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| author | Foster Snowhill <forst@pen.gy> | 2025-01-26 00:54:09 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-02-17 10:05:16 +0100 |
| commit | 829a5645616f3cf60f15fc6cab9a5e033e5b8170 (patch) | |
| tree | def2e4f642f5a2c7c333f7b87fbc1294d431a452 | |
| parent | 5835bf66c50ac2b85ed28b282c2456c3516ef0a6 (diff) | |
| download | linux-829a5645616f3cf60f15fc6cab9a5e033e5b8170.tar.gz linux-829a5645616f3cf60f15fc6cab9a5e033e5b8170.tar.bz2 linux-829a5645616f3cf60f15fc6cab9a5e033e5b8170.zip | |
usbnet: ipheth: document scope of NCM implementation
commit be154b598fa54136e2be17d6dd13c8a8bc0078ce upstream.
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: Foster Snowhill <forst@pen.gy>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/net/usb/ipheth.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/net/usb/ipheth.c b/drivers/net/usb/ipheth.c index 5347cd7e295b..a19789b57190 100644 --- a/drivers/net/usb/ipheth.c +++ b/drivers/net/usb/ipheth.c @@ -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; |