
> 
> Maybe the 'vr' driver shouldn't use timeout = 0, but I think that
> the underlaying logic should cope with it. For me it's more logical
> behaviour if it do one check even with timeout = 0, so probably
> the reverted version of the code is OK
> 
> thanks & regards
> 
> Jaroslav

Hi,

what's your opinion how to fix it?
a) fix asyncAwaitCondition to handle zero timeouts, or
b) increase timeout in 'vr' driver?

Do you want github pull request?

thanks & regards

Jaroslav