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

[Masao Uebayashi <uebayasi%gmail.com@localhost>]

On Tue, Nov 25, 2014 at 7:18 PM, Ryota Ozaki <ozaki-r%netbsd.org@localhost> wrote:
> 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?

For new flags, you can reuse if__pad1.

> 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?

I think adding a new member at the tail doesn't change member offsets,
so netstat(1) *should* keep working.

But for future, netstat(3) should use kvm(3), so that it keeps working
even after struct ifnet changes.