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/ipv4/route.c b/net/ipv4/route.c
index 770f704..8099733 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -139,6 +139,7 @@
*/
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 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);
@@ -155,6 +156,7 @@
.protocol = cpu_to_be16(ETH_P_IP),
.gc = rt_garbage_collect,
.check = ipv4_dst_check,
+ .default_advmss = ipv4_default_advmss,
.destroy = ipv4_dst_destroy,
.ifdown = ipv4_dst_ifdown,
.negative_advice = ipv4_negative_advice,
@@ -383,8 +385,7 @@
(__force u32)r->rt_gateway,
r->rt_flags, atomic_read(&r->dst.__refcnt),
r->dst.__use, 0, (__force u32)r->rt_src,
- (dst_metric(&r->dst, RTAX_ADVMSS) ?
- (int)dst_metric(&r->dst, RTAX_ADVMSS) + 40 : 0),
+ dst_metric_advmss(&r->dst) + 40,
dst_metric(&r->dst, RTAX_WINDOW),
(int)((dst_metric(&r->dst, RTAX_RTT) >> 3) +
dst_metric(&r->dst, RTAX_RTTVAR)),
@@ -1798,6 +1799,19 @@
}
#endif
+static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
+{
+ unsigned int advmss = dst_metric_raw(dst, RTAX_ADVMSS);
+
+ if (advmss == 0) {
+ advmss = max_t(unsigned int, dst->dev->mtu - 40,
+ ip_rt_min_advmss);
+ if (advmss > 65535 - 40)
+ advmss = 65535 - 40;
+ }
+ return advmss;
+}
+
static void rt_set_nexthop(struct rtable *rt, struct fib_result *res, u32 itag)
{
struct dst_entry *dst = &rt->dst;
@@ -1823,11 +1837,7 @@
if (dst_mtu(dst) > IP_MAX_MTU)
dst_metric_set(dst, RTAX_MTU, IP_MAX_MTU);
- if (dst_metric(dst, RTAX_ADVMSS) == 0)
- dst_metric_set(dst, RTAX_ADVMSS,
- max_t(unsigned int, dst->dev->mtu - 40,
- ip_rt_min_advmss));
- if (dst_metric(dst, RTAX_ADVMSS) > 65535 - 40)
+ if (dst_metric_raw(dst, RTAX_ADVMSS) > 65535 - 40)
dst_metric_set(dst, RTAX_ADVMSS, 65535 - 40);
#ifdef CONFIG_NET_CLS_ROUTE