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@165:c47826d07e0d, 2017-09-03 (annotated)

Committer:: nixnax
Date:: Sun Sep 03 19:19:03 2017 +0000
Revision:: 165:c47826d07e0d
Parent:: 164:c3de3d212c4b
Child:: 166:0386c2d5dc89

ICMP header structure. ICMP handler rewrite.

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	165:c47826d07e0d	48	#define SERIAL_PORT_MONITOR_YES /* 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	150:3366bf3d294e	108	// this is websocket demo 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	165:c47826d07e0d	158	/// a structure to keep all our ppp variables in
nixnax	142:54d1543e23e5	159	struct pppType {
nixnax	154:18b2bd92f557	160	pppHeaderType * ppp; // pointer to ppp struct
nixnax	154:18b2bd92f557	161	union {
nixnax	154:18b2bd92f557	162	ipHeaderType * ip; // pointer to ip header struct
nixnax	155:9c6a1d249e26	163	char * ipStart; // char pointer to ip header struct (need a char pointer for byte offset calculations)
nixnax	154:18b2bd92f557	164	};
nixnax	154:18b2bd92f557	165	union {
nixnax	154:18b2bd92f557	166	tcpHeaderType * tcp; // pointer to tcp header struct
nixnax	155:9c6a1d249e26	167	char * tcpStart; // char pointer to tcp header struct (need a char pointer for byte offset calculations)
nixnax	163:d1b4328e9f08	168	udpHeaderType * udp; // pointer to udp header struct
nixnax	163:d1b4328e9f08	169	char * udpStart; // char pointer to udp header struct (need a char pointer for byte offset calculations)
nixnax	165:c47826d07e0d	170	icmpHeaderType * icmp; // pointer to udp header struct
nixnax	165:c47826d07e0d	171	char * icmpStart; // char pointer to icmp header struct (need a char pointer for byte offset calculations)
nixnax	160:bd701ad564cb	172	};
nixnax	142:54d1543e23e5	173	int online; // we hunt for a PPP connection if this is zero
nixnax	143:c5019f856a56	174	int hostIP; // ip address of host
nixnax	145:098b6ed2f7f2	175	int fcs; // PPP "frame check sequence" - a 16-bit HDLC-like checksum used in all PPP frames
nixnax	142:54d1543e23e5	176	int ledState; // state of LED1
nixnax	146:a45f49a2b29c	177	int responseCounter;
nixnax	142:54d1543e23e5	178	int firstFrame; // cleared after first frame
nixnax	159:4d1bf96a59cd	179	unsigned int sum; // a checksum used in headers
nixnax	142:54d1543e23e5	180	struct {
nixnax	142:54d1543e23e5	181	#define RXBUFLEN (1<<11)
nixnax	142:54d1543e23e5	182	// the serial port receive buffer and packet buffer, size is RXBUFLEN (currently 2048 bytes)
nixnax	142:54d1543e23e5	183	char buf[RXBUFLEN]; // RXBUFLEN MUST be a power of two because we use & operator for fast wrap-around in ring buffer
nixnax	142:54d1543e23e5	184	int head;
nixnax	142:54d1543e23e5	185	int tail;
nixnax	142:54d1543e23e5	186	int rtail;
nixnax	142:54d1543e23e5	187	int buflevel;
nixnax	142:54d1543e23e5	188	} rx; // serial port objects
nixnax	142:54d1543e23e5	189	struct {
nixnax	142:54d1543e23e5	190	int len; // number of bytes in buffer
nixnax	142:54d1543e23e5	191	int crc; // PPP CRC (frame check)
nixnax	152:025c73b6c0a9	192	#define PPP_max_size 1600
nixnax	152:025c73b6c0a9	193	// we are assuming 100 bytes more than MTU size of 1500
nixnax	154:18b2bd92f557	194	char buf[PPP_max_size]; // send and receive buffer large enough for largest IP packet
nixnax	142:54d1543e23e5	195	} pkt; // ppp buffer objects
nixnax	142:54d1543e23e5	196	struct {
nixnax	142:54d1543e23e5	197	int frameStartIndex; // frame start marker
nixnax	142:54d1543e23e5	198	int frameEndIndex; // frame end marker
nixnax	142:54d1543e23e5	199	} hdlc; // hdlc frame objects
nixnax	142:54d1543e23e5	200	struct {
nixnax	142:54d1543e23e5	201	unsigned int ident; // our IP ident value (outgoing frame count)
nixnax	154:18b2bd92f557	202	} ipData; // ip related object
nixnax	142:54d1543e23e5	203	};
nixnax	142:54d1543e23e5	204
nixnax	142:54d1543e23e5	205	pppType ppp; // our global - definitely not thread safe
nixnax	142:54d1543e23e5	206
nixnax	142:54d1543e23e5	207	/// Initialize the ppp structure and clear the receive buffer
nixnax	142:54d1543e23e5	208	void pppInitStruct()
nixnax	142:54d1543e23e5	209	{
nixnax	142:54d1543e23e5	210	memset( ppp.rx.buf, 0, RXBUFLEN);
nixnax	142:54d1543e23e5	211	ppp.online=0;
nixnax	142:54d1543e23e5	212	ppp.rx.tail=0;
nixnax	142:54d1543e23e5	213	ppp.rx.rtail=0;
nixnax	142:54d1543e23e5	214	ppp.rx.head=0;
nixnax	142:54d1543e23e5	215	ppp.rx.buflevel=0;
nixnax	142:54d1543e23e5	216	ppp.pkt.len=0;
nixnax	154:18b2bd92f557	217	ppp.ipData.ident=10000; // easy to recognize in ip packet dumps
nixnax	142:54d1543e23e5	218	ppp.ledState=0;
nixnax	142:54d1543e23e5	219	ppp.hdlc.frameStartIndex=0;
nixnax	146:a45f49a2b29c	220	ppp.responseCounter=0;
nixnax	142:54d1543e23e5	221	ppp.firstFrame=1;
nixnax	154:18b2bd92f557	222	ppp.ppp = (pppHeaderType *)ppp.pkt.buf;
nixnax	154:18b2bd92f557	223	ppp.ip = (ipHeaderType *)(ppp.pkt.buf+4); // ppp header is 4 bytes long
nixnax	142:54d1543e23e5	224	}
nixnax	142:54d1543e23e5	225
nixnax	142:54d1543e23e5	226	/// Toggle the LED on every second PPP packet received
nixnax	142:54d1543e23e5	227	void led1Toggle()
nixnax	142:54d1543e23e5	228	{
nixnax	142:54d1543e23e5	229	led1 = (ppp.ledState >> 1) & 1; // use second bit, in other words toggle LED only every second packet
nixnax	143:c5019f856a56	230	ppp.ledState++;
nixnax	142:54d1543e23e5	231	}
nixnax	142:54d1543e23e5	232
nixnax	152:025c73b6c0a9	233	/// returns 1 after a connect message, 0 at startup or after a disconnect message
nixnax	150:3366bf3d294e	234	int connectedPpp()
nixnax	142:54d1543e23e5	235	{
nixnax	142:54d1543e23e5	236	return ppp.online;
nixnax	143:c5019f856a56	237	}
nixnax	142:54d1543e23e5	238
nixnax	143:c5019f856a56	239	/// Check for available characters from the PC and read them into our own circular serial receive buffer at ppp.rx.buf.
nixnax	143:c5019f856a56	240	/// Also, if we are offline and a 0x7e frame start character is seen, we go online immediately
nixnax	142:54d1543e23e5	241	void checkPc()
nixnax	142:54d1543e23e5	242	{
nixnax	142:54d1543e23e5	243	char ch;
nixnax	142:54d1543e23e5	244	if ( pc.readable() ) {
nixnax	142:54d1543e23e5	245	int hd = (ppp.rx.head+1)&(RXBUFLEN-1); // increment/wrap head index
nixnax	142:54d1543e23e5	246	if ( hd == ppp.rx.rtail ) {
nixnax	142:54d1543e23e5	247	debugPrintf("\nReceive buffer full\n");
nixnax	142:54d1543e23e5	248	return;
nixnax	142:54d1543e23e5	249	}
nixnax	142:54d1543e23e5	250	ch = pc.getc(); // read new character
nixnax	142:54d1543e23e5	251	ppp.rx.buf[ppp.rx.head] = ch; // insert in our receive buffer
nixnax	142:54d1543e23e5	252	if ( ppp.online == 0 ) {
nixnax	142:54d1543e23e5	253	if (ch == 0x7E) {
nixnax	142:54d1543e23e5	254	ppp.online = 1;
nixnax	142:54d1543e23e5	255	}
nixnax	142:54d1543e23e5	256	}
nixnax	142:54d1543e23e5	257	ppp.rx.head = hd; // update head pointer
nixnax	142:54d1543e23e5	258	ppp.rx.buflevel++;
nixnax	142:54d1543e23e5	259	}
nixnax	142:54d1543e23e5	260	}
nixnax	142:54d1543e23e5	261
nixnax	142:54d1543e23e5	262	/// print to debug port while checking for incoming characters
nixnax	142:54d1543e23e5	263	void putcWhileCheckingInput( char outByte )
nixnax	142:54d1543e23e5	264	{
nixnax	142:54d1543e23e5	265	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	266	checkPc();
nixnax	142:54d1543e23e5	267	debugPutc( outByte );
nixnax	142:54d1543e23e5	268	checkPc();
nixnax	142:54d1543e23e5	269	#endif
nixnax	142:54d1543e23e5	270	}
nixnax	142:54d1543e23e5	271
nixnax	142:54d1543e23e5	272	/// puts to debug port while checking the PPP input stream
nixnax	142:54d1543e23e5	273	void putsWhileCheckingInput( char * data )
nixnax	142:54d1543e23e5	274	{
nixnax	142:54d1543e23e5	275	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	276	char * nextChar = data;
nixnax	142:54d1543e23e5	277	while( *nextChar != 0 ) {
nixnax	142:54d1543e23e5	278	putcWhileCheckingInput( *nextChar ); // write one character to debug port while checking input
nixnax	142:54d1543e23e5	279	nextChar++;
nixnax	142:54d1543e23e5	280	}
nixnax	142:54d1543e23e5	281	#endif
nixnax	142:54d1543e23e5	282	}
nixnax	142:54d1543e23e5	283
nixnax	145:098b6ed2f7f2	284	/// Initialize the PPP FCS (frame check sequence) total
nixnax	145:098b6ed2f7f2	285	void fcsReset()
nixnax	142:54d1543e23e5	286	{
nixnax	145:098b6ed2f7f2	287	ppp.fcs=0xffff; // crc restart
nixnax	142:54d1543e23e5	288	}
nixnax	142:54d1543e23e5	289
nixnax	145:098b6ed2f7f2	290	/// update the cumulative PPP FCS (frame check sequence)
nixnax	145:098b6ed2f7f2	291	void fcsDo(int x)
nixnax	142:54d1543e23e5	292	{
nixnax	142:54d1543e23e5	293	for (int i=0; i<8; i++) {
nixnax	145:098b6ed2f7f2	294	ppp.fcs=((ppp.fcs&1)^(x&1))?(ppp.fcs>>1)^0x8408:ppp.fcs>>1; // crc calculator
nixnax	142:54d1543e23e5	295	x>>=1;
nixnax	142:54d1543e23e5	296	}
nixnax	142:54d1543e23e5	297	checkPc(); // handle input
nixnax	142:54d1543e23e5	298	}
nixnax	142:54d1543e23e5	299
nixnax	145:098b6ed2f7f2	300	/// calculate the PPP FCS (frame check sequence) on an entire block of memory
nixnax	145:098b6ed2f7f2	301	int fcsBuf(char * buf, int size) // crc on an entire block of memory
nixnax	142:54d1543e23e5	302	{
nixnax	145:098b6ed2f7f2	303	fcsReset();
nixnax	145:098b6ed2f7f2	304	for(int i=0; i<size; i++)fcsDo(*buf++);
nixnax	145:098b6ed2f7f2	305	return ppp.fcs;
nixnax	142:54d1543e23e5	306	}
nixnax	142:54d1543e23e5	307
nixnax	142:54d1543e23e5	308	/// Get one character from our received PPP buffer
nixnax	142:54d1543e23e5	309	int pc_getBuf()
nixnax	142:54d1543e23e5	310	{
nixnax	142:54d1543e23e5	311	int x = ppp.rx.buf[ ppp.rx.tail ];
nixnax	142:54d1543e23e5	312	ppp.rx.tail=(ppp.rx.tail+1)&(RXBUFLEN-1);
nixnax	142:54d1543e23e5	313	ppp.rx.buflevel--;
nixnax	142:54d1543e23e5	314	return x;
nixnax	142:54d1543e23e5	315	}
nixnax	142:54d1543e23e5	316
nixnax	142:54d1543e23e5	317	/// Dump a PPP frame to the debug serial port
nixnax	142:54d1543e23e5	318	/// Note - the hex output of dumpPPPFrame() can be imported into WireShark
nixnax	142:54d1543e23e5	319	/// Capture the frame's hex output in your terminal program and save as a text file
nixnax	164:c3de3d212c4b	320	/// In WireShark, use "Import Hex File". Import options are: Offset=None, Protocol=PPP.
