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| author | Neal Cardwell <ncardwell@google.com> | 2018-05-01 21:45:41 -0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-05-02 11:12:32 -0400 |
| commit | e6e6a278b1eaffa19d42186bfacd1ffc15a50b3f (patch) | |
| tree | 3e42446d622d43a07493f1b110bd9986345eff95 /net/ipv4/tcp_bbr.c | |
| parent | 5e5add172ea81152d518b161ec5706503ad3d799 (diff) | |
| download | lwn-e6e6a278b1eaffa19d42186bfacd1ffc15a50b3f.tar.gz lwn-e6e6a278b1eaffa19d42186bfacd1ffc15a50b3f.zip | |
tcp_bbr: fix to zero idle_restart only upon S/ACKed data
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>
Diffstat (limited to 'net/ipv4/tcp_bbr.c')
| -rw-r--r-- | net/ipv4/tcp_bbr.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c index 158d105e76da..58e2f479ffb4 100644 --- a/net/ipv4/tcp_bbr.c +++ b/net/ipv4/tcp_bbr.c @@ -806,7 +806,9 @@ static void bbr_update_min_rtt(struct sock *sk, const struct rate_sample *rs) } } } - 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) |