I would like to back out the DELAY_ACK macro changes
for now.
The ttcp code behaviour has changed because of the
addition of the DELAY_ACK macro.
The macro is forcing the ttcp code to send an immediate
SYN, ACK for an initial ttcp segment which has the
SYN/FIN/PSH flag set.
Instead the SYN,ACK should be delayed such that
next segment should be SYN/FIN/PSH from the server side.
Change the macro to
DELAY_ACK(tp) \
(tcp_delack_enabled)
instead of
#define DELAY_ACK(tp) \
(tcp_delack_enabled && !callout_pending(tp->tt_delack))
All version before r1.124 seem to work fine
http://www.FreeBSD.org/cgi/cvsweb.cgi/src/sys/netinet/tcp_input.c.diff?r1=1.123
&r2=1.124&f=h
>
> /* TTCP Code in tcp_input.c*/
> if ((to.to_flag & TOF_CC) != 0) {
> if (((tp->t_flags & TF_NOPUSH) != 0) &&
> taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) {
> taop->tao_cc = to.to_cc;
> tp->t_starttime = ticks;
> tp->t_state = TCPS_ESTABLISHED;
> /*
> * If there is a FIN, or if there is data and the
> * connection is local, then delay SYN,ACK(SYN) in
> * the hope of piggy-backing it on a response
> * segment. Otherwise must send ACK now in case
> * the other side is slow starting.
> */
> if (DELAY_ACK(tp) && ((thflags & TH_FIN) ||
> (tlen != 0 &&
> in_localaddr(inp->inp_faddr)))) {
> callout_reset(tp->tt_delack, tcp_delacktime,
> tcp_timer_delack, tp);
> tp->t_flags |= TF_NEEDSYN;
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> At this point NEEDSYN is set and so is the delack timer....
>
> } else
> tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
>
> ....................................................
>
> if (thflags & TH_FIN) {
> if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
> socantrcvmore(so);
> /*
> * If connection is half-synchronized
> * (ie NEEDSYN flag on) then delay ACK,
> * so it may be piggybacked when SYN is sent.
> * Otherwise, since we received a FIN then no
> * more input can be expected, send ACK now.
> */
> if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN))
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> At this point the DELAY_ACK macro returns false because there is a
> callout_pending(). Hence the TF_ACKNOW will be set.
> ^^^^^^^^^^^^^
>
> callout_reset(tp->tt_delack, tcp_delacktime,
> tcp_timer_delack, tp);
> else
> tp->t_flags |= TF_ACKNOW;
>
jayanth
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