libssh2

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/* Copyright (C) Simon Josefsson
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms,
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 * with or without modification, are permitted provided
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 * that the following conditions are met:
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 *
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 *   Redistributions of source code must retain the above
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 *   copyright notice, this list of conditions and the
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 *   following disclaimer.
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 *
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 *   Redistributions in binary form must reproduce the above
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 *   copyright notice, this list of conditions and the following
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 *   disclaimer in the documentation and/or other materials
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 *   provided with the distribution.
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 *
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 *   Neither the name of the copyright holder nor the names
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 *   of any other contributors may be used to endorse or
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 *   promote products derived from this software without
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 *   specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
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 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
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 * OF SUCH DAMAGE.
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 *
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 * SPDX-License-Identifier: BSD-3-Clause
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 */
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#include "libssh2_priv.h"
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#include "transport.h" /* _libssh2_transport_write */
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/* Keep-alive stuff. */
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LIBSSH2_API void
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libssh2_keepalive_config(LIBSSH2_SESSION *session,
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                         int want_reply,
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                         unsigned int interval)
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{
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    if(interval == 1)
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        session->keepalive_interval = 2;
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    else
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        session->keepalive_interval = interval;
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    session->keepalive_want_reply = want_reply ? 1 : 0;
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}
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LIBSSH2_API int
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libssh2_keepalive_send(LIBSSH2_SESSION *session,
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                       int *seconds_to_next)
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{
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    time_t now;
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    if(!session->keepalive_interval) {
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        if(seconds_to_next)
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            *seconds_to_next = 0;
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        return 0;
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    }
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    now = time(NULL);
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    if(session->keepalive_last_sent + session->keepalive_interval <= now) {
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        /* Format is
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           "SSH_MSG_GLOBAL_REQUEST || 4-byte len || str || want-reply". */
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        unsigned char keepalive_data[]
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            = "\x50\x00\x00\x00\x15keepalive@libssh2.orgW";
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        size_t len = sizeof(keepalive_data) - 1;
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        int rc;
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        keepalive_data[len - 1] =
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            (unsigned char)session->keepalive_want_reply;
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        rc = _libssh2_transport_send(session, keepalive_data, len, NULL, 0);
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        /* Silently ignore PACKET_EAGAIN here: if the write buffer is
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           already full, sending another keepalive is not useful. */
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        if(rc && rc != LIBSSH2_ERROR_EAGAIN) {
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            _libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
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                           "Unable to send keepalive message");
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            return rc;
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        }
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        session->keepalive_last_sent = now;
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        if(seconds_to_next)
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            *seconds_to_next = session->keepalive_interval;
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    }
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    else if(seconds_to_next) {
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        *seconds_to_next = (int) (session->keepalive_last_sent - now)
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            + session->keepalive_interval;
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    }
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    return 0;
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}
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