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Message-Id: <20110209.221336.115936680.davem@davemloft.net>
Date: Wed, 09 Feb 2011 22:13:36 -0800 (PST)
From: David Miller <davem@...emloft.net>
To: netdev@...r.kernel.org
Subject: [RFC PATCH 4/5] ipv4: Cache learned PMTU information in inetpeer.
The general idea is that if we learn new PMTU information, we
bump the peer genid.
This triggers the dst_ops->check() code to validate and if
necessary propagate the new PMTU value into the metrics.
Learned PMTU information self-expires.
This means that it is not necessary to kill a cached route
entry just because the PMTU information is too old.
As a consequence:
1) When the path appears unreachable (dst_ops->link_failure
or dst_ops->negative_advice) we unwind the PMTU state if
it is out of date, instead of killing the cached route.
A redirected route will still be invlidated in these
situations.
2) rt_check_expire(), rt_worker_func(), et al. are no longer
necessary at all.
Signed-off-by: David S. Miller <davem@...emloft.net>
---
net/ipv4/route.c | 260 ++++++++++++++++++------------------------------------
1 files changed, 86 insertions(+), 174 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 0979e03..11faf14 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -131,9 +131,6 @@ static int ip_rt_min_pmtu __read_mostly = 512 + 20 + 20;
static int ip_rt_min_advmss __read_mostly = 256;
static int rt_chain_length_max __read_mostly = 20;
-static struct delayed_work expires_work;
-static unsigned long expires_ljiffies;
-
/*
* Interface to generic destination cache.
*/
@@ -668,7 +665,7 @@ static inline int rt_fast_clean(struct rtable *rth)
static inline int rt_valuable(struct rtable *rth)
{
return (rth->rt_flags & (RTCF_REDIRECTED | RTCF_NOTIFY)) ||
- rth->dst.expires;
+ (rth->peer && rth->peer->pmtu_expires);
}
static int rt_may_expire(struct rtable *rth, unsigned long tmo1, unsigned long tmo2)
@@ -679,13 +676,7 @@ static int rt_may_expire(struct rtable *rth, unsigned long tmo1, unsigned long t
if (atomic_read(&rth->dst.__refcnt))
goto out;
- ret = 1;
- if (rth->dst.expires &&
- time_after_eq(jiffies, rth->dst.expires))
- goto out;
-
age = jiffies - rth->dst.lastuse;
- ret = 0;
if ((age <= tmo1 && !rt_fast_clean(rth)) ||
(age <= tmo2 && rt_valuable(rth)))
goto out;
@@ -829,97 +820,6 @@ static int has_noalias(const struct rtable *head, const struct rtable *rth)
return ONE;
}
-static void rt_check_expire(void)
-{
- static unsigned int rover;
- unsigned int i = rover, goal;
- struct rtable *rth;
- struct rtable __rcu **rthp;
- unsigned long samples = 0;
- unsigned long sum = 0, sum2 = 0;
- unsigned long delta;
- u64 mult;
-
- delta = jiffies - expires_ljiffies;
- expires_ljiffies = jiffies;
- mult = ((u64)delta) << rt_hash_log;
- if (ip_rt_gc_timeout > 1)
- do_div(mult, ip_rt_gc_timeout);
- goal = (unsigned int)mult;
- if (goal > rt_hash_mask)
- goal = rt_hash_mask + 1;
- for (; goal > 0; goal--) {
- unsigned long tmo = ip_rt_gc_timeout;
- unsigned long length;
-
- i = (i + 1) & rt_hash_mask;
- rthp = &rt_hash_table[i].chain;
-
- if (need_resched())
- cond_resched();
-
- samples++;
-
- if (rcu_dereference_raw(*rthp) == NULL)
- continue;
- length = 0;
- spin_lock_bh(rt_hash_lock_addr(i));
- while ((rth = rcu_dereference_protected(*rthp,
- lockdep_is_held(rt_hash_lock_addr(i)))) != NULL) {
- prefetch(rth->dst.rt_next);
- if (rt_is_expired(rth)) {
