[NETFILTER]: nf_conntrack: use RCU for conntrack hash

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 71 insertions, 43 deletions

diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
index 2fdcd9233a03..0ee87edbd286 100644
--- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
+++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
@@ -39,12 +39,14 @@ struct ct_iter_state {
 static struct hlist_node *ct_get_first(struct seq_file *seq)
 {
         struct ct_iter_state *st = seq->private;
+        struct hlist_node *n;
 
         for (st->bucket = 0;
              st->bucket < nf_conntrack_htable_size;
              st->bucket++) {
-                if (!hlist_empty(&nf_conntrack_hash[st->bucket]))
-                        return nf_conntrack_hash[st->bucket].first;
+                n = rcu_dereference(nf_conntrack_hash[st->bucket].first);
+                if (n)
+                        return n;
         }
         return NULL;
 }
@@ -54,11 +56,11 @@ static struct hlist_node *ct_get_next(struct seq_file *seq,
 {
         struct ct_iter_state *st = seq->private;
 
-        head = head->next;
+        head = rcu_dereference(head->next);
         while (head == NULL) {
                 if (++st->bucket >= nf_conntrack_htable_size)
                         return NULL;
-                head = nf_conntrack_hash[st->bucket].first;
+                head = rcu_dereference(nf_conntrack_hash[st->bucket].first);
         }
         return head;
 }
@@ -74,8 +76,9 @@ static struct hlist_node *ct_get_idx(struct seq_file *seq, loff_t pos)
 }
 
 static void *ct_seq_start(struct seq_file *seq, loff_t *pos)
+        __acquires(RCU)
 {
-        read_lock_bh(&nf_conntrack_lock);
+        rcu_read_lock();
         return ct_get_idx(seq, *pos);
 }
 
@@ -86,8 +89,9 @@ static void *ct_seq_next(struct seq_file *s, void *v, loff_t *pos)
 }
 
 static void ct_seq_stop(struct seq_file *s, void *v)
+        __releases(RCU)
 {
-        read_unlock_bh(&nf_conntrack_lock);
+        rcu_read_unlock();
 }
 
 static int ct_seq_show(struct seq_file *s, void *v)
@@ -226,6 +230,7 @@ static struct hlist_node *ct_expect_get_idx(struct seq_file *seq, loff_t pos)
 }
 
 static void *exp_seq_start(struct seq_file *seq, loff_t *pos)
+        __acquires(RCU)
 {
         rcu_read_lock();
         return ct_expect_get_idx(seq, *pos);
@@ -238,6 +243,7 @@ static void *exp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 }
 
 static void exp_seq_stop(struct seq_file *seq, void *v)
+        __releases(RCU)
 {
         rcu_read_unlock();
 }
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 10256079e634..a54bfec61e79 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -166,8 +166,8 @@ static void
 clean_from_lists(struct nf_conn *ct)
 {
         pr_debug("clean_from_lists(%p)\n", ct);
-        hlist_del(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnode);
-        hlist_del(&ct->tuplehash[IP_CT_DIR_REPLY].hnode);
+        hlist_del_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnode);
+        hlist_del_rcu(&ct->tuplehash[IP_CT_DIR_REPLY].hnode);
 
         /* Destroy all pending expectations */
         nf_ct_remove_expectations(ct);
@@ -253,7 +253,7 @@ __nf_conntrack_find(const struct nf_conntrack_tuple *tuple,
         struct hlist_node *n;
         unsigned int hash = hash_conntrack(tuple);
 
-        hlist_for_each_entry(h, n, &nf_conntrack_hash[hash], hnode) {
+        hlist_for_each_entry_rcu(h, n, &nf_conntrack_hash[hash], hnode) {
                 if (nf_ct_tuplehash_to_ctrack(h) != ignored_conntrack &&
                     nf_ct_tuple_equal(tuple, &h->tuple)) {
                         NF_CT_STAT_INC(found);
@@ -271,12 +271,16 @@ struct nf_conntrack_tuple_hash *
 nf_conntrack_find_get(const struct nf_conntrack_tuple *tuple)
 {
         struct nf_conntrack_tuple_hash *h;
+        struct nf_conn *ct;
 
