can: gw: add a variable limit for CAN frame routings (be286baf) · Commits · 戴 / test

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);

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