refactored README

2024-10-27 20:44:10 +00:00 · 2020-02-18 21:48:52 +01:00 · 2020-02-18 21:48:52 +01:00 · 4ae7160919
commit 4ae7160919
parent 7b8616fcb3
7 changed files with 414 additions and 422 deletions
--- a/4
+++ b/4
@ -112,7 +112,9 @@ WARN_LOGFILE           =
 #---------------------------------------------------------------------------
 # Configuration options related to the input files
 #---------------------------------------------------------------------------
-INPUT                  = README.md include
+INPUT                  = README.md \
                         doc/build.md doc/protocol.md doc/api.md \
                         include
 INPUT_ENCODING         = UTF-8
 FILE_PATTERNS          = *.h
 RECURSIVE              = YES
--- a/README.md
+++ b/README.md
@ -12,9 +12,7 @@ webfuse combines libwebsockets and libfuse. It allows ot attach a remote filesys
 -   [Fellow Repositories](#Fellow-Repositories)
 -   [Concept](#Concept)
 -   [Similar Projects](#Similar-Projects)
-   [API](#API)
+-   [Further Documentation](#Further-Documentation)
 -   [Build](#Build)
 -   [Dependencies](#Dependencies)
 ## Motivation
@ -53,27 +51,14 @@ A reference implementation of such a daemon is provided within the examples. The
 -   Whenever the user makes filesystem requests, such as *ls*, the request is redirected via webfuse daemon to the connected filesystem provider
-Currently all requests are initiated by webfuse daemon and responded by filesystem provider. This may change in future, e.g. when authentication is supported.
+### Adapters and Providers
-### Filesystem represenation
+In webfuse, an adapter is a component that adapts the libfuse API to a websocket interface.
 Currently, libwebfuse implements only a server based adapter - a websocket server, that allows clients to connect a remote file system which
 is represented via libfuse on the server side.
-![filesystem](doc/filesystem.png)
+In webfuse, a provider is a component that provides a filesystem via websocket interface.
-
+Currently, libwebfuse implements only a client based provider - a websocket client that provides a local filesystem to a remote server.
 To handle multiple filesystems, that are registered by one or more providers, webfuse daemon maintains a directory structure as shown above.
 -   **mount_point** is the entry point of the drectory structure
 -   **fwupdate** is a name defined by the provider when filesystem was registered  
    *Note: the picture above shows two providers, where both registered a filesystem named "fwupdate"*
 -   **&lt;uuid&gt;** is the filesystem id choosen by webfuse daemon to distinguish different filesystems
 -   **default** is a symbolic link maintained by webfuse daemon to identify the default filesystem
 This directoy structure allows to handle multiple filesystems registered by multiple providers.
 It can be used as a kind of service registry, where each filesystem represents a service.
 The named subdirectores distinguish differend service types. The symbolic link *default* can be used to identify the
 default service and the listing of a named subdirectory can be used to list available services of a particular type.
 ## Similar Projects
@ -83,387 +68,8 @@ default service and the listing of a named subdirectory can be used to list avai
 Unlike webfuse, davfs2 mounts a remote filesystem locally, that is provided by a WebDAV server. In contrast, webfuse starts a server awaiting client connections to attach the remote file system.
-## API
+## Further Documentation
-### Requests, responses and notifications
+-   [Build instructions](doc/build.md)
-
+-   [Webfuse Protocol](doc/protocol.md)
-There are three types of messages, used for communication between webfuse daemon and filesystem provider. All message types are encoded in [JSON](https://www.json.org/) and strongly inspired by [JSON-RPC](https://www.jsonrpc.org/).
+-   [API](doc/api.md)
 #### Request
 A request is used by a sender to invoke a method on the receiver. The sender awaits a response from the receiver. Since requests and responses can be sendet or answered in any order, an id is provided in each request to identify it.
