Re: How to statically set J1939 addresses and names

[Kurt Van Dijck <dev.kurt@vandijck-laurijssen.be>]

On Fri, 11 Jun 2021 06:12:32 +0200, Oleksij Rempel wrote:
> Hi Rémy,
> 
> On Tue, Jun 08, 2021 at 05:27:45PM +0200, Rémy DZIEMIASZKO wrote:
> > Hello,
> > 
> > I need that my applications do not care about J1939 node addresses but
> > directly bind / connect to socket based on node name only and the
> > kernel takes care of the conversion to addresses.
> > 
> > I know this is possible if addresses are dynamically assigned through
> > the Address Claiming protocol that is implemented in the kernel. The
> > kernel keeps track of its own address and name as well as the
> > addresses and names of other ECUs on the network and convert name to
> > adresse when requested by the applications.
> > 
> > But I don't want to use the Address Claiming protocol. I want to
> > statically set all addresses and names.

It is supported to not use Address Claiming.

> > 
> > Is there a way to assign J1939 addresses and names to a CAN interface
> > without using the J1939 address claim protocol?
> 
> Current version do not have this functionality.

If you bind() your socket with only sockaddr_can.j1939.sa set to your
SA, and sockaddr_can.j1939.name to 0, makes your socket use your SA as
static address.

> 
> > I found in old j1939 kernel documentation something like
> > ip addr add dev canX j1939 0xXX
> > ip addr add dev canX j1939 name 0xXX
> > See https://www.spinics.net/lists/netdev/msg162350.html
> > 
> > But in the latest j1939 kernel documentation I do not find any
> > reference to these commands.
> 
> Yes, it was pre mainline version. For mainlining we reduced UAPI to the
> minimum to simplify reviewing, mainlining and testing process.
> 

The strict addressing was rejected because it felt much heavier than
what most CAN users were used to. Moving to the current ad-hoc
implementation allowed to drop quite some kernel code too.

> IF you need this option, you are welcome to send patches :)
> Or you can contact us or other company to implement it.
> 
> Regards,
> Oleksij
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