When reading through the values exposed via the socket library, I noticed that currently, only the SocketCAN BCM opcode enums are exposed via the socket constants. These correspond to the following from the Linux headers: enum {	TX_SETUP = 1,	/* create (cyclic) transmission task */	TX_DELETE,	/* remove (cyclic) transmission task */	TX_READ,	/* read properties of (cyclic) transmission task */	TX_SEND,	/* send one CAN frame */	RX_SETUP,	/* create RX content filter subscription */	RX_DELETE,	/* remove RX content filter subscription */	RX_READ,	/* read properties of RX content filter subscription */	TX_STATUS,	/* reply to TX_READ request */	TX_EXPIRED,	/* notification on performed transmissions (count=0) */	RX_STATUS,	/* reply to RX_READ request */	RX_TIMEOUT,	/* cyclic message is absent */	RX_CHANGED	/* updated CAN frame (detected content change) */ }; It would be nice to expose the BCM flags #defines as well. #define SETTIMER 0x0001 #define STARTTIMER 0x0002 #define TX_COUNTEVT 0x0004 #define TX_ANNOUNCE 0x0008 #define TX_CP_CAN_ID 0x0010 #define RX_FILTER_ID 0x0020 #define RX_CHECK_DLC 0x0040 #define RX_NO_AUTOTIMER 0x0080 #define RX_ANNOUNCE_RESUME 0x0100 #define TX_RESET_MULTI_IDX 0x0200 #define RX_RTR_FRAME 0x0400 #define CAN_FD_FRAME 0x0800 These BCM flags are used as part of the BCM header that has the aforementioned opcodes. The flags are set on the bcm_msg_head struct: struct bcm_msg_head { __u32 opcode; __u32 flags; __u32 count; struct bcm_timeval ival1, ival2; canid_t can_id; __u32 nframes; struct can_frame frames[0]; }; The existing documentation for the BCM constants (https://docs.python.org/3/library/socket.html#socket.CAN_BCM) seems to imply that these constants should already be included, but they are not. See the Linux headers for more details: https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/can/bcm.h

 New changeset 31c4fd2a10d90beaa37d630e5f74a471e14e089d by Łukasz Langa (karl ding) in branch 'master': bpo-37085: Expose SocketCAN bcm_msg_head flags (#13646) https://github.com/python/cpython/commit/31c4fd2a10d90beaa37d630e5f74a471e14e089d 

 New changeset d8b914a30b0849476345a19ce0a0ab1ade171b19 by Miss Islington (bot) in branch '3.8': bpo-37085: Expose SocketCAN bcm_msg_head flags (GH-13646) https://github.com/python/cpython/commit/d8b914a30b0849476345a19ce0a0ab1ade171b19 

Karl, many thanks for bringing this up, making a PR and iterating on it with me!