    {
      "method": <method_name>,
      "params": <params>,
      "id"    : <id>
    }
 | Item        | Data type | Description                       |
 | ----------- |:---------:| --------------------------------- |
 | method_name | string    | name of the method to invoke      |
 | params      | array     | method specific parameters        |
 | id          | integer   | id, which is repeated in response |
 #### Response
 A response is used to answer a prior request. There are two kinds of responses:
 ##### Successful Results
    {
       "result": <result>,
       "id": <id>
    }
 | Item        | Data type | Description             |
 | ----------- |:---------:| ----------------------- |
 | result      | any       | request specific result |
 | id          | integer   | id, same as request     |
 ##### Error notifications
    {
       "error": {
         "code": <code>
       },
       "id": <id>
    }
 | Item        | Data type | Description         |
 | ----------- |:---------:| ------------------- |
 | code        | integer   | error code          |
 | id          | integer   | id, same as request |
 ##### Error codes
 | Symbolic name      | Code      | Description            |
 | ------------------ | ---------:| ---------------------- |
 | GOOD               | 0         | no error               |
 | BAD                | 1         | generic error          |
 | BAD_NOTIMPLEMENTED | 2         | method not implemented |
 | BAD_TIMEOUT        | 3         | timeout occured        |
 | BAD_BUSY           | 4         | resource busy          |
 | BAD_FORMAT         | 5         | invalid formt          |
 | BAD_NOENTRY        | 101       | invalid entry          |
 | BAD_ACCESS_DENIED  | 102       | access not allowed     |
 #### Notification
 Notfications are used to inform a receiver about something. Unlike requests, notifications are not answered. Therefore, an id is not supplied.
    {
      "method": <method_name>,
      "params": <params>
    }
 | Item        | Data type | Description                       |
 | ----------- |:---------:| --------------------------------- |
 | method_name | string    | name of the method to invoke      |
 | params      | array     | method specific parameters        |
 ### Requests (Adapter -> Provider)
 #### lookup
 Retrieve information about a filesystem entry by name.
    webfuse daemon: {"method": "lookup", "params": [<filesystem>, <parent>, <name>], "id": <id>}
    fs provider: {"result": {
        "inode": <inode>,
        "mode" : <mode>,
        "type" : <type>,
        "size" : <size>,
        "atime": <atime>,
        "mtime": <mtime>,
        "ctime": <ctime>
        }, "id": <id>}
 | Item        | Data type       | Description                                 |
 | ----------- | --------------- | ------------------------------------------- |
 | filesystem  | string          | name of the filesystem                      |
 | parent      | integer         | inode of parent directory (1 = root)        |
 | name        | string          | name of the filesystem object to look up    |
 | inode       | integer         | inode of the filesystem object              |
 | mode        | integer         | unix file mode                              |
 | type        | "file" or "dir" | type of filesystem object                   |
 | size        | integer         | required for files; file size in bytes      |
 | atime       | integer         | optional; unix time of last access          |
 | mtime       | integer         | optional; unix time of last modification    |
 | ctime       | intefer         | optional; unix time of last metadata change |
 #### getattr
 Get file attributes.
    webfuse daemon: {"method": "getattr", "params": [<filesystem>, <inode>], "id": <id>}
    fs provider: {"result": {
        "mode" : <mode>,
        "type" : <type>,
        "size" : <size>,
        "atime": <atime>,
        "mtime": <mtime>,
        "ctime": <ctime>
        }, "id": <id>}
 | Item        | Data type       | Description                                 |
 | ----------- | --------------- | ------------------------------------------- |
 | filesystem  | string          | name of the filesystem                      |
 | inode       | integer         | inode of the filesystem object              |
 | mode        | integer         | unix file mode                              |
 | type        | "file" or "dir" | type of filesystem object                   |
 | size        | integer         | required for files; file size in bytes      |
 | atime       | integer         | optional; unix time of last access          |
 | mtime       | integer         | optional; unix time of last modification    |
 | ctime       | intefer         | optional; unix time of last metadata change |
 #### readdir
 Read directory contents.  
