can: bcm: add recvmsg flags for own, local and remote traffic

CAN RAW sockets allow userspace to tell if a received CAN frame comes
from the same socket, another socket on the same host, or another host.
See commit 1e55659ce6dd ("can-raw: add msg_flags to distinguish local
traffic"). However, this feature is missing in CAN BCM sockets.

Add the same feature to CAN BCM sockets. When reading a received frame
(opcode RX_CHANGED) using recvmsg, two flags in msg->msg_flags may be
set following the previous convention (from CAN RAW), to distinguish
between 'own', 'local' and 'remote' CAN traffic.

Update the documentation to reflect this change.

Signed-off-by: Nicolas Maier <nicolas.maier.dev@gmail.com>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://lore.kernel.org/all/20240120081018.2319-1-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/Documentation/networking/can.rst b/Documentation/networking/can.rst
index d7e1ada905b2d3bc901e8537f2876d7b28090a08..62519d38c58badee6809a22e4e3ec7ec63d02f1a 100644 (file)
--- a/Documentation/networking/can.rst
+++ b/Documentation/networking/can.rst
@@ -444,6 +444,24 @@ definitions are specified for CAN specific MTUs in include/linux/can.h:
   #define CANFD_MTU (sizeof(struct canfd_frame)) == 72  => CAN FD frame
 
 
+Returned Message Flags
+----------------------
+
+When using the system call recvmsg(2) on a RAW or a BCM socket, the
+msg->msg_flags field may contain the following flags:
+
+MSG_DONTROUTE:
+       set when the received frame was created on the local host.
+
+MSG_CONFIRM:
+       set when the frame was sent via the socket it is received on.
+       This flag can be interpreted as a 'transmission confirmation' when the
+       CAN driver supports the echo of frames on driver level, see
+       :ref:`socketcan-local-loopback1` and :ref:`socketcan-local-loopback2`.
+       (Note: In order to receive such messages on a RAW socket,
+       CAN_RAW_RECV_OWN_MSGS must be set.)
+
+
 .. _socketcan-raw-sockets:
 
 RAW Protocol Sockets with can_filters (SOCK_RAW)
@@ -693,22 +711,6 @@ where the CAN_INV_FILTER flag is set in order to notch single CAN IDs or
 CAN ID ranges from the incoming traffic.
 
 
-RAW Socket Returned Message Flags
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-When using recvmsg() call, the msg->msg_flags may contain following flags:
-
-MSG_DONTROUTE:
-       set when the received frame was created on the local host.
-
-MSG_CONFIRM:
-       set when the frame was sent via the socket it is received on.
-       This flag can be interpreted as a 'transmission confirmation' when the
-       CAN driver supports the echo of frames on driver level, see
-       :ref:`socketcan-local-loopback1` and :ref:`socketcan-local-loopback2`.
-       In order to receive such messages, CAN_RAW_RECV_OWN_MSGS must be set.
-
-
 Broadcast Manager Protocol Sockets (SOCK_DGRAM)
 -----------------------------------------------
 

diff --git a/net/can/bcm.c b/net/can/bcm.c
index 9168114fc87f7b577d393fda08a80d7a9941122e..27d5fcf0eac9dd4737ff03a36737c2286a6c5882 100644 (file)
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -72,9 +72,11 @@
 #define BCM_TIMER_SEC_MAX (400 * 24 * 60 * 60)
 
 /* use of last_frames[index].flags */
+#define RX_LOCAL   0x10 /* frame was created on the local host */
+#define RX_OWN     0x20 /* frame was sent via the socket it was received on */
 #define RX_RECV    0x40 /* received data for this element */
 #define RX_THR     0x80 /* element not been sent due to throttle feature */
-#define BCM_CAN_FLAGS_MASK 0x3F /* to clean private flags after usage */
+#define BCM_CAN_FLAGS_MASK 0x0F /* to clean private flags after usage */
 
