Add a tweak to support USB with 0 class number in device descriptor

VHCI driver builds compatible id with USB class/subclass/protocol
numbers. So those numbers in the first interface descriptor are
delivered to VHCI if udev structure has zero class number.
Sadly, udev structure from linux does not have an interface descriptor.
So we should get interface class number via GET_DESCRIPTOR usb command.

USB stick can be shown as "Mass storage" in device manager
*but* it is not working correctly yet.

userspace/src/usbip/usbip_attach.c

@@ -21,6 +21,7 @@
 #include "usbip_common.h"
 #include "usbip_network.h"
 #include "usbip_vhci.h"
+#include "usbip_proto.h"
 #include "usbip_forward.h"
 
 static const char usbip_attach_usage_string[] =
@@ -33,6 +34,67 @@ void usbip_attach_usage(void)
 	printf("usage: %s", usbip_attach_usage_string);
 }
 
+/*
+ * Sadly, udev structure from linux does not have an interface descriptor.
+ * So we should get interface class number via GET_DESCRIPTOR usb command.
+ */
+static void
+supplement_udev(SOCKET sockfd, UINT32 devid, struct usbip_usb_device *udev)
+{
+	struct usbip_header	uhdr;
+	unsigned char	buf[18];
+	unsigned	alen;
+
+	memset(&uhdr, 0, sizeof(uhdr));
+
+	uhdr.base.command = htonl(USBIP_CMD_SUBMIT);
+	/* sufficient large enough seq used to avoid conflict with normal vhci operation */
+	uhdr.base.seqnum = htonl(0x7fffffff);
+	uhdr.base.direction = htonl(USBIP_DIR_IN);
+	uhdr.base.devid = htonl(devid);
+
+	uhdr.u.cmd_submit.transfer_buffer_length = htonl(18);
+	uhdr.u.cmd_submit.setup[0] = 0x80;	/* IN/control port */
+	uhdr.u.cmd_submit.setup[1] = 6;		/* GetDescriptor */
+	uhdr.u.cmd_submit.setup[6] = 18;	/* Length */
+	uhdr.u.cmd_submit.setup[3] = 2;		/* Configuration Descriptor */
+
+	if (usbip_net_send(sockfd, &uhdr, sizeof(uhdr)) < 0) {
+		err("get_desc: failed to send usbip header\n");
+		return;
+	}
+	if (usbip_net_recv(sockfd, &uhdr, sizeof(uhdr)) < 0) {
+		err("get_desc: failed to recv usbip header\n");
+		return;
+	}
+	if (uhdr.u.ret_submit.status != 0) {
+		err("get_desc: command submit error\n");
+		return;
+	}
+	alen = ntohl(uhdr.u.ret_submit.actual_length);
+	if (alen < 18) {
+		err("get_desc: too short response\n");
+		return;
+	}
+	if (usbip_net_recv(sockfd, buf, 18) < 0) {
+		err("get_desc: failed to recv usbip payload\n");
+		return;
+	}
+	udev->bDeviceClass = buf[14];
+	udev->bDeviceSubClass = buf[15];
+	udev->bDeviceProtocol = buf[16];
+}
+
+static void
+try_to_tweak_udev(SOCKET sockfd, struct usbip_usb_device *udev)
+{
+	if (udev->bDeviceClass != 0 && udev->bDeviceSubClass != 0 && udev->bDeviceProtocol == 0)
+		return;
+	if (udev->bNumConfigurations != 1)
+		return;
+	supplement_udev(sockfd, udev->busnum << 16 | udev->devnum, udev);
+}
+
 static int import_device(SOCKET sockfd, struct usbip_usb_device *udev, HANDLE *phdev)
 {
 	HANDLE hdev;
@@ -115,6 +177,13 @@ static int query_import_device(SOCKET sockfd, const char *busid, HANDLE *phdev)
 		return 1;
 	}
 
+	/* Many devices have 0 usb class number in a device descriptor.
+	 * 0 value means that class number is determined at interface level.
+	 * USB class, subclass and protocol numbers should be setup before importing.
+	 * Because windows vhci driver builds a device compatible id with those numbers.
+	 */
+	try_to_tweak_udev(sockfd, &reply.udev);
+
 	/* import a device */
 	return import_device(sockfd, &reply.udev, phdev);
 }