nixnax	142:54d1543e23e5	321	void dumpPPPFrame()
nixnax	142:54d1543e23e5	322	{
nixnax	142:54d1543e23e5	323	char pbuf[30];
nixnax	142:54d1543e23e5	324	for(int i=0; i<ppp.pkt.len; i++) {
nixnax	142:54d1543e23e5	325	checkPc();
nixnax	142:54d1543e23e5	326	sprintf(pbuf, "%02x ", ppp.pkt.buf[i]);
nixnax	142:54d1543e23e5	327	checkPc();
nixnax	142:54d1543e23e5	328	putsWhileCheckingInput(pbuf);
nixnax	142:54d1543e23e5	329	}
nixnax	142:54d1543e23e5	330	checkPc();
nixnax	142:54d1543e23e5	331	sprintf(pbuf, " CRC=%04x Len=%d\n", ppp.pkt.crc, ppp.pkt.len);
nixnax	142:54d1543e23e5	332	checkPc();
nixnax	142:54d1543e23e5	333	putsWhileCheckingInput(pbuf);
nixnax	142:54d1543e23e5	334	}
nixnax	142:54d1543e23e5	335
nixnax	142:54d1543e23e5	336	/// Process a received PPP frame
nixnax	142:54d1543e23e5	337	void processPPPFrame(int start, int end)
nixnax	142:54d1543e23e5	338	{
nixnax	142:54d1543e23e5	339	led1Toggle(); // change led1 state on every frame we receive
nixnax	142:54d1543e23e5	340	if(start==end) {
nixnax	142:54d1543e23e5	341	return; // empty frame
nixnax	142:54d1543e23e5	342	}
nixnax	145:098b6ed2f7f2	343	fcsReset();
nixnax	142:54d1543e23e5	344	char * dest = ppp.pkt.buf;
nixnax	142:54d1543e23e5	345	ppp.pkt.len=0;
nixnax	142:54d1543e23e5	346	int unstuff=0;
nixnax	142:54d1543e23e5	347	int idx = start;
nixnax	142:54d1543e23e5	348	while(1) {
nixnax	142:54d1543e23e5	349	checkPc();
nixnax	142:54d1543e23e5	350	if (unstuff==0) {
nixnax	142:54d1543e23e5	351	if (ppp.rx.buf[idx]==0x7d) unstuff=1;
nixnax	142:54d1543e23e5	352	else {
nixnax	142:54d1543e23e5	353	*dest = ppp.rx.buf[idx];
nixnax	142:54d1543e23e5	354	ppp.pkt.len++;
nixnax	142:54d1543e23e5	355	dest++;
nixnax	145:098b6ed2f7f2	356	fcsDo(ppp.rx.buf[idx]);
nixnax	142:54d1543e23e5	357	}
nixnax	142:54d1543e23e5	358	} else { // unstuff characters prefixed with 0x7d
nixnax	142:54d1543e23e5	359	*dest = ppp.rx.buf[idx]^0x20;
nixnax	142:54d1543e23e5	360	ppp.pkt.len++;
nixnax	142:54d1543e23e5	361	dest++;
nixnax	145:098b6ed2f7f2	362	fcsDo(ppp.rx.buf[idx]^0x20);
nixnax	142:54d1543e23e5	363	unstuff=0;
nixnax	142:54d1543e23e5	364	}
nixnax	142:54d1543e23e5	365	idx = (idx+1) & (RXBUFLEN-1);
nixnax	142:54d1543e23e5	366	if (idx == end) break;
nixnax	142:54d1543e23e5	367	}
nixnax	145:098b6ed2f7f2	368	ppp.pkt.crc = ppp.fcs & 0xffff;
nixnax	142:54d1543e23e5	369	if(0) dumpPPPFrame(); // set to 1 to dump ALL ppp frames
nixnax	142:54d1543e23e5	370	if (ppp.pkt.crc == 0xf0b8) { // check for good CRC
nixnax	142:54d1543e23e5	371	determinePacketType();
nixnax	142:54d1543e23e5	372	} else {
nixnax	142:54d1543e23e5	373	#define REPORT_FCS_ERROR_YES
nixnax	142:54d1543e23e5	374	#ifdef REPORT_FCS_ERROR_YES
nixnax	142:54d1543e23e5	375	char pbuf[50]; // local print buffer
nixnax	142:54d1543e23e5	376	checkPc();
nixnax	142:54d1543e23e5	377	sprintf(pbuf, "\nPPP FCS(crc) Error CRC=%x Length = %d\n",ppp.pkt.crc,ppp.pkt.len); // print a debug line
nixnax	142:54d1543e23e5	378	checkPc();
nixnax	142:54d1543e23e5	379	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	380	if(0) dumpPPPFrame(); // set to 1 to dump frames with errors in them
nixnax	142:54d1543e23e5	381	#endif
nixnax	142:54d1543e23e5	382	}
nixnax	142:54d1543e23e5	383	}
nixnax	142:54d1543e23e5	384
nixnax	142:54d1543e23e5	385	/// output a character to the PPP port while checking for incoming characters
nixnax	142:54d1543e23e5	386	void pcPutcWhileCheckingInput(int ch)
nixnax	142:54d1543e23e5	387	{
nixnax	142:54d1543e23e5	388	checkPc(); // check input
nixnax	142:54d1543e23e5	389	pc.putc(ch);
nixnax	142:54d1543e23e5	390	checkPc();
nixnax	142:54d1543e23e5	391	}
nixnax	142:54d1543e23e5	392
nixnax	142:54d1543e23e5	393	/// do PPP HDLC-like handling of special (flag) characters
nixnax	143:c5019f856a56	394	void hdlcPut(int ch)
nixnax	142:54d1543e23e5	395	{
nixnax	142:54d1543e23e5	396	if ( (ch<0x20) \|\| (ch==0x7d) \|\| (ch==0x7e) ) {
nixnax	142:54d1543e23e5	397	pcPutcWhileCheckingInput(0x7d);
nixnax	142:54d1543e23e5	398	pcPutcWhileCheckingInput(ch^0x20); // these characters need special handling
nixnax	142:54d1543e23e5	399	} else {
nixnax	142:54d1543e23e5	400	pcPutcWhileCheckingInput(ch);
nixnax	142:54d1543e23e5	401	}
nixnax	142:54d1543e23e5	402	}
nixnax	142:54d1543e23e5	403
nixnax	142:54d1543e23e5	404	/// send a PPP frame in HDLC format
nixnax	144:01d98cf7738e	405	void sendPppFrame()
nixnax	143:c5019f856a56	406	{
nixnax	145:098b6ed2f7f2	407	int crc = fcsBuf(ppp.pkt.buf, ppp.pkt.len-2); // update crc
nixnax	142:54d1543e23e5	408	ppp.pkt.buf[ ppp.pkt.len-2 ] = (~crc>>0); // fcs lo (crc)
nixnax	142:54d1543e23e5	409	ppp.pkt.buf[ ppp.pkt.len-1 ] = (~crc>>8); // fcs hi (crc)
nixnax	142:54d1543e23e5	410	pcPutcWhileCheckingInput(0x7e); // hdlc start-of-frame "flag"
nixnax	142:54d1543e23e5	411	for(int i=0; i<ppp.pkt.len; i++) {
nixnax	142:54d1543e23e5	412	wait_us(86); // wait one character time
nixnax	142:54d1543e23e5	413	checkPc();
nixnax	142:54d1543e23e5	414	hdlcPut( ppp.pkt.buf[i] ); // send a character
nixnax	142:54d1543e23e5	415	}
nixnax	142:54d1543e23e5	416	pcPutcWhileCheckingInput(0x7e); // hdlc end-of-frame "flag"
nixnax	142:54d1543e23e5	417	}
nixnax	142:54d1543e23e5	418
nixnax	143:c5019f856a56	419	/// 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	420	int bufferToIP(char * buffer)
nixnax	143:c5019f856a56	421	{
nixnax	143:c5019f856a56	422	int result=0;
nixnax	143:c5019f856a56	423	for(int i=0; i<4; i++) result = (result<<8)\|(*buffer++ & 0xff);
nixnax	143:c5019f856a56	424	return result;
nixnax	143:c5019f856a56	425	}
nixnax	143:c5019f856a56	426
nixnax	142:54d1543e23e5	427	/// handle IPCP configuration requests
nixnax	142:54d1543e23e5	428	void ipcpConfigRequestHandler()
nixnax	142:54d1543e23e5	429	{
nixnax	142:54d1543e23e5	430	debugPrintf("Their IPCP Config Req, Our Ack\n");
nixnax	143:c5019f856a56	431	if(ppp.pkt.buf[8]==3) {
nixnax	143:c5019f856a56	432	ppp.hostIP = bufferToIP(ppp.pkt.buf+10);
nixnax	143:c5019f856a56	433	debugPrintf("Host IP = %d.%d.%d.%d (%08x)\n", ppp.pkt.buf[10],ppp.pkt.buf[11],ppp.pkt.buf[12],ppp.pkt.buf[13],ppp.hostIP);
nixnax	143:c5019f856a56	434	}
nixnax	143:c5019f856a56	435
nixnax	142:54d1543e23e5	436	ppp.pkt.buf[4]=2; // change code to ack
nixnax	144:01d98cf7738e	437	sendPppFrame(); // acknowledge everything they ask for - assume it's IP addresses
nixnax	142:54d1543e23e5	438
nixnax	142:54d1543e23e5	439	debugPrintf("Our IPCP Ask (no options)\n");
nixnax	142:54d1543e23e5	440	ppp.pkt.buf[4]=1; // change code to request
nixnax	142:54d1543e23e5	441	ppp.pkt.buf[7]=4; // no options in this request
nixnax	142:54d1543e23e5	442	ppp.pkt.len=10; // no options in this request shortest ipcp packet possible (4 ppp + 4 ipcp + 2 crc)
nixnax	144:01d98cf7738e	443	sendPppFrame(); // send our request
nixnax	142:54d1543e23e5	444	}
nixnax	142:54d1543e23e5	445
nixnax	142:54d1543e23e5	446	/// handle IPCP acknowledge (do nothing)
nixnax	142:54d1543e23e5	447	void ipcpAckHandler()
nixnax	142:54d1543e23e5	448	{
nixnax	142:54d1543e23e5	449	debugPrintf("Their IPCP Grant\n");
nixnax	142:54d1543e23e5	450	}
nixnax	142:54d1543e23e5	451
nixnax	143:c5019f856a56	452	/// Handle IPCP NACK by sending our suggested IP address if there is an IP involved.
