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net: Abstract default MTU metric calculation behind an accessor.

Browse source 
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>
This commit is contained in:
David S. Miller 2010-12-14 13:01:14 -08:00
parent 9fe146aef4
commit d33e455337
6 changed files with 60 additions and 39 deletions
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29
net/ipv4/route.c
View file

@ -140,6 +140,7 @@ static unsigned long expires_ljiffies;
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 @@ static struct dst_ops ipv4_dst_ops = {
.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 @@ static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
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 @@ static void rt_set_nexthop(struct rtable *rt, struct fib_result *res, u32 itag)
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);