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authorKevin Yang <yyd@google.com>2018-08-22 17:43:16 -0400
committerDavid S. Miller <davem@davemloft.net>2018-08-22 21:45:32 -0700
commit8e995bf14fdb7e33681d5c3312b602fa342b878a (patch)
treece51c37366551d55e5c7a3ae22f9849ec918c57a /net/ipv4/tcp_bbr.c
parenttcp_bbr: in restart from idle, see if we should exit PROBE_RTT (diff)
downloadlinux-dev-8e995bf14fdb7e33681d5c3312b602fa342b878a.tar.xz
linux-dev-8e995bf14fdb7e33681d5c3312b602fa342b878a.zip
tcp_bbr: apply PROBE_RTT cwnd cap even if acked==0
This commit fixes a corner case where TCP BBR would enter PROBE_RTT mode but not reduce its cwnd. If a TCP receiver ACKed less than one full segment, the number of delivered/acked packets was 0, so that bbr_set_cwnd() would short-circuit and exit early, without cutting cwnd to the value we want for PROBE_RTT. The fix is to instead make sure that even when 0 full packets are ACKed, we do apply all the appropriate caps, including the cap that applies in PROBE_RTT mode. Fixes: 0f8782ea1497 ("tcp_bbr: add BBR congestion control") Signed-off-by: Kevin Yang <yyd@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Reviewed-by: Yuchung Cheng <ycheng@google.com> Reviewed-by: Soheil Hassas Yeganeh <soheil@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.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c
index 1d4bdd3b5e4d..02ff2dde9609 100644
--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -420,10 +420,10 @@ static void bbr_set_cwnd(struct sock *sk, const struct rate_sample *rs,
{
struct tcp_sock *tp = tcp_sk(sk);
struct bbr *bbr = inet_csk_ca(sk);
- u32 cwnd = 0, target_cwnd = 0;
+ u32 cwnd = tp->snd_cwnd, target_cwnd = 0;
if (!acked)
- return;
+ goto done; /* no packet fully ACKed; just apply caps */
if (bbr_set_cwnd_to_recover_or_restore(sk, rs, acked, &cwnd))
goto done;