- *rthp = rth->dst.rt_next;
- rt_free(rth);
- continue;
- }
- if (rth->dst.expires) {
- /* Entry is expired even if it is in use */
- if (time_before_eq(jiffies, rth->dst.expires)) {
-nofree:
- tmo >>= 1;
- rthp = &rth->dst.rt_next;
- /*
- * We only count entries on
- * a chain with equal hash inputs once
- * so that entries for different QOS
- * levels, and other non-hash input
- * attributes don't unfairly skew
- * the length computation
- */
- length += has_noalias(rt_hash_table[i].chain, rth);
- continue;
- }
- } else if (!rt_may_expire(rth, tmo, ip_rt_gc_timeout))
- goto nofree;
-
- /* Cleanup aged off entries. */
- *rthp = rth->dst.rt_next;
- rt_free(rth);
- }
- spin_unlock_bh(rt_hash_lock_addr(i));
- sum += length;
- sum2 += length*length;
- }
- if (samples) {
- unsigned long avg = sum / samples;
- unsigned long sd = int_sqrt(sum2 / samples - avg*avg);
- rt_chain_length_max = max_t(unsigned long,
- ip_rt_gc_elasticity,
- (avg + 4*sd) >> FRACT_BITS);
- }
- rover = i;
-}
-
-/*
- * rt_worker_func() is run in process context.
- * we call rt_check_expire() to scan part of the hash table
- */
-static void rt_worker_func(struct work_struct *work)
-{
- rt_check_expire();
- schedule_delayed_work(&expires_work, ip_rt_gc_interval);
-}
-
/*
* Pertubation of rt_genid by a small quantity [1..256]
* Using 8 bits of shuffling ensure we can call rt_cache_invalidate()
@@ -1535,9 +1435,7 @@ static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst)
if (dst->obsolete > 0) {
ip_rt_put(rt);
ret = NULL;
- } else if ((rt->rt_flags & RTCF_REDIRECTED) ||
- (rt->dst.expires &&
- time_after_eq(jiffies, rt->dst.expires))) {
+ } else if (rt->rt_flags & RTCF_REDIRECTED) {
unsigned hash = rt_hash(rt->fl.fl4_dst, rt->fl.fl4_src,
rt->fl.oif,
rt_genid(dev_net(dst->dev)));
@@ -1547,6 +1445,14 @@ static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst)
#endif
rt_del(hash, rt);
ret = NULL;
+ } else if (rt->peer &&
+ rt->peer->pmtu_expires &&
+ time_after_eq(jiffies, rt->peer->pmtu_expires)) {
+ unsigned long orig = rt->peer->pmtu_expires;
+
+ if (cmpxchg(&rt->peer->pmtu_expires, orig, 0) == orig)
+ dst_metric_set(dst, RTAX_MTU,
+ rt->peer->pmtu_orig);
}
}
return ret;
@@ -1697,80 +1603,78 @@ unsigned short ip_rt_frag_needed(struct net *net, struct iphdr *iph,
unsigned short new_mtu,
struct net_device *dev)
{
- int i, k;
unsigned short old_mtu = ntohs(iph->tot_len);
- struct rtable *rth;
- int ikeys[2] = { dev->ifindex, 0 };
- __be32 skeys[2] = { iph->saddr, 0, };
- __be32 daddr = iph->daddr;
unsigned short est_mtu = 0;
+ struct inet_peer *peer;
- for (k = 0; k < 2; k++) {
- for (i = 0; i < 2; i++) {
- unsigned hash = rt_hash(daddr, skeys[i], ikeys[k],
- rt_genid(net));
-
- rcu_read_lock();
- for (rth = rcu_dereference(rt_hash_table[hash].chain); rth;
- rth = rcu_dereference(rth->dst.rt_next)) {
- unsigned short mtu = new_mtu;
+ peer = inet_getpeer_v4(iph->daddr, 1);
+ if (peer) {
+ unsigned short mtu = new_mtu;
- if (rth->fl.fl4_dst != daddr ||
- rth->fl.fl4_src != skeys[i] ||
- rth->rt_dst != daddr ||
- rth->rt_src != iph->saddr ||
- rth->fl.oif != ikeys[k] ||
- rt_is_input_route(rth) ||
- dst_metric_locked(&rth->dst, RTAX_MTU) ||
- !net_eq(dev_net(rth->dst.dev), net) ||
- rt_is_expired(rth))
- continue;
+ if (new_mtu < 68 || new_mtu >= old_mtu) {
+ /* BSD 4.2 derived systems incorrectly adjust
+ * tot_len by the IP header length, and report
+ * a zero MTU in the ICMP message.
