[IPV6] MIP6: Add inbound interface of home address option.

Add inbound function of home address option by registering it to TLV
table for destination options header.

Based on MIPL2 kernel patch.

This patch was also written by: Ville Nuorvala <vnuorval@tcs.hut.fi>

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

include/linux/ipv6.h

@@ -226,6 +226,9 @@ struct inet6_skb_parm {
 	__u16			dst0;
 	__u16			srcrt;
 	__u16			dst1;
+#ifdef CONFIG_IPV6_MIP6
+	__u16			dsthao;
+#endif
 	__u16			lastopt;
 	__u32			nhoff;
 	__u16			flags;

net/ipv6/exthdrs.c

@@ -196,8 +196,80 @@ bad:
   Destination options header.
  *****************************/
 
+#ifdef CONFIG_IPV6_MIP6
+static int ipv6_dest_hao(struct sk_buff **skbp, int optoff)
+{
+	struct sk_buff *skb = *skbp;
+	struct ipv6_destopt_hao *hao;
+	struct inet6_skb_parm *opt = IP6CB(skb);
+	struct ipv6hdr *ipv6h = (struct ipv6hdr *)skb->nh.raw;
+	struct in6_addr tmp_addr;
+	int ret;
+
+	if (opt->dsthao) {
+		LIMIT_NETDEBUG(KERN_DEBUG "hao duplicated\n");
+		goto discard;
+	}
+	opt->dsthao = opt->dst1;
+	opt->dst1 = 0;
+
+	hao = (struct ipv6_destopt_hao *)(skb->nh.raw + optoff);
+
+	if (hao->length != 16) {
+		LIMIT_NETDEBUG(
+			KERN_DEBUG "hao invalid option length = %d\n", hao->length);
+		goto discard;
+	}
+
+	if (!(ipv6_addr_type(&hao->addr) & IPV6_ADDR_UNICAST)) {
+		LIMIT_NETDEBUG(
+			KERN_DEBUG "hao is not an unicast addr: " NIP6_FMT "\n", NIP6(hao->addr));
+		goto discard;
+	}
+
+	ret = xfrm6_input_addr(skb, (xfrm_address_t *)&ipv6h->daddr,
+			       (xfrm_address_t *)&hao->addr, IPPROTO_DSTOPTS);
+	if (unlikely(ret < 0))
+		goto discard;
+
+	if (skb_cloned(skb)) {
+		struct sk_buff *skb2 = skb_copy(skb, GFP_ATOMIC);
+		if (skb2 == NULL)
+			goto discard;
+
+		kfree_skb(skb);
+
+		/* update all variable using below by copied skbuff */
+		*skbp = skb = skb2;
+		hao = (struct ipv6_destopt_hao *)(skb2->nh.raw + optoff);
+		ipv6h = (struct ipv6hdr *)skb2->nh.raw;
+	}
+
+	if (skb->ip_summed == CHECKSUM_COMPLETE)
+		skb->ip_summed = CHECKSUM_NONE;
+
+	ipv6_addr_copy(&tmp_addr, &ipv6h->saddr);
+	ipv6_addr_copy(&ipv6h->saddr, &hao->addr);
+	ipv6_addr_copy(&hao->addr, &tmp_addr);
+
+	if (skb->tstamp.off_sec == 0)
+		__net_timestamp(skb);
+
+	return 1;
+
+ discard:
+	kfree_skb(skb);
+	return 0;
+}
+#endif
+
 static struct tlvtype_proc tlvprocdestopt_lst[] = {
-	/* No destination options are defined now */
+#ifdef CONFIG_IPV6_MIP6
+	{
+		.type	= IPV6_TLV_HAO,
+		.func	= ipv6_dest_hao,
+	},
+#endif
 	{-1,			NULL}
 };
 
@@ -205,6 +277,9 @@ 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
+	__u16 dstbuf;
+#endif
 
 	if (!pskb_may_pull(skb, (skb->h.raw-skb->data)+8) ||
 	    !pskb_may_pull(skb, (skb->h.raw-skb->data)+((skb->h.raw[1]+1)<<3))) {
@@ -215,11 +290,18 @@ static int ipv6_destopt_rcv(struct sk_buff **skbp)
 
 	opt->lastopt = skb->h.raw - skb->nh.raw;
 	opt->dst1 = skb->h.raw - skb->nh.raw;
+#ifdef CONFIG_IPV6_MIP6
+	dstbuf = opt->dst1;
+#endif
 
 	if (ip6_parse_tlv(tlvprocdestopt_lst, skbp)) {
 		skb = *skbp;
 		skb->h.raw += ((skb->h.raw[1]+1)<<3);
+#ifdef CONFIG_IPV6_MIP6
+		opt->nhoff = dstbuf;
+#else
 		opt->nhoff = opt->dst1;
+#endif
 		return 1;
 	}