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net: Abstract default ADVMSS behind an accessor.

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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>
This commit is contained in:
David S. Miller
2010-12-13 12:52:14 -08:00
parent cc6f02dd49
commit 0dbaee3b37
11 changed files with 75 additions and 33 deletions
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24
net/ipv4/route.c
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@@ -139,6 +139,7 @@ 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 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 @@ static struct dst_ops ipv4_dst_ops = {
.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 @@ static int rt_cache_seq_show(struct seq_file *seq, void *v)
(__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 @@ static void set_class_tag(struct rtable *rt, u32 tag)
}
#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 @@ static void rt_set_nexthop(struct rtable *rt, struct fib_result *res, u32 itag)
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