bpo-37085: Expose SocketCAN bcm_msg_head flags (#13646)

Expose the CAN_BCM SocketCAN constants used in the bcm_msg_head struct
flags (provided by <linux/can/bcm.h>) under the socket library.

This adds the following constants with a CAN_BCM prefix:

  * SETTIMER
  * STARTTIMER
  * TX_COUNTEVT
  * TX_ANNOUNCE
  * TX_CP_CAN_ID
  * RX_FILTER_ID
  * RX_CHECK_DLC
  * RX_NO_AUTOTIMER
  * RX_ANNOUNCE_RESUME
  * TX_RESET_MULTI_IDX
  * RX_RTR_FRAME
  * CAN_FD_FRAME

The CAN_FD_FRAME flag was introduced in the 4.8 kernel, while the other
ones were present since SocketCAN drivers were mainlined in 2.6.25. As
such, it is probably unnecessary to guard against these constants being
missing.

Author: karlding

Doc/library/socket.rst

@@ -391,6 +391,9 @@ Constants
 
    .. availability:: Linux >= 2.6.25.
 
+   .. note::
+      The :data:`CAN_BCM_CAN_FD_FRAME` flag is only available on Linux >= 4.8.
+
    .. versionadded:: 3.4
 
 .. data:: CAN_RAW_FD_FRAMES

Lib/test/test_socket.py

@@ -1908,6 +1908,19 @@ def testBCMConstants(self):
         socket.CAN_BCM_RX_TIMEOUT   # cyclic message is absent
         socket.CAN_BCM_RX_CHANGED   # updated CAN frame (detected content change)
 
+        # flags
+        socket.CAN_BCM_SETTIMER
+        socket.CAN_BCM_STARTTIMER
+        socket.CAN_BCM_TX_COUNTEVT
+        socket.CAN_BCM_TX_ANNOUNCE
+        socket.CAN_BCM_TX_CP_CAN_ID
+        socket.CAN_BCM_RX_FILTER_ID
+        socket.CAN_BCM_RX_CHECK_DLC
+        socket.CAN_BCM_RX_NO_AUTOTIMER
+        socket.CAN_BCM_RX_ANNOUNCE_RESUME
+        socket.CAN_BCM_TX_RESET_MULTI_IDX
+        socket.CAN_BCM_RX_RTR_FRAME
+
     def testCreateSocket(self):
         with socket.socket(socket.PF_CAN, socket.SOCK_RAW, socket.CAN_RAW) as s:
             pass

Misc/ACKS

@@ -397,6 +397,7 @@ Alon Diamant
 Toby Dickenson
 Mark Dickinson
 Jack Diederich
+Karl Ding
 Daniel Diniz
 Humberto Diogenes
 Yves Dionne

Misc/NEWS.d/next/Library/2019-06-18-16-29-31.bpo-37085.GeYaD6.rst

@@ -0,0 +1,2 @@
+Add the optional Linux SocketCAN Broadcast Manager constants, used as flags
+to configure the BCM behaviour, in the socket module.  Patch by Karl Ding.

Modules/socketmodule.c

@@ -7656,6 +7656,8 @@ PyInit__socket(void)
 #endif
 #ifdef HAVE_LINUX_CAN_BCM_H
     PyModule_AddIntMacro(m, CAN_BCM);
+
+    /* BCM opcodes */
     PyModule_AddIntConstant(m, "CAN_BCM_TX_SETUP", TX_SETUP);
     PyModule_AddIntConstant(m, "CAN_BCM_TX_DELETE", TX_DELETE);
     PyModule_AddIntConstant(m, "CAN_BCM_TX_READ", TX_READ);
@@ -7668,6 +7670,23 @@ PyInit__socket(void)
     PyModule_AddIntConstant(m, "CAN_BCM_RX_STATUS", RX_STATUS);
     PyModule_AddIntConstant(m, "CAN_BCM_RX_TIMEOUT", RX_TIMEOUT);
     PyModule_AddIntConstant(m, "CAN_BCM_RX_CHANGED", RX_CHANGED);
+
+    /* BCM flags */
+    PyModule_AddIntConstant(m, "CAN_BCM_SETTIMER", SETTIMER);
+    PyModule_AddIntConstant(m, "CAN_BCM_STARTTIMER", STARTTIMER);
+    PyModule_AddIntConstant(m, "CAN_BCM_TX_COUNTEVT", TX_COUNTEVT);
+    PyModule_AddIntConstant(m, "CAN_BCM_TX_ANNOUNCE", TX_ANNOUNCE);
+    PyModule_AddIntConstant(m, "CAN_BCM_TX_CP_CAN_ID", TX_CP_CAN_ID);
+    PyModule_AddIntConstant(m, "CAN_BCM_RX_FILTER_ID", RX_FILTER_ID);
+    PyModule_AddIntConstant(m, "CAN_BCM_RX_CHECK_DLC", RX_CHECK_DLC);
+    PyModule_AddIntConstant(m, "CAN_BCM_RX_NO_AUTOTIMER", RX_NO_AUTOTIMER);
+    PyModule_AddIntConstant(m, "CAN_BCM_RX_ANNOUNCE_RESUME", RX_ANNOUNCE_RESUME);
+    PyModule_AddIntConstant(m, "CAN_BCM_TX_RESET_MULTI_IDX", TX_RESET_MULTI_IDX);
+    PyModule_AddIntConstant(m, "CAN_BCM_RX_RTR_FRAME", RX_RTR_FRAME);
+#ifdef CAN_FD_FRAME
+    /* CAN_FD_FRAME was only introduced in the 4.8.x kernel series */
+    PyModule_AddIntConstant(m, "CAN_BCM_CAN_FD_FRAME", CAN_FD_FRAME);
+#endif
 #endif
 #ifdef SOL_RDS
     PyModule_AddIntMacro(m, SOL_RDS);