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 <[e-mail]>
Signed-off-by: Marc Kleine-Budde <[e-mail]>

Documentation/networking/can.txt

···
       4.1.3 RAW socket option CAN_RAW_LOOPBACK
       4.1.4 RAW socket option CAN_RAW_RECV_OWN_MSGS
       4.1.5 RAW socket option CAN_RAW_FD_FRAMES
-      4.1.6 RAW socket returned message flags
+      4.1.6 RAW socket option CAN_RAW_JOIN_FILTERS
+      4.1.7 RAW socket returned message flags
     4.2 Broadcast Manager protocol sockets (SOCK_DGRAM)
       4.2.1 Broadcast Manager operations
       4.2.2 Broadcast Manager message flags
···
   CAN FD frames by checking if the device maximum transfer unit is CANFD_MTU.
   The CAN device MTU can be retrieved e.g. with a SIOCGIFMTU ioctl() syscall.
 
-  4.1.6 RAW socket returned message flags
+  4.1.6 RAW socket option CAN_RAW_JOIN_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 (see 4.1.1).
+
+  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.
+
+  4.1.7 RAW socket returned message flags
 
   When using recvmsg() call, the msg->msg_flags may contain following flags:
 

include/uapi/linux/can/raw.h

···
 	CAN_RAW_LOOPBACK,	/* local loopback (default:on)       */
 	CAN_RAW_RECV_OWN_MSGS,	/* receive my own msgs (default:off) */
 	CAN_RAW_FD_FRAMES,	/* allow CAN FD frames (default:off) */
+	CAN_RAW_JOIN_FILTERS,	/* all filters must match to trigger */
 };
 
 #endif /* !_UAPI_CAN_RAW_H */

net/can/raw.c

···
 struct uniqframe {
 	ktime_t tstamp;
 	const struct sk_buff *skb;
+	unsigned int join_rx_count;
 };
 
 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) */
···
 	/* 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 */
···
 	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);
···
 
 		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;
 	}
···
 		if (len > sizeof(int))
 			len = sizeof(int);
 		val = &ro->fd_frames;
+		break;
+
+	case CAN_RAW_JOIN_FILTERS:
+		if (len > sizeof(int))
+			len = sizeof(int);
+		val = &ro->join_filters;
 		break;
 
 	default: