[PATCH v4] canxl: add virtual CAN network identifier support

[Oliver Hartkopp <socketcan@hartkopp.net>]

CAN XL data frames contain an 8-bit virtual CAN network identifier (VCID).
A VCID value of zero represents an 'untagged' CAN XL frame.

To receive and send these optional VCIDs via CAN_RAW sockets a new socket
option CAN_RAW_XL_VCID_OPTS is introduced to define/access VCID content:

- tx: set the outgoing VCID value by the kernel (one fixed 8-bit value)
- tx: pass through VCID values from the user space (e.g. for traffic replay)
- rx: apply VCID receive filter (value/mask) to be passed to the user space

With the 'tx pass through' option CAN_RAW_XL_VCID_TX_PASS all valid VCID
values can be sent, e.g. to replay full qualified CAN XL traffic.

The VCID value provided for the CAN_RAW_XL_VCID_TX_SET option will
override the VCID value in the struct canxl_frame.vcid element defined
for CAN_RAW_XL_VCID_TX_PASS when both flags are set.

With a rx_vcid_mask of zero all possible VCID values (0x00 - 0xFF) are
passed to the user space when the CAN_RAW_XL_VCID_RX_FILTER flag is set.
Without this flag only untagged CAN XL frames (VCID = 0x00) are delivered
to the user space (default).

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
 include/uapi/linux/can.h     | 41 ++++++++++++++--------
 include/uapi/linux/can/raw.h | 14 ++++++++
 net/can/af_can.c             |  2 ++
 net/can/raw.c                | 66 ++++++++++++++++++++++++++++++++++--
 4 files changed, 106 insertions(+), 17 deletions(-)

diff --git a/include/uapi/linux/can.h b/include/uapi/linux/can.h
index 939db2388208..8dcd8a9b5676 100644
--- a/include/uapi/linux/can.h
+++ b/include/uapi/linux/can.h
@@ -44,10 +44,11 @@
  */
 
 #ifndef _UAPI_CAN_H
 #define _UAPI_CAN_H
 
+#include <asm/byteorder.h>
 #include <linux/types.h>
 #include <linux/socket.h>
 #include <linux/stddef.h> /* for offsetof */
 
 /* controller area network (CAN) kernel definitions */
@@ -193,26 +194,38 @@ struct canfd_frame {
 #define CANXL_XLF 0x80 /* mandatory CAN XL frame flag (must always be set!) */
 #define CANXL_SEC 0x01 /* Simple Extended Content (security/segmentation) */
 
 /**
  * struct canxl_frame - CAN with e'X'tended frame 'L'ength frame structure
- * @prio:  11 bit arbitration priority with zero'ed CAN_*_FLAG flags
- * @flags: additional flags for CAN XL
- * @sdt:   SDU (service data unit) type
- * @len:   frame payload length in byte (CANXL_MIN_DLEN .. CANXL_MAX_DLEN)
- * @af:    acceptance field
- * @data:  CAN XL frame payload (CANXL_MIN_DLEN .. CANXL_MAX_DLEN byte)
- *
- * @prio shares the same position as @can_id from struct can[fd]_frame.
+ * @prio:   11 bit arbitration priority (unused 5 bits must be set to zero)
+ *          Shares the lower 16 bits of @can_id from struct can[fd]_frame
+ * @vcid:   CAN XL virtual CAN network identifier
+ * @__res0: reserved / padding must be set to zero to maintain the CAN filter
+ *          functionality as is holds the @can_id flags CAN_xxx_FLAG
+ * @flags:  additional flags for CAN XL
+ * @sdt:    SDU (service data unit) type
+ * @len:    frame payload length in byte (CANXL_MIN_DLEN .. CANXL_MAX_DLEN)
+ * @af:     acceptance field
+ * @data:   CAN XL frame payload (CANXL_MIN_DLEN .. CANXL_MAX_DLEN byte)
  */
 struct canxl_frame {
-	canid_t prio;  /* 11 bit priority for arbitration (canid_t) */
-	__u8    flags; /* additional flags for CAN XL */
-	__u8    sdt;   /* SDU (service data unit) type */
-	__u16   len;   /* frame payload length in byte */
-	__u32   af;    /* acceptance field */
-	__u8    data[CANXL_MAX_DLEN];
+#if defined(__LITTLE_ENDIAN)
+	__u16 prio;   /* 11 bit priority for arbitration */
+	__u8  vcid;   /* virtual CAN network identifier */
+	__u8  __res0; /* reserved / padding must be set to zero */
+#elif defined(__BIG_ENDIAN)
+	__u8  __res0; /* reserved / padding must be set to zero */
+	__u8  vcid;   /* virtual CAN network identifier */
+	__u16 prio;   /* 11 bit priority for arbitration */
+#else
+#error "Unknown endianness"
+#endif
+	__u8  flags;  /* additional flags for CAN XL */
+	__u8  sdt;    /* SDU (service data unit) type */
+	__u16 len;    /* frame payload length in byte */
+	__u32 af;     /* acceptance field */
+	__u8  data[CANXL_MAX_DLEN];
 };
 
