Commit c377411f authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Dumazet <>
Signed-off-by: default avatarDavid S. Miller <>
parent 6e7676c1
......@@ -256,7 +256,6 @@ struct sock {
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 @@ static inline void __sk_add_backlog(struct sock *sk, struct sk_buff *skb)
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);
......@@ -327,6 +327,10 @@ int sk_receive_skb(struct sock *sk, struct sk_buff *skb, const int nested)
skb->dev = NULL;
if (sk_rcvqueues_full(sk, skb)) {
goto discard_and_relse;
if (nested)
......@@ -1885,7 +1889,6 @@ void sock_init_data(struct socket *sock, struct sock *sk)
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);
......@@ -1372,6 +1372,10 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
goto drop;
if (sk_rcvqueues_full(sk, skb))
goto drop;
rc = 0;
......@@ -584,6 +584,10 @@ static void flush_stack(struct sock **stack, unsigned int count,
sk = stack[i];
if (skb1) {
if (sk_rcvqueues_full(sk, skb)) {
goto drop;
if (!sock_owned_by_user(sk))
udpv6_queue_rcv_skb(sk, skb1);
......@@ -759,6 +763,10 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
/* deliver */
if (sk_rcvqueues_full(sk, skb)) {
goto discard;
if (!sock_owned_by_user(sk))
udpv6_queue_rcv_skb(sk, skb);
......@@ -3721,9 +3721,6 @@ SCTP_STATIC int sctp_init_sock(struct sock *sk)
/* Set socket backlog limit. */
sk->sk_backlog.limit = sysctl_sctp_rmem[1];
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
Supports Markdown
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment