Add keep-alive support.

Makefile.inc

@@ -1,5 +1,5 @@
 CSOURCES = channel.c comp.c crypt.c hostkey.c kex.c mac.c misc.c \
  packet.c publickey.c scp.c session.c sftp.c userauth.c transport.c \
- version.c knownhost.c agent.c openssl.c libgcrypt.c pem.c
+ version.c knownhost.c agent.c openssl.c libgcrypt.c pem.c keepalive.c
 
 HHEADERS = libssh2_priv.h openssl.h libgcrypt.h transport.h channel.h comp.h mac.h misc.h

include/libssh2.h

@@ -1,5 +1,6 @@
 /* Copyright (c) 2004-2009, Sara Golemon <sarag@libssh2.org>
  * Copyright (c) 2009 by Daniel Stenberg
+ * Copyright (c) 2010 Simon Josefsson <simon@josefsson.org>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms,
@@ -973,6 +974,35 @@ libssh2_agent_disconnect(LIBSSH2_AGENT *agent);
 LIBSSH2_API void
 libssh2_agent_free(LIBSSH2_AGENT *agent);
 
+
+/*
+ * libssh2_keepalive_config()
+ *
+ * Set how often keepalive messages should be sent.  WANT_REPLY
+ * indicates whether the keepalive messages should request a response
+ * from the server.  INTERVAL is number of seconds that can pass
+ * without any I/O, use 0 (the default) to disable keepalives.  To
+ * avoid some busy-loop corner-cases, if you specify an interval of 1
+ * it will be treated as 2.
+ *
+ * Note that non-blocking applications are responsible for sending the
+ * keepalive messages using libssh2_keepalive_send().
+ */
+LIBSSH2_API void libssh2_keepalive_config (LIBSSH2_SESSION *session,
+                                           int want_reply,
+                                           unsigned interval);
+
+/*
+ * libssh2_keepalive_send()
+ *
+ * Send a keepalive message if needed.  SECONDS_TO_NEXT indicates how
+ * many seconds you can sleep after this call before you need to call
+ * it again.  Returns 0 on success, or LIBSSH2_ERROR_SOCKET_SEND on
+ * I/O errors.
+ */
+LIBSSH2_API int libssh2_keepalive_send (LIBSSH2_SESSION *session,
+                                        int *seconds_to_next);
+
 /* NOTE NOTE NOTE
    libssh2_trace() has no function in builds that aren't built with debug
    enabled

src/keepalive.c

@@ -0,0 +1,97 @@
+/* Copyright (C) 2010  Simon Josefsson
+ * Author: Simon Josefsson
+ *
+ * Redistribution and use in source and binary forms,
+ * with or without modification, are permitted provided
+ * that the following conditions are met:
+ *
+ *   Redistributions of source code must retain the above
+ *   copyright notice, this list of conditions and the
+ *   following disclaimer.
+ *
+ *   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.
+ *
+ *   Neither the name of the copyright holder nor the names
+ *   of any other 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 OWNER 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.
+ *
+ */
+
+#include "libssh2_priv.h"
+#include "transport.h" /* _libssh2_transport_write */
+
+/* Keep-alive stuff. */
+
+LIBSSH2_API void
+libssh2_keepalive_config (LIBSSH2_SESSION *session,
+                          int want_reply,
+                          unsigned interval)
+{
+    if (interval == 1)
+        session->keepalive_interval = 2;
+    else
+        session->keepalive_interval = interval;
+    session->keepalive_want_reply = want_reply ? 1 : 0;
+}
+
+LIBSSH2_API int
+libssh2_keepalive_send (LIBSSH2_SESSION *session,
+                        int *seconds_to_next)
+{
+    time_t now;
+
+    if (!session->keepalive_interval) {
+        if (seconds_to_next)
+            *seconds_to_next = 0;
+        return 0;
+    }
+
+    now = time (NULL);
+
+    if (session->keepalive_last_sent + session->keepalive_interval <= now) {
+/* Format is "SSH_MSG_GLOBAL_REQUEST || 4-byte len || str || want-reply". */
+        unsigned char keepalive_data[]
+            = "\x50\x00\x00\x00\x15keepalive@libssh2.orgW";
+        size_t len = sizeof (keepalive_data) - 1;
+        int rc;
+
+        keepalive_data[len - 1] = session->keepalive_want_reply;
+
+        rc = _libssh2_transport_write(session, keepalive_data, len);
+/* Silently ignore PACKET_EAGAIN here: if the write buffer is
+   already full, sending another keepalive is not useful. */
+        if (rc && rc != PACKET_EAGAIN) {
+            libssh2_error(session, LIBSSH2_ERROR_SOCKET_SEND,
+                          "Unable to send keepalive message", 0);
+            return rc;
+        }
+
+        session->keepalive_last_sent = now;
+        if (seconds_to_next)
+            *seconds_to_next = session->keepalive_interval;
+    } else if (seconds_to_next) {
+        *seconds_to_next = session->keepalive_last_sent
+            + session->keepalive_interval - now;
+    }
+
+    return 0;
+}

src/libssh2_priv.h

@@ -908,6 +908,11 @@ struct _LIBSSH2_SESSION
     char *scpSend_err_msg;
     long scpSend_err_len;
     LIBSSH2_CHANNEL *scpSend_channel;
+
+    /* Keepalive variables used by keepalive.c. */
+    int keepalive_interval;
+    int keepalive_want_reply;
+    time_t keepalive_last_sent;
 };
 
 /* session.state bits */

src/session.c

@@ -1,5 +1,6 @@
 /* Copyright (c) 2004-2007 Sara Golemon <sarag@libssh2.org>
  * Copyright (c) 2009 by Daniel Stenberg
+ * Copyright (c) 2010 Simon Josefsson <simon@josefsson.org>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms,
@@ -521,6 +522,15 @@ int _libssh2_wait_socket(LIBSSH2_SESSION *session)
     fd_set *readfd = NULL;
     int dir;
     int rc;
+    struct timeval tv;
+    int seconds_to_next;
+
+    rc = libssh2_keepalive_send (session, &seconds_to_next);
+    if (rc < 0)
+        return rc;
+
+    tv.tv_sec = seconds_to_next;
+    tv.tv_usec = 0;
 
     FD_ZERO(&fd);
     FD_SET(session->socket_fd, &fd);
@@ -536,7 +546,8 @@ int _libssh2_wait_socket(LIBSSH2_SESSION *session)
 
     /* Note that this COULD be made to use a timeout that perhaps could be
        customizable by the app or something... */
-    rc = select(session->socket_fd + 1, readfd, writefd, NULL, NULL);
+    rc = select(session->socket_fd + 1, readfd, writefd, NULL,
+                seconds_to_next ? &tv : NULL);
 
     if(rc <= 0) {
         /* timeout (or error), bail out with a timeout error */