[IPV6] ADDRCONF: Allow non-DAD'able addresses.

IFA_F_NODAD flag, similar to IN6_IFF_NODAD in BSDs, is introduced
to skip DAD.

This flag should be set to Mobile IPv6 Home Address(es) on Mobile
Node because DAD would fail if we should perform DAD; our Home Agent
protects our Home Address(es).

Signed-off-by: Noriaki TAKAMIYA <takamiya@po.ntts.co.jp>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/if_addr.h

@@ -38,6 +38,7 @@ enum
 #define IFA_F_SECONDARY		0x01
 #define IFA_F_TEMPORARY		IFA_F_SECONDARY
 
+#define	IFA_F_NODAD		0x02
 #define IFA_F_DEPRECATED	0x20
 #define IFA_F_TENTATIVE		0x40
 #define IFA_F_PERMANENT		0x80

net/ipv6/addrconf.c

@@ -1873,12 +1873,11 @@ err_exit:
  *	Manual configuration of address on an interface
  */
 static int inet6_addr_add(int ifindex, struct in6_addr *pfx, int plen,
-			  __u32 prefered_lft, __u32 valid_lft)
+			  __u8 ifa_flags, __u32 prefered_lft, __u32 valid_lft)
 {
 	struct inet6_ifaddr *ifp;
 	struct inet6_dev *idev;
 	struct net_device *dev;
-	__u8 ifa_flags = 0;
 	int scope;
 
 	ASSERT_RTNL();
@@ -1971,7 +1970,7 @@ int addrconf_add_ifaddr(void __user *arg)
 
 	rtnl_lock();
 	err = inet6_addr_add(ireq.ifr6_ifindex, &ireq.ifr6_addr, ireq.ifr6_prefixlen,
-			     INFINITY_LIFE_TIME, INFINITY_LIFE_TIME);
+			     IFA_F_PERMANENT, INFINITY_LIFE_TIME, INFINITY_LIFE_TIME);
 	rtnl_unlock();
 	return err;
 }
@@ -2514,7 +2513,8 @@ static void addrconf_dad_start(struct inet6_ifaddr *ifp, u32 flags)
 	spin_lock_bh(&ifp->lock);
 
 	if (dev->flags&(IFF_NOARP|IFF_LOOPBACK) ||
-	    !(ifp->flags&IFA_F_TENTATIVE)) {
+	    !(ifp->flags&IFA_F_TENTATIVE) ||
+	    ifp->flags & IFA_F_NODAD) {
 		ifp->flags &= ~IFA_F_TENTATIVE;
 		spin_unlock_bh(&ifp->lock);
 		read_unlock_bh(&idev->lock);
@@ -2912,28 +2912,25 @@ inet6_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	return inet6_addr_del(ifm->ifa_index, pfx, ifm->ifa_prefixlen);
 }
 
-static int inet6_addr_modify(struct inet6_ifaddr *ifp, u32 prefered_lft,
-			     u32 valid_lft)
+static int inet6_addr_modify(struct inet6_ifaddr *ifp, u8 ifa_flags,
+			     u32 prefered_lft, u32 valid_lft)
 {
-	int ifa_flags = 0;
-
 	if (!valid_lft || (prefered_lft > valid_lft))
 		return -EINVAL;
 
 	if (valid_lft == INFINITY_LIFE_TIME)
-		ifa_flags = IFA_F_PERMANENT;
+		ifa_flags |= IFA_F_PERMANENT;
 	else if (valid_lft >= 0x7FFFFFFF/HZ)
 		valid_lft = 0x7FFFFFFF/HZ;
 
 	if (prefered_lft == 0)
-		ifa_flags = IFA_F_DEPRECATED;
+		ifa_flags |= IFA_F_DEPRECATED;
 	else if ((prefered_lft >= 0x7FFFFFFF/HZ) &&
 		 (prefered_lft != INFINITY_LIFE_TIME))
 		prefered_lft = 0x7FFFFFFF/HZ;
 
 	spin_lock_bh(&ifp->lock);
-	ifp->flags = (ifp->flags & ~(IFA_F_DEPRECATED|IFA_F_PERMANENT)) | ifa_flags;
-
+	ifp->flags = (ifp->flags & ~(IFA_F_DEPRECATED | IFA_F_PERMANENT | IFA_F_NODAD)) | ifa_flags;
 	ifp->tstamp = jiffies;
 	ifp->valid_lft = valid_lft;
 	ifp->prefered_lft = prefered_lft;
@@ -2955,7 +2952,8 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	struct in6_addr *pfx;
 	struct inet6_ifaddr *ifa;
 	struct net_device *dev;
-	u32 valid_lft, preferred_lft;
+	u32 valid_lft = INFINITY_LIFE_TIME, preferred_lft = INFINITY_LIFE_TIME;
+	u8 ifa_flags;
 	int err;
 
 	err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, ifa_ipv6_policy);
@@ -2982,6 +2980,9 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 	if (dev == NULL)
 		return -ENODEV;
 
+	/* We ignore other flags so far. */
+	ifa_flags = ifm->ifa_flags & IFA_F_NODAD;
+
 	ifa = ipv6_get_ifaddr(pfx, dev, 1);
 	if (ifa == NULL) {
 		/*
@@ -2989,14 +2990,14 @@ inet6_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh, void *arg)
 		 * userspace alreay relies on not having to provide this.
 		 */
 		return inet6_addr_add(ifm->ifa_index, pfx, ifm->ifa_prefixlen,
-				      preferred_lft, valid_lft);
+				      ifa_flags, preferred_lft, valid_lft);
 	}
 
 	if (nlh->nlmsg_flags & NLM_F_EXCL ||
 	    !(nlh->nlmsg_flags & NLM_F_REPLACE))
 		err = -EEXIST;
 	else
-		err = inet6_addr_modify(ifa, preferred_lft, valid_lft);
+		err = inet6_addr_modify(ifa, ifa_flags, preferred_lft, valid_lft);
 
 	in6_ifa_put(ifa);