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

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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: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Oliver Hartkopp 2013-01-17 18:43:44 +01:00 committed by Marc Kleine-Budde
parent d904d3edcb
commit be286bafe1
1 changed files with 40 additions and 16 deletions
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56
net/can/gw.c
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@ -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);