re: struct ifnet and ifaddr handling [was: Re: Making global variables of if.c MPSAFE]

[matthew green <mrg%eterna.com.au@localhost>]

> > Good point.  There must be a way for drivers to declare if
> > CALLOUT_MPSAFE or not.  Need to extend if_flags.
> 
> Hmm, if_flags.
> 
> http://mail-index.netbsd.org/tech-net/2009/01/27/msg000985.html
> 
> Do we have to care about kvm(3) users (i.e., netstat) as well as
> the callout_t issue?
[ .. ]
> > Yes, netstat(1) uses sysctl(3) to fetch statistics numbers.  But
> > netstat(1) needs to know struct type information (by building if.c) to
> > read kernel cores via kvm(3).  Maybe making kvm(3) to understand DWARF
> > type information helps?
> 
> I don't understand how kvm(3) works though, if we don't change existing
> members of struct ifnet, can old netstat(1) run on a new kernel that
> adds a value hidden in _KERNEL to struct ifnet?

you don't have to worry about making old kvm users work on new
kernels.  that has never been a useful goal, and why we have
switched most run-time usage to sysctl().  the real benefit of
kvm programs is running against a core file.  if crash(8) was
extended to handle these cases, or perhaps some gdb scripts,
then we could obsolete the kvm usage entirely.  (of course,
netstat still has a non trivial amount of sysctl work to go,
at least last time i looked.)

thanks.


.mrg.