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| author | Neal Cardwell <ncardwell@google.com> | 2015-02-06 16:04:39 -0500 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-02-08 01:03:12 -0800 |
| commit | a9b2c06dbef48ed31cff1764c5ce824829106f4f (patch) | |
| tree | 7e1dc6d03d3f2ba41a3a867fad3bf59c49665599 /net/ipv4/tcp_minisocks.c | |
| parent | 032ee4236954eb214651cb9bfc1b38ffa8fd7a01 (diff) | |
| download | lwn-a9b2c06dbef48ed31cff1764c5ce824829106f4f.tar.gz lwn-a9b2c06dbef48ed31cff1764c5ce824829106f4f.zip | |
tcp: mitigate ACK loops for connections as tcp_request_sock
In the SYN_RECV state, where the TCP connection is represented by
tcp_request_sock, we now rate-limit SYNACKs in response to a client's
retransmitted SYNs: we do not send a SYNACK in response to client SYN
if it has been less than sysctl_tcp_invalid_ratelimit (default 500ms)
since we last sent a SYNACK in response to a client's retransmitted
SYN.
This allows the vast majority of legitimate client connections to
proceed unimpeded, even for the most aggressive platforms, iOS and
MacOS, which actually retransmit SYNs 1-second intervals for several
times in a row. They use SYN RTO timeouts following the progression:
1,1,1,1,1,2,4,8,16,32.
Reported-by: Avery Fay <avery@mixpanel.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_minisocks.c')
| -rw-r--r-- | net/ipv4/tcp_minisocks.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index bc9216dc9de1..131aa4950d1c 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -605,7 +605,11 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb, * Reset timer after retransmitting SYNACK, similar to * the idea of fast retransmit in recovery. */ - if (!inet_rtx_syn_ack(sk, req)) + if (!tcp_oow_rate_limited(sock_net(sk), skb, + LINUX_MIB_TCPACKSKIPPEDSYNRECV, + &tcp_rsk(req)->last_oow_ack_time) && + + !inet_rtx_syn_ack(sk, req)) req->expires = min(TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX) + jiffies; return NULL; |