[src/trunk]: src/sys/netinet comments

[yamt <yamt%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/356146b9e610
branches:  trunk
changeset: 764256:356146b9e610
user:      yamt <yamt%NetBSD.org@localhost>
date:      Thu Apr 14 15:55:46 2011 +0000

description:
comments

diffstat:

 sys/netinet/tcp_var.h |  36 +++++++++++++++++++++++++++++-------
 1 files changed, 29 insertions(+), 7 deletions(-)

diffs (64 lines):

diff -r 016c5c6f5c39 -r 356146b9e610 sys/netinet/tcp_var.h
--- a/sys/netinet/tcp_var.h     Thu Apr 14 15:54:31 2011 +0000
+++ b/sys/netinet/tcp_var.h     Thu Apr 14 15:55:46 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tcp_var.h,v 1.162 2009/09/16 15:23:05 pooka Exp $      */
+/*     $NetBSD: tcp_var.h,v 1.163 2011/04/14 15:55:46 yamt Exp $       */
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -191,6 +191,12 @@
        short   t_rxtshift;             /* log(2) of rexmt exp. backoff */
        uint32_t t_rxtcur;              /* current retransmit value */
        short   t_dupacks;              /* consecutive dup acks recd */
+       /*
+        * t_partialacks:
+        *      <0      not in fast recovery.
+        *      ==0     in fast recovery.  has not received partial acks
+        *      >0      in fast recovery.  has received partial acks
+        */
        short   t_partialacks;          /* partials acks during fast rexmit */
        u_short t_peermss;              /* peer's maximum segment size */
        u_short t_ourmss;               /* our's maximum segment size */
@@ -233,8 +239,18 @@
        tcp_seq snd_wl2;                /* window update seg ack number */
        tcp_seq iss;                    /* initial send sequence number */
        u_long  snd_wnd;                /* send window */
-       tcp_seq snd_recover;            /* for use in fast recovery */
-       tcp_seq snd_high;               /* NewReno false fast rexmit seq */
+/*
+ * snd_recover
+ *     it's basically same as the "recover" variable in RFC 2852 (NewReno).
+ *     when entering fast retransmit, it's set to snd_max.
+ *     newreno uses this to detect partial ack.
+ * snd_high
+ *     it's basically same as the "send_high" variable in RFC 2852 (NewReno).
+ *     on each RTO, it's set to snd_max.
+ *     newreno uses this to avoid false fast retransmits.
+ */
+       tcp_seq snd_recover;
+       tcp_seq snd_high;
 /* receive sequence variables */
        u_long  rcv_wnd;                /* receive window */
        tcp_seq rcv_nxt;                /* receive next */
@@ -245,10 +261,16 @@
  */
 /* receive variables */
        tcp_seq rcv_adv;                /* advertised window */
-/* retransmit variables */
-       tcp_seq snd_max;                /* highest sequence number sent;
-                                        * used to recognize retransmits
-                                        */
+
+/*
+ * retransmit variables
+ *
+ * snd_max
+ *     the highest sequence number we've ever sent.
+ *     used to recognize retransmits.
+ */
+       tcp_seq snd_max;
+
 /* congestion control (for slow start, source quench, retransmit after loss) */
        u_long  snd_cwnd;               /* congestion-controlled window */
        u_long  snd_ssthresh;           /* snd_cwnd size threshhold for