tcp_recv.c

minix3的源代码

TIME-WAIT:
	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
*/
		rcv_hi= tcp_conn->tc_RCV_HI;
		if (tcp_hdr_flags & THF_URG)
			rcv_hi++;
		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))
			{
				DBLOCK(0x20,
					printf("segment is not acceptable\n");
					printf("\t");
					tcp_print_pack(ip_hdr, tcp_hdr);
					printf("\n\t");
					tcp_print_conn(tcp_conn);
					printf("\n"));
				tcp_conn->tc_flags |= TCF_SEND_ACK;
				tcp_conn_write(tcp_conn, 1);

				/* Sometimes, a retransmission sets the PSH
				 * flag (Solaris 2.4)
				 */
				if (tcp_conn->tc_rcvd_data != NULL &&
					(tcp_hdr_flags & THF_PSH))
				{
					tcp_conn->tc_flags |= TCF_RCV_PUSH;
					if (tcp_conn->tc_fd &&
						(tcp_conn->tc_fd->tf_flags &
						TFF_READ_IP))
					{
						tcp_fd_read(tcp_conn, 1);
					}
					if (tcp_conn->tc_fd &&
						(tcp_conn->tc_fd->tf_flags &
						TFF_SEL_READ))
					{
						tcp_rsel_read(tcp_conn);
					}
				}
			}
			break;
		}
/*
	RST ?
		state == CLOSING || state == LAST-ACK ||
			state == TIME-WAIT ?
			state= CLOSED
			exit
		:
			state= CLOSED
			error "connection reset"
			exit
*/
		if (tcp_hdr_flags & THF_RST)
		{
			if ((tcp_conn->tc_flags &
				(TCF_FIN_SENT|TCF_FIN_RECV)) ==
				(TCF_FIN_SENT|TCF_FIN_RECV) &&
				tcp_conn->tc_send_data == NULL)
			{
				/* Clean shutdown, but the other side
				 * doesn't want to ACK our FIN.
				 */
				tcp_close_connection (tcp_conn, 0);
			}
			else
				tcp_close_connection(tcp_conn, ECONNRESET);
			break;
		}
/*
	SYN in window ?
		state= CLOSED
		error "connection reset"
		exit
*/
		if ((tcp_hdr_flags & THF_SYN) && tcp_GEmod4G(seg_seq,
			tcp_conn->tc_RCV_NXT))
		{
			tcp_close_connection(tcp_conn, ECONNRESET);
			break;
		}
/*
	!ACK ?
		discard packet
		exit
*/
		if (!(tcp_hdr_flags & THF_ACK))
			break;

/*
	SND.UNA < SEG.ACK <= SND.NXT ?
		SND.UNA= SEG.ACK
		reply "send ok"
		SND.WL1 < SEG.SEQ || (SND.WL1 == SEG.SEQ &&
			SND.WL2 <= SEG.ACK ?
			SND.WND= SEG.WND
			SND.Wl1= SEG.SEQ
			SND.WL2= SEG.ACK
	SEG.ACK <= SND.UNA ?
		ignore ACK
	SEG.ACK > SND.NXT ?
		<SEQ=SND.NXT><ACK=RCV.NXT><CTL=ACK>
		discard packet
		exit
*/

		/* Always reset the send timer after a valid ack is
		 * received. The assumption is that either the ack really
		 * acknowledges some data (normal case), contains a zero
		 * window, or the remote host has another reason not
		 * to accept any data. In all cases, the remote host is
		 * alive, so the connection should stay alive too.
		 * Do not reset stt if the state is CLOSING, i.e. if
		 * the user closed the connection and we still have
		 * some data to deliver. We don't want a zero window
		 * to keep us from closing the connection.
		 */
		if (tcp_conn->tc_state != TCS_CLOSING)
			tcp_conn->tc_stt= 0;

		snd_una= tcp_conn->tc_SND_UNA;
		snd_nxt= tcp_conn->tc_SND_NXT;
		if (seg_ack == snd_una)
		{
			
			if (tcp_Gmod4G(snd_nxt, snd_una))
			{
				/* Duplicate ACK */
				if (++tcp_conn->tc_snd_dack ==
					TCP_DACK_RETRANS)
				{
					tcp_fast_retrans(tcp_conn);
				}
			}

