Nicolas Nackel / Mbed 2 deprecated PPP-Blinky

Small Internet Protocol Stack using a standard serial port.

Dependencies:   mbed

PPP-Blinky - TCP/IP Networking Over a Serial Port

Note: The source code is at the bottom of this page.

/media/uploads/nixnax/blinky-connected.gif
A Windows desktop showing PPP-Blinky in the network connections list.

Describe PPP-Blinky in Three Sentences

PPP-Blinky is a tiny library that enables Internet protocols (IPv4) to any mbed target hardware by using only a serial port.

The code runs on processors with as little as 8k RAM, for example the Nucleo-L053R8 board.

PPP-Blinky uses the industry-standard PPP (Point-to-Point) Protocol and a tiny "stateless" TCP/IP stack.

No Ethernet Port Required

No ethernet port is required - PPP-Blinky uses a serial port to send IP packets to your PC.

PPP-Blinky emulates a standard dial-up modem and therefore connects to Windows, Linux or Adroid machines.

The code runs on most ARM mbed platforms such as the LPC11U24 shown in the picture below:

/media/uploads/nixnax/blinky-to-laptop1.jpg mbed LPC11u24 acting as a webserver to a Windows laptop.

Webserver

The Webserver and WebSocket functions are ideal for building browser-based GUIs on mbed-enabled hardware.

PPP-Blinky's HTTP webserver works with most web clients such as Internet Explorer, Mozilla Firefox, Google Chrome, Safari, Curl, wget and Lynx as well as Microsoft Powershell Invoke-Webrequest command.

In the image below Firefox web browser displays the main web page embedded into PPP-Blinky's code:

/media/uploads/nixnax/ppp-blinky-firefox.jpg Firefox web browser displays a web page embedded into PPP-Blinky's code

WebSocket Service

WebSocket is the most popular protocol standard for real-time bidirectional TCP/IP communication between clients and servers.
In the image below a small Internet Explorer script has connected to PPP-Blinky's WebSocket Service.
A websocket message was then sent by the browser and was echoed back by the WebSocket, triggering the onmessage event in the script.
The WebSocket service enables bidirectional real-time interaction between PPP-Blinky and any element in the browser DOM via JavaScript.
If you already have PPP-Blinky up and running you can test your WebSocket service using this: http://jsfiddle.net/d26cyuh2/112/embedded/result
Websockets are ideal for building browser-based GUIs for mbed hardware.

/media/uploads/nixnax/ppp-blinky-websocke-2.gif

Trying PPP-Blinky on your mbed board

You will need an mbed-enabled hardware board: https://developer.mbed.org/platforms/

Establish a serial port connection between your host PC and your mbed board. The easiest way is to use mbed hardware with a USB serial debug port. I've tried the ST-Micro Nucleo-L476RG, Nucleo-L152RE, Nucleo-F401RE, Nucleo-L432KC, Nucleo-L053R8, mbed-LPC11U24 and mbed-LPC1768 boards and they all work out of the box. Use the mbed online compiler to compile the software for your target board. Save the compiled binary to your hardware.

Before establishing a network connection, you can verify the operation of the code by opening a terminal program such as Tera Term, and setting the baud rate of the COM port on your mbed board to 115200 baud. LED1 should toggle for every two 0x7E (~) (i.e. tilde) characters you type, as 0x7E is the PPP frame start/end marker. Don't forget to close the port when your'e done testing, or else Windows Dial-up Networking will report that the COM port is in use by another program when you try to connect.

Once you are certain that the serial port and firmware is working, proceed to creating a new network connection on your PC -see below.

Creating a Dial-up Connection in Windows

/media/uploads/nixnax/modem.jpg

Setting up Dial-Up Networking (DUN) on your Windows 7 or 8 PC is essentially a two-step process: First, you create a new modem device, because PPP-blinky partially emulates a standard Windows serial port modem device. Second, you create a new Internet connection (in practice, a new network adapter) which is associated with your new "modem".

Step-by-step description of how to configure Windows for PPP-Blinky here:

/users/nixnax/code/PPP-Blinky/wiki/Configuring-Windows-Dial-Up-Networking

There is also a screen on how to set up Linux dial-up networking near the bottom of this page.

Connecting to PPP-Blinky from your PC

Once Windows networking is configured you can establish a dial-up connection to your mbed board over the USB virtual com port.

The IP address you manually assigned to the new dial-up network adapter (172.10.10.1) functions as a gateway to any valid IP address on that subnet. In the screen capture below, I'm sending pings from the Windows 8 command line to my ST-Micro Nucleo-L476RG board over the USB virtual serial Port. I'm also using a second serial port and Tera Term to capture the debug output from a second serial port on the hardware. The optional debug output from the board prints out the IP source and destination address and the first few bytes of the data payload. Note that the source is the adapter IP address, (172.10.10.1 in this case) and the destination is some other address on that subnet - all packets to the subnet are sent to our mbed hardware. For example, you could also ping 172.10.10.123 or, if your PPP-Blinky is running, simply click on this link: http://172.10.10.123

/media/uploads/nixnax/ping-cap-3.gif

One Million Pings!

