Re: (usagi-core 12294) Re: [PATCH] IPv6 IPsec support

["David S. Miller" <davem@redhat.com>]

   From: YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@linux-ipv6.org>
   Date: Thu, 06 Mar 2003 00:48:20 +0900 (JST)
   
   > The next large task will be to abstract out more common
   > pieces of code.  There is still quite a bit of code duplication
   > between v4 and v6 xfrm methods,
   
   Yes, we will do that.  That patch is first step for reducing 
   duplicate codes between IPv4 and IPv6.

Great.  I believe it should be possible, in the end, to make the XFRM
engine %100 address-family (v4, v6 etc.) and protocol (ah, esp)
independant.  If that goal is achieved, we may move generic parts from
net/ipv4/xfrm_*.c to net/xfrm_*.c

Note that this coincides with the idea to eventually have
an address-family independant flow cache.

Most of the address-family specific areas are:

1) DST lookup (xfrm_dst_lookup_t)

2) selector key comparisons and state lookup
   (xfrm$(AF)_selector_match, xfrm$(AF)_state_find)

3) receive processing (xfrm${AF}_rcv)

#1 is made for ipv6 by Miyazawa-san's patch.  This could logically
be extended to handle issues #2 and #3 above.

All protocol specific (ESP, AH) and address-family specific references
should go away from places like include/net/xfrm.h

I think you understand all of this, and therefore I cannot wait for the
next ipsec cleanup patch from you :)

Finally, note that eventually we will need some reference counting scheme
for to allow xfrm address-family modules to be unloaded safely.

Currently, ipv4 cannot be a module and ipv6 as a module is not able
to unload :-)  So the module unload problem does not exist right
at this moment.  So ignore this issue for now.