src/session.c - master - niceSOFT/libssh2

src/session.c
1 799 строк57 KB
Viktor Szakats
src: bump `ssh2_time_t`/`ssh2_timediff_t` resolution from milliseconds to microseconds
03 авг 2026, 03:03
03 авг 2026, 03:03c97959e
/* Copyright (C) Sara Golemon <sarag@libssh2.org>
 * Copyright (C) Daniel Stenberg
 * Copyright (C) Simon Josefsson <simon@josefsson.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include "libssh2_priv.h"

#ifdef _WIN32
#include <ws2tcpip.h>  /* for socklen_t */
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include <stdlib.h>
#include <fcntl.h>

#include "transport.h"
#include "session.h"
#include "channel.h"
#include "mac.h"

#ifdef _WIN32
#define libssh2_usec_t long
#elif defined(__APPLE__)
#define libssh2_usec_t suseconds_t
#else
#undef libssh2_usec_t
#endif

#define SSH2_DEFAULT_READ_TIMEOUT 60 /* generic timeout in seconds used when
                                        waiting for more data to arrive */

/* ssh2_default_alloc */
static LIBSSH2_ALLOC_FUNC(ssh2_default_alloc)
{
    (void)abstract;
    return malloc(count);
}

/* ssh2_default_free */
static LIBSSH2_FREE_FUNC(ssh2_default_free)
{
    (void)abstract;
    free(ptr);
}

/* ssh2_default_realloc */
static LIBSSH2_REALLOC_FUNC(ssh2_default_realloc)
{
    (void)abstract;
    return realloc(ptr, count);
}

/*
 * Wait for a hello from the remote host
 * Allocate a buffer and store the banner in session->remote.banner
 * Returns: 0 on success, LIBSSH2_ERROR_EAGAIN if read would block, negative
 * on failure
 */
static int session_banner_receive(LIBSSH2_SESSION *session)
{
    ssize_t ret;
    size_t banner_len;

    if(session->banner_TxRx_state == ssh2_NB_state_idle) {
        banner_len = 0;

        session->banner_TxRx_state = ssh2_NB_state_created;
    }
    else
        banner_len = session->banner_TxRx_total_send;

    while(banner_len < sizeof(session->banner_TxRx_banner) &&
          (banner_len == 0 ||
           session->banner_TxRx_banner[banner_len - 1] != '\n')) {
        char c = '\0';

        /* no incoming block yet! */
        session->socket_block_directions &= ~LIBSSH2_SESSION_BLOCK_INBOUND;

        ret = SSH2_RECV(session, &c, 1, SSH2_SOCKET_RECV_FLAGS(session));
        if(ret < 0) {
            if(session->api_block_mode || (ret != -EAGAIN))
                /* ignore EAGAIN when non-blocking */
                ssh2_deb((session, LIBSSH2_TRACE_SOCKET,
                          "Error recving %d bytes: %ld", 1, (long)-ret));
        }
        else
            ssh2_deb((session, LIBSSH2_TRACE_SOCKET, "Recved %ld bytes banner",
                      (long)ret));

        if(ret < 0) {
            if(ret == -EAGAIN) {
                session->socket_block_directions =
                    LIBSSH2_SESSION_BLOCK_INBOUND;
                session->banner_TxRx_total_send = banner_len;
                return LIBSSH2_ERROR_EAGAIN;
            }

            /* Some kinda error */
            session->banner_TxRx_state = ssh2_NB_state_idle;
            session->banner_TxRx_total_send = 0;
            return LIBSSH2_ERROR_SOCKET_RECV;
        }

        if(ret == 0) {
            session->socket_state = SSH2_SOCKET_DISCONNECTED;
            return LIBSSH2_ERROR_SOCKET_DISCONNECT;
        }

        if((c == '\r' || c == '\n') && banner_len == 0)
            continue;

        if(c == '\0') {
            /* NULLs are not allowed in SSH banners */
            session->banner_TxRx_state = ssh2_NB_state_idle;
            session->banner_TxRx_total_send = 0;
            return LIBSSH2_ERROR_BANNER_RECV;
        }

        session->banner_TxRx_banner[banner_len++] = c;
    }

    while(banner_len &&
          (session->banner_TxRx_banner[banner_len - 1] == '\n' ||
           session->banner_TxRx_banner[banner_len - 1] == '\r'))
        banner_len--;

    /* From this point on, we are done here */
    session->banner_TxRx_state = ssh2_NB_state_idle;
    session->banner_TxRx_total_send = 0;

    if(!banner_len)
        return LIBSSH2_ERROR_BANNER_RECV;

    if(session->remote.banner)
        SSH2_FREE(session, session->remote.banner);

    session->remote.banner = SSH2_ALLOC(session, banner_len + 1);
    if(!session->remote.banner)
        return ssh2_err(session, LIBSSH2_ERROR_ALLOC,
                        "Error allocating space for remote banner");

    memcpy(session->remote.banner, session->banner_TxRx_banner, banner_len);
    session->remote.banner[banner_len] = '\0';
    ssh2_deb((session, LIBSSH2_TRACE_TRANS, "Received Banner: %s",
              session->remote.banner));
    return LIBSSH2_ERROR_NONE;
}

/*
 * Send the default banner, or the one set via libssh2_session_banner_set()
 *
 * Returns LIBSSH2_ERROR_EAGAIN if it would block - and if it does so, you
 * should call this function again as soon as it is likely that more data can
 * be sent, and this function should then be called with the same argument set
 * (same data pointer and same data_len) until zero or failure is returned.
 */
static int session_banner_send(LIBSSH2_SESSION *session)
{
    const char *banner = LIBSSH2_SSH_DEFAULT_BANNER_WITH_CRLF;
    size_t banner_len = sizeof(LIBSSH2_SSH_DEFAULT_BANNER_WITH_CRLF) - 1;
    ssize_t ret;

    if(session->banner_TxRx_state == ssh2_NB_state_idle) {
        if(session->local.banner) {
            /* setopt_string has given us our \r\n characters */
            banner_len = strlen(session->local.banner);
            banner = session->local.banner;
        }
#ifdef LIBSSH2DEBUG
        {
            char banner_dup[256];

            /* Hack and slash to avoid sending CRLF in debug output */
            if(banner_len < 256) {
                memcpy(banner_dup, banner, banner_len - 2);
                banner_dup[banner_len - 2] = '\0';
            }
            else {
                memcpy(banner_dup, banner, 255);
                banner_dup[255] = '\0';
            }

            ssh2_deb((session, LIBSSH2_TRACE_TRANS, "Sending Banner: %s",
                      banner_dup));
        }
#endif

        session->banner_TxRx_state = ssh2_NB_state_created;
    }

    /* no outgoing block yet! */
    session->socket_block_directions &= ~LIBSSH2_SESSION_BLOCK_OUTBOUND;

    ret = SSH2_SEND(session, banner + session->banner_TxRx_total_send,
                    banner_len - session->banner_TxRx_total_send,
                    SSH2_SOCKET_SEND_FLAGS(session));
    if(ret < 0)
        ssh2_deb((session, LIBSSH2_TRACE_SOCKET,
                  "Error sending %ld bytes: %ld",
                  (long)(banner_len - session->banner_TxRx_total_send),
                  (long)-ret));
    else
        ssh2_deb((session, LIBSSH2_TRACE_SOCKET,
                  "Sent %ld/%ld bytes at %p+%ld", (long)ret,
                  (long)(banner_len - session->banner_TxRx_total_send),
                  (const void *)banner,
                  (long)session->banner_TxRx_total_send));

    if(ret != (ssize_t)(banner_len - session->banner_TxRx_total_send)) {
        if(ret >= 0 || ret == -EAGAIN) {
            /* the whole packet could not be sent, save the what was */
            session->socket_block_directions = LIBSSH2_SESSION_BLOCK_OUTBOUND;
            if(ret > 0)
                session->banner_TxRx_total_send += ret;
            return LIBSSH2_ERROR_EAGAIN;
        }
        session->banner_TxRx_state = ssh2_NB_state_idle;
        session->banner_TxRx_total_send = 0;
        return LIBSSH2_ERROR_SOCKET_RECV;
    }