nixnax	143:c5019f856a56	453	/// 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	454	void ipcpNackHandler()
nixnax	142:54d1543e23e5	455	{
nixnax	146:a45f49a2b29c	456	debugPrintf("Their IPCP Nack\n");
nixnax	142:54d1543e23e5	457	if (ppp.pkt.buf[8]==3) { // check if the NACK contains an IP address parameter
nixnax	142:54d1543e23e5	458	ppp.pkt.buf[4]=1; // assume the NACK contains our "suggested" IP address
nixnax	144:01d98cf7738e	459	sendPppFrame(); // let's request this IP address as ours
nixnax	143:c5019f856a56	460	debugPrintf("Our IPCP ACK (received an IP)\n");
nixnax	146:a45f49a2b29c	461	} else { // if it's not an IP nack we ignore it
nixnax	146:a45f49a2b29c	462	debugPrintf("IPCP Nack Ignored\n");
nixnax	146:a45f49a2b29c	463	}
nixnax	142:54d1543e23e5	464	}
nixnax	142:54d1543e23e5	465
nixnax	142:54d1543e23e5	466	/// handle all other IPCP requests (by ignoring them)
nixnax	142:54d1543e23e5	467	void ipcpDefaultHandler()
nixnax	142:54d1543e23e5	468	{
nixnax	142:54d1543e23e5	469	debugPrintf("Their IPCP Other\n");
nixnax	142:54d1543e23e5	470	}
nixnax	142:54d1543e23e5	471
nixnax	142:54d1543e23e5	472	/// process an incoming IPCP packet
nixnax	142:54d1543e23e5	473	void IPCPframe()
nixnax	142:54d1543e23e5	474	{
nixnax	142:54d1543e23e5	475	int code = ppp.pkt.buf[4]; // packet type is here
nixnax	142:54d1543e23e5	476	switch (code) {
nixnax	142:54d1543e23e5	477	case 1:
nixnax	142:54d1543e23e5	478	ipcpConfigRequestHandler();
nixnax	142:54d1543e23e5	479	break;
nixnax	142:54d1543e23e5	480	case 2:
nixnax	142:54d1543e23e5	481	ipcpAckHandler();
nixnax	142:54d1543e23e5	482	break;
nixnax	142:54d1543e23e5	483	case 3:
nixnax	142:54d1543e23e5	484	ipcpNackHandler();
nixnax	142:54d1543e23e5	485	break;
nixnax	142:54d1543e23e5	486	default:
nixnax	142:54d1543e23e5	487	ipcpDefaultHandler();
nixnax	142:54d1543e23e5	488	}
nixnax	142:54d1543e23e5	489	}
nixnax	142:54d1543e23e5	490
nixnax	142:54d1543e23e5	491	/// perform a 16-bit checksum. if the byte count is odd, stuff in an extra zero byte.
nixnax	161:d59f778bc8ab	492	unsigned int dataCheckSum(char * ptr, int len, int restart)
nixnax	142:54d1543e23e5	493	{
nixnax	159:4d1bf96a59cd	494	unsigned int i,hi,lo;
nixnax	142:54d1543e23e5	495	unsigned char placeHolder;
nixnax	161:d59f778bc8ab	496	if (restart) ppp.sum=0;
nixnax	142:54d1543e23e5	497	if (len&1) {
nixnax	142:54d1543e23e5	498	placeHolder = ptr[len];
nixnax	142:54d1543e23e5	499	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	500	}
nixnax	142:54d1543e23e5	501	i=0;
nixnax	142:54d1543e23e5	502	while ( i<len ) {
nixnax	142:54d1543e23e5	503	checkPc();
nixnax	142:54d1543e23e5	504	hi = ptr[i++];
nixnax	142:54d1543e23e5	505	lo = ptr[i++];
nixnax	159:4d1bf96a59cd	506	ppp.sum = ppp.sum + ((hi<<8)\|lo);
nixnax	142:54d1543e23e5	507	}
nixnax	142:54d1543e23e5	508	if (len&1) {
nixnax	142:54d1543e23e5	509	ptr[len] = placeHolder; // restore the extra byte we made zero
nixnax	142:54d1543e23e5	510	}
nixnax	159:4d1bf96a59cd	511	ppp.sum = (ppp.sum & 0xffff) + (ppp.sum>>16);
nixnax	159:4d1bf96a59cd	512	ppp.sum = (ppp.sum & 0xffff) + (ppp.sum>>16); // sum one more time to catch any carry from the carry
nixnax	159:4d1bf96a59cd	513	return ~ppp.sum;
nixnax	142:54d1543e23e5	514	}
nixnax	142:54d1543e23e5	515
nixnax	142:54d1543e23e5	516	/// perform the checksum on an IP header
nixnax	146:a45f49a2b29c	517	void IpHeaderCheckSum()
nixnax	142:54d1543e23e5	518	{
nixnax	161:d59f778bc8ab	519	ppp.ip->checksumR=0; // zero the checsum in the IP header
nixnax	161:d59f778bc8ab	520	int len = 4 * ppp.ip->headerLength; // length of IP header in bytes
nixnax	161:d59f778bc8ab	521	unsigned int sum = dataCheckSum(ppp.ipStart,len,1);
nixnax	161:d59f778bc8ab	522	ppp.ip->checksumR = __REV16( sum ); // insert fresh checksum
nixnax	146:a45f49a2b29c	523	}
nixnax	146:a45f49a2b29c	524
nixnax	147:0f40005cbc5f	525	/// swap the IP source and destination addresses
nixnax	147:0f40005cbc5f	526	void swapIpAddresses()
nixnax	147:0f40005cbc5f	527	{
nixnax	162:594729c0e5c1	528	unsigned int tempHold;
nixnax	162:594729c0e5c1	529	tempHold = ppp.ip->srcAdrR; // tempHold <- source IP
nixnax	162:594729c0e5c1	530	ppp.ip->srcAdrR = ppp.ip->dstAdrR; // source <- dest
nixnax	162:594729c0e5c1	531	ppp.ip->dstAdrR = tempHold; // dest <- tempHold*/
nixnax	147:0f40005cbc5f	532	}
nixnax	147:0f40005cbc5f	533
nixnax	149:969d98f6fb88	534	/// swap the IP source and destination ports
nixnax	149:969d98f6fb88	535	void swapIpPorts()
nixnax	149:969d98f6fb88	536	{
nixnax	149:969d98f6fb88	537	int headerSizeIP = 4*(ppp.pkt.buf[4]&0xf); // calculate size of IP header
nixnax	149:969d98f6fb88	538	char * ipSrcPort = 4 + ppp.pkt.buf + headerSizeIP + 0; // ip source port location
nixnax	149:969d98f6fb88	539	char * ipDstPort = 4 + ppp.pkt.buf + headerSizeIP + 2; // ip destin port location
nixnax	149:969d98f6fb88	540	char tempHold[2];
nixnax	149:969d98f6fb88	541	memcpy(tempHold, ipSrcPort,2); // tempHold <- source
nixnax	149:969d98f6fb88	542	memcpy(ipSrcPort,ipDstPort,2); // source <- dest
nixnax	149:969d98f6fb88	543	memcpy(ipDstPort,tempHold, 2); // dest <- tempHold
nixnax	149:969d98f6fb88	544	}
nixnax	149:969d98f6fb88	545
nixnax	146:a45f49a2b29c	546	/// Process an incoming UDP packet.