In the image below the ICMP ("ping") echo reply service was tested by sending one million pings to ppp-Blinky. This took over two hours.
The ping tool used on the Windows 8 PC was psping.exe from PsTools by Mark Russinovich - http://bit.ly/PingFast
The average reply time for a short ping (1 byte of payload data) was 11 milliseconds at 115200 baud on the $10 Nucleo-L053R8 board - barely enough time for 130 bytes to be sent over the port!

/media/uploads/nixnax/ppp-blinky-ping-results.jpg

Monitoring PPP-Blinky Packets

The image below is from a Microsoft Network Monitor 3.4 capture session.

Responses from PPP-Blinky are shown in blue.

Frame 2 - Internet Explorer at IP 172.10.10.1 (the Dial-Up Adapter IP) requests a TCP connection by sending an S (SYN) flag.
Frame 3 - PPP-Blinky at IP 172.10.10.2 responds with an ACK in frame 3. One direction of the link is now established.
Frame 4 - The PC acknowledges the SYN sent by PPP-Blinky in frame 3. The TCP link is now fully established.
Frame 5 - The browser "pushes" (P flag is set) an HTTP GET request to PPP-Blinky.
Frame 6 - PPP-Blinky responds with a standard HTTP response "pushes" (P flag set) back a small web page. It also sets the A (ACK) flag to acknowledge the message sent in frame 6.
Frame 7 - The PC acknowledges reception of the HTTP payload.
Frame 8 - The PC starts to shut down the TCP connection by sending a FIN flag.
Frame 9 - PPP-Blinky acknowledges the FIN request - the connection is now closed in one direction. It also sets a FIN flag in the response to request closure of the opposite direction of the connection.
Frame 10 - The PC acknowledges the FIN request. The closing of the TCP connection is now confirmed in both directions.

/media/uploads/nixnax/ms-network-monitor-http-get-1.gif

Debug Output

PPP-Blinky can output handy debug information to an optional second serial port.
The image below shows the debug output (Ident, Source, Destination, TCP Flags) for a complete HTTP conversation.
The PC messages are displayed in black. PPP-Blinky messages are blue.
Notice how PPP-blinky automatically inserts a blank line after each full HTTP conversation.

/media/uploads/nixnax/tcp-data-3.gif

Creating a Dial-Up Connection in Linux

The screen below shows the required pppd command to connect to PPP-Blinky from a Linux machine. This was much simpler than Windows! The USB serial port of the mbed LPC1768 board registered as /dev/ttyACM0 on my Linux box. Do a websearch on pppd if you want to learn more about pppd, the Linux PPP handler. Near the bottom of the screen below, two webpages are fetched (/ and /y) by using the curl command on the command line. Gnome Webkit and Firefox work fine, too. Also try echo GET / HTTP/1.1 | nc 172.10.10.2 which uses netcat, the "Swiss army knife" of networking tools. PPP-Blinky was also tested with ApacheBench, the Apache server benchmark software. After 100000 fetches, the mean page fetch rate was reported as 6 page fetches per second for a small page.

/media/uploads/nixnax/pppd-screen.png

Caveats

PPP Blinky is an extremely sparse implementation (1.5k lines) of HTTP,WebSocket,TCP, UDP, ICMP, IPCP and LCP over PPP, requiring around 8kB of RAM. The minimum functionality required to establish connectivity is implemented. These are often acceptable tradeoffs for embedded projects as well as a handy tool to learn the practical details of everyday networking implementations.

main.cpp@12:db0dc91f0231, 2017-01-01 (annotated)

Committer:
nixnax
Date:
Sun Jan 01 01:20:33 2017 +0000
Revision:
12:db0dc91f0231
Parent:
11:f58998c24f0b
Child:
13:d882b8a042b4
UDP partially prints data; Clearer code

Who changed what in which revision?

