sftp: Add sftp_fsync() function

BUG: https://red.libssh.org/issues/141

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>

include/libssh/sftp.h

@@ -788,6 +788,22 @@ LIBSSH_API sftp_statvfs_t sftp_fstatvfs(sftp_file file);
  */
 LIBSSH_API void sftp_statvfs_free(sftp_statvfs_t statvfs_o);
 
+/**
+ * @brief Synchronize a file's in-core state with storage device
+ *
+ * This calls the "fsync@openssh.com" extention. You should check if the
+ * extensions is supported using:
+ *
+ * @code
+ * int supported = sftp_extension_supported(sftp, "fsync@openssh.com", "1");
+ * @endcode
+ *
+ * @param file          The opened sftp file handle to sync
+ *
+ * @return              0 on success, < 0 on error with ssh and sftp error set.
+ */
+LIBSSH_API int sftp_fsync(sftp_file file);
+
 /**
  * @brief Canonicalize a sftp path.
  *

src/sftp.c

@@ -2774,6 +2774,118 @@ sftp_statvfs_t sftp_statvfs(sftp_session sftp, const char *path) {
   return NULL;
 }
 
+int sftp_fsync(sftp_file file)
+{
+    sftp_session sftp;
+    sftp_message msg = NULL;
+    ssh_string ext;
+    ssh_buffer buffer;
+    uint32_t id;
+    int rc;
+
+    if (file == NULL) {
+        return -1;
+    }
+    sftp = file->sftp;
+
+    buffer = ssh_buffer_new();
+    if (buffer == NULL) {
+        ssh_set_error_oom(sftp->session);
+        return -1;
+    }
+
+    ext = ssh_string_from_char("fsync@openssh.com");
+    if (ext == NULL) {
+        ssh_set_error_oom(sftp->session);
+        rc = -1;
+        goto done;
+    }
+
+    id = sftp_get_new_id(sftp);
+    rc = ssh_buffer_add_u32(buffer, htonl(id));
+    if (rc < 0) {
+        ssh_set_error_oom(sftp->session);
+        goto done;
+    }
+
+    rc = ssh_buffer_add_ssh_string(buffer, ext);
+    if (rc < 0) {
+        ssh_set_error_oom(sftp->session);
+        goto done;
+    }
+
+    rc = ssh_buffer_add_ssh_string(buffer, file->handle);
+    if (rc < 0) {
+        ssh_set_error_oom(sftp->session);
+        goto done;
+    }
+
+    rc = sftp_packet_write(sftp, SSH_FXP_EXTENDED, buffer);
+    if (rc < 0) {
+        ssh_set_error_oom(sftp->session);
+        goto done;
+    }
+
+    do {
+        rc = sftp_read_and_dispatch(sftp);
+        if (rc < 0) {
+            ssh_set_error_oom(sftp->session);
+            rc = -1;
+            goto done;
+        }
+        msg = sftp_dequeue(sftp, id);
+    } while (msg == NULL);
+
+    /* By specification, this command only returns SSH_FXP_STATUS */
+    if (msg->packet_type == SSH_FXP_STATUS) {
+        sftp_status_message status;
+
+        status = parse_status_msg(msg);
+        sftp_message_free(msg);
+        if (status == NULL) {
+            rc = -1;
+            goto done;
+        }
+
+        sftp_set_error(sftp, status->status);
+        switch (status->status) {
+            case SSH_FX_OK:
+                /* SUCCESS, LEAVE */
+                status_msg_free(status);
+                rc = 0;
+                goto done;
+            default:
+                break;
+        }
+
+        /*
+         * The status should be SSH_FX_OK if the command was successful, if it
+         * didn't, then there was an error
+         */
+        ssh_set_error(sftp->session,
+                      SSH_REQUEST_DENIED,
+                      "SFTP server: %s",
+                      status->errormsg);
+        status_msg_free(status);
+
+        rc = -1;
+        goto done;
+    } else {
+        ssh_set_error(sftp->session,
+                      SSH_FATAL,
+                      "Received message %d when attempting to set stats",
+                      msg->packet_type);
+        sftp_message_free(msg);
+    }
+
+    rc = -1;
+done:
+    ssh_buffer_free(buffer);
+    ssh_string_free(ext);
+
+    return rc;
+}
+
 sftp_statvfs_t sftp_fstatvfs(sftp_file file) {
   sftp_status_message status = NULL;
   sftp_message msg = NULL;
@@ -3076,4 +3188,3 @@ sftp_attributes sftp_fstat(sftp_file file) {
 }
 
 #endif /* WITH_SFTP */
-/* vim: set ts=2 sw=2 et cindent: */