aboutsummaryrefslogtreecommitdiffstats
path: root/net
diff options
context:
space:
mode:
authorYuchung Cheng <ycheng@google.com>2017-08-03 20:38:51 -0700
committerDavid S. Miller <davem@davemloft.net>2017-08-06 21:25:10 -0700
commit4faf783998b8cb88294e9df89032f473f8771b78 (patch)
tree0ad450f18cbf6c23f23e9f181a4d4ee5c6a99b7a /net
parentnet: systemport: Support 64bit statistics (diff)
downloadlinux-dev-4faf783998b8cb88294e9df89032f473f8771b78.tar.xz
linux-dev-4faf783998b8cb88294e9df89032f473f8771b78.zip
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>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp_cong.c2
-rw-r--r--net/ipv4/tcp_htcp.c3
-rw-r--r--net/ipv4/tcp_input.c1
3 files changed, 3 insertions, 3 deletions
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);