UserRevisionLine numberNew contents of line
nixnax 0:2cf4880c312a 1 #include "mbed.h"
nixnax 0:2cf4880c312a 2
nixnax 12:db0dc91f0231 3 // Copyright 2016 Nicolas Nackel. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
nixnax 12:db0dc91f0231 4
nixnax 0:2cf4880c312a 5 // Proof-of-concept for TCP/IP using Windows 7/8/10 Dial Up Networking over MBED USB Virtual COM Port
nixnax 0:2cf4880c312a 6
nixnax 4:a469050d5b80 7 // Toggles LED1 every time the PC sends an IP packet over the PPP link
nixnax 4:a469050d5b80 8
nixnax 4:a469050d5b80 9 // Note - turn off all authentication, passwords, compression etc. Simplest link possible.
nixnax 0:2cf4880c312a 10
nixnax 9:0992486d4a30 11 // Handy links
nixnax 6:fba4c2e817b8 12 // http://atari.kensclassics.org/wcomlog.htm
nixnax 6:fba4c2e817b8 13 // https://technet.microsoft.com/en-us/library/cc957992.aspx
nixnax 6:fba4c2e817b8 14 // http://www.sunshine2k.de/coding/javascript/crc/crc_js.html
nixnax 9:0992486d4a30 15 // https://en.wikibooks.org/wiki/Serial_Programming/IP_Over_Serial_Connections
nixnax 6:fba4c2e817b8 16
nixnax 6:fba4c2e817b8 17 Serial pc(USBTX, USBRX); // The USB com port - Set this up as a Dial-Up Modem on your pc
nixnax 4:a469050d5b80 18 Serial xx(PC_10, PC_11); // debug port - use a second USB serial port to monitor
nixnax 0:2cf4880c312a 19
nixnax 9:0992486d4a30 20 #define debug(x) xx.printf( x )
nixnax 9:0992486d4a30 21
nixnax 4:a469050d5b80 22 DigitalOut led1(LED1);
nixnax 4:a469050d5b80 23
nixnax 4:a469050d5b80 24 #define FRAME_7E (0x7e)
nixnax 9:0992486d4a30 25 #define BUFLEN (1<<12)
nixnax 4:a469050d5b80 26 char rxbuf[BUFLEN];
nixnax 4:a469050d5b80 27 char frbuf[3000]; // buffer for ppp frame
nixnax 0:2cf4880c312a 28
nixnax 4:a469050d5b80 29 struct {
nixnax 4:a469050d5b80 30 int online;
nixnax 4:a469050d5b80 31 struct {
nixnax 4:a469050d5b80 32 char * buf;
nixnax 4:a469050d5b80 33 int head;
nixnax 4:a469050d5b80 34 int tail;
nixnax 9:0992486d4a30 35 int total;
nixnax 4:a469050d5b80 36 } rx; // serial port buffer
nixnax 4:a469050d5b80 37 struct {
nixnax 6:fba4c2e817b8 38 int id;
nixnax 4:a469050d5b80 39 int len;
nixnax 4:a469050d5b80 40 int crc;
nixnax 4:a469050d5b80 41 char * buf;
nixnax 4:a469050d5b80 42 } pkt; // ppp buffer
nixnax 4:a469050d5b80 43 } ppp;
nixnax 0:2cf4880c312a 44
nixnax 9:0992486d4a30 45 void pppInitStruct(){ ppp.online=0; ppp.rx.buf=rxbuf; ppp.rx.tail=0; ppp.rx.head=0; ppp.rx.total=0; ppp.pkt.buf=frbuf; ppp.pkt.len=0;}
nixnax 4:a469050d5b80 46
nixnax 4:a469050d5b80 47 int crcG; // frame check sequence (CRC) holder
nixnax 4:a469050d5b80 48 void crcDo(int x){for (int i=0;i<8;i++){crcG=((crcG&1)^(x&1))?(crcG>>1)^0x8408:crcG>>1;x>>=1;}} // crc calculator
nixnax 4:a469050d5b80 49 void crcReset(){crcG=0xffff;} // crc restart
nixnax 9:0992486d4a30 50 int crcBuf(char * buf, int size){crcReset();for(int i=0;i<size;i++)crcDo(*buf++);return crcG;} // crc on a block of memory
nixnax 0:2cf4880c312a 51
nixnax 0:2cf4880c312a 52 void rxHandler() // serial port receive interrupt handler
nixnax 0:2cf4880c312a 53 {
nixnax 4:a469050d5b80 54 ppp.rx.buf[ppp.rx.head]=pc.getc(); // insert in buffer
nixnax 0:2cf4880c312a 55 __disable_irq();
nixnax 4:a469050d5b80 56 ppp.rx.head=(ppp.rx.head+1)&(BUFLEN-1);
nixnax 9:0992486d4a30 57 ppp.rx.total++;
nixnax 0:2cf4880c312a 58 __enable_irq();
nixnax 0:2cf4880c312a 59 }
nixnax 0:2cf4880c312a 60
nixnax 0:2cf4880c312a 61 int pc_readable() // check if buffer has data
nixnax 0:2cf4880c312a 62 {
nixnax 4:a469050d5b80 63 return (ppp.rx.head==ppp.rx.tail) ? 0 : 1 ;