 /* get best masking value for can_rx_register() for a given single can_id */
 #define REGMASK(id) ((id & CAN_EFF_FLAG) ? \
@@ -138,6 +140,16 @@ static LIST_HEAD(bcm_notifier_list);
 static DEFINE_SPINLOCK(bcm_notifier_lock);
 static struct bcm_sock *bcm_busy_notifier;
 
+/* Return pointer to store the extra msg flags for bcm_recvmsg().
+ * We use the space of one unsigned int beyond the 'struct sockaddr_can'
+ * in skb->cb.
+ */
+static inline unsigned int *bcm_flags(struct sk_buff *skb)
+{
+       /* return pointer after struct sockaddr_can */
+       return (unsigned int *)(&((struct sockaddr_can *)skb->cb)[1]);
+}
+
 static inline struct bcm_sock *bcm_sk(const struct sock *sk)
 {
        return (struct bcm_sock *)sk;
@@ -325,6 +337,7 @@ static void bcm_send_to_user(struct bcm_op *op, struct bcm_msg_head *head,
        struct sock *sk = op->sk;
        unsigned int datalen = head->nframes * op->cfsiz;
        int err;
+       unsigned int *pflags;
 
        skb = alloc_skb(sizeof(*head) + datalen, gfp_any());
        if (!skb)
@@ -332,6 +345,14 @@ static void bcm_send_to_user(struct bcm_op *op, struct bcm_msg_head *head,
 
        skb_put_data(skb, head, sizeof(*head));
 
+       /* ensure space for sockaddr_can and msg flags */
+       sock_skb_cb_check_size(sizeof(struct sockaddr_can) +
+                              sizeof(unsigned int));
+
+       /* initialize msg flags */
+       pflags = bcm_flags(skb);
+       *pflags = 0;
+
        if (head->nframes) {
                /* CAN frames starting here */
                firstframe = (struct canfd_frame *)skb_tail_pointer(skb);
@@ -344,8 +365,14 @@ static void bcm_send_to_user(struct bcm_op *op, struct bcm_msg_head *head,
                 * relevant for updates that are generated by the
                 * BCM, where nframes is 1
                 */
-               if (head->nframes == 1)
+               if (head->nframes == 1) {
+                       if (firstframe->flags & RX_LOCAL)
+                               *pflags |= MSG_DONTROUTE;
+                       if (firstframe->flags & RX_OWN)
+                               *pflags |= MSG_CONFIRM;
+
                        firstframe->flags &= BCM_CAN_FLAGS_MASK;
+               }
        }
 
        if (has_timestamp) {
@@ -360,7 +387,6 @@ static void bcm_send_to_user(struct bcm_op *op, struct bcm_msg_head *head,
         *  containing the interface index.
         */
 
-       sock_skb_cb_check_size(sizeof(struct sockaddr_can));
        addr = (struct sockaddr_can *)skb->cb;
        memset(addr, 0, sizeof(*addr));
        addr->can_family  = AF_CAN;
@@ -444,7 +470,7 @@ static void bcm_rx_changed(struct bcm_op *op, struct canfd_frame *data)
                op->frames_filtered = op->frames_abs = 0;
 
        /* this element is not throttled anymore */
-       data->flags &= (BCM_CAN_FLAGS_MASK|RX_RECV);
+       data->flags &= ~RX_THR;
 
        memset(&head, 0, sizeof(head));
        head.opcode  = RX_CHANGED;
@@ -465,13 +491,17 @@ static void bcm_rx_changed(struct bcm_op *op, struct canfd_frame *data)
  */
 static void bcm_rx_update_and_send(struct bcm_op *op,
                                   struct canfd_frame *lastdata,
-                                  const struct canfd_frame *rxdata)
+                                  const struct canfd_frame *rxdata,
+                                  unsigned char traffic_flags)
 {
        memcpy(lastdata, rxdata, op->cfsiz);
 
        /* mark as used and throttled by default */
        lastdata->flags |= (RX_RECV|RX_THR);
 