    /* Set the state back to idle */
    session->banner_TxRx_state = ssh2_NB_state_idle;
    session->banner_TxRx_total_send = 0;

    return 0;
}

/*
 * session_nonblock() sets the given socket to either blocking or
 * non-blocking mode based on the 'nonblock' boolean argument. This function
 * is copied from the libcurl sources with permission.
 */
static int session_nonblock(libssh2_socket_t sockfd,   /* operate on this */
                            int nonblock /* TRUE or FALSE */ )
{
#ifdef HAVE_O_NONBLOCK  /* most recent unix versions */
    int flags = fcntl(sockfd, F_GETFL, 0);
    if(nonblock)
        return fcntl(sockfd, F_SETFL, flags | O_NONBLOCK);
    else
        return fcntl(sockfd, F_SETFL, flags & (~O_NONBLOCK));
#elif defined(HAVE_FIONBIO)  /* older unix versions and VMS */
    int flags = nonblock;
    return ioctl(sockfd, FIONBIO, &flags);
#elif defined(HAVE_IOCTLSOCKET_CASE)  /* presumably for Amiga */
    return IoctlSocket(sockfd, FIONBIO, (long)nonblock);
#elif defined(HAVE_SO_NONBLOCK)  /* BeOS */
    long b = nonblock ? 1 : 0;
    return setsockopt(sockfd, SOL_SOCKET, SO_NONBLOCK, &b, sizeof(b));
#elif defined(_WIN32)
    unsigned long flags = nonblock;
    return ioctlsocket(sockfd, FIONBIO, &flags);
#else
    (void)sockfd;
    (void)nonblock;
    return 0;                   /* returns success */
#endif
}

/*
 * gets the given blocking or non-blocking state of the socket.
 */
static int session_get_socket_nonblocking(libssh2_socket_t sockfd)
{                                 /* operate on this */
#ifdef HAVE_O_NONBLOCK  /* most recent unix versions */
    int flags = fcntl(sockfd, F_GETFL, 0);
    if(flags == -1)
        return 1;  /* Assume blocking on error */
    return (flags & O_NONBLOCK);
#elif defined(HAVE_SO_NONBLOCK)  /* BeOS */
    long b;
    if(getsockopt(sockfd, SOL_SOCKET, SO_NONBLOCK, &b, sizeof(b)))
        return 1;  /* Assume blocking on error */
    return (int)b;
#elif defined(SO_STATE) && defined(__VMS)  /* VMS TCP/IP Services */
    size_t sockstat = 0;
    int callstat = 0;
    size_t size = sizeof(int);
    callstat = getsockopt(sockfd, SOL_SOCKET, SO_STATE,
                          (char *)&sockstat, &size);
    if(callstat == -1)
        return 0;
    if((sockstat & SS_NBIO) != 0)
        return 1;
    return 0;
#elif defined(_WIN32)
    unsigned int option_value;
    socklen_t option_len = sizeof(option_value);

    if(getsockopt(sockfd, SOL_SOCKET, SO_ERROR,
                  (void *)&option_value, &option_len))
        return 1;  /* Assume blocking on error */
    return (int)option_value;
#else
    (void)sockfd;
    return 1;                   /* returns blocking */
#endif
}

/*
 * Set the local banner to use in the server handshake.
 */
int libssh2_session_banner_set(LIBSSH2_SESSION *session, const char *banner)
{
    size_t banner_len;

    if(!session)
        return LIBSSH2_ERROR_BAD_USE;

    banner_len = banner ? strlen(banner) : 0;

    if(banner_len > (4 * 1024 * 1024))
        return LIBSSH2_ERROR_OUT_OF_BOUNDARY;

    if(session->local.banner)
        SSH2_SAFEFREE(session, session->local.banner);

    if(!banner || !banner_len)
        return 0;

    session->local.banner = SSH2_ALLOC(session, banner_len + 3);
    if(!session->local.banner)
        return ssh2_err(session, LIBSSH2_ERROR_ALLOC,
                        "Unable to allocate memory for local banner");

    memcpy(session->local.banner, banner, banner_len);

    /* first null-terminate like this so that the debug output is nice */
    session->local.banner[banner_len] = '\0';
    ssh2_deb((session, LIBSSH2_TRACE_TRANS, "Setting local Banner: %s",
              session->local.banner));
    session->local.banner[banner_len++] = '\r';
    session->local.banner[banner_len++] = '\n';
    session->local.banner[banner_len] = '\0';

    return 0;
}

#ifndef LIBSSH2_NO_DEPRECATED
/*
 * Set the local banner. DEPRECATED VERSION
 */
int libssh2_banner_set(LIBSSH2_SESSION *session, const char *banner)
{
    return libssh2_session_banner_set(session, banner);
}
#endif

/*
 * Allocate and initialize a libssh2 session structure. Allows for malloc
 * callbacks in case the calling program has its own memory manager. It is
 * allowable (but unadvisable) to define some but not all of the malloc
 * callbacks An additional pointer value may be optionally passed to be sent
 * to the callbacks (so they know who's asking)
 */
LIBSSH2_SESSION *libssh2_session_init_ex(LIBSSH2_ALLOC_FUNC(*my_alloc),
                                         LIBSSH2_FREE_FUNC(*my_free),
                                         LIBSSH2_REALLOC_FUNC(*my_realloc),
                                         void *abstract)
{
    LIBSSH2_ALLOC_FUNC(*local_alloc) = ssh2_default_alloc;
    LIBSSH2_FREE_FUNC(*local_free) = ssh2_default_free;
    LIBSSH2_REALLOC_FUNC(*local_realloc) = ssh2_default_realloc;
    LIBSSH2_SESSION *session;

    if(my_alloc)
        local_alloc = my_alloc;
    if(my_free)
        local_free = my_free;
    if(my_realloc)
        local_realloc = my_realloc;

    session = local_alloc(sizeof(LIBSSH2_SESSION), &abstract);
    if(session) {
        memset(session, 0, sizeof(LIBSSH2_SESSION));
        session->alloc = local_alloc;
        session->free = local_free;
        session->realloc = local_realloc;
        session->send = ssh2_send;
        session->recv = ssh2_recv;
        session->abstract = abstract;
        session->api_timeout_ms = 0; /* timeout-free API by default */
        session->api_block_mode = 1; /* blocking API by default */
        session->state = SSH2_STATE_INITIAL_KEX;
        session->fullpacket_required_type = 0;
        session->packet_read_timeout =
            ssh2_sec_to_timediff(SSH2_DEFAULT_READ_TIMEOUT);
        session->flag.quote_paths = 1; /* default behavior is to quote paths
                                          for the scp subsystem */
        session->kex = NULL;
        ssh2_deb((session, LIBSSH2_TRACE_TRANS,
                  "New session resource allocated"));
        ssh2_init_if_needed();
    }
    return session;
}