nixnax 0:2cf4880c312a 64 }
nixnax 0:2cf4880c312a 65
nixnax 0:2cf4880c312a 66 int pc_getBuf() // get one character from the buffer
nixnax 0:2cf4880c312a 67 {
nixnax 0:2cf4880c312a 68 if (pc_readable()) {
nixnax 4:a469050d5b80 69 int x = ppp.rx.buf[ ppp.rx.tail ];
nixnax 4:a469050d5b80 70 ppp.rx.tail=(ppp.rx.tail+1)&(BUFLEN-1);
nixnax 0:2cf4880c312a 71 return x;
nixnax 0:2cf4880c312a 72 }
nixnax 0:2cf4880c312a 73 return -1;
nixnax 0:2cf4880c312a 74 }
nixnax 0:2cf4880c312a 75
nixnax 4:a469050d5b80 76 void scanForConnectString(); // scan for connect attempts from pc
nixnax 1:9e03798d4367 77
nixnax 9:0992486d4a30 78 void processFrame(int start, int end) { // process received frame
nixnax 9:0992486d4a30 79 if(start==end) { xx.printf("Null Frame c=%d\n",ppp.rx.total); pc.putc(0x7e); return; }
nixnax 9:0992486d4a30 80 crcReset();
nixnax 9:0992486d4a30 81 char * dest = ppp.pkt.buf;
nixnax 9:0992486d4a30 82 ppp.pkt.len=0;
nixnax 9:0992486d4a30 83 int unstuff=0;
nixnax 9:0992486d4a30 84 for (int i=start; i<end; i++) {
nixnax 9:0992486d4a30 85 if (unstuff==0) {
nixnax 9:0992486d4a30 86 if (rxbuf[i]==0x7d) unstuff=1;
nixnax 9:0992486d4a30 87 else { *dest++ = rxbuf[i]; ppp.pkt.len++; crcDo(rxbuf[i]);}
nixnax 12:db0dc91f0231 88 } else { // unstuff
nixnax 9:0992486d4a30 89 *dest++ = rxbuf[i]^0x20; ppp.pkt.len++; crcDo((int)rxbuf[i]^0x20);
nixnax 9:0992486d4a30 90 unstuff=0;
nixnax 9:0992486d4a30 91 }
nixnax 9:0992486d4a30 92 }
nixnax 9:0992486d4a30 93 ppp.pkt.crc = crcG & 0xffff;
nixnax 9:0992486d4a30 94 if (ppp.pkt.crc == 0xf0b8) { // check for good CRC
nixnax 9:0992486d4a30 95 void determinePacketType(); // declare early
nixnax 9:0992486d4a30 96 determinePacketType();
nixnax 12:db0dc91f0231 97 } else { // crc error
nixnax 12:db0dc91f0231 98 xx.printf("CRC is %x Len is %d\n",ppp.pkt.crc,ppp.pkt.len);
nixnax 9:0992486d4a30 99 for(int i=0;i<ppp.pkt.len;i++)xx.printf("%02x ", ppp.pkt.buf[i]);
nixnax 12:db0dc91f0231 100 xx.printf("\n");
nixnax 9:0992486d4a30 101 }
nixnax 9:0992486d4a30 102 }
nixnax 9:0992486d4a30 103
nixnax 11:f58998c24f0b 104 void dumpFrame() {
nixnax 11:f58998c24f0b 105 for(int i=0;i<ppp.pkt.len/2;i++) xx.printf("%02x ", ppp.pkt.buf[i]);
nixnax 11:f58998c24f0b 106 xx.printf(" C %02x %02x L=%d\n", ppp.pkt.crc&0xff, (ppp.pkt.crc>>8)&0xff, ppp.pkt.len);
nixnax 11:f58998c24f0b 107 }
nixnax 9:0992486d4a30 108
nixnax 9:0992486d4a30 109 void sendFrame(){
nixnax 9:0992486d4a30 110 int crc = crcBuf(ppp.pkt.buf, ppp.pkt.len-2); // get crc
nixnax 12:db0dc91f0231 111 ppp.pkt.buf[ ppp.pkt.len-2 ] = (~crc>>0); // fcs lo (crc)
nixnax 12:db0dc91f0231 112 ppp.pkt.buf[ ppp.pkt.len-1 ] = (~crc>>8); // fcs hi (crc)
nixnax 12:db0dc91f0231 113 pc.putc(0x7e); // frame start flag
nixnax 9:0992486d4a30 114 for(int i=0;i<ppp.pkt.len;i++) {
nixnax 11:f58998c24f0b 115 //xx.printf( "%2x ", ppp.pkt.buf[i]);
nixnax 9:0992486d4a30 116 unsigned int cc = (unsigned int)ppp.pkt.buf[i];
nixnax 9:0992486d4a30 117 if (cc>32) pc.putc(cc); else {pc.putc(0x7d); pc.putc(cc+32);}
nixnax 9:0992486d4a30 118 }
nixnax 12:db0dc91f0231 119 pc.putc(0x7e); // frame end flag
nixnax 9:0992486d4a30 120 }
nixnax 9:0992486d4a30 121
nixnax 9:0992486d4a30 122 void ipRequestHandler(){
nixnax 9:0992486d4a30 123 debug("IPCP Conf ");
nixnax 9:0992486d4a30 124 if ( ppp.pkt.buf[7] != 4 ) {
nixnax 9:0992486d4a30 125 debug("Rej\n"); // reject if any options are requested
nixnax 9:0992486d4a30 126 ppp.pkt.buf[4]=4;
nixnax 9:0992486d4a30 127 sendFrame();