nixnax	146:a45f49a2b29c	547	/// If the packet starts with the string "echo " or "test" we echo back a special packet
nixnax	146:a45f49a2b29c	548	void UDPpacket()
nixnax	146:a45f49a2b29c	549	{
nixnax	163:d1b4328e9f08	550	struct {
nixnax	163:d1b4328e9f08	551	unsigned int all; // length of entire ip packet
nixnax	163:d1b4328e9f08	552	unsigned int header; // length of ip header
nixnax	163:d1b4328e9f08	553	} ipLength;
nixnax	163:d1b4328e9f08	554
nixnax	163:d1b4328e9f08	555	struct {
nixnax	165:c47826d07e0d	556	unsigned int all; // length of entire udp packet
nixnax	163:d1b4328e9f08	557	unsigned int data; // length of udp data segment
nixnax	163:d1b4328e9f08	558	} udpLength;
nixnax	163:d1b4328e9f08	559
nixnax	163:d1b4328e9f08	560	ipLength.header = 4 * ppp.ip->headerLength; // length of ip header
nixnax	163:d1b4328e9f08	561	ppp.udpStart = ppp.ipStart + ipLength.header; // calculate start of udp header
nixnax	163:d1b4328e9f08	562	udpLength.all = __REV16( ppp.udp->lengthR ); //((udpLen[0]<<8) \| udpLen[1]); // size of udp packet
nixnax	163:d1b4328e9f08	563	udpLength.data = udpLength.all - 8; // size of udp data
nixnax	147:0f40005cbc5f	564
nixnax	146:a45f49a2b29c	565	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	163:d1b4328e9f08	566	char * srcIP = (char *)&ppp.ip->srcAdrR; //ipHeader+12; // IP source
nixnax	163:d1b4328e9f08	567	char * dstIP = (char *)&ppp.ip->dstAdrR; //ipHeader+16; // IP destination
nixnax	163:d1b4328e9f08	568
nixnax	163:d1b4328e9f08	569	unsigned int udpSrcPort = __REV16( ppp.udp->srcPortR ); //(udpSrcPort[0]<<8)\|udpSrcPort[1]; // integer of UDP source port
nixnax	163:d1b4328e9f08	570	unsigned int udpDstPort = __REV16( ppp.udp->dstPortR ); //(udpDstPort[0]<<8)\|udpDstPort[1]; // integer of UDP dest port
nixnax	163:d1b4328e9f08	571
nixnax	163:d1b4328e9f08	572	if(v0) {
nixnax	163:d1b4328e9f08	573	debugPrintf("UDP %d.%d.%d.%d:%d ", srcIP[0],srcIP[1],srcIP[2],srcIP[3],udpSrcPort);
nixnax	163:d1b4328e9f08	574	debugPrintf("%d.%d.%d.%d:%d ", dstIP[0],dstIP[1],dstIP[2],dstIP[3],udpDstPort);
nixnax	163:d1b4328e9f08	575	debugPrintf("Len %03d", udpLength);
nixnax	163:d1b4328e9f08	576	}
nixnax	146:a45f49a2b29c	577	if (v1) {
nixnax	163:d1b4328e9f08	578	int printSize = udpLength.data;
nixnax	146:a45f49a2b29c	579	if (printSize > 20) printSize = 20; // print only first 20 characters
nixnax	146:a45f49a2b29c	580	for (int i=0; i<printSize; i++) {
nixnax	163:d1b4328e9f08	581	char ch = ppp.udp->data[i];
nixnax	146:a45f49a2b29c	582	if (ch>31 && ch<127) {
nixnax	146:a45f49a2b29c	583	debugPrintf("%c", ch);
nixnax	146:a45f49a2b29c	584	} else {
nixnax	146:a45f49a2b29c	585	debugPrintf("_");
nixnax	146:a45f49a2b29c	586	}
nixnax	146:a45f49a2b29c	587	}
nixnax	146:a45f49a2b29c	588	}
nixnax	146:a45f49a2b29c	589	if (v0) debugPrintf("\n");
nixnax	146:a45f49a2b29c	590	#endif
nixnax	163:d1b4328e9f08	591	int echoFound = !strncmp(ppp.udp->data,"echo ",5); // true if UDP message starts with "echo "
nixnax	163:d1b4328e9f08	592	int testFound = !strncmp(ppp.udp->data,"test" ,4); // true if UDP message starts with "test"
nixnax	146:a45f49a2b29c	593	if ( (echoFound) \|\| (testFound)) { // if the UDP message starts with "echo " or "test" we answer back
nixnax	147:0f40005cbc5f	594	swapIpAddresses(); // swap IP source and destination
nixnax	149:969d98f6fb88	595	swapIpPorts(); // swap IP source and destination ports
nixnax	146:a45f49a2b29c	596	if (echoFound) {
nixnax	163:d1b4328e9f08	597	memcpy(ppp.udp->data,"Got{",4); // in the UDP data modify "echo" to "Got:"
nixnax	146:a45f49a2b29c	598	char endString[] = "} UDP Server: PPP-Blinky\n"; // an appendix
nixnax	163:d1b4328e9f08	599	memcpy(ppp.udp->data+udpLength.data,endString,sizeof(endString)-1); // add endstring size to the UDP message
nixnax	163:d1b4328e9f08	600	udpLength.all = udpLength.data + sizeof(endString)-1; // update udp data size with the size of the appendix
nixnax	146:a45f49a2b29c	601	}
nixnax	146:a45f49a2b29c	602	if (testFound) {
nixnax	146:a45f49a2b29c	603	char udpResponse[50];
nixnax	146:a45f49a2b29c	604	int n = 0;
nixnax	146:a45f49a2b29c	605	n = n+sprintf(udpResponse+n,"Response count %d\n",ppp.responseCounter++);
nixnax	163:d1b4328e9f08	606	memcpy(ppp.udp->data,udpResponse,n); // copy response to the UDP data area
nixnax	163:d1b4328e9f08	607	udpLength.data = n; // update udp data size
nixnax	146:a45f49a2b29c	608	}
nixnax	163:d1b4328e9f08	609	// we may have changed data length, update all the lengths
nixnax	163:d1b4328e9f08	610	udpLength.all = udpLength.data+8; // update local udp packet length
nixnax	163:d1b4328e9f08	611	ipLength.all = ipLength.header + udpLength.all; // update IP Length
nixnax	163:d1b4328e9f08	612	ppp.ip->lengthR = __REV16(ipLength.all); // update IP length in buffer
nixnax	163:d1b4328e9f08	613	ppp.udp->lengthR = __REV16(udpLength.all); // update UDP length in buffer
nixnax	163:d1b4328e9f08	614	ppp.pkt.len = ipLength.all+2+4; // update ppp packet length
nixnax	164:c3de3d212c4b	615
nixnax	163:d1b4328e9f08	616	IpHeaderCheckSum(); // refresh IP header checksum
nixnax	163:d1b4328e9f08	617	ppp.udp->checkSumR = 0; // we don't yet recompute the UDP checksum (it's optional), so have to zero it
nixnax	165:c47826d07e0d	618	ppp.responseCounter++; // count UDP packet as a response
nixnax	146:a45f49a2b29c	619	sendPppFrame(); // send the UDP message back
nixnax	165:c47826d07e0d	620	} else {
nixnax	165:c47826d07e0d	621	// do nothing with other incoming UDP packets
nixnax	146:a45f49a2b29c	622	}
nixnax	142:54d1543e23e5	623	}
nixnax	142:54d1543e23e5	624
nixnax	142:54d1543e23e5	625	/// handle a PING ICMP (internet control message protocol) packet
nixnax	142:54d1543e23e5	626	void ICMPpacket() // internet control message protocol
nixnax	142:54d1543e23e5	627	{
nixnax	165:c47826d07e0d	628	struct {
nixnax	165:c47826d07e0d	629	unsigned int all; // length of entire ip packet
nixnax	165:c47826d07e0d	630	unsigned int header; // length of ip header
nixnax	165:c47826d07e0d	631	} ipLength;
nixnax	165:c47826d07e0d	632	struct {
nixnax	165:c47826d07e0d	633	unsigned int all; // length of entire udp packet
nixnax	165:c47826d07e0d	634	unsigned int data; // length of udp data segment
nixnax	165:c47826d07e0d	635	} icmpLength;
nixnax	165:c47826d07e0d	636
nixnax	165:c47826d07e0d	637	ipLength.all = __REV16( ppp.ip->lengthR ); // length of ip packet
nixnax	165:c47826d07e0d	638	ipLength.header = 4 * ppp.ip->headerLength; // length of ip header
nixnax	165:c47826d07e0d	639	ppp.icmpStart = ppp.ipStart + ipLength.header; // calculate start of udp header
nixnax	165:c47826d07e0d	640	icmpLength.all = ipLength.all - ipLength.header; // length of icmp packet
nixnax	165:c47826d07e0d	641	icmpLength.data = icmpLength.all - 8; // length of icmp data
nixnax	165:c47826d07e0d	642
nixnax	142:54d1543e23e5	643	#define ICMP_TYPE_PING_REQUEST 8
nixnax	165:c47826d07e0d	644	if ( ppp.icmp->type == ICMP_TYPE_PING_REQUEST ) {
nixnax	165:c47826d07e0d	645	ppp.ip->ttl--; // decrement time to live (so we have to update header checksum)
nixnax	147:0f40005cbc5f	646	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	165:c47826d07e0d	647	char * srcAdr = (char *) &ppp.ip->srcAdrR;
nixnax	165:c47826d07e0d	648	char * dstAdr = (char *) &ppp.ip->dstAdrR;
nixnax	165:c47826d07e0d	649	int icmpIdent = __REV16( ppp.ip->identR ); // byte reversed - big endian
nixnax	165:c47826d07e0d	650	int icmpSequence = __REV16( ppp.icmp->sequenceR ); // byte reversed - big endian
nixnax	142:54d1543e23e5	651	if(1) {
nixnax	142:54d1543e23e5	652	char pbuf[50];
nixnax	142:54d1543e23e5	653	checkPc();
nixnax	142:54d1543e23e5	654	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	655	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	656	checkPc();
nixnax	142:54d1543e23e5	657	sprintf(pbuf, "Ident %04x Sequence %04d \n",icmpIdent,icmpSequence);
nixnax	142:54d1543e23e5	658	checkPc();
nixnax	142:54d1543e23e5	659	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	660	}
nixnax	142:54d1543e23e5	661	#endif
nixnax	147:0f40005cbc5f	662	swapIpAddresses(); // swap the IP source and destination addresses
nixnax	147:0f40005cbc5f	663	IpHeaderCheckSum(); // new ip header checksum (required because we changed TTL)
nixnax	142:54d1543e23e5	664	#define ICMP_TYPE_ECHO_REPLY 0
nixnax	165:c47826d07e0d	665	ppp.icmp->type = ICMP_TYPE_ECHO_REPLY; // icmp echo reply
nixnax	165:c47826d07e0d	666	ppp.icmp->checkSumR = 0; // zero the checksum for recalculation
nixnax	165:c47826d07e0d	667	unsigned int sum = dataCheckSum(ppp.icmpStart, icmpLength.all, 1); // icmp checksum
nixnax	165:c47826d07e0d	668	ppp.icmp->checkSumR = __REV16( sum ); // save big-endian icmp checksum
nixnax	142:54d1543e23e5	669
nixnax	165:c47826d07e0d	670	int printSize = icmpLength.data; // exclude size of icmp header
nixnax	142:54d1543e23e5	671	if (printSize > 10) printSize = 10; // print up to 20 characters
nixnax	142:54d1543e23e5	672	if (0) {
nixnax	142:54d1543e23e5	673	for (int i=0; i<printSize; i++) {
nixnax	165:c47826d07e0d	674	char ch = ppp.icmp->data[i];
nixnax	142:54d1543e23e5	675	if (ch>31 && ch<127) {
nixnax	142:54d1543e23e5	676	putcWhileCheckingInput(ch);
nixnax	142:54d1543e23e5	677	} else {
nixnax	142:54d1543e23e5	678	putcWhileCheckingInput('_');
nixnax	142:54d1543e23e5	679	}
nixnax	142:54d1543e23e5	680	}
nixnax	142:54d1543e23e5	681	putcWhileCheckingInput('\n');
nixnax	142:54d1543e23e5	682	}
nixnax	165:c47826d07e0d	683	ppp.responseCounter++; // count a ping as a response
nixnax	144:01d98cf7738e	684	sendPppFrame(); // reply to the ping
nixnax	142:54d1543e23e5	685	} else {
nixnax	142:54d1543e23e5	686	if (v0) {
nixnax	165:c47826d07e0d	687	debugPrintf("ICMP type=%x \n", ppp.icmp->type);
nixnax	142:54d1543e23e5	688	}
nixnax	142:54d1543e23e5	689	}
nixnax	142:54d1543e23e5	690	}
nixnax	142:54d1543e23e5	691
nixnax	142:54d1543e23e5	692	/// handle an IGMP (internet group managment protocol) packet (by ignoring it)
nixnax	142:54d1543e23e5	693	void IGMPpacket()
nixnax	142:54d1543e23e5	694	{
nixnax	142:54d1543e23e5	695	if (v0) debugPrintf("IGMP type=%d \n", ppp.pkt.buf[28]);
nixnax	142:54d1543e23e5	696	}
nixnax	142:54d1543e23e5	697
nixnax	142:54d1543e23e5	698	/// dump the header of an IP pakcet on the (optional) debug serial port
nixnax	142:54d1543e23e5	699	void dumpHeaderIP (int outGoing)
nixnax	142:54d1543e23e5	700	{
nixnax	142:54d1543e23e5	701	#if defined(IP_HEADER_DUMP_YES) && defined(SERIAL_PORT_MONITOR_YES)
nixnax	142:54d1543e23e5	702	checkPc(); // we are expecting the first character of the next packet
nixnax	155:9c6a1d249e26	703	int IPv4Id = __REV16(ppp.ip->identR);
nixnax	152:025c73b6c0a9	704	char pbuf[80]; // local print buffer
nixnax	142:54d1543e23e5	705	int n=0;
nixnax	142:54d1543e23e5	706	n=n+sprintf(pbuf+n, outGoing ? "\x1b[34m" : "\x1b[30m" ); // VT100 color code, print black for incoming, blue for outgoing headers
nixnax	142:54d1543e23e5	707	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	708	#define DUMP_FULL_IP_ADDRESS_YES
nixnax	142:54d1543e23e5	709	#ifdef DUMP_FULL_IP_ADDRESS_YES
nixnax	163:d1b4328e9f08	710	char * srcAdr = (char *)&ppp.ip->srcAdrR;
nixnax	163:d1b4328e9f08	711	char * dstAdr = (char *)&ppp.ip->dstAdrR;
nixnax	142:54d1543e23e5	712	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	713	#endif
nixnax	142:54d1543e23e5	714	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	715	#ifndef TCP_HEADER_DUMP_YES
nixnax	160:bd701ad564cb	716	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	717	#endif
nixnax	142:54d1543e23e5	718	#endif
nixnax	142:54d1543e23e5	719	}
nixnax	142:54d1543e23e5	720
nixnax	142:54d1543e23e5	721	/// dump a TCP header on the optional debug serial port
nixnax	142:54d1543e23e5	722	void dumpHeaderTCP(int outGoing)
nixnax	142:54d1543e23e5	723	{
nixnax	142:54d1543e23e5	724	#if defined(TCP_HEADER_DUMP_YES) && defined(SERIAL_PORT_MONITOR_YES)
nixnax	155:9c6a1d249e26	725	char flagString[9]; // text string presenting the 8 most important TCP flags
nixnax	142:54d1543e23e5	726	#define PRINT_ALL_TCP_FLAGS_YES
nixnax	142:54d1543e23e5	727	#ifdef PRINT_ALL_TCP_FLAGS_YES
nixnax	155:9c6a1d249e26	728	memset(flagString,'.', 8); // fill string with "........"
nixnax	156:163c23249731	729	if (ppp.tcp->flag.fin) flagString[7]='F';
nixnax	156:163c23249731	730	if (ppp.tcp->flag.syn) flagString[6]='S';
nixnax	156:163c23249731	731	if (ppp.tcp->flag.rst) flagString[5]='R';
nixnax	156:163c23249731	732	if (ppp.tcp->flag.psh) flagString[4]='P';
nixnax	156:163c23249731	733	if (ppp.tcp->flag.ack) flagString[3]='A';
nixnax	156:163c23249731	734	if (ppp.tcp->flag.urg) flagString[2]='U';
nixnax	156:163c23249731	735	if (ppp.tcp->flag.ece) flagString[1]='E';
nixnax	156:163c23249731	736	if (ppp.tcp->flag.cwr) flagString[0]='C';
nixnax	155:9c6a1d249e26	737	flagString[8]=0; // null terminate string
nixnax	142:54d1543e23e5	738	#else
nixnax	156:163c23249731	739	if (ppp.tcp->flag.ack) flagString[0]='A'; // choose only the most important flag to print
nixnax	156:163c23249731	740	if (ppp.tcp->flag.syn) flagString[0]='S';
nixnax	156:163c23249731	741	if (ppp.tcp->flag.fin) flagString[0]='F';
nixnax	156:163c23249731	742	if (ppp.tcp->flag.psh) flagString[0]='P';
nixnax	156:163c23249731	743	if (ppp.tcp->flag.rst) flagString[0]='R';
nixnax	155:9c6a1d249e26	744	flagString[1]=0; // null terminate string
nixnax	142:54d1543e23e5	745	#endif
nixnax	155:9c6a1d249e26	746	putsWhileCheckingInput( flagString );
nixnax	142:54d1543e23e5	747	#define EVERY_PACKET_ON_A_NEW_LINE_YES
nixnax	142:54d1543e23e5	748	#ifdef EVERY_PACKET_ON_A_NEW_LINE_YES
nixnax	142:54d1543e23e5	749	putsWhileCheckingInput("\x1b[30m\n"); // write a black color and newline after every packet
nixnax	160:bd701ad564cb	750	#else
nixnax	160:bd701ad564cb	751	putsWhileCheckingInput("\x1b[30m"); // write a black color after every packet
nixnax	142:54d1543e23e5	752	#endif
nixnax	156:163c23249731	753	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	754	putcWhileCheckingInput('\n'); // insert an extra new line to mark the end (except for final ack) of an HTTP conversation
nixnax	142:54d1543e23e5	755	}
nixnax	142:54d1543e23e5	756	#endif
nixnax	142:54d1543e23e5	757	}
nixnax	142:54d1543e23e5	758
nixnax	143:c5019f856a56	759	/// Encode a buffer in base-64
nixnax	142:54d1543e23e5	760	void enc64(char * in, char * out, int len)
nixnax	142:54d1543e23e5	761	{
nixnax	142:54d1543e23e5	762	const static char lut [] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
nixnax	142:54d1543e23e5	763	int i,j,a,b,c;
nixnax	142:54d1543e23e5	764	i=0;
nixnax	142:54d1543e23e5	765	j=0;
nixnax	142:54d1543e23e5	766	while(1) {
nixnax	142:54d1543e23e5	767	if (i<len) {
nixnax	142:54d1543e23e5	768	a = in[i++];
nixnax	142:54d1543e23e5	769	out[j++] = lut[ ( (a >> 2) & 0x3f) ];
nixnax	142:54d1543e23e5	770	} else break;
nixnax	142:54d1543e23e5	771	if (i<len) {
nixnax	142:54d1543e23e5	772	b = in[i++];
nixnax	142:54d1543e23e5	773	out[j++] = lut[ ( (a << 4) & 0x30) \| ( (b >> 4) & 0x0f) ];
nixnax	142:54d1543e23e5	774	out[j++] = lut[ ( (b << 2) & 0x3c) ];
nixnax	142:54d1543e23e5	775	} else out[j++] = '=';
nixnax	142:54d1543e23e5	776	if (i<len) {
nixnax	142:54d1543e23e5	777	c = in[i++];
nixnax	142:54d1543e23e5	778	j--;
nixnax	142:54d1543e23e5	779	out[j++] = lut[ ( (b << 2) & 0x3c) \| ( (c >> 6) & 0x03) ];
nixnax	142:54d1543e23e5	780	out[j++] = lut[ ( (c >> 0) & 0x3f) ];
nixnax	142:54d1543e23e5	781	} else out[j++] = '=';
nixnax	142:54d1543e23e5	782	}
nixnax	142:54d1543e23e5	783	out[j]=0;
nixnax	142:54d1543e23e5	784	}
nixnax	142:54d1543e23e5	785
nixnax	160:bd701ad564cb	786	/// Handle a request for an http websocket.
nixnax	160:bd701ad564cb	787	/// 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	788	int webSocketHandler(char * dataStart)
nixnax	142:54d1543e23e5	789	{
nixnax	142:54d1543e23e5	790	int n=0; // byte counter
nixnax	142:54d1543e23e5	791	char * key = strstr(dataStart, "Sec-WebSocket-Key: "); // search for the key in the payload
nixnax	142:54d1543e23e5	792	if (key != NULL) {
nixnax	142:54d1543e23e5	793	if (v0) putsWhileCheckingInput("WebSocket Request\n");
nixnax	142:54d1543e23e5	794	char challenge [70];
nixnax	142:54d1543e23e5	795	strncpy(challenge,key+19,70); // a local buffer
nixnax	142:54d1543e23e5	796	*strchr(challenge,'\r')=0; // insert null so we can use sprintf
nixnax	142:54d1543e23e5	797	strncat(challenge,"258EAFA5-E914-47DA-95CA-C5AB0DC85B11",70); // append websocket gui code
nixnax	142:54d1543e23e5	798	char shaOutput [20]; // sha1 output
nixnax	142:54d1543e23e5	799	sha1( shaOutput, challenge, strlen(challenge));
nixnax	142:54d1543e23e5	800	char encOut[50];
nixnax	142:54d1543e23e5	801	enc64( shaOutput, encOut, 20);
nixnax	142:54d1543e23e5	802	char * versionstring = strstr(dataStart, "Sec-WebSocket-Version:");
nixnax	142:54d1543e23e5	803	char * version = challenge;
nixnax	142:54d1543e23e5	804	strncpy(version, versionstring,70); // copy version string
nixnax	142:54d1543e23e5	805	*strchr(version,'\r')=0; // null terminate so we can sprintf it
nixnax	142:54d1543e23e5	806	memset(dataStart,0,500); // blank out old data befor send the websocket response header
nixnax	142:54d1543e23e5	807	n=n+sprintf(dataStart+n, "HTTP/1.1 101 Switching Protocols\r\n");
nixnax	142:54d1543e23e5	808	n=n+sprintf(dataStart+n, "Upgrade: websocket\r\n");
nixnax	142:54d1543e23e5	809	n=n+sprintf(dataStart+n, "Connection: Upgrade\r\n");
nixnax	142:54d1543e23e5	810	n=n+sprintf(dataStart+n, "Sec-WebSocket-Accept: %s\r\n",encOut);
nixnax	142:54d1543e23e5	811	n=n+sprintf(dataStart+n, "%s\r\n",version);
nixnax	142:54d1543e23e5	812	n=n+sprintf(dataStart+n, "mbed-Code: PPP-Blinky\r\n");
nixnax	142:54d1543e23e5	813	n=n+sprintf(dataStart+n, "\r\n"); // websocket response header ending
nixnax	142:54d1543e23e5	814	}
nixnax	142:54d1543e23e5	815	return n; // this response should satisfy a web browser's websocket protocol request
nixnax	142:54d1543e23e5	816	}
nixnax	142:54d1543e23e5	817
nixnax	142:54d1543e23e5	818	#define TCP_FLAG_ACK (1<<4)
nixnax	142:54d1543e23e5	819	#define TCP_FLAG_SYN (1<<1)
nixnax	142:54d1543e23e5	820	#define TCP_FLAG_PSH (1<<3)
nixnax	142:54d1543e23e5	821	#define TCP_FLAG_RST (1<<2)
nixnax	142:54d1543e23e5	822	#define TCP_FLAG_FIN (1<<0)
nixnax	142:54d1543e23e5	823
nixnax	142:54d1543e23e5	824	/// respond to an HTTP request
nixnax	142:54d1543e23e5	825	int httpResponse(char * dataStart)
nixnax	142:54d1543e23e5	826	{
nixnax	142:54d1543e23e5	827	int n=0; // number of bytes we have printed so far
nixnax	142:54d1543e23e5	828	n = webSocketHandler( dataStart ); // test for and handle WebSocket upgrade requests
nixnax	160:bd701ad564cb	829	if (n>0) return n; // if n>0 we already have a response, so return
nixnax	142:54d1543e23e5	830
nixnax	142:54d1543e23e5	831	int nHeader; // byte size of HTTP header
nixnax	142:54d1543e23e5	832	int contentLengthStart; // index where HTML starts
nixnax	142:54d1543e23e5	833	int httpGet5,httpGet6,httpGetx, httpGetRoot; // temporary storage of strncmp results
nixnax	142:54d1543e23e5	834
nixnax	146:a45f49a2b29c	835	ppp.responseCounter++; // increment the number of frames we have made
nixnax	142:54d1543e23e5	836
nixnax	142:54d1543e23e5	837	httpGetRoot = strncmp(dataStart, "GET / HTTP/1.", 13); // found a GET to the root directory
nixnax	142:54d1543e23e5	838	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	839	httpGet5 = dataStart[5]; // the first character in the path name, we use it for special functions later on
nixnax	142:54d1543e23e5	840	httpGet6 = dataStart[6]; // the second character in the path name, we use it for special functions later on
nixnax	142:54d1543e23e5	841	// for example, you could try this using netcat (nc): echo "GET /x" \| nc 172.10.10.2
nixnax	142:54d1543e23e5	842	if( (httpGetRoot==0) \|\| (httpGetx==0) ) {
nixnax	142:54d1543e23e5	843	n=n+sprintf(n+dataStart,"HTTP/1.1 200 OK\r\nServer: mbed-PPP-Blinky-v1\r\n"); // 200 OK header
nixnax	142:54d1543e23e5	844	} else {
nixnax	142:54d1543e23e5	845	n=n+sprintf(n+dataStart,"HTTP/1.1 404 Not Found\r\nServer: mbed-PPP-Blinky\r\n"); // 404 header
nixnax	142:54d1543e23e5	846	}
nixnax	142:54d1543e23e5	847	n=n+sprintf(n+dataStart,"Content-Length: "); // http header
nixnax	142:54d1543e23e5	848	contentLengthStart = n; // remember where Content-Length is in buffer
nixnax	142:54d1543e23e5	849	n=n+sprintf(n+dataStart,"?????\r\n"); // leave five spaces for content length - will be updated later
nixnax	142:54d1543e23e5	850	n=n+sprintf(n+dataStart,"Connection: close\r\n"); // close connection immediately
nixnax	142:54d1543e23e5	851	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	852	nHeader=n; // size of HTTP header
nixnax	142:54d1543e23e5	853	if( httpGetRoot == 0 ) {
nixnax	142:54d1543e23e5	854	// this is where we insert our web page into the buffer
nixnax	142:54d1543e23e5	855	memcpy(n+dataStart,rootWebPage,sizeof(rootWebPage));
nixnax	142:54d1543e23e5	856	n = n + sizeof(rootWebPage)-1; // one less than sizeof because we don't count the null byte at the end
nixnax	142:54d1543e23e5	857	} else if ( (httpGet5 == 'w') && (httpGet6 == 's') ) { // "ws" is a special page for websocket demo
nixnax	142:54d1543e23e5	858	memcpy(n+dataStart,webSocketPage,sizeof(webSocketPage));
nixnax	142:54d1543e23e5	859	n = n + sizeof(webSocketPage)-1; // one less than size
nixnax	142:54d1543e23e5	860	} else {
nixnax	142:54d1543e23e5	861	if (httpGetx == 0) { // the page request started with "GET /x" - here we treat anything starting with /x special:
nixnax	142:54d1543e23e5	862
nixnax	142:54d1543e23e5	863	#define W3C_COMPLIANT_RESPONSE_NO
nixnax	142:54d1543e23e5	864	// change the above to W3C_COMPLIANT_RESPONSE_YES if you want a W3C.org compliant HTTP response
nixnax	142:54d1543e23e5	865	#ifdef W3C_COMPLIANT_RESPONSE_YES
nixnax	142:54d1543e23e5	866	n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (W3C.org required elements)
nixnax	146:a45f49a2b29c	867	n=n+sprintf(n+dataStart,"<body>%d</body>",ppp.responseCounter); // body = the http frame count
nixnax	142:54d1543e23e5	868	#else
nixnax	142:54d1543e23e5	869	if( httpGet6 == 'b' ) { // if the fetched page is "xb" send a meta command to let the browser continuously reload
nixnax	165:c47826d07e0d	870	n=n+sprintf(n+dataStart, "<title>%d</title><meta http-equiv=\"refresh\" content=\"0\">",ppp.responseCounter); // reload loop - handy for benchmarking
nixnax	142:54d1543e23e5	871	}
nixnax	142:54d1543e23e5	872	// /x is a very short page, in fact, it is only a decimal number showing the http Page count
nixnax	146:a45f49a2b29c	873	n=n+sprintf(n+dataStart,"%d ",ppp.responseCounter); // not really valid html but most browsers and curl are ok with it
nixnax	142:54d1543e23e5	874	#endif
nixnax	142:54d1543e23e5	875	} else {
nixnax	142:54d1543e23e5	876	// all other requests get 404 Not Found response with a http frame count - nice for debugging
nixnax	142:54d1543e23e5	877	n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (required element)
nixnax	142:54d1543e23e5	878	n=n+sprintf(n+dataStart,"<body>Not Found</body>"); // not found message
nixnax	142:54d1543e23e5	879	}
nixnax	142:54d1543e23e5	880	}
nixnax	142:54d1543e23e5	881	#define CONTENTLENGTHSIZE 5
nixnax	142:54d1543e23e5	882	char contentLengthString[CONTENTLENGTHSIZE+1];
nixnax	142:54d1543e23e5	883	snprintf(contentLengthString,CONTENTLENGTHSIZE+1,"%*d",CONTENTLENGTHSIZE,n-nHeader); // print Content-Length with leading spaces and fixed width equal to csize
nixnax	142:54d1543e23e5	884	memcpy(dataStart+contentLengthStart, contentLengthString, CONTENTLENGTHSIZE); // copy Content-Length to it's place in the send buffer
nixnax	142:54d1543e23e5	885	return n; // total byte size of our response
nixnax	142:54d1543e23e5	886	}
nixnax	142:54d1543e23e5	887
nixnax	160:bd701ad564cb	888	/// Handle TCP data that is not an HTTP GET.
nixnax	160:bd701ad564cb	889	/// This is handy when for example you want to use netcat (nc.exe) to talk to PPP-Blinky.
nixnax	160:bd701ad564cb	890	/// This could also be a websocket receive event - especially if the first byte is 0x81 (websocket data push)
nixnax	142:54d1543e23e5	891	int tcpResponse(char * dataStart, int len, int * outFlags)
nixnax	142:54d1543e23e5	892	{
nixnax	142:54d1543e23e5	893	int n=0; // number of bytes we have printed so far
nixnax	142:54d1543e23e5	894	if (dataStart[0] == 0x81) { // check if this is a websocket push message
nixnax	160:bd701ad564cb	895	char mask [4];
nixnax	160:bd701ad564cb	896	memcpy ( mask, dataStart+2, 4); // websocket messages are "masked", so first we obtain the 4-byte mask
nixnax	160:bd701ad564cb	897	int websocketMessageSize = len - 6; // 1 byte prefix (0x81), 1 byte, 4 bytes mask = 6 bytes
nixnax	160:bd701ad564cb	898	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	899	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	900	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	901	memcpy(dataStart+2, "Got:",4); // insert our own text into the four mask bytes
nixnax	160:bd701ad564cb	902	n = len; // our response size remains exactly the same length as what we received
nixnax	142:54d1543e23e5	903	} else if ( (dataStart[0]==0x88) && (dataStart[1]==0x80) && (len == 6) ) { // test for a websocket close request
nixnax	142:54d1543e23e5	904	n=2; // our close command is only two bytes long because we don't use the four mask bytes
nixnax	142:54d1543e23e5	905	dataStart[1]=0; // we don't have mask bytes on
nixnax	160:bd701ad564cb	906	} else {
nixnax	160:bd701ad564cb	907	if (v1) putsWhileCheckingInput("TCP data received\n"); // all other tcp push packets
nixnax	163:d1b4328e9f08	908	}
nixnax	142:54d1543e23e5	909	return n; // total byte size of our response
nixnax	142:54d1543e23e5	910	}
nixnax	142:54d1543e23e5	911
nixnax	142:54d1543e23e5	912	/// handle an incoming TCP packet
nixnax	142:54d1543e23e5	913	/// 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	914	void tcpHandler()
nixnax	142:54d1543e23e5	915	{
nixnax	142:54d1543e23e5	916	// IP header
nixnax	154:18b2bd92f557	917	int packetLengthIp = __REV16(ppp.ip->lengthR ); // size of ip packet
nixnax	154:18b2bd92f557	918	int headerSizeIp = 4 * ppp.ip->headerLength; // size of ip header
nixnax	142:54d1543e23e5	919
nixnax	142:54d1543e23e5	920	// TCP header
nixnax	160:bd701ad564cb	921
nixnax	155:9c6a1d249e26	922	ppp.tcpStart = ppp.ipStart + headerSizeIp; // calculate where the TCP header starts
nixnax	154:18b2bd92f557	923	int tcpSize = packetLengthIp - headerSizeIp; // tcp size = size of ip payload
nixnax	160:bd701ad564cb	924	char * tcp = ppp.ipStart+headerSizeIp; // calculate start of tcp packet
nixnax	142:54d1543e23e5	925
nixnax	154:18b2bd92f557	926	int headerSizeTcp = 4 * (ppp.tcp->offset); // tcp "offset" for start of data is also the header size
nixnax	152:025c73b6c0a9	927
nixnax	154:18b2bd92f557	928	char * tcpDataIn = tcp + headerSizeTcp; // start of data block after TCP header
nixnax	154:18b2bd92f557	929	int tcpDataSize = tcpSize - headerSizeTcp; // size of data block after TCP header
nixnax	154:18b2bd92f557	930
nixnax	154:18b2bd92f557	931	unsigned int seq_in = __REV(ppp.tcp->seqTcpR);
nixnax	154:18b2bd92f557	932	unsigned int ack_in = __REV(ppp.tcp->ackTcpR);
nixnax	142:54d1543e23e5	933	unsigned int ack_out = seq_in + tcpDataSize;
nixnax	142:54d1543e23e5	934	unsigned int seq_out = ack_in; // use their version of our current sequence number
nixnax	142:54d1543e23e5	935
nixnax	142:54d1543e23e5	936	// first we shorten the TCP response header to only 20 bytes. This means we ignore all TCP option requests
nixnax	142:54d1543e23e5	937	tcpSize = 20; // shorten total TCP packet size to 20 bytes (no data)
nixnax	154:18b2bd92f557	938	headerSizeTcp = 20; // shorten outgoing TCP header size 20 bytes
nixnax	154:18b2bd92f557	939	ppp.ip->headerLength = 5; // ip header is 20 bytes long
nixnax	154:18b2bd92f557	940	ppp.tcp->offset = (headerSizeTcp/4);
nixnax	154:18b2bd92f557	941	ppp.ip->lengthR = __REV(40);
nixnax	154:18b2bd92f557	942	char * tcpDataOut = tcp + 20; // start of outgoing data
nixnax	154:18b2bd92f557	943
nixnax	154:18b2bd92f557	944	ppp.ip->lengthR = __REV16(40);
nixnax	142:54d1543e23e5	945
nixnax	142:54d1543e23e5	946	int dataLen = 0; // most of our responses will have zero TCP data, only a header
nixnax	142:54d1543e23e5	947	int flagsOut = TCP_FLAG_ACK; // the default case is an ACK packet
nixnax	155:9c6a1d249e26	948	//int flagsTCP = ((flagbitstcp[0]&1)<<8)\|flagbitstcp[1]; // the tcp flags we received
nixnax	160:bd701ad564cb	949
nixnax	159:4d1bf96a59cd	950	ppp.tcp->windowR = __REV16( 700 ); // set tcp window size to 700 bytes
nixnax	142:54d1543e23e5	951
nixnax	142:54d1543e23e5	952	// A sparse TCP flag interpreter that implements stateless TCP connections
nixnax	142:54d1543e23e5	953
nixnax	156:163c23249731	954	switch ( ppp.tcp->flag.All ) {
nixnax	158:841592aed956	955	case TCP_FLAG_ACK: // handle ack messages by ignoring them
nixnax	142:54d1543e23e5	956	return;
nixnax	142:54d1543e23e5	957	case TCP_FLAG_SYN:
nixnax	142:54d1543e23e5	958	flagsOut = TCP_FLAG_SYN \| TCP_FLAG_ACK; // something wants to connect - acknowledge it
nixnax	142:54d1543e23e5	959	seq_out = seq_in+0x10000000U; // create a new sequence number using their sequence as a starting point, increase the highest digit
nixnax	142:54d1543e23e5	960	ack_out++; // for SYN flag we have to increase the sequence by 1
nixnax	142:54d1543e23e5	961	break;
nixnax	142:54d1543e23e5	962	case TCP_FLAG_ACK \| TCP_FLAG_PSH:
nixnax	142:54d1543e23e5	963	if ( (strncmp(tcpDataIn, "GET /", 5) == 0) ) { // check for an http GET command
nixnax	142:54d1543e23e5	964	flagsOut = TCP_FLAG_ACK \| TCP_FLAG_PSH; // set outgoing FIN flag to ask them to close from their side
nixnax	142:54d1543e23e5	965	dataLen = httpResponse(tcpDataOut); // send an http response
nixnax	142:54d1543e23e5	966	} else {
nixnax	158:841592aed956	967	dataLen = tcpResponse(tcpDataOut,tcpDataSize, &flagsOut); // not an http GET, handle as a tcp connection
nixnax	142:54d1543e23e5	968	}
nixnax	142:54d1543e23e5	969	break;
nixnax	142:54d1543e23e5	970	case TCP_FLAG_FIN:
nixnax	142:54d1543e23e5	971	case TCP_FLAG_FIN \| TCP_FLAG_ACK:
nixnax	142:54d1543e23e5	972	case TCP_FLAG_FIN \| TCP_FLAG_PSH \| TCP_FLAG_ACK:
nixnax	142:54d1543e23e5	973	flagsOut = TCP_FLAG_ACK \| TCP_FLAG_FIN; // set outgoing FIN flag to ask them to close from their side
nixnax	142:54d1543e23e5	974	ack_out++; // for FIN flag we have to increase the sequence by 1
nixnax	142:54d1543e23e5	975	break;
nixnax	142:54d1543e23e5	976	default:
nixnax	142:54d1543e23e5	977	return; // ignore remaining packets
nixnax	142:54d1543e23e5	978	} // switch
nixnax	142:54d1543e23e5	979
nixnax	142:54d1543e23e5	980	// The TCP flag handling is now done
nixnax	142:54d1543e23e5	981	// first we swap source and destination TCP addresses and insert the new ack and seq numbers
nixnax	147:0f40005cbc5f	982	swapIpAddresses(); // swap IP source and destination addresses
nixnax	149:969d98f6fb88	983	swapIpPorts(); // swap IP source and destination ports
nixnax	142:54d1543e23e5	984
nixnax	158:841592aed956	985	ppp.tcp->ackTcpR = __REV( ack_out ); // byte reversed - tcp/ip messages are big-endian (high byte first)
nixnax	158:841592aed956	986	ppp.tcp->seqTcpR = __REV( seq_out ); // byte reversed - tcp/ip messages are big-endian (high byte first)
nixnax	160:bd701ad564cb	987
nixnax	156:163c23249731	988	ppp.tcp->flag.All = flagsOut; // update the TCP flags
nixnax	142:54d1543e23e5	989
nixnax	159:4d1bf96a59cd	990	// recalculate all the header sizes
nixnax	154:18b2bd92f557	991	tcpSize = headerSizeTcp + dataLen; // tcp packet size
nixnax	154:18b2bd92f557	992	int newPacketSize = headerSizeIp + tcpSize; // calculate size of the outgoing packet
nixnax	159:4d1bf96a59cd	993	ppp.ip->lengthR = __REV16 ( newPacketSize );
nixnax	142:54d1543e23e5	994	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	995
nixnax	142:54d1543e23e5	996	// the header is all set up, now do the IP and TCP checksums
nixnax	146:a45f49a2b29c	997	IpHeaderCheckSum(); // calculate new IP header checksum
nixnax	142:54d1543e23e5	998
nixnax	159:4d1bf96a59cd	999	// create the TCP "pseudo-header" (containing some IP header values) in order to correctly calculate the TCP checksum
nixnax	142:54d1543e23e5	1000	// this header contains the most important parts of the IP header, i.e. source and destination address, protocol number and data length.
nixnax	159:4d1bf96a59cd	1001	pseudoIpHeaderType pseudoHeader; // create pseudo header
nixnax	159:4d1bf96a59cd	1002	pseudoHeader.srcAdrR = ppp.ip->srcAdrR; // copy in ip source address
nixnax	159:4d1bf96a59cd	1003	pseudoHeader.dstAdrR = ppp.ip->dstAdrR; // copy in ip dest address
nixnax	159:4d1bf96a59cd	1004	pseudoHeader.zero = 0; // padding
nixnax	160:bd701ad564cb	1005	pseudoHeader.protocol = ppp.ip->protocol; // protocol number
nixnax	159:4d1bf96a59cd	1006	pseudoHeader.lengthR = __REV16( tcpSize ); // size of tcp packet
nixnax	159:4d1bf96a59cd	1007	dataCheckSum(pseudoHeader.start, 12, 1); // start with the TCP checksum of the pseudoheader
nixnax	159:4d1bf96a59cd	1008	ppp.tcp->checksumR = 0; // before TCP checksum calculations the checksum bytes must be set cleared
nixnax	161:d59f778bc8ab	1009	unsigned int pseudoHeaderSum=dataCheckSum(ppp.tcpStart,tcpSize, 0); // continue the TCP checksum on the whole TCP packet
nixnax	159:4d1bf96a59cd	1010	ppp.tcp->checksumR = __REV16( pseudoHeaderSum); // tcp checksum done, store it in the TCP header
nixnax	160:bd701ad564cb	1011
nixnax	142:54d1543e23e5	1012	dumpHeaderIP(1); // dump outgoing IP header
nixnax	142:54d1543e23e5	1013	dumpHeaderTCP(1); // dump outgoing TCP header
nixnax	142:54d1543e23e5	1014	for (int i=0; i<45*1000/10; i++) { // 45 ms delay before sending frame - a typical internet delay time
nixnax	142:54d1543e23e5	1015	checkPc(); // catch any incoming characters
nixnax	142:54d1543e23e5	1016	wait_us(10); // wait less than 1 character duration at 115200
nixnax	142:54d1543e23e5	1017	}
nixnax	144:01d98cf7738e	1018	sendPppFrame(); // All preparation complete - send the TCP response
nixnax	142:54d1543e23e5	1019	if(0) dumpPPPFrame(); // set to 1 to dump transmitted ppp frame
nixnax	142:54d1543e23e5	1020	memset(ppp.pkt.buf+44,0,500); // flush out traces of previous data that we may scan for
nixnax	142:54d1543e23e5	1021	}
nixnax	142:54d1543e23e5	1022
nixnax	142:54d1543e23e5	1023	/// dump the TCP data to the debug serial port
nixnax	142:54d1543e23e5	1024	void dumpDataTCP()
nixnax	142:54d1543e23e5	1025	{
nixnax	142:54d1543e23e5	1026	int ipPktLen = (ppp.pkt.buf[6]<<8)\|ppp.pkt.buf[7]; // overall length of ip packet
nixnax	142:54d1543e23e5	1027	int ipHeaderLen = (ppp.pkt.buf[4]&0xf)*4; // length of ip header
nixnax	154:18b2bd92f557	1028	int headerSizeTcp = ((ppp.pkt.buf[4+ipHeaderLen+12]>>4)&0xf)*4;; // length of tcp header
nixnax	154:18b2bd92f557	1029	int dataLen = ipPktLen - ipHeaderLen - headerSizeTcp; // data is what's left after the two headers
nixnax	142:54d1543e23e5	1030	if (v1) {
nixnax	142:54d1543e23e5	1031	char pbuf[50]; // local print buffer
nixnax	142:54d1543e23e5	1032	checkPc();
nixnax	154:18b2bd92f557	1033	sprintf(pbuf, "TCP %d ipHeader %d tcpHeader %d Data %d\n", ipPktLen, ipHeaderLen, headerSizeTcp, dataLen); // 1 for more verbose
nixnax	142:54d1543e23e5	1034	checkPc();
nixnax	142:54d1543e23e5	1035	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	1036	}
nixnax	142:54d1543e23e5	1037	if (dataLen > 0) {
nixnax	154:18b2bd92f557	1038	ppp.pkt.buf[4+ipHeaderLen+headerSizeTcp+dataLen]=0; // insert a null after the data so debug printf stops printing after the data
nixnax	154:18b2bd92f557	1039	putsWhileCheckingInput( ppp.pkt.buf+4+ipHeaderLen+headerSizeTcp ); // print the tcp payload data
nixnax	142:54d1543e23e5	1040	putsWhileCheckingInput("\n");
nixnax	142:54d1543e23e5	1041	}
nixnax	142:54d1543e23e5	1042	}
nixnax	142:54d1543e23e5	1043
nixnax	142:54d1543e23e5	1044	/// handle an incoming TCP packet
nixnax	142:54d1543e23e5	1045	void TCPpacket()
nixnax	142:54d1543e23e5	1046	{
nixnax	142:54d1543e23e5	1047	dumpHeaderIP(0); // dump incoming packet header
nixnax	142:54d1543e23e5	1048	dumpHeaderTCP(0); // dump incoming packet header
nixnax	142:54d1543e23e5	1049	if (v2) dumpDataTCP();
nixnax	142:54d1543e23e5	1050	tcpHandler();
nixnax	142:54d1543e23e5	1051	}
nixnax	142:54d1543e23e5	1052
nixnax	142:54d1543e23e5	1053	/// handle the remaining IP protocols by ignoring them
nixnax	142:54d1543e23e5	1054	void otherProtocol()
nixnax	142:54d1543e23e5	1055	{
nixnax	142:54d1543e23e5	1056	debugPrintf("Other IP protocol");
nixnax	142:54d1543e23e5	1057	}
nixnax	142:54d1543e23e5	1058
nixnax	142:54d1543e23e5	1059	/// process an incoming IP packet
nixnax	142:54d1543e23e5	1060	void IPframe()
nixnax	142:54d1543e23e5	1061	{
nixnax	142:54d1543e23e5	1062	int protocol = ppp.pkt.buf[13];
nixnax	142:54d1543e23e5	1063	switch (protocol) {
nixnax	142:54d1543e23e5	1064	case 1:
nixnax	142:54d1543e23e5	1065	ICMPpacket();
nixnax	142:54d1543e23e5	1066	break;
nixnax	142:54d1543e23e5	1067	case 2:
nixnax	142:54d1543e23e5	1068	IGMPpacket();
nixnax	142:54d1543e23e5	1069	break;
nixnax	142:54d1543e23e5	1070	case 17:
nixnax	142:54d1543e23e5	1071	UDPpacket();
nixnax	142:54d1543e23e5	1072	break;
nixnax	142:54d1543e23e5	1073	case 6:
nixnax	142:54d1543e23e5	1074	TCPpacket();
nixnax	142:54d1543e23e5	1075	break;
nixnax	142:54d1543e23e5	1076	default:
nixnax	142:54d1543e23e5	1077	otherProtocol();
nixnax	142:54d1543e23e5	1078	}
nixnax	142:54d1543e23e5	1079	}
nixnax	142:54d1543e23e5	1080
nixnax	142:54d1543e23e5	1081	/// respond to LCP (line configuration protocol) configuration request) by allowing no options
nixnax	142:54d1543e23e5	1082	void LCPconfReq()
