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>

1 files changed, 243 insertions, 0 deletions

diff --git a/tools/usb/p9_fwd.py b/tools/usb/p9_fwd.py
new file mode 100755
index 000000000000..12c76cbb046b
--- /dev/null
+++ b/tools/usb/p9_fwd.py
@@ -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()