-        read_lock_bh(&nf_conntrack_lock);
+        rcu_read_lock();
         h = __nf_conntrack_find(tuple, NULL);
-        if (h)
-                atomic_inc(&nf_ct_tuplehash_to_ctrack(h)->ct_general.use);
-        read_unlock_bh(&nf_conntrack_lock);
+        if (h) {
+                ct = nf_ct_tuplehash_to_ctrack(h);
+                if (unlikely(!atomic_inc_not_zero(&ct->ct_general.use)))
+                        h = NULL;
+        }
+        rcu_read_unlock();
 
         return h;
 }
@@ -286,10 +290,10 @@ static void __nf_conntrack_hash_insert(struct nf_conn *ct,
                                        unsigned int hash,
                                        unsigned int repl_hash)
 {
-        hlist_add_head(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnode,
-                       &nf_conntrack_hash[hash]);
-        hlist_add_head(&ct->tuplehash[IP_CT_DIR_REPLY].hnode,
-                       &nf_conntrack_hash[repl_hash]);
+        hlist_add_head_rcu(&ct->tuplehash[IP_CT_DIR_ORIGINAL].hnode,
+                           &nf_conntrack_hash[hash]);
+        hlist_add_head_rcu(&ct->tuplehash[IP_CT_DIR_REPLY].hnode,
+                           &nf_conntrack_hash[repl_hash]);
 }
 
 void nf_conntrack_hash_insert(struct nf_conn *ct)
@@ -392,9 +396,9 @@ nf_conntrack_tuple_taken(const struct nf_conntrack_tuple *tuple,
 {
         struct nf_conntrack_tuple_hash *h;
 
-        read_lock_bh(&nf_conntrack_lock);
+        rcu_read_lock();
         h = __nf_conntrack_find(tuple, ignored_conntrack);
-        read_unlock_bh(&nf_conntrack_lock);
+        rcu_read_unlock();
 
         return h != NULL;
 }
@@ -413,21 +417,23 @@ static int early_drop(unsigned int hash)
         unsigned int i, cnt = 0;
         int dropped = 0;
 
-        read_lock_bh(&nf_conntrack_lock);
+        rcu_read_lock();
         for (i = 0; i < nf_conntrack_htable_size; i++) {
-                hlist_for_each_entry(h, n, &nf_conntrack_hash[hash], hnode) {
+                hlist_for_each_entry_rcu(h, n, &nf_conntrack_hash[hash],
+                                         hnode) {
                         tmp = nf_ct_tuplehash_to_ctrack(h);
                         if (!test_bit(IPS_ASSURED_BIT, &tmp->status))
                                 ct = tmp;
                         cnt++;
                 }
+
+                if (ct && unlikely(!atomic_inc_not_zero(&ct->ct_general.use)))
+                        ct = NULL;
                 if (ct || cnt >= NF_CT_EVICTION_RANGE)
                         break;
                 hash = (hash + 1) % nf_conntrack_htable_size;
         }
-        if (ct)
-                atomic_inc(&ct->ct_general.use);
-        read_unlock_bh(&nf_conntrack_lock);
+        rcu_read_unlock();
 
         if (!ct)
                 return dropped;
@@ -480,17 +486,25 @@ struct nf_conn *nf_conntrack_alloc(const struct nf_conntrack_tuple *orig,
         /* Don't set timer yet: wait for confirmation */
         setup_timer(&conntrack->timeout, death_by_timeout,
                     (unsigned long)conntrack);
+        INIT_RCU_HEAD(&conntrack->rcu);
 
         return conntrack;
 }
 EXPORT_SYMBOL_GPL(nf_conntrack_alloc);
 
-void nf_conntrack_free(struct nf_conn *conntrack)
+static void nf_conntrack_free_rcu(struct rcu_head *head)
 {
-        nf_ct_ext_free(conntrack);
-        kmem_cache_free(nf_conntrack_cachep, conntrack);
+        struct nf_conn *ct = container_of(head, struct nf_conn, rcu);
+
+        nf_ct_ext_free(ct);
+        kmem_cache_free(nf_conntrack_cachep, ct);
         atomic_dec(&nf_conntrack_count);
 }
+
+void nf_conntrack_free(struct nf_conn *conntrack)
+{
+        call_rcu(&conntrack->rcu, nf_conntrack_free_rcu);
+}
 EXPORT_SYMBOL_GPL(nf_conntrack_free);
 
 /* Allocate a new conntrack: we return -ENOMEM if classification
@@ -1036,12 +1050,17 @@ int nf_conntrack_set_hashsize(const char *val, struct kernel_param *kp)
          * use a newrandom seed */
         get_random_bytes(&rnd, 4);
 
+        /* 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.
+         */
         write_lock_bh(&nf_conntrack_lock);
         for (i = 0; i < nf_conntrack_htable_size; i++) {
                 while (!hlist_empty(&nf_conntrack_hash[i])) {
                         h = hlist_entry(nf_conntrack_hash[i].first,
                                         struct nf_conntrack_tuple_hash, hnode);
-                        hlist_del(&h->hnode);
+                        hlist_del_rcu(&h->hnode);
                         bucket = __hash_conntrack(&h->tuple, hashsize, rnd);
                         hlist_add_head(&h->hnode, &hash[bucket]);
                 }
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 557f47137da0..b701dcce0e69 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -545,12 +545,12 @@ ctnetlink_dump_table(struct sk_buff *skb, struct netlink_callback *cb)
         struct nfgenmsg *nfmsg = NLMSG_DATA(cb->nlh);
         u_int8_t l3proto = nfmsg->nfgen_family;
 
