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Message-ID: <ZeIgxGn34RHdy4qS@pengutronix.de>
Date: Fri, 1 Mar 2024 19:39:00 +0100
From: Michael Grzeschik <mgr@...gutronix.de>
To: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
Cc: Eric Van Hensbergen <ericvh@...nel.org>,
Latchesar Ionkov <lucho@...kov.net>,
Dominique Martinet <asmadeus@...ewreck.org>,
Christian Schoenebeck <linux_oss@...debyte.com>,
Jonathan Corbet <corbet@....net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
v9fs@...ts.linux.dev, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
kernel@...gutronix.de
Subject: Re: [PATCH v2 4/4] tools: usb: p9_fwd: add usb gadget packet
forwarder script
On Fri, Mar 01, 2024 at 03:26:24PM +0100, Andrzej Pietrasiewicz wrote:
>Hi Michael,
>
>W dniu 2.02.2024 o 01:05, Michael Grzeschik pisze:
>>This patch is adding an small python tool to forward 9pfs requests
>>from the USB gadget to an existing 9pfs TCP server. Since currently all
>>9pfs servers lack support for the usb transport this tool is an useful
>>helper to get started.
>>
>>Refer the Documentation section "USBG Example" in
>>Documentation/filesystems/9p.rst on how to use it.
>>
>>Signed-off-by: Michael Grzeschik <m.grzeschik@...gutronix.de>
>>
>>---
>>v1 -> v2:
>> - added usbg 9pfs detailed instructions to 9p.rst doc
>>---
>> Documentation/filesystems/9p.rst | 32 +++++++
>> tools/usb/p9_fwd.py | 194 +++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 226 insertions(+)
>>
>>diff --git a/Documentation/filesystems/9p.rst b/Documentation/filesystems/9p.rst
>>index 64439068a8fc5..264265c72ba67 100644
>>--- a/Documentation/filesystems/9p.rst
>>+++ b/Documentation/filesystems/9p.rst
>>@@ -67,6 +67,38 @@ To mount a 9p FS on a USB Host accessible via the gadget as root filesystem::
>> where mount_tag is the tag associated by the usb gadget transport. The
>> pattern is usb9pfs0, usb9pfs1, ...
>>+USBG Example
>>+============
>>+
>>+The USB host exports a filesystem, while the gadget on the USB device
>>+side makes it mountable.
>>+
>>+Diod (9pfs server) and the forwarder are on the development host, where
>>+the root filesystem is actually stored. The gadget is initialized during
>>+boot (or later) on the embedded board. Then the forwarder will find it
>>+on the USB bus and start forwarding requests.
>>+
>>+In this case the 9p requests come from the device and are handled by the
>>+host. The reason is that USB device ports are normally not available on
>>+PCs, so a connection in the other direction would not work.
>>+
>>+When using the usbg transport, for now there is no native usb host
>>+service capable to handle the requests from the gadget driver. For
>>+this we have to use the extra python tool p9_fwd.py from tools/usb.
>>+
>>+Just start the 9pfs capable network server like diod/nfs-ganesha e.g.:
>>+
>>+ $ diod -f -n -d 0 -S -l 0.0.0.0:9999 -e $PWD
>>+
>>+Then start the python transport:
>>+
>>+ $ python $kernel_dir/tools/usb/p9_fwd.py -p 9999
>>+
>>+After that the gadget driver can be used as described above.
>
>Hmm... The "described above" portion refers to <mount_tag>. How do I get my
><mount_tag> if I run diod combined with p9_fwd.py?
The mount_tag is decribing the instance of the usb gadget. So, when you
are describing only one gadget this will always be usb9pfs0.
The tools diod and p9_fwd.py don't need any mount_tag information.
9PFS can be sometimes a bit confusing, in regards of what shall be
mounted where. The filesystem path that should be shared by 9pfs
is always represented with the "aname" property.
Regards,
Michael
>>+
>>+One use-case is to use it as an alternative to NFS root booting during
>>+the development of embedded Linux devices.
