ipv6: Reparent temporary address(es) if global address was deleted from userspace

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 protected]>

---
  net/ipv6/addrconf.c | 34 +++++++++++++++++++++++++++++++---
  1 file changed, 31 insertions(+), 3 deletions(-)

net/ipv6/addrconf.c +2 -0

index 6c7fa08..4d5595b 100644
@@ -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 *

net/ipv6/addrconf.c +16 -1

+		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;

net/ipv6/addrconf.c +2 -0

+		}
+
  		if (!(flags&IFA_F_TENTATIVE))
  			ipv6_ifa_notify(0, ift);
  	}

Quoted 5 lines

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.

Nit: your commit description should only be ~75 chars wide max

Quoted 19 lines

Fix this by reparenting orphaned temporary addresses.

Signed-off-by Heiner Kallweit <[email protected]>

---
  net/ipv6/addrconf.c | 34 +++++++++++++++++++++++++++++++---
  1 file changed, 31 insertions(+), 3 deletions(-)

net/ipv6/addrconf.c +2 -0

index 6c7fa08..4d5595b 100644
@@ -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 *

net/ipv6/addrconf.c static void manage_tempaddrs(struct inet6_dev *idev, · line 2091

Quoted 10 lines

net/ipv6/addrconf.c +4 -2

+            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;

You can collapse initialization where you declare the variable.

Quoted 28 lines

net/ipv6/addrconf.c +16 -1

+        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;

net/ipv6/addrconf.c static void manage_tempaddrs(struct inet6_dev *idev, · line 2142

Quoted 5 lines

net/ipv6/addrconf.c +2 -0

@@ -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

Nit: s/prefered/preferred/

net/ipv6/addrconf.c static void manage_tempaddrs(struct inet6_dev *idev, · line 2147

Quoted 5 lines

net/ipv6/addrconf.c +5 -0

+         */
+        if (reparent && prefered_lft > regen_advance) {
+            create = false;
+            pr_info("%s: reparent orphaned temporary address\n",
+                __func__);

The pr_info() should ideally be removed (or at least made pr_debug()).

Quoted 6 lines

net/ipv6/addrconf.c +2 -0

+        }
+
          if (!(flags&IFA_F_TENTATIVE))
              ipv6_ifa_notify(0, ift);
      }