[RFC PATCH v3 2/2] can: support XL only content on real CAN XL interfaces

[Oliver Hartkopp <socketcan@hartkopp.net>]

The CAN XL devices can be configured as CAN XL only with 'xl on fd off'
which is currently not supported as the CAN XL sockopt on the CAN_RAW
socket implicitly enables CAN FD support.

This patch removes this XL/FD connection for real CAN XL interfaces and
rejects CAN FD content on CAN XL interfaces with 'fd off'.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
 include/linux/can/dev.h | 12 ++++++++++++
 net/can/raw.c           | 32 ++++++++++++++------------------
 2 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 9a92cbe5b2cb..9fa139cc793e 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -183,10 +183,22 @@ struct net_device *alloc_candev_mqs(int sizeof_priv, unsigned int echo_skb_max,
 void free_candev(struct net_device *dev);
 
 /* a candev safe wrapper around netdev_priv */
 struct can_priv *safe_candev_priv(struct net_device *dev);
 
+static inline bool can_dev_ctrlmode_fd_on(struct net_device *dev)
+{
+	struct can_priv *priv = safe_candev_priv(dev);
+
+	/* check ctrlmode on real CAN interfaces */
+	if (priv)
+		return (priv->ctrlmode & CAN_CTRLMODE_FD);
+
+	/* virtual CAN FD/XL interfaces always support CAN FD */
+	return true;
+}
+
 int open_candev(struct net_device *dev);
 void close_candev(struct net_device *dev);
 int can_change_mtu(struct net_device *dev, int new_mtu);
 int can_eth_ioctl_hwts(struct net_device *netdev, struct ifreq *ifr, int cmd);
 int can_ethtool_op_get_ts_info_hwts(struct net_device *dev,
diff --git a/net/can/raw.c b/net/can/raw.c
index f48b1f3fd6e8..6cd1f9cb050d 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -558,11 +558,10 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 	struct raw_sock *ro = raw_sk(sk);
 	struct can_filter *filter = NULL;  /* dyn. alloc'ed filters */
 	struct can_filter sfilter;         /* single filter */
 	struct net_device *dev = NULL;
 	can_err_mask_t err_mask = 0;
-	int fd_frames;
 	int count = 0;
 	int err = 0;
 
 	if (level != SOL_CAN_RAW)
 		return -EINVAL;
@@ -698,33 +697,25 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 			return -EFAULT;
 
 		break;
 
 	case CAN_RAW_FD_FRAMES:
-		if (optlen != sizeof(fd_frames))
+		if (optlen != sizeof(ro->fd_frames))
 			return -EINVAL;
 
-		if (copy_from_sockptr(&fd_frames, optval, optlen))
+		if (copy_from_sockptr(&ro->fd_frames, optval, optlen))
 			return -EFAULT;
 
-		/* Enabling CAN XL includes CAN FD */
-		if (ro->xl_frames && !fd_frames)
-			return -EINVAL;
-
-		ro->fd_frames = fd_frames;
 		break;
 
 	case CAN_RAW_XL_FRAMES:
 		if (optlen != sizeof(ro->xl_frames))
 			return -EINVAL;
 
 		if (copy_from_sockptr(&ro->xl_frames, optval, optlen))
 			return -EFAULT;
 
-		/* 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;
@@ -879,24 +870,29 @@ static void raw_put_canxl_vcid(struct raw_sock *ro, struct sk_buff *skb)
 		cxl->prio &= CANXL_PRIO_MASK;
 		cxl->prio |= ro->tx_vcid_shifted;
 	}
 }
 
-static unsigned int raw_check_txframe(struct raw_sock *ro, struct sk_buff *skb, int mtu)
+static unsigned int raw_check_txframe(struct raw_sock *ro, struct sk_buff *skb, struct net_device *dev)
 {
 	/* Classical CAN -> no checks for flags and device capabilities */
 	if (can_is_can_skb(skb))
 		return CAN_MTU;
 
-	/* CAN FD -> needs to be enabled and a CAN FD or CAN XL device */
-	if (ro->fd_frames && can_is_canfd_skb_set_fdf(skb) &&
-	    (mtu == CANFD_MTU || can_is_canxl_dev_mtu(mtu)))
-		return CANFD_MTU;
+	/* CAN FD -> needs to be enabled in a CAN FD or CAN XL device */
+	if (ro->fd_frames && can_is_canfd_skb_set_fdf(skb)) {
+		/* real/virtual CAN FD interface */
+		if (dev->mtu == CANFD_MTU)
+			return CANFD_MTU;
+		if (can_is_canxl_dev_mtu(dev->mtu) &&
+		    can_dev_ctrlmode_fd_on(dev))
+			return CANFD_MTU;
+	}
 
 	/* 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(dev->mtu))
 		return CANXL_MTU;
 
 	return 0;
 }
 
@@ -948,11 +944,11 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 		goto free_skb;
 
 	err = -EINVAL;
 
 	/* check for valid CAN (CC/FD/XL) frame content */
-	txmtu = raw_check_txframe(ro, skb, dev->mtu);
+	txmtu = raw_check_txframe(ro, skb, dev);
 	if (!txmtu)
 		goto free_skb;
 
 	/* only CANXL: clear/forward/set VCID value */
 	if (txmtu == CANXL_MTU)
-- 
2.47.3