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@167:ff8a2d8beeb1, 2017-09-04 (annotated)

Committer:: nixnax
Date:: Mon Sep 04 04:13:15 2017 +0000
Revision:: 167:ff8a2d8beeb1
Parent:: 166:0386c2d5dc89
Child:: 168:c77eb908042a

ICMP header structure & ICMP/LCP 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	167:ff8a2d8beeb1	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	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	165:c47826d07e0d	158	/// a structure to keep all our ppp variables in
nixnax	142:54d1543e23e5	159	struct pppType {
nixnax	167:ff8a2d8beeb1	160	union {
nixnax	167:ff8a2d8beeb1	161	pppHeaderType * ppp; // pointer to ppp structure
nixnax	167:ff8a2d8beeb1	162	ipcpHeaderType * ipcp; // pointer to ipcp structure
nixnax	167:ff8a2d8beeb1	163	};
nixnax	154:18b2bd92f557	164	union {
nixnax	154:18b2bd92f557	165	ipHeaderType * ip; // pointer to ip header struct
nixnax	155:9c6a1d249e26	166	char * ipStart; // char pointer to ip header struct (need a char pointer for byte offset calculations)
nixnax	154:18b2bd92f557	167	};
nixnax	167:ff8a2d8beeb1	168	union { // a union for the packet type contained in the IP packet
nixnax	167:ff8a2d8beeb1	169	tcpHeaderType * tcp; // pointer to tcp header struct
nixnax	167:ff8a2d8beeb1	170	udpHeaderType * udp; // pointer to udp header struct
nixnax	165:c47826d07e0d	171	icmpHeaderType * icmp; // pointer to udp header struct
nixnax	167:ff8a2d8beeb1	172	char * tcpStart; // char pointer to tcp header struct (need a char pointer for byte offset calculations)
nixnax	167:ff8a2d8beeb1	173	char * udpStart; // char pointer to udp header struct (need a char pointer for byte offset calculations)
nixnax	165:c47826d07e0d	174	char * icmpStart; // char pointer to icmp header struct (need a char pointer for byte offset calculations)
nixnax	160:bd701ad564cb	175	};
nixnax	142:54d1543e23e5	176	int online; // we hunt for a PPP connection if this is zero
nixnax	143:c5019f856a56	177	int hostIP; // ip address of host
nixnax	145:098b6ed2f7f2	178	int fcs; // PPP "frame check sequence" - a 16-bit HDLC-like checksum used in all PPP frames
nixnax	142:54d1543e23e5	179	int ledState; // state of LED1
nixnax	146:a45f49a2b29c	180	int responseCounter;
nixnax	142:54d1543e23e5	181	int firstFrame; // cleared after first frame
nixnax	159:4d1bf96a59cd	182	unsigned int sum; // a checksum used in headers
nixnax	142:54d1543e23e5	183	struct {
nixnax	142:54d1543e23e5	184	#define RXBUFLEN (1<<11)
nixnax	142:54d1543e23e5	185	// the serial port receive buffer and packet buffer, size is RXBUFLEN (currently 2048 bytes)
nixnax	142:54d1543e23e5	186	char buf[RXBUFLEN]; // RXBUFLEN MUST be a power of two because we use & operator for fast wrap-around in ring buffer
nixnax	142:54d1543e23e5	187	int head;
nixnax	142:54d1543e23e5	188	int tail;
nixnax	142:54d1543e23e5	189	int rtail;
nixnax	142:54d1543e23e5	190	int buflevel;
nixnax	142:54d1543e23e5	191	} rx; // serial port objects
