Hi,
Am 19.06.2018 um 20:39 schrieb Christian Helmuth:
Hello,
On Tue, Jun 19, 2018 at 08:14:07PM +0200, Johannes Kliemann wrote:
So having at least MSG_DONTWAIT would be quite helpful. But I think the general problem is the API. Having a native asynchronous TCP or IP session with a native TCP/IP stack would be the best case but I assume this won't happen soon. But also an asynchronous (or at least more compatible) approach using libc would already be useful (and potentially resolve the need for any recv flags ;) ).
So currently I need some flags but I would happily switch to a generally better approach if there is one.
I see two prominent directions we could explore. First on the libc level, you may use select() with a zero timeout for polling file descriptors and only read() if data is available. This option leaves us with the question, when to poll.
This is what I currently do but with ioctl(int, FIONREAD, int*) which gives the number of bytes available to read from a socket.
The second option may be a deeper look into Emery's current lwip port which removes the socket API level and provides the low-level functions, which should be non-blocking.
I will look into that, thanks.
There's also a third option in libc/select.h, which provides a mechanism to block in the entrypoint waiting for signals, RPC, and also for libc file descriptors to become readable. The semantics are a bit tricky, but I know of applications out there using this mechanism successfully.
I also might look into this while I still prefer a non-blocking approach.
Thanks for your help, Johannes