From 673fb149c6f3079d4d92ff3f938d44af592c49a6 Mon Sep 17 00:00:00 2001
From: thorpej <thorpej@NetBSD.org>
Date: Wed, 31 Dec 1997 03:31:23 +0000
Subject: [PATCH] Implement a queue for delayed ACK processing.  This queue is
 used in tcp_fasttimo() in lieu of scanning all open TCP connections.

---
 sys/netinet/tcp_input.c  |  4 ++--
 sys/netinet/tcp_output.c |  5 +++--
 sys/netinet/tcp_subr.c   |  3 ++-
 sys/netinet/tcp_timer.c  | 25 +++++++++++++------------
 sys/netinet/tcp_var.h    | 27 ++++++++++++++++++++++++++-
 5 files changed, 46 insertions(+), 18 deletions(-)

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 51662ca59934..531e91267204 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: tcp_input.c,v 1.37 1997/12/11 06:33:29 thorpej Exp $	*/
+/*	$NetBSD: tcp_input.c,v 1.38 1997/12/31 03:31:23 thorpej Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994
@@ -121,7 +121,7 @@ do { \
 	    (tp)->t_flags & TF_DELACK) \
 		tp->t_flags |= TF_ACKNOW; \
 	else \
-		tp->t_flags |= TF_DELACK; \
+		TCP_SET_DELACK(tp); \
 } while (0)
 
 /*
diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
index 421e8768594b..78cfcaa6463a 100644
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: tcp_output.c,v 1.25 1997/12/17 05:59:32 thorpej Exp $	*/
+/*	$NetBSD: tcp_output.c,v 1.26 1997/12/31 03:31:25 thorpej Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1988, 1990, 1993
@@ -642,7 +642,8 @@ out:
 	if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
 		tp->rcv_adv = tp->rcv_nxt + win;
 	tp->last_ack_sent = tp->rcv_nxt;
-	tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
+	tp->t_flags &= ~TF_ACKNOW;
+	TCP_CLEAR_DELACK(tp);
 	if (sendalot)
 		goto again;
 	return (0);
diff --git a/sys/netinet/tcp_subr.c b/sys/netinet/tcp_subr.c
index 723f33a6202f..4f4e83aedc4f 100644
--- a/sys/netinet/tcp_subr.c
+++ b/sys/netinet/tcp_subr.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: tcp_subr.c,v 1.36 1997/12/11 22:47:25 thorpej Exp $	*/
+/*	$NetBSD: tcp_subr.c,v 1.37 1997/12/31 03:31:26 thorpej Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1988, 1990, 1993
@@ -88,6 +88,7 @@ tcp_init()
 {
 
 	in_pcbinit(&tcbtable, tcbhashsize, tcbhashsize);
+	LIST_INIT(&tcp_delacks);
 	if (max_protohdr < sizeof(struct tcpiphdr))
 		max_protohdr = sizeof(struct tcpiphdr);
 	if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN)
diff --git a/sys/netinet/tcp_timer.c b/sys/netinet/tcp_timer.c
index 41de101a8605..17f1e4dad667 100644
--- a/sys/netinet/tcp_timer.c
+++ b/sys/netinet/tcp_timer.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: tcp_timer.c,v 1.26 1997/12/17 06:04:17 thorpej Exp $	*/
+/*	$NetBSD: tcp_timer.c,v 1.27 1997/12/31 03:31:27 thorpej Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1988, 1990, 1993
@@ -71,26 +71,27 @@ extern	int tcp_keepcnt;
 extern	int tcp_maxpersistidle;
 #endif /* TUBA_INCLUDE */
 
+struct tcp_delack_head tcp_delacks;
+
 /*
  * Fast timeout routine for processing delayed acks
  */
 void
 tcp_fasttimo()
 {
-	register struct inpcb *inp;
-	register struct tcpcb *tp;
+	register struct tcpcb *tp, *ntp;
 	int s;
 
 	s = splsoftnet();
-	inp = tcbtable.inpt_queue.cqh_first;
-	if (inp)						/* XXX */
-	for (; inp != (struct inpcb *)&tcbtable.inpt_queue;
-	    inp = inp->inp_queue.cqe_next) {
-		if ((tp = intotcpcb(inp)) != NULL &&
-		    (tp->t_flags & TF_DELACK)) {
-			tp->t_flags |= TF_ACKNOW;
-			(void) tcp_output(tp);
-		}
+	for (tp = tcp_delacks.lh_first; tp != NULL; tp = ntp) {
+		/*
+		 * If tcp_output() can't transmit the ACK for whatever
+		 * reason, it will remain on the queue for the next
+		 * time the heartbeat ticks.
+		 */
+		ntp = tp->t_delack.le_next;
+		tp->t_flags |= TF_ACKNOW;
+		(void) tcp_output(tp);
 	}
 	splx(s);
 }
diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
index 912e6009c90b..b04885b7e124 100644
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: tcp_var.h,v 1.31 1997/12/17 06:06:41 thorpej Exp $	*/
+/*	$NetBSD: tcp_var.h,v 1.32 1997/12/31 03:31:29 thorpej Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1993, 1994
@@ -67,6 +67,7 @@ struct tcpcb {
 
 	struct	tcpiphdr *t_template;	/* skeletal packet for transmit */
 	struct	inpcb *t_inpcb;		/* back pointer to internet pcb */
+	LIST_ENTRY(tcpcb) t_delack;	/* delayed ACK queue */
 /*
  * The following fields are used as in the protocol specification.
  * See RFC783, Dec. 1981, page 21.
@@ -131,6 +132,30 @@ struct tcpcb {
 	caddr_t	t_tuba_pcb;		/* next level down pcb for TCP over z */
 };
 
+/*
+ * Queue for delayed ACK processing.
+ */
+LIST_HEAD(tcp_delack_head, tcpcb);
+#ifdef _KERNEL
+extern struct tcp_delack_head tcp_delacks;
+
+#define	TCP_SET_DELACK(tp) \
+do { \
+	if (((tp)->t_flags & TF_DELACK) == 0) { \
+		(tp)->t_flags |= TF_DELACK; \
+		LIST_INSERT_HEAD(&tcp_delacks, (tp), t_delack); \
+	} \
+} while (0)
+
+#define	TCP_CLEAR_DELACK(tp) \
+do { \
+	if ((tp)->t_flags & TF_DELACK) { \
+		(tp)->t_flags &= ~TF_DELACK; \
+		LIST_REMOVE((tp), t_delack); \
+	} \
+} while (0)
+#endif /* _KERNEL */
+
 /*
  * Handy way of passing around TCP option info.
  */