nixnax	142:54d1543e23e5	192	struct {
nixnax	142:54d1543e23e5	193	int len; // number of bytes in buffer
nixnax	142:54d1543e23e5	194	int crc; // PPP CRC (frame check)
nixnax	152:025c73b6c0a9	195	#define PPP_max_size 1600
nixnax	152:025c73b6c0a9	196	// we are assuming 100 bytes more than MTU size of 1500
nixnax	154:18b2bd92f557	197	char buf[PPP_max_size]; // send and receive buffer large enough for largest IP packet
nixnax	142:54d1543e23e5	198	} pkt; // ppp buffer objects
nixnax	142:54d1543e23e5	199	struct {
nixnax	142:54d1543e23e5	200	int frameStartIndex; // frame start marker
nixnax	142:54d1543e23e5	201	int frameEndIndex; // frame end marker
nixnax	142:54d1543e23e5	202	} hdlc; // hdlc frame objects
nixnax	142:54d1543e23e5	203	struct {
nixnax	142:54d1543e23e5	204	unsigned int ident; // our IP ident value (outgoing frame count)
nixnax	154:18b2bd92f557	205	} ipData; // ip related object
nixnax	142:54d1543e23e5	206	};
nixnax	142:54d1543e23e5	207
nixnax	142:54d1543e23e5	208	pppType ppp; // our global - definitely not thread safe
nixnax	142:54d1543e23e5	209
nixnax	142:54d1543e23e5	210	/// Initialize the ppp structure and clear the receive buffer
nixnax	142:54d1543e23e5	211	void pppInitStruct()
nixnax	142:54d1543e23e5	212	{
nixnax	142:54d1543e23e5	213	memset( ppp.rx.buf, 0, RXBUFLEN);
nixnax	142:54d1543e23e5	214	ppp.online=0;
nixnax	142:54d1543e23e5	215	ppp.rx.tail=0;
nixnax	142:54d1543e23e5	216	ppp.rx.rtail=0;
nixnax	142:54d1543e23e5	217	ppp.rx.head=0;
nixnax	142:54d1543e23e5	218	ppp.rx.buflevel=0;
nixnax	142:54d1543e23e5	219	ppp.pkt.len=0;
nixnax	154:18b2bd92f557	220	ppp.ipData.ident=10000; // easy to recognize in ip packet dumps
nixnax	142:54d1543e23e5	221	ppp.ledState=0;
nixnax	142:54d1543e23e5	222	ppp.hdlc.frameStartIndex=0;
nixnax	146:a45f49a2b29c	223	ppp.responseCounter=0;
nixnax	142:54d1543e23e5	224	ppp.firstFrame=1;
nixnax	154:18b2bd92f557	225	ppp.ppp = (pppHeaderType *)ppp.pkt.buf;
nixnax	154:18b2bd92f557	226	ppp.ip = (ipHeaderType *)(ppp.pkt.buf+4); // ppp header is 4 bytes long
nixnax	142:54d1543e23e5	227	}
nixnax	142:54d1543e23e5	228
nixnax	142:54d1543e23e5	229	/// Toggle the LED on every second PPP packet received
nixnax	142:54d1543e23e5	230	void led1Toggle()
nixnax	142:54d1543e23e5	231	{
nixnax	142:54d1543e23e5	232	led1 = (ppp.ledState >> 1) & 1; // use second bit, in other words toggle LED only every second packet
nixnax	143:c5019f856a56	233	ppp.ledState++;
nixnax	142:54d1543e23e5	234	}
nixnax	142:54d1543e23e5	235
nixnax	152:025c73b6c0a9	236	/// returns 1 after a connect message, 0 at startup or after a disconnect message
nixnax	150:3366bf3d294e	237	int connectedPpp()
nixnax	142:54d1543e23e5	238	{
nixnax	142:54d1543e23e5	239	return ppp.online;
nixnax	143:c5019f856a56	240	}
nixnax	142:54d1543e23e5	241
nixnax	143:c5019f856a56	242	/// Check for available characters from the PC and read them into our own circular serial receive buffer at ppp.rx.buf.
