📄 tcp.lst
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C51 COMPILER V7.20 TCP 03/07/2006 14:49:13 PAGE 1
C51 COMPILER V7.20, COMPILATION OF MODULE TCP
OBJECT MODULE PLACED IN Tcp.OBJ
COMPILER INVOKED BY: C:\Keil\C51\BIN\C51.EXE Tcp.c OPTIMIZE(9,SPEED) BROWSE DEBUG OBJECTEXTEND
line level source
1 //-----------------------------------------------------------------------------
2 // Net TCP.C
3 //
4 // This module handles TCP segments
5 // Refer to RFC 793, 896, 1122, 1323, 2018, 2581
6 //
7 // A "connection" is a unique combination of 4 items: His IP address,
8 // his port number, my IP address, and my port number.
9 //
10 // Note that a SYN and a FIN count as a byte of data, but a RST does
11 // not count. Neither do any of the other flags.
12 // See "TCP/IP Illustrated, Volume 1" Sect 17.3 for info on flags
13 //-----------------------------------------------------------------------------
14 #include <string.h>
15 #include <stdlib.h>
16 #include <ctype.h> // toupper
17 #include "C8051f.h"
18 #include "net.h"
19 #include "cksum.h"
20 #include "serial.h"
21 #include "ip.h"
22 #include "http.h"
23 #include "tcp.h"
24
25
26 // These structures keep track of connection information
27 CONNECTION xdata conxn[5];
28
29 ULONG idata initial_sequence_nr;
30 UINT xdata sender_tcpport;
31 static ULONG xdata sender_ipaddr;
32 UCHAR idata just_closed; // Keeps track of when a conxn closed
33
34 extern ULONG code my_ipaddr;
35 extern UCHAR idata debug;
36 extern char xdata text[];
37
38 // Options: MSS (4 bytes), NOPS (2 bytes), Selective ACK (2 bytes)
39 UCHAR code opt[10] = {
40 0x02, 0x04, 0x05, 0xB4,
41 0x01, 0x01,
42 0x04, 0x02};
43
44
45
46 //------------------------------------------------------------------------
47 // Initialize variables declared in this module
48 // 初始化tcp
49 //------------------------------------------------------------------------
50 void init_tcp(void)
51 {
52 1 memset(conxn, 0, sizeof(conxn));
53 1 just_closed = FALSE;
54 1 initial_sequence_nr = 1;
55 1 }
C51 COMPILER V7.20 TCP 03/07/2006 14:49:13 PAGE 2
56
57 //------------------------------------------------------------------------
58 // This sends a TCP segments that do not include any data.
59 // http_send() in the HTTP module is used to send data.
60 // See "TCP/IP Illustrated, Volume 1" Sect 17.3
61 // 发送一个TCP段，不包括任何数据。http_send()用于发送数据。
62 //------------------------------------------------------------------------
63 void tcp_send(UINT flags, UINT hdr_len, UCHAR nr)
64 {
65 1 ULONG idata sum, dest;
66 1 UINT idata result;
67 1 UCHAR xdata * outbuf;
68 1 TCP_HEADER xdata * tcp;
69 1 IP_HEADER xdata * ip;
70 1
71 1
72 1 // Allocate memory for entire outgoing message including
73 1 // eth & IP headers
74 1 outbuf = (UCHAR xdata *)malloc(34 + hdr_len);
75 1 if (outbuf == NULL)
76 1 {
77 2 if (debug) SendCommString("TCP: Oops, out of memory\r");
78 2 return;
79 2 }
80 1
81 1
82 1 tcp = (TCP_HEADER xdata *)(outbuf + 34);
83 1 ip = (IP_HEADER xdata *)(outbuf + 14);
84 1
85 1 // If no connection, then message is probably a reset
86 1 // message which goes back to the sender
87 1 // Otherwise, use information from the connection.
