from the existing modevent / MOD_UNLOAD handler, and register div_destroy()
in protosw as per-vnet .pr_destroy() handler for options VIMAGE builds. In
nooptions VIMAGE builds, div_destroy() will be invoked from the modevent
handler, resulting in effectively identical operation as it was prior this
change. div_destroy() also tears down hashtables used by ipdivert, which
were previously left behind on ipdivert kldunloads.
For options VIMAGE builds only, temporarily disable kldunloading of ipdivert,
because without introducing additional locking logic it is impossible to
atomically check whether all ipdivert instances in all vnets are idle, and
proceed with cleanup without opening a race window for a vnet to open an
ipdivert socket while ipdivert tear-down is in progress.
While here, staticize div_init(), because it is not used outside of
ip_divert.c.
In cooperation with: julian
Approved by: re (rwatson), julian (mentor)
MFC after: 3 days
of protocols. The call to divert_packet() is done through a function pointer. All
semantics of IPDIVERT remain intact. If IPDIVERT is not loaded ipfw will refuse to
install divert rules and natd will complain about 'protocol not supported'. Once
it is loaded both will work and accept rules and open the divert socket. The module
can only be unloaded if no divert sockets are open. It does not close any divert
sockets when an unload is requested but will return EBUSY instead.
them mostly with packet tags (one case is handled by using an mbuf flag
since the linkage between "caller" and "callee" is direct and there's no
need to incur the overhead of a packet tag).
This is (mostly) work from: sam
Silence from: -arch
Approved by: bms(mentor), sam, rwatson
