tcp_recv.c

Minix比较全的源码

/*
tcp_recv.c

Copyright 1995 Philip Homburg
*/

#include "inet.h"
#include "buf.h"
#include "clock.h"
#include "event.h"
#include "type.h"
#include "sr.h"

#include "io.h"
#include "tcp_int.h"
#include "tcp.h"
#include "assert.h"

THIS_FILE

FORWARD void create_RST ARGS(( tcp_conn_t *tcp_conn,
	ip_hdr_t *ip_hdr, tcp_hdr_t *tcp_hdr, int data_len ));
FORWARD void process_data ARGS(( tcp_conn_t *tcp_conn,
	tcp_hdr_t *tcp_hdr, acc_t *tcp_data, int data_len ));
FORWARD void process_advanced_data ARGS(( tcp_conn_t *tcp_conn,
	tcp_hdr_t *tcp_hdr, acc_t *tcp_data, int data_len ));

PUBLIC void tcp_frag2conn(tcp_conn, ip_hdr, tcp_hdr, tcp_data, data_len)
tcp_conn_t *tcp_conn;
ip_hdr_t *ip_hdr;
tcp_hdr_t *tcp_hdr;
acc_t *tcp_data;
size_t data_len;
{
	tcp_fd_t *connuser;
	int tcp_hdr_flags;
	int ip_hdr_len, tcp_hdr_len;
	u32_t seg_ack, seg_seq, rcv_hi, snd_una, snd_nxt;
	u16_t seg_wnd, mtu;
	size_t mss;
	int acceptable_ACK, segm_acceptable, send_rst, close_connection;

	ip_hdr_len= (ip_hdr->ih_vers_ihl & IH_IHL_MASK) << 2;
	tcp_hdr_len= (tcp_hdr->th_data_off & TH_DO_MASK) >> 2;

	tcp_hdr_flags= tcp_hdr->th_flags & TH_FLAGS_MASK;
	seg_ack= ntohl(tcp_hdr->th_ack_nr);
	seg_seq= ntohl(tcp_hdr->th_seq_nr);
	seg_wnd= ntohs(tcp_hdr->th_window);

#if 0
 { where(); tcp_print_conn(tcp_conn); printf("\n");
	tcp_print_pack(ip_hdr, tcp_hdr); printf("\n"); }
#endif

	switch (tcp_conn->tc_state)
	{
	case TCS_CLOSED:
/*
CLOSED:
	discard all data.
	!RST ?
		ACK ?
			<SEQ=SEG.ACK><CTL=RST>
			exit
		:
			<SEQ=0><ACK=SEG.SEQ+SEG.LEN><CTL=RST,ACK>
			exit
	:
		discard packet
		exit
*/

		if (!(tcp_hdr_flags & THF_RST))
		{
			create_RST(tcp_conn, ip_hdr, tcp_hdr, data_len);
			tcp_conn_write(tcp_conn, 1);
		}
		break;
	case TCS_LISTEN:
/*
LISTEN:
	RST ?
		discard packet
		exit
	ACK ?
		<SEQ=SEG.ACK><CTL=RST>
		exit
	SYN ?
		BUG: no security check
		RCV.NXT= SEG.SEQ+1
		IRS= SEG.SEQ
		ISS should already be selected
		<SEQ=ISS><ACK=RCV.NXT><CTL=SYN,ACK>
		SND.NXT=ISS+1
		SND.UNA=ISS
		state= SYN-RECEIVED
		exit
	:
		shouldnot occur
		discard packet
		exit
*/
		if (tcp_hdr_flags & THF_RST)
			break;
		if (tcp_hdr_flags & THF_ACK)
		{
			create_RST (tcp_conn, ip_hdr, tcp_hdr, data_len);
			tcp_conn_write(tcp_conn, 1);
			break;
		}
		if (tcp_hdr_flags & THF_SYN)
		{
			tcp_extract_ipopt(tcp_conn, ip_hdr);
			tcp_extract_tcpopt(tcp_conn, tcp_hdr, &mss);
			mtu= mss+IP_TCP_MIN_HDR_SIZE;
			if (mtu < IP_MIN_MTU)
			{
				/* No or unrealistic mss, use default MTU */
				mtu= IP_DEF_MTU;
			}
			if (mtu < tcp_conn->tc_max_mtu)
			{
				tcp_conn->tc_max_mtu= mtu;
				tcp_conn->tc_mtu= mtu;
				DBLOCK(1, printf(
					"tcp[%d]: conn[%d]: mtu = %d\n",
					tcp_conn->tc_port-tcp_port_table,
					tcp_conn-tcp_conn_table, 
					mtu););
			}

