Re: [PATCH v4 3/3] tools: usb: p9_fwd: add usb gadget packet forwarder script

Michael Grzeschik
2024-05-28T05:19:58Z

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On Fri, May 10, 2024 at 10:32:11AM +0200, Andrzej Pietrasiewicz wrote:
>Hi Michael,
>
>W dniu 10.05.2024 o 10:29, Andrzej Pietrasiewicz pisze:
>>Hi Michael,
>>
>>W dniu 30.04.2024 o 01:33, 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@pengutronix.de>
>>>
>>>---
>>>v3 -> v4: -
>>>v2 -> v3: -
>>>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 10cf79dc287f8..2467f1ea4a150 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 <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
>>>+
>>>+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.
>>>+
>>>+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)
>>
>>Is this idProduct an assigned number? I can't find it in
>>http://www.linux-usb.org/usb.ids. The "9" is obviously a pun on 9pfs,
>>a nice trick and it would make sense.
>>
>>However, given composition with configfs there's no guarantee that 9pfs will be
>>the only USB gadget function present, and so it is not quite clear that Linux
>>Foundation's vendor and product ids are always appropriate. What's more, when
>>you are not going to the market with products you can use whatever ids you
>>please for your own use.
>>
>>Given the above, I'd love these two (idVendor and idProduct) to be commandline
>>parameters of this script. My user story: whenever I created a gadget with
>>configfs it had different ids than the above and this script wouldn't work.
>
>And actually it is perfectly possible to have more than one USB device with
>_the same_ vendor and product ids connected. How would this script behave if
>that's the case?

I updated the script in v5 to support the subcommand "list" to show all
available devices and their usb path. Together with the configurable
option to select the vid/pid it is now possibleto address the exact
device you want to forward.

https://lore.kernel.org/all/20240116-ml-topic-u9p-v5-0-5ed0abd53ef5@pengutronix.dej/

Regards,
Michael

>>>+        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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