 Result is an array of name-inode pairs for each entry. The generic entries
 "." and ".." should also be provided.
    webfuse daemon: {"method": "readdir", "params": [<filesystem>, <dir_inode>], "id": <id>}
    fs provider: {"result": [
        {"name": <name>, "inode": <inode>},
        ...
        ], "id": <id>}
 | Item        | Data type       | Description                    |
 | ----------- | --------------- | ------------------------------ |
 | filesystem  | string          | name of the filesystem         |
 | dir_inode   | integer         | inode of the directory to read |
 | name        | integer         | name of the entry              |
 | inode       | integer         | inode of the entry             |
 #### open
 Open a file.
    webfuse daemon: {"method": "readdir", "params": [<filesystem>, <inode>, <flags>], "id": <id>}
    fs provider: {"result": {"handle": <handle>}, "id": <id>}
 | Item        | Data type | Description                   |
 | ----------- | ----------| ----------------------------- |
 | filesystem  | string    | name of the filesystem        |
 | inode       | integer   | inode of the file             |
 | flags       | integer   | access mode flags (see below) |
 | handle      | integer   | handle of the file            |
 ##### Flags
 | Symbolic name | Code      | Description                 |
 | --------------| ---------:| --------------------------- |
 | O_ACCMODE     | 0x003     | access mode mask            |
 | O_RDONLY      | 0x000     | open for reading only       |
 | O_WRONLY      | 0x001     | open for writing only       |
 | O_RDWR        | 0x002     | open for reading an writing |
 | O_CREAT       | 0x040     | create (a new) file         |
 | O_EXCL        | 0x080     | open file exclusivly        |
 | O_TRUNC       | 0x200     | open file to truncate       |
 | O_APPEND      | 0x400     | open file to append         |
 #### close
 Informs filesystem provider, that a file is closed.  
 Since `close` is a notification, it cannot fail.
    webfuse daemon: {"method": "close", "params": [<filesystem>, <inode>, <handle>, <flags>], "id": <id>}
 | Item        | Data type | Description                  |
 | ----------- | ----------| ---------------------------- |
 | filesystem  | string    | name of the filesystem       |
 | inode       | integer   | inode of the file            |
 | handle      | integer   | handle of the file           |
 | flags       | integer   | access mode flags (see open) |
 #### read
 Read from an open file.
    webfuse daemon: {"method": "close", "params": [<filesystem>, <inode>, <handle>, <offset>, <length>], "id": <id>}
    fs provider: {"result": {
        "data": <data>,
        "format": <format>,
        "count": <count>
        }, "id": <id>}
 | Item        | Data type | Description                   |
 | ----------- | ----------| ----------------------------- |
 | filesystem  | string    | name of the filesystem        |
 | inode       | integer   | inode of the file             |
 | handle      | integer   | handle of the file            |
 | offset      | integer   | Offet to start read operation |
 | length      | integer   | Max. number of bytes to read  |
 | data        | integer   | handle of the file            |
 | format      | string    | Encoding of data (see below)  |
 | count       | integer   | Actual number of bytes read   |
 ##### Format
 | Format     | Description                                              |
 | ---------- | -------------------------------------------------------- |
 | "identiy"  | Use data as is; note that JSON strings are UTF-8 encoded |
 | "base64"   | data is base64 encoded                                   |
 ### Requests (Provider -> Adapter)
 #### add_filesystem
 Adds a filesystem.
    fs provider: {"method": "add_filesytem", "params": [<name>], "id": <id>}
    webfuse daemon: {"result": {"id": <name>}, "id": <id>}
 | Item        | Data type | Description                     |
 | ----------- | ----------| ------------------------------- |
 | name        | string    | name and id of filesystem       |
 #### authtenticate
 Authenticate the provider.  