/*
 * Set (or reset) a callback function
 * Returns the prior address
 */
#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wcast-function-type"
#endif
libssh2_cb_generic *libssh2_session_callback_set2(LIBSSH2_SESSION *session,
                                                  int cbtype,
                                                  libssh2_cb_generic *callback)
{
    libssh2_cb_generic *oldcb;

    if(!session)
        return NULL;

    switch(cbtype) {
    case LIBSSH2_CALLBACK_IGNORE:
        oldcb = (libssh2_cb_generic *)session->ssh_msg_ignore;
        session->ssh_msg_ignore = (LIBSSH2_IGNORE_FUNC(*))callback;
        return oldcb;

    case LIBSSH2_CALLBACK_DEBUG:
        oldcb = (libssh2_cb_generic *)session->ssh_msg_debug;
        session->ssh_msg_debug = (LIBSSH2_DEBUG_FUNC(*))callback;
        return oldcb;

    case LIBSSH2_CALLBACK_DISCONNECT:
        oldcb = (libssh2_cb_generic *)session->ssh_msg_disconnect;
        session->ssh_msg_disconnect = (LIBSSH2_DISCONNECT_FUNC(*))callback;
        return oldcb;

    case LIBSSH2_CALLBACK_MACERROR:
        oldcb = (libssh2_cb_generic *)session->macerror;
        session->macerror = (LIBSSH2_MACERROR_FUNC(*))callback;
        return oldcb;

    case LIBSSH2_CALLBACK_X11:
        oldcb = (libssh2_cb_generic *)session->x11;
        session->x11 = (LIBSSH2_X11_OPEN_FUNC(*))callback;
        return oldcb;

    case LIBSSH2_CALLBACK_SEND:
        oldcb = (libssh2_cb_generic *)session->send;
        session->send = (LIBSSH2_SEND_FUNC(*))callback;
        return oldcb;

    case LIBSSH2_CALLBACK_RECV:
        oldcb = (libssh2_cb_generic *)session->recv;
        session->recv = (LIBSSH2_RECV_FUNC(*))callback;
        return oldcb;

    case LIBSSH2_CALLBACK_AUTHAGENT:
        oldcb = (libssh2_cb_generic *)session->authagent;
        session->authagent = (LIBSSH2_AUTHAGENT_FUNC(*))callback;
        return oldcb;

    case LIBSSH2_CALLBACK_AUTHAGENT_IDENTITIES:
        oldcb = (libssh2_cb_generic *)session->addLocalIdentities;
        session->addLocalIdentities = (LIBSSH2_ADD_IDENTITIES_FUNC(*))callback;
        return oldcb;

    case LIBSSH2_CALLBACK_AUTHAGENT_SIGN:
        oldcb = (libssh2_cb_generic *)session->agentSignCallback;
        session->agentSignCallback = (LIBSSH2_AUTHAGENT_SIGN_FUNC(*))callback;
        return oldcb;
    }
    ssh2_deb((session, LIBSSH2_TRACE_TRANS, "Unrecognized callback type %d",
              cbtype));

    return NULL;
}
#ifdef __clang__
#pragma clang diagnostic pop
#endif

/*
 * DEPRECATED, DO NOT USE!
 *
 * Set (or reset) a callback function
 * Returns the prior address
 *
 * ALERT: this function relies on that we can typecast function pointers
 * to void pointers, which is not allowed in ISO C!
 */
#ifdef _MSC_VER
#pragma warning(push)
/* 'type cast': from data pointer to function pointer */
#pragma warning(disable:4054)
/* 'type cast': from function pointer to data pointer */
#pragma warning(disable:4055)
#else
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wpedantic"
#endif
void *libssh2_session_callback_set(LIBSSH2_SESSION *session,
                                   int cbtype, void *callback)
{
    return (void *)libssh2_session_callback_set2(session, cbtype,
                                               (libssh2_cb_generic *)callback);
}
#ifdef _MSC_VER
#pragma warning(pop)
#else
#pragma GCC diagnostic pop
#endif

/*
 * Utility function that waits for action on the socket. Returns 0 when ready
 * to run again or error on timeout.
 */
int ssh2_wait_socket(LIBSSH2_SESSION *session, ssh2_time_t start_time)
{
    int rc;
    int seconds_to_next;
    int dir;
    int has_timeout;
    ssh2_timediff_t time_to_next = 0;
    ssh2_timediff_t elapsed_time;
    ssh2_timediff_t api_timeout = ssh2_ms_to_timediff(session->api_timeout_ms);

    /* since libssh2 often sets EAGAIN internally before this function is
       called, we can decrease some amount of confusion in user programs by
       resetting the error code in this function to reduce the risk of EAGAIN
       being stored as error when a blocking function has returned */
    session->err_code = LIBSSH2_ERROR_NONE;

    rc = libssh2_keepalive_send(session, &seconds_to_next);
    if(rc)
        return rc;

    time_to_next = ssh2_sec_to_timediff(seconds_to_next);

    /* figure out what to wait for */
    dir = libssh2_session_block_directions(session);
    if(!dir) {
        ssh2_deb((session, LIBSSH2_TRACE_SOCKET,
                  "Nothing to wait for in wait_socket"));
        /* To avoid that we hang below because there is nothing set to
           wait for, we timeout on 1 second to also avoid busy-looping
           during this condition */
        time_to_next = ssh2_ms_to_timediff(1000);
    }

    if(api_timeout > 0 &&
       (seconds_to_next == 0 || time_to_next > api_timeout)) {
        ssh2_time_t now = ssh2_now();
        elapsed_time = now > start_time ? (now - start_time) : 0;
        if(elapsed_time > api_timeout)
            return ssh2_err(session, LIBSSH2_ERROR_TIMEOUT,
                            "API timeout expired");

        time_to_next = api_timeout - elapsed_time;
        has_timeout = 1;
    }
    else if(time_to_next > 0)
        has_timeout = 1;
    else
        has_timeout = 0;

#ifdef HAVE_POLL
    {
        ssh2_timediff_t time_to_next_ms = ssh2_timediff_to_ms(time_to_next);
        struct pollfd sockets[1];

        sockets[0].fd = session->socket_fd;
        sockets[0].events = 0;
        sockets[0].revents = 0;

        if(dir & LIBSSH2_SESSION_BLOCK_INBOUND)
            sockets[0].events |= POLLIN;

        if(dir & LIBSSH2_SESSION_BLOCK_OUTBOUND)
            sockets[0].events |= POLLOUT;

        rc = poll(sockets, 1,
                  has_timeout ? (int)SSH2_MIN(time_to_next_ms, INT_MAX) : -1);
    }
#else
    {
        fd_set rfd;
        fd_set wfd;
        fd_set *writefd = NULL;
        fd_set *readfd = NULL;
        struct timeval tv;
        tv.tv_sec = (long)ssh2_timediff_to_sec(time_to_next);
#ifdef libssh2_usec_t
        tv.tv_usec = (libssh2_usec_t)ssh2_timediff_to_usec(time_to_next);
#else
        tv.tv_usec = ssh2_timediff_to_usec(time_to_next);
#endif

        if(dir & LIBSSH2_SESSION_BLOCK_INBOUND) {
            FD_ZERO(&rfd);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
            FD_SET(session->socket_fd, &rfd);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif
            readfd = &rfd;
        }

