Re: behavior of NO SENDERS notifications when receive rights move

[Brent W. Baccala]

On Fri, Sep 30, 2016 at 9:17 AM, Kalle Olavi Niemitalo <kon@iki.fi> wrote:

A future version of rpctrace might want to move receive rights
if it were able to attach to a preexisting task.

That's an important and interesting application that I hadn't thought of.

Now I'm wondering - how would DEAD NAME notifications be handled?  rpctrace would want to transfer send rights with the DN notifications attached (so it could wrap them both), but my experience, and my understanding of the Mach documentation, is that moving a send right with a DN request triggers a PORT DELETED notification, which is not what we would want.

Right now, I can't think of any way to circumvent the problem with the current Mach API.  We could copy the send rights instead of moving them, which would avoid triggering the notification, but then how would we interpose rpctrace?  We could swap the ports all around with the target task halted, and I'm not sure what would happen then.

We'd probably have to modify the kernel to allow rpctrace to transparently attach like that.

    agape

    brent