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enhance protocol documentation
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Falk Werner
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doc/protocol.md
506
doc/protocol.md
@ -1,4 +1,36 @@
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# Webufse 2 Protocol
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# Webfuse 2 Protocol
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## Scope
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This document describes the webfuse 2 communication protocol. The protocol is used to transfer messages between a `webfuse2 service` and a `webfuse2 provider`. In contrast to `legacy webfuse`, which is based on `JSON RPC` the `webfuse2 protocol` is a binary protocol.
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## Definitions
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### Webfuse2 Service
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A `webfuse2 service` is both,
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- a [websocket](https://en.wikipedia.org/wiki/WebSocket) service providing the `webfuse2` protocol
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- a [fuse](https://github.com/libfuse/libfuse) filesystem attached to a local mountpoint
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The `webfuse2 service` awaits incoming connections from a `webfuse2 provider`. Once connected, it communicates all the filesystem requests originated by the `libfuse` to the connected `webfuse2 provider` using the `websocket`-based `webfuse2 protocol`.
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By doing so, `webfuse2` allows to inject a filesystem to a remote device.
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### Webfuse2 Provider
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A `webfuse2 provider` provides a filesystem to a remote device using the `websocket`-based `webfuse2 protocol`. Therefore, a `webfuse2 provider` implements a `websocket` client.
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## Message exchange
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Once connected, the `webfuse2 protocol` implements a strict request-response scheme, where
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- all requests are send by the `webfuse2 service`,
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- all requests require a response and
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- all responses are send by the `webfuse2 provider`
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Note that this communication is reversed the typical client-server-communication scheme. In `webfuse2` the `webfuse2 serive` (server) sends all the requests and the `webfuse provider` (client) sends the responses.
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For message transfer, the [websocket](https://en.wikipedia.org/wiki/WebSocket) protocol is used. All messages are in binary form, plain text messages are never used by the `webfuse2 protocol`.
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## Endianness
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@ -86,7 +118,70 @@ For instance, the uint32 value 1 will be transferred as
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| EXDEV | -18 | improper link |
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| EWOULDBLOCK | -11 | resource temporarily unavailable |
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#### access mode
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| Mode | Value | Description |
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| ---- | ----- | ----------- |
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| F_OK | 0 | Tests, whether the file exists |
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| X_OK | 1 | Tests, whether the file is executable |
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| W_OK | 2 | Tests, whether the file is writable |
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| R_OK | 4 | Tests, whether the file is readable |
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#### mode
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_Note that the following numbers are in `octal` notation._
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| Fields and Flags | Mask | Description |
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| ---------------- | -------- | ----------- |
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| Protection mask | 0o000777 | Cointains the file protection flags (rwx for owner, group and others) |
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| Sticky mask | 0o007000 | Sticky bits |
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| S_ISVTX | 0o001000 | Sticky bit |
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| S_ISGID | 0o002000 | Set-Group-ID bit |
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| S_ISUID | 0o004000 | Set-User-ID bit |
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| Filetype mask | 0o170000 | Filetype mask |
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| S_IFREG | 0o100000 | regular file |
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| S_IFDIR | 0o040000 | directory |
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| S_IFCHR | 0o020000 | character device |
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| S_IFBLK | 0o060000 | block device |
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| S_IFIFO | 0o010000 | named pipe |
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| S_IFLNK | 0o120000 | link |
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| S_IFSOCK | 0o140000 | socket |
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#### open_flags
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_Note that the following numbers are in `octal` notation._
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| Flags | Value | Description |
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| ---------------- | -------- | ----------- |
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| O_ACCMODE | 0o03 | Access mode mask |
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| O_RDONLY | 0o00 | open file read-only |
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| O_WRONLY | 0o01 | open file write-only |
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| O_RDWR | 0o02 | open file for reading and writing |
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| O_APPEND | 0o000002000 | open file in append mode |
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| O_ASYNC | 0o000020000 | enable signal-driven I/O |
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| O_CLOEXEC | 0o002000000 | enable close-on-exec |
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| O_CREAT | 0o000000100 | create file if path does not exists |
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| O_DIRECT | 0o000040000 | try to minimize cache effects on I/O |
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| O_DIRECTORY | 0o000200000 | open a directory |
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| O_DSYNC | 0o000010000 | write with synchronized I/O data integrity |
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| O_EXCL | 0o000000200 | ensure that file exists when specified in conjunction with O_CREATE |
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| O_LARGEFILE | 0o000100000 | allow large files to be opened |
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| O_NOATIME | 0o001000000 | do not update file last access time |
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| O_NOCTTY | 0o000000400 | make device the process's controlling terminal |
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| O_NOFOLLOW | 0o000400000 | fail to open, if basename is a symbolic link |
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| O_NONBLOCK | 0o000004000 | open in nonblocking mode |
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| O_NDELAY | 0o000004000 | open in nonblocking mode |
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| O_PATH | 0o010000000 | see manual entry of `open(2)` for details |
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| O_SYNC | 0o004010000 | write using synchronized I/O |
