diff options
| author | Eric Dumazet <edumazet@google.com> | 2016-10-26 09:27:57 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-10-29 15:09:21 -0400 |
| commit | 5ea8ea2cb7f1d0db15762c9b0bb9e7330425a071 (patch) | |
| tree | 46fb718cf8da30f0cbb023e19081921cac3832a0 | |
| parent | 58effd7168e9b74252650a008b5229c7cf224c7b (diff) | |
| download | linux-5ea8ea2cb7f1d0db15762c9b0bb9e7330425a071.tar.bz2 | |
tcp/dccp: drop SYN packets if accept queue is full
Per listen(fd, backlog) rules, there is really no point accepting a SYN,
sending a SYNACK, and dropping the following ACK packet if accept queue
is full, because application is not draining accept queue fast enough.
This behavior is fooling TCP clients that believe they established a
flow, while there is nothing at server side. They might then send about
10 MSS (if using IW10) that will be dropped anyway while server is under
stress.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | include/net/inet_connection_sock.h | 5 | ||||
| -rw-r--r-- | net/dccp/ipv4.c | 8 | ||||
| -rw-r--r-- | net/dccp/ipv6.c | 2 | ||||
| -rw-r--r-- | net/ipv4/tcp_input.c | 8 |
4 files changed, 3 insertions, 20 deletions
diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h index 197a30d221e9..146054ceea8e 100644 --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -289,11 +289,6 @@ static inline int inet_csk_reqsk_queue_len(const struct sock *sk) return reqsk_queue_len(&inet_csk(sk)->icsk_accept_queue); } -static inline int inet_csk_reqsk_queue_young(const struct sock *sk) -{ - return reqsk_queue_len_young(&inet_csk(sk)->icsk_accept_queue); -} - static inline int inet_csk_reqsk_queue_is_full(const struct sock *sk) { return inet_csk_reqsk_queue_len(sk) >= sk->sk_max_ack_backlog; diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c index 345a3aeb8c7e..a957acac2337 100644 --- a/net/dccp/ipv4.c +++ b/net/dccp/ipv4.c @@ -588,13 +588,7 @@ int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb) if (inet_csk_reqsk_queue_is_full(sk)) goto drop; - /* - * Accept backlog is full. If we have already queued enough - * of warm entries in syn queue, drop request. It is better than - * clogging syn queue with openreqs with exponentially increasing - * timeout. - */ - if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) + if (sk_acceptq_is_full(sk)) goto drop; req = inet_reqsk_alloc(&dccp_request_sock_ops, sk, true); diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c index 3828f94b234c..32f9f1a189f8 100644 --- a/net/dccp/ipv6.c +++ b/net/dccp/ipv6.c @@ -325,7 +325,7 @@ static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb) if (inet_csk_reqsk_queue_is_full(sk)) goto drop; - if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) + if (sk_acceptq_is_full(sk)) goto drop; req = inet_reqsk_alloc(&dccp6_request_sock_ops, sk, true); diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index a27b9c0e27c0..f2c59c8e57ff 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -6298,13 +6298,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, goto drop; } - - /* Accept backlog is full. If we have already queued enough - * of warm entries in syn queue, drop request. It is better than - * clogging syn queue with openreqs with exponentially increasing - * timeout. - */ - if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) { + if (sk_acceptq_is_full(sk)) { NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS); goto drop; } |