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

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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 1e55659ce6 ("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>
This commit is contained in:
Nicolas Maier 2024-01-20 09:10:18 +01:00 committed by Marc Kleine-Budde
parent 970cb1ceda
commit fec846fa7e
2 changed files with 75 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
Documentation/networking/can.rst
View File

@ -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)
-----------------------------------------------

69
net/can/bcm.c
View File

@ -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;