ipv6: RCU changes in ipv6_get_mtu() and ip6_dst_hoplimit()

Use RCU to avoid atomic ops on idev refcnt in ipv6_get_mtu()
and ip6_dst_hoplimit()

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 8 deletions

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f7702850d45c..8f2d0400cf8a 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1084,11 +1084,11 @@ static int ipv6_get_mtu(struct net_device *dev)
         int mtu = IPV6_MIN_MTU;
         struct inet6_dev *idev;
 
-        idev = in6_dev_get(dev);
-        if (idev) {
+        rcu_read_lock();
+        idev = __in6_dev_get(dev);
+        if (idev)
                 mtu = idev->cnf.mtu6;
-                in6_dev_put(idev);
-        }
+        rcu_read_unlock();
         return mtu;
 }
 
@@ -1097,12 +1097,15 @@ int ip6_dst_hoplimit(struct dst_entry *dst)
         int hoplimit = dst_metric(dst, RTAX_HOPLIMIT);
         if (hoplimit < 0) {
                 struct net_device *dev = dst->dev;
-                struct inet6_dev *idev = in6_dev_get(dev);
-                if (idev) {
+                struct inet6_dev *idev;
+
+                rcu_read_lock();
+                idev = __in6_dev_get(dev);
+                if (idev)
                         hoplimit = idev->cnf.hop_limit;
-                        in6_dev_put(idev);
-                } else
+                else
                         hoplimit = dev_net(dev)->ipv6.devconf_all->hop_limit;
+                rcu_read_unlock();
         }
         return hoplimit;
 }