>>+
>> Options
>> =======
>>diff --git a/tools/usb/p9_fwd.py b/tools/usb/p9_fwd.py
>>new file mode 100755
>>index 0000000000000..95208df11abef
>>--- /dev/null
>>+++ b/tools/usb/p9_fwd.py
>>@@ -0,0 +1,194 @@
>>+#!/usr/bin/env python3
>>+# SPDX-License-Identifier: GPL-2.0
>>+
>>+import argparse
>>+import errno
>>+import logging
>>+import socket
>>+import struct
>>+import sys
>>+import time
>>+
>>+import usb.core
>>+import usb.util
>>+
>>+
>>+class Forwarder:
>>+ HEXDUMP_FILTER = (
>>+ "".join(chr(x).isprintable() and chr(x) or "." for x in range(128)) + "." * 128
>>+ )
>>+
>>+ @staticmethod
>>+ def _log_hexdump(data):
>>+ if not logging.root.isEnabledFor(logging.TRACE):
>>+ return
>>+ L = 16
>>+ for c in range(0, len(data), L):
>>+ chars = data[c : c + L]
>>+ dump = " ".join(f"{x:02x}" for x in chars)
>>+ printable = "".join(HEXDUMP_FILTER[x] for x in chars)
>>+ line = f"{c:08x} {dump:{L*3}s} |{printable:{L}s}|"
>>+ logging.root.log(logging.TRACE, "%s", line)
>>+
>>+ def __init__(self, server):
>>+ self.stats = {
>>+ "c2s packets": 0,
>>+ "c2s bytes": 0,
>>+ "s2c packets": 0,
>>+ "s2c bytes": 0,
>>+ }
>>+ self.stats_logged = time.monotonic()
>>+
>>+ dev = usb.core.find(idVendor=0x1D6B, idProduct=0x0109)
>>+ if dev is None:
>>+ raise ValueError("Device not found")
>>+
>>+ logging.info(f"found device: {dev.bus}/{dev.address}")
>>+
>>+ # dev.set_configuration() is not necessary since g_multi has only one
>>+ usb9pfs = None
>>+ # g_multi adds 9pfs as last interface
>>+ cfg = dev.get_active_configuration()
>>+ for intf in cfg:
>>+ # we have to detach the usb-storage driver from multi gadget since
>>+ # stall option could be set, which will lead to spontaneous port
>>+ # resets and our transfers will run dead
>>+ if intf.bInterfaceClass == 0x08:
>>+ if dev.is_kernel_driver_active(intf.bInterfaceNumber):
>>+ dev.detach_kernel_driver(intf.bInterfaceNumber)
>>+
>>+ if (
>>+ intf.bInterfaceClass == 0xFF
>>+ and intf.bInterfaceSubClass == 0xFF
>>+ and intf.bInterfaceProtocol == 0x09
>>+ ):
>>+ usb9pfs = intf
>>+ if usb9pfs is None:
>>+ raise ValueError("Interface not found")
>>+
>>+ logging.info(f"claiming interface:\n{usb9pfs}")
>>+ usb.util.claim_interface(dev, usb9pfs.bInterfaceNumber)
>>+ ep_out = usb.util.find_descriptor(
>>+ usb9pfs,
>>+ custom_match=lambda e: usb.util.endpoint_direction(e.bEndpointAddress)
>>+ == usb.util.ENDPOINT_OUT,
>>+ )
>>+ assert ep_out is not None
>>+ ep_in = usb.util.find_descriptor(
>>+ usb9pfs,
>>+ custom_match=lambda e: usb.util.endpoint_direction(e.bEndpointAddress)
>>+ == usb.util.ENDPOINT_IN,
>>+ )
>>+ assert ep_in is not None
>>+ logging.info(f"interface claimed")
>>+
>>+ self.ep_out = ep_out
>>+ self.ep_in = ep_in
>>+ self.dev = dev
>>+
>>+ # create and connect socket
>>+ self.s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
>>+ self.s.connect(server)
>>+
>>+ logging.info(f"connected to server")
>>+
>>+ def c2s(self):
>>+ """forward a request from the USB client to the TCP server"""
