From 93bb0ceb75be2fdfa9fc0dd1fb522d9ada515d9c Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Mon, 3 Mar 2014 14:46:13 +0100 Subject: netfilter: conntrack: remove central spinlock nf_conntrack_lock nf_conntrack_lock is a monolithic lock and suffers from huge contention on current generation servers (8 or more core/threads). Perf locking congestion is clear on base kernel: - 72.56% ksoftirqd/6 [kernel.kallsyms] [k] _raw_spin_lock_bh - _raw_spin_lock_bh + 25.33% init_conntrack + 24.86% nf_ct_delete_from_lists + 24.62% __nf_conntrack_confirm + 24.38% destroy_conntrack + 0.70% tcp_packet + 2.21% ksoftirqd/6 [kernel.kallsyms] [k] fib_table_lookup + 1.15% ksoftirqd/6 [kernel.kallsyms] [k] __slab_free + 0.77% ksoftirqd/6 [kernel.kallsyms] [k] inet_getpeer + 0.70% ksoftirqd/6 [nf_conntrack] [k] nf_ct_delete + 0.55% ksoftirqd/6 [ip_tables] [k] ipt_do_table This patch change conntrack locking and provides a huge performance improvement. SYN-flood attack tested on a 24-core E5-2695v2(ES) with 10Gbit/s ixgbe (with tool trafgen): Base kernel: 810.405 new conntrack/sec After patch: 2.233.876 new conntrack/sec Notice other floods attack (SYN+ACK or ACK) can easily be deflected using: # iptables -A INPUT -m state --state INVALID -j DROP # sysctl -w net/netfilter/nf_conntrack_tcp_loose=0 Use an array of hashed spinlocks to protect insertions/deletions of conntracks into the hash table. 1024 spinlocks seem to give good results, at minimal cost (4KB memory). Due to lockdep max depth, 1024 becomes 8 if CONFIG_LOCKDEP=y The hash resize is a bit tricky, because we need to take all locks in the array. A seqcount_t is used to synchronize the hash table users with the resizing process. Signed-off-by: Eric Dumazet Signed-off-by: Jesper Dangaard Brouer Signed-off-by: David S. Miller Reviewed-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_core.c | 219 +++++++++++++++++++++++++++----------- 1 file changed, 159 insertions(+), 60 deletions(-) (limited to 'net/netfilter/nf_conntrack_core.c') diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 4cdf1ade1530..5d1e7d126ebd 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -60,12 +60,60 @@ int (*nfnetlink_parse_nat_setup_hook)(struct nf_conn *ct, const struct nlattr *attr) __read_mostly; EXPORT_SYMBOL_GPL(nfnetlink_parse_nat_setup_hook); -DEFINE_SPINLOCK(nf_conntrack_lock); -EXPORT_SYMBOL_GPL(nf_conntrack_lock); +__cacheline_aligned_in_smp spinlock_t nf_conntrack_locks[CONNTRACK_LOCKS]; +EXPORT_SYMBOL_GPL(nf_conntrack_locks); __cacheline_aligned_in_smp DEFINE_SPINLOCK(nf_conntrack_expect_lock); EXPORT_SYMBOL_GPL(nf_conntrack_expect_lock); +static void nf_conntrack_double_unlock(unsigned int h1, unsigned int h2) +{ + h1 %= CONNTRACK_LOCKS; + h2 %= CONNTRACK_LOCKS; + spin_unlock(&nf_conntrack_locks[h1]); + if (h1 != h2) + spin_unlock(&nf_conntrack_locks[h2]); +} + +/* return true if we need to recompute hashes (in case hash table was resized) */ +static bool nf_conntrack_double_lock(struct net *net, unsigned int h1, + unsigned int h2, unsigned int sequence) +{ + h1 %= CONNTRACK_LOCKS; + h2 %= CONNTRACK_LOCKS; + if (h1 <= h2) { + spin_lock(&nf_conntrack_locks[h1]); + if (h1 != h2) + spin_lock_nested(&nf_conntrack_locks[h2], + SINGLE_DEPTH_NESTING); + } else { + spin_lock(&nf_conntrack_locks[h2]); + spin_lock_nested(&nf_conntrack_locks[h1], + SINGLE_DEPTH_NESTING); + } + if (read_seqcount_retry(&net->ct.generation, sequence)) { + nf_conntrack_double_unlock(h1, h2); + return true; + } + return false; +} + +static