net-tcp_bbr: set tp->snd_ssthresh to BDP upon STARTUP exit

Set tp->snd_ssthresh to BDP upon STARTUP exit. This allows us
to check if a BBR flow exited STARTUP and the BDP at the
time of STARTUP exit with SCM_TIMESTAMPING_OPT_STATS. Since BBR does not
use snd_ssthresh this fix has no impact on BBR's behavior.

Signed-off-by: Yousuk Seung <ysseung@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Priyaranjan Jha <priyarjha@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c
index c92014cb1e16..158d105e76da 100644
--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -731,6 +731,8 @@ static void bbr_check_drain(struct sock *sk, const struct rate_sample *rs)
                 bbr->mode = BBR_DRAIN;  /* drain queue we created */
                 bbr->pacing_gain = bbr_drain_gain;      /* pace slow to drain */
                 bbr->cwnd_gain = bbr_high_gain; /* maintain cwnd */
+                tcp_sk(sk)->snd_ssthresh =
+                                bbr_target_cwnd(sk, bbr_max_bw(sk), BBR_UNIT);
         }       /* fall through to check if in-flight is already small: */
         if (bbr->mode == BBR_DRAIN &&
             tcp_packets_in_flight(tcp_sk(sk)) <=
@@ -834,6 +836,7 @@ static void bbr_init(struct sock *sk)
         struct bbr *bbr = inet_csk_ca(sk);
 
         bbr->prior_cwnd = 0;
+        tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
         bbr->rtt_cnt = 0;
         bbr->next_rtt_delivered = 0;
         bbr->prev_ca_state = TCP_CA_Open;
@@ -886,7 +889,7 @@ static u32 bbr_undo_cwnd(struct sock *sk)
 static u32 bbr_ssthresh(struct sock *sk)
 {
         bbr_save_cwnd(sk);
-        return TCP_INFINITE_SSTHRESH;    /* BBR does not use ssthresh */
+        return tcp_sk(sk)->snd_ssthresh;
 }
 
 static size_t bbr_get_info(struct sock *sk, u32 ext, int *attr,