nixnax 9:0992486d4a30 128 } else {
nixnax 9:0992486d4a30 129 debug("Ack\n");
nixnax 9:0992486d4a30 130 ppp.pkt.buf[4]=2; // ack the minimum
nixnax 9:0992486d4a30 131 sendFrame(); // acknowledge
nixnax 12:db0dc91f0231 132 debug("IPCP Ask\n");
nixnax 9:0992486d4a30 133 // send our own request now
nixnax 12:db0dc91f0231 134 ppp.pkt.buf[4]=1; // request no options
nixnax 9:0992486d4a30 135 ppp.pkt.buf[5]++; // next sequence
nixnax 9:0992486d4a30 136 sendFrame(); // this is our request
nixnax 9:0992486d4a30 137 }
nixnax 9:0992486d4a30 138 }
nixnax 9:0992486d4a30 139
nixnax 9:0992486d4a30 140 void ipAckHandler(){ debug("IPCP Grant\n"); }
nixnax 9:0992486d4a30 141
nixnax 9:0992486d4a30 142 void ipNackHandler(){ debug("IPCP Nack\n"); }
nixnax 9:0992486d4a30 143
nixnax 9:0992486d4a30 144 void ipDefaultHandler(){ debug("IPCP Other\n"); }
nixnax 9:0992486d4a30 145
nixnax 9:0992486d4a30 146 void IPCPframe() {
nixnax 9:0992486d4a30 147 led1 = ppp.pkt.buf[5] & 1; // This is the sequence number so the led blinks on packets
nixnax 9:0992486d4a30 148 //ppp.pkt.id = ppp.pkt.buf[5]; // remember the sequence number
nixnax 9:0992486d4a30 149 int code = ppp.pkt.buf[4]; // packet type is here
nixnax 9:0992486d4a30 150 switch (code) {
nixnax 9:0992486d4a30 151 case 1: ipRequestHandler(); break;
nixnax 9:0992486d4a30 152 case 2: ipAckHandler(); break;
nixnax 9:0992486d4a30 153 case 3: ipNackHandler(); break;
nixnax 9:0992486d4a30 154 default: ipDefaultHandler();
nixnax 9:0992486d4a30 155 }
nixnax 9:0992486d4a30 156 }
nixnax 9:0992486d4a30 157
nixnax 10:74f8233f72c0 158 void UDPpacket() {
nixnax 12:db0dc91f0231 159 char * udpPkt = ppp.pkt.buf+4; // udp packet start
nixnax 12:db0dc91f0231 160 //char * pktLen = udpPkt+2; // total packet length
nixnax 12:db0dc91f0231 161 int headerSize = (( udpPkt[0]&0xf)*4);
nixnax 12:db0dc91f0231 162 char * udpBlock = udpPkt + headerSize; // udp info start
nixnax 12:db0dc91f0231 163 char * udpSrc = udpBlock; // source port
nixnax 12:db0dc91f0231 164 char * udpDst = udpBlock+2; // destination port
nixnax 12:db0dc91f0231 165 char * udpLen = udpBlock+4; // udp data length
nixnax 12:db0dc91f0231 166 char * udpInf = udpBlock+8; // actual start of info
nixnax 12:db0dc91f0231 167 //char * udpSum = udpBlock+6; // udp checksum
nixnax 12:db0dc91f0231 168 //int packetLength = (pktLen[0]<<8) | pktLen[1]; // udp total packet length
nixnax 12:db0dc91f0231 169 int srcPort = (udpSrc[0]<<8) | udpSrc[1];
nixnax 12:db0dc91f0231 170 int dstPort = (udpDst[0]<<8) | udpDst[1];
nixnax 12:db0dc91f0231 171 char * srcIP = udpPkt+12; // udp src addr
nixnax 12:db0dc91f0231 172 char * dstIP = udpPkt+16; // udp dst addr
nixnax 12:db0dc91f0231 173 #define UDP_HEADER_SIZE 8
nixnax 12:db0dc91f0231 174 int udpLength = ((udpLen[0]<<8) | udpLen[1]) - UDP_HEADER_SIZE; // size of the actual udp data
nixnax 12:db0dc91f0231 175 xx.printf("UDP %d.%d.%d.%d:%d ", srcIP[0],srcIP[1],srcIP[2],srcIP[3],srcPort);
nixnax 12:db0dc91f0231 176 xx.printf("%d.%d.%d.%d:%d ", dstIP[1],dstIP[1],dstIP[1],dstIP[1],dstPort);
nixnax 12:db0dc91f0231 177 xx.printf("Len %d ", udpLength);
nixnax 12:db0dc91f0231 178 int printSize = udpLength > 20 ? 20 : udpLength;
nixnax 12:db0dc91f0231 179 for (int i=0; i<printSize; i++) { xx.putc( udpInf[i]); } // printf first 20 characters of the data
nixnax 12:db0dc91f0231 180 xx.printf("\n");
nixnax 12:db0dc91f0231 181 }
nixnax 11:f58998c24f0b 182
nixnax 11:f58998c24f0b 183 int dataCheckSum(char * ptr, int len) {
nixnax 11:f58998c24f0b 184 int sum=0;
