Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 18/33] tcp_bbr: fix to zero idle_restart only upon S/ACKed data | Date | Fri, 18 May 2018 10:15:57 +0200 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Neal Cardwell <ncardwell@google.com>
[ Upstream commit e6e6a278b1eaffa19d42186bfacd1ffc15a50b3f ]
Previously the bbr->idle_restart tracking was zeroing out the bbr->idle_restart bit upon ACKs that did not SACK or ACK anything, e.g. receiving incoming data or receiver window updates. In such situations BBR would forget that this was a restart-from-idle situation, and if the min_rtt had expired it would unnecessarily enter PROBE_RTT (even though we were actually restarting from idle but had merely forgotten that fact).
The fix is simple: we need to remember we are restarting from idle until we receive a S/ACK for some data (a S/ACK for the first flight of data we send as we are restarting).
This commit is a stable candidate for kernels back as far as 4.9.
Fixes: 0f8782ea1497 ("tcp_bbr: add BBR congestion control") Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: Priyaranjan Jha <priyarjha@google.com> Signed-off-by: Yousuk Seung <ysseung@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/ipv4/tcp_bbr.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/net/ipv4/tcp_bbr.c +++ b/net/ipv4/tcp_bbr.c @@ -773,7 +773,9 @@ static void bbr_update_min_rtt(struct so } } } - bbr->idle_restart = 0; + /* Restart after idle ends only once we process a new S/ACK for data */ + if (rs->delivered > 0) + bbr->idle_restart = 0; } static void bbr_update_model(struct sock *sk, const struct rate_sample *rs)
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