			tcp_conn->tc_RCV_LO= seg_seq+1;
			tcp_conn->tc_RCV_NXT= seg_seq+1;
			tcp_conn->tc_RCV_HI= tcp_conn->tc_RCV_LO+
				tcp_conn->tc_rcv_wnd;
			tcp_conn->tc_RCV_UP= seg_seq;
			tcp_conn->tc_IRS= seg_seq;
			tcp_conn->tc_SND_UNA= tcp_conn->tc_ISS;
			tcp_conn->tc_SND_TRM= tcp_conn->tc_ISS;
			tcp_conn->tc_SND_NXT= tcp_conn->tc_ISS+1;
			tcp_conn->tc_SND_UP= tcp_conn->tc_ISS-1;
			tcp_conn->tc_SND_PSH= tcp_conn->tc_ISS-1;
			tcp_conn->tc_state= TCS_SYN_RECEIVED;
			tcp_conn->tc_stt= 0;
			assert (tcp_check_conn(tcp_conn));
			tcp_conn->tc_locaddr= ip_hdr->ih_dst;
			tcp_conn->tc_locport= tcp_hdr->th_dstport;
			tcp_conn->tc_remaddr= ip_hdr->ih_src;
			tcp_conn->tc_remport= tcp_hdr->th_srcport;
			tcp_conn_write(tcp_conn, 1);

			DIFBLOCK(0x10, seg_seq == 0,
				printf("warning got 0 IRS from ");
				writeIpAddr(tcp_conn->tc_remaddr);
				printf("\n"));

			/* Start the timer (if necessary) */
			tcp_set_send_timer(tcp_conn);

			break;
		}
		/* do nothing */
		break;
	case TCS_SYN_SENT:
/*
SYN-SENT:
	ACK ?
		SEG.ACK <= ISS || SEG.ACK > SND.NXT ?
			RST ?
				discard packet
				exit
			:
				<SEQ=SEG.ACK><CTL=RST>
				exit
		SND.UNA <= SEG.ACK && SEG.ACK <= SND.NXT ?
			ACK is acceptable
		:
			ACK is !acceptable
	:
		ACK is !acceptable
	RST ?
		ACK acceptable ?
			discard segment
			state= CLOSED
			error "connection refused"
			exit
		:
			discard packet
			exit
	BUG: no security check
	SYN ?
		IRS= SEG.SEQ
		RCV.NXT= IRS+1
		ACK ?
			SND.UNA= SEG.ACK
		SND.UNA > ISS ?
			state= ESTABLISHED
			<SEQ=SND.NXT><ACK= RCV.NXT><CTL=ACK>
			process ev. URG and text
			exit
		:
			state= SYN-RECEIVED
			SND.WND= SEG.WND
			SND.WL1= SEG.SEQ
			SND.WL2= SEG.ACK
			<SEQ=ISS><ACK=RCV.NXT><CTL=SYN,ACK>
			exit
	:
		discard segment
		exit
*/
		if (tcp_hdr_flags & THF_ACK)
		{
			if (tcp_LEmod4G(seg_ack, tcp_conn->tc_ISS) ||
				tcp_Gmod4G(seg_ack, tcp_conn->tc_SND_NXT))
				if (tcp_hdr_flags & THF_RST)
					break;
				else
				{
					/* HACK: force sending a RST,
					 * normally, RSTs are not send
					 * if the segment is an ACK.
					 */
					create_RST (tcp_conn, ip_hdr,
						tcp_hdr, data_len+1);
					tcp_conn_write(tcp_conn, 1);
					break;
				}
			acceptable_ACK= (tcp_LEmod4G(tcp_conn->tc_SND_UNA,
				seg_ack) && tcp_LEmod4G(seg_ack,
				tcp_conn->tc_SND_NXT));
		}
		else
			acceptable_ACK= FALSE;
		if (tcp_hdr_flags & THF_RST)
		{
			if (acceptable_ACK)
			{
				DBLOCK(1, printf(
					"calling tcp_close_connection\n"));

				tcp_close_connection(tcp_conn,
					ECONNREFUSED);
			}
			break;
		}
		if (tcp_hdr_flags & THF_SYN)
		{
			tcp_extract_ipopt(tcp_conn, ip_hdr);
			tcp_extract_tcpopt(tcp_conn, tcp_hdr, &mss);
			mtu= mss+IP_TCP_MIN_HDR_SIZE;
			if (mtu < IP_MIN_MTU)
			{
				/* No or unrealistic mss, use default MTU */
				mtu= IP_DEF_MTU;
			}
			if (mtu < tcp_conn->tc_max_mtu)
			{
				tcp_conn->tc_max_mtu= mtu;
				tcp_conn->tc_mtu= mtu;
				DBLOCK(1, printf(
					"tcp[%d]: conn[%d]: mtu = %d\n",
					tcp_conn->tc_port-tcp_port_table,
					tcp_conn-tcp_conn_table, 
					mtu););
			}
			tcp_conn->tc_RCV_LO= seg_seq+1;
			tcp_conn->tc_RCV_NXT= seg_seq+1;
			tcp_conn->tc_RCV_HI= tcp_conn->tc_RCV_LO +
				tcp_conn->tc_rcv_wnd;
			tcp_conn->tc_RCV_UP= seg_seq;
			tcp_conn->tc_IRS= seg_seq;
			if (tcp_hdr_flags & THF_ACK)
				tcp_conn->tc_SND_UNA= seg_ack;
			if (tcp_Gmod4G(tcp_conn->tc_SND_UNA,
				tcp_conn->tc_ISS))
			{
				tcp_conn->tc_state= TCS_ESTABLISHED;
				tcp_conn->tc_rt_dead= TCP_DEF_RT_DEAD;

				assert (tcp_check_conn(tcp_conn));
				assert(tcp_conn->tc_connInprogress);

				tcp_restart_connect(tcp_conn);

				tcp_conn->tc_flags |= TCF_SEND_ACK;
				tcp_conn_write(tcp_conn, 1);
				if (data_len != 0)
				{
					tcp_frag2conn(tcp_conn, ip_hdr,
						tcp_hdr, tcp_data, data_len);
					/* tcp_data is already freed */
					return;
				}
				break;
			}
			tcp_conn->tc_state= TCS_SYN_RECEIVED;

			assert (tcp_check_conn(tcp_conn));

			tcp_conn->tc_SND_TRM= tcp_conn->tc_ISS;
			tcp_conn_write(tcp_conn, 1);
		}
		break;

	case TCS_SYN_RECEIVED:
/*
SYN-RECEIVED:
	test if segment is acceptable:

	Segment	Receive	Test
	Length	Window
	0	0	SEG.SEQ == RCV.NXT
	0	>0	RCV.NXT <= SEG.SEQ && SEG.SEQ < RCV.NXT+RCV.WND
	>0	0	not acceptable
	>0	>0	(RCV.NXT <= SEG.SEQ && SEG.SEQ < RCV.NXT+RCV.WND)
			|| (RCV.NXT <= SEG.SEQ+SEG.LEN-1 &&
			SEG.SEQ+SEG.LEN-1 < RCV.NXT+RCV.WND)
	for urgent data: use RCV.WND+1 for RCV.WND

	Special: Send RST if SEG.SEQ < IRS or SEG.SEQ > RCV.NXT+64K (and
		 the packet is not a RST packet itself).
*/
		rcv_hi= tcp_conn->tc_RCV_HI;
		if (tcp_hdr_flags & THF_URG)
			rcv_hi++;
		send_rst= tcp_Lmod4G(seg_seq, tcp_conn->tc_IRS) ||
			tcp_Gmod4G(seg_seq, tcp_conn->tc_RCV_NXT+0x10000);
		close_connection= 0;

