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Commit be286baf authored by Oliver Hartkopp's avatar Oliver Hartkopp Committed by Marc Kleine-Budde
Browse files

can: gw: add a variable limit for CAN frame routings 



To prevent a possible misconfiguration (e.g. circular CAN frame routings)
limit the number of routings of a single CAN frame to a small variable value.

The limit can be specified by the module parameter 'max_hops' (1..6).
The default value is 1 (one hop), according to the original can-gw behaviour.

Signed-off-by: default avatarOliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
parent d904d3ed

net/can/gw.c

+40 −16
Original line number Diff line number Diff line
@@ -42,6 +42,7 @@ 
#include <linux/module.h>

#include <linux/init.h>

#include <linux/types.h>

#include <linux/kernel.h>

#include <linux/list.h>

#include <linux/spinlock.h>

#include <linux/rcupdate.h>
@@ -58,14 +59,25 @@ 
#include <net/net_namespace.h>

#include <net/sock.h>



#define CAN_GW_VERSION "20101209"

static __initconst const char banner[] =

	KERN_INFO "can: netlink gateway (rev " CAN_GW_VERSION ")\n";

#define CAN_GW_VERSION "20130117"

#define CAN_GW_NAME "can-gw"



MODULE_DESCRIPTION("PF_CAN netlink gateway");

MODULE_LICENSE("Dual BSD/GPL");

MODULE_AUTHOR("Oliver Hartkopp <oliver.hartkopp@volkswagen.de>");

MODULE_ALIAS("can-gw");

MODULE_ALIAS(CAN_GW_NAME);



#define CGW_MIN_HOPS 1

#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, S_IRUGO);

MODULE_PARM_DESC(max_hops,

		 "maximum " CAN_GW_NAME " routing hops for CAN frames "

		 "(valid values: " __stringify(CGW_MIN_HOPS) "-"

		 __stringify(CGW_MAX_HOPS) " hops, "

		 "default: " __stringify(CGW_DEFAULT_HOPS) ")");



static HLIST_HEAD(cgw_list);

static struct notifier_block notifier;
@@ -339,8 +351,23 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data) 
	struct sk_buff *nskb;

	int modidx = 0;



	/* do not handle already routed frames - see comment below */

	if (skb_mac_header_was_set(skb))

	/*

	 * 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/unsued 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)

		return;



	if (!(gwj->dst.dev->flags & IFF_UP)) {
@@ -371,15 +398,8 @@ static void can_can_gw_rcv(struct sk_buff *skb, void *data) 
		return;

	}



	/*

	 * Mark routed frames by setting some mac header length which is

	 * not relevant for the CAN frames located in the skb->data section.

	 *

	 * As dev->header_ops is not set in CAN netdevices no one is ever

	 * accessing the various header offsets in the CAN skbuffs anyway.

	 * E.g. using the packet socket to read CAN frames is still working.

	 */

	skb_set_mac_header(nskb, 8);

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

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

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



	/* pointer to modifiable CAN frame */
@@ -903,7 +923,11 @@ static int cgw_remove_job(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg) 


static __init int cgw_module_init(void)

{

	printk(banner);

	/* sanitize given module parameter */

	max_hops = clamp_t(unsigned int, max_hops, CGW_MIN_HOPS, CGW_MAX_HOPS);



	pr_info("can: netlink gateway (rev " CAN_GW_VERSION ") max_hops=%d\n",

		max_hops);



	cgw_cache = kmem_cache_create("can_gw", sizeof(struct cgw_job),

				      0, 0, NULL);