From 1e55659ce6ddb5247cee0b1f720d77a799902b85 Mon Sep 17 00:00:00 2001 From: Oliver Hartkopp Date: Tue, 19 Oct 2010 09:32:04 +0000 Subject: can-raw: add msg_flags to distinguish local traffic 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. The distinction is made by returning flags in msg->msg_flags in the call to recvmsg(). The added documentation explains the introduced flags. Signed-off-by: Kurt Van Dijck Signed-off-by: Oliver Hartkopp Signed-off-by: David S. Miller --- Documentation/networking/can.txt | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'Documentation') diff --git a/Documentation/networking/can.txt b/Documentation/networking/can.txt index cd79735013f9..5b04b67ddca2 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 message 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 +472,17 @@ 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 message 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 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) -- cgit v1.2.1