PPP-Blinky - Small Internet Protocol Stack using a standard se…

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Nicolas Nackel / Mbed 2 deprecated PPP-Blinky

Small Internet Protocol Stack using a standard serial port.

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.

PPP-Blinky/ppp-blinky.cpp@175:b4e6f8a6fe00, 2017-09-06 (annotated)

Committer:: nixnax
Date:: Wed Sep 06 21:10:01 2017 +0000
Revision:: 175:b4e6f8a6fe00
Parent:: 173:6774a0c851c4
Child:: 176:011dbb3f7d03

Moved ppp structure.

Who changed what in which revision?

User	Revision	Line number	New contents of line
nixnax	142:54d1543e23e5	1	// PPP-Blinky - "The Most Basic Internet Of a Thing"
nixnax	142:54d1543e23e5	2	// A Tiny HTTP Webserver Using Windows XP/7/8/10/Linux Dial-Up Networking Over A Serial Port.
nixnax	142:54d1543e23e5	3	// Receives UDP packets and responds to ping (ICMP Echo requests)
nixnax	142:54d1543e23e5	4	// WebSocket Service - see https://en.wikipedia.org/wiki/WebSocket
nixnax	142:54d1543e23e5	5
nixnax	142:54d1543e23e5	6	// Copyright 2016/2017 Nicolas Nackel aka Nixnax. 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	142:54d1543e23e5	7
nixnax	142:54d1543e23e5	8	// Notes and Instructions
nixnax	142:54d1543e23e5	9	// http://bit.ly/PPP-Blinky-Instructions
nixnax	142:54d1543e23e5	10	// http://bit.ly/win-rasdial-config
nixnax	142:54d1543e23e5	11
nixnax	142:54d1543e23e5	12	// Handy reading material
nixnax	142:54d1543e23e5	13	// https://technet.microsoft.com/en-us/library/cc957992.aspx
nixnax	142:54d1543e23e5	14	// https://en.wikibooks.org/wiki/Serial_Programming/IP_Over_Serial_Connections
nixnax	142:54d1543e23e5	15	// http://atari.kensclassics.org/wcomlog.htm
nixnax	142:54d1543e23e5	16
nixnax	142:54d1543e23e5	17	// Handy tools
nixnax	142:54d1543e23e5	18	// https://ttssh2.osdn.jp/index.html.en - Tera Term, a good terminal program to monitor the debug output from the second serial port with!
nixnax	142:54d1543e23e5	19	// https://www.microsoft.com/en-us/download/details.aspx?id=4865 - Microsoft network monitor - real-time monitoring of PPP packets
nixnax	142:54d1543e23e5	20	// http://pingtester.net/ - nice tool for high rate ping testing
nixnax	142:54d1543e23e5	21	// http://www.sunshine2k.de/coding/javascript/crc/crc_js.html - Correctly calculates the 16-bit FCS (crc) on our frames (Choose CRC16_CCITT_FALSE), then custom relected-in=1, reflected-out=1
nixnax	142:54d1543e23e5	22	// https://technet.microsoft.com/en-us/sysinternals/pstools.aspx - psping for fast testing of ICMP ping function
nixnax	142:54d1543e23e5	23	// https://eternallybored.org/misc/netcat/ - use netcat -u 172.10.10.1 80 to send/receive UDP packets from PPP-Blinky
nixnax	142:54d1543e23e5	24	// Windows Powershell invoke-webrequest command - use it to stress test the webserver like this: while (1){ invoke-webrequest -uri 172.10.10.1/x }
nixnax	142:54d1543e23e5	25
nixnax	142:54d1543e23e5	26	// Connecting PPP-Blinky to Linux
nixnax	142:54d1543e23e5	27	// PPP-Blinky can be made to talk to Linux - tested on Fedora - the following command, which uses pppd, works:
nixnax	142:54d1543e23e5	28	// pppd /dev/ttyACM0 115200 debug dump local passive noccp novj nodetach nocrtscts 172.10.10.1:172.10.10.2
nixnax	142:54d1543e23e5	29	// in the above command 172.10.10.1 is the adapter IP, and 172.10.10.2 is the IP of PPP-Blinky.
nixnax	142:54d1543e23e5	30	// See also https://en.wikipedia.org/wiki/Point-to-Point_Protocol_daemon
nixnax	142:54d1543e23e5	31
nixnax	142:54d1543e23e5	32	// Special pages when PPP-Blinky is running
nixnax	142:54d1543e23e5	33	// 172.10.10.2 root page
nixnax	143:c5019f856a56	34	// 172.10.10.2/x returns a number that increments every time you request a page - this is handy for testing
nixnax	146:a45f49a2b29c	35	// 172.10.10.2/xb also returns a number, but issues a fast refresh meta command. This allows you to use your browser to benchmark page load speed
nixnax	142:54d1543e23e5	36	// 172.10.10.2/ws a simple WebSocket demo
nixnax	142:54d1543e23e5	37	// http://jsfiddle.net/d26cyuh2/ more complete WebSocket demo in JSFiddle
nixnax	142:54d1543e23e5	38
nixnax	142:54d1543e23e5	39	// Ok, enough talking, time to check out some code!!
nixnax	142:54d1543e23e5	40
nixnax	142:54d1543e23e5	41	#include "ppp-blinky.h"
nixnax	142:54d1543e23e5	42
nixnax	142:54d1543e23e5	43	// The #define below enables/disables a second (OPTIONAL) serial port that prints out interesting diagnostic messages.
nixnax	146:a45f49a2b29c	44	// Change to SERIAL_PORT_MONITOR_YES to enable diagnostics messages. You need to wire a second serial port to your mbed hardware to monitor the debug output.
nixnax	142:54d1543e23e5	45	// Using the second serial port will slow down packet response time
nixnax	142:54d1543e23e5	46	// Note - the LPC11U24 does NOT have a second serial port
nixnax	146:a45f49a2b29c	47
nixnax	169:ee90aed3a735	48	#define SERIAL_PORT_MONITOR_NO /* change to SERIAL_PORT_MONITOR_YES for debug messages */
nixnax	142:54d1543e23e5	49
nixnax	142:54d1543e23e5	50	// here we define the OPTIONAL, second debug serial port for various mbed target boards
nixnax	142:54d1543e23e5	51	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	52	#if defined(TARGET_LPC1768)
nixnax	142:54d1543e23e5	53	Serial xx(p9, p10); // Second serial port on LPC1768 - not required to run, if you get compile error here, change #define SERIAL_PORT_MONITOR_YES to #define SERIAL_PORT_MONITOR_NO
nixnax	142:54d1543e23e5	54	#elif defined(TARGET_NUCLEO_F446RE) \|\| defined(TARGET_NUCLEO_L152RE) \|\| defined(TARGET_NUCLEO_L053R8) \|\| defined(TARGET_NUCLEO_L476RG) \|\| defined(TARGET_NUCLEO_F401RE)
nixnax	142:54d1543e23e5	55	Serial xx(PC_10, PC_11); // Second serial port on NUCLEO boards - not required to run, if you get compile error here, change #define SERIAL_PORT_MONITOR_YES to #define SERIAL_PORT_MONITOR_NO
nixnax	142:54d1543e23e5	56	#elif defined(TARGET_LPC11U24)
nixnax	142:54d1543e23e5	57	#error The LPC11U24 does not have a second serial port to use for debugging - change SERIAL_PORT_MONITOR_YES back to SERIAL_PORT_MONITOR_NO
nixnax	142:54d1543e23e5	58	#elif defined (TARGET_KL46Z) \|\| (TARGET_KL25Z)
nixnax	142:54d1543e23e5	59	Serial xx(PTE0,PTE1); // Second serial port on FRDM-KL46Z board
nixnax	142:54d1543e23e5	60	#elif defined(YOUR_TARGET_BOARD_NAME_HERE)
nixnax	142:54d1543e23e5	61	// change the next line to YOUR target board's second serial port pin definition if it's not present - and if it works, please send it to me - thanks!!!
nixnax	142:54d1543e23e5	62	Serial xx(p9, p10); // change this to YOUR board second serial port pin definition - and please send it to me if it works!!!
nixnax	142:54d1543e23e5	63	#else
nixnax	142:54d1543e23e5	64	#error Add your target board's second serial port here if you want to use debugging - or simply change SERIAL_PORT_MONITOR_YES to SERIAL_PORT_MONITOR_NO
nixnax	142:54d1543e23e5	65	#endif
nixnax	142:54d1543e23e5	66	#define debugPrintf(x...) xx.printf (x) /* if we have a serial port we print debug messages */
nixnax	142:54d1543e23e5	67	#define debugPutc(x...) xx.putc(x)
nixnax	142:54d1543e23e5	68	#define debugBaudRate(x...) xx.baud(x)
nixnax	142:54d1543e23e5	69	#else
nixnax	142:54d1543e23e5	70	// if we don't have a debug port the debug print functions do nothing
nixnax	142:54d1543e23e5	71	#define debugPrintf(x...) {}
nixnax	142:54d1543e23e5	72	#define debugPutc(x...) {}
nixnax	142:54d1543e23e5	73	#define debugBaudRate(x...) {}
nixnax	142:54d1543e23e5	74	#endif
nixnax	142:54d1543e23e5	75
nixnax	142:54d1543e23e5	76	// verbosity flags used in debug printouts - change to 1 to see increasingly more detailed debug info.
nixnax	142:54d1543e23e5	77	#define v0 1
nixnax	142:54d1543e23e5	78	#define v1 0
nixnax	142:54d1543e23e5	79	#define v2 0
nixnax	142:54d1543e23e5	80	#define IP_HEADER_DUMP_YES /* YES for ip header dump */
nixnax	142:54d1543e23e5	81	#define TCP_HEADER_DUMP_YES /* YES for tcp header dump */
nixnax	142:54d1543e23e5	82
nixnax	142:54d1543e23e5	83	// this is the webpage we serve when we get an HTTP request to root (/)
nixnax	142:54d1543e23e5	84	// keep size under ~900 bytes to fit into a single PPP packet
nixnax	142:54d1543e23e5	85
nixnax	142:54d1543e23e5	86	const static char rootWebPage[] = "\
nixnax	142:54d1543e23e5	87	<!DOCTYPE html>\
nixnax	142:54d1543e23e5	88	<html>\
nixnax	142:54d1543e23e5	89	<head>\
nixnax	146:a45f49a2b29c	90	<title>mbed PPP-Blinky</title>\r\n\
nixnax	146:a45f49a2b29c	91	<script>\r\n\
nixnax	142:54d1543e23e5	92	window.onload=function(){\
nixnax	142:54d1543e23e5	93	setInterval(function(){function x(){return document.getElementById('w');};\
nixnax	146:a45f49a2b29c	94	x().textContent=parseInt(x().textContent)+1;},100);};\r\n\
nixnax	146:a45f49a2b29c	95	</script>\r\n\
nixnax	142:54d1543e23e5	96	</head>\
nixnax	142:54d1543e23e5	97	<body style=\"font-family: sans-serif; font-size:20px; text-align:center; color:#807070\">\
nixnax	142:54d1543e23e5	98	<h1>mbed PPP-Blinky Up and Running</h1>\
nixnax	142:54d1543e23e5	99	<h1 id=\"w\">0</h1>\
nixnax	142:54d1543e23e5	100	<h1><a href=\"http://bit.ly/pppBlink2\">Source on mbed</a></h1>\
nixnax	142:54d1543e23e5	101	<h1><a href=\"/ws\">WebSocket Demo</a></h1>\
nixnax	142:54d1543e23e5	102	<h1><a href=\"/x\">Benchmark 1</a></h1>\
nixnax	142:54d1543e23e5	103	<h1><a href=\"/xb\">Benchmark 2</a></h1>\
nixnax	142:54d1543e23e5	104	<h1><a href=\"http://jsfiddle.net/d26cyuh2/\">JSFiddle Demo</a></h1>\
nixnax	142:54d1543e23e5	105	</body>\
nixnax	146:a45f49a2b29c	106	</html>\r\n"; // size = 644 bytes plus 1 null byte = 645 bytes
nixnax	142:54d1543e23e5	107
nixnax	167:ff8a2d8beeb1	108	// this is a websocket demo html page we serve when GET /ws is requested
nixnax	142:54d1543e23e5	109	const static char webSocketPage[] = "\
nixnax	142:54d1543e23e5	110	<!DOCTYPE html>\
nixnax	142:54d1543e23e5	111	<html>\
nixnax	142:54d1543e23e5	112	<head>\
nixnax	142:54d1543e23e5	113	<title>mbed PPP-Blinky</title>\
nixnax	142:54d1543e23e5	114	<script>\
nixnax	142:54d1543e23e5	115	window.onload=function(){\
nixnax	142:54d1543e23e5	116	var url=\"ws://172.10.10.2\";\
nixnax	142:54d1543e23e5	117	var sts=document.getElementById(\"sts\");\
nixnax	142:54d1543e23e5	118	var btn=document.getElementById(\"btn\");\
nixnax	142:54d1543e23e5	119	var ctr=0;\
nixnax	142:54d1543e23e5	120	function show(text){sts.textContent=text;}\
nixnax	142:54d1543e23e5	121	btn.onclick=function(){\
nixnax	142:54d1543e23e5	122	if(btn.textContent==\"Connect\"){\
nixnax	142:54d1543e23e5	123	x=new WebSocket(url);\
nixnax	142:54d1543e23e5	124	x.onopen=function(){\
nixnax	142:54d1543e23e5	125	show(\"Connected to : \"+url);\
nixnax	142:54d1543e23e5	126	btn.textContent=\"Send \\\"\"+ctr+\"\\\"\";\
nixnax	142:54d1543e23e5	127	};\
nixnax	142:54d1543e23e5	128	x.onclose=function(){show(\"closed\");};\
nixnax	142:54d1543e23e5	129	x.onmessage=function(msg){show(\"PPP-Blinky Sent: \\\"\"+msg.data+\"\\\"\");};\
nixnax	142:54d1543e23e5	130	} else {\
nixnax	142:54d1543e23e5	131	x.send(ctr);\
nixnax	142:54d1543e23e5	132	ctr=ctr+1;\
nixnax	142:54d1543e23e5	133	btn.textContent=\"Send \\\"\"+ctr+\"\\\"\";\
nixnax	142:54d1543e23e5	134	}\
nixnax	142:54d1543e23e5	135	};\
nixnax	142:54d1543e23e5	136	};\
nixnax	142:54d1543e23e5	137	</script>\
nixnax	142:54d1543e23e5	138	<body style=\"font-family: sans-serif; font-size:25px; color:#807070\">\
nixnax	142:54d1543e23e5	139	<h1>PPP-Blinky WebSocket Test</h1>\
nixnax	142:54d1543e23e5	140	<div id=\"sts\">Idle</div>\
nixnax	142:54d1543e23e5	141	<button id=\"btn\" style=\"font-size: 100%; margin-top: 55px; margin-bottom: 55px;\">Connect</button>\
nixnax	142:54d1543e23e5	142	<h4><a href=\"/\">PPP-Blinky home</a></h4>\
nixnax	142:54d1543e23e5	143	</body>\
nixnax	142:54d1543e23e5	144	</html>"; // size = 916 bytes + 1 null byte = 917 bytes
nixnax	142:54d1543e23e5	145
nixnax	142:54d1543e23e5	146	// The serial port on your mbed hardware. Your PC should be configured to view this port as a standard dial-up networking modem.