        if(dir & LIBSSH2_SESSION_BLOCK_OUTBOUND) {
            FD_ZERO(&wfd);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
            FD_SET(session->socket_fd, &wfd);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif
            writefd = &wfd;
        }

        rc = select((int)(session->socket_fd + 1), readfd, writefd, NULL,
                    has_timeout ? &tv : NULL);
    }
#endif
    if(rc == 0)
        return ssh2_err(session, LIBSSH2_ERROR_TIMEOUT,
                        "Timed out waiting on socket");

    if(rc < 0) {
        /* Profiling tools that use SIGPROF can cause EINTR responses.
           poll() / select() do not set any descriptor states on EINTR,
           but some fds may be ready, so the caller should try again */
        if(SSH2_ERRNO() == EINTR)
            return 0;

        return ssh2_err(session, LIBSSH2_ERROR_TIMEOUT,
                        "Error waiting on socket");
    }

    return 0; /* ready to try again */
}

static int session_startup(LIBSSH2_SESSION *session, libssh2_socket_t sock)
{
    int rc;

    if(!session)
        return LIBSSH2_ERROR_BAD_USE;

    if(session->startup_state == ssh2_NB_state_idle) {
        ssh2_deb((session, LIBSSH2_TRACE_TRANS,
                  "session_startup for socket %ld", (long)sock));
        if(LIBSSH2_INVALID_SOCKET == sock)  /* Did we forget something? */
            return ssh2_err(session, LIBSSH2_ERROR_BAD_SOCKET,
                            "Bad socket provided");

        session->socket_fd = sock;

        session->socket_prev_blockstate =
            !session_get_socket_nonblocking(session->socket_fd);

        if(session->socket_prev_blockstate) {
            /* If in blocking state change to non-blocking */
            rc = session_nonblock(session->socket_fd, 1);
            if(rc)
                return ssh2_err(session, rc,
                                "Failed changing socket's "
                                "blocking state to non-blocking");
        }

        session->startup_state = ssh2_NB_state_created;
    }

    if(session->startup_state == ssh2_NB_state_created) {
        rc = session_banner_send(session);
        if(rc == LIBSSH2_ERROR_EAGAIN)
            return rc;
        else if(rc)
            return ssh2_err(session, rc, "Failed sending banner");

        session->startup_state = ssh2_NB_state_sent;
        session->banner_TxRx_state = ssh2_NB_state_idle;
    }

    if(session->startup_state == ssh2_NB_state_sent) {
        do {
            rc = session_banner_receive(session);
            if(rc == LIBSSH2_ERROR_EAGAIN)
                return rc;
            else if(rc)
                return ssh2_err(session, rc, "Failed getting banner");
        } while(strncmp("SSH-", session->remote.banner, 4));

        session->startup_state = ssh2_NB_state_sent1;
    }

    if(session->startup_state == ssh2_NB_state_sent1) {
        rc = ssh2_kex_exchange(session, 0, &session->startup_key_state);
        if(rc == LIBSSH2_ERROR_EAGAIN)
            return rc;
        else if(rc)
            return ssh2_err(session, rc, "Unable to exchange encryption keys");

        session->startup_state = ssh2_NB_state_sent2;
    }

    if(session->startup_state == ssh2_NB_state_sent2) {
        ssh2_deb((session, LIBSSH2_TRACE_TRANS,
                  "Requesting userauth service"));

        /* Request the userauth service */
        session->startup_service[0] = SSH_MSG_SERVICE_REQUEST;
        ssh2_htonu32(session->startup_service + 1, sizeof("ssh-userauth") - 1);
        memcpy(session->startup_service + 5, "ssh-userauth",
               sizeof("ssh-userauth") - 1);

        session->startup_state = ssh2_NB_state_sent3;
    }

    if(session->startup_state == ssh2_NB_state_sent3) {
        rc = ssh2_transport_send(session, session->startup_service,
                                 sizeof("ssh-userauth") + 5 - 1, NULL, 0);
        if(rc == LIBSSH2_ERROR_EAGAIN)
            return rc;
        else if(rc)
            return ssh2_err(session, rc,
                            "Unable to ask for ssh-userauth service");

        session->startup_state = ssh2_NB_state_sent4;
    }

    if(session->startup_state == ssh2_NB_state_sent4) {
        struct string_buf buf;
        rc = ssh2_packet_require(session, SSH_MSG_SERVICE_ACCEPT,
                                 &session->startup_data,
                                 &session->startup_data_len, 0, NULL, 0,
                                 &session->startup_req_state);
        if(rc)
            return ssh2_err(session, rc,
                            "Failed to get response to "
                            "ssh-userauth request");

        buf.data = session->startup_data;
        buf.dataptr = buf.data;
        buf.len = session->startup_data_len;

        /* advance past packet type */
        buf.dataptr++;

        if(ssh2_match_string(&buf, "ssh-userauth")) {
            SSH2_SAFEFREE(session, session->startup_data);
            return ssh2_err(session, LIBSSH2_ERROR_PROTO,
                            "Invalid response received from server");
        }

        session->startup_service_length = (sizeof("ssh-userauth") - 1);

        SSH2_SAFEFREE(session, session->startup_data);

        session->startup_state = ssh2_NB_state_idle;

        return 0;
    }

    /* for safety return some error */
    return LIBSSH2_ERROR_INVAL;
}

/*
 * session: LIBSSH2_SESSION struct allocated and owned by the calling program
 * sock:    *must* be populated with an opened and connected socket.
 *
 * Returns: 0 on success, or non-zero on failure
 */
int libssh2_session_handshake(LIBSSH2_SESSION *session, libssh2_socket_t sock)
{
    int rc;

    if(!session)
        return LIBSSH2_ERROR_BAD_USE;

    BLOCK_ADJUST(rc, session, session_startup(session, sock));

    return rc;
}

#ifndef LIBSSH2_NO_DEPRECATED
/*
 * DEPRECATED. Use libssh2_session_handshake() instead! This function is not
 * portable enough.
 *
 * session: LIBSSH2_SESSION struct allocated and owned by the calling program
 * sock:    *must* be populated with an opened and connected socket.
 *
 * Returns: 0 on success, or non-zero on failure
 */
int libssh2_session_startup(LIBSSH2_SESSION *session, int sock)
{
    return libssh2_session_handshake(session, (libssh2_socket_t)sock);
}
#endif

/*
 * Frees the memory allocated to the session
 * Also closes and frees any channels attached to this session
 */
static int session_free(LIBSSH2_SESSION *session)
{
    int rc;
    struct packet *pkg;
    LIBSSH2_CHANNEL *ch;
    LIBSSH2_LISTENER *l;
    int packets_left = 0;

    if(session->free_state == ssh2_NB_state_idle) {
        ssh2_deb((session, LIBSSH2_TRACE_TRANS, "Freeing session resource %p",
                  (void *)session->remote.banner));

        session->free_state = ssh2_NB_state_created;
    }

    if(session->free_state == ssh2_NB_state_created) {
        /* !checksrc! disable EQUALSNULL 1 */
        while((ch = ssh2_list_first(&session->channels)) != NULL) {
            rc = ssh2_channel_free(ch);
            if(rc == LIBSSH2_ERROR_EAGAIN)
                return rc;
        }

        session->free_state = ssh2_NB_state_sent;
    }

    if(session->free_state == ssh2_NB_state_sent) {
        /* !checksrc! disable EQUALSNULL 1 */
        while((l = ssh2_list_first(&session->listeners)) != NULL) {
            rc = ssh2_channel_forward_cancel(l);
            if(rc == LIBSSH2_ERROR_EAGAIN)
                return rc;
        }

        session->free_state = ssh2_NB_state_sent1;
    }

    if(session->kex && session->kex->cleanup)
        session->kex->cleanup(session,
                              &session->startup_key_state.key_state_low);

