The difference in V3 is proper documentation. Both code & documentation look very complete now.
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 flags in msg->msg_flags in the call to recvmsg. The Documentation/... explains the flags. Signed-off-by: Kurt Van Dijck <[email protected]> --- Documentation/networking/can.txt | 13 +++++++++++++ net/can/raw.c | 33 ++++++++++++++++++++++++++++++--- 2 files changed, 43 insertions(+), 3 deletions(-) diff --git a/Documentation/networking/can.txt b/Documentation/networking/can.txt index cd79735..bc015d0 100644 --- a/Documentation/networking/can.txt +++ b/Documentation/networking/can.txt @@ -22,6 +22,7 @@ This file contains 4.1.2 RAW socket option CAN_RAW_ERR_FILTER 4.1.3 RAW socket option CAN_RAW_LOOPBACK 4.1.4 RAW socket option CAN_RAW_RECV_OWN_MSGS + 4.1.5 RAW socket returned flags 4.2 Broadcast Manager protocol sockets (SOCK_DGRAM) 4.3 connected transport protocols (SOCK_SEQPACKET) 4.4 unconnected transport protocols (SOCK_DGRAM) @@ -471,6 +472,18 @@ solution for a couple of reasons: setsockopt(s, SOL_CAN_RAW, CAN_RAW_RECV_OWN_MSGS, &recv_own_msgs, sizeof(recv_own_msgs)); + 4.1.5 RAW socket returned 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 CAN frames on driver level, + see 3.2 and 6.2. + In order to receive such messages, CAN_RAW_RECV_OWN_MSGS must be set. + 4.2 Broadcast Manager protocol sockets (SOCK_DGRAM) 4.3 connected transport protocols (SOCK_SEQPACKET) 4.4 unconnected transport protocols (SOCK_DGRAM) diff --git a/net/can/raw.c b/net/can/raw.c index 7d77e67..a9edd69 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 pointer to store the extra msg flags for raw_recvmsg(). + * We use the space of one unsigned int beyond the 'struct sockaddr_can' + * in skb->cb. + */ +static inline unsigned int *raw_flags(struct sk_buff *skb) +{ + BUILD_BUG_ON(sizeof(skb->cb) <= (sizeof(struct sockaddr_can) + + sizeof(unsigned int))); + + /* return pointer after struct sockaddr_can */ + return (unsigned 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; + unsigned 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 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
