[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, 10 insertions, 9 deletions

diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 14be0b9b77a5..173a4bb52255 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -42,7 +42,7 @@
 #include <net/ndisc.h>
 #include <net/ip6_route.h>
 #include <net/addrconf.h>
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 #include <net/xfrm.h>
 #endif
 
@@ -90,6 +90,7 @@ int ipv6_find_tlv(struct sk_buff *skb, int offset, int type)
  bad:
         return -1;
 }
+EXPORT_SYMBOL_GPL(ipv6_find_tlv);
 
 /*
  *      Parsing tlv encoded headers.
@@ -196,7 +197,7 @@ bad:
   Destination options header.
  *****************************/
 
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 static int ipv6_dest_hao(struct sk_buff **skbp, int optoff)
 {
         struct sk_buff *skb = *skbp;
@@ -270,7 +271,7 @@ static int ipv6_dest_hao(struct sk_buff **skbp, int optoff)
 #endif
 
 static struct tlvtype_proc tlvprocdestopt_lst[] = {
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
         {
                 .type   = IPV6_TLV_HAO,
                 .func   = ipv6_dest_hao,
@@ -283,7 +284,7 @@ static int ipv6_destopt_rcv(struct sk_buff **skbp)
 {
         struct sk_buff *skb = *skbp;
         struct inet6_skb_parm *opt = IP6CB(skb);
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
         __u16 dstbuf;
 #endif
         struct dst_entry *dst;
@@ -298,7 +299,7 @@ static int ipv6_destopt_rcv(struct sk_buff **skbp)
         }
 
         opt->lastopt = opt->dst1 = skb_network_header_len(skb);
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
         dstbuf = opt->dst1;
 #endif
 
@@ -308,7 +309,7 @@ static int ipv6_destopt_rcv(struct sk_buff **skbp)
                 skb = *skbp;
                 skb->transport_header += (skb_transport_header(skb)[1] + 1) << 3;
                 opt = IP6CB(skb);
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
                 opt->nhoff = dstbuf;
 #else
                 opt->nhoff = opt->dst1;
@@ -427,7 +428,7 @@ static int ipv6_rthdr_rcv(struct sk_buff **skbp)
 looped_back:
         if (hdr->segments_left == 0) {
                 switch (hdr->type) {
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
                 case IPV6_SRCRT_TYPE_2:
                         /* Silently discard type 2 header unless it was
                          * processed by own
@@ -463,7 +464,7 @@ looped_back:
                         return -1;
                 }
                 break;
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
         case IPV6_SRCRT_TYPE_2:
                 /* Silently discard invalid RTH type 2 */
                 if (hdr->hdrlen != 2 || hdr->segments_left != 1) {
@@ -520,7 +521,7 @@ looped_back:
         addr += i - 1;
 
         switch (hdr->type) {
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
         case IPV6_SRCRT_TYPE_2:
                 if (xfrm6_input_addr(skb, (xfrm_address_t *)addr,
                                      (xfrm_address_t *)&ipv6_hdr(skb)->saddr,