How to create a stop-filter (instead of a pass-filter) when reading CAN messages? [C++, Linux]

Question

I am using a SocketCAN to access the CAN bus. I have successfully created pass-filters like this:

struct can_filter m_Filter;
// ... setting up m_Filters
setsockopt(m_CanSockId, SOL_CAN_RAW, CAN_RAW_FILTER, m_Filter,
           sizeof(struct can_filter));

This instructs to let CAN messages pass when meeting the filter settings.

Now I want to create a stop-filter but I do not know how to do it. For example: I wish to let all CAN messages pass except the ones with ID 0x18DAF101.

Does anybody know how to do it?

I have looked in this documentation [link](https://www.kernel.org/doc/Documentation/networking/can.txt) without finding anything to try, that's why I asked here. — robitop, Apr 12 '19 at 08:21

score 2 · Accepted Answer · answered Apr 12 '19 at 13:09

2

You have to set the bit CAN_INV_FILTER in your filter to invert the filter logic.

From the documentation behind the link you have provided:

The filter can be inverted in this semantic, when the CAN_INV_FILTER bit is set in can_id element of the can_filter structure.

answered Apr 12 '19 at 13:09

MSpiller

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thank you! I will check asap but I already trust this is what I need! – robitop Apr 12 '19 at 15:25

How to create a stop-filter (instead of a pass-filter) when reading CAN messages? [C++, Linux]

1 Answers1