net: sk_add_backlog() take rmem_alloc into account

Current socket backlog limit is not enough to really stop DDOS attacks,
because user thread spend many time to process a full backlog each
round, and user might crazy spin on socket lock.

We should add backlog size and receive_queue size (aka rmem_alloc) to
pace writers, and let user run without being slow down too much.

Introduce a sk_rcvqueues_full() helper, to avoid taking socket lock in
stress situations.

Under huge stress from a multiqueue/RPS enabled NIC, a single flow udp
receiver can now process ~200.000 pps (instead of ~100 pps before the
patch) on a 8 core machine.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 0 insertions, 3 deletions

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index f34adcca8a8c..13d8229f3a9c 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3721,9 +3721,6 @@ SCTP_STATIC int sctp_init_sock(struct sock *sk)
         SCTP_DBG_OBJCNT_INC(sock);
         percpu_counter_inc(&sctp_sockets_allocated);
 
-        /* Set socket backlog limit. */
-        sk->sk_backlog.limit = sysctl_sctp_rmem[1];
-
         local_bh_disable();
         sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
         local_bh_enable();