diff options
| author | Yuchung Cheng <ycheng@google.com> | 2017-08-03 20:38:51 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-08-06 21:25:10 -0700 |
| commit | 4faf783998b8cb88294e9df89032f473f8771b78 (patch) | |
| tree | 0ad450f18cbf6c23f23e9f181a4d4ee5c6a99b7a | |
| parent | 10377ba7673d19e28d92846955d51f49acd25c35 (diff) | |
tcp: fix cwnd undo in Reno and HTCP congestion controls
Using ssthresh to revert cwnd is less reliable when ssthresh is
bounded to 2 packets. This patch uses an existing variable in TCP
"prior_cwnd" that snapshots the cwnd right before entering fast
recovery and RTO recovery in Reno. This fixes the issue discussed
in netdev thread: "A buggy behavior for Linux TCP Reno and HTCP"
https://www.spinics.net/lists/netdev/msg444955.html
Suggested-by: Neal Cardwell <ncardwell@google.com>
Reported-by: Wei Sun <unlcsewsun@gmail.com>
Signed-off-by: Yuchung Cheng <ncardwell@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | include/linux/tcp.h | 2 | ||||
| -rw-r--r-- | net/ipv4/tcp_cong.c | 2 | ||||
| -rw-r--r-- | net/ipv4/tcp_htcp.c | 3 | ||||
| -rw-r--r-- | net/ipv4/tcp_input.c | 1 |
4 files changed, 4 insertions, 4 deletions
diff --git a/include/linux/tcp.h b/include/linux/tcp.h index d7389ea36e10..267164a1d559 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -258,7 +258,7 @@ struct tcp_sock { u32 snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */ u32 snd_cwnd_used; u32 snd_cwnd_stamp; - u32 prior_cwnd; /* Congestion window at start of Recovery. */ + u32 prior_cwnd; /* cwnd right before starting loss recovery */ u32 prr_delivered; /* Number of newly delivered packets to * receiver in Recovery. */ u32 prr_out; /* Total number of pkts sent during Recovery. */ diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index fde983f6376b..c2b174469645 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -456,7 +456,7 @@ u32 tcp_reno_undo_cwnd(struct sock *sk) { const struct tcp_sock *tp = tcp_sk(sk); - return max(tp->snd_cwnd, tp->snd_ssthresh << 1); + return max(tp->snd_cwnd, tp->prior_cwnd); } EXPORT_SYMBOL_GPL(tcp_reno_undo_cwnd); diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c index 3eb78cde6ff0..082d479462fa 100644 --- a/net/ipv4/tcp_htcp.c +++ b/net/ipv4/tcp_htcp.c @@ -66,7 +66,6 @@ static inline void htcp_reset(struct htcp *ca) static u32 htcp_cwnd_undo(struct sock *sk) { - const struct tcp_sock *tp = tcp_sk(sk); struct htcp *ca = inet_csk_ca(sk); if (ca->undo_last_cong) { @@ -76,7 +75,7 @@ static u32 htcp_cwnd_undo(struct sock *sk) ca->undo_last_cong = 0; } - return max(tp->snd_cwnd, (tp->snd_ssthresh << 7) / ca->beta); + return tcp_reno_undo_cwnd(sk); } static inline void measure_rtt(struct sock *sk, u32 srtt) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 99cdf4ccabb8..842ed75ccb25 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1950,6 +1950,7 @@ void tcp_enter_loss(struct sock *sk) !after(tp->high_seq, tp->snd_una) || (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { tp->prior_ssthresh = tcp_current_ssthresh(sk); + tp->prior_cwnd = tp->snd_cwnd; tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); tcp_ca_event(sk, CA_EVENT_LOSS); tcp_init_undo(tp); |