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| O_TMPFILE | 0o020200000 | create an unnamed temporary file |
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| O_TRUNC | 0o000001000 | truncate fole to length 0 |
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#### rename_flags
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| Flag | Value | Description |
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| ---------------- | ----- | ----------- |
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| RENAME_NOREPLACE | 1 | do not overwrite the new file |
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| RENAME_EXCHANGE | 2 | atomically exchange the files |
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### Complex Types
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@ -137,22 +232,423 @@ For instance, the uint32 value 1 will be transferred as
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#### statistics
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## Messages
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## Message
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| Field | Type | Descripton |
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| ------- | ---- | ---------- |
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| id | u32 | Unique ID of the message |
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| type | u8 | Type of the message |
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| payload | u8[] | Payload according to the message type |
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The `id` is just a number without any meaning for the `webfuse2 provider`. It is set by the `webfuse2 service` of a request and is copied by the `webfuse2 provider` to the response. A `webfuse2 service` implementation might choose to keep track on pending requests using the `id`.
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### Erroneous Responses
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Most responses contain a `result` encoding the status of the operation. While successful responses may contain additional data, erroneous responses must not be decoded by a `webfuse2 service` implementation beyond the `result` value.
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### Message Types
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_Note that the following numbers are in `hexadecimal` notation._
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| Method | Request | Response |
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| -------- | ------- | -------- |
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| access | 0x01 | 0x81 |
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| getattr | 0x02 | 0x82 |
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| readlink | 0x03 | 0x83 |
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| symlink | 0x04 | 0x84 |
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| link | 0x05 | 0x85 |
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| rename | 0x06 | 0x86 |
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| chmod | 0x07 | 0x87 |
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| chown | 0x08 | 0x88 |
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| truncate | 0x09 | 0x89 |
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| fsync | 0x0a | 0x8a |
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| open | 0x0b | 0x8b |
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| mknod | 0x0c | 0x8c |
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| create | 0x0d | 0x8d |
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| release | 0x0e | 0x8e |
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| unlink | 0x0f | 0x8f |
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| read | 0x10 | 0x90 |
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| write | 0x11 | 0x91 |
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| mkdir | 0x12 | 0x92 |
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| readdir | 0x13 | 0x93 |
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| rmdir | 0x14 | 0x94 |
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| statfs | 0x15 | 0x95 |
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| utimens | 0x16 | 0x96 |
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## Methods
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### access
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#### Request
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| Field | Data Type | Description |
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| ----- | ---------------- | ----------- |
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| | uint32 | message id |
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| type | uint8 | message type (0x00) |
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| id | u32 | message id |
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| type | u8 | message type (0x01) |
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| path | string | |
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| mode | access_mode (i8) |
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#### Response
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| Field |
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### getattr
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### readlink
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### symlink
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### link
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### rename
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### chmod
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### chown
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### truncate
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### fsync
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### open
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### mknod
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### create
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### release
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### unlink
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### read
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### write
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### mkdir
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### readdir
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### rmdir
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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#### Response
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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| id | u32 | message id |
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| type | u8 | message type (0x81) |
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| result | result | operation status |
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### statfs
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#### Request
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| Field | Data Type | Description |
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| ------ | --------- | ----------- |
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||||
| id | u32 | message id |
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| type | u8 | message type (0x81) |
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||||
|
||||
#### Response
|
||||
|
||||
| Field | Data Type | Description |
|
||||
| ------ | --------- | ----------- |
|
||||
| id | u32 | message id |
|
||||
| type | u8 | message type (0x81) |
|
||||
| result | result | operation status |
|
||||
|
||||
### utimens
|
||||
|
||||
#### Request
|
||||
|
||||
| Field | Data Type | Description |
|
||||
| ------ | --------- | ----------- |
|
||||
| id | u32 | message id |
|
||||
| type | u8 | message type (0x81) |
|
||||
|
||||
#### Response
|
||||
|
||||
| Field | Data Type | Description |
|
||||
| ------ | --------- | ----------- |
|
||||
| id | u32 | message id |
|
||||
| type | u8 | message type (0x81) |
|
||||
| result | result | operation status |
|
||||
|
||||
Loading…
Reference in New Issue
Block a user