mirror of
https://github.com/rustdesk/rustdesk.git
synced 2024-12-04 20:21:35 +08:00
162 lines
5.5 KiB
Markdown
162 lines
5.5 KiB
Markdown
# clipboard
|
|
|
|
Copy files and text through network.
|
|
Main lowlevel logic from [FreeRDP](https://github.com/FreeRDP/FreeRDP).
|
|
|
|
To enjoy file copy and paste feature on Linux/OSX,
|
|
please build with `unix-file-copy-paste` feature.
|
|
|
|
TODO: Move this lib to a separate project.
|
|
|
|
## How it works
|
|
|
|
Terminalogies:
|
|
|
|
- cliprdr: this module
|
|
- local: the endpoint which initiates a file copy events
|
|
- remote: the endpoint which paste the file copied from `local`
|
|
|
|
The main algorithm of copying and pasting files is from
|
|
[Remote Desktop Protocol: Clipboard Virtual Channel Extension](https://winprotocoldoc.blob.core.windows.net/productionwindowsarchives/MS-RDPECLIP/%5bMS-RDPECLIP%5d.pdf),
|
|
and could be concluded as:
|
|
|
|
0. local and remote notify each other that it's ready.
|
|
1. local subscribes/listening to the system's clipboard for file copy
|
|
2. local once got file copy event, notice the remote
|
|
3. remote confirms receive and try pulls the file list
|
|
4. local updates its file-list, the remote flushes pulled file list to the clipboard
|
|
5. remote OS or desktop manager initiates a paste, making other programs reading
|
|
clipboard files. Convert those reading requests to RPCs
|
|
|
|
- on Windows, all file reading will go through the stream file API
|
|
- on Linux/OSX, FUSE is used for converting reading requests to RPCs
|
|
- in case of local clipboard been transferred back
|
|
and leading to a dead loop,
|
|
all file copy event pointing at the FUSE directory will be ignored
|
|
|
|
6. finishing pasting all files one by one.
|
|
|
|
In a perspective of network data transferring:
|
|
|
|
```mermaid
|
|
sequenceDiagram
|
|
participant l as Local
|
|
participant r as Remote
|
|
note over l, r: Initialize
|
|
l ->> r: Monitor Ready
|
|
r ->> l: Monitor Ready
|
|
loop Get clipboard update
|
|
l ->> r: Format List (I got update)
|
|
r ->> l: Format List Response (notified)
|
|
r ->> l: Format Data Request (requests file list)
|
|
activate l
|
|
note left of l: Retrive file list from system clipboard
|
|
l ->> r: Format Data Response (containing file list)
|
|
deactivate l
|
|
note over r: Update system clipboard with received file list
|
|
end
|
|
loop Some application requests copied files
|
|
note right of r: application reads file from x to x+y
|
|
note over r: the file is the a-th file on list
|
|
r ->> l: File Contents Request (read file a offset x size y)
|
|
activate l
|
|
note left of l: Find a-th file on list, read from x to x+y
|
|
l ->> r: File Contents Response (contents of file a offset x size y)
|
|
deactivate l
|
|
end
|
|
```
|
|
|
|
Note: In actual implementation, both sides could play send clipboard update
|
|
and request file contents.
|
|
There is no such limitation that only local can update clipboard
|
|
and copy files to remote.
|
|
|
|
## impl
|
|
|
|
### windows
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
The protocol was originally designed as an extension of the Windows RDP,
|
|
so the specific message packages fits windows well.
|
|
|
|
When starting cliprdr, a thread is spawn to create a invisible window
|
|
and to subscribe to OLE clipboard events.
|
|
The window's callback (see `cliprdr_proc` in `src/windows/wf_cliprdr.c`) was
|
|
set to handle a variaty of events.
|
|
|
|
Detailed implementation is shown in pictures above.
|
|
|
|
### Linux/OSX
|
|
|
|
The Cliprdr Server implementation has mainly 3 parts:
|
|
|
|
- Clipboard Client
|
|
- Local File list
|
|
- FUSE server
|
|
|
|
#### Clipboard Client
|
|
|
|
The clipboard client has a thread polling for file urls on clipboard.
|
|
|
|
If the client found any updates of file urls,
|
|
after filtering out those pointing to our FUSE directory or duplicated,
|
|
send format list directly to remote.
|
|
|
|
The cliprdr server also uses clipboard client for setting clipboard,
|
|
or retrive paths from system.
|
|
|
|
#### Local File List
|
|
|
|
The local file list is a temperary list of file metadata.
|
|
When receiving file contents PDU from peer, the server picks
|
|
out the file requested and open it for reading if necessary.
|
|
|
|
Also when receiving Format Data Request PDU from remote asking for file list,
|
|
the local file list should be rebuilt from file list retrieved from Clipboard Client.
|
|
|
|
Some caching and preloading could done on it since applications are likely to read
|
|
on the list sequentially.
|
|
|
|
#### FUSE server
|
|
|
|
The FUSE server could convert POSIX file reading request to File Contents
|
|
Request/Response RPCs.
|
|
|
|
When received file list from remote,
|
|
the FUSE server will figure out the file system tree and rearrange its content.
|
|
|
|
#### Groceries
|
|
|
|
- The protocol was originally implemented for windows,
|
|
so paths in PDU will all be converted to DOS formats in UTF-16 LE encoding,
|
|
and datetimes will be converted to LDAP timestamp instead of
|
|
unix timestamp
|
|
|
|
```text
|
|
UNIX
|
|
/usr/bin/rustdesk
|
|
->
|
|
DOS
|
|
\usr\bin\rustdesk
|
|
```
|
|
|
|
- To better fit for preserving permissions on unix-like platforms,
|
|
a reserved area of FileDescriptor PDU
|
|
|
|
- you may notice
|
|
the mountpoint is still occupied after the application quits.
|
|
That's because the FUSE server was not mounted with `AUTO_UNMOUNT`.
|
|
- It's hard to implement gressful shutdown for a multi-processed program
|
|
- `AUTO_UNMOUNT` was not enabled by default and requires enable
|
|
`user_allow_other` in configure. Letting users edit such global
|
|
configuration to use this feature might not be a good idea.
|
|
- use [`umount()`](https://man7.org/linux/man-pages/man2/umount.2.html)
|
|
syscall to unmount will also require that option.
|
|
- we currently directly call [`umount`](https://man7.org/linux/man-pages/man8/umount.8.html)
|
|
program to unmount dangling FUSE server. It worked perfectly for now.
|