net: usb: ax88179_178a: fix rx frame length for non-last packets

Commit 4ce62d5b2f7a ("net: usb: ax88179_178a: stop lying about
skb->truesize") replaced skb_clone() with a copy into a new skb for
every packet of a bulk-in transfer except the last one. The copy skips
the 2-byte IP alignment pseudo header but still copies pkt_len bytes,
and pkt_len includes that header. Each of these frames is therefore
delivered with two extra trailing bytes: the 0xeeee pseudo header of
the next slot when the frame ends on an 8-byte boundary, or slot
padding otherwise. The last packet is still trimmed to pkt_len - 2.

IPv4 and IPv6 trim the extra bytes, so most traffic is unaffected.
Anything that relies on the frame length is not. MACsec takes the ICV
from the last 16 bytes and drops every such frame as InPktsNotValid. In
our setup that was 0.2-1.2% of received MACsec frames, depending on how
many frames shared a transfer, including service discovery multicast.

Allocate and copy pkt_len - 2 bytes, like the last-packet path.

Fixes: 4ce62d5b2f7a ("net: usb: ax88179_178a: stop lying about skb->truesize")
Cc: stable@vger.kernel.org
Signed-off-by: Fredrik Nyberg <fredrik.nyberg@volvocars.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20261002-ax88179-rx-len-v1-1-f01a2a295079@volvocars.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions