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netfilter: nf_conncount: merge lookup and add functions

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'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>
This commit is contained in:
Florian Westphal 2018-12-28 01:24:46 +01:00 committed by Pablo Neira Ayuso
parent e8cfb372b3
commit df4a902509
3 changed files with 72 additions and 106 deletions
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18
include/net/netfilter/nf_conntrack_count.h
View File

@ -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 net *net,
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);

146
net/netfilter/nf_conncount.c
View File

@ -83,38 +83,6 @@ static int key_diff(const u32 *a, const u32 *b, unsigned int klen)
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_conncount_list *list,
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;
}
EXPORT_SYMBOL_GPL(nf_conncount_lookup);
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_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;
}
}

14
net/netfilter/nft_connlimit.c
View File

@ -30,7 +30,6 @@ static inline void nft_connlimit_do_eval(struct nft_connlimit *priv,
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(struct nft_connlimit *priv,
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;