net: Convert TCP/DCCP listening hash tables to use RCU
This is the last step to be able to perform full RCU lookups
in __inet_lookup() : After established/timewait tables, we
add RCU lookups to listening hash table.
The only trick here is that a socket of a given type (TCP ipv4,
TCP ipv6, ...) can now flight between two different tables
(established and listening) during a RCU grace period, so we
must use different 'nulls' end-of-chain values for two tables.
We define a large value :
#define LISTENING_NULLS_BASE (1U << 29)
So that slots in listening table are guaranteed to have different
end-of-chain values than slots in established table. A reader can
still detect it finished its lookup in the right chain.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
index e0fd681..8fe267f 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -33,7 +33,7 @@
ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
spin_lock(&ilb->lock);
- __sk_add_node(sk, &ilb->head);
+ __sk_nulls_add_node_rcu(sk, &ilb->head);
spin_unlock(&ilb->lock);
} else {
unsigned int hash;
@@ -118,47 +118,71 @@
}
EXPORT_SYMBOL(__inet6_lookup_established);
+static int inline compute_score(struct sock *sk, struct net *net,
+ const unsigned short hnum,
+ const struct in6_addr *daddr,
+ const int dif)
+{
+ int score = -1;
+
+ if (net_eq(sock_net(sk), net) && inet_sk(sk)->num == hnum &&
+ sk->sk_family == PF_INET6) {
+ const struct ipv6_pinfo *np = inet6_sk(sk);
+
+ score = 1;
+ if (!ipv6_addr_any(&np->rcv_saddr)) {
+ if (!ipv6_addr_equal(&np->rcv_saddr, daddr))
+ return -1;
+ score++;
+ }
+ if (sk->sk_bound_dev_if) {
+ if (sk->sk_bound_dev_if != dif)
+ return -1;
+ score++;
+ }
+ }
+ return score;
+}
+
struct sock *inet6_lookup_listener(struct net *net,
struct inet_hashinfo *hashinfo, const struct in6_addr *daddr,
const unsigned short hnum, const int dif)
{
struct sock *sk;
- const struct hlist_node *node;
- struct sock *result = NULL;
- int score, hiscore = 0;
- struct inet_listen_hashbucket *ilb;
+ const struct hlist_nulls_node *node;
+ struct sock *result;
+ int score, hiscore;
+ unsigned int hash = inet_lhashfn(net, hnum);
+ struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];
- ilb = &hashinfo->listening_hash[inet_lhashfn(net, hnum)];
- spin_lock(&ilb->lock);
- sk_for_each(sk, node, &ilb->head) {
- if (net_eq(sock_net(sk), net) && inet_sk(sk)->num == hnum &&
- sk->sk_family == PF_INET6) {
- const struct ipv6_pinfo *np = inet6_sk(sk);
-
- score = 1;
- if (!ipv6_addr_any(&np->rcv_saddr)) {
- if (!ipv6_addr_equal(&np->rcv_saddr, daddr))
- continue;
- score++;
- }
- if (sk->sk_bound_dev_if) {
- if (sk->sk_bound_dev_if != dif)
- continue;
- score++;
- }
- if (score == 3) {
- result = sk;
- break;
- }
- if (score > hiscore) {
- hiscore = score;
- result = sk;
- }
+ rcu_read_lock();
+begin:
+ result = NULL;
+ hiscore = -1;
+ sk_nulls_for_each(sk, node, &ilb->head) {
+ score = compute_score(sk, net, hnum, daddr, dif);
+ if (score > hiscore) {
+ hiscore = score;
+ result = sk;
}
}
- if (result)
- sock_hold(result);
- spin_unlock(&ilb->lock);
+ /*
+ * if the nulls value we got at the end of this lookup is
+ * not the expected one, we must restart lookup.
+ * We probably met an item that was moved to another chain.
+ */
+ if (get_nulls_value(node) != hash + LISTENING_NULLS_BASE)
+ goto begin;
+ if (result) {
+ if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt)))
+ result = NULL;
+ else if (unlikely(compute_score(result, net, hnum, daddr,
+ dif) < hiscore)) {
+ sock_put(result);
+ goto begin;
+ }
+ }
+ rcu_read_unlock();
return result;
}