[IPV6] NDISC: update neighbor cache entry by RS.

Signed-off-by: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>

include/net/ndisc.h

@@ -45,6 +45,11 @@ struct nd_msg {
 	__u8		opt[0];
 };
 
+struct rs_msg {
+	struct icmp6hdr	icmph;
+	__u8		opt[0];
+};
+
 struct ra_msg {
         struct icmp6hdr		icmph;
 	__u32			reachable_time;

net/ipv6/ndisc.c

@@ -921,6 +921,64 @@ static void ndisc_recv_na(struct sk_buff *skb)
 	}
 }
 
+static void ndisc_recv_rs(struct sk_buff *skb)
+{
+	struct rs_msg *rs_msg = (struct rs_msg *) skb->h.raw;
+	unsigned long ndoptlen = skb->len - sizeof(*rs_msg);
+	struct neighbour *neigh;
+	struct inet6_dev *idev;
+	struct in6_addr *saddr = &skb->nh.ipv6h->saddr;
+	struct ndisc_options ndopts;
+	u8 *lladdr = NULL;
+	int lladdrlen = 0;
+
+	if (skb->len < sizeof(*rs_msg))
+		return;
+
+	idev = in6_dev_get(skb->dev);
+	if (!idev) {
+		if (net_ratelimit())
+			ND_PRINTK1("ICMP6 RS: can't find in6 device\n");
+		return;
+	}
+
+	/* Don't accept RS if we're not in router mode */
+	if (!idev->cnf.forwarding || idev->cnf.accept_ra)
+		goto out;
+
+	/*
+	 * Don't update NCE if src = ::;
+	 * this implies that the source node has no ip address assigned yet.
+	 */
+	if (ipv6_addr_any(saddr))
+		goto out;
+
+	/* Parse ND options */
+	if (!ndisc_parse_options(rs_msg->opt, ndoptlen, &ndopts)) {
+		if (net_ratelimit())
+			ND_PRINTK2("ICMP6 NS: invalid ND option, ignored\n");
+		goto out;
+	}
+
+	if (ndopts.nd_opts_src_lladdr) {
+		lladdr = (u8 *)(ndopts.nd_opts_src_lladdr + 1);
+		lladdrlen = ndopts.nd_opts_src_lladdr->nd_opt_len << 3;
+		if (lladdrlen != NDISC_OPT_SPACE(skb->dev->addr_len))
+			goto out;
+	}
+
+	neigh = __neigh_lookup(&nd_tbl, saddr, skb->dev, 1);
+	if (neigh) {
+		neigh_update(neigh, lladdr, NUD_STALE,
+			     NEIGH_UPDATE_F_WEAK_OVERRIDE|
+			     NEIGH_UPDATE_F_OVERRIDE|
+			     NEIGH_UPDATE_F_OVERRIDE_ISROUTER);
+		neigh_release(neigh);
+	}
+out:
+	in6_dev_put(idev);
+}
+
 static void ndisc_router_discovery(struct sk_buff *skb)
 {
         struct ra_msg *ra_msg = (struct ra_msg *) skb->h.raw;
@@ -1395,6 +1453,10 @@ int ndisc_rcv(struct sk_buff *skb)
 		ndisc_recv_na(skb);
 		break;
 
+	case NDISC_ROUTER_SOLICITATION:
+		ndisc_recv_rs(skb);
+		break;
+
 	case NDISC_ROUTER_ADVERTISEMENT:
 		ndisc_router_discovery(skb);
 		break;