		if (!data_len)
		{
			if (rcv_hi == tcp_conn->tc_RCV_NXT)
				segm_acceptable= (seg_seq == rcv_hi);
			else
			{
				assert (tcp_Gmod4G(rcv_hi,
					tcp_conn->tc_RCV_NXT));
				segm_acceptable= (tcp_LEmod4G(tcp_conn->
					tc_RCV_NXT, seg_seq) &&
					tcp_Lmod4G(seg_seq, rcv_hi));
			}
		}
		else
		{
			if (tcp_Gmod4G(rcv_hi, tcp_conn->tc_RCV_NXT))
			{
				segm_acceptable= (tcp_LEmod4G(tcp_conn->
					tc_RCV_NXT, seg_seq) &&
					tcp_Lmod4G(seg_seq, rcv_hi)) ||
					(tcp_LEmod4G(tcp_conn->tc_RCV_NXT,
					seg_seq+data_len-1) &&
					tcp_Lmod4G(seg_seq+data_len-1,
					rcv_hi));
			}
			else
			{
				segm_acceptable= FALSE;
			}
		}
/*
	!segment acceptable ?
		RST ?
			discard packet
			exit
		:
			<SEG=SND.NXT><ACK=RCV.NXT><CTL=ACK>
			exit
*/
		if (!segm_acceptable)
		{
			if (tcp_hdr_flags & THF_RST)
				; /* do nothing */
			else if (send_rst)
			{
				create_RST(tcp_conn, ip_hdr, tcp_hdr,
					data_len);
				tcp_conn_write(tcp_conn, 1);
			}
			else
			{
				tcp_conn->tc_flags |= TCF_SEND_ACK;
				tcp_conn_write(tcp_conn, 1);
			}
			break;
		}
/*
	RST ?
		initiated by a LISTEN ?
			state= LISTEN
			exit
		:
			state= CLOSED
			error "connection refused"
			exit
*/

		if (tcp_hdr_flags & THF_RST)
			close_connection= 1;

/*
	SYN in window ?
		initiated by a LISTEN ?
			state= LISTEN
			exit
		:
			state= CLOSED
			error "connection reset"
			exit
*/
		if ((tcp_hdr_flags & THF_SYN) && tcp_GEmod4G(seg_seq,
			tcp_conn->tc_RCV_NXT))
		{
			close_connection= 1;
		}

		if (close_connection)
		{
			if (!tcp_conn->tc_orglisten)
			{
				tcp_close_connection(tcp_conn, ECONNREFUSED);
				break;
			}

			connuser= tcp_conn->tc_fd;
			assert(connuser);
			if (connuser->tf_flags & TFF_LISTENQ)
			{
				tcp_close_connection (tcp_conn,
					ECONNREFUSED);
			}
			else
			{
				tcp_conn->tc_connInprogress= 0;
				tcp_conn->tc_fd= NULL;

				tcp_close_connection (tcp_conn,
					ECONNREFUSED);

				/* Pick a new ISS next time */
				tcp_conn->tc_ISS= 0;

				(void)tcp_su4listen(connuser, tcp_conn,
					0 /* !do_listenq */);
			}
			break;
		}
/*
	!ACK ?
		discard packet
		exit
*/
		if (!(tcp_hdr_flags & THF_ACK))
			break;
/*
	SND.UNA < SEG.ACK <= SND.NXT ?
		state= ESTABLISHED
	:
		<SEG=SEG.ACK><CTL=RST>
		exit
*/
		if (tcp_Lmod4G(tcp_conn->tc_SND_UNA, seg_ack) &&
			tcp_LEmod4G(seg_ack, tcp_conn->tc_SND_NXT))
		{
			tcp_conn->tc_state= TCS_ESTABLISHED;
			tcp_conn->tc_rt_dead= TCP_DEF_RT_DEAD;

			tcp_release_retrans(tcp_conn, seg_ack, seg_wnd);

			assert (tcp_check_conn(tcp_conn));
			assert(tcp_conn->tc_connInprogress);

			tcp_restart_connect(tcp_conn);
			tcp_frag2conn(tcp_conn, ip_hdr, tcp_hdr, tcp_data,
				data_len);
			/* tcp_data is already freed */
			return;
		}
		else
		{
			create_RST (tcp_conn, ip_hdr, tcp_hdr, data_len);
			tcp_conn_write(tcp_conn, 1);
			break;
		}
		break;

	case TCS_ESTABLISHED:
	case TCS_CLOSING:
/*
ESTABLISHED:
FIN-WAIT-1:
FIN-WAIT-2:
CLOSE-WAIT:
CLOSING:
LAST-ACK: