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Date:	Tue, 23 Jan 2007 15:51:18 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	YOSHIFUJI Hideaki / 吉藤英明 
	<yoshfuji@...ux-ipv6.org>
Cc:	davem@...emloft.net, kuznet@....inr.ac.ru, pekkas@...core.fi,
	jmorris@...ei.org, kaber@...eworks.de, netdev@...r.kernel.org
Subject: Re: [PATCH] IPv6: Implement RFC 4429 Optimistic Duplicate Address Detection

On Tue, Jan 23, 2007 at 09:18:20AM +0900, YOSHIFUJI Hideaki / 吉藤英明 wrote:
> Hello.
<snip>

New patch attached, incorporating Yoshijui and Vlads latest comments.  I didn't
follow guidance on the ndisc_recv_ns comment, Yoshifuji, since Vlad had already
suggested an alternate solution in a previous post, but from looking at them
both, they should be equivalent.

Thanks & Regards
Neil

Signed-off-by: Neil Horman <nhorman@...driver.com>


 include/linux/if_addr.h |    1 
 include/linux/ipv6.h    |    2 +
 include/linux/sysctl.h  |    1 
 include/net/addrconf.h  |    4 +-
 net/ipv6/addrconf.c     |   56 ++++++++++++++++++++++++++++----
 net/ipv6/mcast.c        |    4 +-
 net/ipv6/ndisc.c        |   82 +++++++++++++++++++++++++++++++++++-------------
 7 files changed, 117 insertions(+), 33 deletions(-)


diff --git a/include/linux/if_addr.h b/include/linux/if_addr.h
index d557e4c..43f3bed 100644
--- a/include/linux/if_addr.h
+++ b/include/linux/if_addr.h
@@ -39,6 +39,7 @@ enum
 #define IFA_F_TEMPORARY		IFA_F_SECONDARY
 
 #define	IFA_F_NODAD		0x02
+#define IFA_F_OPTIMISTIC	0x04
 #define	IFA_F_HOMEADDRESS	0x10
 #define IFA_F_DEPRECATED	0x20
 #define IFA_F_TENTATIVE		0x40
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index f824113..5d37abf 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -177,6 +177,7 @@ struct ipv6_devconf {
 #endif
 #endif
 	__s32		proxy_ndp;
+	__s32		optimistic_dad;
 	void		*sysctl;
 };
 
@@ -205,6 +206,7 @@ enum {
 	DEVCONF_RTR_PROBE_INTERVAL,
 	DEVCONF_ACCEPT_RA_RT_INFO_MAX_PLEN,
 	DEVCONF_PROXY_NDP,
+	DEVCONF_OPTIMISTIC_DAD,
 	DEVCONF_MAX
 };
 
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 81480e6..972a33a 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -570,6 +570,7 @@ enum {
 	NET_IPV6_RTR_PROBE_INTERVAL=21,
 	NET_IPV6_ACCEPT_RA_RT_INFO_MAX_PLEN=22,
 	NET_IPV6_PROXY_NDP=23,
+	NET_IPV6_OPTIMISTIC_DAD=24,
 	__NET_IPV6_MAX
 };
 
diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 88df8fc..d248a19 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -73,7 +73,9 @@ extern int			ipv6_get_saddr(struct dst_entry *dst,
 extern int			ipv6_dev_get_saddr(struct net_device *dev, 
 					       struct in6_addr *daddr,
 					       struct in6_addr *saddr);
-extern int			ipv6_get_lladdr(struct net_device *dev, struct in6_addr *);
+extern int			ipv6_get_lladdr(struct net_device *dev, 
+						struct in6_addr *,
+						unsigned char banned_flags);
 extern int			ipv6_rcv_saddr_equal(const struct sock *sk, 
 						      const struct sock *sk2);
 extern void			addrconf_join_solict(struct net_device *dev,
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 2a7e461..d2b01ec 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -830,7 +830,8 @@ retry:
 	ift = !max_addresses ||
 	      ipv6_count_addresses(idev) < max_addresses ? 
 		ipv6_add_addr(idev, &addr, tmp_plen,
-			      ipv6_addr_type(&addr)&IPV6_ADDR_SCOPE_MASK, IFA_F_TEMPORARY) : NULL;
+			      ipv6_addr_type(&addr)&IPV6_ADDR_SCOPE_MASK, 
+			      IFA_F_TEMPORARY|IFA_F_OPTIMISTIC) : NULL;
 	if (!ift || IS_ERR(ift)) {
 		in6_ifa_put(ifp);
 		in6_dev_put(idev);
@@ -1174,7 +1175,8 @@ int ipv6_get_saddr(struct dst_entry *dst,
 }
 