nixnax	142:54d1543e23e5	147	// On Windows the model type of the modem should be selected as "Communications cable between two computers"
nixnax	142:54d1543e23e5	148	// The modem baud rate should be set to 115200 baud
nixnax	142:54d1543e23e5	149	// See instructions at the top.
nixnax	142:54d1543e23e5	150	// On a typical mbed hardware platform this serial port is a USB virtual com port (VCP) and the USB serial driver is supplied by the board vendor.
nixnax	142:54d1543e23e5	151	BufferedSerial pc(USBTX, USBRX, 100); // usb virtual com port for mbed hardware
nixnax	142:54d1543e23e5	152
nixnax	142:54d1543e23e5	153	DigitalOut led1(LED1); // this led toggles when a packet is received
nixnax	142:54d1543e23e5	154
nixnax	142:54d1543e23e5	155	// the standard hdlc frame start/end character. It's the tilde character "~"
nixnax	142:54d1543e23e5	156	#define FRAME_7E (0x7e)
nixnax	142:54d1543e23e5	157
nixnax	142:54d1543e23e5	158	pppType ppp; // our global - definitely not thread safe
nixnax	142:54d1543e23e5	159
nixnax	142:54d1543e23e5	160	/// Initialize the ppp structure and clear the receive buffer
nixnax	142:54d1543e23e5	161	void pppInitStruct()
nixnax	142:54d1543e23e5	162	{
nixnax	142:54d1543e23e5	163	memset( ppp.rx.buf, 0, RXBUFLEN);
nixnax	142:54d1543e23e5	164	ppp.online=0;
nixnax	142:54d1543e23e5	165	ppp.rx.tail=0;
nixnax	142:54d1543e23e5	166	ppp.rx.rtail=0;
nixnax	142:54d1543e23e5	167	ppp.rx.head=0;
nixnax	142:54d1543e23e5	168	ppp.rx.buflevel=0;
nixnax	142:54d1543e23e5	169	ppp.pkt.len=0;
nixnax	154:18b2bd92f557	170	ppp.ipData.ident=10000; // easy to recognize in ip packet dumps
nixnax	142:54d1543e23e5	171	ppp.ledState=0;
nixnax	142:54d1543e23e5	172	ppp.hdlc.frameStartIndex=0;
nixnax	146:a45f49a2b29c	173	ppp.responseCounter=0;
nixnax	142:54d1543e23e5	174	ppp.firstFrame=1;
nixnax	175:b4e6f8a6fe00	175	ppp.ppp = (pppHeaderType *)ppp.pkt.buf; // pointer to ppp header
nixnax	175:b4e6f8a6fe00	176	ppp.ip = (ipHeaderType *)(ppp.pkt.buf+4); // pointer to IP header
nixnax	142:54d1543e23e5	177	}
nixnax	142:54d1543e23e5	178
nixnax	142:54d1543e23e5	179	/// Toggle the LED on every second PPP packet received
nixnax	142:54d1543e23e5	180	void led1Toggle()
nixnax	142:54d1543e23e5	181	{
nixnax	142:54d1543e23e5	182	led1 = (ppp.ledState >> 1) & 1; // use second bit, in other words toggle LED only every second packet
nixnax	143:c5019f856a56	183	ppp.ledState++;
nixnax	142:54d1543e23e5	184	}
nixnax	142:54d1543e23e5	185
nixnax	152:025c73b6c0a9	186	/// returns 1 after a connect message, 0 at startup or after a disconnect message
nixnax	150:3366bf3d294e	187	int connectedPpp()
nixnax	142:54d1543e23e5	188	{
nixnax	142:54d1543e23e5	189	return ppp.online;
nixnax	143:c5019f856a56	190	}
nixnax	142:54d1543e23e5	191
nixnax	143:c5019f856a56	192	/// Check for available characters from the PC and read them into our own circular serial receive buffer at ppp.rx.buf.
nixnax	143:c5019f856a56	193	/// Also, if we are offline and a 0x7e frame start character is seen, we go online immediately
nixnax	142:54d1543e23e5	194	void checkPc()
nixnax	142:54d1543e23e5	195	{
nixnax	142:54d1543e23e5	196	char ch;
nixnax	142:54d1543e23e5	197	if ( pc.readable() ) {
nixnax	142:54d1543e23e5	198	int hd = (ppp.rx.head+1)&(RXBUFLEN-1); // increment/wrap head index
nixnax	142:54d1543e23e5	199	if ( hd == ppp.rx.rtail ) {
nixnax	142:54d1543e23e5	200	debugPrintf("\nReceive buffer full\n");
nixnax	142:54d1543e23e5	201	return;
nixnax	142:54d1543e23e5	202	}
nixnax	142:54d1543e23e5	203	ch = pc.getc(); // read new character
nixnax	142:54d1543e23e5	204	ppp.rx.buf[ppp.rx.head] = ch; // insert in our receive buffer
nixnax	142:54d1543e23e5	205	if ( ppp.online == 0 ) {
nixnax	142:54d1543e23e5	206	if (ch == 0x7E) {
nixnax	142:54d1543e23e5	207	ppp.online = 1;
nixnax	142:54d1543e23e5	208	}
nixnax	142:54d1543e23e5	209	}
nixnax	142:54d1543e23e5	210	ppp.rx.head = hd; // update head pointer
nixnax	142:54d1543e23e5	211	ppp.rx.buflevel++;
nixnax	142:54d1543e23e5	212	}
nixnax	142:54d1543e23e5	213	}
nixnax	142:54d1543e23e5	214
nixnax	142:54d1543e23e5	215	/// print to debug port while checking for incoming characters
nixnax	142:54d1543e23e5	216	void putcWhileCheckingInput( char outByte )
nixnax	142:54d1543e23e5	217	{
nixnax	142:54d1543e23e5	218	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	219	checkPc();
nixnax	142:54d1543e23e5	220	debugPutc( outByte );
nixnax	142:54d1543e23e5	221	checkPc();
nixnax	142:54d1543e23e5	222	#endif
nixnax	142:54d1543e23e5	223	}
nixnax	142:54d1543e23e5	224
nixnax	142:54d1543e23e5	225	/// puts to debug port while checking the PPP input stream
nixnax	142:54d1543e23e5	226	void putsWhileCheckingInput( char * data )
nixnax	142:54d1543e23e5	227	{
nixnax	142:54d1543e23e5	228	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	229	char * nextChar = data;
nixnax	142:54d1543e23e5	230	while( *nextChar != 0 ) {
nixnax	142:54d1543e23e5	231	putcWhileCheckingInput( *nextChar ); // write one character to debug port while checking input
nixnax	142:54d1543e23e5	232	nextChar++;
nixnax	142:54d1543e23e5	233	}
nixnax	142:54d1543e23e5	234	#endif
nixnax	142:54d1543e23e5	235	}
nixnax	142:54d1543e23e5	236
nixnax	145:098b6ed2f7f2	237	/// Initialize the PPP FCS (frame check sequence) total
nixnax	145:098b6ed2f7f2	238	void fcsReset()
nixnax	142:54d1543e23e5	239	{
nixnax	145:098b6ed2f7f2	240	ppp.fcs=0xffff; // crc restart
nixnax	142:54d1543e23e5	241	}
nixnax	142:54d1543e23e5	242
nixnax	145:098b6ed2f7f2	243	/// update the cumulative PPP FCS (frame check sequence)
nixnax	145:098b6ed2f7f2	244	void fcsDo(int x)
nixnax	142:54d1543e23e5	245	{
nixnax	142:54d1543e23e5	246	for (int i=0; i<8; i++) {
nixnax	145:098b6ed2f7f2	247	ppp.fcs=((ppp.fcs&1)^(x&1))?(ppp.fcs>>1)^0x8408:ppp.fcs>>1; // crc calculator
nixnax	142:54d1543e23e5	248	x>>=1;
nixnax	142:54d1543e23e5	249	}
nixnax	142:54d1543e23e5	250	checkPc(); // handle input
nixnax	142:54d1543e23e5	251	}
nixnax	142:54d1543e23e5	252
nixnax	145:098b6ed2f7f2	253	/// calculate the PPP FCS (frame check sequence) on an entire block of memory
nixnax	145:098b6ed2f7f2	254	int fcsBuf(char * buf, int size) // crc on an entire block of memory
nixnax	142:54d1543e23e5	255	{
nixnax	145:098b6ed2f7f2	256	fcsReset();
nixnax	145:098b6ed2f7f2	257	for(int i=0; i<size; i++)fcsDo(*buf++);
nixnax	145:098b6ed2f7f2	258	return ppp.fcs;
nixnax	142:54d1543e23e5	259	}
nixnax	142:54d1543e23e5	260
nixnax	142:54d1543e23e5	261	/// Get one character from our received PPP buffer
nixnax	142:54d1543e23e5	262	int pc_getBuf()
nixnax	142:54d1543e23e5	263	{
nixnax	142:54d1543e23e5	264	int x = ppp.rx.buf[ ppp.rx.tail ];
nixnax	142:54d1543e23e5	265	ppp.rx.tail=(ppp.rx.tail+1)&(RXBUFLEN-1);
nixnax	142:54d1543e23e5	266	ppp.rx.buflevel--;
nixnax	142:54d1543e23e5	267	return x;
nixnax	142:54d1543e23e5	268	}
nixnax	142:54d1543e23e5	269
nixnax	142:54d1543e23e5	270	/// Dump a PPP frame to the debug serial port
nixnax	142:54d1543e23e5	271	/// Note - the hex output of dumpPPPFrame() can be imported into WireShark
nixnax	142:54d1543e23e5	272	/// Capture the frame's hex output in your terminal program and save as a text file
nixnax	164:c3de3d212c4b	273	/// In WireShark, use "Import Hex File". Import options are: Offset=None, Protocol=PPP.
