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CAN(4)                       Device Drivers Manual                      CAN(4)

     CAN - CAN Protocol

     #include <sys/socket.h>
     #include <netcan/can.h>

     socket(AF_CAN, SOCK_RAW, CAN_RAW);

     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

     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.

     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.

     socket(2), canloop(4), netintro(4), canconfig(8),

     SocketCAN - Wikipedia: https://en.wikipedia.org/wiki/SocketCAN Readme
     file for the Controller Area Network Protocol Family:

     The CAN protocol appeared in NetBSD 8.0.

     CANFD and error frames are not implemented.

NetBSD 8.0                       May 18, 2017                       NetBSD 8.0