void nf_conntrack_all_lock(void) +{ + int i; + + for (i = 0; i < CONNTRACK_LOCKS; i++) + spin_lock_nested(&nf_conntrack_locks[i], i); +} + +static void nf_conntrack_all_unlock(void) +{ + int i; + + for (i = 0; i < CONNTRACK_LOCKS; i++) + spin_unlock(&nf_conntrack_locks[i]); +} + unsigned int nf_conntrack_htable_size __read_mostly; EXPORT_SYMBOL_GPL(nf_conntrack_htable_size); @@ -280,15 +328,28 @@ destroy_conntrack(struct nf_conntrack *nfct) static void nf_ct_delete_from_lists(struct nf_conn *ct) { struct net *net = nf_ct_net(ct); + unsigned int hash, reply_hash; + u16 zone = nf_ct_zone(ct); + unsigned int sequence; nf_ct_helper_destroy(ct); - spin_lock_bh(&nf_conntrack_lock); - /* Inside lock so preempt is disabled on module removal path. - * Otherwise we can get spurious warnings. */ - NF_CT_STAT_INC(net, delete_list); + + local_bh_disable(); + do { + sequence = read_seqcount_begin(&net->ct.generation); + hash = hash_conntrack(net, zone, + &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple); + reply_hash = hash_conntrack(net, zone, + &ct->tuplehash[IP_CT_DIR_REPLY].tuple); + } while (nf_conntrack_double_lock(net, hash, reply_hash, sequence)); + clean_from_lists(ct); + nf_conntrack_double_unlock(hash, reply_hash); + nf_ct_add_to_dying_list(ct); - spin_unlock_bh(&nf_conntrack_lock); + + NF_CT_STAT_INC(net, delete_list); + local_bh_enable(); } static void death_by_event(unsigned long ul_conntrack) @@ -372,8 +433,6 @@ nf_ct_key_equal(struct nf_conntrack_tuple_hash *h, * Warning : * - Caller must take a reference on returned object * and recheck nf_ct_tuple_equal(tuple, &h->tuple) - * OR - * - Caller must lock nf_conntrack_lock before calling this function */ static struct nf_conntrack_tuple_hash * ____nf_conntrack_find(struct net *net, u16 zone, @@ -467,14 +526,18 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct) struct nf_conntrack_tuple_hash *h; struct hlist_nulls_node *n; u16 zone; + unsigned int sequence; zone = nf_ct_zone(ct); - hash = hash_conntrack(net, zone, - &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple); - reply_hash = hash_conntrack(net, zone, - &ct->tuplehash[IP_CT_DIR_REPLY].tuple); - spin_lock_bh(&nf_conntrack_lock); + local_bh_disable(); + do { + sequence = read_seqcount_begin(&net->ct.generation); + hash = hash_conntrack(net, zone, + &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple); + reply_hash = hash_conntrack(net, zone, + &ct->tuplehash[IP_CT_DIR_REPLY].tuple); + } while (nf_conntrack_double_lock(net, hash, reply_hash, sequence)); /* See if there's one in the list already, including reverse */ hlist_nulls_for_each_entry(h, n, &net->ct.hash[hash], hnnode) @@ -493,14 +556,15 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct) /* The caller holds a reference to this object */ atomic_set(&ct->ct_general.use, 2); __nf_conntrack_hash_insert(ct, hash, reply_hash); + nf_conntrack_double_unlock(hash, reply_hash); NF_CT_STAT_INC(net, insert); - spin_unlock_bh(&nf_conntrack_lock); - + local_bh_enable(); return 0; out: + nf_conntrack_double_unlock(hash, reply_hash); NF_CT_STAT_INC(net, insert_failed); - spin_unlock_bh(&nf_conntrack_lock); + local_bh_enable(); return -EEXIST; } EXPORT_SYMBOL_GPL(nf_conntrack_hash_check_insert); @@ -540,6 +604,7 @@ __nf_conntrack_confirm(struct sk_buff *skb) enum ip_conntrack_info ctinfo; struct net *net; u16 zone; + unsigned int sequence; ct = nf_ct_get(skb, &ctinfo); net = nf_ct_net(ct); @@ -552,31 +617,37 @@ __nf_conntrack_confirm(struct sk_buff *skb) return