+ */
+ if (mtu == 0 &&
+ old_mtu >= 68 + (iph->ihl << 2))
+ old_mtu -= iph->ihl << 2;
+ mtu = guess_mtu(old_mtu);
+ }
- if (new_mtu < 68 || new_mtu >= old_mtu) {
+ if (mtu < ip_rt_min_pmtu)
+ mtu = ip_rt_min_pmtu;
+ if (!peer->pmtu_expires || mtu < peer->pmtu_learned) {
+ est_mtu = mtu;
+ peer->pmtu_learned = mtu;
+ peer->pmtu_expires = jiffies + ip_rt_mtu_expires;
+ }
- /* BSD 4.2 compatibility hack :-( */
- if (mtu == 0 &&
- old_mtu >= dst_mtu(&rth->dst) &&
- old_mtu >= 68 + (iph->ihl << 2))
- old_mtu -= iph->ihl << 2;
+ inet_putpeer(peer);
- mtu = guess_mtu(old_mtu);
- }
- if (mtu <= dst_mtu(&rth->dst)) {
- if (mtu < dst_mtu(&rth->dst)) {
- dst_confirm(&rth->dst);
- if (mtu < ip_rt_min_pmtu) {
- u32 lock = dst_metric(&rth->dst,
- RTAX_LOCK);
- mtu = ip_rt_min_pmtu;
- lock |= (1 << RTAX_MTU);
- dst_metric_set(&rth->dst, RTAX_LOCK,
- lock);
- }
- dst_metric_set(&rth->dst, RTAX_MTU, mtu);
- dst_set_expires(&rth->dst,
- ip_rt_mtu_expires);
- }
- est_mtu = mtu;
- }
- }
- rcu_read_unlock();
- }
+ atomic_inc(&__rt_peer_genid);
}
return est_mtu ? : new_mtu;
}
+static void check_peer_pmtu(struct dst_entry *dst, struct inet_peer *peer)
+{
+ unsigned long expires = peer->pmtu_expires;
+
+ if (time_before(expires, jiffies)) {
+ u32 orig_dst_mtu = dst_mtu(dst);
+ if (peer->pmtu_learned < orig_dst_mtu) {
+ if (!peer->pmtu_orig)
+ peer->pmtu_orig = dst_metric_raw(dst, RTAX_MTU);
+ dst_metric_set(dst, RTAX_MTU, peer->pmtu_learned);
+ }
+ } else if (cmpxchg(&peer->pmtu_expires, expires, 0) == expires)
+ dst_metric_set(dst, RTAX_MTU, peer->pmtu_orig);
+}
+
static void ip_rt_update_pmtu(struct dst_entry *dst, u32 mtu)
{
- if (dst_mtu(dst) > mtu && mtu >= 68 &&
- !(dst_metric_locked(dst, RTAX_MTU))) {
- if (mtu < ip_rt_min_pmtu) {
- u32 lock = dst_metric(dst, RTAX_LOCK);
+ struct rtable *rt = (struct rtable *) dst;
+ struct inet_peer *peer;
+
+ dst_confirm(dst);
+
+ if (!rt->peer)
+ rt_bind_peer(rt, 1);
+ peer = rt->peer;
+ if (peer) {
+ if (mtu < ip_rt_min_pmtu)
mtu = ip_rt_min_pmtu;
- dst_metric_set(dst, RTAX_LOCK, lock | (1 << RTAX_MTU));
+ if (!peer->pmtu_expires || mtu < peer->pmtu_learned) {
+ peer->pmtu_learned = mtu;
+ peer->pmtu_expires = jiffies + ip_rt_mtu_expires;
+
+ atomic_inc(&__rt_peer_genid);
