Project to mess around with passing file descriptors between
applications using UNIX-domain sockets and SCM_RIGHTS. Some of the C
code was taken from this amazing Cloudflare blog article. The
Python code was inspired by the Python docs as well as bits
from the standard library. Also, credit to Cindy Sridharan
for inspiring me to mess around with this.
It was interesting to discover that Python 3.9 added support for this
into the core socket module. It has also existed for some time in
the multiprocessing.reduction module but is not very well documented.
This implementation is pretty naive and more of a toy than anything so I'm sure it has quite a few sharp edges that weren't accounted for or were not evident when writing.
-----------------------------------
| | |
V +-------------+ +---------------+
o/ | | | |
User /| --> | Quarterback | --> | Wide Receiver |
/ \ | | | |
+-------------+ +---------------+
Start by running the Wide Receiver first. This is the last element
depicted in the flow above. It gets passed the user's file descriptor
from Quarterback.
$ python3 wr.py
Now, start Quarterback.
$ ./qb
Finally, connect with nc to see the magic. Whatever is typed
should be echoed back.
$ nc localhost 8000
Output should look like the following:
User
$ nc localhost 8000
Hello from Quarterback on PID (373)!
Hello from Wide Receiver on PID (520)!
foo
foo
bar
bar
Quarterback
$ ./qb
Starting Quarterback with PID (373)
Connecting to UNIX socket (fd-pass.sock)
Connected to UNIX socket (fd-pass.sock)
Listening on 0.0.0.0:8000
Handling connection from (127.0.0.1:60316)
Closing connection from (127.0.0.1:60316)
^CProcessing signal (Interrupt: 2)
Shutting down
Wide Receiver
$ python wr.py
Starting Wide Receiver on PID (520)
Listening for messages on (fd-pass.sock)
Handling connection from (fd-pass.sock)
Handling connection from (127.0.0.1:60316)
Closing connection from (127.0.0.1:60316)
Connection on (fd-pass.sock) closed
^CProcessing signal (SIGINT)
Shutting down
TODO
Builds use gcc.
$ make
TODO
TODO
TODO
TODO