NF_ACCEPT; zone = nf_ct_zone(ct); - /* reuse the hash saved before */ - hash = *(unsigned long *)&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev; - hash = hash_bucket(hash, net); - reply_hash = hash_conntrack(net, zone, - &ct->tuplehash[IP_CT_DIR_REPLY].tuple); + local_bh_disable(); + + do { + sequence = read_seqcount_begin(&net->ct.generation); + /* reuse the hash saved before */ + hash = *(unsigned long *)&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev; + hash = hash_bucket(hash, net); + reply_hash = hash_conntrack(net, zone, + &ct->tuplehash[IP_CT_DIR_REPLY].tuple); + + } while (nf_conntrack_double_lock(net, hash, reply_hash, sequence)); /* We're not in hash table, and we refuse to set up related - connections for unconfirmed conns. But packet copies and - REJECT will give spurious warnings here. */ + * connections for unconfirmed conns. But packet copies and + * REJECT will give spurious warnings here. + */ /* NF_CT_ASSERT(atomic_read(&ct->ct_general.use) == 1); */ /* No external references means no one else could have - confirmed us. */ + * confirmed us. + */ NF_CT_ASSERT(!nf_ct_is_confirmed(ct)); pr_debug("Confirming conntrack %p\n", ct); - - spin_lock_bh(&nf_conntrack_lock); - /* We have to check the DYING flag inside the lock to prevent a race against nf_ct_get_next_corpse() possibly called from user context, else we insert an already 'dead' hash, blocking further use of that particular connection -JM */ if (unlikely(nf_ct_is_dying(ct))) { - spin_unlock_bh(&nf_conntrack_lock); + nf_conntrack_double_unlock(hash, reply_hash); + local_bh_enable(); return NF_ACCEPT; } @@ -618,8 +689,9 @@ __nf_conntrack_confirm(struct sk_buff *skb) * stores are visible. */ __nf_conntrack_hash_insert(ct, hash, reply_hash); + nf_conntrack_double_unlock(hash, reply_hash); NF_CT_STAT_INC(net, insert); - spin_unlock_bh(&nf_conntrack_lock); + local_bh_enable(); help = nfct_help(ct); if (help && help->helper) @@ -630,8 +702,9 @@ __nf_conntrack_confirm(struct sk_buff *skb) return NF_ACCEPT; out: + nf_conntrack_double_unlock(hash, reply_hash); NF_CT_STAT_INC(net, insert_failed); - spin_unlock_bh(&nf_conntrack_lock); + local_bh_enable(); return NF_DROP; } EXPORT_SYMBOL_GPL(__nf_conntrack_confirm); @@ -674,39 +747,48 @@ EXPORT_SYMBOL_GPL(nf_conntrack_tuple_taken); /* There's a small race here where we may free a just-assured connection. Too bad: we're in trouble anyway. */ -static noinline int early_drop(struct net *net, unsigned int hash) +static noinline int early_drop(struct net *net, unsigned int _hash) { /* Use oldest entry, which is roughly LRU */ struct nf_conntrack_tuple_hash *h; struct nf_conn *ct = NULL, *tmp; struct hlist_nulls_node *n; - unsigned int i, cnt = 0; + unsigned int i = 0, cnt = 0; int dropped = 0; + unsigned int hash, sequence; + spinlock_t *lockp; - rcu_read_lock(); - for (i = 0; i < net->ct.htable_size; i++) { + local_bh_disable(); +restart: + sequence = read_seqcount_begin(&net->ct.generation); + hash = hash_bucket(_hash, net); + for (; i < net->ct.htable_size; i++) { + lockp = &nf_conntrack_locks[hash % CONNTRACK_LOCKS]; + spin_lock(lockp); + if (read_seqcount_retry(&net->ct.generation, sequence)) { + spin_unlock(lockp); + goto restart; + } hlist_nulls_for_each_entry_rcu(h, n, &net->ct.hash[hash], hnnode) { tmp = nf_ct_tuplehash_to_ctrack(h); - if (!test_bit(IPS_ASSURED_BIT, &tmp->status)) + if (!test_bit(IPS_ASSURED_BIT, &tmp->status) && + !nf_ct_is_dying(tmp) && + atomic_inc_not_zero(&tmp->ct_general.use)) { ct = tmp; + break; + } cnt++; } - if (ct != NULL) { - if (likely(!nf_ct_is_dying(ct) && - atomic_inc_not_zero(&ct->ct_general.use))) - break; - else - ct = NULL; - } + hash = (hash + 1) % net->ct.htable_size; + spin_unlock(lockp); - if (cnt >= NF_CT_EVICTION_RANGE) + if (ct || cnt >= NF_CT_EVICTION_RANGE) break; - hash = (hash + 1) % net->ct.htable_size; } - rcu_read_unlock(); + local_bh_enable(); if (!ct) return dropped; @@ -755,7 +837,7 @@ __nf_conntrack_alloc(struct net *net, u16 zone, if (nf_conntrack_max && unlikely(atomic_read(&net->ct.count) > nf_conntrack_max)) { - if (!early_drop(net, hash_bucket(hash, net))) { + if (!early_drop(net, hash)) { atomic_dec(&net->ct.count); net_warn_ratelimited("nf_conntrack: table full, dropping packet\n"); return ERR_PTR(-ENOMEM); @@ -1304,18 +1386,24 @@ get_next_corpse(struct net *net, int (*iter)(struct nf_conn *i, void *data), struct nf_conn *ct; struct hlist_nulls_node *n; int cpu; + spinlock_t *lockp; - spin_lock_bh(&nf_conntrack_lock); for (; *bucket < net->ct.htable_size; (*bucket)++) { - hlist_nulls_for_each_entry(h, n, &net->ct.hash[*bucket], hnnode) { - if (NF_CT_DIRECTION(h) != IP_CT_DIR_ORIGINAL) - continue; - ct = nf_ct_tuplehash_to_ctrack(h); - if (iter(ct, data)) - goto found; + lockp = &nf_conntrack_locks[*bucket % CONNTRACK_LOCKS]; + local_bh_disable(); + spin_lock(lockp); + if (*bucket < net->ct.htable_size) { + hlist_nulls_for_each_entry(h, n, &net->ct.hash[*bucket], hnnode) { + if (NF_CT_DIRECTION(h) != IP_CT_DIR_ORIGINAL) + continue; + ct = nf_ct_tuplehash_to_ctrack(h); + if (iter(ct, data)) + goto found; + } } + spin_unlock(lockp); + local_bh_enable(); } - spin_unlock_bh(&nf_conntrack_lock); for_each_possible_cpu(cpu) { struct ct_pcpu *pcpu = per_cpu_ptr(net->ct.pcpu_lists, cpu); @@ -1331,7 +1419,8 @@ get_next_corpse(struct net *net, int (*iter)(struct nf_conn *i, void *data), return NULL; found: atomic_inc(&ct->ct_general.use); - spin_unlock_bh(&nf_conntrack_lock); + spin_unlock(lockp); + local_bh_enable(); return ct; } @@ -1532,12 +1621,16 @@ int nf_conntrack_set_hashsize(const char *val, struct kernel_param *kp) if (!hash) return -ENOMEM; + local_bh_disable(); + nf_conntrack_all_lock(); + write_seqcount_begin(&init_net.ct.generation); + /* Lookups in the old hash might happen in parallel, which means we * might get false negatives during connection lookup. New connections * created because of a false negative won't make it into the hash - * though since that required taking the lock. + * though since that required taking the locks. */ - spin_lock_bh(&nf_conntrack_lock); + for (i = 0; i < init_net.ct.htable_size; i++) { while (!hlist_nulls_empty(&init_net.ct.hash[i])) { h = hlist_nulls_entry(init_net.ct.hash[i].first, @@ -1554,7 +1647,10 @@ int nf_conntrack_set_hashsize(const char *val, struct kernel_param *kp) init_net.ct.htable_size = nf_conntrack_htable_size = hashsize; init_net.ct.hash = hash; - spin_unlock_bh(&nf_conntrack_lock); + + write_seqcount_end(&init_net.ct.generation); + nf_conntrack_all_unlock(); + local_bh_enable(); nf_ct_free_hashtable(old_hash, old_size); return 0; @@ -1576,7 +1672,10 @@ EXPORT_SYMBOL_GPL(nf_ct_untracked_status_or); int nf_conntrack_init_start(void) { int max_factor = 8; - int ret, cpu; + int i, ret, cpu; + + for (i = 0; i < ARRAY_SIZE(nf_conntrack_locks); i++) + spin_lock_init(&nf_conntrack_locks[i]); /* Idea from tcp.c: use 1/16384 of memory. On i386: 32MB * machine has 512 buckets. >= 1GB machines have 16384 buckets. */ -- cgit v1.2.3-55-g7522