 If authentication is enabled, a provider must be authenticated by the adapter before filesystems can be added.
    fs provider: {"method": "authenticate", "params": [<type>, <credentials>], "id": <id>}
    webfuse daemon: {"result": {}, "id": <id>}
 | Item        | Data type | Description                     |
 | ----------- | ----------| ------------------------------- |
 | type        | string    | authentication type (see below) |
 | credentials | object    | credentials to authenticate     |
 ##### authentication types
 -   **username**: authenticate via username and password  
    `{"username": <username>, "password": <password>}`
 ## Authentication
 By default, webfuse daemon will redirect each filesystem call to the first connected provider without any authentication.
 This might be good for testing purposes or when an external authentication mechanism is used. In some use cases, explicit authentication is needed. Therefore, authentication can be enabled within webfuse daemon.
 When authentication is enabled, filesystem calls are only redirected to a connected provider, after `authenticate`
 has succeeded.
 ![authenticate](doc/authenticate.png)
 ### Enable authentication
 Authentication is enabled, if one or more authenticators are registered via `wf_server_config`.
    static bool authenticate(struct wf_credentials * creds, void * user_data)
    {
        char const * username = wf_credentials_get(creds, "username");
        char const * password = wf_credentials_get(creds, "password");
       return ((NULL != username) && (0 == strcmp(username, "bob")) &&
               (NULL != password) && (0 == strcmp(password, "???")));
    }
    wf_server_config * config = wf_server_config_create();
    wf_server_config_add_authenticator(config, "username", &authenticate, NULL);
    wf_server * server = wf_server_create(config);
    //...
 ### Authenticator types and credentidals
 Each authenticator is identified by a user defined string, called `type`. The type is provided by the `authenticate` request, so you can define different authenticators for different authentication types, e.g. username, certificate, token.
 Actually, only one type is used: **username**  
 **It is strongly recommended to prefix custom authenticator types with an underscore (`_`) to avoid name clashes.**
 The `wf_credentials`struct represents a map to access credentials as key-value pairs, where both, key and value, are of type string.
 #### username
 The authenticator type **username** is used to authenticate via username and password. Valid credentials should contain two keys.
 -   **username** refers to the name of the user
 -   **password** refers to the password of the user
 **Note** that no further encryption is done, so this authenticator type should not be used over unencrypted websocket connections.
 ## Build
 To install dependencies, see below.
    cd webfuse
    mkdir .build
    cd .build
    cmake ..
    make
 ### Build options
 By default, unit tests are enabled. You can disable them using the following cmake options:
 -   **WITHOUT_TESTS**: disable tests  
    `cmake -DWITHOUT_TESTS=ON ..`
 Since webfuse consists of two libraries, it is possible to disable one of them
 in order to reduce build dependencies.  
 *Note that unit tests are only available, when both libraries are built.*
 -   **WITHOUT_ADAPTER**: omit adapter library  
    `cmake -DWITHOUT_ADAPTER=ON`
 -   **WIHTOU_PROVIDER**: omit provider library
    `cmake -DWITHOUT_PROVIDER=ON`
 ## Dependencies
 -   [libfuse3](https://github.com/libfuse/libfuse/)
 -   [libwebsockets](https://libwebsockets.org/)
 -   [Jansson](https://jansson.readthedocs.io)
 -   [GoogleTest](https://github.com/google/googletest) *(optional)*
 ### Installation from source
 #### libfuse
 To install libfuse, meson is needed. Please refer to [meson quick guide](https://mesonbuild.com/Quick-guide.html) for setup instructions.
    wget -O fuse-3.8.0.tar.gz https://github.com/libfuse/libfuse/archive/fuse-3.8.0.tar.gz
    tar -xf fuse-3.8.0.tar.gz
    cd libfuse-fuse-3.8.0
    mkdir .build
    cd .build
    meson ..