			/* This ACK doesn't acknowledge any new data, this
			 * is a likely situation if we are only receiving
			 * data. We only update the window if we are
			 * actually sending or if we currently have a
			 * zero window.
			 */
			if (tcp_conn->tc_snd_cwnd == snd_una &&
				seg_wnd != 0)
			{
				DBLOCK(2, printf("zero window opened\n"));
				/* The other side opened up its receive
				 * window. */
				mss= tcp_conn->tc_mtu-IP_TCP_MIN_HDR_SIZE;
				if (seg_wnd > 2*mss)
					seg_wnd= 2*mss;
				tcp_conn->tc_snd_cwnd= snd_una+seg_wnd;
				tcp_conn_write(tcp_conn, 1);
			}
			if (seg_wnd == 0)
			{
				tcp_conn->tc_snd_cwnd= tcp_conn->tc_SND_TRM=
					snd_una;
			}
		}
		else if (tcp_Lmod4G(snd_una, seg_ack) &&
			tcp_LEmod4G(seg_ack, snd_nxt))
		{
			tcp_release_retrans(tcp_conn, seg_ack, seg_wnd);
			if (tcp_conn->tc_state == TCS_CLOSED)
				break;
		}
		else if (tcp_Gmod4G(seg_ack,
			snd_nxt))
		{
			tcp_conn->tc_flags |= TCF_SEND_ACK;
			tcp_conn_write(tcp_conn, 1);
			DBLOCK(1, printf(
			"got an ack of something I haven't send\n");
				printf( "seg_ack= %lu, SND_NXT= %lu\n",
				seg_ack, snd_nxt));
			break;
		}

/*
	process data...
*/
		tcp_extract_ipopt(tcp_conn, ip_hdr);
		tcp_extract_tcpopt(tcp_conn, tcp_hdr, &mss);

		if (data_len)
		{
			if (tcp_LEmod4G(seg_seq, tcp_conn->tc_RCV_NXT))
			{
				process_data (tcp_conn, tcp_hdr,
					tcp_data, data_len);
			}
			else
			{
				process_advanced_data (tcp_conn,
					tcp_hdr, tcp_data, data_len);
			}
			tcp_conn->tc_flags |= TCF_SEND_ACK;
			tcp_conn_write(tcp_conn, 1);

			/* Don't process a FIN if we got new data */
			break;
		}
/*
	FIN ?
		reply pending receives
		advace RCV.NXT over the FIN
		<SEQ=SND.NXT><ACK=RCV.NXT><CTL=ACK>

		state == ESTABLISHED ?
			state= CLOSE-WAIT
		state == FIN-WAIT-1 ?
			state= CLOSING
		state == FIN-WAIT-2 ?
			state= TIME-WAIT
		state == TIME-WAIT ?
			restart the TIME-WAIT timer
	exit
*/
		if ((tcp_hdr_flags & THF_FIN) && tcp_LEmod4G(seg_seq,
			tcp_conn->tc_RCV_NXT))
		{
			if (!(tcp_conn->tc_flags & TCF_FIN_RECV) &&
				tcp_Lmod4G(tcp_conn->tc_RCV_NXT,
				tcp_conn->tc_RCV_HI))
			{
				tcp_conn->tc_RCV_NXT++;
				tcp_conn->tc_flags |= TCF_FIN_RECV;
			}
			tcp_conn->tc_flags |= TCF_SEND_ACK;
			tcp_conn_write(tcp_conn, 1);
			if (tcp_conn->tc_fd &&
				(tcp_conn->tc_fd->tf_flags & TFF_READ_IP))
			{
				tcp_fd_read(tcp_conn, 1);
			}
			if (tcp_conn->tc_fd &&
				(tcp_conn->tc_fd->tf_flags & TFF_SEL_READ))
			{
				tcp_rsel_read(tcp_conn);
			}
		}
		break;
	default:
		printf("tcp_frag2conn: unknown state ");
		tcp_print_state(tcp_conn);
		break;
	}
	if (tcp_data != NULL)
		bf_afree(tcp_data);
}