nixnax	143:c5019f856a56	243	/// Also, if we are offline and a 0x7e frame start character is seen, we go online immediately
nixnax	142:54d1543e23e5	244	void checkPc()
nixnax	142:54d1543e23e5	245	{
nixnax	142:54d1543e23e5	246	char ch;
nixnax	142:54d1543e23e5	247	if ( pc.readable() ) {
nixnax	142:54d1543e23e5	248	int hd = (ppp.rx.head+1)&(RXBUFLEN-1); // increment/wrap head index
nixnax	142:54d1543e23e5	249	if ( hd == ppp.rx.rtail ) {
nixnax	142:54d1543e23e5	250	debugPrintf("\nReceive buffer full\n");
nixnax	142:54d1543e23e5	251	return;
nixnax	142:54d1543e23e5	252	}
nixnax	142:54d1543e23e5	253	ch = pc.getc(); // read new character
nixnax	142:54d1543e23e5	254	ppp.rx.buf[ppp.rx.head] = ch; // insert in our receive buffer
nixnax	142:54d1543e23e5	255	if ( ppp.online == 0 ) {
nixnax	142:54d1543e23e5	256	if (ch == 0x7E) {
nixnax	142:54d1543e23e5	257	ppp.online = 1;
nixnax	142:54d1543e23e5	258	}
nixnax	142:54d1543e23e5	259	}
nixnax	142:54d1543e23e5	260	ppp.rx.head = hd; // update head pointer
nixnax	142:54d1543e23e5	261	ppp.rx.buflevel++;
nixnax	142:54d1543e23e5	262	}
nixnax	142:54d1543e23e5	263	}
nixnax	142:54d1543e23e5	264
nixnax	142:54d1543e23e5	265	/// print to debug port while checking for incoming characters
nixnax	142:54d1543e23e5	266	void putcWhileCheckingInput( char outByte )
nixnax	142:54d1543e23e5	267	{
nixnax	142:54d1543e23e5	268	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	269	checkPc();
nixnax	142:54d1543e23e5	270	debugPutc( outByte );
nixnax	142:54d1543e23e5	271	checkPc();
nixnax	142:54d1543e23e5	272	#endif
nixnax	142:54d1543e23e5	273	}
nixnax	142:54d1543e23e5	274
nixnax	142:54d1543e23e5	275	/// puts to debug port while checking the PPP input stream
nixnax	142:54d1543e23e5	276	void putsWhileCheckingInput( char * data )
nixnax	142:54d1543e23e5	277	{
nixnax	142:54d1543e23e5	278	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	279	char * nextChar = data;
nixnax	142:54d1543e23e5	280	while( *nextChar != 0 ) {
nixnax	142:54d1543e23e5	281	putcWhileCheckingInput( *nextChar ); // write one character to debug port while checking input
nixnax	142:54d1543e23e5	282	nextChar++;
nixnax	142:54d1543e23e5	283	}
nixnax	142:54d1543e23e5	284	#endif
nixnax	142:54d1543e23e5	285	}
nixnax	142:54d1543e23e5	286
nixnax	145:098b6ed2f7f2	287	/// Initialize the PPP FCS (frame check sequence) total
nixnax	145:098b6ed2f7f2	288	void fcsReset()
nixnax	142:54d1543e23e5	289	{
nixnax	145:098b6ed2f7f2	290	ppp.fcs=0xffff; // crc restart
nixnax	142:54d1543e23e5	291	}
nixnax	142:54d1543e23e5	292
nixnax	145:098b6ed2f7f2	293	/// update the cumulative PPP FCS (frame check sequence)
nixnax	145:098b6ed2f7f2	294	void fcsDo(int x)
nixnax	142:54d1543e23e5	295	{
nixnax	142:54d1543e23e5	296	for (int i=0; i<8; i++) {
nixnax	145:098b6ed2f7f2	297	ppp.fcs=((ppp.fcs&1)^(x&1))?(ppp.fcs>>1)^0x8408:ppp.fcs>>1; // crc calculator
nixnax	142:54d1543e23e5	298	x>>=1;
nixnax	142:54d1543e23e5	299	}
nixnax	142:54d1543e23e5	300	checkPc(); // handle input
nixnax	142:54d1543e23e5	301	}
nixnax	142:54d1543e23e5	302
nixnax	145:098b6ed2f7f2	303	/// calculate the PPP FCS (frame check sequence) on an entire block of memory
nixnax	145:098b6ed2f7f2	304	int fcsBuf(char * buf, int size) // crc on an entire block of memory
nixnax	142:54d1543e23e5	305	{
nixnax	145:098b6ed2f7f2	306	fcsReset();
nixnax	145:098b6ed2f7f2	307	for(int i=0; i<size; i++)fcsDo(*buf++);
nixnax	145:098b6ed2f7f2	308	return ppp.fcs;
nixnax	142:54d1543e23e5	309	}
nixnax	142:54d1543e23e5	310
nixnax	142:54d1543e23e5	311	/// Get one character from our received PPP buffer
nixnax	142:54d1543e23e5	312	int pc_getBuf()
nixnax	142:54d1543e23e5	313	{
nixnax	142:54d1543e23e5	314	int x = ppp.rx.buf[ ppp.rx.tail ];
nixnax	142:54d1543e23e5	315	ppp.rx.tail=(ppp.rx.tail+1)&(RXBUFLEN-1);
nixnax	142:54d1543e23e5	316	ppp.rx.buflevel--;
nixnax	142:54d1543e23e5	317	return x;
nixnax	142:54d1543e23e5	318	}
nixnax	142:54d1543e23e5	319
nixnax	142:54d1543e23e5	320	/// Dump a PPP frame to the debug serial port
nixnax	142:54d1543e23e5	321	/// Note - the hex output of dumpPPPFrame() can be imported into WireShark
nixnax	142:54d1543e23e5	322	/// Capture the frame's hex output in your terminal program and save as a text file
nixnax	164:c3de3d212c4b	323	/// In WireShark, use "Import Hex File". Import options are: Offset=None, Protocol=PPP.
