can: introduce new raw socket option to join the given CAN filters

The CAN_RAW socket can set multiple CAN identifier specific filters that lead
to multiple filters in the af_can.c filter processing. These filters are
indenpendent from each other which leads to logical OR'ed filters when applied.

This socket option joines the given CAN filters in the way that only CAN frames
are passed to user space that matched *all* given CAN filters. The semantic for
the applied filters is therefore changed to a logical AND.

This is useful especially when the filterset is a combination of filters where
the CAN_INV_FILTER flag is set in order to notch single CAN IDs or CAN ID
ranges from the incoming traffic.

As the raw_rcv() function is executed from NET_RX softirq the introduced
variables are implemented as per-CPU variables to avoid extensive locking at
CAN frame reception time.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

1 files changed, 30 insertions, 1 deletions

diff --git a/net/can/raw.c b/net/can/raw.c
index 0c8d537b59b8..31b9748cbb4e 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -77,6 +77,7 @@ MODULE_ALIAS("can-proto-1");
 struct uniqframe {
         ktime_t tstamp;
         const struct sk_buff *skb;
+        unsigned int join_rx_count;
 };
 
 struct raw_sock {
@@ -87,6 +88,7 @@ struct raw_sock {
         int loopback;
         int recv_own_msgs;
         int fd_frames;
+        int join_filters;
         int count;                 /* number of active filters */
         struct can_filter dfilter; /* default/single filter */
         struct can_filter *filter; /* pointer to filter(s) */
@@ -132,10 +134,21 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
         /* eliminate multiple filter matches for the same skb */
         if (this_cpu_ptr(ro->uniq)->skb == oskb &&
             ktime_equal(this_cpu_ptr(ro->uniq)->tstamp, oskb->tstamp)) {
-                return;
+                if (ro->join_filters) {
+                        this_cpu_inc(ro->uniq->join_rx_count);
+                        /* drop frame until all enabled filters matched */
+                        if (this_cpu_ptr(ro->uniq)->join_rx_count < ro->count)
+                                return;
+                } else {
+                        return;
+                }
         } else {
                 this_cpu_ptr(ro->uniq)->skb = oskb;
                 this_cpu_ptr(ro->uniq)->tstamp = oskb->tstamp;
+                this_cpu_ptr(ro->uniq)->join_rx_count = 1;
+                /* drop first frame to check all enabled filters? */
+                if (ro->join_filters && ro->count > 1)
+                        return;
         }
 
         /* clone the given skb to be able to enqueue it into the rcv queue */
@@ -311,6 +324,7 @@ static int raw_init(struct sock *sk)
         ro->loopback         = 1;
         ro->recv_own_msgs    = 0;
         ro->fd_frames        = 0;
+        ro->join_filters     = 0;
 
         /* alloc_percpu provides zero'ed memory */
         ro->uniq = alloc_percpu(struct uniqframe);
@@ -604,6 +618,15 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 
                 break;
 
+        case CAN_RAW_JOIN_FILTERS:
+                if (optlen != sizeof(ro->join_filters))
+                        return -EINVAL;
+
+                if (copy_from_user(&ro->join_filters, optval, optlen))
+                        return -EFAULT;
+
+                break;
+
         default:
                 return -ENOPROTOOPT;
         }
@@ -668,6 +691,12 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
                 val = &ro->fd_frames;
                 break;
 
+        case CAN_RAW_JOIN_FILTERS:
+                if (len > sizeof(int))
+                        len = sizeof(int);
+                val = &ro->join_filters;
+                break;
+
         default:
                 return -ENOPROTOOPT;
         }