tcpwinit.c

来自「TCP-IP红宝书源代码」· C语言 代码 · 共 43 行

/* tcpwinit.c - tcpwinit */

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

/*------------------------------------------------------------------------
 *  tcpwinit - initialize window data for a new connection
 *------------------------------------------------------------------------
 */
int
tcpwinit(struct tcb *ptcb, struct tcb *newptcb, struct ep *pep)
{
	struct	ip	*pip = (struct ip *)pep->ep_data;
	struct	tcp	*ptcp = (struct tcp *)pip->ip_data;
	struct	route	*prt;
	unsigned	mss;
	Bool		local;

	newptcb->tcb_swindow = ptcp->tcp_window;
	newptcb->tcb_lwseq = ptcp->tcp_seq;
	newptcb->tcb_lwack = newptcb->tcb_iss;	/* set in tcpsync()	*/

	prt = (struct route *)rtget(pip->ip_src, RTF_REMOTE);
	local = prt && prt->rt_metric == 0;
	newptcb->tcb_pni = &nif[prt->rt_ifnum];
	rtfree(prt);
	if (local)
		mss = newptcb->tcb_pni->ni_mtu-IPMHLEN-TCPMHLEN;
	else
		mss = 536;	/* RFC 1122 */
	if (ptcb->tcb_smss) {
		newptcb->tcb_smss = min(ptcb->tcb_smss, mss);
		ptcb->tcb_smss = 0;		/* reset server smss	*/
	} else
		newptcb->tcb_smss = mss;
	newptcb->tcb_rmss = mss;		/* receive mss		*/
	newptcb->tcb_cwnd = newptcb->tcb_smss;	/* 1 segment		*/
	newptcb->tcb_ssthresh = 65535;		/* IP max window	*/
	newptcb->tcb_rnext = ptcp->tcp_seq;
	newptcb->tcb_cwin = newptcb->tcb_rnext + newptcb->tcb_rbsize;
}