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Groups > linux.kernel > #1664009

[PATCH 4.9 005/119] tcp: disallow cwnd undo when switching congestion control

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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 44abafc4cc094214a99f860f778c48ecb23422fc ]

When the sender switches its congestion control during loss
recovery, if the recovery is spurious then it may incorrectly
revert cwnd and ssthresh to the older values set by a previous
congestion control. Consider a congestion control (like BBR)
that does not use ssthresh and keeps it infinite: the connection
may incorrectly revert cwnd to an infinite value when switching
from BBR to another congestion control.

This patch fixes it by disallowing such cwnd undo operation
upon switching congestion control.  Note that undo_marker
is not reset s.t. the packets that were incorrectly marked
lost would be corrected. We only avoid undoing the cwnd in
tcp_undo_cwnd_reduction().

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-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_cong.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -179,6 +179,7 @@ void tcp_init_congestion_control(struct
 {
 	const struct inet_connection_sock *icsk = inet_csk(sk);
 
+	tcp_sk(sk)->prior_ssthresh = 0;
 	if (icsk->icsk_ca_ops->init)
 		icsk->icsk_ca_ops->init(sk);
 	if (tcp_ca_needs_ecn(sk))

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[PATCH 4.9 000/119] 4.9.32-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:00 +0200
  [PATCH 4.9 052/119] dmaengine: mv_xor_v2: set DMA mask to 40 bits Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:00 +0200
  [PATCH 4.9 048/119] dmaengine: mv_xor_v2: do not use descriptors not acked by async_tx Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:00 +0200
  [PATCH 4.9 055/119] ext4: fix SEEK_HOLE Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:00 +0200
  [PATCH 4.9 029/119] crypto: drbg - wait for crypto op not signal safe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:00 +0200
  [PATCH 4.9 054/119] xen/privcmd: Support correctly 64KB page granularity when mapping memory Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:00 +0200
  [PATCH 4.9 023/119] serial: ifx6x60: fix use-after-free on module unload Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:00 +0200
  [PATCH 4.9 030/119] crypto: gcm - wait for crypto op not signal safe Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:00 +0200
  [PATCH 4.9 034/119] efi: Dont issue error message when booted under Xen Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:00 +0200
  [PATCH 4.9 005/119] tcp: disallow cwnd undo when switching congestion control Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:00 +0200
  [PATCH 4.9 017/119] sparc64: combine activate_mm and switch_mm Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:10 +0200
  [PATCH 4.9 013/119] sparc64: Add __multi3 for gcc 7.x and later. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:10 +0200
  [PATCH 4.9 016/119] sparc64: reset mm cpumask after wrap Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:10 +0200
  [PATCH 4.9 011/119] net: stmmac: fix completely hung TX when using TSO Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:10 +0200
  [PATCH 4.9 001/119] bnx2x: Fix Multi-Cos Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:10 +0200
  [PATCH 4.9 010/119] net: ethoc: enable NAPI before poll may be scheduled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:10 +0200
  [PATCH 4.9 018/119] sparc64: redefine first version Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:10 +0200
  [PATCH 4.9 020/119] sparc64: new context wrap Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-12 19:10 +0200
  Re: [PATCH 4.9 000/119] 4.9.32-stable review Guenter Roeck <linux@roeck-us.net> - 2017-06-13 00:00 +0200
    Re: [PATCH 4.9 000/119] 4.9.32-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-13 09:30 +0200
  Re: [PATCH 4.9 000/119] 4.9.32-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-06-13 02:50 +0200

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