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Fix incorrectly implemented receive ACK timeout algorithm:

Browse Source 
instead of bumping the recvAck counter by one, pretend that
all outstanding xmit packets are acknowleged, and restart
transmitting anew, with an empty (but halved) transmit window.

Put a lower bound on the adaptive timeout value.
This commit is contained in:
Archie Cobbs 2000-06-28 19:43:34 +00:00
parent 726bd7bebf
commit e962a82308
1 changed files with 20 additions and 14 deletions
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34
sys/netgraph/ng_pptpgre.c
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@ -115,14 +115,16 @@ struct greheader {
#define PPTP_MAX_PAYLOAD (0xffff - sizeof(struct greheader) - 8)
/* All times are scaled by this (PPTP_TIME_SCALE time units = 1 sec.) */
#define PPTP_TIME_SCALE 1000
#define PPTP_TIME_SCALE 1000 /* milliseconds */
typedef u_int32_t pptptime_t;
/* Acknowledgment timeout parameters and functions */
#define PPTP_XMIT_WIN 8 /* max xmit window */
#define PPTP_MIN_RTT (PPTP_TIME_SCALE / 10) /* 1/10 second */
#define PPTP_XMIT_WIN 16 /* max xmit window */
#define PPTP_MIN_RTT (PPTP_TIME_SCALE / 10) /* 100 milliseconds */
#define PPTP_MIN_TIMEOUT (PPTP_TIME_SCALE / 100) /* 10 milliseconds */
#define PPTP_MAX_TIMEOUT (10 * PPTP_TIME_SCALE) /* 10 seconds */
/* See RFC 2637 section 4.4 */
#define PPTP_ACK_ALPHA(x) ((x) >> 3) /* alpha = 0.125 */
#define PPTP_ACK_BETA(x) ((x) >> 2) /* beta = 0.25 */
#define PPTP_ACK_CHI(x) ((x) << 2) /* chi = 4 */
@ -636,11 +638,17 @@ bad:
if (diff < 0)
diff = -diff;
a->dev += PPTP_ACK_BETA(diff - a->dev);
a->ato = a->rtt + (u_int) (PPTP_ACK_CHI(a->dev));
a->ato = a->rtt + PPTP_ACK_CHI(a->dev);
if (a->ato > PPTP_MAX_TIMEOUT)
a->ato = PPTP_MAX_TIMEOUT;
if (a->ato < PPTP_MIN_TIMEOUT)
a->ato = PPTP_MIN_TIMEOUT;
/* Shift packet transmit times in our transmit window */
ovbcopy(a->timeSent + index + 1, a->timeSent,
sizeof(*a->timeSent) * (PPTP_XMIT_WIN - (index + 1)));
/* If we sent an entire window, increase window size by one */
if (PPTP_SEQ_DIFF(ack, a->winAck) >= 0
&& a->xmitWin < PPTP_XMIT_WIN) {
a->xmitWin++;
@ -772,15 +780,13 @@ ng_pptpgre_recv_ack_timeout(void *arg)
a->ato = a->rtt + PPTP_ACK_CHI(a->dev);
if (a->ato > PPTP_MAX_TIMEOUT)
a->ato = PPTP_MAX_TIMEOUT;
priv->recvAck++; /* assume packet was lost */
a->winAck = priv->recvAck + a->xmitWin; /* reset win expand time */
ovbcopy(a->timeSent + 1, a->timeSent, /* shift xmit window times */
sizeof(*a->timeSent) * (PPTP_XMIT_WIN - 1));
a->xmitWin = (a->xmitWin + 1) / 2; /* shrink transmit window */
if (a->ato < PPTP_MIN_TIMEOUT)
a->ato = PPTP_MIN_TIMEOUT;
/* Restart timer if there are any more outstanding frames */
if (priv->recvAck != priv->xmitSeq)
ng_pptpgre_start_recv_ack_timer(node);
/* Reset ack and sliding window */
priv->recvAck = priv->xmitSeq; /* pretend we got the ack */
a->xmitWin = (a->xmitWin + 1) / 2; /* shrink transmit window */
a->winAck = priv->recvAck + a->xmitWin; /* reset win expand time */
splx(s);
}
@ -859,8 +865,8 @@ ng_pptpgre_reset(node_p node)
a->rtt = PPTP_MIN_RTT;
a->dev = 0;
a->xmitWin = (priv->conf.recvWin + 1) / 2;
if (a->xmitWin < 2)
a->xmitWin = 2;
if (a->xmitWin < 2) /* often the first packet is lost */
a->xmitWin = 2; /* because the peer isn't ready */
if (a->xmitWin > PPTP_XMIT_WIN)
a->xmitWin = PPTP_XMIT_WIN;
a->winAck = a->xmitWin;