path: root/net/dccp
diff options
authorEric Dumazet <edumazet@google.com>2016-10-26 09:27:57 -0700
committerDavid S. Miller <davem@davemloft.net>2016-10-29 15:09:21 -0400
commit5ea8ea2cb7f1d0db15762c9b0bb9e7330425a071 (patch)
tree46fb718cf8da30f0cbb023e19081921cac3832a0 /net/dccp
parentnet: phy: at803x: Add a definition for PHY ID mask (diff)
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>
Diffstat (limited to 'net/dccp')
2 files changed, 2 insertions, 8 deletions
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);