[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 <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/linux/ipv6.h

···
 	__u16			lastopt;
 	__u32			nhoff;
 	__u16			flags;
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 	__u16			dsthao;
 #endif
 

include/net/addrconf.h

···
 extern int			ipv6_chk_addr(struct in6_addr *addr,
 					      struct net_device *dev,
 					      int strict);
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 extern int			ipv6_chk_home_addr(struct in6_addr *addr);
 #endif
 extern struct inet6_ifaddr *	ipv6_get_ifaddr(struct in6_addr *addr,

include/net/mip6.h

···
 #define IP6_MH_TYPE_BERROR	7   /* Binding Error */
 #define IP6_MH_TYPE_MAX		IP6_MH_TYPE_BERROR
 
-extern int mip6_init(void);
-extern void mip6_fini(void);
-extern int mip6_mh_filter(struct sock *sk, struct sk_buff *skb);
-
 #endif

include/net/rawv6.h

···
 
 #ifdef __KERNEL__
 
+#include <net/protocol.h>
+
 #define RAWV6_HTABLE_SIZE	MAX_INET_PROTOS
 extern struct hlist_head raw_v6_htable[RAWV6_HTABLE_SIZE];
 extern rwlock_t raw_v6_lock;
···
 					  struct inet6_skb_parm *opt,
 					  int type, int code, 
 					  int offset, __be32 info);
+
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
+int rawv6_mh_filter_register(int (*filter)(struct sock *sock,
+					   struct sk_buff *skb));
+int rawv6_mh_filter_unregister(int (*filter)(struct sock *sock,
+					     struct sk_buff *skb));
+#endif
 
 #endif
 

net/ipv6/Kconfig

···
 	  If unsure, say Y.
 
 config IPV6_MIP6
-	bool "IPv6: Mobility (EXPERIMENTAL)"
+	tristate "IPv6: Mobility (EXPERIMENTAL)"
 	depends on IPV6 && EXPERIMENTAL
 	select XFRM
 	---help---

net/ipv6/Makefile

···
 	xfrm6_output.o
 ipv6-$(CONFIG_NETFILTER) += netfilter.o
 ipv6-$(CONFIG_IPV6_MULTIPLE_TABLES) += fib6_rules.o
-ipv6-$(CONFIG_IPV6_MIP6) += mip6.o
 ipv6-$(CONFIG_PROC_FS) += proc.o
 
 ipv6-objs += $(ipv6-y)
···
 obj-$(CONFIG_INET6_XFRM_MODE_TUNNEL) += xfrm6_mode_tunnel.o
 obj-$(CONFIG_INET6_XFRM_MODE_ROUTEOPTIMIZATION) += xfrm6_mode_ro.o
 obj-$(CONFIG_INET6_XFRM_MODE_BEET) += xfrm6_mode_beet.o
+obj-$(CONFIG_IPV6_MIP6) += mip6.o
 obj-$(CONFIG_NETFILTER)	+= netfilter/
 
 obj-$(CONFIG_IPV6_SIT) += sit.o

net/ipv6/addrconf.c

···
 			}
 
 			/* 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;
···
 }
 #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)
 {

net/ipv6/af_inet6.c

···
 #ifdef CONFIG_IPV6_TUNNEL
 #include <net/ip6_tunnel.h>
 #endif
-#ifdef CONFIG_IPV6_MIP6
-#include <net/mip6.h>
-#endif
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
···
 	ipv6_frag_init();
 	ipv6_nodata_init();
 	ipv6_destopt_init();
-#ifdef CONFIG_IPV6_MIP6
-	mip6_init();
-#endif
 
 	/* Init v6 transport protocols. */
 	udpv6_init();
···
 
 	/* Cleanup code parts. */
 	ipv6_packet_cleanup();
-#ifdef CONFIG_IPV6_MIP6
-	mip6_fini();
-#endif
+
 	addrconf_cleanup();
 	ip6_flowlabel_cleanup();
 	ip6_route_cleanup();

net/ipv6/ah6.c

···
 	return 0;
 }
 
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 /**
  *	ipv6_rearrange_destopt - rearrange IPv6 destination options header
  *	@iph: IPv6 header
···
 	u8 nexthdr;
 	char tmp_base[8];
 	struct {
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 		struct in6_addr saddr;
 #endif
 		struct in6_addr daddr;
···
 			err = -ENOMEM;
 			goto error;
 		}
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 		memcpy(tmp_ext, &top_iph->saddr, extlen);
 #else
 		memcpy(tmp_ext, &top_iph->daddr, extlen);
···
 
 	memcpy(top_iph, tmp_base, sizeof(tmp_base));
 	if (tmp_ext) {
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 		memcpy(&top_iph->saddr, tmp_ext, extlen);
 #else
 		memcpy(&top_iph->daddr, tmp_ext, extlen);

net/ipv6/datagram.c

···
 
 			switch (rthdr->type) {
 			case IPV6_SRCRT_TYPE_0:
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 			case IPV6_SRCRT_TYPE_2:
 #endif
 				break;

net/ipv6/exthdrs.c

···
 #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
 
···
  bad:
 	return -1;
 }
+EXPORT_SYMBOL_GPL(ipv6_find_tlv);
 
 /*
  *	Parsing tlv encoded headers.
···
   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;
···
 #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,
···
 {
 	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;
···
 	}
 