    /* hostkey */
    if(session->hostkey && session->hostkey->dtor)
        session->hostkey->dtor(session, &session->server_hostkey_abstract);

    /* Client to Server */
    /* crypt */
    if(session->local.crypt && session->local.crypt->dtor)
        session->local.crypt->dtor(session, &session->local.crypt_abstract);
    /* comp */
    if(session->local.comp && session->local.comp->dtor)
        session->local.comp->dtor(session, 1, &session->local.comp_abstract);
    /* mac */
    if(session->local.mac && session->local.mac->dtor)
        session->local.mac->dtor(session, &session->local.mac_abstract);

    /* Server to Client */
    /* crypt */
    if(session->remote.crypt && session->remote.crypt->dtor)
        session->remote.crypt->dtor(session, &session->remote.crypt_abstract);
    /* comp */
    if(session->remote.comp && session->remote.comp->dtor)
        session->remote.comp->dtor(session, 0, &session->remote.comp_abstract);
    /* mac */
    if(session->remote.mac && session->remote.mac->dtor)
        session->remote.mac->dtor(session, &session->remote.mac_abstract);

    /* session_id */
    if(session->session_id)
        SSH2_FREE(session, session->session_id);

    /* Free banner(s) */
    if(session->remote.banner)
        SSH2_FREE(session, session->remote.banner);
    if(session->local.banner)
        SSH2_FREE(session, session->local.banner);

    /* Free preference(s) */
    if(session->kex_prefs)
        SSH2_FREE(session, session->kex_prefs);
    if(session->hostkey_prefs)
        SSH2_FREE(session, session->hostkey_prefs);

    if(session->local.kexinit)
        SSH2_FREE(session, session->local.kexinit);
    if(session->local.crypt_prefs)
        SSH2_FREE(session, session->local.crypt_prefs);
    if(session->local.mac_prefs)
        SSH2_FREE(session, session->local.mac_prefs);
    if(session->local.comp_prefs)
        SSH2_FREE(session, session->local.comp_prefs);
    if(session->local.lang_prefs)
        SSH2_FREE(session, session->local.lang_prefs);

    if(session->remote.kexinit)
        SSH2_FREE(session, session->remote.kexinit);
    if(session->remote.crypt_prefs)
        SSH2_FREE(session, session->remote.crypt_prefs);
    if(session->remote.mac_prefs)
        SSH2_FREE(session, session->remote.mac_prefs);
    if(session->remote.comp_prefs)
        SSH2_FREE(session, session->remote.comp_prefs);
    if(session->remote.lang_prefs)
        SSH2_FREE(session, session->remote.lang_prefs);
    if(session->server_sign_algorithms)
        SSH2_FREE(session, session->server_sign_algorithms);
    if(session->sign_algo_prefs)
        SSH2_FREE(session, session->sign_algo_prefs);

    /*
     * Make sure all memory used in the state variables are free
     */
    if(session->kexinit_data)
        SSH2_FREE(session, session->kexinit_data);
    if(session->startup_data)
        SSH2_FREE(session, session->startup_data);
    if(session->userauth_list_data)
        SSH2_FREE(session, session->userauth_list_data);
    if(session->userauth_banner)
        SSH2_FREE(session, session->userauth_banner);
    if(session->userauth_pswd_data)
        SSH2_FREE(session, session->userauth_pswd_data);
    if(session->userauth_pswd_newpw)
        SSH2_FREE(session, session->userauth_pswd_newpw);
    if(session->userauth_host_packet)
        SSH2_FREE(session, session->userauth_host_packet);
    if(session->userauth_host_method)
        SSH2_FREE(session, session->userauth_host_method);
    if(session->userauth_host_data)
        SSH2_FREE(session, session->userauth_host_data);
    if(session->userauth_pblc_data)
        SSH2_FREE(session, session->userauth_pblc_data);
    if(session->userauth_pblc_packet)
        SSH2_FREE(session, session->userauth_pblc_packet);
    if(session->userauth_pblc_method)
        SSH2_FREE(session, session->userauth_pblc_method);
    if(session->userauth_kybd_data)
        SSH2_FREE(session, session->userauth_kybd_data);
    if(session->userauth_kybd_packet)
        SSH2_FREE(session, session->userauth_kybd_packet);
    if(session->userauth_kybd_auth_instruction)
        SSH2_FREE(session, session->userauth_kybd_auth_instruction);
    if(session->open_packet)
        SSH2_FREE(session, session->open_packet);
    if(session->open_data)
        SSH2_FREE(session, session->open_data);
    if(session->direct_message)
        SSH2_FREE(session, session->direct_message);
    if(session->fwdLstn_packet)
        SSH2_FREE(session, session->fwdLstn_packet);
    if(session->pkeyInit_data)
        SSH2_FREE(session, session->pkeyInit_data);
    if(session->scpRecv_command)
        SSH2_FREE(session, session->scpRecv_command);
    if(session->scpSend_command)
        SSH2_FREE(session, session->scpSend_command);
    if(session->sftpInit_sftp)
        SSH2_FREE(session, session->sftpInit_sftp);

    /* Free payload buffer */
    if(session->packet.payload)
        SSH2_SAFEFREE(session, session->packet.payload);

    /* Cleanup all remaining packets */
    /* !checksrc! disable EQUALSNULL 1 */
    while((pkg = ssh2_list_first(&session->packets)) != NULL) {
        packets_left++;
        ssh2_deb((session, LIBSSH2_TRACE_TRANS, "packet left with id %d",
                  pkg->data[0]));
        /* unlink the node */
        ssh2_list_remove(&pkg->node);

        /* free */
        SSH2_FREE(session, pkg->data);
        SSH2_FREE(session, pkg);
    }
    (void)packets_left;
    ssh2_deb((session, LIBSSH2_TRACE_TRANS, "Extra packets left %d",
              packets_left));

    if(session->socket_prev_blockstate) {
        /* if the socket was previously blocking, put it back so */
        rc = session_nonblock(session->socket_fd, 0);
        if(rc)
            ssh2_deb((session, LIBSSH2_TRACE_TRANS,
                      "unable to reset socket's blocking state"));
    }

    if(session->server_hostkey)
        SSH2_FREE(session, session->server_hostkey);

    /* error string */
    if(session->err_msg && ((session->err_flags & SSH2_ERR_FLAG_DUP) != 0))
        SSH2_FREE(session, SSH2_UNCONST(session->err_msg));

    SSH2_FREE(session, session);

    return 0;
}

/*
 * Frees the memory allocated to the session
 * Also closes and frees any channels attached to this session
 */
int libssh2_session_free(LIBSSH2_SESSION *session)
{
    int rc;

    if(!session)
        return LIBSSH2_ERROR_BAD_USE;

    BLOCK_ADJUST(rc, session, session_free(session));

    return rc;
}

static int session_disconnect(LIBSSH2_SESSION *session, int reason,
                              const char *description,
                              const char *lang)
{
    unsigned char *s;
    size_t descr_len = 0, lang_len = 0;
    int rc;

    if(session->disconnect_state == ssh2_NB_state_idle) {
        ssh2_deb((session, LIBSSH2_TRACE_TRANS,
                  "Disconnecting: reason=%d, desc=%s, lang=%s", reason,
                  description ? description : "(null)",
                  lang ? lang : "(null)"));
        if(description)
            descr_len = strlen(description);

        if(descr_len > 256)
            return ssh2_err(session, LIBSSH2_ERROR_INVAL,
                            "too long description");

        if(lang)
            lang_len = strlen(lang);

        if(lang_len > 256)
            return ssh2_err(session, LIBSSH2_ERROR_INVAL,
                            "too long language string");