nixnax	142:54d1543e23e5	274	void dumpPPPFrame()
nixnax	142:54d1543e23e5	275	{
nixnax	142:54d1543e23e5	276	char pbuf[30];
nixnax	142:54d1543e23e5	277	for(int i=0; i<ppp.pkt.len; i++) {
nixnax	142:54d1543e23e5	278	checkPc();
nixnax	142:54d1543e23e5	279	sprintf(pbuf, "%02x ", ppp.pkt.buf[i]);
nixnax	142:54d1543e23e5	280	checkPc();
nixnax	142:54d1543e23e5	281	putsWhileCheckingInput(pbuf);
nixnax	142:54d1543e23e5	282	}
nixnax	142:54d1543e23e5	283	checkPc();
nixnax	142:54d1543e23e5	284	sprintf(pbuf, " CRC=%04x Len=%d\n", ppp.pkt.crc, ppp.pkt.len);
nixnax	142:54d1543e23e5	285	checkPc();
nixnax	142:54d1543e23e5	286	putsWhileCheckingInput(pbuf);
nixnax	142:54d1543e23e5	287	}
nixnax	142:54d1543e23e5	288
nixnax	142:54d1543e23e5	289	/// Process a received PPP frame
nixnax	142:54d1543e23e5	290	void processPPPFrame(int start, int end)
nixnax	142:54d1543e23e5	291	{
nixnax	142:54d1543e23e5	292	led1Toggle(); // change led1 state on every frame we receive
nixnax	142:54d1543e23e5	293	if(start==end) {
nixnax	142:54d1543e23e5	294	return; // empty frame
nixnax	142:54d1543e23e5	295	}
nixnax	145:098b6ed2f7f2	296	fcsReset();
nixnax	142:54d1543e23e5	297	char * dest = ppp.pkt.buf;
nixnax	142:54d1543e23e5	298	ppp.pkt.len=0;
nixnax	142:54d1543e23e5	299	int unstuff=0;
nixnax	142:54d1543e23e5	300	int idx = start;
nixnax	142:54d1543e23e5	301	while(1) {
nixnax	142:54d1543e23e5	302	checkPc();
nixnax	142:54d1543e23e5	303	if (unstuff==0) {
nixnax	142:54d1543e23e5	304	if (ppp.rx.buf[idx]==0x7d) unstuff=1;
nixnax	142:54d1543e23e5	305	else {
nixnax	142:54d1543e23e5	306	*dest = ppp.rx.buf[idx];
nixnax	142:54d1543e23e5	307	ppp.pkt.len++;
nixnax	142:54d1543e23e5	308	dest++;
nixnax	145:098b6ed2f7f2	309	fcsDo(ppp.rx.buf[idx]);
nixnax	142:54d1543e23e5	310	}
nixnax	142:54d1543e23e5	311	} else { // unstuff characters prefixed with 0x7d
nixnax	142:54d1543e23e5	312	*dest = ppp.rx.buf[idx]^0x20;
nixnax	142:54d1543e23e5	313	ppp.pkt.len++;
nixnax	142:54d1543e23e5	314	dest++;
nixnax	145:098b6ed2f7f2	315	fcsDo(ppp.rx.buf[idx]^0x20);
nixnax	142:54d1543e23e5	316	unstuff=0;
nixnax	142:54d1543e23e5	317	}
nixnax	142:54d1543e23e5	318	idx = (idx+1) & (RXBUFLEN-1);
nixnax	142:54d1543e23e5	319	if (idx == end) break;
nixnax	142:54d1543e23e5	320	}
nixnax	145:098b6ed2f7f2	321	ppp.pkt.crc = ppp.fcs & 0xffff;
nixnax	142:54d1543e23e5	322	if(0) dumpPPPFrame(); // set to 1 to dump ALL ppp frames
nixnax	142:54d1543e23e5	323	if (ppp.pkt.crc == 0xf0b8) { // check for good CRC
nixnax	142:54d1543e23e5	324	determinePacketType();
nixnax	142:54d1543e23e5	325	} else {
nixnax	142:54d1543e23e5	326	#define REPORT_FCS_ERROR_YES
nixnax	142:54d1543e23e5	327	#ifdef REPORT_FCS_ERROR_YES
nixnax	142:54d1543e23e5	328	char pbuf[50]; // local print buffer
nixnax	142:54d1543e23e5	329	checkPc();
nixnax	142:54d1543e23e5	330	sprintf(pbuf, "\nPPP FCS(crc) Error CRC=%x Length = %d\n",ppp.pkt.crc,ppp.pkt.len); // print a debug line
nixnax	142:54d1543e23e5	331	checkPc();
nixnax	142:54d1543e23e5	332	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	333	if(0) dumpPPPFrame(); // set to 1 to dump frames with errors in them
nixnax	142:54d1543e23e5	334	#endif
nixnax	142:54d1543e23e5	335	}
nixnax	142:54d1543e23e5	336	}
nixnax	142:54d1543e23e5	337
nixnax	142:54d1543e23e5	338	/// output a character to the PPP port while checking for incoming characters
nixnax	142:54d1543e23e5	339	void pcPutcWhileCheckingInput(int ch)
nixnax	142:54d1543e23e5	340	{
nixnax	142:54d1543e23e5	341	checkPc(); // check input
nixnax	142:54d1543e23e5	342	pc.putc(ch);
nixnax	142:54d1543e23e5	343	checkPc();
nixnax	142:54d1543e23e5	344	}
nixnax	142:54d1543e23e5	345
nixnax	142:54d1543e23e5	346	/// do PPP HDLC-like handling of special (flag) characters
nixnax	143:c5019f856a56	347	void hdlcPut(int ch)
nixnax	142:54d1543e23e5	348	{
nixnax	142:54d1543e23e5	349	if ( (ch<0x20) \|\| (ch==0x7d) \|\| (ch==0x7e) ) {
nixnax	142:54d1543e23e5	350	pcPutcWhileCheckingInput(0x7d);
nixnax	142:54d1543e23e5	351	pcPutcWhileCheckingInput(ch^0x20); // these characters need special handling
nixnax	142:54d1543e23e5	352	} else {
nixnax	142:54d1543e23e5	353	pcPutcWhileCheckingInput(ch);
nixnax	142:54d1543e23e5	354	}
nixnax	142:54d1543e23e5	355	}
nixnax	142:54d1543e23e5	356
nixnax	142:54d1543e23e5	357	/// send a PPP frame in HDLC format
nixnax	144:01d98cf7738e	358	void sendPppFrame()
nixnax	143:c5019f856a56	359	{
nixnax	172:449dd7a28955	360	ppp.responseCounter++; // count the number of ppp frames we send
nixnax	145:098b6ed2f7f2	361	int crc = fcsBuf(ppp.pkt.buf, ppp.pkt.len-2); // update crc
nixnax	142:54d1543e23e5	362	ppp.pkt.buf[ ppp.pkt.len-2 ] = (~crc>>0); // fcs lo (crc)
nixnax	142:54d1543e23e5	363	ppp.pkt.buf[ ppp.pkt.len-1 ] = (~crc>>8); // fcs hi (crc)
nixnax	142:54d1543e23e5	364	pcPutcWhileCheckingInput(0x7e); // hdlc start-of-frame "flag"
nixnax	142:54d1543e23e5	365	for(int i=0; i<ppp.pkt.len; i++) {
nixnax	142:54d1543e23e5	366	wait_us(86); // wait one character time
nixnax	142:54d1543e23e5	367	checkPc();
nixnax	142:54d1543e23e5	368	hdlcPut( ppp.pkt.buf[i] ); // send a character
nixnax	142:54d1543e23e5	369	}
nixnax	142:54d1543e23e5	370	pcPutcWhileCheckingInput(0x7e); // hdlc end-of-frame "flag"
nixnax	142:54d1543e23e5	371	}
nixnax	142:54d1543e23e5	372
nixnax	143:c5019f856a56	373	/// convert a network ip address in the buffer to an integer (IP adresses are big-endian, i.e most significant byte first)
nixnax	143:c5019f856a56	374	int bufferToIP(char * buffer)
nixnax	143:c5019f856a56	375	{
nixnax	143:c5019f856a56	376	int result=0;
nixnax	143:c5019f856a56	377	for(int i=0; i<4; i++) result = (result<<8)\|(*buffer++ & 0xff);
nixnax	143:c5019f856a56	378	return result;
nixnax	143:c5019f856a56	379	}
nixnax	143:c5019f856a56	380
nixnax	142:54d1543e23e5	381	/// handle IPCP configuration requests
nixnax	142:54d1543e23e5	382	void ipcpConfigRequestHandler()
nixnax	142:54d1543e23e5	383	{
nixnax	142:54d1543e23e5	384	debugPrintf("Their IPCP Config Req, Our Ack\n");
nixnax	173:6774a0c851c4	385	if(ppp.ipcp->request[0]==3) {
nixnax	143:c5019f856a56	386	ppp.hostIP = bufferToIP(ppp.pkt.buf+10);
nixnax	173:6774a0c851c4	387	debugPrintf("Host IP = %d.%d.%d.%d (%08x)\n", ppp.ipcp->request[2],ppp.ipcp->request[3],ppp.ipcp->request[4],ppp.ipcp->request[5],ppp.hostIP);
nixnax	143:c5019f856a56	388	}
nixnax	143:c5019f856a56	389
nixnax	167:ff8a2d8beeb1	390	ppp.ipcp->code=2; // change code to ack
nixnax	144:01d98cf7738e	391	sendPppFrame(); // acknowledge everything they ask for - assume it's IP addresses
nixnax	142:54d1543e23e5	392
nixnax	142:54d1543e23e5	393	debugPrintf("Our IPCP Ask (no options)\n");
nixnax	167:ff8a2d8beeb1	394	ppp.ipcp->code=1; // change code to request
nixnax	167:ff8a2d8beeb1	395	ppp.ipcp->lengthR = __REV16( 4 ); // 4 is minimum length - no options in this request
nixnax	167:ff8a2d8beeb1	396	ppp.pkt.len=4+4+2; // no options in this request shortest ipcp packet possible (4 ppp + 4 ipcp + 2 crc)
nixnax	144:01d98cf7738e	397	sendPppFrame(); // send our request
nixnax	142:54d1543e23e5	398	}
nixnax	142:54d1543e23e5	399
nixnax	142:54d1543e23e5	400	/// handle IPCP acknowledge (do nothing)
nixnax	142:54d1543e23e5	401	void ipcpAckHandler()
nixnax	142:54d1543e23e5	402	{
nixnax	142:54d1543e23e5	403	debugPrintf("Their IPCP Grant\n");
nixnax	142:54d1543e23e5	404	}
nixnax	142:54d1543e23e5	405
nixnax	143:c5019f856a56	406	/// Handle IPCP NACK by sending our suggested IP address if there is an IP involved.
nixnax	143:c5019f856a56	407	/// This is how Linux responds to an IPCP request with no options - Windows assumes any IP address on the submnet is OK.
nixnax	142:54d1543e23e5	408	void ipcpNackHandler()
nixnax	142:54d1543e23e5	409	{
nixnax	146:a45f49a2b29c	410	debugPrintf("Their IPCP Nack\n");
nixnax	173:6774a0c851c4	411	if (ppp.ipcp->request[0]==3) { // check if the NACK contains an IP address parameter
nixnax	167:ff8a2d8beeb1	412	ppp.ipcp->code=1; // assume the NACK contains our "suggested" IP address
nixnax	144:01d98cf7738e	413	sendPppFrame(); // let's request this IP address as ours
nixnax	143:c5019f856a56	414	debugPrintf("Our IPCP ACK (received an IP)\n");
nixnax	146:a45f49a2b29c	415	} else { // if it's not an IP nack we ignore it
nixnax	146:a45f49a2b29c	416	debugPrintf("IPCP Nack Ignored\n");
nixnax	146:a45f49a2b29c	417	}
nixnax	142:54d1543e23e5	418	}
nixnax	142:54d1543e23e5	419
nixnax	142:54d1543e23e5	420	/// handle all other IPCP requests (by ignoring them)
nixnax	142:54d1543e23e5	421	void ipcpDefaultHandler()
nixnax	142:54d1543e23e5	422	{
nixnax	142:54d1543e23e5	423	debugPrintf("Their IPCP Other\n");
nixnax	142:54d1543e23e5	424	}
nixnax	142:54d1543e23e5	425
nixnax	142:54d1543e23e5	426	/// process an incoming IPCP packet
nixnax	142:54d1543e23e5	427	void IPCPframe()
nixnax	142:54d1543e23e5	428	{
nixnax	167:ff8a2d8beeb1	429	int action = ppp.ipcp->code; // packet type is here
nixnax	167:ff8a2d8beeb1	430	switch (action) {
nixnax	142:54d1543e23e5	431	case 1:
nixnax	142:54d1543e23e5	432	ipcpConfigRequestHandler();
nixnax	142:54d1543e23e5	433	break;
nixnax	142:54d1543e23e5	434	case 2:
nixnax	142:54d1543e23e5	435	ipcpAckHandler();
nixnax	142:54d1543e23e5	436	break;
nixnax	142:54d1543e23e5	437	case 3:
nixnax	142:54d1543e23e5	438	ipcpNackHandler();
nixnax	142:54d1543e23e5	439	break;
nixnax	142:54d1543e23e5	440	default:
nixnax	142:54d1543e23e5	441	ipcpDefaultHandler();
nixnax	142:54d1543e23e5	442	}
nixnax	142:54d1543e23e5	443	}
nixnax	142:54d1543e23e5	444
nixnax	142:54d1543e23e5	445	/// perform a 16-bit checksum. if the byte count is odd, stuff in an extra zero byte.
nixnax	161:d59f778bc8ab	446	unsigned int dataCheckSum(char * ptr, int len, int restart)
nixnax	142:54d1543e23e5	447	{
nixnax	159:4d1bf96a59cd	448	unsigned int i,hi,lo;
nixnax	142:54d1543e23e5	449	unsigned char placeHolder;
nixnax	161:d59f778bc8ab	450	if (restart) ppp.sum=0;
nixnax	142:54d1543e23e5	451	if (len&1) {
nixnax	142:54d1543e23e5	452	placeHolder = ptr[len];
nixnax	142:54d1543e23e5	453	ptr[len]=0; // if the byte count is odd, insert one extra zero byte is after the last real byte because we sum byte PAIRS
nixnax	142:54d1543e23e5	454	}
nixnax	142:54d1543e23e5	455	i=0;
nixnax	142:54d1543e23e5	456	while ( i<len ) {
nixnax	142:54d1543e23e5	457	checkPc();
nixnax	142:54d1543e23e5	458	hi = ptr[i++];
nixnax	142:54d1543e23e5	459	lo = ptr[i++];
nixnax	159:4d1bf96a59cd	460	ppp.sum = ppp.sum + ((hi<<8)\|lo);
nixnax	142:54d1543e23e5	461	}
nixnax	142:54d1543e23e5	462	if (len&1) {
nixnax	142:54d1543e23e5	463	ptr[len] = placeHolder; // restore the extra byte we made zero
nixnax	142:54d1543e23e5	464	}
nixnax	159:4d1bf96a59cd	465	ppp.sum = (ppp.sum & 0xffff) + (ppp.sum>>16);
nixnax	159:4d1bf96a59cd	466	ppp.sum = (ppp.sum & 0xffff) + (ppp.sum>>16); // sum one more time to catch any carry from the carry
nixnax	159:4d1bf96a59cd	467	return ~ppp.sum;
nixnax	142:54d1543e23e5	468	}
nixnax	142:54d1543e23e5	469
nixnax	142:54d1543e23e5	470	/// perform the checksum on an IP header
nixnax	146:a45f49a2b29c	471	void IpHeaderCheckSum()
nixnax	142:54d1543e23e5	472	{
nixnax	161:d59f778bc8ab	473	ppp.ip->checksumR=0; // zero the checsum in the IP header
nixnax	161:d59f778bc8ab	474	int len = 4 * ppp.ip->headerLength; // length of IP header in bytes
nixnax	161:d59f778bc8ab	475	unsigned int sum = dataCheckSum(ppp.ipStart,len,1);
nixnax	161:d59f778bc8ab	476	ppp.ip->checksumR = __REV16( sum ); // insert fresh checksum
nixnax	146:a45f49a2b29c	477	}
nixnax	146:a45f49a2b29c	478
nixnax	147:0f40005cbc5f	479	/// swap the IP source and destination addresses
nixnax	147:0f40005cbc5f	480	void swapIpAddresses()
nixnax	147:0f40005cbc5f	481	{
nixnax	162:594729c0e5c1	482	unsigned int tempHold;
nixnax	162:594729c0e5c1	483	tempHold = ppp.ip->srcAdrR; // tempHold <- source IP
nixnax	162:594729c0e5c1	484	ppp.ip->srcAdrR = ppp.ip->dstAdrR; // source <- dest
nixnax	162:594729c0e5c1	485	ppp.ip->dstAdrR = tempHold; // dest <- tempHold*/
nixnax	147:0f40005cbc5f	486	}
nixnax	147:0f40005cbc5f	487
nixnax	149:969d98f6fb88	488	/// swap the IP source and destination ports
nixnax	149:969d98f6fb88	489	void swapIpPorts()
nixnax	149:969d98f6fb88	490	{
nixnax	173:6774a0c851c4	491	int headerSizeIP = 4 * (ppp.ip->headerLength); // calculate size of IP header
nixnax	173:6774a0c851c4	492	char * ipSrcPort = ppp.ipStart + headerSizeIP + 0; // ip source port location
nixnax	173:6774a0c851c4	493	char * ipDstPort = ppp.ipStart + headerSizeIP + 2; // ip destin port location
nixnax	149:969d98f6fb88	494	char tempHold[2];
nixnax	149:969d98f6fb88	495	memcpy(tempHold, ipSrcPort,2); // tempHold <- source
nixnax	149:969d98f6fb88	496	memcpy(ipSrcPort,ipDstPort,2); // source <- dest
nixnax	149:969d98f6fb88	497	memcpy(ipDstPort,tempHold, 2); // dest <- tempHold
nixnax	149:969d98f6fb88	498	}
nixnax	149:969d98f6fb88	499
nixnax	170:3d3b2126181c	500	/// Build the "pseudo header" required for UDP and TCP, then calculate its checksum
nixnax	170:3d3b2126181c	501	void checkSumPseudoHeader( unsigned int packetLength )
nixnax	170:3d3b2126181c	502	{
nixnax	170:3d3b2126181c	503	// this header contains the most important parts of the IP header, i.e. source and destination address, protocol number and data length.