88 1 if (nr == NO_CONNECTION)
89 1 {
90 2 tcp->source_port = HTTP_PORT;
91 2 tcp->dest_port = sender_tcpport;
92 2 tcp->sequence = 0;
93 2 tcp->ack_number = 0;
94 2 dest = sender_ipaddr;
95 2 }
96 1 else if (nr < 5)
97 1 {
98 2 // This message is to connected port
99 2 tcp->source_port = HTTP_PORT;
100 2 tcp->dest_port = conxn[nr].port;
101 2 tcp->sequence = conxn[nr].my_sequence;
102 2 tcp->ack_number = conxn[nr].his_sequence;
103 2 dest = conxn[nr].ipaddr;
104 2 }
105 1 else
106 1 {
107 2 if (debug) SendCommString("TCP: Oops, sock nr out of range\r");
108 2 free(outbuf);
109 2 return;
110 2 }
111 1
112 1 // Total segment length = header length
113 1
114 1 // Insert header len
115 1 tcp->flags = (hdr_len << 10) | flags;
116 1 tcp->window = 1024;
117 1 tcp->checksum = 0;
C51 COMPILER V7.20 TCP 03/07/2006 14:49:13 PAGE 3
118 1 tcp->urgent_ptr = 0;//
119 1
120 1 // Sending SYN with header options
121 1 if (hdr_len == 28)
122 1 {
123 2 memcpy(&tcp->options, opt, 8);
124 2 }
125 1
126 1 // Compute checksum including 12 bytes of pseudoheader
127 1 // Must pre-fill 2 items in ip header to do this
128 1 ip->dest_ipaddr = dest;
129 1 ip->source_ipaddr = my_ipaddr;
130 1
131 1 // Sum source_ipaddr, dest_ipaddr, and entire TCP message
132 1 sum = (ULONG)cksum(outbuf + 26, 8 + hdr_len);
133 1
134 1 // Add in the rest of pseudoheader which is
135 1 // protocol id and TCP segment length
136 1 sum += (ULONG)0x0006;
137 1 sum += (ULONG)hdr_len;
138 1
139 1 // In case there was a carry, add it back around
140 1 result = (UINT)(sum + (sum >> 16));
141 1 tcp->checksum = ~result;
142 1
143 1 if (debug) SendCommString("TCP: Sending msg to IP layer\r");
144 1 ip_send(outbuf, dest, TCP_TYPE, hdr_len);
145 1
146 1 // (Re)start TCP retransmit timer
147 1 conxn[nr].timer = TCP_TIMEOUT;
148 1 }
149
150
151 //------------------------------------------------------------------------
152 // This runs every 0.5 seconds. If the other end has not ACK'd
153 // everyting we have sent, it re-sends it. To save RAM space, we
154 // regenerate a segment rather than keeping a bunch of segments
155 // hanging around eating up RAM. A connection should not be in an
156 // opening or closing state when this timer expires, so we simply
157 // send a reset.
158 // 每0.5秒运行一次。如果我们这端发送后另外一端没有没有回复的，将重发。
159 // 为了保证RAM的空间，我们另开了一段RAM，防止互相重叠。当超时时，
160 // 一次连接不应该是开或者关状态，因此我们简单的重发一次。
161 // If a connection is in the ESTABLISHED state when the timer expires
162 // then we have just sent a web page so re-send the page
163 // 在连接状态时，当超时，我们发送网页，更新它。
164 //------------------------------------------------------------------------
165 void tcp_retransmit(void)
166 {
167 1 static UCHAR idata retries = 0;//重试
168 1 UCHAR idata nr;
169 1
170 1 // Scan through all active connections
171 1 for (nr = 0; nr < 5; nr++)
172 1 {
173 2 if ((conxn[nr].ipaddr != 0) && (conxn[nr].timer))
174 2 {
175 3 // Decrement the timer and see if it hit 0
176 3 conxn[nr].timer--;
177 3 if (conxn[nr].timer == 0)
178 3 {
179 4 // Socket just timed out. If we are not in ESTABLISHED state
C51 COMPILER V7.20 TCP 03/07/2006 14:49:13 PAGE 4
180 4 // something is amiss so send reset and close connection
181 4 if (conxn[nr].state != STATE_ESTABLISHED)
182 4 {
183 5 // Send reset and close connection
184 5 if (debug) SendCommString("TCP: Timeout, sending reset\r");
185 5 tcp_send(FLG_RST, 20, nr);
186 5 conxn[nr].ipaddr = 0;
187 5 return;
188 5 }
189 4 else
190 4 {
191 5 // Socket is in ESTABLISHED state. First make sure his
192 5 // ack number is not bogus.
193 5 if (conxn[nr].his_ack > conxn[nr].my_sequence)
194 5 {
195 6 // Send reset and close connection
196 6 if (debug) SendCommString("TCP: Timeout, sending reset\r");
197 6 tcp_send(FLG_RST, 20, nr);
198 6 conxn[nr].ipaddr = 0;
199 6 return;
200 6 }
201 5
202 5 // We always increment our sequence number immediately
203 5 // after sending, so the ack number from the other end
204 5 // should be equal to our sequence number. If it is less,
205 5 // it means he lost some of our data.
206 5 if (conxn[nr].his_ack < conxn[nr].my_sequence)
207 5 {
208 6 retries++;
209 6 if (retries <= 2)
210 6 {
211 7 // The only thing we send is a web page, and it looks
212 7 // like other end did not get it, so resend
213 7 // but do not increase my sequence number
214 7 if (debug) SendCommString("TCP: Timeout, resending data\r");
215 7 http_server(conxn[nr].query, 0, nr, 1);
216 7 conxn[nr].inactivity = INACTIVITY_TIME;
217 7 }
218 6 else
219 6 {
220 7 if (debug) SendCommString("TCP: Giving up, sending reset\r");
221 7 // Send reset and close connection
222 7 tcp_send(FLG_RST, 20, nr);
223 7 conxn[nr].ipaddr = 0;
224 7 }
225 6 }
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