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/net/decnet/dn_route.c b/net/decnet/dn_route.c
index e2e9268..b8a5c05 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -110,6 +110,7 @@
static int dn_dst_gc(struct dst_ops *ops);
static struct dst_entry *dn_dst_check(struct dst_entry *, __u32);
+static unsigned int dn_dst_default_advmss(const struct dst_entry *dst);
static struct dst_entry *dn_dst_negative_advice(struct dst_entry *);
static void dn_dst_link_failure(struct sk_buff *);
static void dn_dst_update_pmtu(struct dst_entry *dst, u32 mtu);
@@ -129,6 +130,7 @@
.gc_thresh = 128,
.gc = dn_dst_gc,
.check = dn_dst_check,
+ .default_advmss = dn_dst_default_advmss,
.negative_advice = dn_dst_negative_advice,
.link_failure = dn_dst_link_failure,
.update_pmtu = dn_dst_update_pmtu,
@@ -245,7 +247,8 @@
}
if (!(dst_metric_locked(dst, RTAX_ADVMSS))) {
u32 mss = mtu - DN_MAX_NSP_DATA_HEADER;
- if (dst_metric(dst, RTAX_ADVMSS) > mss)
+ u32 existing_mss = dst_metric_raw(dst, RTAX_ADVMSS);
+ if (!existing_mss || existing_mss > mss)
dst_metric_set(dst, RTAX_ADVMSS, mss);
}
}
@@ -795,12 +798,17 @@
return NET_RX_DROP;
}
+static unsigned int dn_dst_default_advmss(const struct dst_entry *dst)
+{
+ return dn_mss_from_pmtu(dst->dev, dst_mtu(dst));
+}
+
static int dn_rt_set_next_hop(struct dn_route *rt, struct dn_fib_res *res)
{
struct dn_fib_info *fi = res->fi;
struct net_device *dev = rt->dst.dev;
struct neighbour *n;
- unsigned mss;
+ unsigned int metric;
if (fi) {
if (DN_FIB_RES_GW(*res) &&
@@ -820,10 +828,12 @@
if (dst_metric(&rt->dst, RTAX_MTU) == 0 ||
dst_metric(&rt->dst, RTAX_MTU) > rt->dst.dev->mtu)
dst_metric_set(&rt->dst, RTAX_MTU, rt->dst.dev->mtu);
- mss = dn_mss_from_pmtu(dev, dst_mtu(&rt->dst));
- if (dst_metric(&rt->dst, RTAX_ADVMSS) == 0 ||
- dst_metric(&rt->dst, RTAX_ADVMSS) > mss)
- dst_metric_set(&rt->dst, RTAX_ADVMSS, mss);
+ metric = dst_metric_raw(&rt->dst, RTAX_ADVMSS);
+ if (metric) {
+ unsigned int mss = dn_mss_from_pmtu(dev, dst_mtu(&rt->dst));
+ if (metric > mss)
+ dst_metric_set(&rt->dst, RTAX_ADVMSS, mss);
+ }
return 0;
}