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>
diff --git a/include/net/sock.h b/include/net/sock.h
index 0782228..cf12b1e 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -256,7 +256,6 @@
struct sk_buff *head;
struct sk_buff *tail;
int len;
- int limit;
} sk_backlog;
wait_queue_head_t *sk_sleep;
struct dst_entry *sk_dst_cache;
@@ -608,10 +607,20 @@
skb->next = NULL;
}
+/*
+ * Take into account size of receive queue and backlog queue
+ */
+static inline bool sk_rcvqueues_full(const struct sock *sk, const struct sk_buff *skb)
+{
+ unsigned int qsize = sk->sk_backlog.len + atomic_read(&sk->sk_rmem_alloc);
+
+ return qsize + skb->truesize > sk->sk_rcvbuf;
+}
+
/* The per-socket spinlock must be held here. */
static inline __must_check int sk_add_backlog(struct sock *sk, struct sk_buff *skb)
{
- if (sk->sk_backlog.len >= max(sk->sk_backlog.limit, sk->sk_rcvbuf << 1))
+ if (sk_rcvqueues_full(sk, skb))
return -ENOBUFS;
__sk_add_backlog(sk, skb);
diff --git a/net/core/sock.c b/net/core/sock.c
index 58ebd14..5104175 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -327,6 +327,10 @@
skb->dev = NULL;
+ if (sk_rcvqueues_full(sk, skb)) {
+ atomic_inc(&sk->sk_drops);
+ goto discard_and_relse;
+ }
if (nested)
bh_lock_sock_nested(sk);
else
@@ -1885,7 +1889,6 @@
sk->sk_allocation = GFP_KERNEL;
sk->sk_rcvbuf = sysctl_rmem_default;
sk->sk_sndbuf = sysctl_wmem_default;
- sk->sk_backlog.limit = sk->sk_rcvbuf << 1;
sk->sk_state = TCP_CLOSE;
sk_set_socket(sk, sock);
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index fa3d287..63eb56b 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1372,6 +1372,10 @@
goto drop;
}
+
+ if (sk_rcvqueues_full(sk, skb))
+ goto drop;
+
rc = 0;
bh_lock_sock(sk);
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 2850e35..3ead20a 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -584,6 +584,10 @@
sk = stack[i];
if (skb1) {
+ if (sk_rcvqueues_full(sk, skb)) {
+ kfree_skb(skb1);
+ goto drop;
+ }
bh_lock_sock(sk);
if (!sock_owned_by_user(sk))
udpv6_queue_rcv_skb(sk, skb1);
@@ -759,6 +763,10 @@
/* deliver */
+ if (sk_rcvqueues_full(sk, skb)) {
+ sock_put(sk);
+ goto discard;
+ }
bh_lock_sock(sk);
if (!sock_owned_by_user(sk))
udpv6_queue_rcv_skb(sk, skb);
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index f34adcc..13d8229 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3721,9 +3721,6 @@
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();
