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Subject[PATCH 4.19 10/99] netfilter: nf_conncount: merge lookup and add functions
Date
4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Westphal <fw@strlen.de>

commit df4a902509766897f7371fdfa4c3bf8bc321b55d upstream.

'lookup' is always followed by 'add'.
Merge both and make the list-walk part of nf_conncount_add().

This also avoids one unneeded unlock/re-lock pair.

Extra care needs to be taken in count_tree, as we only hold rcu
read lock, i.e. we can only insert to an existing tree node after
acquiring its lock and making sure it has a nonzero count.

As a zero count should be rare, just fall back to insert_tree()
(which acquires tree lock).

This issue and its solution were pointed out by Shawn Bohrer
during patch review.

Reviewed-by: Shawn Bohrer <sbohrer@cloudflare.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/net/netfilter/nf_conntrack_count.h | 18 ---
net/netfilter/nf_conncount.c | 146 +++++++++++++----------------
net/netfilter/nft_connlimit.c | 14 --
3 files changed, 72 insertions(+), 106 deletions(-)

--- a/include/net/netfilter/nf_conntrack_count.h
+++ b/include/net/netfilter/nf_conntrack_count.h
@@ -5,12 +5,6 @@

struct nf_conncount_data;

-enum nf_conncount_list_add {
- NF_CONNCOUNT_ADDED, /* list add was ok */
- NF_CONNCOUNT_ERR, /* -ENOMEM, must drop skb */
- NF_CONNCOUNT_SKIP, /* list is already reclaimed by gc */
-};
-
struct nf_conncount_list {
spinlock_t list_lock;
struct list_head head; /* connections with the same filtering key */
@@ -29,18 +23,12 @@ unsigned int nf_conncount_count(struct n
const struct nf_conntrack_tuple *tuple,
const struct nf_conntrack_zone *zone);

-void nf_conncount_lookup(struct net *net, struct nf_conncount_list *list,
- const struct nf_conntrack_tuple *tuple,
- const struct nf_conntrack_zone *zone,
- bool *addit);
+int nf_conncount_add(struct net *net, struct nf_conncount_list *list,
+ const struct nf_conntrack_tuple *tuple,
+ const struct nf_conntrack_zone *zone);

void nf_conncount_list_init(struct nf_conncount_list *list);

-enum nf_conncount_list_add
-nf_conncount_add(struct nf_conncount_list *list,
- const struct nf_conntrack_tuple *tuple,
- const struct nf_conntrack_zone *zone);
-
bool nf_conncount_gc_list(struct net *net,
struct nf_conncount_list *list);

--- a/net/netfilter/nf_conncount.c
+++ b/net/netfilter/nf_conncount.c
@@ -83,38 +83,6 @@ static int key_diff(const u32 *a, const
return memcmp(a, b, klen * sizeof(u32));
}

-enum nf_conncount_list_add
-nf_conncount_add(struct nf_conncount_list *list,
- const struct nf_conntrack_tuple *tuple,
- const struct nf_conntrack_zone *zone)
-{
- struct nf_conncount_tuple *conn;
-
- if (WARN_ON_ONCE(list->count > INT_MAX))
- return NF_CONNCOUNT_ERR;
-
- conn = kmem_cache_alloc(conncount_conn_cachep, GFP_ATOMIC);
- if (conn == NULL)
- return NF_CONNCOUNT_ERR;
-
- conn->tuple = *tuple;
- conn->zone = *zone;
- conn->cpu = raw_smp_processor_id();
- conn->jiffies32 = (u32)jiffies;
- conn->dead = false;
- spin_lock_bh(&list->list_lock);
- if (list->dead == true) {
- kmem_cache_free(conncount_conn_cachep, conn);
- spin_unlock_bh(&list->list_lock);
- return NF_CONNCOUNT_SKIP;
- }
- list_add_tail(&conn->node, &list->head);
- list->count++;
- spin_unlock_bh(&list->list_lock);
- return NF_CONNCOUNT_ADDED;
-}
-EXPORT_SYMBOL_GPL(nf_conncount_add);
-
static void __conn_free(struct rcu_head *h)
{
struct nf_conncount_tuple *conn;
@@ -177,11 +145,10 @@ find_or_evict(struct net *net, struct nf
return ERR_PTR(-EAGAIN);
}

-void nf_conncount_lookup(struct net *net,
- struct nf_conncount_list *list,
- const struct nf_conntrack_tuple *tuple,
- const struct nf_conntrack_zone *zone,
- bool *addit)
+static int __nf_conncount_add(struct net *net,
+ struct nf_conncount_list *list,
+ const struct nf_conntrack_tuple *tuple,
+ const struct nf_conntrack_zone *zone)
{
const struct nf_conntrack_tuple_hash *found;
struct nf_conncount_tuple *conn, *conn_n;
@@ -189,9 +156,6 @@ void nf_conncount_lookup(struct net *net
unsigned int collect = 0;
bool free_entry = false;

- /* best effort only */
- *addit = tuple ? true : false;
-
/* check the saved connections */
list_for_each_entry_safe(conn, conn_n, &list->head, node) {
if (collect > CONNCOUNT_GC_MAX_NODES)
@@ -201,21 +165,19 @@ void nf_conncount_lookup(struct net *net
if (IS_ERR(found)) {
/* Not found, but might be about to be confirmed */
if (PTR_ERR(found) == -EAGAIN) {
- if (!tuple)
- continue;
-
if (nf_ct_tuple_equal(&conn->tuple, tuple) &&
nf_ct_zone_id(&conn->zone, conn->zone.dir) ==
nf_ct_zone_id(zone, zone->dir))
- *addit = false;
- } else if (PTR_ERR(found) == -ENOENT)
+ return 0; /* already exists */
+ } else {
collect++;
+ }
continue;
}

found_ct = nf_ct_tuplehash_to_ctrack(found);

- if (tuple && nf_ct_tuple_equal(&conn->tuple, tuple) &&
+ if (nf_ct_tuple_equal(&conn->tuple, tuple) &&
nf_ct_zone_equal(found_ct, zone, zone->dir)) {
/*
* We should not see tuples twice unless someone hooks
@@ -223,7 +185,8 @@ void nf_conncount_lookup(struct net *net
*
* Attempt to avoid a re-add in this case.
*/
- *addit = false;
+ nf_ct_put(found_ct);
+ return 0;
} else if (already_closed(found_ct)) {
/*
* we do not care about connections which are
@@ -237,8 +200,38 @@ void nf_conncount_lookup(struct net *net

nf_ct_put(found_ct);
}
+
+ if (WARN_ON_ONCE(list->count > INT_MAX))
+ return -EOVERFLOW;
+
+ conn = kmem_cache_alloc(conncount_conn_cachep, GFP_ATOMIC);
+ if (conn == NULL)
+ return -ENOMEM;
+
+ conn->tuple = *tuple;
+ conn->zone = *zone;
+ conn->cpu = raw_smp_processor_id();
+ conn->jiffies32 = (u32)jiffies;
+ list_add_tail(&conn->node, &list->head);
+ list->count++;
+ return 0;
+}
+
+int nf_conncount_add(struct net *net,
+ struct nf_conncount_list *list,
+ const struct nf_conntrack_tuple *tuple,
+ const struct nf_conntrack_zone *zone)
+{
+ int ret;
+
+ /* check the saved connections */
+ spin_lock_bh(&list->list_lock);
+ ret = __nf_conncount_add(net, list, tuple, zone);
+ spin_unlock_bh(&list->list_lock);
+
+ return ret;
}
-EXPORT_SYMBOL_GPL(nf_conncount_lookup);
+EXPORT_SYMBOL_GPL(nf_conncount_add);

void nf_conncount_list_init(struct nf_conncount_list *list)
{
@@ -339,13 +332,11 @@ insert_tree(struct net *net,
const struct nf_conntrack_tuple *tuple,
const struct nf_conntrack_zone *zone)
{
- enum nf_conncount_list_add ret;
struct nf_conncount_rb *gc_nodes[CONNCOUNT_GC_MAX_NODES];
struct rb_node **rbnode, *parent;
struct nf_conncount_rb *rbconn;
struct nf_conncount_tuple *conn;
unsigned int count = 0, gc_count = 0;
- bool node_found = false;
bool do_gc = true;

