tcpackit.c,v

来自「TCP-IP红宝书源代码」· C,V 代码 · 共 93 行

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date	97.09.21.19.29.52;	author dls;	state Dist;
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1.1
date	94.01.14.03.51.20;	author dls;	state v2e1;
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@pre-3e code
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@/* tcpackit.c - tcpackit */

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

/*------------------------------------------------------------------------
 *  tcpackit -  generate an ACK for a received TCP packet
 *------------------------------------------------------------------------
 */
int tcpackit(ptcb, pepin)
struct	tcb	*ptcb;
struct	ep	*pepin;
{
	struct ep	*pepout;
	struct ip	*pipin = (struct ip *)pepin->ep_data, *pipout;
	struct tcp	*ptcpin = (struct tcp *)pipin->ip_data, *ptcpout;

	if (ptcpin->tcp_code & TCPF_RST)
		return OK;
	if (pipin->ip_len <= IP_HLEN(pipin) + TCP_HLEN(ptcpin) &&
			!(ptcpin->tcp_code & (TCPF_SYN|TCPF_FIN)))
		return OK;	/* duplicate ACK */
	pepout = (struct ep *)getbuf(Net.netpool);
	if ((int)pepout == SYSERR)
		return SYSERR;
	pepout->ep_order = ~0;
	pipout = (struct ip *)pepout->ep_data;
	pipout->ip_src = pipin->ip_dst;
	pipout->ip_dst = pipin->ip_src;
	ptcpout = (struct tcp *)pipout->ip_data;
	ptcpout->tcp_sport = ptcpin->tcp_dport;
	ptcpout->tcp_dport = ptcpin->tcp_sport;
	ptcpout->tcp_seq = ptcb->tcb_snext;
	ptcpout->tcp_ack = ptcb->tcb_rnext;
	ptcpout->tcp_code = TCPF_ACK;
	ptcpout->tcp_offset = TCPHOFFSET;
	ptcpout->tcp_window = tcprwindow(ptcb);
	ptcpout->tcp_urgptr = 0;
	ptcpout->tcp_cksum = 0;
	tcph2net(ptcpout);
	pepout->ep_order &= ~EPO_TCP;
	ptcpout->tcp_cksum = tcpcksum(pepout, TCPMHLEN);
	TcpOutSegs++;
	return ipsend(pipin->ip_src, pepout, TCPMHLEN, IPT_TCP,
		IPP_NORMAL, IP_TTL);
}
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@Initial revision
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	blkcopy(pipout->ip_src, pipin->ip_dst, IP_ALEN);
	blkcopy(pipout->ip_dst, pipin->ip_src, IP_ALEN);
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	ptcpout->tcp_cksum = tcpcksum(pipout);
@