CAN has no addressing scheme. It is currently impossible for userspace to tell is a received CAN frame comes from another process on the local host, or from a remote CAN device. This patch add support for userspace applications to distinguish between 'own', 'local' and 'remote' CAN traffic. Distinction is made by returning some flags in msg->msg_flags in the call to recvmsg. MSG_CONFIRM flag means 'own', as in 'transmission confirmation' MSG_DONTROUTE flag means 'local', not routed. Obviously, msgs with MSG_CONFIRM will have MSG_DONTROUTE set too.
Please note that on SocketCAN mailing list, different opinions exist on the exact meaning of MSG_DONTROUTE. Better (=more intuitive) alternatives are appreciated. Signed-off-by: Kurt Van Dijck <[email protected]> --- net/can/raw.c | 33 ++++++++++++++++++++++++++++++--- 1 files changed, 30 insertions(+), 3 deletions(-) diff --git a/net/can/raw.c b/net/can/raw.c index 7d77e67..f98709e 100644 --- a/net/can/raw.c +++ b/net/can/raw.c @@ -90,23 +90,39 @@ struct raw_sock { can_err_mask_t err_mask; }; +/* + * return some space to store extra msg flags in. + * We use 1 int beyond the 'struct sockaddr_can' in skb->cb + * to store those. + * These flags will be use in raw_recvmsg() + */ +static inline int *raw_flags(struct sk_buff *skb) +{ + BUILD_BUG_ON(sizeof(skb->cb) + <= (sizeof(struct sockaddr_can) + sizeof(int))); + /* return pointer after struct sockaddr_can */ + return (int *)(&((struct sockaddr_can *)skb->cb)[1]); +} + static inline struct raw_sock *raw_sk(const struct sock *sk) { return (struct raw_sock *)sk; } -static void raw_rcv(struct sk_buff *skb, void *data) +static void raw_rcv(struct sk_buff *oskb, void *data) { struct sock *sk = (struct sock *)data; struct raw_sock *ro = raw_sk(sk); struct sockaddr_can *addr; + struct sk_buff *skb; + int *pflags; /* check the received tx sock reference */ - if (!ro->recv_own_msgs && skb->sk == sk) + if (!ro->recv_own_msgs && oskb->sk == sk) return; /* clone the given skb to be able to enqueue it into the rcv queue */ - skb = skb_clone(skb, GFP_ATOMIC); + skb = skb_clone(oskb, GFP_ATOMIC); if (!skb) return; @@ -123,6 +139,14 @@ static void raw_rcv(struct sk_buff *skb, void *data) addr->can_family = AF_CAN; addr->can_ifindex = skb->dev->ifindex; + /* prepare the flags for raw_recvmsg() */ + pflags = raw_flags(skb); + *pflags = 0; + if (oskb->sk) + *pflags |= MSG_DONTROUTE; + if (oskb->sk == sk) + *pflags |= MSG_CONFIRM; + if (sock_queue_rcv_skb(sk, skb) < 0) kfree_skb(skb); } @@ -707,6 +731,9 @@ static int raw_recvmsg(struct kiocb *iocb, struct socket *sock, memcpy(msg->msg_name, skb->cb, msg->msg_namelen); } + /* assign the flags that have been recorded in in raw_rcv() */ + msg->msg_flags |= *(raw_flags(skb)); + skb_free_datagram(sk, skb); return size; _______________________________________________ Socketcan-core mailing list [email protected] https://lists.berlios.de/mailman/listinfo/socketcan-core