+ rt->rt_peer_genid = rt_peer_genid();
+
+ check_peer_pmtu(dst, peer);
}
- dst_metric_set(dst, RTAX_MTU, mtu);
- dst_set_expires(dst, ip_rt_mtu_expires);
+ inet_putpeer(peer);
}
}
@@ -1781,9 +1685,15 @@ static struct dst_entry *ipv4_dst_check(struct dst_entry *dst, u32 cookie)
if (rt_is_expired(rt))
return NULL;
if (rt->rt_peer_genid != rt_peer_genid()) {
+ struct inet_peer *peer;
+
if (!rt->peer)
rt_bind_peer(rt, 0);
+ peer = rt->peer;
+ if (peer && peer->pmtu_expires)
+ check_peer_pmtu(dst, peer);
+
rt->rt_peer_genid = rt_peer_genid();
}
return dst;
@@ -1812,8 +1722,14 @@ static void ipv4_link_failure(struct sk_buff *skb)
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0);
rt = skb_rtable(skb);
- if (rt)
- dst_set_expires(&rt->dst, 0);
+ if (rt &&
+ rt->peer &&
+ rt->peer->pmtu_expires) {
+ unsigned long orig = rt->peer->pmtu_expires;
+
+ if (cmpxchg(&rt->peer->pmtu_expires, orig, 0) == orig)
+ dst_metric_set(&rt->dst, RTAX_MTU, rt->peer->pmtu_orig);
+ }
}
static int ip_rt_bug(struct sk_buff *skb)
@@ -1911,6 +1827,9 @@ static void rt_init_metrics(struct rtable *rt, struct fib_info *fi)
memcpy(peer->metrics, fi->fib_metrics,
sizeof(u32) * RTAX_MAX);
dst_init_metrics(&rt->dst, peer->metrics, false);
+
+ if (peer->pmtu_expires)
+ check_peer_pmtu(&rt->dst, peer);
} else {
if (fi->fib_metrics != (u32 *) dst_default_metrics) {
rt->fi = fi;
@@ -2961,7 +2880,8 @@ static int rt_fill_info(struct net *net,
NLA_PUT_BE32(skb, RTA_MARK, rt->fl.mark);
error = rt->dst.error;
- expires = rt->dst.expires ? rt->dst.expires - jiffies : 0;
+ expires = (rt->peer && rt->peer->pmtu_expires) ?
+ rt->peer->pmtu_expires - jiffies : 0;
if (rt->peer) {
inet_peer_refcheck(rt->peer);
id = atomic_read(&rt->peer->ip_id_count) & 0xffff;
@@ -3418,14 +3338,6 @@ int __init ip_rt_init(void)
devinet_init();
ip_fib_init();
- /* All the timers, started at system startup tend
- to synchronize. Perturb it a bit.
- */
- INIT_DELAYED_WORK_DEFERRABLE(&expires_work, rt_worker_func);
- expires_ljiffies = jiffies;
- schedule_delayed_work(&expires_work,
- net_random() % ip_rt_gc_interval + ip_rt_gc_interval);
-
if (ip_rt_proc_init())
printk(KERN_ERR "Unable to create route proc files\n");
#ifdef CONFIG_XFRM
--
1.7.4
--
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