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/ipv6/route.c b/net/ipv6/route.c
index 98796b0..d9cb832 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -76,6 +76,7 @@
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 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 *,
@@ -103,6 +104,7 @@
.gc = ip6_dst_gc,
.gc_thresh = 1024,
.check = ip6_dst_check,
+ .default_advmss = ip6_default_advmss,
.destroy = ip6_dst_destroy,
.ifdown = ip6_dst_ifdown,
.negative_advice = ip6_negative_advice,
@@ -937,8 +939,12 @@
static int ipv6_get_mtu(struct net_device *dev);
-static inline unsigned int ipv6_advmss(struct net *net, unsigned int mtu)
+static unsigned int ip6_default_advmss(const struct dst_entry *dst)
{
+ struct net_device *dev = dst->dev;
+ unsigned int mtu = dst_mtu(dst);
+ struct net *net = dev_net(dev);
+
mtu -= sizeof(struct ipv6hdr) + sizeof(struct tcphdr);
if (mtu < net->ipv6.sysctl.ip6_rt_min_advmss)
@@ -990,7 +996,6 @@
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));
- dst_metric_set(&rt->dst, RTAX_ADVMSS, ipv6_advmss(net, dst_mtu(&rt->dst)));
rt->dst.output = ip6_output;
#if 0 /* there's no chance to use these for ndisc */
@@ -1312,8 +1317,6 @@
if (!dst_mtu(&rt->dst))
dst_metric_set(&rt->dst, RTAX_MTU, ipv6_get_mtu(dev));
- if (!dst_metric(&rt->dst, RTAX_ADVMSS))
- dst_metric_set(&rt->dst, RTAX_ADVMSS, ipv6_advmss(net, dst_mtu(&rt->dst)));
rt->dst.dev = dev;
rt->rt6i_idev = idev;
rt->rt6i_table = table;
@@ -1540,8 +1543,6 @@
nrt->rt6i_nexthop = neigh_clone(neigh);
/* Reset pmtu, it may be better */
dst_metric_set(&nrt->dst, RTAX_MTU, ipv6_get_mtu(neigh->dev));
- dst_metric_set(&nrt->dst, RTAX_ADVMSS, ipv6_advmss(dev_net(neigh->dev),
- dst_mtu(&nrt->dst)));
if (ip6_ins_rt(nrt))
goto out;
@@ -1971,7 +1972,6 @@
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_ADVMSS, ipv6_advmss(net, dst_mtu(&rt->dst)));
dst_metric_set(&rt->dst, RTAX_HOPLIMIT, -1);
rt->dst.obsolete = -1;
@@ -2041,7 +2041,6 @@
{
struct rt6_mtu_change_arg *arg = (struct rt6_mtu_change_arg *) p_arg;
struct inet6_dev *idev;
- struct net *net = dev_net(arg->dev);
/* In IPv6 pmtu discovery is not optional,
so that RTAX_MTU lock cannot disable it.
@@ -2073,7 +2072,6 @@
(dst_mtu(&rt->dst) < arg->mtu &&
dst_mtu(&rt->dst) == idev->cnf.mtu6))) {
dst_metric_set(&rt->dst, RTAX_MTU, arg->mtu);
- dst_metric_set(&rt->dst, RTAX_ADVMSS, ipv6_advmss(net, arg->mtu));
}
return 0;
}