Classful nifconfig(8) design document / pseudocode
--------------------------------------------------
Brief: nifconfig(8) identifies device drivers via the IFT_TYPE and
ifmedia mechanisms, and determines which parser(s) for command words
to invoke accordingly.

IFT types by kernel subtree
---------------------------
<net/if_types.h> defines lots. We only use a few.

dev/em/if_em.c		IFT_ETHER (has native IFT_L2VLAN support)
dev/iicbus/if_ic.c	IFT_PARA
dev/ppbus/if_plip.c	IFT_PARA
dev/sn/if_sn.c		IFT_ETHER
netatm/atm_if.c		IFT_IPOVERATM
net/if_vlan.c		IFT_L2VLAN
net/if_arcsubr.c	IFT_ARCNET
net/if_disc.c		IFT_LOOP
net/if_ef.c		IFT_XETHER
net/if_faith.c		IFT_FAITH
net/if_fddisubr.c	IFT_FDDI
net/if_gif.c		IFT_GIF
net/if_gre.c		IFT_GRE
net/if_loop.c		IFT_LOOP
net/if_ppp.c		IFT_PPP
net/if_sl.c		IFT_SLIP
net/if_spppsubr.c	IFT_PPP
net/if_stf.c		IFT_STF
net/if_tun.c		IFT_PPP

XXX Change if_gre.c to use IFT_GRE. IFT_OTHER too ambiguous. [diff]

Interface Classes by IFT_TYPE
-----------------------------

regular cloners {
{ IFT_LOOP } => loop
{ IFT_PARA, IFT_PPP, IFT_SLIP, IFT_TUN } => ptp
{ IFT_GRE, IFT_GIF } => tunnel
{ IFT_FAITH } => faith
{ IFT_L2VLAN } => vlan
}
XXX have regular cloner semantics, subclasses may have particular semantics

special cloners {
{ IFT_STF } => stf
{ IFT_XETHER } => ethfr
}
XXX do not have regular cloner semantics

link {
{ IFT_ATM } => atm
{ IFT_FDDI } => fddi
{ IFT_ISO88025 } => tr
{ IFT_ARCNET } => arc
{ IFT_ETHER } => eth
}

-> all link-layer interfaces grok the ifmedia interface now

IFT_ETHER special cases:
 grab ift_media list; 
 if IFM_IEEE80211 mask matched
  -> treat as new class 'wlan'

Loadable Address Families
-------------------------
 inet [DEFAULT]
 inet6
 ipx
 atalk
 link
  ether
  token
  nsap 

 - Specifying an address family name assigns an address.
 - alias keyword *adds* an address to an interface.
 - delete keyword *removes* an address from an interface.
 - inet is the default address family; it is implied if no interface word
   is present.

Command line structure
----------------------

[GENERAL CASE]
ifconfig <iface> <action>
 -> if <iface> can be found, error
 -> if <iface> cannot be found...
  -> attempt to load a module if_<iface>.ko from kernel boot path
    -> if this fails, error
    -> if this succeeds... fallthrough

DEFAULT ACTION IS list; list word may be omitted.

ifconfig
 -> on its own, implies -a.
ifconfig -a
 -> display all interfaces in system
   -d all downed interfaces
   -u all upped interfaces
   -L display IPv6 address lifetime (special case..)
ifconfig -C
 -> list current cloners available (modules loaded into kernel)
ifconfig -m <iface>
 -> list supported media for <iface>
   XXX -L display IPv6 address lifetime -- this is silly for -m, depracate.
ifconfig -l
 -> list current interfaces by name on one line
   -d all downed interfaces
   -u all upped interfaces
ifconfig <iface>
 -> list <iface> AND ONLY <iface>

ifconfig <iface> <address-family> <address>
 -> if address-family is omitted, ALWAYS assume inet

ifconfig <iface> create
 -> if <iface> is a cloner, create
 -> if <iface> is not a cloner, error

ifconfig <iface> destroy
 -> if <iface> cannot be found, error
 -> if <iface> exists
  -> if <iface> is not a cloner, error
  -> if <iface> is a cloner, destroy

Per-class command words
-----------------------
[TO FOLLOW]