        /* 13 = packet_type(1) + reason code(4) + descr_len(4) + lang_len(4) */
        session->disconnect_data_len = descr_len + 13;

        s = session->disconnect_data;

        *(s++) = SSH_MSG_DISCONNECT;
        ssh2_store_u32(&s, reason);
        ssh2_store_str(&s, description, descr_len);
        /* store length only, lang is sent separately */
        ssh2_store_u32(&s, (uint32_t)lang_len);

        session->disconnect_state = ssh2_NB_state_created;
    }

    rc = ssh2_transport_send(session, session->disconnect_data,
                             session->disconnect_data_len,
                             (const unsigned char *)lang, lang_len);
    if(rc == LIBSSH2_ERROR_EAGAIN)
        return rc;

    session->disconnect_state = ssh2_NB_state_idle;

    return 0;
}

int libssh2_session_disconnect_ex(LIBSSH2_SESSION *session, int reason,
                                  const char *description, const char *lang)
{
    int rc;

    if(!session)
        return LIBSSH2_ERROR_BAD_USE;

    session->state &= ~SSH2_STATE_INITIAL_KEX;
    session->state &= ~SSH2_STATE_EXCHANGING_KEYS;
    BLOCK_ADJUST(rc, session,
                 session_disconnect(session, reason, description, lang));

    return rc;
}

/*
 * Return the currently active methods for method_type
 *
 * NOTE: Currently lang_cs and lang_sc are ALWAYS set to empty string
 * regardless of actual negotiation Strings should NOT be freed
 */
const char *libssh2_session_methods(LIBSSH2_SESSION *session, int method_type)
{
    /* All methods have char *name as their first element */
    const struct kex_method *method = NULL;

    if(!session)
        return NULL;

    switch(method_type) {
    case LIBSSH2_METHOD_KEX:
        method = session->kex;
        break;

    case LIBSSH2_METHOD_HOSTKEY:
        method = (const struct kex_method *)session->hostkey;
        break;

    case LIBSSH2_METHOD_CRYPT_CS:
        method = (const struct kex_method *)session->local.crypt;
        break;

    case LIBSSH2_METHOD_CRYPT_SC:
        method = (const struct kex_method *)session->remote.crypt;
        break;

    case LIBSSH2_METHOD_MAC_CS:
        method = (const struct kex_method *)session->local.mac;
        break;

    case LIBSSH2_METHOD_MAC_SC:
        method = (const struct kex_method *)session->remote.mac;
        break;

    case LIBSSH2_METHOD_COMP_CS:
        method = (const struct kex_method *)session->local.comp;
        break;

    case LIBSSH2_METHOD_COMP_SC:
        method = (const struct kex_method *)session->remote.comp;
        break;

    case LIBSSH2_METHOD_LANG_CS:
        return "";

    case LIBSSH2_METHOD_LANG_SC:
        return "";

    default:
        ssh2_err(session, LIBSSH2_ERROR_INVAL,
                 "Invalid parameter specified for method_type");
        return NULL;
    }

    if(!method) {
        ssh2_err(session, LIBSSH2_ERROR_METHOD_NONE, "No method negotiated");
        return NULL;
    }

    return method->name;
}

/*
 * Retrieve a pointer to the abstract property
 */
void **libssh2_session_abstract(LIBSSH2_SESSION *session)
{
    if(!session)
        return NULL;

    return &session->abstract;
}

/*
 * Returns error code and populates an error string into errmsg If want_buf is
 * non-zero then the string placed into errmsg must be freed by the calling
 * program. Otherwise it is assumed to be owned by libssh2
 */
int libssh2_session_last_error(LIBSSH2_SESSION *session, char **errmsg,
                               int *errmsg_len, int want_buf)
{
    size_t msglen = 0;

    if(!session)
        return LIBSSH2_ERROR_BAD_USE;

    /* No error to report */
    if(!session->err_code) {
        if(errmsg) {
            if(want_buf) {
                *errmsg = SSH2_ALLOC(session, 1);
                if(*errmsg)
                    **errmsg = 0;
            }
            else
                *errmsg = (char *)SSH2_UNCONST("");
        }
        if(errmsg_len)
            *errmsg_len = 0;
        return 0;
    }

    if(errmsg) {
        const char *error = session->err_msg ? session->err_msg : "";

        msglen = strlen(error);

        if(want_buf) {
            /* Make a copy so the calling program can own it */
            *errmsg = SSH2_ALLOC(session, msglen + 1);
            if(*errmsg) {
                memcpy(*errmsg, error, msglen);
                (*errmsg)[msglen] = '\0';
            }
        }
        else
            *errmsg = (char *)SSH2_UNCONST(error);
    }

    if(errmsg_len)
        *errmsg_len = (int)msglen;

    return session->err_code;
}

/*
 * Returns error code
 */
int libssh2_session_last_errno(LIBSSH2_SESSION *session)
{
    if(!session)
        return LIBSSH2_ERROR_BAD_USE;

    return session->err_code;
}

/*
 * Sets the internal error code for the session.
 *
 * This function is available specifically to be used by high level
 * language wrappers (i.e. Python or Perl) that may extend the library
 * features while still relying on its error reporting mechanism.
 */
int libssh2_session_set_last_error(LIBSSH2_SESSION *session,
                                   int errcode, const char *errmsg)
{
    return ssh2_err_flags(session, errcode, errmsg, SSH2_ERR_FLAG_DUP);
}

/*
 * Set/Get session flags
 *
 * Return error code.
 */
int libssh2_session_flag(LIBSSH2_SESSION *session, int flag, int value)
{
    if(!session)
        return LIBSSH2_ERROR_BAD_USE;

    switch(flag) {
    case LIBSSH2_FLAG_SIGPIPE:
        session->flag.sigpipe = value;
        break;
    case LIBSSH2_FLAG_COMPRESS:
        session->flag.compress = value;
        break;
    case LIBSSH2_FLAG_QUOTE_PATHS:
        session->flag.quote_paths = value;
        break;
    default:
        return LIBSSH2_ERROR_INVAL;  /* unknown flag */
    }

    return LIBSSH2_ERROR_NONE;
}

/*
 * Set a session's blocking mode on or off, return the previous status when
 * this function is called. Note this function does not alter the state of the
 * actual socket involved.
 */
int ssh2_session_set_blocking(LIBSSH2_SESSION *session, int blocking)
{
    int bl = session->api_block_mode;
    ssh2_deb((session, LIBSSH2_TRACE_CONN, "Setting blocking mode %s",
              blocking ? "ON" : "OFF"));
    session->api_block_mode = blocking;

    return bl;
}

/*
 * Set a channel's blocking mode on or off, similar to a socket's
 * fcntl(fd, F_SETFL, O_NONBLOCK); type command
 */
void libssh2_session_set_blocking(LIBSSH2_SESSION *session, int blocking)
{
    if(!session)
        return;

