1

tools: usb: p9_fwd: add usb gadget packet forwarder script

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: Jan Luebbe <jlu@pengutronix.de>
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Tested-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Link: https://lore.kernel.org/r/20240116-ml-topic-u9p-v12-3-9a27de5160e0@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Michael Grzeschik 2024-09-01 21:11:18 +02:00 committed by Greg Kroah-Hartman
parent a3be076dc1
commit 673f0c3ffc
2 changed files with 284 additions and 0 deletions

View File

@ -67,6 +67,47 @@ To mount a 9p FS on a USB Host accessible via the gadget as root filesystem::
where <device> is the tag associated by the usb gadget transport.
It is defined by the configfs instance name.
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
Optionaly scan your bus if there are more then one usbg gadgets to find their path:
$ python $kernel_dir/tools/usb/p9_fwd.py list
Bus | Addr | Manufacturer | Product | ID | Path
--- | ---- | ---------------- | ---------------- | --------- | ----
2 | 67 | unknown | unknown | 1d6b:0109 | 2-1.1.2
2 | 68 | unknown | unknown | 1d6b:0109 | 2-1.1.3
Then start the python transport:
$ python $kernel_dir/tools/usb/p9_fwd.py --path 2-1.1.2 connect -p 9999
After that the gadget driver can be used as described above.
One use-case is to use it as an alternative to NFS root booting during
the development of embedded Linux devices.
Options
=======

243
tools/usb/p9_fwd.py Executable file
View File

@ -0,0 +1,243 @@
#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-2.0
import argparse
import errno
import logging
import socket
import struct
import time
import usb.core
import usb.util
def path_from_usb_dev(dev):
"""Takes a pyUSB device as argument and returns a string.
The string is a Path representation of the position of the USB device on the USB bus tree.
This path is used to find a USB device on the bus or all devices connected to a HUB.
The path is made up of the number of the USB controller followed be the ports of the HUB tree."""
if dev.port_numbers:
dev_path = ".".join(str(i) for i in dev.port_numbers)
return f"{dev.bus}-{dev_path}"
return ""
HEXDUMP_FILTER = "".join(chr(x).isprintable() and chr(x) or "." for x in range(128)) + "." * 128
class Forwarder:
@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, vid, pid, path):
self.stats = {
"c2s packets": 0,
"c2s bytes": 0,
"s2c packets": 0,
"s2c bytes": 0,
}
self.stats_logged = time.monotonic()
def find_filter(dev):
dev_path = path_from_usb_dev(dev)
if path is not None:
return dev_path == path
return True
dev = usb.core.find(idVendor=vid, idProduct=pid, custom_match=find_filter)
if dev is None:
raise ValueError("Device not found")
logging.info(f"found device: {dev.bus}/{dev.address} located at {path_from_usb_dev(dev)}")
# 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("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("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
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 try_get_usb_str(dev, name):
try:
with open(f"/sys/bus/usb/devices/{dev.bus}-{dev.address}/{name}") as f:
return f.read().strip()
except FileNotFoundError:
return None
def list_usb(args):
vid, pid = [int(x, 16) for x in args.id.split(":", 1)]
print("Bus | Addr | Manufacturer | Product | ID | Path")
print("--- | ---- | ---------------- | ---------------- | --------- | ----")
for dev in usb.core.find(find_all=True, idVendor=vid, idProduct=pid):
path = path_from_usb_dev(dev) or ""
manufacturer = try_get_usb_str(dev, "manufacturer") or "unknown"
product = try_get_usb_str(dev, "product") or "unknown"
print(
f"{dev.bus:3} | {dev.address:4} | {manufacturer:16} | {product:16} | {dev.idVendor:04x}:{dev.idProduct:04x} | {path:18}"
)
def connect(args):
vid, pid = [int(x, 16) for x in args.id.split(":", 1)]
f = Forwarder(server=(args.server, args.port), vid=vid, pid=pid, path=args.path)
try:
while True:
f.c2s()
f.s2c()
f.log_stats_interval()
finally:
f.log_stats()
def main():
parser = argparse.ArgumentParser(
description="Forward 9PFS requests from USB to TCP",
)
parser.add_argument("--id", type=str, default="1d6b:0109", help="vid:pid of target device")
parser.add_argument("--path", type=str, required=False, help="path of target device")
parser.add_argument("-v", "--verbose", action="count", default=0)
subparsers = parser.add_subparsers()
subparsers.required = True
subparsers.dest = "command"
parser_list = subparsers.add_parser("list", help="List all connected 9p gadgets")
parser_list.set_defaults(func=list_usb)
parser_connect = subparsers.add_parser(
"connect", help="Forward messages between the usb9pfs gadget and the 9p server"
)
parser_connect.set_defaults(func=connect)
connect_group = parser_connect.add_argument_group()
connect_group.required = True
parser_connect.add_argument("-s", "--server", type=str, default="127.0.0.1", help="server hostname")
parser_connect.add_argument("-p", "--port", type=int, default=564, help="server port")
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")
args.func(args)
if __name__ == "__main__":
main()