CAN(4)

NAME
CAN - CAN Protocol

SYNOPSIS
#include <sys/socket.h>
#include <netcan/can.h>
int
socket(AF_CAN, SOCK_RAW, CAN_RAW);

DESCRIPTION
CAN is the network layer protocol used on top of CAN bus networks. At this time only the SOCK_RAW socket type is supported. This protocol layer is intended to be compatible with the Linux SocketCAN implementation.

  ADDRESSING
A CAN frame consists of a 11 bits (standard frame format) or 29 bits (extended frame format) identifier, followed by up to 8 data bytes. The interpretation of the identifier is application-dependent, the CAN standard itself doesn't define an addressing.

The CAN layer uses a 32bits identifier. The 3 upper bits are used as control flags. The extended frame format is selected by setting the CAN_EFF_FLAG control bit.

The socket address is defined as

    struct sockaddr_can {
            u_int8_t        can_len;
            sa_family_t     can_family;
            int             can_ifindex;
            union {
                    /* transport protocol class address information */
                    struct { canid_t rx_id, tx_id; } tp;
                    /* reserved for future CAN protocols address information */
            } can_addr;
    };

For CAN raw sockets, the 32bits identifier is part of the message data. The can_addr field of the sockaddr structure is not used.

  MESSAGE
Raw CAN sockets use fixed-length messages defined as follow:

    struct can_frame {
            canid_t can_id; /* ID + EFF/RTR/ERR flags */
            uint8_t can_dlc; /* frame payload length in byte (0 .. CAN_MAX_DLEN) */
            uint8_t __pad;
            uint8_t __res0;
            uint8_t __res1;
            uint8_t data[CAN_MAX_DLEN] __aligned(8);
    };

The lower 11 bits (for standard frames) or 29 bits (for extended frames) are used as the on-wire identifier. The CAN_EFF_FLAG bit is set in can_id for extended frames. The CAN_RTR_FLAG bit is set in can_id for remote transmission request frames.

SEE ALSO
socket(2), canloop(4), netintro(4), canconfig(8), /usr/include/netcan/can.h

SocketCAN - Wikipedia: https://en.wikipedia.org/wiki/SocketCAN Readme file for the Controller Area Network Protocol Family: https://www.kernel.org/doc/Documentation/networking/can.txt

HISTORY
The CAN protocol appeared in NetBSD 8.0.

BUGS
CANFD and error frames are not implemented.