diff options
| author | Eric Dumazet <edumazet@google.com> | 2016-10-26 09:27:57 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-03-27 14:13:04 +0900 |
| commit | dfe4f69f8ee06f8a95877cf8fb98795e8ac65eca (patch) | |
| tree | a3f9a8ab7ebb4d605a368f2adbf9160a35f1f5b5 /net/dccp | |
| parent | 9e9e3a46e69d5d3ed7e4333d9ed86486fd84ffc4 (diff) | |
tcp/dccp: drop SYN packets if accept queue is full
commit 5ea8ea2cb7f1d0db15762c9b0bb9e7330425a071 upstream.
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>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net/dccp')
| -rw-r--r-- | net/dccp/ipv4.c | 8 | ||||
| -rw-r--r-- | net/dccp/ipv6.c | 2 |
2 files changed, 2 insertions, 8 deletions
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c index 28ad6f187e19..1d6d3aaa8c3d 100644 --- a/net/dccp/ipv4.c +++ b/net/dccp/ipv4.c @@ -596,13 +596,7 @@ 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 6cbcf399d22b..93c706172f40 100644 --- a/net/dccp/ipv6.c +++ b/net/dccp/ipv6.c @@ -328,7 +328,7 @@ 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); |