nixnax	142:54d1543e23e5	324	void dumpPPPFrame()
nixnax	142:54d1543e23e5	325	{
nixnax	142:54d1543e23e5	326	char pbuf[30];
nixnax	142:54d1543e23e5	327	for(int i=0; i<ppp.pkt.len; i++) {
nixnax	142:54d1543e23e5	328	checkPc();
nixnax	142:54d1543e23e5	329	sprintf(pbuf, "%02x ", ppp.pkt.buf[i]);
nixnax	142:54d1543e23e5	330	checkPc();
nixnax	142:54d1543e23e5	331	putsWhileCheckingInput(pbuf);
nixnax	142:54d1543e23e5	332	}
nixnax	142:54d1543e23e5	333	checkPc();
nixnax	142:54d1543e23e5	334	sprintf(pbuf, " CRC=%04x Len=%d\n", ppp.pkt.crc, ppp.pkt.len);
nixnax	142:54d1543e23e5	335	checkPc();
nixnax	142:54d1543e23e5	336	putsWhileCheckingInput(pbuf);
nixnax	142:54d1543e23e5	337	}
nixnax	142:54d1543e23e5	338
nixnax	142:54d1543e23e5	339	/// Process a received PPP frame
nixnax	142:54d1543e23e5	340	void processPPPFrame(int start, int end)
nixnax	142:54d1543e23e5	341	{
nixnax	142:54d1543e23e5	342	led1Toggle(); // change led1 state on every frame we receive
nixnax	142:54d1543e23e5	343	if(start==end) {
nixnax	142:54d1543e23e5	344	return; // empty frame
nixnax	142:54d1543e23e5	345	}
nixnax	145:098b6ed2f7f2	346	fcsReset();
nixnax	142:54d1543e23e5	347	char * dest = ppp.pkt.buf;
nixnax	142:54d1543e23e5	348	ppp.pkt.len=0;
nixnax	142:54d1543e23e5	349	int unstuff=0;
nixnax	142:54d1543e23e5	350	int idx = start;
nixnax	142:54d1543e23e5	351	while(1) {
nixnax	142:54d1543e23e5	352	checkPc();
nixnax	142:54d1543e23e5	353	if (unstuff==0) {
nixnax	142:54d1543e23e5	354	if (ppp.rx.buf[idx]==0x7d) unstuff=1;
nixnax	142:54d1543e23e5	355	else {
nixnax	142:54d1543e23e5	356	*dest = ppp.rx.buf[idx];
nixnax	142:54d1543e23e5	357	ppp.pkt.len++;
nixnax	142:54d1543e23e5	358	dest++;
nixnax	145:098b6ed2f7f2	359	fcsDo(ppp.rx.buf[idx]);
nixnax	142:54d1543e23e5	360	}
nixnax	142:54d1543e23e5	361	} else { // unstuff characters prefixed with 0x7d
nixnax	142:54d1543e23e5	362	*dest = ppp.rx.buf[idx]^0x20;
nixnax	142:54d1543e23e5	363	ppp.pkt.len++;
nixnax	142:54d1543e23e5	364	dest++;
nixnax	145:098b6ed2f7f2	365	fcsDo(ppp.rx.buf[idx]^0x20);
nixnax	142:54d1543e23e5	366	unstuff=0;
nixnax	142:54d1543e23e5	367	}
nixnax	142:54d1543e23e5	368	idx = (idx+1) & (RXBUFLEN-1);
nixnax	142:54d1543e23e5	369	if (idx == end) break;
nixnax	142:54d1543e23e5	370	}
nixnax	145:098b6ed2f7f2	371	ppp.pkt.crc = ppp.fcs & 0xffff;
nixnax	142:54d1543e23e5	372	if(0) dumpPPPFrame(); // set to 1 to dump ALL ppp frames