 #define CAN_MTU		(sizeof(struct can_frame))
 #define CANFD_MTU	(sizeof(struct canfd_frame))
 #define CANXL_MTU	(sizeof(struct canxl_frame))
diff --git a/include/uapi/linux/can/raw.h b/include/uapi/linux/can/raw.h
index 31622c9b7988..88e4e8176b89 100644
--- a/include/uapi/linux/can/raw.h
+++ b/include/uapi/linux/can/raw.h
@@ -63,8 +63,22 @@ enum {
 	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 */
 	CAN_RAW_XL_FRAMES,	/* allow CAN XL frames (default:off) */
+	CAN_RAW_XL_VCID_OPTS,	/* CAN XL VCID configuration options */
 };
 
+/* configuration for CAN XL virtual CAN identifier (VCID) handling */
+struct can_raw_vcid_options {
+	__u8 flags;		/* flags for vcid (filter) behaviour */
+	__u8 tx_vcid;		/* VCID value set into canxl_frame.vcid */
+	__u8 rx_vcid;		/* VCID value for VCID filter */
+	__u8 rx_vcid_mask;	/* VCID mask for VCID filter */
+};
+
+/* can_raw_vcid_options.flags for CAN XL virtual CAN identifier handling */
+#define CAN_RAW_XL_VCID_TX_SET		0x01
+#define CAN_RAW_XL_VCID_TX_PASS		0x02
+#define CAN_RAW_XL_VCID_RX_FILTER	0x04
+
 #endif /* !_UAPI_CAN_RAW_H */
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 7343fd487dbe..707576eeeb58 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -863,10 +863,12 @@ static __init int can_init(void)
 	int err;
 
 	/* check for correct padding to be able to use the structs similarly */
 	BUILD_BUG_ON(offsetof(struct can_frame, len) !=
 		     offsetof(struct canfd_frame, len) ||
+		     offsetof(struct can_frame, len) !=
+		     offsetof(struct canxl_frame, flags) ||
 		     offsetof(struct can_frame, data) !=
 		     offsetof(struct canfd_frame, data));
 
 	pr_info("can: controller area network core\n");
 
diff --git a/net/can/raw.c b/net/can/raw.c
index e6b822624ba2..3083df64723c 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -89,10 +89,11 @@ struct raw_sock {
 	struct list_head notifier;
 	int loopback;
 	int recv_own_msgs;
 	int fd_frames;
 	int xl_frames;
+	struct can_raw_vcid_options raw_vcid_opts;
 	int join_filters;
 	int count;                 /* number of active filters */
 	struct can_filter dfilter; /* default/single filter */
 	struct can_filter *filter; /* pointer to filter(s) */
 	can_err_mask_t err_mask;
@@ -132,14 +133,34 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
 	/* check the received tx sock reference */
 	if (!ro->recv_own_msgs && oskb->sk == sk)
 		return;
 
 	/* make sure to not pass oversized frames to the socket */
-	if ((!ro->fd_frames && can_is_canfd_skb(oskb)) ||
-	    (!ro->xl_frames && can_is_canxl_skb(oskb)))
+	if (!ro->fd_frames && can_is_canfd_skb(oskb))
 		return;
 