    ninja
    sudo ninja install
 #### libwebsockets
    wget -O libwebsockets-3.2.0.tar.gz https://github.com/warmcat/libwebsockets/archive/v3.2.0.tar.gz
    tar -xf libwebsockets-3.2.0.tar.gz
    cd libwebsockets-3.2.0
    mkdir .build
    cd .build
    cmake ..
    make
    sudo make install
 #### Jansson
    wget -O libjansson-2.12.tar.gz https://github.com/akheron/jansson/archive/v2.12.tar.gz
    tar -xf libjansson-2.12.tar.gz
    cd jansson-2.12
    mkdir .build
    cd .build
    cmake ..
    make
    sudo make install
 #### GoogleTest
 Installation of GoogleTest is optional webfuse library, but required to compile tests.
    wget -O gtest-1.10.0.tar.gz https://github.com/google/googletest/archive/release-1.10.0.tar.gz
    tar -xf gtest-1.10.0.tar.gz
    cd googletest-release-1.10.0
    mkdir .build
    cd .build
    cmake ..
    make
    sudo make install
--- a/doc/api.md
+++ b/doc/api.md
@ -0,0 +1,55 @@
 # Webfuse API introduction
 This introduction provides a general overview to webfuse API.
 Please refer to the [build instructions](build.md) to generate API reference documentation.
 ## Contents
 -   [Authentication](#Authentication)
 ## Authentication
 By default, webfuse daemon will redirect each filesystem call to the first connected provider without any authentication.
 This might be good for testing purposes or when an external authentication mechanism is used. In some use cases, explicit authentication is needed. Therefore, authentication can be enabled within webfuse daemon.
 When authentication is enabled, filesystem calls are only redirected to a connected provider, after `authenticate`
 has succeeded.
 ![authenticate](authenticate.png)
 ### Enable authentication
 Authentication is enabled, if one or more authenticators are registered via `wf_server_config`.
    static bool authenticate(struct wf_credentials * creds, void * user_data)
    {
        char const * username = wf_credentials_get(creds, "username");
        char const * password = wf_credentials_get(creds, "password");
       return ((NULL != username) && (0 == strcmp(username, "bob")) &&
               (NULL != password) && (0 == strcmp(password, "???")));
    }
    wf_server_config * config = wf_server_config_create();
    wf_server_config_add_authenticator(config, "username", &authenticate, NULL);
    wf_server * server = wf_server_create(config);
    //...
 ### Authenticator types and credentidals
 Each authenticator is identified by a user defined string, called `type`. The type is provided by the `authenticate` request, so you can define different authenticators for different authentication types, e.g. username, certificate, token.
 Actually, only one type is used: **username**  
 **It is strongly recommended to prefix custom authenticator types with an underscore (`_`) to avoid name clashes.**
 The `wf_credentials`struct represents a map to access credentials as key-value pairs, where both, key and value, are of type string.
 #### username
 The authenticator type **username** is used to authenticate via username and password. Valid credentials should contain two keys.
 -   **username** refers to the name of the user
 -   **password** refers to the password of the user
 **Note** that no further encryption is done, so this authenticator type should not be used over unencrypted websocket connections.
--- a/doc/build.md
+++ b/doc/build.md
@ -0,0 +1,92 @@
 # Build Instructions
 To install dependencies, see below.
    cd webfuse
    mkdir .build
    cd .build
    cmake ..
    make
 ## Build options
 By default, unit tests are enabled. You can disable them using the following cmake options:
 -   **WITHOUT_TESTS**: disable tests  
    `cmake -DWITHOUT_TESTS=ON ..`
 Since webfuse consists of two libraries, it is possible to disable one of them
 in order to reduce build dependencies.  
 *Note that unit tests are only available, when both libraries are built.*
 -   **WITHOUT_ADAPTER**: omit adapter library  
    `cmake -DWITHOUT_ADAPTER=ON`
 -   **WIHTOU_PROVIDER**: omit provider library
    `cmake -DWITHOUT_PROVIDER=ON`
 ## Create API documentation
 To create API documentation, you must install doxygen and dot first.
