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QRZ! Ham Radio 8
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unixcpio.gz
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unixnet.cpio
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tcptimer.c
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C/C++ Source or Header
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1994-07-11
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1KB
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56 lines
/* TCP timeout routines */
#include <stdio.h>
#include "global.h"
#include "mbuf.h"
#include "timer.h"
#include "netuser.h"
#include "internet.h"
#include "tcp.h"
/* Timer timeout */
void
tcp_timeout(arg)
char *arg;
{
register struct tcb *tcb;
tcb = (struct tcb *)arg;
if(tcb == NULLTCB)
return;
/* Make sure the timer has stopped (we might have been kicked) */
stop_timer(&tcb->timer);
switch(tcb->state){
case TIME_WAIT: /* 2MSL timer has expired */
close_self(tcb,NORMAL);
break;
default: /* Retransmission timer has expired */
tcb->flags |= RETRAN; /* Indicate > 1 transmission */
tcb->backoff++;
tcb->snd.ptr = tcb->snd.una;
/* Reduce slowstart threshold to half current window */
tcb->ssthresh = tcb->cwind / 2;
tcb->ssthresh = max(tcb->ssthresh,tcb->mss);
/* Shrink congestion window to 1 packet */
tcb->cwind = tcb->mss;
tcp_output(tcb);
}
}
/* Backoff function - the subject of much research */
backoff(n)
int n;
{
/* Use binary exponential up to retry #4, and quadratic after that
* This yields the sequence
* 1, 2, 4, 8, 16, 25, 36, 49, 64, 81, 100 ...
*/
if(n <= 4)
return 1 << n; /* Binary exponential back off */
else
return n * n; /* Quadratic back off */
}