On Apr 29, 2010, at 6:35 PM, Nick Mathewson wrote: > On Thu, Apr 29, 2010 at 5:19 AM, Sebastian Sjöberg > <sebastian.sjob...@axis.com> wrote: >> Hi, >> >> I've encountered a problem with openssl bufferevents where libevent reports >> fd:s as writeable but no action is being taken. > > [...] >> There is no problem when I'm connecting without tls so I think this is an >> issue with openssl bufferevents and my guess is that somehow the write >> events that openssl bufferevents sets up sometimes doesn't get removed or >> disabled properly. >> >> Is this an issue that someone else has seen and does anyone have any >> pointers on how to debug this problem? > > > I haven't run into this myself yet, but the openssl code is relatively > new, and probably has some bugs left. > > To clarify, it seems that the problem is that Libevent bufferevent > openssl code never deletes the relevant read events, even though it > isn't actually interested in reading? Or the problem is that epoll is > returning immediately but not making any events active?
It seems to be the latter. > > If it's the first problem, I'd try adding debugging messages to the > points in bufferevent_openssl that call event_add, event_del, and > _bufferevent_add_event, along with debugging statements to display the > return values of SSL_read and SSL_write, to see at what point we're > supposed to be deleting the relevant read event but not really doing > it. I've added stack backtraces in event_(del|add)_internal, mostly to figure out where they get called from in the openssl bufferevent code but I haven't yet been able to interpret them completely but they might shed some light on what's going on. > > If it's the second problem, I'd start by testing whether stuff begins > to work when you set the EVENT_NOEPOLL environment variable. If so, > then the bug is probably with the epoll backend -- or at least, it > requires the epoll backend to appear. To debug this, I'd add > debugging messages to the loop in epoll_dispatch that calls > evmap_io_active to tell me whenever it decided not to call > evmap_io_active, and I'd have evmap_io_active tell me whenever it made > 0 events become active. Cheers, I haven't yet been able to reproduce it when disabling epoll. I've started to debug the evmap_io_active calls and after a while there are a no events being activated as you said so I guess at some point the there's a mismatch between what's in epoll and in the event map. > > With any luck, the debugging output should help figure out exactly > what's going wrong here. > > I'm afraid I'm about to be away from the internet for tomorrow and the > weekend, so I won't be able to help much more until early next week. > Good luck! Thanks, I won't be looking at this until after the weekend either. Best regards, Sebastian Sjoberg > > yrs, > -- > Nick > *********************************************************************** > To unsubscribe, send an e-mail to majord...@freehaven.net with > unsubscribe libevent-users in the body. *********************************************************************** To unsubscribe, send an e-mail to majord...@freehaven.net with unsubscribe libevent-users in the body.
