Commit be154b59 authored by Foster Snowhill's avatar Foster Snowhill Committed by Paolo Abeni
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usbnet: ipheth: document scope of NCM implementation 



Clarify that the "NCM" implementation in `ipheth` is very limited, as
iOS devices aren't compatible with the CDC NCM specification in regular
tethering mode.

For a standards-compliant implementation, one shall turn to
the `cdc_ncm` module.

Cc: stable@vger.kernel.org # 6.5.x
Signed-off-by: default avatarFoster Snowhill <forst@pen.gy>
Reviewed-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent ee591f2b

drivers/net/usb/ipheth.c

+8 −0
Original line number Diff line number Diff line
@@ -218,6 +218,14 @@ static int ipheth_rcvbulk_callback_legacy(struct urb *urb) 
	return ipheth_consume_skb(buf, len, dev);

}



/* In "NCM mode", the iOS device encapsulates RX (phone->computer) traffic

 * in NCM Transfer Blocks (similarly to CDC NCM). However, unlike reverse

 * tethering (handled by the `cdc_ncm` driver), regular tethering is not

 * compliant with the CDC NCM spec, as the device is missing the necessary

 * descriptors, and TX (computer->phone) traffic is not encapsulated

 * at all. Thus `ipheth` implements a very limited subset of the spec with

 * the sole purpose of parsing RX URBs.

 */

static int ipheth_rcvbulk_callback_ncm(struct urb *urb)

{

	struct usb_cdc_ncm_nth16 *ncmh;