If you get SSL_ERROR_WANT_WRITE, call the same function with the same parameters and same buffer content immediately. (Same with SSL_ERROR_WANT_READ.)
If you need to, stash those parameters in variables for ease of reference. But don't do anything else on the SSL layer until you get a different return value. (If you implement your own BIO layer, do what you need to do in support of what you're asked to do for the raw I/O. But don't do anything with the SSL layer until its internal state has moved past the need to read or write to or from the BIO.) -Kyle H On Thu, Dec 10, 2020, 09:14 Cosmin Apreutesei <cosmin.apreute...@gmail.com> wrote: > Hello, > > I have a question regarding SSL_write() and returning SSL_ERROR_WANT_WRITE > from the write callback. > > _After_ SSL_write() returns with SSL_ERROR_WANT_WRITE (because my write > callback returned SSL_ERROR_WANT_WRITE), can I _then_ send the data given > to the calback and then call SSL_write() again (with the same arguments) > and then in the second call to the callback return the number of bytes > written? Is that a supported use of the API? (I'm asking because that's the > only way I can use the API, I can't send the data inside the callback, I > need to send it outside the callback, see below for why). > > In other words, is it guaranteed that on that second call to SSL_write(), > SSL will want to send the exact same data that it tried before when it > failed, and not change its mind about it wants to send? Because > technically, since SSL_ERROR_WANT_WRITE implies that "no data was sent", > the state machine might as well advance and send something different at a > later time (because it received data or something inside expired or > whatever). > > ---- > > Why I need this: I'm using IOCP and LuaJIT which means I have two > limitations: > > 1) Because I'm using a completion API as opposed to a readiness API, I > can't just tell OpenSSL when the socket is writable and let it write to it, > I need to write the data myself. > > 2) because LuaJIT doesn't allow me to yield from inside a C callback, I > can't do async I/O inside the callback, I can only do it in between calls > to SSL_read()/SSL_write(). > > Any suggestions appreciated, thanks! > >