nixnax 11:f58998c24f0b 185 for (int i=0;i<len/2;i++) {
nixnax 11:f58998c24f0b 186 int hi = *ptr; ptr++;
nixnax 11:f58998c24f0b 187 int lo = *ptr; ptr++;
nixnax 11:f58998c24f0b 188 int val = ( lo & 0xff ) | ( (hi<<8) & 0xff00 );
nixnax 11:f58998c24f0b 189 sum = sum + val;
nixnax 11:f58998c24f0b 190 }
nixnax 11:f58998c24f0b 191 sum = sum + (sum>>16);
nixnax 12:db0dc91f0231 192 return ~sum;
nixnax 11:f58998c24f0b 193 }
nixnax 11:f58998c24f0b 194
nixnax 11:f58998c24f0b 195 void headerCheckSum() {
nixnax 11:f58998c24f0b 196 int len =(ppp.pkt.buf[4]&0xf)*4; // length of header in bytes
nixnax 11:f58998c24f0b 197 char * ptr = ppp.pkt.buf+4; // start of ip packet
nixnax 11:f58998c24f0b 198 int sum=0;
nixnax 11:f58998c24f0b 199
nixnax 11:f58998c24f0b 200 for (int i=0;i<len/2;i++) {
nixnax 11:f58998c24f0b 201 int hi = *ptr; ptr++;
nixnax 11:f58998c24f0b 202 int lo = *ptr; ptr++;
nixnax 11:f58998c24f0b 203 int val = ( lo & 0xff ) | ( (hi<<8) & 0xff00 );
nixnax 11:f58998c24f0b 204 sum = sum + val;
nixnax 11:f58998c24f0b 205 }
nixnax 11:f58998c24f0b 206 sum = sum + (sum>>16);
nixnax 11:f58998c24f0b 207 sum = ~sum;
nixnax 11:f58998c24f0b 208 ppp.pkt.buf[14]= (sum>>8);
nixnax 11:f58998c24f0b 209 ppp.pkt.buf[15]= (sum );
nixnax 9:0992486d4a30 210 }
nixnax 9:0992486d4a30 211
nixnax 11:f58998c24f0b 212 void ICMPpacket() { // internet control message protocol
nixnax 12:db0dc91f0231 213 char * ipPkt = ppp.pkt.buf+4; // ip packet start
nixnax 12:db0dc91f0231 214 char * pktLen = ipPkt+2;
nixnax 12:db0dc91f0231 215 int packetLength = (pktLen[0]<<8) | pktLen[1]; // icmp packet length
nixnax 12:db0dc91f0231 216 int headerSize = (( ipPkt[0]&0xf)*4);
nixnax 12:db0dc91f0231 217 char * icmpType = ipPkt + headerSize; // icmp data start
nixnax 12:db0dc91f0231 218 char * icmpData = icmpType; // icmp packet type
nixnax 12:db0dc91f0231 219 char * icmpSum = icmpData+2; // icmp checksum
nixnax 12:db0dc91f0231 220 #define ICMP_TYPE_PING_REQUEST 8
nixnax 12:db0dc91f0231 221 if ( icmpType[0] == ICMP_TYPE_PING_REQUEST ) {
nixnax 12:db0dc91f0231 222 xx.printf("ICMP PING\n");
nixnax 12:db0dc91f0231 223 char * ipTTL = ipPkt+8; // time to live
nixnax 12:db0dc91f0231 224 ipTTL[0]--; // decrement time to live
nixnax 12:db0dc91f0231 225 char * srcAdr = ipPkt+12;
nixnax 12:db0dc91f0231 226 char * dstAdr = ipPkt+16;
nixnax 11:f58998c24f0b 227 char src[4]; char dst[4];
nixnax 12:db0dc91f0231 228 memcpy(src, srcAdr,4);
nixnax 12:db0dc91f0231 229 memcpy(dst, dstAdr,4);
nixnax 12:db0dc91f0231 230 memcpy(srcAdr, dst,4);
nixnax 12:db0dc91f0231 231 memcpy(dstAdr, src,4); // swap src & dest ip
nixnax 12:db0dc91f0231 232 char * chkSum = ipPkt+10;
nixnax 12:db0dc91f0231 233 chkSum[0]=0; chkSum[1]=0;
nixnax 12:db0dc91f0231 234 headerCheckSum(); // new ip header checksum
nixnax 12:db0dc91f0231 235 #define ICMP_TYPE_ECHO_REPLY 0
nixnax 12:db0dc91f0231 236 icmpType[0]=ICMP_TYPE_ECHO_REPLY; // icmp echo replay
nixnax 12:db0dc91f0231 237 icmpSum[0]=0; icmpSum[1]=0; // zero the checksum for recalculation
nixnax 12:db0dc91f0231 238 int dataLength = packetLength - headerSize; // length of ICMP data portion
nixnax 12:db0dc91f0231 239 int sum = dataCheckSum( icmpData, dataLength); // new data portion checksum
nixnax 12:db0dc91f0231 240 icmpSum[0]=sum>>8; icmpSum[1]=sum; // new checksum for ICMP data portion
nixnax 11:f58998c24f0b 241 sendFrame();
nixnax 12:db0dc91f0231 242 } else {
nixnax 12:db0dc91f0231 243 xx.printf("ICMP type=%d \n", icmpType[0]);
nixnax 11:f58998c24f0b 244 }