nixnax	170:3d3b2126181c	504	pseudoIpHeaderType pseudoHeader; // create pseudo header
nixnax	170:3d3b2126181c	505	pseudoHeader.srcAdrR = ppp.ip->srcAdrR; // copy in ip source address
nixnax	170:3d3b2126181c	506	pseudoHeader.dstAdrR = ppp.ip->dstAdrR; // copy in ip dest address
nixnax	170:3d3b2126181c	507	pseudoHeader.zero = 0; // zero byte
nixnax	170:3d3b2126181c	508	pseudoHeader.protocol = ppp.ip->protocol; // protocol number (udp or tcp)
nixnax	170:3d3b2126181c	509	pseudoHeader.lengthR = __REV16( packetLength ); // size of tcp or udp packet
nixnax	170:3d3b2126181c	510	dataCheckSum(pseudoHeader.start, 12, 1); // calculate this header's checksum
nixnax	170:3d3b2126181c	511	}
nixnax	170:3d3b2126181c	512
nixnax	171:46b36d4edd1d	513	/// initialize an IP packet to send
nixnax	171:46b36d4edd1d	514	void initIP (unsigned int srcIp, unsigned int dstIp, unsigned int srcPort, unsigned int dstPort, unsigned int protocol)
nixnax	171:46b36d4edd1d	515	{
nixnax	171:46b36d4edd1d	516	ppp.ppp->address = 0xff;
nixnax	171:46b36d4edd1d	517	ppp.ppp->control = 3;
nixnax	171:46b36d4edd1d	518	ppp.ppp->protocolR = __REV16( 0x0021 );
nixnax	171:46b36d4edd1d	519	ppp.ip->version = 4;
nixnax	171:46b36d4edd1d	520	ppp.ip->headerLength = 5; // 5 words = 20 bytes
nixnax	171:46b36d4edd1d	521	ppp.ip->identR = __REV16(ppp.ipData.ident++); // insert our ident
nixnax	171:46b36d4edd1d	522	ppp.ip->dontFragment=1;
nixnax	171:46b36d4edd1d	523	ppp.ip->ttl=128;
nixnax	171:46b36d4edd1d	524	ppp.ip->protocol = protocol; // udp
nixnax	171:46b36d4edd1d	525	ppp.ip->srcAdrR = __REV(srcIp);
nixnax	171:46b36d4edd1d	526	ppp.ip->dstAdrR = __REV(dstIp);
nixnax	171:46b36d4edd1d	527	ppp.udpStart = ppp.ipStart + 20; // calculate start of udp header
nixnax	171:46b36d4edd1d	528	ppp.udp->srcPortR = __REV16(srcPort); // source port
nixnax	171:46b36d4edd1d	529	ppp.udp->dstPortR = __REV16(dstPort); // dest port
nixnax	171:46b36d4edd1d	530	}
nixnax	171:46b36d4edd1d	531
nixnax	171:46b36d4edd1d	532
nixnax	171:46b36d4edd1d	533	/// Build a UDP packet from scratch
nixnax	171:46b36d4edd1d	534	void sendUdp(unsigned int srcIp, unsigned int dstIp, unsigned int srcPort, unsigned int dstPort, char * message,int msgLen)
nixnax	171:46b36d4edd1d	535	{
nixnax	171:46b36d4edd1d	536	struct {
nixnax	171:46b36d4edd1d	537	unsigned int ipAll; // length of entire ip packet
nixnax	171:46b36d4edd1d	538	unsigned int ipHeader; // length of ip header
nixnax	171:46b36d4edd1d	539	unsigned int udpAll; // length of entire udp packet
nixnax	171:46b36d4edd1d	540	unsigned int udpData; // length of udp data segment
nixnax	171:46b36d4edd1d	541	} len;
nixnax	171:46b36d4edd1d	542	len.ipHeader = 20; // ip header length
nixnax	171:46b36d4edd1d	543	len.udpData = msgLen; // udp data size
nixnax	171:46b36d4edd1d	544	len.udpAll = len.udpData+8; // update local udp packet length
nixnax	171:46b36d4edd1d	545	len.ipAll = len.ipHeader + len.udpAll; // update IP Length
nixnax	171:46b36d4edd1d	546	initIP(srcIp, dstIp, srcPort, dstPort, 17); // init a UDP packet
nixnax	171:46b36d4edd1d	547	ppp.ip->lengthR = __REV16(len.ipAll); // update IP length in buffer
nixnax	171:46b36d4edd1d	548	ppp.udpStart = ppp.ipStart + len.ipHeader; // calculate start of udp header
nixnax	171:46b36d4edd1d	549	memcpy( ppp.udp->data, message, len.udpData ); // copy the message to the buffer
nixnax	171:46b36d4edd1d	550	ppp.udp->lengthR = __REV16(len.udpAll); // update UDP length in buffer
nixnax	171:46b36d4edd1d	551	ppp.pkt.len = len.ipAll+2+4; // update ppp packet length
nixnax	171:46b36d4edd1d	552	IpHeaderCheckSum(); // refresh IP header checksum
nixnax	171:46b36d4edd1d	553	checkSumPseudoHeader( len.udpAll ); // get the UDP pseudo-header checksum
nixnax	171:46b36d4edd1d	554	ppp.udp->checksumR = 0; // before TCP checksum calculations the checksum bytes must be set cleared
nixnax	171:46b36d4edd1d	555	unsigned int pseudoHeaderSum=dataCheckSum(ppp.udpStart,len.udpAll, 0); // continue the TCP checksum on the whole TCP packet
nixnax	171:46b36d4edd1d	556	ppp.udp->checksumR = __REV16( pseudoHeaderSum); // tcp checksum done, store it in the TCP header
nixnax	171:46b36d4edd1d	557	sendPppFrame(); // send the UDP message back
nixnax	171:46b36d4edd1d	558	}
nixnax	171:46b36d4edd1d	559
nixnax	146:a45f49a2b29c	560	/// Process an incoming UDP packet.
nixnax	146:a45f49a2b29c	561	/// If the packet starts with the string "echo " or "test" we echo back a special packet
nixnax	146:a45f49a2b29c	562	void UDPpacket()
nixnax	146:a45f49a2b29c	563	{
nixnax	163:d1b4328e9f08	564	struct {
nixnax	163:d1b4328e9f08	565	unsigned int all; // length of entire ip packet
nixnax	163:d1b4328e9f08	566	unsigned int header; // length of ip header
nixnax	163:d1b4328e9f08	567	} ipLength;
nixnax	163:d1b4328e9f08	568
nixnax	163:d1b4328e9f08	569	struct {
nixnax	165:c47826d07e0d	570	unsigned int all; // length of entire udp packet
nixnax	163:d1b4328e9f08	571	unsigned int data; // length of udp data segment
nixnax	163:d1b4328e9f08	572	} udpLength;
nixnax	163:d1b4328e9f08	573
nixnax	163:d1b4328e9f08	574	ipLength.header = 4 * ppp.ip->headerLength; // length of ip header
nixnax	163:d1b4328e9f08	575	ppp.udpStart = ppp.ipStart + ipLength.header; // calculate start of udp header
nixnax	171:46b36d4edd1d	576	udpLength.all = __REV16( ppp.udp->lengthR ); // size of udp packet
nixnax	163:d1b4328e9f08	577	udpLength.data = udpLength.all - 8; // size of udp data
nixnax	147:0f40005cbc5f	578
nixnax	146:a45f49a2b29c	579	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	171:46b36d4edd1d	580	char * srcIP = ppp.ip->srcAdrPtr; // IP source
nixnax	171:46b36d4edd1d	581	char * dstIP = ppp.ip->dstAdrPtr; //IP destination
nixnax	163:d1b4328e9f08	582
nixnax	171:46b36d4edd1d	583	unsigned int udpSrcPort = __REV16( ppp.udp->srcPortR ); // integer of UDP source port
nixnax	171:46b36d4edd1d	584	unsigned int udpDstPort = __REV16( ppp.udp->dstPortR ); // integer of UDP dest port
nixnax	163:d1b4328e9f08	585
nixnax	163:d1b4328e9f08	586	if(v0) {
nixnax	163:d1b4328e9f08	587	debugPrintf("UDP %d.%d.%d.%d:%d ", srcIP[0],srcIP[1],srcIP[2],srcIP[3],udpSrcPort);
nixnax	163:d1b4328e9f08	588	debugPrintf("%d.%d.%d.%d:%d ", dstIP[0],dstIP[1],dstIP[2],dstIP[3],udpDstPort);
nixnax	163:d1b4328e9f08	589	debugPrintf("Len %03d", udpLength);
nixnax	163:d1b4328e9f08	590	}
nixnax	146:a45f49a2b29c	591	if (v1) {
nixnax	163:d1b4328e9f08	592	int printSize = udpLength.data;
nixnax	146:a45f49a2b29c	593	if (printSize > 20) printSize = 20; // print only first 20 characters
nixnax	146:a45f49a2b29c	594	for (int i=0; i<printSize; i++) {
nixnax	163:d1b4328e9f08	595	char ch = ppp.udp->data[i];
nixnax	146:a45f49a2b29c	596	if (ch>31 && ch<127) {
nixnax	146:a45f49a2b29c	597	debugPrintf("%c", ch);
nixnax	146:a45f49a2b29c	598	} else {
nixnax	146:a45f49a2b29c	599	debugPrintf("_");
nixnax	146:a45f49a2b29c	600	}
nixnax	146:a45f49a2b29c	601	}
nixnax	146:a45f49a2b29c	602	}
nixnax	146:a45f49a2b29c	603	if (v0) debugPrintf("\n");
nixnax	146:a45f49a2b29c	604	#endif
nixnax	163:d1b4328e9f08	605	int echoFound = !strncmp(ppp.udp->data,"echo ",5); // true if UDP message starts with "echo "
nixnax	163:d1b4328e9f08	606	int testFound = !strncmp(ppp.udp->data,"test" ,4); // true if UDP message starts with "test"
nixnax	146:a45f49a2b29c	607	if ( (echoFound) \|\| (testFound)) { // if the UDP message starts with "echo " or "test" we answer back
nixnax	146:a45f49a2b29c	608	if (echoFound) {
nixnax	171:46b36d4edd1d	609	swapIpAddresses(); // swap IP source and destination
nixnax	171:46b36d4edd1d	610	swapIpPorts(); // swap IP source and destination ports
nixnax	163:d1b4328e9f08	611	memcpy(ppp.udp->data,"Got{",4); // in the UDP data modify "echo" to "Got:"
nixnax	170:3d3b2126181c	612	int n=0;
nixnax	170:3d3b2126181c	613	n=n+sprintf(n+ppp.udp->data+udpLength.data, "} UDP Server: PPP-Blinky\n"); // an appendix
nixnax	168:c77eb908042a	614	udpLength.data = udpLength.data + n; // update udp data size with the size of the appendix
nixnax	171:46b36d4edd1d	615	// we may have changed data length, update all the lengths
nixnax	171:46b36d4edd1d	616	udpLength.all = udpLength.data+8; // update local udp packet length
nixnax	171:46b36d4edd1d	617	ipLength.all = ipLength.header + udpLength.all; // update IP Length
nixnax	171:46b36d4edd1d	618	ppp.ip->lengthR = __REV16(ipLength.all); // update IP length in buffer
nixnax	171:46b36d4edd1d	619	ppp.udp->lengthR = __REV16(udpLength.all); // update UDP length in buffer
nixnax	171:46b36d4edd1d	620	ppp.pkt.len = ipLength.all+2+4; // update ppp packet length
nixnax	171:46b36d4edd1d	621	IpHeaderCheckSum(); // refresh IP header checksum
nixnax	171:46b36d4edd1d	622	checkSumPseudoHeader( udpLength.all ); // get the UDP pseudo-header checksum
nixnax	171:46b36d4edd1d	623	ppp.udp->checksumR = 0; // before TCP checksum calculations the checksum bytes must be set cleared
nixnax	171:46b36d4edd1d	624	unsigned int pseudoHeaderSum=dataCheckSum(ppp.udpStart,udpLength.all, 0); // continue the TCP checksum on the whole TCP packet
nixnax	171:46b36d4edd1d	625	ppp.udp->checksumR = __REV16( pseudoHeaderSum); // tcp checksum done, store it in the TCP header
nixnax	171:46b36d4edd1d	626	sendPppFrame(); // send the UDP message back
nixnax	171:46b36d4edd1d	627	} else if ( testFound ) {
nixnax	171:46b36d4edd1d	628	unsigned int sI = __REV( ppp.ip->srcAdrR );
nixnax	171:46b36d4edd1d	629	unsigned int dI = __REV( ppp.ip->dstAdrR );
nixnax	171:46b36d4edd1d	630	unsigned int sp = __REV16( ppp.udp->srcPortR );
nixnax	171:46b36d4edd1d	631	unsigned int dp = __REV16( ppp.udp->dstPortR );
nixnax	172:449dd7a28955	632	int n=sprintf(ppp.pkt.buf+200,"Response Count %d\n", ppp.responseCounter);
nixnax	171:46b36d4edd1d	633	sendUdp(dI,sI,dp,sp,ppp.pkt.buf+200,n); // build a udp packet from the ground up
nixnax	146:a45f49a2b29c	634	}
nixnax	146:a45f49a2b29c	635	}
nixnax	142:54d1543e23e5	636	}
nixnax	142:54d1543e23e5	637
nixnax	142:54d1543e23e5	638	/// handle a PING ICMP (internet control message protocol) packet
nixnax	142:54d1543e23e5	639	void ICMPpacket() // internet control message protocol
nixnax	142:54d1543e23e5	640	{
nixnax	165:c47826d07e0d	641	struct {
