diff options
| author | Oliver Hartkopp <socketcan@hartkopp.net> | 2026-10-01 13:57:24 +0200 |
|---|---|---|
| committer | Marc Kleine-Budde <mkl@pengutronix.de> | 2026-10-01 17:05:03 +0200 |
| commit | 7093c3b8314a4ef7405c4066a2521398c455efe7 (patch) | |
| tree | f7502c5160a5b442258cd8b5179fef6edfde0fc5 /include/linux | |
| parent | 0a04c0cb8606ff88399489d03ef255afe90d0d5f (diff) | |
can: fix unique skb identifier regression under RPS
Commit d4fb6514ff8e ("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: d4fb6514ff8e ("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>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/can/core.h | 3 | ||||
| -rw-r--r-- | include/linux/can/skb.h | 4 |
2 files changed, 5 insertions, 2 deletions
diff --git a/include/linux/can/core.h b/include/linux/can/core.h index 3287232e3cad..2de74c2b78b6 100644 --- a/include/linux/can/core.h +++ b/include/linux/can/core.h @@ -17,6 +17,7 @@ #include <linux/can.h> #include <linux/skbuff.h> #include <linux/netdevice.h> +#include <net/can.h> #define DNAME(dev) ((dev) ? (dev)->name : "any") @@ -58,7 +59,7 @@ extern void can_rx_unregister(struct net *net, struct net_device *dev, void *data); extern int can_send(struct sk_buff *skb, int loop); -void can_set_skb_uid(struct sk_buff *skb); +void can_set_skb_uid(struct can_skb_ext *csx); void can_sock_destruct(struct sock *sk); #endif /* !_CAN_CORE_H */ diff --git a/include/linux/can/skb.h b/include/linux/can/skb.h index a70a02967071..5d27843862fc 100644 --- a/include/linux/can/skb.h +++ b/include/linux/can/skb.h @@ -43,8 +43,10 @@ static inline struct can_skb_ext *can_skb_ext_add(struct sk_buff *skb) struct can_skb_ext *csx = skb_ext_add(skb, SKB_EXT_CAN); /* skb_ext_add() returns uninitialized space */ - if (csx) + if (csx) { csx->can_gw_hops = 0; + csx->can_skb_uid = 0; + } return csx; } |