?? tcp.lst
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C51 COMPILER V8.02 TCP 08/07/2008 16:11:58 PAGE 1
C51 COMPILER V8.02, 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 //
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 V8.02 TCP 08/07/2008 16:11:58 PAGE 2
56
57
58
59 //------------------------------------------------------------------------
60 // This sends a TCP segments that do not include any data.
61 // http_send() in the HTTP module is used to send data.
62 // See "TCP/IP Illustrated, Volume 1" Sect 17.3
63 //------------------------------------------------------------------------
64 void tcp_send(UINT flags, UINT hdr_len, UCHAR nr)
65 {
66 1 ULONG idata sum, dest;
67 1 UINT idata result;
68 1 UCHAR xdata * outbuf;
69 1 TCP_HEADER xdata * tcp;
70 1 IP_HEADER xdata * ip;
71 1
72 1
73 1 // Allocate memory for entire outgoing message including
74 1 // eth & IP headers
75 1 outbuf = (UCHAR xdata *)malloc(34 + hdr_len);
76 1 if (outbuf == NULL)
77 1 {
78 2 if (debug) serial_send("TCP: Oops, out of memory\r");
79 2 return;
80 2 }
81 1
82 1
83 1 tcp = (TCP_HEADER xdata *)(outbuf + 34);
84 1 ip = (IP_HEADER xdata *)(outbuf + 14);
85 1
86 1 // If no connection, then message is probably a reset
87 1 // message which goes back to the sender
88 1 // Otherwise, use information from the connection.
89 1 if (nr == NO_CONNECTION)
90 1 {
91 2 tcp->source_port = HTTP_PORT;
92 2 tcp->dest_port = sender_tcpport;
94 2 tcp->ack_number = 0;
95 2 dest = sender_ipaddr;
96 2 }
97 1 else if (nr < 5)
98 1 {
99 2 // This message is to connected port
100 2 tcp->source_port = HTTP_PORT;
101 2 tcp->dest_port = conxn[nr].port;
102 2 tcp->sequence = conxn[nr].my_sequence;
103 2 tcp->ack_number = conxn[nr].his_sequence;
104 2 dest = conxn[nr].ipaddr;
105 2 }
106 1 else
107 1 {
108 2 if (debug) serial_send("TCP: Oops, sock nr out of range\r");
109 2 free(outbuf);
110 2 return;
111 2 }
112 1
113 1 // Total segment length = header length
114 1
115 1 // Insert header len
116 1 tcp->flags = (hdr_len << 10) | flags;
117 1 tcp->window = 1024;
C51 COMPILER V8.02 TCP 08/07/2008 16:11:58 PAGE 3
118 1 tcp->checksum = 0;
119 1 tcp->urgent_ptr = 0;
120 1
121 1 // Sending SYN with header options
122 1 if (hdr_len == 28)
123 1 {
124 2 memcpy(&tcp->options, opt, 8);
125 2 }
126 1
127 1 // Compute checksum including 12 bytes of pseudoheader
128 1 // Must pre-fill 2 items in ip header to do this
129 1 ip->dest_ipaddr = dest;
130 1 ip->source_ipaddr = my_ipaddr;
131 1
132 1 // Sum source_ipaddr, dest_ipaddr, and entire TCP message
133 1 sum = (ULONG)cksum(outbuf + 26, 8 + hdr_len);
134 1
135 1 // Add in the rest of pseudoheader which is
136 1 // protocol id and TCP segment length
137 1 sum += (ULONG)0x0006;
138 1 sum += (ULONG)hdr_len;
139 1
140 1 // In case there was a carry, add it back around
141 1 result = (UINT)(sum + (sum >> 16));
142 1 tcp->checksum = ~result;
143 1
144 1 if (debug) serial_send("TCP: Sending msg to IP layer\r");
145 1 ip_send(outbuf, dest, TCP_TYPE, hdr_len);
146 1
147 1 // (Re)start TCP retransmit timer
148 1 conxn[nr].timer = TCP_TIMEOUT;
149 1 }
150
151
152
153
154 //------------------------------------------------------------------------
155 // This runs every 0.5 seconds. If the other end has not ACK'd
156 // everyting we have sent, it re-sends it. To save RAM space, we
157 // regenerate a segment rather than keeping a bunch of segments
158 // hanging around eating up RAM. A connection should not be in an
159 // opening or closing state when this timer expires, so we simply
160 // send a reset.
161 //
162 // If a connection is in the ESTABLISHED state when the timer expires
163 // then we have just sent a web page so re-send the page
164 //------------------------------------------------------------------------
165 void tcp_retransmit(void)
166 {
167 1 static UCHAR idata retries = 0;
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 V8.02 TCP 08/07/2008 16:11:58 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) serial_send("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) serial_send("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) serial_send("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) serial_send("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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