nixnax	165:c47826d07e0d	642	unsigned int all; // length of entire ip packet
nixnax	165:c47826d07e0d	643	unsigned int header; // length of ip header
nixnax	165:c47826d07e0d	644	} ipLength;
nixnax	165:c47826d07e0d	645	struct {
nixnax	165:c47826d07e0d	646	unsigned int all; // length of entire udp packet
nixnax	165:c47826d07e0d	647	unsigned int data; // length of udp data segment
nixnax	165:c47826d07e0d	648	} icmpLength;
nixnax	165:c47826d07e0d	649	ipLength.all = __REV16( ppp.ip->lengthR ); // length of ip packet
nixnax	165:c47826d07e0d	650	ipLength.header = 4 * ppp.ip->headerLength; // length of ip header
nixnax	165:c47826d07e0d	651	ppp.icmpStart = ppp.ipStart + ipLength.header; // calculate start of udp header
nixnax	165:c47826d07e0d	652	icmpLength.all = ipLength.all - ipLength.header; // length of icmp packet
nixnax	165:c47826d07e0d	653	icmpLength.data = icmpLength.all - 8; // length of icmp data
nixnax	142:54d1543e23e5	654	#define ICMP_TYPE_PING_REQUEST 8
nixnax	165:c47826d07e0d	655	if ( ppp.icmp->type == ICMP_TYPE_PING_REQUEST ) {
nixnax	165:c47826d07e0d	656	ppp.ip->ttl--; // decrement time to live (so we have to update header checksum)
nixnax	147:0f40005cbc5f	657	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	167:ff8a2d8beeb1	658	char * srcAdr = ppp.ip->srcAdrPtr;
nixnax	167:ff8a2d8beeb1	659	char * dstAdr = ppp.ip->dstAdrPtr;
nixnax	165:c47826d07e0d	660	int icmpIdent = __REV16( ppp.ip->identR ); // byte reversed - big endian
nixnax	165:c47826d07e0d	661	int icmpSequence = __REV16( ppp.icmp->sequenceR ); // byte reversed - big endian
nixnax	142:54d1543e23e5	662	if(1) {
nixnax	142:54d1543e23e5	663	char pbuf[50];
nixnax	142:54d1543e23e5	664	checkPc();
nixnax	142:54d1543e23e5	665	sprintf(pbuf, "ICMP PING %d.%d.%d.%d %d.%d.%d.%d ", srcAdr[0],srcAdr[1],srcAdr[2],srcAdr[3],dstAdr[0],dstAdr[1],dstAdr[2],dstAdr[3]);
nixnax	142:54d1543e23e5	666	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	667	checkPc();
nixnax	142:54d1543e23e5	668	sprintf(pbuf, "Ident %04x Sequence %04d \n",icmpIdent,icmpSequence);
nixnax	142:54d1543e23e5	669	checkPc();
nixnax	142:54d1543e23e5	670	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	671	}
nixnax	142:54d1543e23e5	672	#endif
nixnax	147:0f40005cbc5f	673	swapIpAddresses(); // swap the IP source and destination addresses
nixnax	147:0f40005cbc5f	674	IpHeaderCheckSum(); // new ip header checksum (required because we changed TTL)
nixnax	142:54d1543e23e5	675	#define ICMP_TYPE_ECHO_REPLY 0
nixnax	165:c47826d07e0d	676	ppp.icmp->type = ICMP_TYPE_ECHO_REPLY; // icmp echo reply
nixnax	165:c47826d07e0d	677	ppp.icmp->checkSumR = 0; // zero the checksum for recalculation
nixnax	165:c47826d07e0d	678	unsigned int sum = dataCheckSum(ppp.icmpStart, icmpLength.all, 1); // icmp checksum
nixnax	165:c47826d07e0d	679	ppp.icmp->checkSumR = __REV16( sum ); // save big-endian icmp checksum
nixnax	142:54d1543e23e5	680
nixnax	165:c47826d07e0d	681	int printSize = icmpLength.data; // exclude size of icmp header
nixnax	142:54d1543e23e5	682	if (printSize > 10) printSize = 10; // print up to 20 characters
nixnax	142:54d1543e23e5	683	if (0) {
nixnax	142:54d1543e23e5	684	for (int i=0; i<printSize; i++) {
nixnax	165:c47826d07e0d	685	char ch = ppp.icmp->data[i];
nixnax	142:54d1543e23e5	686	if (ch>31 && ch<127) {
nixnax	142:54d1543e23e5	687	putcWhileCheckingInput(ch);
nixnax	142:54d1543e23e5	688	} else {
nixnax	142:54d1543e23e5	689	putcWhileCheckingInput('_');
nixnax	142:54d1543e23e5	690	}
nixnax	142:54d1543e23e5	691	}
nixnax	142:54d1543e23e5	692	putcWhileCheckingInput('\n');
nixnax	142:54d1543e23e5	693	}
nixnax	144:01d98cf7738e	694	sendPppFrame(); // reply to the ping
nixnax	142:54d1543e23e5	695	} else {
nixnax	142:54d1543e23e5	696	if (v0) {
nixnax	165:c47826d07e0d	697	debugPrintf("ICMP type=%x \n", ppp.icmp->type);
nixnax	142:54d1543e23e5	698	}
nixnax	142:54d1543e23e5	699	}
nixnax	142:54d1543e23e5	700	}
nixnax	142:54d1543e23e5	701
nixnax	142:54d1543e23e5	702	/// handle an IGMP (internet group managment protocol) packet (by ignoring it)
nixnax	142:54d1543e23e5	703	void IGMPpacket()
nixnax	142:54d1543e23e5	704	{
nixnax	142:54d1543e23e5	705	if (v0) debugPrintf("IGMP type=%d \n", ppp.pkt.buf[28]);
nixnax	142:54d1543e23e5	706	}
nixnax	142:54d1543e23e5	707
nixnax	142:54d1543e23e5	708	/// dump the header of an IP pakcet on the (optional) debug serial port
nixnax	142:54d1543e23e5	709	void dumpHeaderIP (int outGoing)
nixnax	142:54d1543e23e5	710	{
nixnax	142:54d1543e23e5	711	#if defined(IP_HEADER_DUMP_YES) && defined(SERIAL_PORT_MONITOR_YES)
nixnax	142:54d1543e23e5	712	checkPc(); // we are expecting the first character of the next packet
nixnax	155:9c6a1d249e26	713	int IPv4Id = __REV16(ppp.ip->identR);
nixnax	152:025c73b6c0a9	714	char pbuf[80]; // local print buffer
nixnax	142:54d1543e23e5	715	int n=0;
nixnax	142:54d1543e23e5	716	n=n+sprintf(pbuf+n, outGoing ? "\x1b[34m" : "\x1b[30m" ); // VT100 color code, print black for incoming, blue for outgoing headers
nixnax	142:54d1543e23e5	717	n=n+sprintf(pbuf+n, "%05d ",IPv4Id); // IPv4Id is a good way to correlate our dumps with net monitor or wireshark traces
nixnax	142:54d1543e23e5	718	#define DUMP_FULL_IP_ADDRESS_YES
nixnax	142:54d1543e23e5	719	#ifdef DUMP_FULL_IP_ADDRESS_YES
nixnax	167:ff8a2d8beeb1	720	char * srcAdr = ppp.ip->srcAdrPtr;
nixnax	167:ff8a2d8beeb1	721	char * dstAdr = ppp.ip->dstAdrPtr;
nixnax	142:54d1543e23e5	722	n=n+sprintf(pbuf+n, " %d.%d.%d.%d %d.%d.%d.%d ",srcAdr[0],srcAdr[1],srcAdr[2],srcAdr[3], dstAdr[0],dstAdr[1],dstAdr[2],dstAdr[3]); // full ip addresses
nixnax	142:54d1543e23e5	723	#endif
nixnax	142:54d1543e23e5	724	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	725	#ifndef TCP_HEADER_DUMP_YES
nixnax	160:bd701ad564cb	726	putsWhileCheckingInput('\x1b[30m\n'); // if there's no TCP header dump we terminate the line with \n and VT100 code for black
nixnax	142:54d1543e23e5	727	#endif
nixnax	142:54d1543e23e5	728	#endif
nixnax	142:54d1543e23e5	729	}
nixnax	142:54d1543e23e5	730
nixnax	142:54d1543e23e5	731	/// dump a TCP header on the optional debug serial port
nixnax	142:54d1543e23e5	732	void dumpHeaderTCP(int outGoing)
nixnax	142:54d1543e23e5	733	{
nixnax	142:54d1543e23e5	734	#if defined(TCP_HEADER_DUMP_YES) && defined(SERIAL_PORT_MONITOR_YES)
nixnax	155:9c6a1d249e26	735	char flagString[9]; // text string presenting the 8 most important TCP flags
nixnax	142:54d1543e23e5	736	#define PRINT_ALL_TCP_FLAGS_YES
nixnax	142:54d1543e23e5	737	#ifdef PRINT_ALL_TCP_FLAGS_YES
nixnax	155:9c6a1d249e26	738	memset(flagString,'.', 8); // fill string with "........"
nixnax	156:163c23249731	739	if (ppp.tcp->flag.fin) flagString[7]='F';
nixnax	156:163c23249731	740	if (ppp.tcp->flag.syn) flagString[6]='S';
nixnax	156:163c23249731	741	if (ppp.tcp->flag.rst) flagString[5]='R';
nixnax	156:163c23249731	742	if (ppp.tcp->flag.psh) flagString[4]='P';
nixnax	156:163c23249731	743	if (ppp.tcp->flag.ack) flagString[3]='A';
nixnax	156:163c23249731	744	if (ppp.tcp->flag.urg) flagString[2]='U';
nixnax	156:163c23249731	745	if (ppp.tcp->flag.ece) flagString[1]='E';
nixnax	156:163c23249731	746	if (ppp.tcp->flag.cwr) flagString[0]='C';
nixnax	155:9c6a1d249e26	747	flagString[8]=0; // null terminate string
nixnax	142:54d1543e23e5	748	#else
nixnax	156:163c23249731	749	if (ppp.tcp->flag.ack) flagString[0]='A'; // choose only the most important flag to print
nixnax	156:163c23249731	750	if (ppp.tcp->flag.syn) flagString[0]='S';
nixnax	156:163c23249731	751	if (ppp.tcp->flag.fin) flagString[0]='F';
nixnax	156:163c23249731	752	if (ppp.tcp->flag.psh) flagString[0]='P';
nixnax	156:163c23249731	753	if (ppp.tcp->flag.rst) flagString[0]='R';
nixnax	155:9c6a1d249e26	754	flagString[1]=0; // null terminate string
nixnax	142:54d1543e23e5	755	#endif
nixnax	155:9c6a1d249e26	756	putsWhileCheckingInput( flagString );
nixnax	142:54d1543e23e5	757	#define EVERY_PACKET_ON_A_NEW_LINE_YES
nixnax	142:54d1543e23e5	758	#ifdef EVERY_PACKET_ON_A_NEW_LINE_YES
nixnax	142:54d1543e23e5	759	putsWhileCheckingInput("\x1b[30m\n"); // write a black color and newline after every packet
nixnax	160:bd701ad564cb	760	#else
nixnax	160:bd701ad564cb	761	putsWhileCheckingInput("\x1b[30m"); // write a black color after every packet
nixnax	142:54d1543e23e5	762	#endif
nixnax	156:163c23249731	763	if( outGoing && ppp.tcp->flag.fin ) { // ACK/FIN - if this is an outgoing FIN it's the end of a tcp conversation
nixnax	160:bd701ad564cb	764	putcWhileCheckingInput('\n'); // insert an extra new line to mark the end (except for final ack) of an HTTP conversation
nixnax	142:54d1543e23e5	765	}
nixnax	142:54d1543e23e5	766	#endif
nixnax	142:54d1543e23e5	767	}
nixnax	142:54d1543e23e5	768
nixnax	143:c5019f856a56	769	/// Encode a buffer in base-64
nixnax	142:54d1543e23e5	770	void enc64(char * in, char * out, int len)
nixnax	142:54d1543e23e5	771	{
nixnax	142:54d1543e23e5	772	const static char lut [] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
nixnax	142:54d1543e23e5	773	int i,j,a,b,c;
nixnax	142:54d1543e23e5	774	i=0;
nixnax	142:54d1543e23e5	775	j=0;
nixnax	142:54d1543e23e5	776	while(1) {
nixnax	142:54d1543e23e5	777	if (i<len) {
nixnax	142:54d1543e23e5	778	a = in[i++];
nixnax	142:54d1543e23e5	779	out[j++] = lut[ ( (a >> 2) & 0x3f) ];
nixnax	142:54d1543e23e5	780	} else break;
nixnax	142:54d1543e23e5	781	if (i<len) {
nixnax	142:54d1543e23e5	782	b = in[i++];
nixnax	142:54d1543e23e5	783	out[j++] = lut[ ( (a << 4) & 0x30) \| ( (b >> 4) & 0x0f) ];
nixnax	142:54d1543e23e5	784	out[j++] = lut[ ( (b << 2) & 0x3c) ];
nixnax	142:54d1543e23e5	785	} else out[j++] = '=';
nixnax	142:54d1543e23e5	786	if (i<len) {
nixnax	142:54d1543e23e5	787	c = in[i++];
nixnax	142:54d1543e23e5	788	j--;
nixnax	142:54d1543e23e5	789	out[j++] = lut[ ( (b << 2) & 0x3c) \| ( (c >> 6) & 0x03) ];
nixnax	142:54d1543e23e5	790	out[j++] = lut[ ( (c >> 0) & 0x3f) ];
nixnax	142:54d1543e23e5	791	} else out[j++] = '=';
nixnax	142:54d1543e23e5	792	}
nixnax	142:54d1543e23e5	793	out[j]=0;
nixnax	142:54d1543e23e5	794	}
nixnax	142:54d1543e23e5	795
nixnax	160:bd701ad564cb	796	/// Handle a request for an http websocket.