nixnax	142:54d1543e23e5	1083	{
nixnax	142:54d1543e23e5	1084	debugPrintf("LCP Config ");
nixnax	142:54d1543e23e5	1085	if (ppp.pkt.buf[7] != 4) {
nixnax	142:54d1543e23e5	1086	ppp.pkt.buf[4]=4; // allow only "no options" which means Maximum Receive Unit (MRU) is default 1500 bytes
nixnax	142:54d1543e23e5	1087	debugPrintf("Reject\n");
nixnax	144:01d98cf7738e	1088	sendPppFrame();
nixnax	142:54d1543e23e5	1089	} else {
nixnax	142:54d1543e23e5	1090	ppp.pkt.buf[4]=2; // ack zero conf
nixnax	142:54d1543e23e5	1091	debugPrintf("Ack\n");
nixnax	144:01d98cf7738e	1092	sendPppFrame();
nixnax	142:54d1543e23e5	1093	debugPrintf("LCP Ask\n");
nixnax	142:54d1543e23e5	1094	ppp.pkt.buf[4]=1; // request no options
nixnax	144:01d98cf7738e	1095	sendPppFrame();
nixnax	142:54d1543e23e5	1096	}
nixnax	142:54d1543e23e5	1097	}
nixnax	142:54d1543e23e5	1098
nixnax	142:54d1543e23e5	1099	/// handle LCP acknowledge packets by ignoring them
nixnax	142:54d1543e23e5	1100	void LCPconfAck()
nixnax	142:54d1543e23e5	1101	{
nixnax	142:54d1543e23e5	1102	debugPrintf("LCP Ack\n");
nixnax	142:54d1543e23e5	1103	}
nixnax	142:54d1543e23e5	1104
nixnax	143:c5019f856a56	1105	/// handle LCP end (disconnect) packets by acknowledging them and by setting ppp.online to false
nixnax	142:54d1543e23e5	1106	void LCPend()
nixnax	142:54d1543e23e5	1107	{
nixnax	142:54d1543e23e5	1108	ppp.pkt.buf[4]=6;
nixnax	144:01d98cf7738e	1109	sendPppFrame(); // acknowledge
nixnax	142:54d1543e23e5	1110	ppp.online=0; // start hunting for connect string again
nixnax	142:54d1543e23e5	1111	pppInitStruct(); // flush the receive buffer
nixnax	143:c5019f856a56	1112	debugPrintf("LCP End (Disconnect from host)\n");
nixnax	142:54d1543e23e5	1113	}
nixnax	142:54d1543e23e5	1114
nixnax	142:54d1543e23e5	1115	/// respond to other LCP requests by ignoring them
nixnax	142:54d1543e23e5	1116	void LCPother()
nixnax	142:54d1543e23e5	1117	{
nixnax	142:54d1543e23e5	1118	debugPrintf("LCP Other\n");
nixnax	142:54d1543e23e5	1119	dumpPPPFrame();
nixnax	142:54d1543e23e5	1120	}
nixnax	142:54d1543e23e5	1121
nixnax	142:54d1543e23e5	1122	/// process incoming LCP packets
nixnax	142:54d1543e23e5	1123	void LCPframe()
nixnax	142:54d1543e23e5	1124	{
nixnax	142:54d1543e23e5	1125	int code = ppp.pkt.buf[4];
nixnax	142:54d1543e23e5	1126	switch (code) {
nixnax	142:54d1543e23e5	1127	case 1:
nixnax	142:54d1543e23e5	1128	LCPconfReq();
nixnax	142:54d1543e23e5	1129	break; // config request
nixnax	142:54d1543e23e5	1130	case 2:
nixnax	142:54d1543e23e5	1131	LCPconfAck();
nixnax	142:54d1543e23e5	1132	break; // config ack
nixnax	142:54d1543e23e5	1133	case 5:
nixnax	142:54d1543e23e5	1134	LCPend();
nixnax	142:54d1543e23e5	1135	break; // end connection
nixnax	142:54d1543e23e5	1136	default:
nixnax	142:54d1543e23e5	1137	LCPother();
nixnax	142:54d1543e23e5	1138	}
nixnax	142:54d1543e23e5	1139	}
nixnax	142:54d1543e23e5	1140
nixnax	142:54d1543e23e5	1141	/// discard packets that are not IP, IPCP, or LCP
nixnax	142:54d1543e23e5	1142	void discardedFrame()
nixnax	142:54d1543e23e5	1143	{
nixnax	142:54d1543e23e5	1144	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	1145	}
nixnax	142:54d1543e23e5	1146
nixnax	142:54d1543e23e5	1147	/// determine the packet type (IP, IPCP or LCP) of incoming packets
nixnax	142:54d1543e23e5	1148	void determinePacketType()
nixnax	142:54d1543e23e5	1149	{
nixnax	142:54d1543e23e5	1150	if ( ppp.pkt.buf[0] != 0xff ) {
nixnax	142:54d1543e23e5	1151	debugPrintf("byte0 != ff\n");
nixnax	142:54d1543e23e5	1152	return;
nixnax	142:54d1543e23e5	1153	}
nixnax	142:54d1543e23e5	1154	if ( ppp.pkt.buf[1] != 3 ) {
nixnax	142:54d1543e23e5	1155	debugPrintf("byte1 != 3\n");
nixnax	142:54d1543e23e5	1156	return;
nixnax	142:54d1543e23e5	1157	}
nixnax	142:54d1543e23e5	1158	if ( ppp.pkt.buf[3] != 0x21 ) {
nixnax	142:54d1543e23e5	1159	debugPrintf("byte2 != 21\n");
nixnax	142:54d1543e23e5	1160	return;
nixnax	142:54d1543e23e5	1161	}
nixnax	142:54d1543e23e5	1162	int packetType = ppp.pkt.buf[2];
nixnax	142:54d1543e23e5	1163	switch (packetType) {
nixnax	142:54d1543e23e5	1164	case 0xc0:
nixnax	142:54d1543e23e5	1165	LCPframe();
nixnax	142:54d1543e23e5	1166	break; // link control
nixnax	142:54d1543e23e5	1167	case 0x80:
nixnax	142:54d1543e23e5	1168	IPCPframe();
nixnax	142:54d1543e23e5	1169	break; // IP control
nixnax	142:54d1543e23e5	1170	case 0x00:
nixnax	142:54d1543e23e5	1171	IPframe();
nixnax	142:54d1543e23e5	1172	break; // IP itself
nixnax	142:54d1543e23e5	1173	default:
nixnax	142:54d1543e23e5	1174	discardedFrame();
nixnax	142:54d1543e23e5	1175	}
nixnax	142:54d1543e23e5	1176	}
nixnax	142:54d1543e23e5	1177
nixnax	146:a45f49a2b29c	1178	/// a sniffer tool to assist in figuring out where in the code we are having characters in the input buffer
nixnax	146:a45f49a2b29c	1179	void sniff()
nixnax	146:a45f49a2b29c	1180	{
nixnax	146:a45f49a2b29c	1181	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	1182	}
nixnax	146:a45f49a2b29c	1183
nixnax	142:54d1543e23e5	1184	/// scan the PPP serial input stream for frame start markers
nixnax	143:c5019f856a56	1185	void waitForPppFrame()
nixnax	142:54d1543e23e5	1186	{
nixnax	142:54d1543e23e5	1187	while(1) {
nixnax	142:54d1543e23e5	1188	checkPc(); // handle received characters
nixnax	142:54d1543e23e5	1189	if ( ppp.rx.head != ppp.rx.tail ) {
nixnax	142:54d1543e23e5	1190	int oldTail = ppp.rx.tail; // remember where the character is located in the buffer
nixnax	142:54d1543e23e5	1191	int rx = pc_getBuf(); // get the character
nixnax	142:54d1543e23e5	1192	if (rx==FRAME_7E) {
nixnax	142:54d1543e23e5	1193	if (ppp.firstFrame) { // is this the start of the first frame start
nixnax	142:54d1543e23e5	1194	ppp.firstFrame=0;
nixnax	142:54d1543e23e5	1195	ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
nixnax	142:54d1543e23e5	1196	ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where first frame started
nixnax	142:54d1543e23e5	1197	} else {
nixnax	142:54d1543e23e5	1198	ppp.hdlc.frameEndIndex=oldTail; // mark the frame end character
nixnax	142:54d1543e23e5	1199	processPPPFrame(ppp.hdlc.frameStartIndex, ppp.hdlc.frameEndIndex); // process the frame
nixnax	142:54d1543e23e5	1200	ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
nixnax	142:54d1543e23e5	1201	ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where next frame started
nixnax	142:54d1543e23e5	1202	break;
nixnax	142:54d1543e23e5	1203	}
nixnax	142:54d1543e23e5	1204	}
nixnax	142:54d1543e23e5	1205	}
nixnax	142:54d1543e23e5	1206	}
nixnax	142:54d1543e23e5	1207	}
nixnax	142:54d1543e23e5	1208
nixnax	153:7993def8663f	1209	/// 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	1210	// Note: a 0x7E in the input stream (ppp start of frame character) will also set ppp.online to true - see checkPc();
nixnax	153:7993def8663f	1211	void waitForPcConnectString()
nixnax	142:54d1543e23e5	1212	{
nixnax	142:54d1543e23e5	1213	while(ppp.online == 0) {
nixnax	142:54d1543e23e5	1214	checkPc(); // gather received characters
nixnax	142:54d1543e23e5	1215	// search for Windows Dialup Networking "Direct Connection Between Two Computers" expected connect string
nixnax	142:54d1543e23e5	1216	char * found1 = strstr( (char *)ppp.rx.buf, "CLIENT" );
nixnax	142:54d1543e23e5	1217	if (found1 != NULL) {
nixnax	142:54d1543e23e5	1218	// respond with Windows Dialup networking expected "Direct Connection Between Two Computers" response string
nixnax	143:c5019f856a56	1219	if (v0) debugPrintf("Connected: Found connect string \"CLIENT\", sent \"CLIENTSERVER\"\n");
nixnax	142:54d1543e23e5	1220	pc.puts("CLIENTSERVER");
nixnax	142:54d1543e23e5	1221	ppp.online=1; // we are connected - set flag so we stop looking for the connect string
nixnax	142:54d1543e23e5	1222	checkPc();
nixnax	142:54d1543e23e5	1223	}
nixnax	142:54d1543e23e5	1224	}
nixnax	142:54d1543e23e5	1225	}
nixnax	142:54d1543e23e5	1226
nixnax	144:01d98cf7738e	1227	/// Initialize PPP data structure and set serial port(s) baud rate(s)
nixnax	144:01d98cf7738e	1228	void initializePpp()
nixnax	142:54d1543e23e5	1229	{
nixnax	142:54d1543e23e5	1230	pc.baud(115200); // USB serial port to pc
nixnax	144:01d98cf7738e	1231	debugBaudRate(115200); // baud rate for (optional) debug serial port
nixnax	142:54d1543e23e5	1232	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	1233	pppInitStruct(); // initialize all the PPP properties
nixnax	143:c5019f856a56	1234	}

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Repository details

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.