linux-kernel - [PATCH] CDC-NCM: add support for Apple's private interface

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Message-ID: <20240607074117.31322-1-oleavr@frida.re>
Date: Fri,  7 Jun 2024 09:40:17 +0200
From: Ole André Vadla Ravnås <oleavr@...da.re>
To: linux-usb@...r.kernel.org
Cc: oleavr@...da.re,
	Håvard Sørbø <havard@...rbo.no>,
	Oliver Neukum <oliver@...kum.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] CDC-NCM: add support for Apple's private interface

Available on iOS/iPadOS >= 17, where this new interface is used by
developer tools using the new RemoteXPC protocol.

This private interface lacks a status endpoint, presumably because there
isn't a physical cable that can be unplugged, nor any speed changes to
be notified about.

Note that NCM interfaces are not exposed until a mode switch is
requested, which macOS does automatically.

The mode switch can be performed like this:

        uint8_t status;
        libusb_control_transfer(device_handle,
                LIBUSB_RECIPIENT_DEVICE | LIBUSB_REQUEST_TYPE_VENDOR |
                LIBUSB_ENDPOINT_IN,
                82, /* bRequest */
                0,  /* wValue   */
                3,  /* wIndex   */
                &status,
                sizeof(status),
                0);

Newer versions of usbmuxd do this automatically.

Co-developed-by: Håvard Sørbø <havard@...rbo.no>
Signed-off-by: Håvard Sørbø <havard@...rbo.no>
Signed-off-by: Ole André Vadla Ravnås <oleavr@...da.re>
---
 drivers/net/usb/cdc_ncm.c | 47 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index bf76ecccc2e6..d5c47a2a62dc 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -933,7 +933,8 @@ int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_
 
 	cdc_ncm_find_endpoints(dev, ctx->data);
 	cdc_ncm_find_endpoints(dev, ctx->control);
-	if (!dev->in || !dev->out || !dev->status) {
+	if (!dev->in || !dev->out ||
+	    (!dev->status && dev->driver_info->flags & FLAG_LINK_INTR)) {
 		dev_dbg(&intf->dev, "failed to collect endpoints\n");
 		goto error2;
 	}
@@ -1925,6 +1926,34 @@ static const struct driver_info cdc_ncm_zlp_info = {
 	.set_rx_mode = usbnet_cdc_update_filter,
 };
 
+/* Same as cdc_ncm_info, but with FLAG_SEND_ZLP */
+static const struct driver_info apple_tethering_interface_info = {
+	.description = "CDC NCM (Apple Tethering)",
+	.flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT | FLAG_MULTI_PACKET
+			| FLAG_LINK_INTR | FLAG_ETHER | FLAG_SEND_ZLP,
+	.bind = cdc_ncm_bind,
+	.unbind = cdc_ncm_unbind,
+	.manage_power = usbnet_manage_power,
+	.status = cdc_ncm_status,
+	.rx_fixup = cdc_ncm_rx_fixup,
+	.tx_fixup = cdc_ncm_tx_fixup,
+	.set_rx_mode = usbnet_cdc_update_filter,
+};
+
+/* Same as apple_tethering_interface_info, but without FLAG_LINK_INTR */
+static const struct driver_info apple_private_interface_info = {
+	.description = "CDC NCM (Apple Private)",
+	.flags = FLAG_POINTTOPOINT | FLAG_NO_SETINT | FLAG_MULTI_PACKET
+			| FLAG_ETHER | FLAG_SEND_ZLP,
+	.bind = cdc_ncm_bind,
+	.unbind = cdc_ncm_unbind,
+	.manage_power = usbnet_manage_power,
+	.status = cdc_ncm_status,
+	.rx_fixup = cdc_ncm_rx_fixup,
+	.tx_fixup = cdc_ncm_tx_fixup,
+	.set_rx_mode = usbnet_cdc_update_filter,
+};
+
 /* Same as cdc_ncm_info, but with FLAG_WWAN */
 static const struct driver_info wwan_info = {
 	.description = "Mobile Broadband Network Device",
@@ -1954,6 +1983,22 @@ static const struct driver_info wwan_noarp_info = {
 };
 
 static const struct usb_device_id cdc_devs[] = {
+	/* iPhone */
+	{ USB_DEVICE_INTERFACE_NUMBER(0x05ac, 0x12a8, 2),
+		.driver_info = (unsigned long)&apple_tethering_interface_info,
+	},
+	{ USB_DEVICE_INTERFACE_NUMBER(0x05ac, 0x12a8, 4),
+		.driver_info = (unsigned long)&apple_private_interface_info,
+	},
+
+	/* iPad */
+	{ USB_DEVICE_INTERFACE_NUMBER(0x05ac, 0x12ab, 2),
+		.driver_info = (unsigned long)&apple_tethering_interface_info,
+	},
+	{ USB_DEVICE_INTERFACE_NUMBER(0x05ac, 0x12ab, 4),
+		.driver_info = (unsigned long)&apple_private_interface_info,
+	},
+
 	/* Ericsson MBM devices like F5521gw */
 	{ .match_flags = USB_DEVICE_ID_MATCH_INT_INFO
 		| USB_DEVICE_ID_MATCH_VENDOR,
-- 
2.45.2