nixnax	160:bd701ad564cb	797	/// We end up here if we enter the following javascript in a web browser console: x = new WebSocket("ws://172.10.10.2");
nixnax	142:54d1543e23e5	798	int webSocketHandler(char * dataStart)
nixnax	142:54d1543e23e5	799	{
nixnax	142:54d1543e23e5	800	int n=0; // byte counter
nixnax	142:54d1543e23e5	801	char * key = strstr(dataStart, "Sec-WebSocket-Key: "); // search for the key in the payload
nixnax	142:54d1543e23e5	802	if (key != NULL) {
nixnax	142:54d1543e23e5	803	if (v0) putsWhileCheckingInput("WebSocket Request\n");
nixnax	142:54d1543e23e5	804	char challenge [70];
nixnax	142:54d1543e23e5	805	strncpy(challenge,key+19,70); // a local buffer
nixnax	142:54d1543e23e5	806	*strchr(challenge,'\r')=0; // insert null so we can use sprintf
nixnax	142:54d1543e23e5	807	strncat(challenge,"258EAFA5-E914-47DA-95CA-C5AB0DC85B11",70); // append websocket gui code
nixnax	142:54d1543e23e5	808	char shaOutput [20]; // sha1 output
nixnax	142:54d1543e23e5	809	sha1( shaOutput, challenge, strlen(challenge));
nixnax	142:54d1543e23e5	810	char encOut[50];
nixnax	142:54d1543e23e5	811	enc64( shaOutput, encOut, 20);
nixnax	142:54d1543e23e5	812	char * versionstring = strstr(dataStart, "Sec-WebSocket-Version:");
nixnax	142:54d1543e23e5	813	char * version = challenge;
nixnax	142:54d1543e23e5	814	strncpy(version, versionstring,70); // copy version string
nixnax	142:54d1543e23e5	815	*strchr(version,'\r')=0; // null terminate so we can sprintf it
nixnax	142:54d1543e23e5	816	memset(dataStart,0,500); // blank out old data befor send the websocket response header
nixnax	142:54d1543e23e5	817	n=n+sprintf(dataStart+n, "HTTP/1.1 101 Switching Protocols\r\n");
nixnax	142:54d1543e23e5	818	n=n+sprintf(dataStart+n, "Upgrade: websocket\r\n");
nixnax	142:54d1543e23e5	819	n=n+sprintf(dataStart+n, "Connection: Upgrade\r\n");
nixnax	142:54d1543e23e5	820	n=n+sprintf(dataStart+n, "Sec-WebSocket-Accept: %s\r\n",encOut);
nixnax	142:54d1543e23e5	821	n=n+sprintf(dataStart+n, "%s\r\n",version);
nixnax	142:54d1543e23e5	822	n=n+sprintf(dataStart+n, "mbed-Code: PPP-Blinky\r\n");
nixnax	142:54d1543e23e5	823	n=n+sprintf(dataStart+n, "\r\n"); // websocket response header ending
nixnax	142:54d1543e23e5	824	}
nixnax	142:54d1543e23e5	825	return n; // this response should satisfy a web browser's websocket protocol request
nixnax	142:54d1543e23e5	826	}
nixnax	142:54d1543e23e5	827
nixnax	142:54d1543e23e5	828	#define TCP_FLAG_ACK (1<<4)
nixnax	142:54d1543e23e5	829	#define TCP_FLAG_SYN (1<<1)
nixnax	142:54d1543e23e5	830	#define TCP_FLAG_PSH (1<<3)
nixnax	142:54d1543e23e5	831	#define TCP_FLAG_RST (1<<2)
nixnax	142:54d1543e23e5	832	#define TCP_FLAG_FIN (1<<0)
nixnax	142:54d1543e23e5	833
nixnax	142:54d1543e23e5	834	/// respond to an HTTP request
nixnax	142:54d1543e23e5	835	int httpResponse(char * dataStart)
nixnax	142:54d1543e23e5	836	{
nixnax	142:54d1543e23e5	837	int n=0; // number of bytes we have printed so far
nixnax	142:54d1543e23e5	838	n = webSocketHandler( dataStart ); // test for and handle WebSocket upgrade requests
nixnax	160:bd701ad564cb	839	if (n>0) return n; // if n>0 we already have a response, so return
nixnax	142:54d1543e23e5	840
nixnax	142:54d1543e23e5	841	int nHeader; // byte size of HTTP header
nixnax	142:54d1543e23e5	842	int contentLengthStart; // index where HTML starts
nixnax	142:54d1543e23e5	843	int httpGet5,httpGet6,httpGetx, httpGetRoot; // temporary storage of strncmp results
nixnax	142:54d1543e23e5	844
nixnax	142:54d1543e23e5	845	httpGetRoot = strncmp(dataStart, "GET / HTTP/1.", 13); // found a GET to the root directory
nixnax	142:54d1543e23e5	846	httpGetx = strncmp(dataStart, "GET /x", 6); // found a GET to /x which we will treat special (anything starting with /x, e.g. /x, /xyz, /xABC?pqr=123
nixnax	142:54d1543e23e5	847	httpGet5 = dataStart[5]; // the first character in the path name, we use it for special functions later on
nixnax	142:54d1543e23e5	848	httpGet6 = dataStart[6]; // the second character in the path name, we use it for special functions later on
nixnax	142:54d1543e23e5	849	// for example, you could try this using netcat (nc): echo "GET /x" \| nc 172.10.10.2
nixnax	142:54d1543e23e5	850	if( (httpGetRoot==0) \|\| (httpGetx==0) ) {
nixnax	142:54d1543e23e5	851	n=n+sprintf(n+dataStart,"HTTP/1.1 200 OK\r\nServer: mbed-PPP-Blinky-v1\r\n"); // 200 OK header
nixnax	142:54d1543e23e5	852	} else {
nixnax	142:54d1543e23e5	853	n=n+sprintf(n+dataStart,"HTTP/1.1 404 Not Found\r\nServer: mbed-PPP-Blinky\r\n"); // 404 header
nixnax	142:54d1543e23e5	854	}
nixnax	142:54d1543e23e5	855	n=n+sprintf(n+dataStart,"Content-Length: "); // http header
nixnax	142:54d1543e23e5	856	contentLengthStart = n; // remember where Content-Length is in buffer
nixnax	142:54d1543e23e5	857	n=n+sprintf(n+dataStart,"?????\r\n"); // leave five spaces for content length - will be updated later
nixnax	142:54d1543e23e5	858	n=n+sprintf(n+dataStart,"Connection: close\r\n"); // close connection immediately
nixnax	142:54d1543e23e5	859	n=n+sprintf(n+dataStart,"Content-Type: text/html; charset=us-ascii\r\n\r\n"); // http header must end with empty line (\r\n)
nixnax	142:54d1543e23e5	860	nHeader=n; // size of HTTP header
nixnax	142:54d1543e23e5	861	if( httpGetRoot == 0 ) {
nixnax	142:54d1543e23e5	862	// this is where we insert our web page into the buffer
nixnax	142:54d1543e23e5	863	memcpy(n+dataStart,rootWebPage,sizeof(rootWebPage));
nixnax	142:54d1543e23e5	864	n = n + sizeof(rootWebPage)-1; // one less than sizeof because we don't count the null byte at the end
nixnax	142:54d1543e23e5	865	} else if ( (httpGet5 == 'w') && (httpGet6 == 's') ) { // "ws" is a special page for websocket demo
nixnax	142:54d1543e23e5	866	memcpy(n+dataStart,webSocketPage,sizeof(webSocketPage));
nixnax	142:54d1543e23e5	867	n = n + sizeof(webSocketPage)-1; // one less than size
nixnax	142:54d1543e23e5	868	} else {
nixnax	142:54d1543e23e5	869	if (httpGetx == 0) { // the page request started with "GET /x" - here we treat anything starting with /x special:
nixnax	142:54d1543e23e5	870
nixnax	142:54d1543e23e5	871	#define W3C_COMPLIANT_RESPONSE_NO
nixnax	142:54d1543e23e5	872	// change the above to W3C_COMPLIANT_RESPONSE_YES if you want a W3C.org compliant HTTP response
nixnax	142:54d1543e23e5	873	#ifdef W3C_COMPLIANT_RESPONSE_YES
nixnax	142:54d1543e23e5	874	n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (W3C.org required elements)
nixnax	146:a45f49a2b29c	875	n=n+sprintf(n+dataStart,"<body>%d</body>",ppp.responseCounter); // body = the http frame count
nixnax	142:54d1543e23e5	876	#else
nixnax	142:54d1543e23e5	877	if( httpGet6 == 'b' ) { // if the fetched page is "xb" send a meta command to let the browser continuously reload
nixnax	167:ff8a2d8beeb1	878	n=n+sprintf(n+dataStart, "<meta http-equiv=\"refresh\" content=\"0\">"); // reload loop - handy for benchmarking
nixnax	142:54d1543e23e5	879	}
nixnax	142:54d1543e23e5	880	// /x is a very short page, in fact, it is only a decimal number showing the http Page count
nixnax	146:a45f49a2b29c	881	n=n+sprintf(n+dataStart,"%d ",ppp.responseCounter); // not really valid html but most browsers and curl are ok with it
nixnax	142:54d1543e23e5	882	#endif
nixnax	142:54d1543e23e5	883	} else {
nixnax	142:54d1543e23e5	884	// all other requests get 404 Not Found response with a http frame count - nice for debugging
nixnax	142:54d1543e23e5	885	n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (required element)
nixnax	142:54d1543e23e5	886	n=n+sprintf(n+dataStart,"<body>Not Found</body>"); // not found message
nixnax	142:54d1543e23e5	887	}
nixnax	142:54d1543e23e5	888	}
nixnax	142:54d1543e23e5	889	#define CONTENTLENGTHSIZE 5
nixnax	142:54d1543e23e5	890	char contentLengthString[CONTENTLENGTHSIZE+1];
nixnax	142:54d1543e23e5	891	snprintf(contentLengthString,CONTENTLENGTHSIZE+1,"%*d",CONTENTLENGTHSIZE,n-nHeader); // print Content-Length with leading spaces and fixed width equal to csize
nixnax	142:54d1543e23e5	892	memcpy(dataStart+contentLengthStart, contentLengthString, CONTENTLENGTHSIZE); // copy Content-Length to it's place in the send buffer
nixnax	142:54d1543e23e5	893	return n; // total byte size of our response
nixnax	142:54d1543e23e5	894	}
nixnax	142:54d1543e23e5	895
nixnax	160:bd701ad564cb	896	/// Handle TCP data that is not an HTTP GET.
nixnax	160:bd701ad564cb	897	/// This is handy when for example you want to use netcat (nc.exe) to talk to PPP-Blinky.
nixnax	160:bd701ad564cb	898	/// This could also be a websocket receive event - especially if the first byte is 0x81 (websocket data push)
nixnax	142:54d1543e23e5	899	int tcpResponse(char * dataStart, int len, int * outFlags)
nixnax	142:54d1543e23e5	900	{
nixnax	142:54d1543e23e5	901	int n=0; // number of bytes we have printed so far
nixnax	142:54d1543e23e5	902	if (dataStart[0] == 0x81) { // check if this is a websocket push message
nixnax	160:bd701ad564cb	903	char mask [4];
nixnax	160:bd701ad564cb	904	memcpy ( mask, dataStart+2, 4); // websocket messages are "masked", so first we obtain the 4-byte mask
nixnax	160:bd701ad564cb	905	int websocketMessageSize = len - 6; // 1 byte prefix (0x81), 1 byte, 4 bytes mask = 6 bytes
nixnax	160:bd701ad564cb	906	if((dataStart[1]&0x80)==0x80) // test if the mask bit is set, which means all data is xor'ed with the mask
nixnax	160:bd701ad564cb	907	for (int i=0; i<websocketMessageSize; i++) dataStart[i+6]^= mask[i%4]; // unmask each byte with one of the mask bytes
nixnax	160:bd701ad564cb	908	dataStart[1] = len-2; // add four extra bytes to the message length because we don't use mask bytes for the send
nixnax	160:bd701ad564cb	909	memcpy(dataStart+2, "Got:",4); // insert our own text into the four mask bytes
nixnax	160:bd701ad564cb	910	n = len; // our response size remains exactly the same length as what we received
nixnax	142:54d1543e23e5	911	} else if ( (dataStart[0]==0x88) && (dataStart[1]==0x80) && (len == 6) ) { // test for a websocket close request
nixnax	142:54d1543e23e5	912	n=2; // our close command is only two bytes long because we don't use the four mask bytes
nixnax	142:54d1543e23e5	913	dataStart[1]=0; // we don't have mask bytes on
nixnax	160:bd701ad564cb	914	} else {
nixnax	160:bd701ad564cb	915	if (v1) putsWhileCheckingInput("TCP data received\n"); // all other tcp push packets
nixnax	163:d1b4328e9f08	916	}
nixnax	142:54d1543e23e5	917	return n; // total byte size of our response
nixnax	142:54d1543e23e5	918	}
nixnax	142:54d1543e23e5	919
nixnax	173:6774a0c851c4	920	/// dump the TCP data to the debug serial port
nixnax	173:6774a0c851c4	921	void dumpDataTCP(int outGoing)
nixnax	173:6774a0c851c4	922	{
nixnax	173:6774a0c851c4	923	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	173:6774a0c851c4	924	if (v2) {
nixnax	173:6774a0c851c4	925	// IP header
nixnax	173:6774a0c851c4	926	int packetLengthIp = __REV16(ppp.ip->lengthR ); // size of ip packet
nixnax	173:6774a0c851c4	927	int headerSizeIp = 4 * ppp.ip->headerLength; // size of ip header
nixnax	173:6774a0c851c4	928	// TCP header
nixnax	173:6774a0c851c4	929	ppp.tcpStart = ppp.ipStart + headerSizeIp; // calculate where the TCP header starts
nixnax	173:6774a0c851c4	930	int headerSizeTcp = 4 * (ppp.tcp->offset); // tcp "offset" for start of data is also the header size
nixnax	173:6774a0c851c4	931	ppp.tcpData = ppp.tcpStart + headerSizeTcp; // start of tcp data
nixnax	173:6774a0c851c4	932	int tcpSize = packetLengthIp - headerSizeIp; // tcp size = size of ip payload
nixnax	173:6774a0c851c4	933	int tcpDataSize = tcpSize - headerSizeTcp; // size of data block after TCP header
nixnax	173:6774a0c851c4	934	char pbuf[80]; // local print buffer
nixnax	173:6774a0c851c4	935	int n=0;
nixnax	173:6774a0c851c4	936	checkPc();
nixnax	173:6774a0c851c4	937	n=n+sprintf(pbuf+n, outGoing ? "\x1b[34m" : "\x1b[30m" ); // VT100 color code, print black for incoming, blue for outgoing headers
nixnax	173:6774a0c851c4	938	checkPc();
nixnax	173:6774a0c851c4	939	n=n+sprintf(pbuf+n, "IP:%d ipHeader:%d tcpHeader:%d tcpData:%d\n", packetLengthIp, headerSizeIp, headerSizeTcp, tcpDataSize); // 1 for more verbose
nixnax	173:6774a0c851c4	940	if (n>70) putsWhileCheckingInput("n>pbuf in dumpDataTCP()\n");
nixnax	173:6774a0c851c4	941	checkPc();
nixnax	173:6774a0c851c4	942	putsWhileCheckingInput( pbuf );
nixnax	173:6774a0c851c4	943	if (tcpDataSize > 0) {
nixnax	173:6774a0c851c4	944	ppp.tcpData[tcpDataSize]=0; // insert a null after the data so debug printf stops printing after the data
nixnax	173:6774a0c851c4	945	putsWhileCheckingInput( ppp.tcpData ); // print the tcp payload data
nixnax	173:6774a0c851c4	946	putsWhileCheckingInput("\n");
nixnax	173:6774a0c851c4	947	}
nixnax	173:6774a0c851c4	948	putsWhileCheckingInput( "\x1b[30m" ); // VT100 color code, print black
nixnax	173:6774a0c851c4	949	}
nixnax	173:6774a0c851c4	950	#endif
nixnax	173:6774a0c851c4	951	}
nixnax	173:6774a0c851c4	952
nixnax	142:54d1543e23e5	953	/// handle an incoming TCP packet
nixnax	142:54d1543e23e5	954	/// use the first few bytes to figure out if it's a websocket, an http request or just pure incoming TCP data
nixnax	142:54d1543e23e5	955	void tcpHandler()
nixnax	142:54d1543e23e5	956	{
nixnax	154:18b2bd92f557	957	int packetLengthIp = __REV16(ppp.ip->lengthR ); // size of ip packet
nixnax	154:18b2bd92f557	958	int headerSizeIp = 4 * ppp.ip->headerLength; // size of ip header
nixnax	173:6774a0c851c4	959	ppp.tcpStart = ppp.ipStart + headerSizeIp; // calculate TCP header start
nixnax	154:18b2bd92f557	960	int tcpSize = packetLengthIp - headerSizeIp; // tcp size = size of ip payload
nixnax	154:18b2bd92f557	961	int headerSizeTcp = 4 * (ppp.tcp->offset); // tcp "offset" for start of data is also the header size
nixnax	173:6774a0c851c4	962	char * tcpDataIn = ppp.tcpStart + headerSizeTcp; // start of data TCP data after TCP header
nixnax	154:18b2bd92f557	963	int tcpDataSize = tcpSize - headerSizeTcp; // size of data block after TCP header
nixnax	154:18b2bd92f557	964
nixnax	154:18b2bd92f557	965	unsigned int seq_in = __REV(ppp.tcp->seqTcpR);
nixnax	154:18b2bd92f557	966	unsigned int ack_in = __REV(ppp.tcp->ackTcpR);
nixnax	142:54d1543e23e5	967	unsigned int ack_out = seq_in + tcpDataSize;
nixnax	142:54d1543e23e5	968	unsigned int seq_out = ack_in; // use their version of our current sequence number
nixnax	142:54d1543e23e5	969
nixnax	142:54d1543e23e5	970	// first we shorten the TCP response header to only 20 bytes. This means we ignore all TCP option requests
nixnax	173:6774a0c851c4	971	headerSizeIp=20;
nixnax	173:6774a0c851c4	972	ppp.ip->headerLength = headerSizeIp/4; // ip header is 20 bytes long
nixnax	173:6774a0c851c4	973	ppp.ip->lengthR = __REV(40); // 20 ip header + 20 tcp header
nixnax	173:6774a0c851c4	974	//tcpSize = 20; // shorten total TCP packet size to 20 bytes (no data)
nixnax	154:18b2bd92f557	975	headerSizeTcp = 20; // shorten outgoing TCP header size 20 bytes
nixnax	173:6774a0c851c4	976	ppp.tcpStart = ppp.ipStart + headerSizeIp; // recalc TCP header start
nixnax	154:18b2bd92f557	977	ppp.tcp->offset = (headerSizeTcp/4);
nixnax	173:6774a0c851c4	978	char * tcpDataOut = ppp.tcpStart + headerSizeTcp; // start of outgoing data
nixnax	142:54d1543e23e5	979
nixnax	142:54d1543e23e5	980	int dataLen = 0; // most of our responses will have zero TCP data, only a header
nixnax	142:54d1543e23e5	981	int flagsOut = TCP_FLAG_ACK; // the default case is an ACK packet
nixnax	160:bd701ad564cb	982
nixnax	159:4d1bf96a59cd	983	ppp.tcp->windowR = __REV16( 700 ); // set tcp window size to 700 bytes
nixnax	142:54d1543e23e5	984
nixnax	142:54d1543e23e5	985	// A sparse TCP flag interpreter that implements stateless TCP connections
nixnax	142:54d1543e23e5	986
nixnax	156:163c23249731	987	switch ( ppp.tcp->flag.All ) {
nixnax	158:841592aed956	988	case TCP_FLAG_ACK: // handle ack messages by ignoring them
nixnax	142:54d1543e23e5	989	return;
nixnax	142:54d1543e23e5	990	case TCP_FLAG_SYN:
nixnax	142:54d1543e23e5	991	flagsOut = TCP_FLAG_SYN \| TCP_FLAG_ACK; // something wants to connect - acknowledge it
nixnax	142:54d1543e23e5	992	seq_out = seq_in+0x10000000U; // create a new sequence number using their sequence as a starting point, increase the highest digit
nixnax	142:54d1543e23e5	993	ack_out++; // for SYN flag we have to increase the sequence by 1
nixnax	142:54d1543e23e5	994	break;
nixnax	142:54d1543e23e5	995	case TCP_FLAG_ACK \| TCP_FLAG_PSH:
nixnax	142:54d1543e23e5	996	if ( (strncmp(tcpDataIn, "GET /", 5) == 0) ) { // check for an http GET command
nixnax	142:54d1543e23e5	997	flagsOut = TCP_FLAG_ACK \| TCP_FLAG_PSH; // set outgoing FIN flag to ask them to close from their side
nixnax	142:54d1543e23e5	998	dataLen = httpResponse(tcpDataOut); // send an http response
nixnax	142:54d1543e23e5	999	} else {
nixnax	158:841592aed956	1000	dataLen = tcpResponse(tcpDataOut,tcpDataSize, &flagsOut); // not an http GET, handle as a tcp connection
nixnax	142:54d1543e23e5	1001	}
nixnax	142:54d1543e23e5	1002	break;
nixnax	142:54d1543e23e5	1003	case TCP_FLAG_FIN:
nixnax	142:54d1543e23e5	1004	case TCP_FLAG_FIN \| TCP_FLAG_ACK:
nixnax	142:54d1543e23e5	1005	case TCP_FLAG_FIN \| TCP_FLAG_PSH \| TCP_FLAG_ACK:
nixnax	142:54d1543e23e5	1006	flagsOut = TCP_FLAG_ACK \| TCP_FLAG_FIN; // set outgoing FIN flag to ask them to close from their side
nixnax	142:54d1543e23e5	1007	ack_out++; // for FIN flag we have to increase the sequence by 1
nixnax	142:54d1543e23e5	1008	break;
nixnax	142:54d1543e23e5	1009	default:
nixnax	142:54d1543e23e5	1010	return; // ignore remaining packets
nixnax	142:54d1543e23e5	1011	} // switch
nixnax	142:54d1543e23e5	1012
nixnax	142:54d1543e23e5	1013	// The TCP flag handling is now done
nixnax	142:54d1543e23e5	1014	// first we swap source and destination TCP addresses and insert the new ack and seq numbers
nixnax	147:0f40005cbc5f	1015	swapIpAddresses(); // swap IP source and destination addresses
nixnax	149:969d98f6fb88	1016	swapIpPorts(); // swap IP source and destination ports
nixnax	142:54d1543e23e5	1017
nixnax	158:841592aed956	1018	ppp.tcp->ackTcpR = __REV( ack_out ); // byte reversed - tcp/ip messages are big-endian (high byte first)
nixnax	158:841592aed956	1019	ppp.tcp->seqTcpR = __REV( seq_out ); // byte reversed - tcp/ip messages are big-endian (high byte first)
nixnax	160:bd701ad564cb	1020
nixnax	156:163c23249731	1021	ppp.tcp->flag.All = flagsOut; // update the TCP flags
nixnax	142:54d1543e23e5	1022
nixnax	159:4d1bf96a59cd	1023	// recalculate all the header sizes
nixnax	154:18b2bd92f557	1024	tcpSize = headerSizeTcp + dataLen; // tcp packet size
nixnax	154:18b2bd92f557	1025	int newPacketSize = headerSizeIp + tcpSize; // calculate size of the outgoing packet
nixnax	159:4d1bf96a59cd	1026	ppp.ip->lengthR = __REV16 ( newPacketSize );
nixnax	142:54d1543e23e5	1027	ppp.pkt.len = newPacketSize+4+2; // ip packet length + 4-byte ppp prefix (ff 03 00 21) + 2 fcs (crc) bytes bytes at the end of the packet
nixnax	142:54d1543e23e5	1028
nixnax	142:54d1543e23e5	1029	// the header is all set up, now do the IP and TCP checksums
nixnax	146:a45f49a2b29c	1030	IpHeaderCheckSum(); // calculate new IP header checksum
nixnax	170:3d3b2126181c	1031	checkSumPseudoHeader( tcpSize ); // get the TCP pseudo-header checksum
nixnax	159:4d1bf96a59cd	1032	ppp.tcp->checksumR = 0; // before TCP checksum calculations the checksum bytes must be set cleared
nixnax	161:d59f778bc8ab	1033	unsigned int pseudoHeaderSum=dataCheckSum(ppp.tcpStart,tcpSize, 0); // continue the TCP checksum on the whole TCP packet
nixnax	159:4d1bf96a59cd	1034	ppp.tcp->checksumR = __REV16( pseudoHeaderSum); // tcp checksum done, store it in the TCP header
nixnax	160:bd701ad564cb	1035
nixnax	170:3d3b2126181c	1036	dumpHeaderIP(1); // dump outgoing IP header before sending the frame
nixnax	170:3d3b2126181c	1037	dumpHeaderTCP(1); // dump outgoing TCP header before sending the frame
nixnax	173:6774a0c851c4	1038	dumpDataTCP(1); // dump outgoing TCP data before sending the frame
nixnax	171:46b36d4edd1d	1039
