net: mctp: usblib: Implement receive-side packet spanning

Using the existing prepare/complete API, we can persist the rx skb
across receives to implement v1.1 packet spanning.

Alter the packet-extraction loop to allow truncated packets, returning
early with the skb persisted for the next IN urb completion. When we see
we have a complete packet, netif_rx() that. If the packet boundary
aligns with the urb completion, we can netif_rx() the whole thing.

Those intermediate packets are cloned from the original
(large-transfer-data) skb. Unlike existing behaviour, if the clone
fails, we drop just that clone, instead of the existing transfer skb.
This allows us to process the rest of the skb data, and any continuation
of the span into the next transfer.

One subtle change: the mctp_usblib_rx() helper now handles skbs with the
full transport header, so we shift the skb_pull() for the header data to
the helper, before doing the rx_bytes stats update.

We still need to handle non-spanning mode, so error out on
truncated-packet cases there.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://patch.msgid.link/20260724-dev-mctp-usb-1-1-v5-8-e66bbba0dbdc@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions