CAN Filter

[karlkobel]

I apologize for using this communication path, but I don't feel comfortable doing a pull request.
I am using libj1939 a in an application and I am using filters. I ran into a problem and found a solution. It may be appropriate to include this solution in the library. The method in question is j1939_filter in linux_socketcan.c.

int j1939_filter(struct j1939_pgn_filter *filter, uint32_t num_filters)
{
struct can_filter rfilter[num_filters];
uint32_t id;

for (size_t i = 0; i < num_filters; i++) {
	id = j1939_pgn2id(filter[i].pgn, filter[i].priority, filter[i].addr);

    // all of the network messages have the CAN_EFF_FLAG bit cleared, so I don't
    // understand why this is set here. The mask is zero, so this bit wouldn't
    // be considered in the filter anyway
	rfilter[i].can_id = id | CAN_EFF_FLAG;
    
    // the filter mask didn't line up with the ID so I used the pgn2id macro to align it
    // I didn't know what to do with the polarity bit, so I left it at 0
    // I did not need to filter on the polarity
	// original code - rfilter[i].can_mask = filter[i].pgn_mask;
    rfilter[i].can_mask = j1939_pgn2id(filter[i].pgn_mask, 0, filter[i].addr_mask);

    // test code to verify the id and mask
	//printf("ID: %08x, Mask: %08x\n", rfilter[i].can_id, rfilter[i].can_mask);
}
setsockopt(cansock, SOL_CAN_RAW, CAN_RAW_FILTER, &rfilter, sizeof(rfilter));

return 0;

}

Thanks for your consideration.

Karl Kobel

BTW - we have a slight connection - I work for Wabtec (albeit in the bus division). I know we have done work for Alstom.

[email protected]