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, 7 insertions, 0 deletions

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 36936c8ae961..8b3ef404c794 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2366,6 +2366,11 @@ static unsigned int xfrm_default_advmss(const struct dst_entry *dst)
         return dst_metric_advmss(dst->path);
 }
 
+static unsigned int xfrm_default_mtu(const struct dst_entry *dst)
+{
+        return dst_mtu(dst->path);
+}
+
 int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo)
 {
         struct net *net;
@@ -2385,6 +2390,8 @@ int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo)
                         dst_ops->check = xfrm_dst_check;
                 if (likely(dst_ops->default_advmss == NULL))
                         dst_ops->default_advmss = xfrm_default_advmss;
+                if (likely(dst_ops->default_mtu == NULL))
+                        dst_ops->default_mtu = xfrm_default_mtu;
                 if (likely(dst_ops->negative_advice == NULL))
                         dst_ops->negative_advice = xfrm_negative_advice;
                 if (likely(dst_ops->link_failure == NULL))