+	if (can_is_canxl_skb(oskb)) {
+		struct canxl_frame *cxl = (struct canxl_frame *)oskb->data;
+		struct can_raw_vcid_options *ropts = &ro->raw_vcid_opts;
+
+		/* make sure to not pass oversized frames to the socket */
+		if (!ro->xl_frames)
+			return;
+
+		/* filter CAN XL VCID content */
+		if (ropts->flags & CAN_RAW_XL_VCID_RX_FILTER) {
+			/* apply VCID filter if user enabled the filter */
+			if ((cxl->vcid & ropts->rx_vcid_mask) !=
+			    (ropts->rx_vcid & ropts->rx_vcid_mask))
+				return;
+		} else {
+			/* no filter => do not forward VCID tagged frames */
+			if (cxl->vcid)
+				return;
+		}
+	}
+
 	/* eliminate multiple filter matches for the same skb */
 	if (this_cpu_ptr(ro->uniq)->skb == oskb &&
 	    this_cpu_ptr(ro->uniq)->skbcnt == can_skb_prv(oskb)->skbcnt) {
 		if (!ro->join_filters)
 			return;
@@ -696,10 +717,19 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 		/* Enabling CAN XL includes CAN FD */
 		if (ro->xl_frames)
 			ro->fd_frames = ro->xl_frames;
 		break;
 
+	case CAN_RAW_XL_VCID_OPTS:
+		if (optlen != sizeof(ro->raw_vcid_opts))
+			return -EINVAL;
+
+		if (copy_from_sockptr(&ro->raw_vcid_opts, optval, optlen))
+			return -EFAULT;
+
+		break;
+
 	case CAN_RAW_JOIN_FILTERS:
 		if (optlen != sizeof(ro->join_filters))
 			return -EINVAL;
 
 		if (copy_from_sockptr(&ro->join_filters, optval, optlen))
@@ -784,10 +814,25 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
 		if (len > sizeof(int))
 			len = sizeof(int);
 		val = &ro->xl_frames;
 		break;
 
+	case CAN_RAW_XL_VCID_OPTS:
+		/* user space buffer to small for VCID opts? */
+		if (len < sizeof(ro->raw_vcid_opts)) {
+			/* return -ERANGE and needed space in optlen */
+			err = -ERANGE;
+			if (put_user(sizeof(ro->raw_vcid_opts), optlen))
+				err = -EFAULT;
+		} else {
+			if (len > sizeof(ro->raw_vcid_opts))
+				len = sizeof(ro->raw_vcid_opts);
+			if (copy_to_user(optval, &ro->raw_vcid_opts, len))
+				err = -EFAULT;
+		}
+		break;
+
 	case CAN_RAW_JOIN_FILTERS:
 		if (len > sizeof(int))
 			len = sizeof(int);
 		val = &ro->join_filters;
 		break;
@@ -814,12 +859,27 @@ static bool raw_bad_txframe(struct raw_sock *ro, struct sk_buff *skb, int mtu)
 	    (mtu == CANFD_MTU || can_is_canxl_dev_mtu(mtu)))
 		return false;
 
 	/* CAN XL -> needs to be enabled and a CAN XL device */
 	if (ro->xl_frames && can_is_canxl_skb(skb) &&
-	    can_is_canxl_dev_mtu(mtu))
+	    can_is_canxl_dev_mtu(mtu)) {
+		struct canxl_frame *cxl = (struct canxl_frame *)skb->data;
+		struct can_raw_vcid_options *ropts = &ro->raw_vcid_opts;
+
+		/* sanitize non CAN XL bits */
+		cxl->__res0 = 0;
+
+		/* clear VCID in CAN XL frame if pass through is disabled */
+		if (!(ropts->flags & CAN_RAW_XL_VCID_TX_PASS))
+			cxl->vcid = 0;
+
+		/* set VCID in CAN XL frame if enabled */
+		if (ropts->flags & CAN_RAW_XL_VCID_TX_SET)
+			cxl->vcid = ropts->tx_vcid;
+
 		return false;
+	}
 
 	return true;
 }
 
 static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
-- 
2.39.2