Commit 3ffecc14 authored by Oliver Hartkopp's avatar Oliver Hartkopp Committed by Paolo Abeni
Browse files

can: gw: use can_gw_hops instead of sk_buff::csum_start 



As CAN skbs don't use IP checksums the skb->csum_start variable was used to
store the can-gw CAN frame time-to-live counter together with
skb->ip_summed set to CHECKSUM_UNNECESSARY.

Remove the 'hack' using the skb->csum_start variable and move the content
to can_skb_ext::can_gw_hops of the CAN skb extensions.

The module parameter 'max_hops' has been reduced to a single byte to fit
can_skb_ext::can_gw_hops as the maximum value to be stored is 6.

Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: default avatarOliver Hartkopp <socketcan@hartkopp.net>
Link: https://patch.msgid.link/20260201-can_skb_ext-v8-6-3635d790fe8b@hartkopp.net


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 9f10374b

drivers/net/can/vxcan.c

+1 −1
Original line number Diff line number Diff line
@@ -77,7 +77,7 @@ static netdev_tx_t vxcan_xmit(struct sk_buff *oskb, struct net_device *dev) 
	}



	/* reset CAN GW hop counter */

	skb->csum_start = 0;

	csx->can_gw_hops = 0;

	skb->pkt_type   = PACKET_BROADCAST;

	skb->dev        = peer;

	skb->ip_summed  = CHECKSUM_UNNECESSARY;

net/can/gw.c

+6 −17
Original line number Diff line number Diff line
@@ -71,8 +71,8 @@ MODULE_ALIAS(CAN_GW_NAME); 
#define CGW_MAX_HOPS 6

#define CGW_DEFAULT_HOPS 1



static unsigned int max_hops __read_mostly = CGW_DEFAULT_HOPS;

module_param(max_hops, uint, 0444);

static unsigned char max_hops __read_mostly = CGW_DEFAULT_HOPS;

module_param(max_hops, byte, 0444);

MODULE_PARM_DESC(max_hops,

		 "maximum " CAN_GW_NAME " routing hops for CAN frames "

		 "(valid values: " __stringify(CGW_MIN_HOPS) "-"
@@ -480,19 +480,8 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data) 
	/* Do not handle CAN frames routed more than 'max_hops' times.

	 * In general we should never catch this delimiter which is intended

	 * to cover a misconfiguration protection (e.g. circular CAN routes).

	 *

	 * The Controller Area Network controllers only accept CAN frames with

	 * correct CRCs - which are not visible in the controller registers.

	 * According to skbuff.h documentation the csum_start element for IP

	 * checksums is undefined/unused when ip_summed == CHECKSUM_UNNECESSARY.

	 * Only CAN skbs can be processed here which already have this property.

	 */



#define cgw_hops(skb) ((skb)->csum_start)



	BUG_ON(skb->ip_summed != CHECKSUM_UNNECESSARY);



	if (cgw_hops(skb) >= max_hops) {

	if (csx->can_gw_hops >= max_hops) {

		/* indicate deleted frames due to misconfiguration */

		gwj->deleted_frames++;

		return;
@@ -536,11 +525,11 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data) 
	}



	/* put the incremented hop counter in the cloned skb */

	cgw_hops(nskb) = cgw_hops(skb) + 1;

	ncsx->can_gw_hops = csx->can_gw_hops + 1;



	/* first processing of this CAN frame -> adjust to private hop limit */

	if (gwj->limit_hops && cgw_hops(nskb) == 1)

		cgw_hops(nskb) = max_hops - gwj->limit_hops + 1;

	if (gwj->limit_hops && ncsx->can_gw_hops == 1)

		ncsx->can_gw_hops = max_hops - gwj->limit_hops + 1;



	nskb->dev = gwj->dst.dev;