| Message ID | 20180502014541.194259-1-ncardwell@google.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] tcp_bbr: fix to zero idle_restart only upon S/ACKed data | expand |
From: Neal Cardwell <ncardwell@google.com> Date: Tue, 1 May 2018 21:45:41 -0400 > 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> Applied and queued up for -stable.
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c index 158d105e76da1..58e2f479ffb4d 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)
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> --- net/ipv4/tcp_bbr.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)