Subject: Re: Linux 2.6.35/TIPC 2.0 ABI breaking changes

From: Leandro Lucarella <[email-masked]>
Date: Wed, 20 Oct 2010 15:24:11 -0300

Jon Maloy, el 20 de octubre a las 13:57 me escribiste:
> > Another option is to change the TIPC 2.0 specification to use 
> > the old format (use HBO in subscriptions and keep 
> > TIPC_SUB_SERVICE as a separate flag with value 2) and forget 
> > about all this. After all, I can't see what advantages gives 
> > having to change the BO for internal messages between the 
> > applications and the stack.
> 
> I agree with this. I have no problems with changing the draft 
> (which as Leandro already noted is "work-in-progress") to specify that 
> both HBO and NBO are permitted over the wire, and that it is the
> topology server's task to keep track of which one is used.

Just to try to understand better how things works, or are supposed to
work: do the subscription and event messages (and I mean the struct
tipc_subscr and tipc_event published in tipc.h) really go over the wire
or are only used to communicate the stack to the application inside
a node?

I think this is a crucial matter, since it defines if the changes cross
kernel/userspace boundaries only or it also crosses the kernel/network
boundaries.

> Remember, permitting both is a superset of the current one (NBO only)
> so it is fully backwards compatible. We break absolutly nothing by
> permitting this.

I think if they really go through the wire, it should be in NBO, and if
tipc_subscr and tipc_event are used only internally, we can still fix
the userspace messages when sending them through the wire.

In any case, I agree that the patches should be reverted and a solution
should be planned with more time and consensus.

Thanks.

-- 
Leandro Lucarella (AKA luca)                     http://llucax.com.ar/
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