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falk-werner_webfuse-provider/doc/protocol.md
Falk Werner 1a1367eae7 fixed typo
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# 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_filesystem", "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>}`
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