[IPV6] MIP6: Loadable module support for MIPv6.

This patch makes MIPv6 loadable module named "mip6".

Here is a modprobe.conf(5) example to load it automatically
when user application uses XFRM state for MIPv6:

alias xfrm-type-10-43 mip6
alias xfrm-type-10-60 mip6

Some MIPv6 feature is not included by this modular, however,
it should not be affected to other features like either IPsec
or IPv6 with and without the patch.
We may discuss XFRM, MH (RAW socket) and ancillary data/sockopt
separately for future work.

Loadable features:
* MH receiving check (to send ICMP error back)
* RO header parsing and building (i.e. RH2 and HAO in DSTOPTS)
* XFRM policy/state database handling for RO

These are NOT covered as loadable:
* Home Address flags and its rule on source address selection
* XFRM sub policy (depends on its own kernel option)
* XFRM functions to receive RO as IPv6 extension header
* MH sending/receiving through raw socket if user application
  opens it (since raw socket allows to do so)
* RH2 sending as ancillary data
* RH2 operation with setsockopt(2)

Signed-off-by: Masahide NAKAMURA <nakam@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 79b79f3de24c..11c0028863b0 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1034,7 +1034,7 @@ int ipv6_dev_get_saddr(struct net_device *daddr_dev,
                         }
 
                         /* Rule 4: Prefer home address */
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
                         if (hiscore.rule < 4) {
                                 if (ifa_result->flags & IFA_F_HOMEADDRESS)
                                         hiscore.attrs |= IPV6_SADDR_SCORE_HOA;
@@ -2835,7 +2835,7 @@ void if6_proc_exit(void)
 }
 #endif  /* CONFIG_PROC_FS */
 
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 /* Check if address is a home address configured on any interface. */
 int ipv6_chk_home_addr(struct in6_addr *addr)
 {