GUACAMOLE-203: Merge support for SSH/SFTP connection keep-alive packets.

src/common-ssh/common-ssh/ssh.h

@@ -98,7 +98,7 @@ void guac_common_ssh_uninit();
  *     if the connection or authentication were not successful.
  */
 guac_common_ssh_session* guac_common_ssh_create_session(guac_client* client,
-        const char* hostname, const char* port, guac_common_ssh_user* user);
+        const char* hostname, const char* port, guac_common_ssh_user* user, int keepalive);
 
 /**
  * Disconnects and destroys the given SSH session, freeing all associated

src/common-ssh/ssh.c

@@ -414,7 +414,7 @@ static int guac_common_ssh_authenticate(guac_common_ssh_session* common_session)
 }
 
 guac_common_ssh_session* guac_common_ssh_create_session(guac_client* client,
-        const char* hostname, const char* port, guac_common_ssh_user* user) {
+        const char* hostname, const char* port, guac_common_ssh_user* user, int keepalive) {
 
     int retval;
 
@@ -532,6 +532,20 @@ guac_common_ssh_session* guac_common_ssh_create_session(guac_client* client,
         return NULL;
     }
 
+    /* Warn if keepalive below minimum value */
+    if (keepalive < 0) {
+        keepalive = 0;
+        guac_client_log(client, GUAC_LOG_WARNING, "negative keepalive intervals "
+            "are converted to 0, disabling keepalive.");
+    }
+    else if (keepalive == 1) {
+        guac_client_log(client, GUAC_LOG_WARNING, "keepalive interval will "
+            "be rounded up to minimum value of 2.");
+    }
+
+    /* Configure session keepalive */
+    libssh2_keepalive_config(common_session->session, 1, keepalive);
+
     /* Return created session */
     return common_session;
 

src/protocols/rdp/rdp.c

@@ -977,7 +977,7 @@ void* guac_rdp_client_thread(void* data) {
         /* Attempt SSH connection */
         rdp_client->sftp_session =
             guac_common_ssh_create_session(client, settings->sftp_hostname,
-                    settings->sftp_port, rdp_client->sftp_user);
+                    settings->sftp_port, rdp_client->sftp_user, settings->sftp_server_alive_interval);
 
         /* Fail if SSH connection does not succeed */
         if (rdp_client->sftp_session == NULL) {

src/protocols/rdp/rdp_settings.c

@@ -84,6 +84,7 @@ const char* GUAC_RDP_CLIENT_ARGS[] = {
     "sftp-private-key",
     "sftp-passphrase",
     "sftp-directory",
+    "sftp-server-alive-interval",
 #endif
 
     "recording-path",
@@ -366,6 +367,13 @@ enum RDP_ARGS_IDX {
      */
     IDX_SFTP_DIRECTORY,
 
+    /**
+     * The interval at which SSH keepalive messages are sent to the server for
+     * SFTP connections.  The default is 0 (disabling keepalives), and a value
+     * of 1 is automatically increased to 2 by libssh2 to avoid busy loop corner
+     * cases.
+     */
+    IDX_SFTP_SERVER_ALIVE_INTERVAL,
 #endif
 
     /**
@@ -775,6 +783,11 @@ guac_rdp_settings* guac_rdp_parse_args(guac_user* user,
     settings->sftp_directory =
         guac_user_parse_args_string(user, GUAC_RDP_CLIENT_ARGS, argv,
                 IDX_SFTP_DIRECTORY, NULL);
+
+    /* Default keepalive value */
+    settings->sftp_server_alive_interval =
+        guac_user_parse_args_int(user, GUAC_RDP_CLIENT_ARGS, argv,
+                IDX_SFTP_SERVER_ALIVE_INTERVAL, 0);
 #endif
 
     /* Read recording path */

src/protocols/rdp/rdp_settings.h

@@ -359,6 +359,14 @@ typedef struct guac_rdp_settings {
      * the destination directory is otherwise ambiguous).
      */
     char* sftp_directory;
+
+    /**
+     * The interval at which SSH keepalive messages are sent to the server for
+     * SFTP connections.  The default is 0 (disabling keepalives), and a value
+     * of 1 is automatically increased to 2 by libssh2 to avoid busy loop corner
+     * cases.
+     */
+    int sftp_server_alive_interval;
 #endif
 
     /**

src/protocols/ssh/settings.c

@@ -51,6 +51,7 @@ const char* GUAC_SSH_CLIENT_ARGS[] = {
     "recording-name",
     "create-recording-path",
     "read-only",
+    "server-alive-interval",
     NULL
 };
 
@@ -165,6 +166,13 @@ enum SSH_ARGS_IDX {
      */
     IDX_READ_ONLY,
 
+    /**
+     * Number of seconds between sending alive packets.  A default of 0
+     * tells SSH not to send these packets.  A value of 1 is automatically
+     * changed by libssh2 to 2 to avoid busy-loop corner cases.
+     */
+    IDX_SERVER_ALIVE_INTERVAL,
+
     SSH_ARGS_COUNT
 };
 
@@ -279,6 +287,11 @@ guac_ssh_settings* guac_ssh_parse_args(guac_user* user,
         guac_user_parse_args_boolean(user, GUAC_SSH_CLIENT_ARGS, argv,
                 IDX_CREATE_RECORDING_PATH, false);
 
+    /* Parse server alive interval */
+    settings->server_alive_interval =
+        guac_user_parse_args_int(user, GUAC_SSH_CLIENT_ARGS, argv,
+                IDX_SERVER_ALIVE_INTERVAL, 0);
+
     /* Parsing was successful */
     return settings;
 

src/protocols/ssh/settings.h

@@ -53,6 +53,11 @@
  */
 #define GUAC_SSH_DEFAULT_RECORDING_NAME "recording"
 
