Subject: [PATCH] ipv6: Reparent temporary address(es) if global address was deleted from userspace

From: Heiner Kallweit <[email-masked]>
Date: Sun, 06 Apr 2014 21:04:11 +0200

If the kernel takes care of global and temporary addresses it can happen that the global
address is deleted from userspace, e.g. by network managers in case the link goes (temporarily) down.
In addition to the then orphaned temporary address(es) the next RA will create a new temporary address.
Therefore we might end up with more than one non-deprecated temporary address for the same prefix
for a longer period of time (>regen_advance). According to RfC 4941 sect. 3.4 this should not happen.

Fix this by reparenting orphaned temporary addresses.

Signed-off-by: Heiner Kallweit <[email-masked]>
---
 net/ipv6/addrconf.c | 34 +++++++++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 6c7fa08..4d5595b 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2077,14 +2077,34 @@ static void manage_tempaddrs(struct inet6_dev *idev,
 {
 	u32 flags;
 	struct inet6_ifaddr *ift;
+	unsigned long regen_advance;
 
 	read_lock_bh(&idev->lock);
+	regen_advance = idev->cnf.regen_max_retry *
+			idev->cnf.dad_transmits *
+			NEIGH_VAR(idev->nd_parms, RETRANS_TIME) / HZ;
 	/* update all temporary addresses in the list */
 	list_for_each_entry(ift, &idev->tempaddr_list, tmp_list) {
 		int age, max_valid, max_prefered;
+		bool reparent;
 
-		if (ifp != ift->ifpub)
-			continue;
+		reparent = false;
+		spin_lock(&ift->lock);
+		if (ifp != ift->ifpub) {
+			/* reparent if orphaned temporary address with same
+			 * prefix is found
+			 */
+			if (ipv6_prefix_equal(&ift->addr, &ifp->addr,
+					      ift->prefix_len)) {
+				in6_ifa_hold(ifp);
+				in6_ifa_put(ift->ifpub);
+				ift->ifpub = ifp;
+				reparent = true;
+			} else {
+				spin_unlock(&ift->lock);
+				continue;
+			}
+		}
 
 		/* RFC 4941 section 3.3:
 		 * If a received option will extend the lifetime of a public
@@ -2110,7 +2130,6 @@ static void manage_tempaddrs(struct inet6_dev *idev,
 		if (prefered_lft > max_prefered)
 			prefered_lft = max_prefered;
 
-		spin_lock(&ift->lock);
 		flags = ift->flags;
 		ift->valid_lft = valid_lft;
 		ift->prefered_lft = prefered_lft;
@@ -2119,6 +2138,15 @@ static void manage_tempaddrs(struct inet6_dev *idev,
 			ift->flags &= ~IFA_F_DEPRECATED;
 
 		spin_unlock(&ift->lock);
+		/* Don't create a temporary address if we reparented one which
+		 * is prefered more than regen_advance
+		 */
+		if (reparent && prefered_lft > regen_advance) {
+			create = false;
+			pr_info("%s: reparent orphaned temporary address\n",
+				__func__);
+		}
+
 		if (!(flags&IFA_F_TENTATIVE))
 			ipv6_ifa_notify(0, ift);
 	}
-- 
1.9.1.315.g3f09db0.dirty