 
-int ipv6_get_lladdr(struct net_device *dev, struct in6_addr *addr)
+int ipv6_get_lladdr(struct net_device *dev, struct in6_addr *addr, 
+		    unsigned char banned_flags)
 {
 	struct inet6_dev *idev;
 	int err = -EADDRNOTAVAIL;
@@ -1185,7 +1187,7 @@ int ipv6_get_lladdr(struct net_device *dev, struct in6_addr *addr)
 
 		read_lock_bh(&idev->lock);
 		for (ifp=idev->addr_list; ifp; ifp=ifp->if_next) {
-			if (ifp->scope == IFA_LINK && !(ifp->flags&IFA_F_TENTATIVE)) {
+			if (ifp->scope == IFA_LINK && !(ifp->flags & banned_flags)) {
 				ipv6_addr_copy(addr, &ifp->addr);
 				err = 0;
 				break;
@@ -1751,6 +1753,7 @@ ok:
 
 			update_lft = create = 1;
 			ifp->cstamp = jiffies;
+			ifp->flags |= IFA_F_OPTIMISTIC;
 			addrconf_dad_start(ifp, RTF_ADDRCONF|RTF_PREFIX_RT);
 		}
 
@@ -1945,7 +1948,11 @@ static int inet6_addr_add(int ifindex, struct in6_addr *pfx, int plen,
 		ifp->prefered_lft = prefered_lft;
 		ifp->tstamp = jiffies;
 		spin_unlock_bh(&ifp->lock);
-
+		/*
+		 * Note that section 3.1 of RFC 4429 indicates
+		 * That the Optimistic flag should not be set for
+		 * manually configured addresses
+		 */
 		addrconf_dad_start(ifp, 0);
 		in6_ifa_put(ifp);
 		addrconf_verify(0);
@@ -2123,7 +2130,8 @@ static void addrconf_add_linklocal(struct inet6_dev *idev, struct in6_addr *addr
 {
 	struct inet6_ifaddr * ifp;
 
-	ifp = ipv6_add_addr(idev, addr, 64, IFA_LINK, IFA_F_PERMANENT);
+	ifp = ipv6_add_addr(idev, addr, 64, IFA_LINK, 
+		            IFA_F_PERMANENT|IFA_F_OPTIMISTIC);
 	if (!IS_ERR(ifp)) {
 		addrconf_dad_start(ifp, 0);
 		in6_ifa_put(ifp);
@@ -2190,7 +2198,7 @@ ipv6_inherit_linklocal(struct inet6_dev *idev, struct net_device *link_dev)
 {
 	struct in6_addr lladdr;
 
-	if (!ipv6_get_lladdr(link_dev, &lladdr)) {
+	if (!ipv6_get_lladdr(link_dev, &lladdr, IFA_F_TENTATIVE)) {
 		addrconf_add_linklocal(idev, &lladdr);
 		return 0;
 	}
@@ -2537,8 +2545,18 @@ static void addrconf_dad_start(struct inet6_ifaddr *ifp, u32 flags)
 	struct inet6_dev *idev = ifp->idev;
 	struct net_device *dev = idev->dev;
 
+	if (!idev->cnf.optimistic_dad)
+		ifp->flags &= ~IFA_F_OPTIMISTIC;
+
 	addrconf_join_solict(dev, &ifp->addr);
 
+	/*
+	 * Optimistic nodes need to joing the anycast address
+	 * right away
+	 */
+	if (ifp->flags & IFA_F_OPTIMISTIC)
+		addrconf_join_anycast(ifp);
+
 	if (ifp->prefix_len != 128 && (ifp->flags&IFA_F_PERMANENT))
 		addrconf_prefix_route(&ifp->addr, ifp->prefix_len, dev, 0,
 					flags);
@@ -2553,7 +2571,7 @@ static void addrconf_dad_start(struct inet6_ifaddr *ifp, u32 flags)
 	if (dev->flags&(IFF_NOARP|IFF_LOOPBACK) ||
 	    !(ifp->flags&IFA_F_TENTATIVE) ||
 	    ifp->flags & IFA_F_NODAD) {
-		ifp->flags &= ~IFA_F_TENTATIVE;
+		ifp->flags &= ~(IFA_F_TENTATIVE|IFA_F_OPTIMISTIC);
 		spin_unlock_bh(&ifp->lock);
 		read_unlock_bh(&idev->lock);
 
@@ -2573,6 +2591,18 @@ static void addrconf_dad_start(struct inet6_ifaddr *ifp, u32 flags)
 		addrconf_dad_stop(ifp);
 		return;
 	}
+
+	/*
+	 * Forwarding devices (routers) should not use
+	 * optimistic addresses
+	 * Nor should interfaces that don't know the 
+	 * Source address for their default gateway
+	 * RFC 4429 Sec 3.3
+	 */
+	if ((ipv6_devconf.forwarding) ||
+	   (ifp->rt == NULL))
+		ifp->flags &= ~IFA_F_OPTIMISTIC;
+
 	addrconf_dad_kick(ifp);
 	spin_unlock_bh(&ifp->lock);
 out:
@@ -2597,7 +2627,7 @@ static void addrconf_dad_timer(unsigned long data)
 		 * DAD was successful
 		 */
 