PRIVATE void
process_data(tcp_conn, tcp_hdr, tcp_data, data_len)
tcp_conn_t *tcp_conn;
tcp_hdr_t *tcp_hdr;
acc_t *tcp_data;
int data_len;
{
	u32_t lo_seq, hi_seq, urg_seq, seq_nr, adv_seq, nxt;
	u32_t urgptr;
	int tcp_hdr_flags;
	unsigned int offset;
	acc_t *tmp_data, *rcvd_data, *adv_data;
	int len_diff;

	assert(tcp_conn->tc_busy);

	/* Note, tcp_data will be freed by the caller. */
	assert (!(tcp_hdr->th_flags & THF_SYN));

	seq_nr= ntohl(tcp_hdr->th_seq_nr);
	urgptr= ntohs(tcp_hdr->th_urgptr);

	tcp_data->acc_linkC++;

	lo_seq= seq_nr;
	tcp_hdr_flags= tcp_hdr->th_flags & TH_FLAGS_MASK;

	if (tcp_Lmod4G(lo_seq, tcp_conn->tc_RCV_NXT))
	{
		DBLOCK(0x10,
			printf("segment is a retransmission\n"));
		offset= tcp_conn->tc_RCV_NXT-lo_seq;
		tcp_data= bf_delhead(tcp_data, offset);
		lo_seq += offset;
		data_len -= offset;
		if (tcp_hdr_flags & THF_URG)
		{
			printf("process_data: updating urgent pointer\n");
			if (urgptr >= offset)
				urgptr -= offset;
			else
				tcp_hdr_flags &= ~THF_URG;
		}
	}
	assert (lo_seq == tcp_conn->tc_RCV_NXT);

	if (tcp_hdr_flags & THF_URG)
	{
		if (!(tcp_conn->tc_flags & TCF_BSD_URG))
		{
			/* Update urgent pointer to point past the urgent
			 * data
			 */
			urgptr++;
		}
		if (urgptr == 0)
			tcp_hdr_flags &= ~THF_URG;
	}

	if (tcp_hdr_flags & THF_URG)
	{
		if (urgptr > data_len)
			urgptr= data_len;
		urg_seq= lo_seq+urgptr;

		if (tcp_GEmod4G(urg_seq, tcp_conn->tc_RCV_HI))
			urg_seq= tcp_conn->tc_RCV_HI;
		if (tcp_conn->tc_flags & TCF_BSD_URG)
		{
			if (tcp_Gmod4G(tcp_conn->tc_RCV_NXT,
				tcp_conn->tc_RCV_LO))
			{
				DBLOCK(1, printf(
					"ignoring urgent data\n"));

				bf_afree(tcp_data);
				/* Should set advertised window to
				 * zero */

				/* Flush */
				tcp_conn->tc_flags |= TCF_RCV_PUSH;
				if (tcp_conn->tc_fd &&
					(tcp_conn->tc_fd->tf_flags &
					TFF_READ_IP))
				{
					tcp_fd_read(tcp_conn, 1);
				}
				if (tcp_conn->tc_fd &&
					(tcp_conn->tc_fd->tf_flags &
					TFF_SEL_READ))
				{
					tcp_rsel_read(tcp_conn);
				}
				return;
			}
		}
		if (tcp_Gmod4G(urg_seq, tcp_conn->tc_RCV_UP))
			tcp_conn->tc_RCV_UP= urg_seq;
#if 0
		if (urgptr < data_len)
		{
			data_len= urgptr;
			tmp_data= bf_cut(tcp_data, 0, data_len);
			bf_afree(tcp_data);
			tcp_data= tmp_data;
			tcp_hdr_flags &= ~THF_FIN;
		}
#endif
		tcp_conn->tc_flags |= TCF_RCV_PUSH;
	}
	else
	{
		/* Normal data. */
	}

