canfd: add support for CAN FD in CAN_RAW sockets

- introduce a new sockopt CAN_RAW_FD_FRAMES to allow CAN FD frames
- handle CAN frames and CAN FD frames simultaneously when enabled

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

2 files changed, 48 insertions, 5 deletions

diff --git a/include/linux/can/raw.h b/include/linux/can/raw.h
index 781f3a3701be..a814062b0719 100644
--- a/include/linux/can/raw.h
+++ b/include/linux/can/raw.h
@@ -23,7 +23,8 @@ enum {
         CAN_RAW_FILTER = 1,     /* set 0 .. n can_filter(s)          */
         CAN_RAW_ERR_FILTER,     /* set filter for error frames       */
         CAN_RAW_LOOPBACK,       /* local loopback (default:on)       */
-        CAN_RAW_RECV_OWN_MSGS   /* receive my own msgs (default:off) */
+        CAN_RAW_RECV_OWN_MSGS,  /* receive my own msgs (default:off) */
+        CAN_RAW_FD_FRAMES,      /* allow CAN FD frames (default:off) */
 };
 
 #endif
diff --git a/net/can/raw.c b/net/can/raw.c
index 46cca3a91d19..3e9c89356a93 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -82,6 +82,7 @@ struct raw_sock {
         struct notifier_block notifier;
         int loopback;
         int recv_own_msgs;
+        int fd_frames;
         int count;                 /* number of active filters */
         struct can_filter dfilter; /* default/single filter */
         struct can_filter *filter; /* pointer to filter(s) */
@@ -119,6 +120,14 @@ static void raw_rcv(struct sk_buff *oskb, void *data)
         if (!ro->recv_own_msgs && oskb->sk == sk)
                 return;
 
+        /* do not pass frames with DLC > 8 to a legacy socket */
+        if (!ro->fd_frames) {
+                struct canfd_frame *cfd = (struct canfd_frame *)oskb->data;
+
+                if (unlikely(cfd->len > CAN_MAX_DLEN))
+                        return;
+        }
+
         /* clone the given skb to be able to enqueue it into the rcv queue */
         skb = skb_clone(oskb, GFP_ATOMIC);
         if (!skb)
@@ -291,6 +300,7 @@ static int raw_init(struct sock *sk)
         /* set default loopback behaviour */
         ro->loopback         = 1;
         ro->recv_own_msgs    = 0;
+        ro->fd_frames        = 0;
 
         /* set notifier */
         ro->notifier.notifier_call = raw_notifier;
@@ -569,6 +579,15 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,
 
                 break;
 
+        case CAN_RAW_FD_FRAMES:
+                if (optlen != sizeof(ro->fd_frames))
+                        return -EINVAL;
+
+                if (copy_from_user(&ro->fd_frames, optval, optlen))
+                        return -EFAULT;
+
+                break;
+
         default:
                 return -ENOPROTOOPT;
         }
@@ -627,6 +646,12 @@ static int raw_getsockopt(struct socket *sock, int level, int optname,
                 val = &ro->recv_own_msgs;
                 break;
 
+        case CAN_RAW_FD_FRAMES:
+                if (len > sizeof(int))
+                        len = sizeof(int);
+                val = &ro->fd_frames;
+                break;
+
         default:
                 return -ENOPROTOOPT;
         }
@@ -662,8 +687,13 @@ static int raw_sendmsg(struct kiocb *iocb, struct socket *sock,
         } else
                 ifindex = ro->ifindex;
 
-        if (size != sizeof(struct can_frame))
-                return -EINVAL;
+        if (ro->fd_frames) {
+                if (unlikely(size != CANFD_MTU && size != CAN_MTU))
+                        return -EINVAL;
+        } else {
+                if (unlikely(size != CAN_MTU))
+                        return -EINVAL;
+        }
 
         dev = dev_get_by_index(&init_net, ifindex);
         if (!dev)
@@ -705,7 +735,9 @@ static int raw_recvmsg(struct kiocb *iocb, struct socket *sock,
                        struct msghdr *msg, size_t size, int flags)
 {
         struct sock *sk = sock->sk;
+        struct raw_sock *ro = raw_sk(sk);
         struct sk_buff *skb;
+        int rxmtu;
         int err = 0;
         int noblock;
 
@@ -716,10 +748,20 @@ static int raw_recvmsg(struct kiocb *iocb, struct socket *sock,
         if (!skb)
                 return err;
 
-        if (size < skb->len)
+        /*
+         * when serving a legacy socket the DLC <= 8 is already checked inside
+         * raw_rcv(). Now check if we need to pass a canfd_frame to a legacy
+         * socket and cut the possible CANFD_MTU/CAN_MTU length to CAN_MTU
+         */
+        if (!ro->fd_frames)
+                rxmtu = CAN_MTU;
+        else
+                rxmtu = skb->len;
+
+        if (size < rxmtu)
                 msg->msg_flags |= MSG_TRUNC;
         else
-                size = skb->len;
+                size = rxmtu;
 
         err = memcpy_toiovec(msg->msg_iov, skb->data, size);
         if (err < 0) {