-		ifp->flags &= ~IFA_F_TENTATIVE;
+		ifp->flags &= ~(IFA_F_TENTATIVE|IFA_F_OPTIMISTIC);
 		spin_unlock_bh(&ifp->lock);
 		read_unlock_bh(&idev->lock);
 
@@ -3398,6 +3428,7 @@ static void inline ipv6_store_devconf(struct ipv6_devconf *cnf,
 #endif
 #endif
 	array[DEVCONF_PROXY_NDP] = cnf->proxy_ndp;
+	array[DEVCONF_OPTIMISTIC_DAD] = cnf->optimistic_dad;
 }
 
 static inline size_t inet6_if_nlmsg_size(void)
@@ -3918,6 +3949,15 @@ static struct addrconf_sysctl_table
 			.proc_handler	=	&proc_dointvec,
 		},
 		{
+			.ctl_name	=	NET_IPV6_OPTIMISTIC_DAD,
+			.procname       =       "optimistic_dad",
+			.data           =       &ipv6_devconf.optimistic_dad,
+			.maxlen         =       sizeof(int),
+			.mode           =       0644,
+			.proc_handler   =       &proc_dointvec,
+
+		},
+		{
 			.ctl_name	=	0,	/* sentinel */
 		}
 	},
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 882cde4..9c5273c 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1411,7 +1411,7 @@ static struct sk_buff *mld_newpack(struct net_device *dev, int size)
 
 	skb_reserve(skb, LL_RESERVED_SPACE(dev));
 
-	if (ipv6_get_lladdr(dev, &addr_buf)) {
+	if (ipv6_get_lladdr(dev, &addr_buf, IFA_F_TENTATIVE)) {
 		/* <draft-ietf-magma-mld-source-05.txt>:
 		 * use unspecified address as the source address 
 		 * when a valid link-local address is not available.
@@ -1789,7 +1789,7 @@ static void igmp6_send(struct in6_addr *addr, struct net_device *dev, int type)
 
 	skb_reserve(skb, LL_RESERVED_SPACE(dev));
 
-	if (ipv6_get_lladdr(dev, &addr_buf)) {
+	if (ipv6_get_lladdr(dev, &addr_buf, IFA_F_TENTATIVE)) {
 		/* <draft-ietf-magma-mld-source-05.txt>:
 		 * use unspecified address as the source address 
 		 * when a valid link-local address is not available.
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 6a9f616..fcd22e3 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -498,7 +498,21 @@ static void ndisc_send_na(struct net_device *dev, struct neighbour *neigh,
         msg->icmph.icmp6_unused = 0;
         msg->icmph.icmp6_router    = router;
         msg->icmph.icmp6_solicited = solicited;
-        msg->icmph.icmp6_override  = override;
+	if (!ifp || !(ifp->flags & IFA_F_OPTIMISTIC))
+		msg->icmph.icmp6_override  = override;
+	else {
+		/*
+		 * We must clear the override flag on all
+		 * neighbor advertisements from source 
+		 * addresses that are OPTIMISTIC - RFC 4429
+		 * section 2.2
+		 */
+		if (override)
+			printk(KERN_WARNING
+				"Disallowing override flag for OPTIMISTIC addr\n");
+		msg->icmph.icmp6_override = 0;
+	}
+
 
         /* Set the target address. */
 	ipv6_addr_copy(&msg->target, solicited_addr);
@@ -542,7 +556,8 @@ 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;
 	}
@@ -622,9 +637,20 @@ 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 len;
 	int err;
 
+	/*
+	 * Check the source address.  If its OPTIMISTIC
+	 * and addr_len is non-zero (implying the sllao option)
+	 * then don't send the RS (RFC 4429, section 2.2)
+	 */
+	ifp = ipv6_get_ifaddr(saddr, dev, 1);
+
+	if ((!ifp) || ((ifp->flags & IFA_F_OPTIMISTIC) && dev->addr_len))
+		return;
+
 	ndisc_flow_init(&fl, NDISC_ROUTER_SOLICITATION, saddr, daddr,
 			dev->ifindex);
 
@@ -746,6 +772,7 @@ static void ndisc_recv_ns(struct sk_buff *skb)
 	int dad = ipv6_addr_any(saddr);
 	int inc;
 	int is_router;
+	int type;
 
 	if (ipv6_addr_is_multicast(&msg->target)) {
 		ND_PRINTK2(KERN_WARNING 
@@ -796,28 +823,39 @@ 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;
@@ -1406,7 +1444,7 @@ 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);
-
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