On Wed, Nov 26, 2014 at 12:29 AM, Ryota Ozaki <ozak...@netbsd.org> wrote: > Yes, we can extend if_flags to int by unifying with if__pad1, and it works > for the kernel and for old userland programs on little endian machines. > However, it doesn't work for old userland programs on big endian machines, > IIUC. An old userland program, say netstat, which uses kvm(3) reads > if_flags as short. On a LE machine, netstat can see lower-half of if_flags > (int) of a new kernel as expected. OTOH, on a BE machine, netstat sees > upper-half of the value.
I'd change if__pad1 to if_flags2 and define IFF2_SLOWTIMO_MPSAFE etc. >>> 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. > > Hmm, I fail to understand what you mean. netstat should use kvm? or > shouldn't use? Sorry, I meant s/kvm(3)/sysctl(3)/...
