Hi Marc, On Jul 15 20:54, Marc Hoersken via Cygwin wrote: > Hello everyone, > > I identified an issue related to the way the events FD_CONNECT and FD_CLOSE > returned by WSAEnumNetworkEvents are currently handled in > winsup/cygwin/fhandler_socket_inet.cc. > > It seems like the code does not handle the fact that those events are > returned only once for a socket and if not acted upon by the calling program > may not be received again. This means poll and select are currently not > consistend about the socket still being writable after a connect failure. > The first call to poll or select would signal the socket as writable, but > not any following call. The first call consumes the FD_CONNECT and FD_CLOSE > events, regardless of the event mask supplied by the calling program. So > even if the calling program does not care about writability in the first > call, the events are consumed and following calls checking for writability > will not be able to detect a connection failure. > [...] > As far as I understand calling poll and/or select should not change/reset > the socket readyness state, therefore I created a simple fix which could be > used to solve this issue. Attached you will find a suggested patch to make > sure poll and select always signal writability of a connection failed > socket. With this patch applied the above example command failed with a > "Connection refused" as expected. > > This patch only fixes the behaviour regarding connection failure (during > FD_CONNECT), I am not sure if connection closure (during FD_CLOSE) is also > affected, but I was not able to find code handling the fact that FD_CLOSE is > only signalled once. > > Please take a look and thanks in advance!
Thanks for the patch. I pushed it. But then I got second thoughts in terms of how to fix the issue. The reason is that the FD_CLOSE problem shouldn't exist, simply for the fact that we never remove FD_CLOSE from the events mask, see https://sourceware.org/git/?p=newlib-cygwin.git;a=blob;f=winsup/cygwin/fhandler_socket_inet.cc;hb=HEAD#l377 So, rather than setting FD_WRITE at some later point in the code, what about handling this where the other FD_CONNECT stuff is handled, by not erasing the FD_CONNECT bit, just like with FD_CLOSE? diff --git a/winsup/cygwin/fhandler_socket_inet.cc b/winsup/cygwin/fhandler_socket_inet.cc index e5b0d2d1443e..b64d96225db1 100644 --- a/winsup/cygwin/fhandler_socket_inet.cc +++ b/winsup/cygwin/fhandler_socket_inet.cc @@ -354,7 +354,12 @@ fhandler_socket_wsock::evaluate_events (const long event_mask, long &events, } else wsock_events->events |= FD_WRITE; - wsock_events->events &= ~FD_CONNECT; + /* Since FD_CONNECT is only given once, we have to keep FD_CONNECT + for connection failed sockets to have consistent behaviour in + programs calling poll/select multiple times. Example test to + non-listening port: curl -v 127.0.0.1:47 */ + if (connect_state () != connect_failed) + wsock_events->events &= ~FD_CONNECT; wsock_events->connect_errorcode = 0; } /* This test makes accept/connect behave as on Linux when accept/connect @@ -376,12 +381,6 @@ fhandler_socket_wsock::evaluate_events (const long event_mask, long &events, if (erase) wsock_events->events &= ~(events & ~(FD_WRITE | FD_CLOSE)); } - /* Since FD_CONNECT is only given once, we manually need to set - FD_WRITE for connection failed sockets to have consistent - behaviour in programs calling poll/select multiple times. - Example test to non-listening port: curl -v 127.0.0.1:47 */ - if ((connect_state () == connect_failed) && (event_mask & FD_WRITE)) - wsock_events->events |= FD_WRITE; UNLOCK_EVENTS; return ret; What do you think? Thanks, Corinna -- Corinna Vinschen Cygwin Maintainer -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