nixnax 11:f58998c24f0b 245 }
nixnax 11:f58998c24f0b 246
nixnax 11:f58998c24f0b 247 void IGMPpacket() { // internet group management protocol
nixnax 11:f58998c24f0b 248 xx.printf("IGMP type=%d \n", ppp.pkt.buf[28]);
nixnax 11:f58998c24f0b 249 }
nixnax 11:f58998c24f0b 250
nixnax 11:f58998c24f0b 251 void TCPpacket() {
nixnax 11:f58998c24f0b 252 debug("TCP\n");
nixnax 10:74f8233f72c0 253 /*
nixnax 11:f58998c24f0b 254 switch (protocol) {
nixnax 11:f58998c24f0b 255 case 2: TCPsyn(); break;
nixnax 11:f58998c24f0b 256 case 17: TCPack(); break;
nixnax 11:f58998c24f0b 257 case 6: TCPpacket(); break;
nixnax 11:f58998c24f0b 258 default: debug( "Other \n");
nixnax 11:f58998c24f0b 259 }
nixnax 10:74f8233f72c0 260 */
nixnax 10:74f8233f72c0 261 }
nixnax 10:74f8233f72c0 262
nixnax 11:f58998c24f0b 263 void otherProtocol() {
nixnax 12:db0dc91f0231 264 debug("Other IP protocol");
nixnax 11:f58998c24f0b 265 }
nixnax 11:f58998c24f0b 266
nixnax 10:74f8233f72c0 267 void IPframe() {
nixnax 10:74f8233f72c0 268 int protocol = ppp.pkt.buf[13];
nixnax 10:74f8233f72c0 269 switch (protocol) {
nixnax 11:f58998c24f0b 270 case 1: ICMPpacket(); break;
nixnax 11:f58998c24f0b 271 case 2: IGMPpacket(); break;
nixnax 11:f58998c24f0b 272 case 17: UDPpacket(); break;
nixnax 11:f58998c24f0b 273 case 6: TCPpacket(); break;
nixnax 11:f58998c24f0b 274 default: otherProtocol();
nixnax 10:74f8233f72c0 275 }
nixnax 10:74f8233f72c0 276 //xx.printf("IP frame proto %3d len %4d %d.%d.%d.%d %d.%d.%d.%d\n", ppp.pkt.buf[13],(ppp.pkt.buf[6]<<8)+ppp.pkt.buf[7],ppp.pkt.buf[16],ppp.pkt.buf[17],ppp.pkt.buf[18],ppp.pkt.buf[19],ppp.pkt.buf[20],ppp.pkt.buf[21],ppp.pkt.buf[22],ppp.pkt.buf[23] );
nixnax 10:74f8233f72c0 277 }
nixnax 9:0992486d4a30 278
nixnax 9:0992486d4a30 279 void LCPconfReq() {
nixnax 11:f58998c24f0b 280 debug("LCP Config ");
nixnax 9:0992486d4a30 281 if (ppp.pkt.buf[7] != 4) {
nixnax 11:f58998c24f0b 282 ppp.pkt.buf[4]=4; // allow only no options
nixnax 11:f58998c24f0b 283 debug("Reject\n");
nixnax 9:0992486d4a30 284 sendFrame();
nixnax 9:0992486d4a30 285 } else {
nixnax 9:0992486d4a30 286 ppp.pkt.buf[4]=2; // ack zero conf
nixnax 9:0992486d4a30 287 debug("Ack\n");
nixnax 9:0992486d4a30 288 sendFrame();
nixnax 10:74f8233f72c0 289 debug("LCP Ask\n");
nixnax 11:f58998c24f0b 290 ppp.pkt.buf[4]=1; // request no options
nixnax 9:0992486d4a30 291 sendFrame();
nixnax 9:0992486d4a30 292 }
nixnax 9:0992486d4a30 293 }
nixnax 9:0992486d4a30 294
nixnax 9:0992486d4a30 295 void LCPconfAck() {
nixnax 9:0992486d4a30 296 debug("LCP Ack\n");
nixnax 9:0992486d4a30 297 }
nixnax 9:0992486d4a30 298
nixnax 9:0992486d4a30 299 void LCPend(){
nixnax 9:0992486d4a30 300 debug("LCP End\n");
nixnax 12:db0dc91f0231 301 ppp.online=0; // start hunting for connect string again
nixnax 9:0992486d4a30 302 ppp.pkt.buf[4]=6;
nixnax 12:db0dc91f0231 303 sendFrame(); // acknowledge
nixnax 9:0992486d4a30 304 }
nixnax 9:0992486d4a30 305
nixnax 9:0992486d4a30 306 void LCPother(){
nixnax 9:0992486d4a30 307 debug("LCP Other\n");
nixnax 12:db0dc91f0231 308 dumpFrame();
nixnax 9:0992486d4a30 309 }
nixnax 9:0992486d4a30 310
nixnax 9:0992486d4a30 311 void LCPframe(){
nixnax 9:0992486d4a30 312 int code = ppp.pkt.buf[4];
nixnax 9:0992486d4a30 313 switch (code) {
nixnax 12:db0dc91f0231 314 case 1: LCPconfReq(); break; // config request
nixnax 12:db0dc91f0231 315 case 2: LCPconfAck(); break; // config ack
nixnax 12:db0dc91f0231 316 case 5: LCPend(); break; // end connection
nixnax 12:db0dc91f0231 317 default: LCPother();