 	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
 
···
 		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;
···
 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
···
 			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) {
···
 	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,

net/ipv6/icmp.c

···
 	return 0;
 }
 
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 static void mip6_addr_swap(struct sk_buff *skb)
 {
 	struct ipv6hdr *iph = ipv6_hdr(skb);

net/ipv6/ip6_output.c

···
 			found_rhdr = 1;
 			break;
 		case NEXTHDR_DEST:
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 			if (ipv6_find_tlv(skb, offset, IPV6_TLV_HAO) >= 0)
 				break;
 #endif

net/ipv6/ipv6_sockglue.c

···
 			struct ipv6_rt_hdr *rthdr = opt->srcrt;
 			switch (rthdr->type) {
 			case IPV6_SRCRT_TYPE_0:
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 			case IPV6_SRCRT_TYPE_2:
 #endif
 				break;

net/ipv6/mip6.c

···
 #include <net/sock.h>
 #include <net/ipv6.h>
 #include <net/ip6_checksum.h>
+#include <net/rawv6.h>
 #include <net/xfrm.h>
 #include <net/mip6.h>
 
···
 	return len;
 }
 
-int mip6_mh_filter(struct sock *sk, struct sk_buff *skb)
+static int mip6_mh_filter(struct sock *sk, struct sk_buff *skb)
 {
 	struct ip6_mh *mh;
 
···
 	.remote_addr	= mip6_xfrm_addr,
 };
 
-int __init mip6_init(void)
+static int __init mip6_init(void)
 {
 	printk(KERN_INFO "Mobile IPv6\n");
 
···
 		printk(KERN_INFO "%s: can't add xfrm type(rthdr)\n", __FUNCTION__);
 		goto mip6_rthdr_xfrm_fail;
 	}
+	if (rawv6_mh_filter_register(mip6_mh_filter) < 0) {
+		printk(KERN_INFO "%s: can't add rawv6 mh filter\n", __FUNCTION__);
+		goto mip6_rawv6_mh_fail;
+	}
+
+
 	return 0;
 
+ mip6_rawv6_mh_fail:
+	xfrm_unregister_type(&mip6_rthdr_type, AF_INET6);
  mip6_rthdr_xfrm_fail:
 	xfrm_unregister_type(&mip6_destopt_type, AF_INET6);
  mip6_destopt_xfrm_fail:
 	return -EAGAIN;
 }
 
-void __exit mip6_fini(void)
+static void __exit mip6_fini(void)
 {
+	if (rawv6_mh_filter_unregister(mip6_mh_filter) < 0)
+		printk(KERN_INFO "%s: can't remove rawv6 mh filter\n", __FUNCTION__);
 	if (xfrm_unregister_type(&mip6_rthdr_type, AF_INET6) < 0)
 		printk(KERN_INFO "%s: can't remove xfrm type(rthdr)\n", __FUNCTION__);
 	if (xfrm_unregister_type(&mip6_destopt_type, AF_INET6) < 0)
 		printk(KERN_INFO "%s: can't remove xfrm type(destopt)\n", __FUNCTION__);
 }
+
+module_init(mip6_init);
+module_exit(mip6_fini);
+
+MODULE_LICENSE("GPL");

net/ipv6/raw.c

···
 #include <net/udp.h>
 #include <net/inet_common.h>
 #include <net/tcp_states.h>
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 #include <net/mip6.h>
 #endif
 
···
 	return 0;
 }
 
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
+static int (*mh_filter)(struct sock *sock, struct sk_buff *skb);
+
+int rawv6_mh_filter_register(int (*filter)(struct sock *sock,
+					   struct sk_buff *skb))
+{
+	rcu_assign_pointer(mh_filter, filter);
+	return 0;
+}
+EXPORT_SYMBOL(rawv6_mh_filter_register);
+
+int rawv6_mh_filter_unregister(int (*filter)(struct sock *sock,
+					     struct sk_buff *skb))
+{
+	rcu_assign_pointer(mh_filter, NULL);
+	synchronize_rcu();
+	return 0;
+}
+EXPORT_SYMBOL(rawv6_mh_filter_unregister);
+
+#endif
+
 /*
  *	demultiplex raw sockets.
  *	(should consider queueing the skb in the sock receive_queue
···
 		case IPPROTO_ICMPV6:
 			filtered = icmpv6_filter(sk, skb);
 			break;
-#ifdef CONFIG_IPV6_MIP6
+
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 		case IPPROTO_MH:
+		{
 			/* XXX: To validate MH only once for each packet,
 			 * this is placed here. It should be after checking
 			 * xfrm policy, however it doesn't. The checking xfrm
 			 * policy is placed in rawv6_rcv() because it is
 			 * required for each socket.
 			 */
-			filtered = mip6_mh_filter(sk, skb);
+			int (*filter)(struct sock *sock, struct sk_buff *skb);
+
+			filter = rcu_dereference(mh_filter);
+			filtered = filter ? filter(sk, skb) : 0;
 			break;
+		}
 #endif
 		default:
 			filtered = 0;

net/ipv6/xfrm6_policy.c

···
 #include <net/ip.h>
 #include <net/ipv6.h>
 #include <net/ip6_route.h>
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 #include <net/mip6.h>
 #endif
 
···
 			fl->proto = nexthdr;
 			return;
 
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 		case IPPROTO_MH:
 			if (pskb_may_pull(skb, nh + offset + 3 - skb->data)) {
 				struct ip6_mh *mh;

net/ipv6/xfrm6_state.c

···
 		goto end;
 
 	/* Rule 2: select MIPv6 RO or inbound trigger */
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 	for (i = 0; i < n; i++) {
 		if (src[i] &&
 		    (src[i]->props.mode == XFRM_MODE_ROUTEOPTIMIZATION ||
···
 		goto end;
 
 	/* Rule 2: select MIPv6 RO or inbound trigger */
-#ifdef CONFIG_IPV6_MIP6
+#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
 	for (i = 0; i < n; i++) {
 		if (src[i] &&
 		    (src[i]->mode == XFRM_MODE_ROUTEOPTIMIZATION ||