Oliver Hartkopp 7093c3b831 can: fix unique skb identifier regression under RPS ... Commit d4fb6514ff ("can: use skb hash instead of private variable in headroom") moved the per-skb unique identifier used for raw_rcv() duplicate detection into skb->hash. With RPS enabled, get_rps_cpu() calls skb_get_hash() before the frame reaches the CAN subsystem. Since CAN skbs have no L3/L4 headers, the flow dissector assigns every CAN frame the same non-zero software hash. can_set_skb_uid() only generated a new identifier when skb->hash was 0, so it kept this constant hash. When the SLAB allocator later reused the same skb address, raw_rcv() mistook the next legitimate frame for a duplicate and dropped it. Fix this by storing the CAN UID in the CAN skb extension (struct can_skb_ext::can_skb_uid) instead of skb->hash, decoupling it from any hash the network stack may compute. can_set_skb_uid() keeps its "assign only if unset" behaviour, which preserves UIDs set before transmission (e.g. by isotp to identify echo frames) across the local loopback path. Frames whose extension is shared with another clone (e.g. via tc mirred or netem duplicate) are given a private extension copy before the UID is assigned, so that independently received skb clones from real CAN interfaces (can_skb_uid = 0) don't end up with the same UID. The limitation that tc mirred/netem skb duplicates might be dropped in raw_rcv for looped back isotp echo frame skbs is accepted. There is no valid use-case for tc mirred or netem together with isotp which is not capable to operate on different CAN interfaces simultaneously. For routing and modifying CAN frames together with isotp use can-gw. can-gw and vxcan additionally clear the UID of forwarded/duplicated frames so each newly routed frame gets its own unique identifier. Fixes: d4fb6514ff ("can: use skb hash instead of private variable in headroom") Reported-by: Joerg Willmann <joe@clnt.de> Closes: https://lore.kernel.org/linux-can/2859AD3D-C805-41A0-9036-C5E8EE152419@clnt.de/ Cc: stable@vger.kernel.org Tested-by: Oliver Hartkopp <socketcan@hartkopp.net> Tested-by: Joerg Willmann <joe@clnt.de> Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net> Link: https://patch.msgid.link/20261001115724.27192-1-socketcan@hartkopp.net Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>		2026-10-01 17:05:03 +02:00
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j1939	can: j1939: transport: j1939_session_fresh_new(): initialize receive buffer	2026-07-29 10:15:33 +02:00
af_can.c	can: fix unique skb identifier regression under RPS	2026-10-01 17:05:03 +02:00
af_can.h	can: statistics: add missing atomic access in hot path	2026-03-19 14:53:19 +01:00
bcm.c	can: bcm: track a single source interface for ANYDEV timeout/throttle ops	2026-07-16 10:02:20 +02:00
gw.c	can: fix unique skb identifier regression under RPS	2026-10-01 17:05:03 +02:00
isotp.c	can: fix unique skb identifier regression under RPS	2026-10-01 17:05:03 +02:00
Kconfig	can: add CAN skb extension infrastructure	2026-02-05 11:58:39 +01:00
Makefile	can: add ISO 15765-2:2016 transport protocol	2020-10-07 23:18:33 +02:00
proc.c	can: statistics: add missing atomic access in hot path	2026-03-19 14:53:19 +01:00
raw.c	can: fix unique skb identifier regression under RPS	2026-10-01 17:05:03 +02:00