spin_lock_bh(&nf_conncount_locks[hash]);
@@ -363,20 +354,15 @@ restart:
} else if (diff > 0) {
rbnode = &((*rbnode)->rb_right);
} else {
- /* unlikely: other cpu added node already */
- node_found = true;
- ret = nf_conncount_add(&rbconn->list, tuple, zone);
- if (ret == NF_CONNCOUNT_ERR) {
+ int ret;
+
+ ret = nf_conncount_add(net, &rbconn->list, tuple, zone);
+ if (ret)
count = 0; /* hotdrop */
- } else if (ret == NF_CONNCOUNT_ADDED) {
+ else
count = rbconn->list.count;
- } else {
- /* NF_CONNCOUNT_SKIP, rbconn is already
- * reclaimed by gc, insert a new tree node
- */
- node_found = false;
- }
- break;
+ tree_nodes_free(root, gc_nodes, gc_count);
+ goto out_unlock;
}

if (gc_count >= ARRAY_SIZE(gc_nodes))
@@ -394,9 +380,6 @@ restart:
goto restart;
}

- if (node_found)
- goto out_unlock;
-
/* expected case: match, insert new node */
rbconn = kmem_cache_alloc(conncount_rb_cachep, GFP_ATOMIC);
if (rbconn == NULL)
@@ -431,7 +414,6 @@ count_tree(struct net *net,
const struct nf_conntrack_tuple *tuple,
const struct nf_conntrack_zone *zone)
{
- enum nf_conncount_list_add ret;
struct rb_root *root;
struct rb_node *parent;
struct nf_conncount_rb *rbconn;
@@ -444,7 +426,6 @@ count_tree(struct net *net,
parent = rcu_dereference_raw(root->rb_node);
while (parent) {
int diff;
- bool addit;

rbconn = rb_entry(parent, struct nf_conncount_rb, node);

@@ -454,24 +435,29 @@ count_tree(struct net *net,
} else if (diff > 0) {
parent = rcu_dereference_raw(parent->rb_right);
} else {
- /* same source network -> be counted! */
- nf_conncount_lookup(net, &rbconn->list, tuple, zone,
- &addit);
+ int ret;

- if (!addit)
+ if (!tuple) {
+ nf_conncount_gc_list(net, &rbconn->list);
return rbconn->list.count;
+ }

- ret = nf_conncount_add(&rbconn->list, tuple, zone);
- if (ret == NF_CONNCOUNT_ERR) {
- return 0; /* hotdrop */
- } else if (ret == NF_CONNCOUNT_ADDED) {
- return rbconn->list.count;
- } else {
- /* NF_CONNCOUNT_SKIP, rbconn is already
- * reclaimed by gc, insert a new tree node
- */
+ spin_lock_bh(&rbconn->list.list_lock);
+ /* Node might be about to be free'd.
+ * We need to defer to insert_tree() in this case.
+ */
+ if (rbconn->list.count == 0) {
+ spin_unlock_bh(&rbconn->list.list_lock);
break;
}
+
+ /* same source network -> be counted! */
+ ret = __nf_conncount_add(net, &rbconn->list, tuple, zone);
+ spin_unlock_bh(&rbconn->list.list_lock);
+ if (ret)
+ return 0; /* hotdrop */
+ else
+ return rbconn->list.count;
}
}

--- a/net/netfilter/nft_connlimit.c
+++ b/net/netfilter/nft_connlimit.c
@@ -30,7 +30,6 @@ static inline void nft_connlimit_do_eval
enum ip_conntrack_info ctinfo;
const struct nf_conn *ct;
unsigned int count;
- bool addit;

tuple_ptr = &tuple;

@@ -44,19 +43,12 @@ static inline void nft_connlimit_do_eval
return;
}

- nf_conncount_lookup(nft_net(pkt), &priv->list, tuple_ptr, zone,
- &addit);
- count = priv->list.count;
-
- if (!addit)
- goto out;
-
- if (nf_conncount_add(&priv->list, tuple_ptr, zone) == NF_CONNCOUNT_ERR) {
+ if (nf_conncount_add(nft_net(pkt), &priv->list, tuple_ptr, zone)) {
regs->verdict.code = NF_DROP;
return;
}
- count++;
-out:
+
+ count = priv->list.count;

if ((count > priv->limit) ^ priv->invert) {
regs->verdict.code = NFT_BREAK;

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