 After that, run doxygen in the project root directory.
    doxygen
 After that, you will find the API documentation in the doc/api subdirectory.
 ## Dependencies
 -   [libfuse3](https://github.com/libfuse/libfuse/)
 -   [libwebsockets](https://libwebsockets.org/)
 -   [Jansson](https://jansson.readthedocs.io)
 -   [GoogleTest](https://github.com/google/googletest) *(optional)*
 ### Installation from source
 #### libfuse
 To install libfuse, meson is needed. Please refer to [meson quick guide](https://mesonbuild.com/Quick-guide.html) for setup instructions.
    wget -O fuse-3.8.0.tar.gz https://github.com/libfuse/libfuse/archive/fuse-3.8.0.tar.gz
    tar -xf fuse-3.8.0.tar.gz
    cd libfuse-fuse-3.8.0
    mkdir .build
    cd .build
    meson ..
    ninja
    sudo ninja install
 #### libwebsockets
    wget -O libwebsockets-3.2.0.tar.gz https://github.com/warmcat/libwebsockets/archive/v3.2.0.tar.gz
    tar -xf libwebsockets-3.2.0.tar.gz
    cd libwebsockets-3.2.0
    mkdir .build
    cd .build
    cmake ..
    make
    sudo make install
 #### Jansson
    wget -O libjansson-2.12.tar.gz https://github.com/akheron/jansson/archive/v2.12.tar.gz
    tar -xf libjansson-2.12.tar.gz
    cd jansson-2.12
    mkdir .build
    cd .build
    cmake ..
    make
    sudo make install
 #### GoogleTest
 Installation of GoogleTest is optional webfuse library, but required to compile tests.
    wget -O gtest-1.10.0.tar.gz https://github.com/google/googletest/archive/release-1.10.0.tar.gz
    tar -xf gtest-1.10.0.tar.gz
    cd googletest-release-1.10.0
    mkdir .build
    cd .build
    cmake ..
    make
    sudo make install
--- a/doc/filesystem.png
+++ b/doc/filesystem.png
--- a/doc/filesystem.uml
+++ b/doc/filesystem.uml
@ -1,16 +0,0 @@
@startuml
 salt
 {
 {T
 + mount_point
 ++ fwupdate
 +++ default -> 7c029f81-6bdf-4d3c-82dc-26f748164012
 +++ 7c029f81-6bdf-4d3c-82dc-26f748164012
 ++++ update.raucb
 +++ f93de23b-4535-4a47-a287-a381b78a11b8
 ++++ update.raucb
 }
 }
@enduml
--- a/doc/protocol.md
+++ b/doc/protocol.md
@ -0,0 +1,253 @@
 # Webfuse Protocol
 ## Requests, responses and notifications
 There are three types of messages, used for communication between webfuse daemon and filesystem provider. All message types are encoded in [JSON](https://www.json.org/) and strongly inspired by [JSON-RPC](https://www.jsonrpc.org/).
 ### Request
 A request is used by a sender to invoke a method on the receiver. The sender awaits a response from the receiver. Since requests and responses can be sendet or answered in any order, an id is provided in each request to identify it.
