[patch 08/22] can: Fix CAN_(EFF|RTR)_FLAG handling in can_filter

Greg KH
2008-12-17T00:13:31Z

[-- Attachment #1: can-fix-can__flag-handling-in-can_filter.patch --]
[-- Type: text/plain, Size: 5397 bytes --]

2.6.27-stable review patch. If anyone has any objections, please let us know.

------------------

From: Oliver Hartkopp <oliver@hartkopp.net>

commit d253eee20195b25e298bf162a6e72f14bf4803e5 upstream.

Due to a wrong safety check in af_can.c it was not possible to filter
for SFF frames with a specific CAN identifier without getting the
same selected CAN identifier from a received EFF frame also.

This fix has a minimum (but user visible) impact on the CAN filter
API and therefore the CAN version is set to a new date.

Indeed the 'old' API is still working as-is. But when now setting
CAN_(EFF|RTR)_FLAG in can_filter.can_mask you might get less traffic
than before - but still the stuff that you expected to get for your
defined filter ...

Thanks to Kurt Van Dijck for pointing at this issue and for the review.

Signed-off-by: Oliver Hartkopp <oliver@hartkopp.net>
Acked-by: Kurt Van Dijck <kurt.van.dijck@eia.be>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
include/linux/can/core.h | 2 -
net/can/af_can.c | 63 +++++++++++++++++++++++++++++++++++------------
net/can/bcm.c | 7 ++---
3 files changed, 53 insertions(+), 19 deletions(-)

--- a/include/linux/can/core.h
+++ b/include/linux/can/core.h
@@ -19,7 +19,7 @@
#include <linux/skbuff.h>
#include <linux/netdevice.h>

-#define CAN_VERSION "20071116"
+#define CAN_VERSION "20081130"

/* increment this number each time you change some user-space interface */
#define CAN_ABI_VERSION "8"
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -319,23 +319,52 @@ static struct dev_rcv_lists *find_dev_rc
return n ? d : NULL;
}

+/**
+ * find_rcv_list - determine optimal filterlist inside device filter struct
+ * @can_id: pointer to CAN identifier of a given can_filter
+ * @mask: pointer to CAN mask of a given can_filter
+ * @d: pointer to the device filter struct
+ *
+ * Description:
+ * Returns the optimal filterlist to reduce the filter handling in the
+ * receive path. This function is called by service functions that need
+ * to register or unregister a can_filter in the filter lists.
+ *
+ * A filter matches in general, when
+ *
+ * <received_can_id> & mask == can_id & mask
+ *
+ * so every bit set in the mask (even CAN_EFF_FLAG, CAN_RTR_FLAG) describe
+ * relevant bits for the filter.
+ *
+ * The filter can be inverted (CAN_INV_FILTER bit set in can_id) or it can
+ * filter for error frames (CAN_ERR_FLAG bit set in mask). For error frames
+ * there is a special filterlist and a special rx path filter handling.
+ *
+ * Return:
+ * Pointer to optimal filterlist for the given can_id/mask pair.
+ * Constistency checked mask.
+ * Reduced can_id to have a preprocessed filter compare value.
+ */
static struct hlist_head *find_rcv_list(canid_t *can_id, canid_t *mask,
struct dev_rcv_lists *d)
{
canid_t inv = *can_id & CAN_INV_FILTER; /* save flag before masking */

- /* filter error frames */
+ /* filter for error frames in extra filterlist */
if (*mask & CAN_ERR_FLAG) {
- /* clear CAN_ERR_FLAG in list entry */
+ /* clear CAN_ERR_FLAG in filter entry */
*mask &= CAN_ERR_MASK;
return &d->rx[RX_ERR];
}

- /* ensure valid values in can_mask */
- if (*mask & CAN_EFF_FLAG)
- *mask &= (CAN_EFF_MASK | CAN_EFF_FLAG | CAN_RTR_FLAG);
- else
- *mask &= (CAN_SFF_MASK | CAN_RTR_FLAG);
+ /* with cleared CAN_ERR_FLAG we have a simple mask/value filterpair */
+
+#define CAN_EFF_RTR_FLAGS (CAN_EFF_FLAG | CAN_RTR_FLAG)
+
+ /* ensure valid values in can_mask for 'SFF only' frame filtering */
+ if ((*mask & CAN_EFF_FLAG) && !(*can_id & CAN_EFF_FLAG))
+ *mask &= (CAN_SFF_MASK | CAN_EFF_RTR_FLAGS);

/* reduce condition testing at receive time */
*can_id &= *mask;
@@ -348,15 +377,19 @@ static struct hlist_head *find_rcv_list(
if (!(*mask))
return &d->rx[RX_ALL];

- /* use extra filterset for the subscription of exactly *ONE* can_id */
- if (*can_id & CAN_EFF_FLAG) {
- if (*mask == (CAN_EFF_MASK | CAN_EFF_FLAG)) {
- /* RFC: a use-case for hash-tables in the future? */
- return &d->rx[RX_EFF];
+ /* extra filterlists for the subscription of a single non-RTR can_id */
+ if (((*mask & CAN_EFF_RTR_FLAGS) == CAN_EFF_RTR_FLAGS)
+ && !(*can_id & CAN_RTR_FLAG)) {
+
+ if (*can_id & CAN_EFF_FLAG) {
+ if (*mask == (CAN_EFF_MASK | CAN_EFF_RTR_FLAGS)) {
+ /* RFC: a future use-case for hash-tables? */
+ return &d->rx[RX_EFF];
+ }
+ } else {
+ if (*mask == (CAN_SFF_MASK | CAN_EFF_RTR_FLAGS))
+ return &d->rx_sff[*can_id];
}
- } else {
- if (*mask == CAN_SFF_MASK)
- return &d->rx_sff[*can_id];
}

/* default: filter via can_id/can_mask */
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -64,10 +64,11 @@
#define BCM_CAN_DLC_MASK 0x0F /* clean private flags in can_dlc by masking */

/* get best masking value for can_rx_register() for a given single can_id */
-#define REGMASK(id) ((id & CAN_RTR_FLAG) | ((id & CAN_EFF_FLAG) ? \
- (CAN_EFF_MASK | CAN_EFF_FLAG) : CAN_SFF_MASK))
+#define REGMASK(id) ((id & CAN_EFF_FLAG) ? \
+ (CAN_EFF_MASK | CAN_EFF_FLAG | CAN_RTR_FLAG) : \
+ (CAN_SFF_MASK | CAN_EFF_FLAG | CAN_RTR_FLAG))

-#define CAN_BCM_VERSION "20080415"
+#define CAN_BCM_VERSION CAN_VERSION
static __initdata const char banner[] = KERN_INFO
"can: broadcast manager protocol (rev " CAN_BCM_VERSION ")\n";