follows BSD/OS practice and ucd-snmp code (FreeBSD does it for specific
interfaces only).
was: if_lastchange get updated on every packet transmission/receipt.
now: if_lastchange get updated when IFF_UP is changed.
This now provides slightly more functionality than the FreeBSD layer1-newbus
interface. It was meant to be a simple change to one header and a few
c files, but the change rippled all through various stuff.
To prevent a change to the kernel<->userland interface right now the kernel
is now lying about card types to userland (but who cares). This will be fixed
when the userland interface changes, after layer 3 <-> layer 4 has been
fixed.
Functional changes:
Provide a clean interface for hardware drivers to attach to the upper
layers. This will need another small change in the B-channel handling
when a similar change to the layer 3 <-> layer 4 interface happens.
Avoid passing indices into global arrays of pointers around, instead pass
the pointers itself. Don't code hardware driver types by predefined magic
numbers (think LKM). Prepare for detachable drivers (think pcmcia).
While there remove some sets of function pointers always pointing to the
same function (meant to be the configurable set of D channel protocol
handlers). It is unlikely another supported D-channel protocol will fit into
that (maximal layer interface) abstraction. When we get support for another
protocol, we will need to come up with a workable interface. Besides, the
old implementation was, uhm, strange.
the link level name for the interface (ifp->if_sadl) is allocated
before ifp->if_addrlen is initialized, which could lead to allocating
too little space for the link level address.
Do this by splitting allocation of the link level name out of
if_attach() and into if_alloc_sadl(), which is normally called
by functions like ether_ifattach(). Network interfaces which
don't have a link-specific attach routine must call if_alloc_sadl()
themselves (example: gif).
Link level names are freed by if_free_sadl(), which can be called
from e.g. ether_ifdetach(). Drivers never need call if_free_sadl()
themselves as if_detach() will do it if it is not already done.
While here, add the ability to pass an AF_LINK address to
SIOCSIFADDR in ether_ioctl() (this is what caused me to notice
the problem that the above fixes).
itojun