>>+ data = None
>>+ while data is None:
>>+ try:
>>+ logging.log(logging.TRACE, "c2s: reading")
>>+ data = self.ep_in.read(self.ep_in.wMaxPacketSize)
>>+ except usb.core.USBTimeoutError:
>>+ logging.log(logging.TRACE, "c2s: reading timed out")
>>+ continue
>>+ except usb.core.USBError as e:
>>+ if e.errno == errno.EIO:
>>+ logging.debug("c2s: reading failed with %s, retrying", repr(e))
>>+ time.sleep(0.5)
>>+ continue
>>+ else:
>>+ logging.error("c2s: reading failed with %s, aborting", repr(e))
>>+ raise
>>+ size = struct.unpack("<I", data[:4])[0]
>>+ while len(data) < size:
>>+ data += self.ep_in.read(size - len(data))
>>+ logging.log(logging.TRACE, "c2s: writing")
>>+ self._log_hexdump(data)
>>+ self.s.send(data)
>>+ logging.debug("c2s: forwarded %i bytes", size)
>>+ self.stats["c2s packets"] += 1
>>+ self.stats["c2s bytes"] += size
>>+
>>+ def s2c(self):
>>+ """forward a response from the TCP server to the USB client"""
>>+ logging.log(logging.TRACE, "s2c: reading")
>>+ data = self.s.recv(4)
>>+ size = struct.unpack("<I", data[:4])[0]
>>+ while len(data) < size:
>>+ data += self.s.recv(size - len(data))
>>+ logging.log(logging.TRACE, "s2c: writing")
>>+ self._log_hexdump(data)
>>+ while data:
>>+ written = self.ep_out.write(data)
>>+ assert written > 0
>>+ data = data[written:]
>>+ if size % self.ep_out.wMaxPacketSize == 0:
>>+ logging.log(logging.TRACE, "sending zero length packet")
>>+ self.ep_out.write(b"")
>>+ logging.debug("s2c: forwarded %i bytes", size)
>>+ self.stats["s2c packets"] += 1
>>+ self.stats["s2c bytes"] += size
>>+
>>+ def log_stats(self):
>>+ logging.info("statistics:")
>>+ for k, v in self.stats.items():
>>+ logging.info(f" {k+':':14s} {v}")
>>+
>>+ def log_stats_interval(self, interval=5):
>>+ if (time.monotonic() - self.stats_logged) < interval:
>>+ return
>>+
>>+ self.log_stats()
>>+ self.stats_logged = time.monotonic()
>>+
>>+
>>+def main():
>>+ parser = argparse.ArgumentParser(
>>+ description="Forward 9PFS requests from USB to TCP",
>>+ )
>>+
>>+ parser.add_argument(
>>+ "-s", "--server", type=str, default="127.0.0.1", help="server hostname"
>>+ )
>>+ parser.add_argument("-p", "--port", type=int, default=564, help="server port")
>>+ parser.add_argument("-v", "--verbose", action="count", default=0)
>>+
>>+ args = parser.parse_args()
>>+
>>+ logging.TRACE = logging.DEBUG - 5
>>+ logging.addLevelName(logging.TRACE, "TRACE")
>>+
>>+ if args.verbose >= 2:
>>+ level = logging.TRACE
>>+ elif args.verbose:
>>+ level = logging.DEBUG
>>+ else:
>>+ level = logging.INFO
>>+ logging.basicConfig(
>>+ level=level, format="%(asctime)-15s %(levelname)-8s %(message)s"
>>+ )
>>+
>>+ f = Forwarder(server=(args.server, args.port))
>>+
>>+ try:
>>+ while True:
>>+ f.c2s()
>>+ f.s2c()
>>+ f.log_stats_interval()
>>+ finally:
>>+ f.log_stats()
>>+
>>+
>>+if __name__ == "__main__":
>>+ main()
>>
>
>
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