+/**
+ * The default polling timeout for SSH activity in milliseconds.
+ */
+#define GUAC_SSH_DEFAULT_POLL_TIMEOUT 1000
+
 /**
  * Settings for the SSH connection. The values for this structure are parsed
  * from the arguments given during the Guacamole protocol handshake using the
@@ -181,6 +186,11 @@ typedef struct guac_ssh_settings {
      */
     bool create_recording_path;
 
+    /**
+     * The number of seconds between sending server alive messages.
+     */
+    int server_alive_interval;
+
 } guac_ssh_settings;
 
 /**

src/protocols/ssh/ssh.c

@@ -218,7 +218,7 @@ void* ssh_client_thread(void* data) {
 
     /* Open SSH session */
     ssh_client->session = guac_common_ssh_create_session(client,
-            settings->hostname, settings->port, ssh_client->user);
+            settings->hostname, settings->port, ssh_client->user, settings->server_alive_interval);
     if (ssh_client->session == NULL) {
         /* Already aborted within guac_common_ssh_create_session() */
         return NULL;
@@ -258,7 +258,7 @@ void* ssh_client_thread(void* data) {
         guac_client_log(client, GUAC_LOG_DEBUG, "Reconnecting for SFTP...");
         ssh_client->sftp_session =
             guac_common_ssh_create_session(client, settings->hostname,
-                    settings->port, ssh_client->user);
+                    settings->port, ssh_client->user, settings->server_alive_interval);
         if (ssh_client->sftp_session == NULL) {
             /* Already aborted within guac_common_ssh_create_session() */
             return NULL;
@@ -323,6 +323,9 @@ void* ssh_client_thread(void* data) {
         /* Track total amount of data read */
         int total_read = 0;
 
+        /* Timeout for polling socket activity */
+        int timeout;
+
         pthread_mutex_lock(&(ssh_client->term_channel_lock));
 
         /* Stop reading at EOF */
@@ -331,6 +334,17 @@ void* ssh_client_thread(void* data) {
             break;
         }
 
+        /* Send keepalive at configured interval */
+        if (settings->server_alive_interval > 0) {
+            timeout = 0;
+            if (libssh2_keepalive_send(ssh_client->session->session, &timeout) > 0)
+                break;
+            timeout *= 1000;
+        }
+        /* If keepalive is not configured, sleep for the default of 1 second */
+        else
+            timeout = GUAC_SSH_DEFAULT_POLL_TIMEOUT;
+
         /* Read terminal data */
         bytes_read = libssh2_channel_read(ssh_client->term_channel,
                 buffer, sizeof(buffer));
@@ -370,8 +384,8 @@ void* ssh_client_thread(void* data) {
                 .revents = 0,
             }};
 
-            /* Wait up to one second */
-            if (poll(fds, 1, 1000) < 0)
+            /* Wait up to computed timeout */
+            if (poll(fds, 1, timeout) < 0)
                 break;
 
         }

src/protocols/vnc/settings.c

@@ -66,6 +66,7 @@ const char* GUAC_VNC_CLIENT_ARGS[] = {
     "sftp-private-key",
     "sftp-passphrase",
     "sftp-directory",
+    "sftp-server-alive-interval",
 #endif
 
     "recording-path",
@@ -227,6 +228,14 @@ enum VNC_ARGS_IDX {
      * the destination directory is otherwise ambiguous).
      */
     IDX_SFTP_DIRECTORY,
+
+    /**
+     * The interval at which SSH keepalive messages are sent to the server for
+     * SFTP connections.  The default is 0 (disabling keepalives), and a value
+     * of 1 is automatically incremented to 2 by libssh2 to avoid busy loop corner
+     * cases.
+     */
+    IDX_SFTP_SERVER_ALIVE_INTERVAL,
 #endif
 
     /**
@@ -395,6 +404,11 @@ guac_vnc_settings* guac_vnc_parse_args(guac_user* user,
     settings->sftp_directory =
         guac_user_parse_args_string(user, GUAC_VNC_CLIENT_ARGS, argv,
                 IDX_SFTP_DIRECTORY, NULL);
+
+    /* Default keepalive value */
+    settings->sftp_server_alive_interval =
+        guac_user_parse_args_int(user, GUAC_VNC_CLIENT_ARGS, argv,
+                IDX_SFTP_SERVER_ALIVE_INTERVAL, 0);
 #endif
 
     /* Read recording path */

src/protocols/vnc/settings.h

@@ -173,6 +173,14 @@ typedef struct guac_vnc_settings {
      * the destination directory is otherwise ambiguous).
      */
     char* sftp_directory;
+
+    /**
+     * The interval at which SSH keepalive messages are sent to the server for
+     * SFTP connections.  The default is 0 (disabling keepalives), and a value
+     * of 1 is automatically increased to 2 by libssh2 to avoid busy loop corner
+     * cases.
+     */
+    int sftp_server_alive_interval;
 #endif
 
     /**

src/protocols/vnc/vnc.c

@@ -261,7 +261,7 @@ void* guac_vnc_client_thread(void* data) {
         /* Attempt SSH connection */
         vnc_client->sftp_session =
             guac_common_ssh_create_session(client, settings->sftp_hostname,
-                    settings->sftp_port, vnc_client->sftp_user);
+                    settings->sftp_port, vnc_client->sftp_user, settings->sftp_server_alive_interval);
 
         /* Fail if SSH connection does not succeed */
         if (vnc_client->sftp_session == NULL) {