socketcan_v4.patch:
 - dummy question: why an address is a tuple with 1 string instead of just the string? Does AF_UNIX also uses a tuple of 1 string?
 - the example should also use struct.pack() to create the frame, I don't like hardcoded BLOB
 - in test_socket: _have_socket_can() interprets permission denied as "CAN is not supported", it would be nice to provide a better skip message. Create maybe a decorator based?
 - _have_socket_can(): you may move s.close() outside the try block (add maybe a "else:" block?) because you may hide a real bug in .close()
 - data += b'\0' * (8 - can_dlc): I prefer data = data.ljust(8, '\x00')
 - you might add frame encoder/decoder in your example
 - if (!strcmp(PyBytes_AS_STRING(interfaceName), "")) hum..... PyBytes_GET_SIZE(intername)==0 should be enough
 - you truncate the interface name, it can be surprising, I would prefer an error (e.g. "interface name too long: 20 characters, the maximum is 10 characters" ?)
 - (oh no! don't include horrible configure diff in patches for the bug tracker :-p)

In which Linux version was CAN introduced?