net: Abstract default ADVMSS behind an accessor.
Make all RTAX_ADVMSS metric accesses go through a new helper function,
dst_metric_advmss().
Leave the actual default metric as "zero" in the real metric slot,
and compute the actual default value dynamically via a new dst_ops
AF specific callback.
For stacked IPSEC routes, we use the advmss of the path which
preserves existing behavior.
Unlike ipv4/ipv6, DecNET ties the advmss to the mtu and thus updates
advmss on pmtu updates. This inconsistency in advmss handling
results in more raw metric accesses than I wish we ended up with.
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/dst.h b/include/net/dst.h
index 755ac6c..03a1c3d 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -112,10 +112,22 @@
static inline u32
dst_metric(const struct dst_entry *dst, const int metric)
{
- WARN_ON_ONCE(metric == RTAX_HOPLIMIT);
+ WARN_ON_ONCE(metric == RTAX_HOPLIMIT ||
+ metric == RTAX_ADVMSS);
return dst_metric_raw(dst, metric);
}
+static inline u32
+dst_metric_advmss(const struct dst_entry *dst)
+{
+ u32 advmss = dst_metric_raw(dst, RTAX_ADVMSS);
+
+ if (!advmss)
+ advmss = dst->ops->default_advmss(dst);
+
+ return advmss;
+}
+
static inline void dst_metric_set(struct dst_entry *dst, int metric, u32 val)
{
dst->_metrics[metric-1] = val;
diff --git a/include/net/dst_ops.h b/include/net/dst_ops.h
index 51665b3..15fb7af 100644
--- a/include/net/dst_ops.h
+++ b/include/net/dst_ops.h
@@ -16,6 +16,7 @@
int (*gc)(struct dst_ops *ops);
struct dst_entry * (*check)(struct dst_entry *, __u32 cookie);
+ unsigned int (*default_advmss)(const struct dst_entry *);
void (*destroy)(struct dst_entry *);
void (*ifdown)(struct dst_entry *,
struct net_device *dev, int how);