diff options
Diffstat (limited to 'lib9p')
| -rw-r--r-- | lib9p/idl/2003-9P2000.p9p.9p.wip | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/lib9p/idl/2003-9P2000.p9p.9p.wip b/lib9p/idl/2003-9P2000.p9p.9p.wip new file mode 100644 index 0000000..c42584f --- /dev/null +++ b/lib9p/idl/2003-9P2000.p9p.9p.wip @@ -0,0 +1,48 @@ +# lib9p/idl/2003-9P2000.p9p.9p - Definitions of plan9port extension messages +# +# Copyright (C) 2025 Luke T. Shumaker <lukeshu@lukeshu.com> +# SPDX-License-Identifier: AGPL-3.0-or-later + +# Plan 9 from User Space (a.k.a. plan9port)'s lib9pclient:fsopenfd(3) +# and 9pserve(4) proxy server (which takes the place of the Plan 9 +# kernel) add a special-purpose `openfd` command to 9P2000. +# +# https://9fans.github.io/plan9port/man/man9/openfd.htlm +# https://github.com/9fans/plan9port/blob/master/man/man9/openfd.9p +# https://github.com/9fans/plan9port/commit/32f69c36e0eec1227934bbd34854bfebd88686f2 +# https://github.com/9fans/plan9port/pull/692 + +# BUG: There is no version-string for this extension; plan9port still +# calls it vanilla "9P2000". + +from ./2002-9P2000.9p import * + +# On Plan 9 the usual 9P client is the kernel, not normal userspace +# programs. The kernel multiplexes multiple userspace processes onto +# a single 9P connection; the userspace programs make 9P calls by +# making syscalls. plan9port emulates this by having mock syscalls +# that make 9P client calls over an AF_UNIX socket to a local +# `9pserve` daemon that does the multiplexing (you add an "fs" prefix; +# e.g. you replace syscall:`open()` with lib9pclient:`fsopen()`). +# +# "Unfortunately", programs in plan9port must deal both with 9P files +# and native "Unix" files; and need to turn an 9P FID into a native +# file descriptor. To do this, the `9pserve` program and lib9pclient +# add an extension call to 9P2000: Topenfd/Ropenfd/fsopenfd(). +# +# An AF_UNIX socket has the ability to send a file descriptor over it +# via an out-of-band "socket control message" ("CMSG" or "SCM"). +# +# Topenfd asks 9pserve to create a socketpair() file descriptor that +# 9pserve will pump to/from a FID, and then send that pipe file +# descriptor over a control-message to the client program. +# +# When replying, the server sends not just an in-band Ropenfd message, +# but also an out-of-band control-message with a socketpair() file +# descriptor. A successful call results in the FID being clunked. +msg Topenfd = "size[4,val=end-&size] typ[1,val=98] tag[tag] fid[fid] mode[o]" +msg Ropenfd = "size[4,val=end-&size] typ[1,val=98] tag[tag] qid[qid] iounit[4] unixfd[4]" +# BUG: The "unixfd" field nominally indicates the the file descriptor +# of the pipe, but really 9pserve doesn't know which FD it will end up +# on the client process, and lib9pclient ignores the value here and +# overwrites it with the file descriptor indicated from the CMSG |