Re: [PATCH can-next v3 0/3] Introduce diag support for CAN

[Filippo Storniolo <fstornio@redhat.com>]

On Tue, Oct 20, 2026 at 06:20:22PM +0200, Oliver Hartkopp wrote:
>
>
>On 20.10.26 17:50, Marc Kleine-Budde wrote:
>>On 04.09.2026 16:12:54, Filippo Storniolo wrote:
>>>An example of the output given by ss -cpe:
>>>
>>>Netid                     Recv-Q                 Send-Q                                 Local Address:Port                                   Peer Address:Port                 Process
>>>CAN_ISOTP                 0                      0                                              vcan1:1110                                          vcan1:291                   uid:1001 ino:50324 sk:0 users:(("can2",pid=9210,fd=4))
>>>CAN_ISOTP                 0                      0                                              vcan1:291                                           vcan1:1110                  uid:1001 ino:50323 sk:0 users:(("can2",pid=9210,fd=3))
>

Hi Oliver

>The fact that the inode number of the socket is visible fits great to 
>the upcoming CAN procfs output:
>
>https://lore.kernel.org/linux-can/20261018164417.1540449-8-mkl@pengutronix.de/
>
>But I'm not sure about "Local Address:Port" being "vcan1:1110".
>

You are right and probably the example in the cover letter does not
fit the best use for the netlink message.

This is just how ss show numbers. I used this tool as proof of
concept during development and I didn't put too much effort on it.

>A CAN-ID together with a CAN interface is a unique "content address" 
>to identify the content which is in the CAN frames data.
>
>I assume "1110" to be the decimal representation of an 11 bit SFF CAN 
>ID 0x456, right?

Yes, it comes from 0x456. During development, I was using some C
program to just create CAN sockets. The socket configuration for the
shown example was the following:

`
addr_send.can_family = addr_recv.can_family = AF_CAN;
addr_send.can_ifindex = addr_recv.can_ifindex = if_nametoindex("vcan1");
addr_send.can_addr.tp.tx_id = addr_recv.can_addr.tp.rx_id = 0x123;
addr_send.can_addr.tp.rx_id = addr_recv.can_addr.tp.tx_id = 0x456;
`

>
>Having a CAN ID in decimal representation is generally unusual - 
>especially in Linux. Additionally you can have 29 bit EFF CAN IDs 
>which does not fit into a 16 bit port value.
>
>And 29 bit IDs have to be marked as you can have the value 0x456 in 11 
>bit and 29 bit CAN IDs. We usually do this with 456 and 00000456 to 
>indicate 11/29 bit IDs.
>
>So the "Local Address:Port" output does not really fit to CAN here ...
>

I can update the ss example in the cover letter with something
that better fits a real case scenario if you want. 

>Best regards,
>Oliver

Best regards,
Filippo
>
>