tcp/dccp: do not touch listener sk_refcnt under synflood
When a SYNFLOOD targets a non SO_REUSEPORT listener, multiple
cpus contend on sk->sk_refcnt and sk->sk_wmem_alloc changes.
By letting listeners use SOCK_RCU_FREE infrastructure,
we can relax TCP_LISTEN lookup rules and avoid touching sk_refcnt
Note that we still use SLAB_DESTROY_BY_RCU rules for other sockets,
only listeners are impacted by this change.
Peak performance under SYNFLOOD is increased by ~33% :
On my test machine, I could process 3.2 Mpps instead of 2.4 Mpps
Most consuming functions are now skb_set_owner_w() and sock_wfree()
contending on sk->sk_wmem_alloc when cooking SYNACK and freeing them.
Signed-off-by: Eric Dumazet <edumazet@google.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 e6ef6ce1..607da08 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -120,6 +120,7 @@
return score;
}
+/* called with rcu_read_lock() */
struct sock *inet6_lookup_listener(struct net *net,
struct inet_hashinfo *hashinfo,
struct sk_buff *skb, int doff,
@@ -127,38 +128,27 @@
const __be16 sport, const struct in6_addr *daddr,
const unsigned short hnum, const int dif)
{
- struct sock *sk;
- const struct hlist_nulls_node *node;
- struct sock *result;
- int score, hiscore, matches = 0, reuseport = 0;
- bool select_ok = true;
- u32 phash = 0;
unsigned int hash = inet_lhashfn(net, hnum);
struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];
+ int score, hiscore = 0, matches = 0, reuseport = 0;
+ struct sock *sk, *result = NULL;
+ u32 phash = 0;
-begin:
- result = NULL;
- hiscore = 0;
- sk_nulls_for_each(sk, node, &ilb->head) {
+ sk_for_each(sk, &ilb->head) {
score = compute_score(sk, net, hnum, daddr, dif);
if (score > hiscore) {
hiscore = score;
- result = sk;
- reuseport = sk->sk_reuseport;
if (reuseport) {
phash = inet6_ehashfn(net, daddr, hnum,
saddr, sport);
- if (select_ok) {
- struct sock *sk2;
- sk2 = reuseport_select_sock(sk, phash,
- skb, doff);
- if (sk2) {
- result = sk2;
- goto found;
- }
- }
+ result = reuseport_select_sock(sk, phash,
+ skb, doff);
+ if (result)
+ return result;
matches = 1;
}
+ result = sk;
+ reuseport = sk->sk_reuseport;
} else if (score == hiscore && reuseport) {
matches++;
if (reciprocal_scale(phash, matches) == 0)
@@ -166,24 +156,6 @@
phash = next_pseudo_random32(phash);
}
}
- /*
- * 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) {
-found:
- 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);
- select_ok = false;
- goto begin;
- }
- }
return result;
}
EXPORT_SYMBOL_GPL(inet6_lookup_listener);
@@ -195,10 +167,12 @@
const int dif)
{
struct sock *sk;
+ bool refcounted;
sk = __inet6_lookup(net, hashinfo, skb, doff, saddr, sport, daddr,
- ntohs(dport), dif);
-
+ ntohs(dport), dif, &refcounted);
+ if (sk && !refcounted && !atomic_inc_not_zero(&sk->sk_refcnt))
+ sk = NULL;
return sk;
}
EXPORT_SYMBOL_GPL(inet6_lookup);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 711d209..f0422e7 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -858,6 +858,7 @@
return;
#ifdef CONFIG_TCP_MD5SIG
+ rcu_read_lock();
hash_location = tcp_parse_md5sig_option(th);
if (sk && sk_fullsock(sk)) {
key = tcp_v6_md5_do_lookup(sk, &ipv6h->saddr);
@@ -875,16 +876,15 @@
th->source, &ipv6h->daddr,
ntohs(th->source), tcp_v6_iif(skb));
if (!sk1)
- return;
+ goto out;
- rcu_read_lock();
key = tcp_v6_md5_do_lookup(sk1, &ipv6h->saddr);
if (!key)
- goto release_sk1;
+ goto out;
genhash = tcp_v6_md5_hash_skb(newhash, key, NULL, skb);
if (genhash || memcmp(hash_location, newhash, 16) != 0)
- goto release_sk1;
+ goto out;
}
#endif
@@ -898,11 +898,8 @@
tcp_v6_send_response(sk, skb, seq, ack_seq, 0, 0, 0, oif, key, 1, 0, 0);
#ifdef CONFIG_TCP_MD5SIG
-release_sk1:
- if (sk1) {
- rcu_read_unlock();
- sock_put(sk1);
- }
+out:
+ rcu_read_unlock();
#endif
}
@@ -1351,6 +1348,7 @@
{
const struct tcphdr *th;
const struct ipv6hdr *hdr;
+ bool refcounted;
struct sock *sk;
int ret;
struct net *net = dev_net(skb->dev);
@@ -1381,7 +1379,8 @@
lookup:
sk = __inet6_lookup_skb(&tcp_hashinfo, skb, __tcp_hdrlen(th),
- th->source, th->dest, inet6_iif(skb));
+ th->source, th->dest, inet6_iif(skb),
+ &refcounted);
if (!sk)
goto no_tcp_socket;
@@ -1404,6 +1403,7 @@
goto lookup;
}
sock_hold(sk);
+ refcounted = true;
nsk = tcp_check_req(sk, skb, req, false);
if (!nsk) {
reqsk_put(req);
@@ -1460,7 +1460,8 @@
bh_unlock_sock(sk);
put_and_return:
- sock_put(sk);
+ if (refcounted)
+ sock_put(sk);
return ret ? -1 : 0;
no_tcp_socket:
@@ -1483,7 +1484,8 @@
return 0;
discard_and_relse:
- sock_put(sk);
+ if (refcounted)
+ sock_put(sk);
goto discard_it;
do_time_wait:
@@ -1514,6 +1516,7 @@
inet_twsk_deschedule_put(tw);
sk = sk2;
tcp_v6_restore_cb(skb);
+ refcounted = false;
goto process;
}
/* Fall through to ACK */