[IPV6] ADDRCONF: Optimistic Duplicate Address Detection (RFC 4429) Support.

Nominally an autoconfigured IPv6 address is added to an interface in the
Tentative state (as per RFC 2462).  Addresses in this state remain in this
state while the Duplicate Address Detection process operates on them to
determine their uniqueness on the network.  During this period, these
tentative addresses may not be used for communication, increasing the time
before a node may be able to communicate on a network.  Using Optimistic
Duplicate Address Detection, autoconfigured addresses may be used
immediately for communication on the network, as long as certain rules are
followed to avoid conflicts with other nodes during the Duplicate Address
Detection process.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 61 insertions, 23 deletions

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 886c5be..b79b000 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -449,6 +449,8 @@ static void ndisc_send_na(struct net_device *dev, struct neighbour *neigh,
 	ifp = ipv6_get_ifaddr(solicited_addr, dev, 1);
 	if (ifp) {
 		src_addr = solicited_addr;
+		if (ifp->flags & IFA_F_OPTIMISTIC)
+			override = 0;
 		in6_ifa_put(ifp);
 	} else {
 		if (ipv6_dev_get_saddr(dev, daddr, &tmpaddr))
@@ -544,7 +546,8 @@ void ndisc_send_ns(struct net_device *dev, struct neighbour *neigh,
 	int send_llinfo;
 
 	if (saddr == NULL) {
-		if (ipv6_get_lladdr(dev, &addr_buf))
+		if (ipv6_get_lladdr(dev, &addr_buf,
+				   (IFA_F_TENTATIVE|IFA_F_OPTIMISTIC)))
 			return;
 		saddr = &addr_buf;
 	}
@@ -624,9 +627,33 @@ void ndisc_send_rs(struct net_device *dev, struct in6_addr *saddr,
 	struct sk_buff *skb;
 	struct icmp6hdr *hdr;
 	__u8 * opt;
+	struct inet6_ifaddr *ifp;
+	int send_sllao = dev->addr_len;
 	int len;
 	int err;
 
+
+#ifdef CONFIG_IPV6_OPTIMISTIC_DAD
+	/*
+	 * According to section 2.2 of RFC 4429, we must not
+	 * send router solicitations with a sllao from
+	 * optimistic addresses, but we may send the solicitation
+	 * if we don't include the sllao.  So here we check
+	 * if our address is optimistic, and if so, we
+	 * supress the inclusion of the sllao.
+	 */
+	if (send_sllao) {
+		ifp = ipv6_get_ifaddr(saddr, dev, 1);
+		if (ifp) {
+			if (ifp->flags & IFA_F_OPTIMISTIC)  {
+				send_sllao=0;
+				in6_ifa_put(ifp);
+			}
+		} else {
+			send_sllao = 0;
+		}
+	}
+#endif
 	ndisc_flow_init(&fl, NDISC_ROUTER_SOLICITATION, saddr, daddr,
 			dev->ifindex);
 
@@ -639,7 +666,7 @@ void ndisc_send_rs(struct net_device *dev, struct in6_addr *saddr,
 		return;
 
 	len = sizeof(struct icmp6hdr);
-	if (dev->addr_len)
+	if (send_sllao)
 		len += ndisc_opt_addr_space(dev);
 
 	skb = sock_alloc_send_skb(sk,
@@ -666,7 +693,7 @@ void ndisc_send_rs(struct net_device *dev, struct in6_addr *saddr,
 
 	opt = (u8*) (hdr + 1);
 
-	if (dev->addr_len)
+	if (send_sllao)
 		ndisc_fill_addr_option(opt, ND_OPT_SOURCE_LL_ADDR, dev->dev_addr,
 				       dev->addr_len, dev->type);
 
@@ -798,28 +825,39 @@ static void ndisc_recv_ns(struct sk_buff *skb)
 	inc = ipv6_addr_is_multicast(daddr);
 
 	if ((ifp = ipv6_get_ifaddr(&msg->target, dev, 1)) != NULL) {
-		if (ifp->flags & IFA_F_TENTATIVE) {
-			/* Address is tentative. If the source
-			   is unspecified address, it is someone
-			   does DAD, otherwise we ignore solicitations
-			   until DAD timer expires.
-			 */
-			if (!dad)
+
+		if (ifp->flags & (IFA_F_TENTATIVE|IFA_F_OPTIMISTIC)) {
+			if (dad) {
+				if (dev->type == ARPHRD_IEEE802_TR) {
+					unsigned char *sadr = skb->mac.raw;
+					if (((sadr[8] ^ dev->dev_addr[0]) & 0x7f) == 0 &&
+					    sadr[9] == dev->dev_addr[1] &&
+					    sadr[10] == dev->dev_addr[2] &&
+					    sadr[11] == dev->dev_addr[3] &&
+					    sadr[12] == dev->dev_addr[4] &&
+					    sadr[13] == dev->dev_addr[5]) {
+						/* looped-back to us */
+						goto out;
+					}
+				}
+
+				/*
+				 * We are colliding with another node
+				 * who is doing DAD
+				 * so fail our DAD process
+				 */
+				addrconf_dad_failure(ifp);
 				goto out;
-			if (dev->type == ARPHRD_IEEE802_TR) {
-				unsigned char *sadr = skb->mac.raw;
-				if (((sadr[8] ^ dev->dev_addr[0]) & 0x7f) == 0 &&
-				    sadr[9] == dev->dev_addr[1] &&
-				    sadr[10] == dev->dev_addr[2] &&
-				    sadr[11] == dev->dev_addr[3] &&
-				    sadr[12] == dev->dev_addr[4] &&
-				    sadr[13] == dev->dev_addr[5]) {
-					/* looped-back to us */
+			} else {
+				/*
+				 * This is not a dad solicitation.
+				 * If we are an optimistic node,
+				 * we should respond.
+				 * Otherwise, we should ignore it.
+				 */
+				if (!(ifp->flags & IFA_F_OPTIMISTIC))
 					goto out;
-				}
 			}
-			addrconf_dad_failure(ifp);
-			return;
 		}
 
 		idev = ifp->idev;
@@ -1408,7 +1446,7 @@ void ndisc_send_redirect(struct sk_buff *skb, struct neighbour *neigh,
 
 	dev = skb->dev;
 
-	if (ipv6_get_lladdr(dev, &saddr_buf)) {
+	if (ipv6_get_lladdr(dev, &saddr_buf, IFA_F_TENTATIVE)) {
 		ND_PRINTK2(KERN_WARNING
 			   "ICMPv6 Redirect: no link-local address on %s\n",
 			   dev->name);