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>
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 8099733..ae52096 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -140,6 +140,7 @@
static struct dst_entry *ipv4_dst_check(struct dst_entry *dst, u32 cookie);
static unsigned int ipv4_default_advmss(const struct dst_entry *dst);
+static unsigned int ipv4_default_mtu(const struct dst_entry *dst);
static void ipv4_dst_destroy(struct dst_entry *dst);
static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst);
static void ipv4_link_failure(struct sk_buff *skb);
@@ -157,6 +158,7 @@
.gc = rt_garbage_collect,
.check = ipv4_dst_check,
.default_advmss = ipv4_default_advmss,
+ .default_mtu = ipv4_default_mtu,
.destroy = ipv4_dst_destroy,
.ifdown = ipv4_dst_ifdown,
.negative_advice = ipv4_negative_advice,
@@ -1812,6 +1814,23 @@
return advmss;
}
+static unsigned int ipv4_default_mtu(const struct dst_entry *dst)
+{
+ unsigned int mtu = dst->dev->mtu;
+
+ if (unlikely(dst_metric_locked(dst, RTAX_MTU))) {
+ const struct rtable *rt = (const struct rtable *) dst;
+
+ if (rt->rt_gateway != rt->rt_dst && mtu > 576)
+ mtu = 576;
+ }
+
+ if (mtu > IP_MAX_MTU)
+ mtu = IP_MAX_MTU;
+
+ return mtu;
+}
+
static void rt_set_nexthop(struct rtable *rt, struct fib_result *res, u32 itag)
{
struct dst_entry *dst = &rt->dst;
@@ -1822,18 +1841,10 @@
FIB_RES_NH(*res).nh_scope == RT_SCOPE_LINK)
rt->rt_gateway = FIB_RES_GW(*res);
dst_import_metrics(dst, fi->fib_metrics);
- if (fi->fib_mtu == 0) {
- dst_metric_set(dst, RTAX_MTU, dst->dev->mtu);
- if (dst_metric_locked(dst, RTAX_MTU) &&
- rt->rt_gateway != rt->rt_dst &&
- dst->dev->mtu > 576)
- dst_metric_set(dst, RTAX_MTU, 576);
- }
#ifdef CONFIG_NET_CLS_ROUTE
dst->tclassid = FIB_RES_NH(*res).nh_tclassid;
#endif
- } else
- dst_metric_set(dst, RTAX_MTU, dst->dev->mtu);
+ }
if (dst_mtu(dst) > IP_MAX_MTU)
dst_metric_set(dst, RTAX_MTU, IP_MAX_MTU);