fixes #523 dialers could support multiple outstanding dial requests

fixes #179 DNS resolution should be done at connect time
fixes #586 Windows IO completion port work could be better
fixes #339 Windows iocp could use synchronous completions
fixes #280 TCP abstraction improvements

This is a rather monstrous set of changes, which refactors TCP, and
the underlying Windows I/O completion path logic, in order to obtain
a cleaner, simpler API, with support for asynchronous DNS lookups performed
on connect rather than initialization time, the ability to have multiple
connects or accepts pending, as well as fewer extraneous function calls.

The Windows code also benefits from greatly reduced context switching,
fewer lock operations performed, and a reduced number of system calls
on the hot code path.  (We use automatic event resetting instead of manual.)

Some dead code was removed as well, and a few potential edge case leaks
on failure paths (in the websocket code) were plugged.

Note that all TCP based transports benefit from this work. The IPC code
on Windows still uses the legacy IOCP for now, as does the UDP code (used
for ZeroTier.)  We will be converting those soon too.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/core/aio.c b/src/core/aio.c
index c8517b9b..40638bce 100644
--- a/src/core/aio.c
+++ b/src/core/aio.c
@@ -378,8 +378,10 @@ nni_aio_schedule(nni_aio *aio, nni_aio_cancelfn cancelfn, void *data)
 		return (NNG_ECLOSED);
 	}
 
+	NNI_ASSERT(aio->a_prov_cancel == NULL);
 	aio->a_prov_cancel = cancelfn;
 	aio->a_prov_data   = data;
+
 	if (aio->a_expire != NNI_TIME_NEVER) {
 		nni_aio_expire_add(aio);
 	}