HEAD UP: non-MPSAFE network drivers to be disabled (was: 8.0 network stack MPsafety goals (fwd))

[Robert Watson]

On Tue, 27 May 2008, Poul-Henning Kamp wrote:

> In message <20080527062736.GF64397 at hoeg.nl>, Ed Schouten writes:
>
>>>> The new TTY layer should still support line disciplines, [...]
>>>
>>> Actually...  I think it shouldn't.
>>
>> With the word `should' I meant that it would still be possible to implement 
>> multiple line disciplines with the mpsafetty code. But I really think line 
>> disciplines should go.
>
> No, don't bother.  Remove the entire "abstraction" of linedisciplines.
>
>> What should happen with the NETGRAPHDISC?
>
> It should be done in userland if it is necessary at all.

It sounds like there is some disagreement on this point, given that that would 
require byte streams from serial lines to go into userspace just to be 
re-injected into the kernel in order to enter netgraph.  Rather than do that, 
a more sensible route would be to look at converting ng_tty from a line 
discipline into a much more constrained set of I/O hooks, selected using the 
same ioctl but presumably a different discipline name.  Unfortunately, it's 
not clear that snp would use the same hooks, as Netgraph presumably wants to 
eat the input, whereas snp just wants a copy, but perhaps there's a clean way 
to capture that distinction.

Robert N M Watson
Computer Laboratory
University of Cambridge