nixnax	142:54d1543e23e5	1040	for (int i=0; i<45*1000/10; i++) { // 45 ms delay before sending frame - a typical internet delay time
nixnax	142:54d1543e23e5	1041	checkPc(); // catch any incoming characters
nixnax	142:54d1543e23e5	1042	wait_us(10); // wait less than 1 character duration at 115200
nixnax	142:54d1543e23e5	1043	}
nixnax	144:01d98cf7738e	1044	sendPppFrame(); // All preparation complete - send the TCP response
nixnax	142:54d1543e23e5	1045	if(0) dumpPPPFrame(); // set to 1 to dump transmitted ppp frame
nixnax	142:54d1543e23e5	1046	memset(ppp.pkt.buf+44,0,500); // flush out traces of previous data that we may scan for
nixnax	142:54d1543e23e5	1047	}
nixnax	142:54d1543e23e5	1048
nixnax	142:54d1543e23e5	1049	/// handle an incoming TCP packet
nixnax	142:54d1543e23e5	1050	void TCPpacket()
nixnax	142:54d1543e23e5	1051	{
nixnax	173:6774a0c851c4	1052	dumpHeaderIP(0); // dump incoming packet IP header
nixnax	173:6774a0c851c4	1053	dumpHeaderTCP(0); // dump incoming packet TCP header
nixnax	173:6774a0c851c4	1054	dumpDataTCP(0); // dump incoming packet data
nixnax	142:54d1543e23e5	1055	tcpHandler();
nixnax	142:54d1543e23e5	1056	}
nixnax	142:54d1543e23e5	1057
nixnax	142:54d1543e23e5	1058	/// handle the remaining IP protocols by ignoring them
nixnax	142:54d1543e23e5	1059	void otherProtocol()
nixnax	142:54d1543e23e5	1060	{
nixnax	142:54d1543e23e5	1061	debugPrintf("Other IP protocol");
nixnax	142:54d1543e23e5	1062	}
nixnax	142:54d1543e23e5	1063
nixnax	142:54d1543e23e5	1064	/// process an incoming IP packet
nixnax	142:54d1543e23e5	1065	void IPframe()
nixnax	142:54d1543e23e5	1066	{
nixnax	167:ff8a2d8beeb1	1067	int protocol = ppp.ip->protocol;
nixnax	142:54d1543e23e5	1068	switch (protocol) {
nixnax	142:54d1543e23e5	1069	case 1:
nixnax	142:54d1543e23e5	1070	ICMPpacket();
nixnax	142:54d1543e23e5	1071	break;
nixnax	142:54d1543e23e5	1072	case 2:
nixnax	142:54d1543e23e5	1073	IGMPpacket();
nixnax	142:54d1543e23e5	1074	break;
nixnax	142:54d1543e23e5	1075	case 17:
nixnax	142:54d1543e23e5	1076	UDPpacket();
nixnax	142:54d1543e23e5	1077	break;
nixnax	142:54d1543e23e5	1078	case 6:
nixnax	142:54d1543e23e5	1079	TCPpacket();
nixnax	142:54d1543e23e5	1080	break;
nixnax	142:54d1543e23e5	1081	default:
nixnax	142:54d1543e23e5	1082	otherProtocol();
nixnax	142:54d1543e23e5	1083	}
nixnax	142:54d1543e23e5	1084	}
nixnax	142:54d1543e23e5	1085
nixnax	142:54d1543e23e5	1086	/// respond to LCP (line configuration protocol) configuration request) by allowing no options
nixnax	142:54d1543e23e5	1087	void LCPconfReq()
nixnax	142:54d1543e23e5	1088	{
nixnax	142:54d1543e23e5	1089	debugPrintf("LCP Config ");
nixnax	175:b4e6f8a6fe00	1090	if ( ppp.lcp->lengthR != __REV16(4) ) {
nixnax	175:b4e6f8a6fe00	1091	ppp.lcp->code=4; // allow only "no options" which means Maximum Receive Unit (MRU) is default 1500 bytes
nixnax	142:54d1543e23e5	1092	debugPrintf("Reject\n");
nixnax	144:01d98cf7738e	1093	sendPppFrame();
nixnax	142:54d1543e23e5	1094	} else {
nixnax	175:b4e6f8a6fe00	1095	ppp.lcp->code=2; // ack zero conf
nixnax	142:54d1543e23e5	1096	debugPrintf("Ack\n");
nixnax	144:01d98cf7738e	1097	sendPppFrame();
nixnax	142:54d1543e23e5	1098	debugPrintf("LCP Ask\n");
nixnax	175:b4e6f8a6fe00	1099	ppp.lcp->code=1; // request no options
nixnax	144:01d98cf7738e	1100	sendPppFrame();
nixnax	142:54d1543e23e5	1101	}
nixnax	142:54d1543e23e5	1102	}
nixnax	142:54d1543e23e5	1103
nixnax	142:54d1543e23e5	1104	/// handle LCP acknowledge packets by ignoring them
nixnax	142:54d1543e23e5	1105	void LCPconfAck()
nixnax	142:54d1543e23e5	1106	{
nixnax	142:54d1543e23e5	1107	debugPrintf("LCP Ack\n");
nixnax	142:54d1543e23e5	1108	}
nixnax	142:54d1543e23e5	1109
nixnax	143:c5019f856a56	1110	/// handle LCP end (disconnect) packets by acknowledging them and by setting ppp.online to false
nixnax	142:54d1543e23e5	1111	void LCPend()
nixnax	142:54d1543e23e5	1112	{
nixnax	175:b4e6f8a6fe00	1113	ppp.lcp->code=6; // end
nixnax	144:01d98cf7738e	1114	sendPppFrame(); // acknowledge
nixnax	142:54d1543e23e5	1115	ppp.online=0; // start hunting for connect string again
nixnax	142:54d1543e23e5	1116	pppInitStruct(); // flush the receive buffer
nixnax	143:c5019f856a56	1117	debugPrintf("LCP End (Disconnect from host)\n");
nixnax	142:54d1543e23e5	1118	}
nixnax	142:54d1543e23e5	1119
nixnax	142:54d1543e23e5	1120	/// respond to other LCP requests by ignoring them
nixnax	142:54d1543e23e5	1121	void LCPother()
nixnax	142:54d1543e23e5	1122	{
nixnax	142:54d1543e23e5	1123	debugPrintf("LCP Other\n");
nixnax	142:54d1543e23e5	1124	dumpPPPFrame();
nixnax	142:54d1543e23e5	1125	}
nixnax	142:54d1543e23e5	1126
nixnax	142:54d1543e23e5	1127	/// process incoming LCP packets
nixnax	142:54d1543e23e5	1128	void LCPframe()
nixnax	142:54d1543e23e5	1129	{
nixnax	175:b4e6f8a6fe00	1130	int code = ppp.lcp->code;
nixnax	142:54d1543e23e5	1131	switch (code) {
nixnax	142:54d1543e23e5	1132	case 1:
nixnax	142:54d1543e23e5	1133	LCPconfReq();
nixnax	142:54d1543e23e5	1134	break; // config request
nixnax	142:54d1543e23e5	1135	case 2:
nixnax	142:54d1543e23e5	1136	LCPconfAck();
nixnax	142:54d1543e23e5	1137	break; // config ack
nixnax	142:54d1543e23e5	1138	case 5:
nixnax	142:54d1543e23e5	1139	LCPend();
nixnax	142:54d1543e23e5	1140	break; // end connection
nixnax	142:54d1543e23e5	1141	default:
nixnax	142:54d1543e23e5	1142	LCPother();
nixnax	142:54d1543e23e5	1143	}
nixnax	142:54d1543e23e5	1144	}
nixnax	142:54d1543e23e5	1145
nixnax	142:54d1543e23e5	1146	/// discard packets that are not IP, IPCP, or LCP
nixnax	142:54d1543e23e5	1147	void discardedFrame()
nixnax	142:54d1543e23e5	1148	{
nixnax	142:54d1543e23e5	1149	if (v0) debugPrintf("Frame is not IP, IPCP or LCP: %02x %02x %02x %02x\n", ppp.pkt.buf[0],ppp.pkt.buf[1],ppp.pkt.buf[2],ppp.pkt.buf[3]);
nixnax	142:54d1543e23e5	1150	}
nixnax	142:54d1543e23e5	1151
nixnax	142:54d1543e23e5	1152	/// determine the packet type (IP, IPCP or LCP) of incoming packets
nixnax	142:54d1543e23e5	1153	void determinePacketType()
nixnax	142:54d1543e23e5	1154	{
nixnax	167:ff8a2d8beeb1	1155	if ( ppp.ppp->address != 0xff ) {
nixnax	167:ff8a2d8beeb1	1156	debugPrintf("Unexpected: PPP address != ff\n");
nixnax	142:54d1543e23e5	1157	return;
nixnax	142:54d1543e23e5	1158	}
nixnax	167:ff8a2d8beeb1	1159	if ( ppp.ppp->control != 3 ) {
nixnax	167:ff8a2d8beeb1	1160	debugPrintf("Unexpected: PPP control != 3\n");
nixnax	142:54d1543e23e5	1161	return;
nixnax	142:54d1543e23e5	1162	}
nixnax	167:ff8a2d8beeb1	1163	unsigned int protocol = __REV16( ppp.ppp->protocolR );
nixnax	167:ff8a2d8beeb1	1164	switch ( protocol ) {
nixnax	167:ff8a2d8beeb1	1165	case 0xc021:
nixnax	142:54d1543e23e5	1166	LCPframe();
nixnax	142:54d1543e23e5	1167	break; // link control
nixnax	167:ff8a2d8beeb1	1168	case 0x8021:
nixnax	142:54d1543e23e5	1169	IPCPframe();
nixnax	142:54d1543e23e5	1170	break; // IP control
nixnax	167:ff8a2d8beeb1	1171	case 0x0021:
nixnax	142:54d1543e23e5	1172	IPframe();
nixnax	142:54d1543e23e5	1173	break; // IP itself
nixnax	142:54d1543e23e5	1174	default:
nixnax	142:54d1543e23e5	1175	discardedFrame();
nixnax	142:54d1543e23e5	1176	}
nixnax	142:54d1543e23e5	1177	}
nixnax	142:54d1543e23e5	1178
nixnax	146:a45f49a2b29c	1179	/// a sniffer tool to assist in figuring out where in the code we are having characters in the input buffer
nixnax	146:a45f49a2b29c	1180	void sniff()
nixnax	146:a45f49a2b29c	1181	{
nixnax	146:a45f49a2b29c	1182	if ( pc.readable() ) putsWhileCheckingInput( "Sniff - Char available!\n" ); // if this prints anything it means there is a character in the serial receive buffer
nixnax	146:a45f49a2b29c	1183	}
nixnax	146:a45f49a2b29c	1184
nixnax	142:54d1543e23e5	1185	/// scan the PPP serial input stream for frame start markers
nixnax	143:c5019f856a56	1186	void waitForPppFrame()
nixnax	142:54d1543e23e5	1187	{
nixnax	142:54d1543e23e5	1188	while(1) {
nixnax	142:54d1543e23e5	1189	checkPc(); // handle received characters
nixnax	142:54d1543e23e5	1190	if ( ppp.rx.head != ppp.rx.tail ) {
nixnax	142:54d1543e23e5	1191	int oldTail = ppp.rx.tail; // remember where the character is located in the buffer
nixnax	142:54d1543e23e5	1192	int rx = pc_getBuf(); // get the character
nixnax	142:54d1543e23e5	1193	if (rx==FRAME_7E) {
nixnax	142:54d1543e23e5	1194	if (ppp.firstFrame) { // is this the start of the first frame start
nixnax	142:54d1543e23e5	1195	ppp.firstFrame=0;
nixnax	142:54d1543e23e5	1196	ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
nixnax	142:54d1543e23e5	1197	ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where first frame started
nixnax	142:54d1543e23e5	1198	} else {
nixnax	142:54d1543e23e5	1199	ppp.hdlc.frameEndIndex=oldTail; // mark the frame end character
nixnax	142:54d1543e23e5	1200	processPPPFrame(ppp.hdlc.frameStartIndex, ppp.hdlc.frameEndIndex); // process the frame
nixnax	142:54d1543e23e5	1201	ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
nixnax	142:54d1543e23e5	1202	ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where next frame started
nixnax	142:54d1543e23e5	1203	break;
nixnax	142:54d1543e23e5	1204	}
nixnax	142:54d1543e23e5	1205	}
nixnax	142:54d1543e23e5	1206	}
nixnax	142:54d1543e23e5	1207	}
nixnax	142:54d1543e23e5	1208	}
nixnax	142:54d1543e23e5	1209
nixnax	153:7993def8663f	1210	/// Wait for a dial-up modem connect command ("CLIENT") from the host PC, if found, we set ppp.online to true, which will start the IP packet scanner.
nixnax	153:7993def8663f	1211	// Note: a 0x7E in the input stream (ppp start of frame character) will also set ppp.online to true - see checkPc();
nixnax	153:7993def8663f	1212	void waitForPcConnectString()
nixnax	142:54d1543e23e5	1213	{
nixnax	142:54d1543e23e5	1214	while(ppp.online == 0) {
nixnax	142:54d1543e23e5	1215	checkPc(); // gather received characters
nixnax	142:54d1543e23e5	1216	// search for Windows Dialup Networking "Direct Connection Between Two Computers" expected connect string
nixnax	142:54d1543e23e5	1217	char * found1 = strstr( (char *)ppp.rx.buf, "CLIENT" );
nixnax	142:54d1543e23e5	1218	if (found1 != NULL) {
nixnax	142:54d1543e23e5	1219	// respond with Windows Dialup networking expected "Direct Connection Between Two Computers" response string
nixnax	143:c5019f856a56	1220	if (v0) debugPrintf("Connected: Found connect string \"CLIENT\", sent \"CLIENTSERVER\"\n");
nixnax	142:54d1543e23e5	1221	pc.puts("CLIENTSERVER");
nixnax	142:54d1543e23e5	1222	ppp.online=1; // we are connected - set flag so we stop looking for the connect string
nixnax	142:54d1543e23e5	1223	checkPc();
nixnax	142:54d1543e23e5	1224	}
nixnax	142:54d1543e23e5	1225	}
nixnax	142:54d1543e23e5	1226	}
nixnax	142:54d1543e23e5	1227
nixnax	144:01d98cf7738e	1228	/// Initialize PPP data structure and set serial port(s) baud rate(s)
nixnax	144:01d98cf7738e	1229	void initializePpp()
nixnax	142:54d1543e23e5	1230	{
nixnax	142:54d1543e23e5	1231	pc.baud(115200); // USB serial port to pc
nixnax	144:01d98cf7738e	1232	debugBaudRate(115200); // baud rate for (optional) debug serial port
nixnax	142:54d1543e23e5	1233	debugPrintf("\x1b[2J\x1b[H\x1b[30mmbed PPP-Blinky HTTP & WebSocket server ready :)\n"); // VT100 codes for clear_screen, home, black_text - Tera Term is a handy VT100 terminal
nixnax	142:54d1543e23e5	1234	pppInitStruct(); // initialize all the PPP properties
nixnax	143:c5019f856a56	1235	}

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Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	27 Dec 2016
Imports:	426
Forks:	1
Commits:	276
Dependents:	0
Dependencies:	1
Followers:	22

The code in this repository is MIT licensed.