    {
      "method": <method_name>,
      "params": <params>,
      "id"    : <id>
    }
 | Item        | Data type | Description                       |
 | ----------- |:---------:| --------------------------------- |
 | method_name | string    | name of the method to invoke      |
 | params      | array     | method specific parameters        |
 | id          | integer   | id, which is repeated in response |
 ### Response
 A response is used to answer a prior request. There are two kinds of responses:
 #### Successful Results
    {
       "result": <result>,
       "id": <id>
    }
 | Item        | Data type | Description             |
 | ----------- |:---------:| ----------------------- |
 | result      | any       | request specific result |
 | id          | integer   | id, same as request     |
 #### Error notifications
    {
       "error": {
         "code": <code>
       },
       "id": <id>
    }
 | Item        | Data type | Description         |
 | ----------- |:---------:| ------------------- |
 | code        | integer   | error code          |
 | id          | integer   | id, same as request |
 #### Error codes
 | Symbolic name      | Code      | Description            |
 | ------------------ | ---------:| ---------------------- |
 | GOOD               | 0         | no error               |
 | BAD                | 1         | generic error          |
 | BAD_NOTIMPLEMENTED | 2         | method not implemented |
 | BAD_TIMEOUT        | 3         | timeout occured        |
 | BAD_BUSY           | 4         | resource busy          |
 | BAD_FORMAT         | 5         | invalid formt          |
 | BAD_NOENTRY        | 101       | invalid entry          |
 | BAD_ACCESS_DENIED  | 102       | access not allowed     |
 ### Notification
 Notfications are used to inform a receiver about something. Unlike requests, notifications are not answered. Therefore, an id is not supplied.
    {
      "method": <method_name>,
      "params": <params>
    }
 | Item        | Data type | Description                       |
 | ----------- |:---------:| --------------------------------- |
 | method_name | string    | name of the method to invoke      |
 | params      | array     | method specific parameters        |
 ## Requests (Adapter -> Provider)
 ### lookup
 Retrieve information about a filesystem entry by name.
    webfuse daemon: {"method": "lookup", "params": [<filesystem>, <parent>, <name>], "id": <id>}
    fs provider: {"result": {
        "inode": <inode>,
        "mode" : <mode>,
        "type" : <type>,
        "size" : <size>,
        "atime": <atime>,
        "mtime": <mtime>,
        "ctime": <ctime>
        }, "id": <id>}
 | Item        | Data type       | Description                                 |
 | ----------- | --------------- | ------------------------------------------- |
 | filesystem  | string          | name of the filesystem                      |
 | parent      | integer         | inode of parent directory (1 = root)        |
 | name        | string          | name of the filesystem object to look up    |
 | inode       | integer         | inode of the filesystem object              |
 | mode        | integer         | unix file mode                              |
 | type        | "file" or "dir" | type of filesystem object                   |
 | size        | integer         | required for files; file size in bytes      |
 | atime       | integer         | optional; unix time of last access          |
 | mtime       | integer         | optional; unix time of last modification    |
 | ctime       | intefer         | optional; unix time of last metadata change |
 ### getattr
 Get file attributes.
    webfuse daemon: {"method": "getattr", "params": [<filesystem>, <inode>], "id": <id>}
    fs provider: {"result": {
        "mode" : <mode>,
        "type" : <type>,
        "size" : <size>,
        "atime": <atime>,
        "mtime": <mtime>,
        "ctime": <ctime>
        }, "id": <id>}
 | Item        | Data type       | Description                                 |
 | ----------- | --------------- | ------------------------------------------- |
 | filesystem  | string          | name of the filesystem                      |
 | inode       | integer         | inode of the filesystem object              |
 | mode        | integer         | unix file mode                              |
 | type        | "file" or "dir" | type of filesystem object                   |
 | size        | integer         | required for files; file size in bytes      |
 | atime       | integer         | optional; unix time of last access          |
 | mtime       | integer         | optional; unix time of last modification    |
 | ctime       | intefer         | optional; unix time of last metadata change |
 ### readdir
 Read directory contents.  
 Result is an array of name-inode pairs for each entry. The generic entries
 "." and ".." should also be provided.
    webfuse daemon: {"method": "readdir", "params": [<filesystem>, <dir_inode>], "id": <id>}
    fs provider: {"result": [
        {"name": <name>, "inode": <inode>},
        ...