    (void)ssh2_session_set_blocking(session, blocking);
}

/*
 * Returns a session's blocking mode on or off
 */
int libssh2_session_get_blocking(LIBSSH2_SESSION *session)
{
    if(!session)
        return 0;

    return session->api_block_mode;
}

/*
 * Set a session's timeout (in msec) for blocking mode,
 * or 0 to disable timeouts.
 */
void libssh2_session_set_timeout(LIBSSH2_SESSION *session, long timeout_ms)
{
    if(!session)
        return;

    session->api_timeout_ms = timeout_ms;
}

/*
 * Returns a session's timeout, or 0 if disabled
 */
long libssh2_session_get_timeout(LIBSSH2_SESSION *session)
{
    if(!session)
        return 0;

    return session->api_timeout_ms;
}

/*
 * Set a session's timeout (in sec) when reading packets,
 * or 0 to use default of 60 seconds.
 */
void libssh2_session_set_read_timeout(LIBSSH2_SESSION *session, long timeout_s)
{
    if(!session)
        return;

    if(timeout_s <= 0)
        timeout_s = SSH2_DEFAULT_READ_TIMEOUT;

    session->packet_read_timeout = ssh2_sec_to_timediff(timeout_s);
}

/*
 * Returns a session's timeout. Default is 60 seconds.
 */
long libssh2_session_get_read_timeout(LIBSSH2_SESSION *session)
{
    if(!session)
        return 0;

    return (long)ssh2_timediff_to_sec(session->packet_read_timeout);
}

#ifndef LIBSSH2_NO_DEPRECATED
/*
 * DEPRECATED, DO NOT USE!
 *
 * Returns 1 if data is available, 0 if not, or a negative libssh2 error code
 * on error.
 */
int libssh2_poll_channel_read(LIBSSH2_CHANNEL *channel, int extended)
{
    LIBSSH2_SESSION *session;
    struct packet *packet;

    if(!channel)
        return LIBSSH2_ERROR_BAD_USE;

    session = channel->session;
    packet = ssh2_list_first(&session->packets);

    while(packet) {
        if(packet->data_len < 5)
            return ssh2_err(session, LIBSSH2_ERROR_BUFFER_TOO_SMALL,
                            "Packet too small");

        if(channel->local.id == ssh2_ntohu32(packet->data + 1)) {
            if(extended == 1 &&
               (packet->data[0] == SSH_MSG_CHANNEL_EXTENDED_DATA ||
                packet->data[0] == SSH_MSG_CHANNEL_DATA)) {
                return 1;
            }
            else if(extended == 0 &&
                    packet->data[0] == SSH_MSG_CHANNEL_DATA) {
                return 1;
            }
            /* else - no data of any type is ready to be read */
        }
        packet = ssh2_list_next(&packet->node);
    }

    return 0;
}

/*
 * Returns 0 if writing to channel would block,
 * non-0 if data can be written without blocking
 */
static SSH2_INLINE int session_poll_channel_write(LIBSSH2_CHANNEL *channel)
{
    return channel->local.window_size ? 1 : 0;
}

/*
 * Returns 0 if no connections are waiting to be accepted
 * non-0 if one or more connections are available
 */
static SSH2_INLINE int session_poll_listener_queued(LIBSSH2_LISTENER *listener)
{
    return ssh2_list_first(&listener->queue) ? 1 : 0;
}

/*
 * DEPRECATED, DO NOT USE!
 *
 * Poll sockets, channels, and listeners for activity
 */
int libssh2_poll(LIBSSH2_POLLFD *fds, unsigned int nfds, long timeout_ms)
{
    ssh2_timediff_t timeout_remaining;
    unsigned int i, active_fds;
#ifdef HAVE_POLL
    LIBSSH2_SESSION *session = NULL;
    struct pollfd sockets_stack[256];
    struct pollfd *sockets_heap = NULL;
    struct pollfd *sockets;

    if(nfds > 256) {
        sockets = sockets_heap = calloc(nfds, sizeof(struct pollfd));
        if(!sockets)
            return -1;
    }
    else
        sockets = sockets_stack;

    /* Setup sockets for polling */
    for(i = 0; i < nfds; i++) {
        fds[i].revents = 0;
        switch(fds[i].type) {
        case LIBSSH2_POLLFD_SOCKET:
            sockets[i].fd = fds[i].fd.socket;
            sockets[i].events = (short)fds[i].events;
            sockets[i].revents = 0;
            break;

        case LIBSSH2_POLLFD_CHANNEL:
            sockets[i].fd = fds[i].fd.channel->session->socket_fd;
            sockets[i].events = POLLIN;
            sockets[i].revents = 0;
            if(!session)
                session = fds[i].fd.channel->session;
            break;

        case LIBSSH2_POLLFD_LISTENER:
            sockets[i].fd = fds[i].fd.listener->session->socket_fd;
            sockets[i].events = POLLIN;
            sockets[i].revents = 0;
            if(!session)
                session = fds[i].fd.listener->session;
            break;

        default:
            if(sockets_heap)
                free(sockets_heap);
            if(session)
                ssh2_err(session, LIBSSH2_ERROR_INVALID_POLL_TYPE,
                         "Invalid descriptor passed to libssh2_poll()");
            return -1;
        }
    }
#else /* !HAVE_POLL, use select() */
    LIBSSH2_SESSION *session = NULL;
    libssh2_socket_t maxfd = 0;
    fd_set rfds, wfds;

    FD_ZERO(&rfds);
    FD_ZERO(&wfds);
    for(i = 0; i < nfds; i++) {
        fds[i].revents = 0;
        switch(fds[i].type) {
        case LIBSSH2_POLLFD_SOCKET:
            if(fds[i].events & LIBSSH2_POLLFD_POLLIN) {
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
                FD_SET(fds[i].fd.socket, &rfds);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif
                if(fds[i].fd.socket > maxfd)
                    maxfd = fds[i].fd.socket;
            }
            if(fds[i].events & LIBSSH2_POLLFD_POLLOUT) {
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
                FD_SET(fds[i].fd.socket, &wfds);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif
                if(fds[i].fd.socket > maxfd)
                    maxfd = fds[i].fd.socket;
            }
            break;

        case LIBSSH2_POLLFD_CHANNEL:
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
            FD_SET(fds[i].fd.channel->session->socket_fd, &rfds);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif
            if(fds[i].fd.channel->session->socket_fd > maxfd)
                maxfd = fds[i].fd.channel->session->socket_fd;
            if(!session)
                session = fds[i].fd.channel->session;
            break;

        case LIBSSH2_POLLFD_LISTENER:
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
            FD_SET(fds[i].fd.listener->session->socket_fd, &rfds);
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif
            if(fds[i].fd.listener->session->socket_fd > maxfd)
                maxfd = fds[i].fd.listener->session->socket_fd;
            if(!session)
                session = fds[i].fd.listener->session;
            break;

        default:
            if(session)
                ssh2_err(session, LIBSSH2_ERROR_INVALID_POLL_TYPE,
                         "Invalid descriptor passed to libssh2_poll()");
            return -1;
        }
    }
#endif /* HAVE_POLL */

    timeout_remaining = ssh2_ms_to_timediff(timeout_ms);
    do {
        int sysret;
        active_fds = 0;

