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Groups > linux.kernel > #1710050

[PATCH 4.9 03/16] tcp: avoid setting cwnd to invalid ssthresh after cwnd reduction states

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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yuchung Cheng <ycheng@google.com>


[ Upstream commit ed254971edea92c3ac5c67c6a05247a92aa6075e ]

If the sender switches the congestion control during ECN-triggered
cwnd-reduction state (CA_CWR), upon exiting recovery cwnd is set to
the ssthresh value calculated by the previous congestion control. If
the previous congestion control is BBR that always keep ssthresh
to TCP_INIFINITE_SSTHRESH, cwnd ends up being infinite. The safe
step is to avoid assigning invalid ssthresh value when recovery ends.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/tcp_input.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2560,8 +2560,8 @@ static inline void tcp_end_cwnd_reductio
 		return;
 
 	/* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
-	if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR ||
-	    (tp->undo_marker && tp->snd_ssthresh < TCP_INFINITE_SSTHRESH)) {
+	if (tp->snd_ssthresh < TCP_INFINITE_SSTHRESH &&
+	    (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR || tp->undo_marker)) {
 		tp->snd_cwnd = tp->snd_ssthresh;
 		tp->snd_cwnd_stamp = tcp_time_stamp;
 	}

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[PATCH 4.9 00/16] 4.9.43-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:10 +0200
  [PATCH 4.9 07/16] net: sched: set xt_tgchk_param par.nft_compat as 0 in ipt_init_target Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:10 +0200
  [PATCH 4.9 13/16] revert "ipv4: Should use consistent conditional judgement for ip fragment in __ip_append_data and ip_finish_output" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:10 +0200
  [PATCH 4.9 08/16] tcp: fastopen: tcp_connect() must refresh the route Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 16/16] KVM: arm/arm64: Handle hva aging while destroying the vm Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 11/16] packet: fix tp_reserve race in packet_set_ring Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 15/16] sparc64: Prevent perf from running during super critical sections Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 04/16] net: fix keepalive code vs TCP_FASTOPEN_CONNECT Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 12/16] revert "net: account for current skb length when deciding about UFO" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 03/16] tcp: avoid setting cwnd to invalid ssthresh after cwnd reduction states Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 06/16] net/mlx4_en: dont set CHECKSUM_COMPLETE on SCTP packets Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 14/16] udp: consistently apply ufo or fragmentation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 05/16] bpf, s390: fix jit branch offset related to ldimm64 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 10/16] igmp: Fix regression caused by igmp sysctl namespace code. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 02/16] ppp: fix xmit recursion detection on ppp channels Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  [PATCH 4.9 01/16] ppp: Fix false xmit recursion detect with two ppp devices Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 00:20 +0200
  Re: [PATCH 4.9 00/16] 4.9.43-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-08-12 04:00 +0200
  Re: [PATCH 4.9 00/16] 4.9.43-stable review Guenter Roeck <linux@roeck-us.net> - 2017-08-12 14:40 +0200
    Re: [PATCH 4.9 00/16] 4.9.43-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-08-12 18:10 +0200
      Re: [PATCH 4.9 00/16] 4.9.43-stable review Guenter Roeck <linux@roeck-us.net> - 2017-08-12 18:30 +0200

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