-        read_lock_bh(&nf_conntrack_lock);
+        rcu_read_lock();
         last = (struct nf_conn *)cb->args[1];
         for (; cb->args[0] < nf_conntrack_htable_size; cb->args[0]++) {
 restart:
-                hlist_for_each_entry(h, n, &nf_conntrack_hash[cb->args[0]],
-                                     hnode) {
+                hlist_for_each_entry_rcu(h, n, &nf_conntrack_hash[cb->args[0]],
+                                         hnode) {
                         if (NF_CT_DIRECTION(h) != IP_CT_DIR_ORIGINAL)
                                 continue;
                         ct = nf_ct_tuplehash_to_ctrack(h);
@@ -568,7 +568,8 @@ restart:
                                                 cb->nlh->nlmsg_seq,
                                                 IPCTNL_MSG_CT_NEW,
                                                 1, ct) < 0) {
-                                nf_conntrack_get(&ct->ct_general);
+                                if (!atomic_inc_not_zero(&ct->ct_general.use))
+                                        continue;
                                 cb->args[1] = (unsigned long)ct;
                                 goto out;
                         }
@@ -584,7 +585,7 @@ restart:
                 }
         }
 out:
-        read_unlock_bh(&nf_conntrack_lock);
+        rcu_read_unlock();
         if (last)
                 nf_ct_put(last);
 
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 28c5ae8f5625..98f0cd31150d 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -58,12 +58,14 @@ struct ct_iter_state {
 static struct hlist_node *ct_get_first(struct seq_file *seq)
 {
         struct ct_iter_state *st = seq->private;
+        struct hlist_node *n;
 
         for (st->bucket = 0;
              st->bucket < nf_conntrack_htable_size;
              st->bucket++) {
-                if (!hlist_empty(&nf_conntrack_hash[st->bucket]))
-                        return nf_conntrack_hash[st->bucket].first;
+                n = rcu_dereference(nf_conntrack_hash[st->bucket].first);
+                if (n)
+                        return n;
         }
         return NULL;
 }
@@ -73,11 +75,11 @@ static struct hlist_node *ct_get_next(struct seq_file *seq,
 {
         struct ct_iter_state *st = seq->private;
 
-        head = head->next;
+        head = rcu_dereference(head->next);
         while (head == NULL) {
                 if (++st->bucket >= nf_conntrack_htable_size)
                         return NULL;
-                head = nf_conntrack_hash[st->bucket].first;
+                head = rcu_dereference(nf_conntrack_hash[st->bucket].first);
         }
         return head;
 }
@@ -93,9 +95,9 @@ static struct hlist_node *ct_get_idx(struct seq_file *seq, loff_t pos)
 }
 
 static void *ct_seq_start(struct seq_file *seq, loff_t *pos)
-        __acquires(nf_conntrack_lock)
+        __acquires(RCU)
 {
-        read_lock_bh(&nf_conntrack_lock);
+        rcu_read_lock();
         return ct_get_idx(seq, *pos);
 }
 
@@ -106,9 +108,9 @@ static void *ct_seq_next(struct seq_file *s, void *v, loff_t *pos)
 }
 
 static void ct_seq_stop(struct seq_file *s, void *v)
-        __releases(nf_conntrack_lock)
+        __releases(RCU)
 {
-        read_unlock_bh(&nf_conntrack_lock);
+        rcu_read_unlock();
 }
 
 /* return 0 on success, 1 in case of error */
diff --git a/net/netfilter/xt_connlimit.c b/net/netfilter/xt_connlimit.c
index e00ecd974fa3..f9b59a6753ee 100644
--- a/net/netfilter/xt_connlimit.c
+++ b/net/netfilter/xt_connlimit.c
@@ -120,7 +120,7 @@ static int count_them(struct xt_connlimit_data *data,
         else
                 hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)];
 
-        read_lock_bh(&nf_conntrack_lock);
+        rcu_read_lock();
 
         /* check the saved connections */
         list_for_each_entry_safe(conn, tmp, hash, list) {
@@ -163,7 +163,7 @@ static int count_them(struct xt_connlimit_data *data,
                         ++matches;
         }
 
-        read_unlock_bh(&nf_conntrack_lock);
+        rcu_read_unlock();
 
         if (addit) {
                 /* save the new connection in our list */