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Date: Mon, 8 Oct 2018 15:32:20 -0700
From: Yuchung Cheng <ycheng@...gle.com>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org, edumazet@...gle.com, ncardwell@...gle.com,
ysseung@...gle.com, Yuchung Cheng <ycheng@...gle.com>
Subject: [PATCH net-next] tcp: refactor DCTCP ECN ACK handling
DCTCP has two parts - a new ECN signalling mechanism and the response
function to it. The first part can be used by other congestion
control for DCTCP-ECN deployed networks. This patch moves that part
into a separate tcp_dctcp.h to be used by other congestion control
module (like how Yeah uses Vegas algorithmas). For example, BBR is
experimenting such ECN signal currently
https://tinyurl.com/ietf-102-iccrg-bbr2
Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
Signed-off-by: Yousuk Seung <ysseung@...gle.com>
Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
net/ipv4/tcp_dctcp.c | 55 ++++----------------------------------------
net/ipv4/tcp_dctcp.h | 40 ++++++++++++++++++++++++++++++++
2 files changed, 44 insertions(+), 51 deletions(-)
create mode 100644 net/ipv4/tcp_dctcp.h
diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c
index ca61e2a659e7..cd4814f7e962 100644
--- a/net/ipv4/tcp_dctcp.c
+++ b/net/ipv4/tcp_dctcp.c
@@ -44,6 +44,7 @@
#include <linux/mm.h>
#include <net/tcp.h>
#include <linux/inet_diag.h>
+#include "tcp_dctcp.h"
#define DCTCP_MAX_ALPHA 1024U
@@ -118,54 +119,6 @@ static u32 dctcp_ssthresh(struct sock *sk)
return max(tp->snd_cwnd - ((tp->snd_cwnd * ca->dctcp_alpha) >> 11U), 2U);
}
-/* Minimal DCTP CE state machine:
- *
- * S: 0 <- last pkt was non-CE
- * 1 <- last pkt was CE
- */
-
-static void dctcp_ce_state_0_to_1(struct sock *sk)
-{
- struct dctcp *ca = inet_csk_ca(sk);
- struct tcp_sock *tp = tcp_sk(sk);
-
- if (!ca->ce_state) {
- /* State has changed from CE=0 to CE=1, force an immediate
- * ACK to reflect the new CE state. If an ACK was delayed,
- * send that first to reflect the prior CE state.
- */
- if (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_TIMER)
- __tcp_send_ack(sk, ca->prior_rcv_nxt);
- inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
- }
-
- ca->prior_rcv_nxt = tp->rcv_nxt;
- ca->ce_state = 1;
-
- tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
-}
-
-static void dctcp_ce_state_1_to_0(struct sock *sk)
-{
- struct dctcp *ca = inet_csk_ca(sk);
- struct tcp_sock *tp = tcp_sk(sk);
-
- if (ca->ce_state) {
- /* State has changed from CE=1 to CE=0, force an immediate
- * ACK to reflect the new CE state. If an ACK was delayed,
- * send that first to reflect the prior CE state.
- */
- if (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_TIMER)
- __tcp_send_ack(sk, ca->prior_rcv_nxt);
- inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
- }
-
- ca->prior_rcv_nxt = tp->rcv_nxt;
- ca->ce_state = 0;
-
- tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
-}
-
static void dctcp_update_alpha(struct sock *sk, u32 flags)
{
const struct tcp_sock *tp = tcp_sk(sk);
@@ -230,12 +183,12 @@ static void dctcp_state(struct sock *sk, u8 new_state)
static void dctcp_cwnd_event(struct sock *sk, enum tcp_ca_event ev)
{
+ struct dctcp *ca = inet_csk_ca(sk);
+
switch (ev) {
case CA_EVENT_ECN_IS_CE:
- dctcp_ce_state_0_to_1(sk);
- break;
case CA_EVENT_ECN_NO_CE:
- dctcp_ce_state_1_to_0(sk);
+ dctcp_ece_ack_update(sk, ev, &ca->prior_rcv_nxt, &ca->ce_state);
break;
default:
/* Don't care for the rest. */
diff --git a/net/ipv4/tcp_dctcp.h b/net/ipv4/tcp_dctcp.h
new file mode 100644
index 000000000000..d69a77cbd0c7
--- /dev/null
+++ b/net/ipv4/tcp_dctcp.h
@@ -0,0 +1,40 @@
+#ifndef _TCP_DCTCP_H
+#define _TCP_DCTCP_H
+
+static inline void dctcp_ece_ack_cwr(struct sock *sk, u32 ce_state)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+
+ if (ce_state == 1)
+ tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
+ else
+ tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
+}
+
+/* Minimal DCTP CE state machine:
+ *
+ * S: 0 <- last pkt was non-CE
+ * 1 <- last pkt was CE
+ */
+static inline void dctcp_ece_ack_update(struct sock *sk, enum tcp_ca_event evt,
+ u32 *prior_rcv_nxt, u32 *ce_state)
+{
+ u32 new_ce_state = (evt == CA_EVENT_ECN_IS_CE) ? 1 : 0;
+
+ if (*ce_state != new_ce_state) {
+ /* CE state has changed, force an immediate ACK to
+ * reflect the new CE state. If an ACK was delayed,
+ * send that first to reflect the prior CE state.
+ */
+ if (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_TIMER) {
+ dctcp_ece_ack_cwr(sk, *ce_state);
+ __tcp_send_ack(sk, *prior_rcv_nxt);
+ }
+ inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
+ }
+ *prior_rcv_nxt = tcp_sk(sk)->rcv_nxt;
+ *ce_state = new_ce_state;
+ dctcp_ece_ack_cwr(sk, new_ce_state);
+}
+
+#endif
--
2.19.0.605.g01d371f741-goog
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