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/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 */