        for(i = 0; i < nfds; i++) {
            if(fds[i].events != fds[i].revents) {
                switch(fds[i].type) {
                case LIBSSH2_POLLFD_CHANNEL:
                    if((fds[i].events & LIBSSH2_POLLFD_POLLIN) &&
                       /* Want to be ready for read */
                       ((fds[i].revents & LIBSSH2_POLLFD_POLLIN) == 0)) {
                        /* Not yet known to be ready for read */
                        fds[i].revents |=
                            libssh2_poll_channel_read(fds[i].fd.channel, 0) ?
                            LIBSSH2_POLLFD_POLLIN : 0;
                    }
                    if((fds[i].events & LIBSSH2_POLLFD_POLLEXT) &&
                       /* Want to be ready for extended read */
                       ((fds[i].revents & LIBSSH2_POLLFD_POLLEXT) == 0)) {
                        /* Not yet known to be ready for extended read */
                        fds[i].revents |=
                            libssh2_poll_channel_read(fds[i].fd.channel, 1) ?
                            LIBSSH2_POLLFD_POLLEXT : 0;
                    }
                    if((fds[i].events & LIBSSH2_POLLFD_POLLOUT) &&
                       /* Want to be ready for write */
                       ((fds[i].revents & LIBSSH2_POLLFD_POLLOUT) == 0)) {
                        /* Not yet known to be ready for write */
                        fds[i].revents |=
                            session_poll_channel_write(fds[i].fd.channel) ?
                            LIBSSH2_POLLFD_POLLOUT : 0;
                    }
                    if(fds[i].fd.channel->remote.close ||
                       fds[i].fd.channel->local.close) {
                        fds[i].revents |= LIBSSH2_POLLFD_CHANNEL_CLOSED;
                    }
                    if(fds[i].fd.channel->session->socket_state ==
                       SSH2_SOCKET_DISCONNECTED) {
                        fds[i].revents |=
                            LIBSSH2_POLLFD_CHANNEL_CLOSED |
                            LIBSSH2_POLLFD_SESSION_CLOSED;
                    }
                    break;

                case LIBSSH2_POLLFD_LISTENER:
                    if((fds[i].events & LIBSSH2_POLLFD_POLLIN) &&
                       /* Want a connection */
                       ((fds[i].revents & LIBSSH2_POLLFD_POLLIN) == 0)) {
                        /* No connections known of yet */
                        fds[i].revents |=
                            session_poll_listener_queued(fds[i].fd.listener) ?
                            LIBSSH2_POLLFD_POLLIN : 0;
                    }
                    if(fds[i].fd.listener->session->socket_state ==
                       SSH2_SOCKET_DISCONNECTED) {
                        fds[i].revents |=
                            LIBSSH2_POLLFD_LISTENER_CLOSED |
                            LIBSSH2_POLLFD_SESSION_CLOSED;
                    }
                    break;
                }
            }
            if(fds[i].revents)
                active_fds++;
        }

        if(active_fds) {
            /* Do not block on the sockets if we have channels/listeners which
               are ready */
            timeout_remaining = 0;
        }

#ifdef HAVE_POLL
        {
            ssh2_timediff_t timeout_remaining_ms =
                ssh2_timediff_to_ms(timeout_remaining);
            ssh2_time_t start_time = ssh2_now(), now;
            sysret = poll(sockets, nfds,
                          (int)SSH2_MIN(timeout_remaining_ms, INT_MAX));
            now = ssh2_now();
            timeout_remaining -= now > start_time ? (now - start_time) : 0;
        }

        if(sysret > 0) {
            for(i = 0; i < nfds; i++) {
                switch(fds[i].type) {
                case LIBSSH2_POLLFD_SOCKET:
                    fds[i].revents = sockets[i].revents;
                    sockets[i].revents = 0; /* Be nice in case we loop again */
                    if(fds[i].revents)
                        active_fds++;
                    break;
                case LIBSSH2_POLLFD_CHANNEL:
                    if(sockets[i].events & POLLIN) {
                        /* Spin session until no data available */
                        while(ssh2_transport_read(fds[i].fd.channel->session)
                              > 0);
                    }
                    if(sockets[i].revents & POLLHUP) {
                        fds[i].revents |=
                            LIBSSH2_POLLFD_CHANNEL_CLOSED |
                            LIBSSH2_POLLFD_SESSION_CLOSED;
                    }
                    sockets[i].revents = 0;
                    break;
                case LIBSSH2_POLLFD_LISTENER:
                    if(sockets[i].events & POLLIN) {
                        /* Spin session until no data available */
                        while(ssh2_transport_read(fds[i].fd.listener->session)
                              > 0);
                    }
                    if(sockets[i].revents & POLLHUP) {
                        fds[i].revents |=
                            LIBSSH2_POLLFD_LISTENER_CLOSED |
                            LIBSSH2_POLLFD_SESSION_CLOSED;
                    }
                    sockets[i].revents = 0;
                    break;
                }
            }
        }

#else /* !HAVE_POLL, use select() */

        {
            ssh2_time_t start_time, now;
            struct timeval tv;
            tv.tv_sec = (long)ssh2_timediff_to_sec(timeout_remaining);
#ifdef libssh2_usec_t
            tv.tv_usec =
                (libssh2_usec_t)ssh2_timediff_to_usec(timeout_remaining);
#else
            tv.tv_usec = ssh2_timediff_to_usec(timeout_remaining);
#endif
            start_time = ssh2_now();
            sysret = select((int)(maxfd + 1), &rfds, &wfds, NULL,
                            timeout_remaining >= 0 ? &tv : NULL);
            now = ssh2_now();
            timeout_remaining -= now > start_time ? (now - start_time) : 0;
        }

        if(sysret > 0) {
            for(i = 0; i < nfds; i++) {
                switch(fds[i].type) {
                case LIBSSH2_POLLFD_SOCKET:
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wsign-conversion"
#endif
                    if(FD_ISSET(fds[i].fd.socket, &rfds))
                        fds[i].revents |= LIBSSH2_POLLFD_POLLIN;
                    if(FD_ISSET(fds[i].fd.socket, &wfds))
                        fds[i].revents |= LIBSSH2_POLLFD_POLLOUT;
                    if(fds[i].revents)
                        active_fds++;
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif
                    break;

                case LIBSSH2_POLLFD_CHANNEL:
                    if(FD_ISSET(fds[i].fd.channel->session->socket_fd,
                                &rfds)) {
                        /* Spin session until no data available */
                        while(ssh2_transport_read(fds[i].fd.channel->session)
                              > 0);
                    }
                    break;

                case LIBSSH2_POLLFD_LISTENER:
                    if(FD_ISSET(fds[i].fd.listener->session->socket_fd,
                                &rfds)) {
                        /* Spin session until no data available */
                        while(ssh2_transport_read(fds[i].fd.listener->session)
                              > 0);
                    }
                    break;
                }
            }
        }
#endif /* HAVE_POLL */
    } while(timeout_remaining > 0 && !active_fds);

#ifdef HAVE_POLL
    if(sockets_heap)
        free(sockets_heap);
#endif

    return active_fds;
}
#endif /* LIBSSH2_NO_DEPRECATED */

/*
 * Get blocked direction when a function returns LIBSSH2_ERROR_EAGAIN
 * Returns SSH2_SOCKET_BLOCK_INBOUND if recv() blocked
 * or SSH2_SOCKET_BLOCK_OUTBOUND if send() blocked
 */
int libssh2_session_block_directions(LIBSSH2_SESSION *session)
{
    if(!session)
        return 0;

    return session->socket_block_directions;
}

/*
 * Get the remote banner (server ID string)
 */
const char *libssh2_session_banner_get(LIBSSH2_SESSION *session)
{
    if(!session)
        return NULL;

    if(!session->remote.banner)
        return NULL;

    return session->remote.banner;
}