I am proposing and planning to start working on the following changes, after discussion and agreement from the other readers of this list.
BACKGROUND: The current implementation, 0.14 and 0.15-CVS, does not properly handle a socket in non-blocking mode. Work was started by Daniel Stenberg and then continued by myself. But this direction was based on adding a new non-blocking function for every existing function. Libssh2 has a hierarchical setup, http://www.libssh2.org/wiki/ index.php/SSH2:Overview . You start with LIBSSH2_SESSION, that owns the socket. Then to LIBSSH2_SESSION you attach a LIBSSH2_CHANNEL to transfer data. Then on the LILBSSH2_CHANNEL you can attach LIBSSH2_SFTP or other protocols. It is also possible to have more then one LIBSSH2_CHANNEL attached to a single LIBSSH2_SESSION. The current functions to control blocking would change blocking in the channel, and change the setting on the socket (LIBSSH2_SESSION). This is clearly wrong. The blocking functions belong at the LIBSSH2_SESSION level, later I will talk about advanced possibilities. PROPOSAL: I propose making libssh2 fully support non-blocking mode all the way down to the LIBSSH2_SESSION level. 1) Move the blocking functions into session.c, and modify the ones in channel.c to call the ones in session.c. 2) Create _libssh2_get_socket_blocking() that will be called by libssh2_session_startup() to try and find the current blocking state of the socket, defaulting to blocking when not sure. 3) The start working from session.c and find all routines that call send(2) and recv(2) and have them return EAGAIN when send(2) or recv (2) returns EAGAIN. But, since the calling routine won't properly support EAGAIN, I will loop on EAGAIN so the code will still work and act as if it were in blocking mode. Currently in session.c, libssh2_banner_send() and libssh2_banner_receive() aren't non-blocking safe. In transport.c, send_existing(), libssh2_packet_write() and libssh2_packet_read() are non-blocking safe, but all callers may not be. For example, from libssh2_session_startup() if (libssh2_banner_send(session)) { /* Unable to send banner? */ libssh2_error(session, LIBSSH2_ERROR_BANNER_SEND, "Error sending banner to remote host", 0); return LIBSSH2_ERROR_BANNER_SEND; } would become while ((rc = libssh2_banner_send(session)) == EAGAIN) { libssh2_waitsocket(session, LIBSSH2_READ_TIMEOUT); } if (rc) { /* Unable to send banner? */ libssh2_error(session, LIBSSH2_ERROR_BANNER_SEND, "Error sending banner to remote host", 0); return LIBSSH2_ERROR_BANNER_SEND; } If the socket wasn't in non-blocking mode, EAGAIN is not a valid return value so the while wouldn't loop. There are also many places that libssh2_channel_get_blocking()/ libssh2_channel_set_blocking() pairs were added to the code. But, since all channels share a single LIBSSH2_SESSION this is wrong. These need to be removed and temporarily replaced with "while ((rc = libssh2_*(session)) == EAGAIN){libssh2_waitsocket(session, LIBSSH2_READ_TIMEOUT);}" loops. 4) After all the lowest level routines can return EAGAIN, move up to the next set of routines and continue until there are no more functions that have "while ((rc = libssh2_*(session)) == EAGAIN) {libssh2_waitsocket(session, LIBSSH2_READ_TIMEOUT);}" code. There are some external functions, and probably some internal ones too, that don't return a numerical value, but return a structure. For example, libssh2_sftp_open_ex() returns a LIBSSH2_SFTP_HANDLE. I think the current functions should operate in a blocking mode and loop on EAGAIN when necessary and create a second non-blocking version. This will keep the API consistent and only add a few new functions. The list is small, not including the defined short cut functions of these. LIBSSH2_API LIBSSH2_SESSION *libssh2_session_init_ex() LIBSSH2_API LIBSSH2_CHANNEL *libssh2_channel_open_ex(); LIBSSH2_API LIBSSH2_CHANNEL *libssh2_channel_direct_tcpip_ex(); LIBSSH2_API LIBSSH2_LISTENER *libssh2_channel_forward_listen_ex(); LIBSSH2_API LIBSSH2_CHANNEL *libssh2_channel_forward_accept(); LIBSSH2_API LIBSSH2_CHANNEL *libssh2_scp_recv(); LIBSSH2_API LIBSSH2_CHANNEL *libssh2_scp_send_ex(); LIBSSH2_API LIBSSH2_PUBLICKEY *libssh2_publickey_init(); LIBSSH2_API LIBSSH2_SFTP *libssh2_sftp_init(); LIBSSH2_API LIBSSH2_SFTP_HANDLE *libssh2_sftp_open_ex(); ADVANCED: After the above work is all done it would be possible to add code, maybe a lot, into the channel functions to allow channels to simulate blocking by looping when the LIBSSH2_SESSION is non-blocking. I am not sure why you would want some blocking and others not. But this could be done, not that I am recommending it. Comments wanted from all. Jim -- /"\ ASCII Ribbon Campaign . \ / - NO HTML/RTF in e-mail . 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