net: Abstract default MTU metric calculation behind an accessor.

Like RTAX_ADVMSS, make the default calculation go through a dst_ops
method rather than caching the computation in the routing cache
entries.

Now dst metrics are pretty much left as-is when new entries are
created, thus optimizing metric sharing becomes a real possibility.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 16 insertions, 21 deletions

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index d9cb832be529..e7efb269a6e9 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -77,6 +77,7 @@
 static struct rt6_info * ip6_rt_copy(struct rt6_info *ort);
 static struct dst_entry *ip6_dst_check(struct dst_entry *dst, u32 cookie);
 static unsigned int      ip6_default_advmss(const struct dst_entry *dst);
+static unsigned int      ip6_default_mtu(const struct dst_entry *dst);
 static struct dst_entry *ip6_negative_advice(struct dst_entry *);
 static void             ip6_dst_destroy(struct dst_entry *);
 static void             ip6_dst_ifdown(struct dst_entry *,
@@ -105,6 +106,7 @@ static struct dst_ops ip6_dst_ops_template = {
         .gc_thresh              =       1024,
         .check                  =       ip6_dst_check,
         .default_advmss         =       ip6_default_advmss,
+        .default_mtu            =       ip6_default_mtu,
         .destroy                =       ip6_dst_destroy,
         .ifdown                 =       ip6_dst_ifdown,
         .negative_advice        =       ip6_negative_advice,
@@ -937,8 +939,6 @@ static void ip6_rt_update_pmtu(struct dst_entry *dst, u32 mtu)
         }
 }
 
-static int ipv6_get_mtu(struct net_device *dev);
-
 static unsigned int ip6_default_advmss(const struct dst_entry *dst)
 {
         struct net_device *dev = dst->dev;
@@ -961,6 +961,20 @@ static unsigned int ip6_default_advmss(const struct dst_entry *dst)
         return mtu;
 }
 
+static unsigned int ip6_default_mtu(const struct dst_entry *dst)
+{
+        unsigned int mtu = IPV6_MIN_MTU;
+        struct inet6_dev *idev;
+
+        rcu_read_lock();
+        idev = __in6_dev_get(dst->dev);
+        if (idev)
+                mtu = idev->cnf.mtu6;
+        rcu_read_unlock();
+
+        return mtu;
+}
+
 static struct dst_entry *icmp6_dst_gc_list;
 static DEFINE_SPINLOCK(icmp6_dst_lock);
 
@@ -995,7 +1009,6 @@ struct dst_entry *icmp6_dst_alloc(struct net_device *dev,
         rt->rt6i_nexthop  = neigh;
         atomic_set(&rt->dst.__refcnt, 1);
         dst_metric_set(&rt->dst, RTAX_HOPLIMIT, 255);
-        dst_metric_set(&rt->dst, RTAX_MTU, ipv6_get_mtu(rt->rt6i_dev));
         rt->dst.output  = ip6_output;
 
 #if 0   /* there's no chance to use these for ndisc */
@@ -1094,19 +1107,6 @@ out:
    Remove it only when all the things will work!
  */
 
-static int ipv6_get_mtu(struct net_device *dev)
-{
-        int mtu = IPV6_MIN_MTU;
-        struct inet6_dev *idev;
-
-        rcu_read_lock();
-        idev = __in6_dev_get(dev);
-        if (idev)
-                mtu = idev->cnf.mtu6;
-        rcu_read_unlock();
-        return mtu;
-}
-
 int ip6_dst_hoplimit(struct dst_entry *dst)
 {
         int hoplimit = dst_metric_raw(dst, RTAX_HOPLIMIT);
@@ -1315,8 +1315,6 @@ install_route:
                 }
         }
 
-        if (!dst_mtu(&rt->dst))
-                dst_metric_set(&rt->dst, RTAX_MTU, ipv6_get_mtu(dev));
         rt->dst.dev = dev;
         rt->rt6i_idev = idev;
         rt->rt6i_table = table;
@@ -1541,8 +1539,6 @@ void rt6_redirect(struct in6_addr *dest, struct in6_addr *src,
 
         ipv6_addr_copy(&nrt->rt6i_gateway, (struct in6_addr*)neigh->primary_key);
         nrt->rt6i_nexthop = neigh_clone(neigh);
-        /* Reset pmtu, it may be better */
-        dst_metric_set(&nrt->dst, RTAX_MTU, ipv6_get_mtu(neigh->dev));
 
         if (ip6_ins_rt(nrt))
                 goto out;
@@ -1971,7 +1967,6 @@ struct rt6_info *addrconf_dst_alloc(struct inet6_dev *idev,
         rt->dst.output = ip6_output;
         rt->rt6i_dev = net->loopback_dev;
         rt->rt6i_idev = idev;
-        dst_metric_set(&rt->dst, RTAX_MTU, ipv6_get_mtu(rt->rt6i_dev));
         dst_metric_set(&rt->dst, RTAX_HOPLIMIT, -1);
         rt->dst.obsolete = -1;