nixnax 9:0992486d4a30 318 }
nixnax 9:0992486d4a30 319 }
nixnax 9:0992486d4a30 320
nixnax 12:db0dc91f0231 321 void discardedFrame() {
nixnax 12:db0dc91f0231 322 xx.printf("Dropping frame %02x %02x %02x %02x\n", ppp.pkt.buf[0],ppp.pkt.buf[1],ppp.pkt.buf[2],ppp.pkt.buf[3] );
nixnax 9:0992486d4a30 323 }
nixnax 9:0992486d4a30 324
nixnax 9:0992486d4a30 325 void determinePacketType() {
nixnax 9:0992486d4a30 326 if ( ppp.pkt.buf[0] != 0xff ) {debug("byte0 != ff\n"); return;}
nixnax 9:0992486d4a30 327 if ( ppp.pkt.buf[1] != 3 ) {debug("byte1 != 3\n"); return;}
nixnax 9:0992486d4a30 328 if ( ppp.pkt.buf[3] != 0x21 ) {debug("byte2 != 21\n"); return;}
nixnax 9:0992486d4a30 329 int packetType = ppp.pkt.buf[2];
nixnax 9:0992486d4a30 330 switch (packetType) {
nixnax 12:db0dc91f0231 331 case 0xc0: LCPframe(); break; // link control
nixnax 12:db0dc91f0231 332 case 0x80: IPCPframe(); break; // IP control
nixnax 12:db0dc91f0231 333 case 0x00: IPframe(); break; // IP itself
nixnax 12:db0dc91f0231 334 default: discardedFrame();
nixnax 9:0992486d4a30 335 }
nixnax 9:0992486d4a30 336 }
nixnax 9:0992486d4a30 337
nixnax 9:0992486d4a30 338 void scanForConnectString() {
nixnax 9:0992486d4a30 339 if ( ppp.online==0 ) {
nixnax 9:0992486d4a30 340 char * clientFound = strstr( rxbuf, "CLIENTCLIENT" ); // look for PC string
nixnax 9:0992486d4a30 341 if( clientFound ) {
nixnax 9:0992486d4a30 342 strcpy( clientFound, "FOUND!FOUND!" ); // overwrite so we don't get fixated
nixnax 9:0992486d4a30 343 pc.printf("CLIENTSERVER"); // respond to PC
nixnax 9:0992486d4a30 344 ppp.online=1; // we can stop looking for the string
nixnax 9:0992486d4a30 345 debug("Connect string found\n");
nixnax 9:0992486d4a30 346 }
nixnax 9:0992486d4a30 347 }
nixnax 9:0992486d4a30 348 }
nixnax 9:0992486d4a30 349
nixnax 0:2cf4880c312a 350 int main()
nixnax 0:2cf4880c312a 351 {
nixnax 12:db0dc91f0231 352 pc.baud(115200);
nixnax 4:a469050d5b80 353 xx.baud(115200);
nixnax 9:0992486d4a30 354 xx.puts("\x1b[2J\x1b[HReady\n"); // VT100 code for clear screen & home
nixnax 4:a469050d5b80 355
nixnax 9:0992486d4a30 356 pppInitStruct(); // initialize all the PPP properties
nixnax 4:a469050d5b80 357
nixnax 9:0992486d4a30 358 pc.attach(&rxHandler,Serial::RxIrq); // start the receive handler
nixnax 4:a469050d5b80 359
nixnax 9:0992486d4a30 360 int frameStartIndex, frameEndIndex; int frameBusy=0;
nixnax 4:a469050d5b80 361
nixnax 0:2cf4880c312a 362 while(1) {
nixnax 9:0992486d4a30 363 if ( ppp.online==0 ) scanForConnectString(); // try to connect
nixnax 0:2cf4880c312a 364 while ( pc_readable() ) {
nixnax 1:9e03798d4367 365 int rx = pc_getBuf();
nixnax 9:0992486d4a30 366 wait(0.001);
nixnax 4:a469050d5b80 367 if (frameBusy) {
nixnax 4:a469050d5b80 368 if (rx==FRAME_7E) {
nixnax 4:a469050d5b80 369 frameBusy=0; // done gathering frame
nixnax 4:a469050d5b80 370 frameEndIndex=ppp.rx.tail-1; // remember where frame ends
nixnax 4:a469050d5b80 371 void processFrame(int start, int end); // process a received frame
nixnax 4:a469050d5b80 372 processFrame(frameStartIndex, frameEndIndex);
nixnax 4:a469050d5b80 373 }
nixnax 4:a469050d5b80 374 }
nixnax 4:a469050d5b80 375 else {
nixnax 4:a469050d5b80 376 if (rx==FRAME_7E) {
nixnax 4:a469050d5b80 377 frameBusy=1; // start gathering frame
nixnax 9:0992486d4a30 378 frameStartIndex=ppp.rx.tail; // remember where frame started
nixnax 4:a469050d5b80 379 }
nixnax 0:2cf4880c312a 380 }
nixnax 4:a469050d5b80 381 }
nixnax 7:ab147f5e97ac 382 }
nixnax 7:ab147f5e97ac 383 }