        ], "id": <id>}
 | Item        | Data type       | Description                    |
 | ----------- | --------------- | ------------------------------ |
 | filesystem  | string          | name of the filesystem         |
 | dir_inode   | integer         | inode of the directory to read |
 | name        | integer         | name of the entry              |
 | inode       | integer         | inode of the entry             |
 ### open
 Open a file.
    webfuse daemon: {"method": "readdir", "params": [<filesystem>, <inode>, <flags>], "id": <id>}
    fs provider: {"result": {"handle": <handle>}, "id": <id>}
 | Item        | Data type | Description                   |
 | ----------- | ----------| ----------------------------- |
 | filesystem  | string    | name of the filesystem        |
 | inode       | integer   | inode of the file             |
 | flags       | integer   | access mode flags (see below) |
 | handle      | integer   | handle of the file            |
 #### Flags
 | Symbolic name | Code      | Description                 |
 | --------------| ---------:| --------------------------- |
 | O_ACCMODE     | 0x003     | access mode mask            |
 | O_RDONLY      | 0x000     | open for reading only       |
 | O_WRONLY      | 0x001     | open for writing only       |
 | O_RDWR        | 0x002     | open for reading an writing |
 | O_CREAT       | 0x040     | create (a new) file         |
 | O_EXCL        | 0x080     | open file exclusivly        |
 | O_TRUNC       | 0x200     | open file to truncate       |
 | O_APPEND      | 0x400     | open file to append         |
 ### close
 Informs filesystem provider, that a file is closed.  
 Since `close` is a notification, it cannot fail.
    webfuse daemon: {"method": "close", "params": [<filesystem>, <inode>, <handle>, <flags>], "id": <id>}
 | Item        | Data type | Description                  |
 | ----------- | ----------| ---------------------------- |
 | filesystem  | string    | name of the filesystem       |
 | inode       | integer   | inode of the file            |
 | handle      | integer   | handle of the file           |
 | flags       | integer   | access mode flags (see open) |
 ### read
 Read from an open file.
    webfuse daemon: {"method": "close", "params": [<filesystem>, <inode>, <handle>, <offset>, <length>], "id": <id>}
    fs provider: {"result": {
        "data": <data>,
        "format": <format>,
        "count": <count>
        }, "id": <id>}
 | Item        | Data type | Description                   |
 | ----------- | ----------| ----------------------------- |
 | filesystem  | string    | name of the filesystem        |
 | inode       | integer   | inode of the file             |
 | handle      | integer   | handle of the file            |
 | offset      | integer   | Offet to start read operation |
 | length      | integer   | Max. number of bytes to read  |
 | data        | integer   | handle of the file            |
 | format      | string    | Encoding of data (see below)  |
 | count       | integer   | Actual number of bytes read   |
 #### Format
 | Format     | Description                                              |
 | ---------- | -------------------------------------------------------- |
 | "identiy"  | Use data as is; note that JSON strings are UTF-8 encoded |
 | "base64"   | data is base64 encoded                                   |
 ## Requests (Provider -> Adapter)
 ### add_filesystem
 Adds a filesystem.
    fs provider: {"method": "add_filesytem", "params": [<name>], "id": <id>}
    webfuse daemon: {"result": {"id": <name>}, "id": <id>}
 | Item        | Data type | Description                     |
 | ----------- | ----------| ------------------------------- |
 | name        | string    | name and id of filesystem       |
 ### authtenticate
 Authenticate the provider.  
 If authentication is enabled, a provider must be authenticated by the adapter before filesystems can be added.
    fs provider: {"method": "authenticate", "params": [<type>, <credentials>], "id": <id>}
    webfuse daemon: {"result": {}, "id": <id>}
 | Item        | Data type | Description                     |
 | ----------- | ----------| ------------------------------- |
 | type        | string    | authentication type (see below) |
 | credentials | object    | credentials to authenticate     |
 #### authentication types
 -   **username**: authenticate via username and password  
    `{"username": <username>, "password": <password>}`