tcprwindow.c

来自「TCP-IP红宝书源代码」· C语言 代码 · 共 32 行

/* tcprwindow.c - tcprwindow */

#include <conf.h>
#include <kernel.h>
#include <network.h>

/*------------------------------------------------------------------------
 *  tcprwindow - do receive window processing for a TCB
 *------------------------------------------------------------------------
 */
int
tcprwindow(struct tcb *ptcb)
{
	int	window;

	window = ptcb->tcb_rbsize - ptcb->tcb_rbcount;
	if (ptcb->tcb_state < TCPS_ESTABLISHED)
		return window;
	/*
	 *	Receiver-Side Silly Window Syndrome Avoidance:
	 *  Never shrink an already-advertised window, but wait for at
	 *  least 1/4 receiver buffer and 1 max-sized segment before
	 *  opening a zero window.
	 */
	if (window*4 < (int)ptcb->tcb_rbsize ||
	    window < (int)ptcb->tcb_rmss)
		window = 0;
	window = max(window, ptcb->tcb_cwin - ptcb->tcb_rnext);
	ptcb->tcb_cwin = ptcb->tcb_rnext + window;
	return window;
}