diff options
Diffstat (limited to 'net')
| -rw-r--r-- | net/can/gw.c | 56 |
1 files changed, 40 insertions, 16 deletions
diff --git a/net/can/gw.c b/net/can/gw.c index 37a3efb..4216a80 100644 --- a/net/can/gw.c +++ b/net/can/gw.c @@ -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); |
