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ipv4: Cache learned PMTU information in inetpeer.
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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   it is out of date, instead of killing the cached route.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 invalidated in these
   situations.

2) rt_check_expire(), rt_worker_func(), et al. are no longer
   necessary at all.

Signed-off-by: David S. Miller <[email protected]>
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@davem330
davem330 committed Feb 15, 2011
1 parent d606ef3 commit 2c8cec5
Showing 1 changed file with 86 additions and 174 deletions.
260 changes: 86 additions & 174 deletions net/ipv4/route.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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.
*/
Expand Down Expand Up @@ -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)
Expand All @@ -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;
Expand Down Expand Up @@ -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()
Expand Down Expand Up @@ -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)));
Expand All @@ -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;
Expand Down Expand Up @@ -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);
}
}

Expand All @@ -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;
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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
Expand Down

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