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@google.com>
Signed-off-by: Yousuk Seung <ysseung@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c
index ca61e2a..cd4814f 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. */