BSD network memory allocation bug

[eric at cls.usask.ca (Eric Norum)]

Quality Quorum wrote:

> I do not bleive that RTOS has to follow same logic UNIX in the case:
> 
>     1. Work load of RTOS stuff is more predictale so in many
>        cases there is enough information to figure out
>        necessary size of mbuf free list.
> 
>     2. All IP based protocols will recover from packet loss
>        without too many problems.
> 
>     3. Memory is cheap.
> 
> So, the most natuarl thing is to have pool of mbuffs and return
> NULL in all cases (WAIT and NO_WAIT) when it is exhausted.
> 

But this is exactly what cant *not* be done.  The FreeBSD code (and many RTEMS network drivers) assume that a valid pointer will be returned in response to an M_WAIT mbuf request.  I propose to make that assumption valid when I rewrite m_mballoc and m_clalloc.  My previous posting was just asking for confirmation that the FreeBSD code did, indeed, have a bug.

-- 
Eric Norum                                 eric at cls.usask.ca
Saskatchewan Accelerator Laboratory        Phone: (306) 966-6308
University of Saskatchewan                 FAX:   (306) 966-6058
Saskatoon, Canada.