+       /* add own/local/remote traffic flags */
+       lastdata->flags |= traffic_flags;
+
        /* throttling mode inactive ? */
        if (!op->kt_ival2) {
                /* send RX_CHANGED to the user immediately */
@@ -508,7 +538,8 @@ rx_changed_settime:
  *                       received data stored in op->last_frames[]
  */
 static void bcm_rx_cmp_to_index(struct bcm_op *op, unsigned int index,
-                               const struct canfd_frame *rxdata)
+                               const struct canfd_frame *rxdata,
+                               unsigned char traffic_flags)
 {
        struct canfd_frame *cf = op->frames + op->cfsiz * index;
        struct canfd_frame *lcf = op->last_frames + op->cfsiz * index;
@@ -521,7 +552,7 @@ static void bcm_rx_cmp_to_index(struct bcm_op *op, unsigned int index,
 
        if (!(lcf->flags & RX_RECV)) {
                /* received data for the first time => send update to user */
-               bcm_rx_update_and_send(op, lcf, rxdata);
+               bcm_rx_update_and_send(op, lcf, rxdata, traffic_flags);
                return;
        }
 
@@ -529,7 +560,7 @@ static void bcm_rx_cmp_to_index(struct bcm_op *op, unsigned int index,
        for (i = 0; i < rxdata->len; i += 8) {
                if ((get_u64(cf, i) & get_u64(rxdata, i)) !=
                    (get_u64(cf, i) & get_u64(lcf, i))) {
-                       bcm_rx_update_and_send(op, lcf, rxdata);
+                       bcm_rx_update_and_send(op, lcf, rxdata, traffic_flags);
                        return;
                }
        }
@@ -537,7 +568,7 @@ static void bcm_rx_cmp_to_index(struct bcm_op *op, unsigned int index,
        if (op->flags & RX_CHECK_DLC) {
                /* do a real check in CAN frame length */
                if (rxdata->len != lcf->len) {
-                       bcm_rx_update_and_send(op, lcf, rxdata);
+                       bcm_rx_update_and_send(op, lcf, rxdata, traffic_flags);
                        return;
                }
        }
@@ -644,6 +675,7 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
        struct bcm_op *op = (struct bcm_op *)data;
        const struct canfd_frame *rxframe = (struct canfd_frame *)skb->data;
        unsigned int i;
+       unsigned char traffic_flags;
 
        if (op->can_id != rxframe->can_id)
                return;
@@ -673,15 +705,24 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
                return;
        }
 
+       /* compute flags to distinguish between own/local/remote CAN traffic */
+       traffic_flags = 0;
+       if (skb->sk) {
+               traffic_flags |= RX_LOCAL;
+               if (skb->sk == op->sk)
+                       traffic_flags |= RX_OWN;
+       }
+
        if (op->flags & RX_FILTER_ID) {
                /* the easiest case */
-               bcm_rx_update_and_send(op, op->last_frames, rxframe);
+               bcm_rx_update_and_send(op, op->last_frames, rxframe,
+                                      traffic_flags);
                goto rx_starttimer;
        }
 
        if (op->nframes == 1) {
                /* simple compare with index 0 */
-               bcm_rx_cmp_to_index(op, 0, rxframe);
+               bcm_rx_cmp_to_index(op, 0, rxframe, traffic_flags);
                goto rx_starttimer;
        }
 
@@ -698,7 +739,8 @@ static void bcm_rx_handler(struct sk_buff *skb, void *data)
                        if ((get_u64(op->frames, 0) & get_u64(rxframe, 0)) ==
                            (get_u64(op->frames, 0) &
                             get_u64(op->frames + op->cfsiz * i, 0))) {
-                               bcm_rx_cmp_to_index(op, i, rxframe);
+                               bcm_rx_cmp_to_index(op, i, rxframe,
+                                                   traffic_flags);
                                break;
                        }
                }
@@ -1675,6 +1717,9 @@ static int bcm_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
                memcpy(msg->msg_name, skb->cb, msg->msg_namelen);
        }
 
+       /* assign the flags that have been recorded in bcm_send_to_user() */
+       msg->msg_flags |= *(bcm_flags(skb));
+
        skb_free_datagram(sk, skb);
 
        return size;