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authorOliver Hartkopp <socketcan@hartkopp.net>2010-10-19 09:32:04 +0000
committerDavid S. Miller <davem@davemloft.net>2010-10-21 04:27:03 -0700
commit1e55659ce6ddb5247cee0b1f720d77a799902b85 (patch)
tree335e43324d5ad5e0979fb30e333cb1a4e1a47085 /Documentation/networking/can.txt
parent32a875adcdcf5f470bf967250cfd01722e23844f (diff)
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 <kurt.van.dijck@eia.be> Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/networking/can.txt')
-rw-r--r--Documentation/networking/can.txt12
1 files changed, 12 insertions, 0 deletions
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)