	if (tcp_hdr_flags & THF_PSH)
	{
		tcp_conn->tc_flags |= TCF_RCV_PUSH;
	}

	hi_seq= lo_seq+data_len;
	if (tcp_Gmod4G(hi_seq, tcp_conn->tc_RCV_HI))
	{
		data_len= tcp_conn->tc_RCV_HI-lo_seq;
		tmp_data= bf_cut(tcp_data, 0, data_len);
		bf_afree(tcp_data);
		tcp_data= tmp_data;
		hi_seq= lo_seq+data_len;
		tcp_hdr_flags &= ~THF_FIN;
	}
	assert (tcp_LEmod4G (hi_seq, tcp_conn->tc_RCV_HI));

	rcvd_data= tcp_conn->tc_rcvd_data;
	tcp_conn->tc_rcvd_data= 0;
	tmp_data= bf_append(rcvd_data, tcp_data);
	tcp_conn->tc_rcvd_data= tmp_data;
	tcp_conn->tc_RCV_NXT= hi_seq;

	if ((tcp_hdr_flags & THF_FIN) && 
		tcp_Lmod4G(tcp_conn->tc_RCV_NXT, tcp_conn->tc_RCV_HI) &&
		!(tcp_conn->tc_flags & TCF_FIN_RECV))
	{
		tcp_conn->tc_RCV_NXT++;
		tcp_conn->tc_flags |= TCF_FIN_RECV;
	}

	if (tcp_conn->tc_fd && (tcp_conn->tc_fd->tf_flags & TFF_READ_IP))
		tcp_fd_read(tcp_conn, 1);
	if (tcp_conn->tc_fd && (tcp_conn->tc_fd->tf_flags & TFF_SEL_READ))
		tcp_rsel_read(tcp_conn);

	DIFBLOCK(2, (tcp_conn->tc_RCV_NXT == tcp_conn->tc_RCV_HI),
		printf("conn[[%d] full receive buffer\n", 
		tcp_conn-tcp_conn_table));

	if (tcp_conn->tc_adv_data == NULL)
		return;
	if (tcp_hdr_flags & THF_FIN)
	{
		printf("conn[%d]: advanced data after FIN\n",
			tcp_conn-tcp_conn_table);
		tcp_data= tcp_conn->tc_adv_data;
		tcp_conn->tc_adv_data= NULL;
		bf_afree(tcp_data);
		return;
	}

	lo_seq= tcp_conn->tc_adv_seq;
	if (tcp_Gmod4G(lo_seq, tcp_conn->tc_RCV_NXT))
		return;		/* Not yet */

	tcp_data= tcp_conn->tc_adv_data;
	tcp_conn->tc_adv_data= NULL;

	data_len= bf_bufsize(tcp_data);
	if (tcp_Lmod4G(lo_seq, tcp_conn->tc_RCV_NXT))
	{
		offset= tcp_conn->tc_RCV_NXT-lo_seq;
		if (offset >= data_len)
		{
			bf_afree(tcp_data);
			return;
		}
		tcp_data= bf_delhead(tcp_data, offset);
		lo_seq += offset;
		data_len -= offset;
	}
	assert (lo_seq == tcp_conn->tc_RCV_NXT);

	hi_seq= lo_seq+data_len;
	assert (tcp_LEmod4G (hi_seq, tcp_conn->tc_RCV_HI));

	rcvd_data= tcp_conn->tc_rcvd_data;
	tcp_conn->tc_rcvd_data= 0;
	tmp_data= bf_append(rcvd_data, tcp_data);