nixnax	142:54d1543e23e5	373	if (ppp.pkt.crc == 0xf0b8) { // check for good CRC
nixnax	142:54d1543e23e5	374	determinePacketType();
nixnax	142:54d1543e23e5	375	} else {
nixnax	142:54d1543e23e5	376	#define REPORT_FCS_ERROR_YES
nixnax	142:54d1543e23e5	377	#ifdef REPORT_FCS_ERROR_YES
nixnax	142:54d1543e23e5	378	char pbuf[50]; // local print buffer
nixnax	142:54d1543e23e5	379	checkPc();
nixnax	142:54d1543e23e5	380	sprintf(pbuf, "\nPPP FCS(crc) Error CRC=%x Length = %d\n",ppp.pkt.crc,ppp.pkt.len); // print a debug line
nixnax	142:54d1543e23e5	381	checkPc();
nixnax	142:54d1543e23e5	382	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	383	if(0) dumpPPPFrame(); // set to 1 to dump frames with errors in them
nixnax	142:54d1543e23e5	384	#endif
nixnax	142:54d1543e23e5	385	}
nixnax	142:54d1543e23e5	386	}
nixnax	142:54d1543e23e5	387
nixnax	142:54d1543e23e5	388	/// output a character to the PPP port while checking for incoming characters
nixnax	142:54d1543e23e5	389	void pcPutcWhileCheckingInput(int ch)
nixnax	142:54d1543e23e5	390	{
nixnax	142:54d1543e23e5	391	checkPc(); // check input
nixnax	142:54d1543e23e5	392	pc.putc(ch);
nixnax	142:54d1543e23e5	393	checkPc();
nixnax	142:54d1543e23e5	394	}
nixnax	142:54d1543e23e5	395
nixnax	142:54d1543e23e5	396	/// do PPP HDLC-like handling of special (flag) characters
nixnax	143:c5019f856a56	397	void hdlcPut(int ch)
nixnax	142:54d1543e23e5	398	{
nixnax	142:54d1543e23e5	399	if ( (ch<0x20) \|\| (ch==0x7d) \|\| (ch==0x7e) ) {
nixnax	142:54d1543e23e5	400	pcPutcWhileCheckingInput(0x7d);
nixnax	142:54d1543e23e5	401	pcPutcWhileCheckingInput(ch^0x20); // these characters need special handling
nixnax	142:54d1543e23e5	402	} else {
nixnax	142:54d1543e23e5	403	pcPutcWhileCheckingInput(ch);
nixnax	142:54d1543e23e5	404	}
nixnax	142:54d1543e23e5	405	}
nixnax	142:54d1543e23e5	406
nixnax	142:54d1543e23e5	407	/// send a PPP frame in HDLC format
nixnax	144:01d98cf7738e	408	void sendPppFrame()
nixnax	143:c5019f856a56	409	{
nixnax	145:098b6ed2f7f2	410	int crc = fcsBuf(ppp.pkt.buf, ppp.pkt.len-2); // update crc
nixnax	142:54d1543e23e5	411	ppp.pkt.buf[ ppp.pkt.len-2 ] = (~crc>>0); // fcs lo (crc)
nixnax	142:54d1543e23e5	412	ppp.pkt.buf[ ppp.pkt.len-1 ] = (~crc>>8); // fcs hi (crc)
nixnax	142:54d1543e23e5	413	pcPutcWhileCheckingInput(0x7e); // hdlc start-of-frame "flag"
nixnax	142:54d1543e23e5	414	for(int i=0; i<ppp.pkt.len; i++) {
nixnax	142:54d1543e23e5	415	wait_us(86); // wait one character time
nixnax	142:54d1543e23e5	416	checkPc();
nixnax	142:54d1543e23e5	417	hdlcPut( ppp.pkt.buf[i] ); // send a character
nixnax	142:54d1543e23e5	418	}
nixnax	142:54d1543e23e5	419	pcPutcWhileCheckingInput(0x7e); // hdlc end-of-frame "flag"
nixnax	142:54d1543e23e5	420	}
nixnax	142:54d1543e23e5	421
nixnax	143:c5019f856a56	422	/// 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	423	int bufferToIP(char * buffer)
nixnax	143:c5019f856a56	424	{
nixnax	143:c5019f856a56	425	int result=0;
nixnax	143:c5019f856a56	426	for(int i=0; i<4; i++) result = (result<<8)\|(*buffer++ & 0xff);
nixnax	143:c5019f856a56	427	return result;
nixnax	143:c5019f856a56	428	}
nixnax	143:c5019f856a56	429
nixnax	142:54d1543e23e5	430	/// handle IPCP configuration requests
nixnax	142:54d1543e23e5	431	void ipcpConfigRequestHandler()
nixnax	142:54d1543e23e5	432	{
nixnax	142:54d1543e23e5	433	debugPrintf("Their IPCP Config Req, Our Ack\n");
nixnax	143:c5019f856a56	434	if(ppp.pkt.buf[8]==3) {
nixnax	143:c5019f856a56	435	ppp.hostIP = bufferToIP(ppp.pkt.buf+10);
nixnax	143:c5019f856a56	436	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	437	}
nixnax	143:c5019f856a56	438
nixnax	167:ff8a2d8beeb1	439	ppp.ipcp->code=2; // change code to ack
nixnax	144:01d98cf7738e	440	sendPppFrame(); // acknowledge everything they ask for - assume it's IP addresses
nixnax	142:54d1543e23e5	441
nixnax	142:54d1543e23e5	442	debugPrintf("Our IPCP Ask (no options)\n");
nixnax	167:ff8a2d8beeb1	443	ppp.ipcp->code=1; // change code to request
nixnax	167:ff8a2d8beeb1	444	ppp.ipcp->lengthR = __REV16( 4 ); // 4 is minimum length - no options in this request
nixnax	167:ff8a2d8beeb1	445	ppp.pkt.len=4+4+2; // no options in this request shortest ipcp packet possible (4 ppp + 4 ipcp + 2 crc)
nixnax	144:01d98cf7738e	446	sendPppFrame(); // send our request
nixnax	142:54d1543e23e5	447	}
nixnax	142:54d1543e23e5	448
nixnax	142:54d1543e23e5	449	/// handle IPCP acknowledge (do nothing)
nixnax	142:54d1543e23e5	450	void ipcpAckHandler()
nixnax	142:54d1543e23e5	451	{
nixnax	142:54d1543e23e5	452	debugPrintf("Their IPCP Grant\n");
nixnax	142:54d1543e23e5	453	}
nixnax	142:54d1543e23e5	454
nixnax	143:c5019f856a56	455	/// Handle IPCP NACK by sending our suggested IP address if there is an IP involved.
nixnax	143:c5019f856a56	456	/// 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	457	void ipcpNackHandler()
nixnax	142:54d1543e23e5	458	{
nixnax	146:a45f49a2b29c	459	debugPrintf("Their IPCP Nack\n");
nixnax	142:54d1543e23e5	460	if (ppp.pkt.buf[8]==3) { // check if the NACK contains an IP address parameter
nixnax	167:ff8a2d8beeb1	461	ppp.ipcp->code=1; // assume the NACK contains our "suggested" IP address
nixnax	144:01d98cf7738e	462	sendPppFrame(); // let's request this IP address as ours
nixnax	143:c5019f856a56	463	debugPrintf("Our IPCP ACK (received an IP)\n");
nixnax	146:a45f49a2b29c	464	} else { // if it's not an IP nack we ignore it
nixnax	146:a45f49a2b29c	465	debugPrintf("IPCP Nack Ignored\n");
nixnax	146:a45f49a2b29c	466	}
nixnax	142:54d1543e23e5	467	}
nixnax	142:54d1543e23e5	468
nixnax	142:54d1543e23e5	469	/// handle all other IPCP requests (by ignoring them)
nixnax	142:54d1543e23e5	470	void ipcpDefaultHandler()
nixnax	142:54d1543e23e5	471	{
nixnax	142:54d1543e23e5	472	debugPrintf("Their IPCP Other\n");
nixnax	142:54d1543e23e5	473	}
nixnax	142:54d1543e23e5	474
nixnax	142:54d1543e23e5	475	/// process an incoming IPCP packet
nixnax	142:54d1543e23e5	476	void IPCPframe()
nixnax	142:54d1543e23e5	477	{
nixnax	167:ff8a2d8beeb1	478	int action = ppp.ipcp->code; // packet type is here
nixnax	167:ff8a2d8beeb1	479	switch (action) {
nixnax	142:54d1543e23e5	480	case 1:
nixnax	142:54d1543e23e5	481	ipcpConfigRequestHandler();
nixnax	142:54d1543e23e5	482	break;
nixnax	142:54d1543e23e5	483	case 2:
nixnax	142:54d1543e23e5	484	ipcpAckHandler();
nixnax	142:54d1543e23e5	485	break;
nixnax	142:54d1543e23e5	486	case 3:
nixnax	142:54d1543e23e5	487	ipcpNackHandler();
nixnax	142:54d1543e23e5	488	break;
nixnax	142:54d1543e23e5	489	default:
nixnax	142:54d1543e23e5	490	ipcpDefaultHandler();
nixnax	142:54d1543e23e5	491	}
nixnax	142:54d1543e23e5	492	}
nixnax	142:54d1543e23e5	493
nixnax	142:54d1543e23e5	494	/// perform a 16-bit checksum. if the byte count is odd, stuff in an extra zero byte.
nixnax	161:d59f778bc8ab	495	unsigned int dataCheckSum(char * ptr, int len, int restart)
nixnax	142:54d1543e23e5	496	{
nixnax	159:4d1bf96a59cd	497	unsigned int i,hi,lo;
nixnax	142:54d1543e23e5	498	unsigned char placeHolder;
nixnax	161:d59f778bc8ab	499	if (restart) ppp.sum=0;
nixnax	142:54d1543e23e5	500	if (len&1) {
nixnax	142:54d1543e23e5	501	placeHolder = ptr[len];
nixnax	142:54d1543e23e5	502	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	503	}
nixnax	142:54d1543e23e5	504	i=0;
nixnax	142:54d1543e23e5	505	while ( i<len ) {
nixnax	142:54d1543e23e5	506	checkPc();
nixnax	142:54d1543e23e5	507	hi = ptr[i++];
nixnax	142:54d1543e23e5	508	lo = ptr[i++];
nixnax	159:4d1bf96a59cd	509	ppp.sum = ppp.sum + ((hi<<8)\|lo);
nixnax	142:54d1543e23e5	510	}
nixnax	142:54d1543e23e5	511	if (len&1) {
nixnax	142:54d1543e23e5	512	ptr[len] = placeHolder; // restore the extra byte we made zero
nixnax	142:54d1543e23e5	513	}
nixnax	159:4d1bf96a59cd	514	ppp.sum = (ppp.sum & 0xffff) + (ppp.sum>>16);
nixnax	159:4d1bf96a59cd	515	ppp.sum = (ppp.sum & 0xffff) + (ppp.sum>>16); // sum one more time to catch any carry from the carry
nixnax	159:4d1bf96a59cd	516	return ~ppp.sum;
nixnax	142:54d1543e23e5	517	}
nixnax	142:54d1543e23e5	518
nixnax	142:54d1543e23e5	519	/// perform the checksum on an IP header
nixnax	146:a45f49a2b29c	520	void IpHeaderCheckSum()
nixnax	142:54d1543e23e5	521	{
nixnax	161:d59f778bc8ab	522	ppp.ip->checksumR=0; // zero the checsum in the IP header
nixnax	161:d59f778bc8ab	523	int len = 4 * ppp.ip->headerLength; // length of IP header in bytes
nixnax	161:d59f778bc8ab	524	unsigned int sum = dataCheckSum(ppp.ipStart,len,1);
nixnax	161:d59f778bc8ab	525	ppp.ip->checksumR = __REV16( sum ); // insert fresh checksum
nixnax	146:a45f49a2b29c	526	}
nixnax	146:a45f49a2b29c	527
nixnax	147:0f40005cbc5f	528	/// swap the IP source and destination addresses
nixnax	147:0f40005cbc5f	529	void swapIpAddresses()
nixnax	147:0f40005cbc5f	530	{
nixnax	162:594729c0e5c1	531	unsigned int tempHold;
nixnax	162:594729c0e5c1	532	tempHold = ppp.ip->srcAdrR; // tempHold <- source IP
nixnax	162:594729c0e5c1	533	ppp.ip->srcAdrR = ppp.ip->dstAdrR; // source <- dest
nixnax	162:594729c0e5c1	534	ppp.ip->dstAdrR = tempHold; // dest <- tempHold*/
nixnax	147:0f40005cbc5f	535	}
nixnax	147:0f40005cbc5f	536
nixnax	149:969d98f6fb88	537	/// swap the IP source and destination ports
nixnax	149:969d98f6fb88	538	void swapIpPorts()
nixnax	149:969d98f6fb88	539	{
nixnax	149:969d98f6fb88	540	int headerSizeIP = 4*(ppp.pkt.buf[4]&0xf); // calculate size of IP header
nixnax	149:969d98f6fb88	541	char * ipSrcPort = 4 + ppp.pkt.buf + headerSizeIP + 0; // ip source port location
nixnax	149:969d98f6fb88	542	char * ipDstPort = 4 + ppp.pkt.buf + headerSizeIP + 2; // ip destin port location
nixnax	149:969d98f6fb88	543	char tempHold[2];
nixnax	149:969d98f6fb88	544	memcpy(tempHold, ipSrcPort,2); // tempHold <- source
nixnax	149:969d98f6fb88	545	memcpy(ipSrcPort,ipDstPort,2); // source <- dest
nixnax	149:969d98f6fb88	546	memcpy(ipDstPort,tempHold, 2); // dest <- tempHold
nixnax	149:969d98f6fb88	547	}
nixnax	149:969d98f6fb88	548
nixnax	146:a45f49a2b29c	549	/// Process an incoming UDP packet.
nixnax	146:a45f49a2b29c	550	/// If the packet starts with the string "echo " or "test" we echo back a special packet
nixnax	146:a45f49a2b29c	551	void UDPpacket()
nixnax	146:a45f49a2b29c	552	{
nixnax	163:d1b4328e9f08	553	struct {
nixnax	163:d1b4328e9f08	554	unsigned int all; // length of entire ip packet
nixnax	163:d1b4328e9f08	555	unsigned int header; // length of ip header
nixnax	163:d1b4328e9f08	556	} ipLength;
nixnax	163:d1b4328e9f08	557
nixnax	163:d1b4328e9f08	558	struct {
nixnax	165:c47826d07e0d	559	unsigned int all; // length of entire udp packet
nixnax	163:d1b4328e9f08	560	unsigned int data; // length of udp data segment
nixnax	163:d1b4328e9f08	561	} udpLength;
nixnax	163:d1b4328e9f08	562
nixnax	163:d1b4328e9f08	563	ipLength.header = 4 * ppp.ip->headerLength; // length of ip header
nixnax	163:d1b4328e9f08	564	ppp.udpStart = ppp.ipStart + ipLength.header; // calculate start of udp header
nixnax	163:d1b4328e9f08	565	udpLength.all = __REV16( ppp.udp->lengthR ); //((udpLen[0]<<8) \| udpLen[1]); // size of udp packet
nixnax	163:d1b4328e9f08	566	udpLength.data = udpLength.all - 8; // size of udp data
nixnax	147:0f40005cbc5f	567
nixnax	146:a45f49a2b29c	568	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	167:ff8a2d8beeb1	569	char * srcIP = ppp.ip->srcAdrPtr; //ipHeader+12; // IP source
nixnax	167:ff8a2d8beeb1	570	char * dstIP = ppp.ip->dstAdrPtr; //ipHeader+16; // IP destination
nixnax	163:d1b4328e9f08	571
nixnax	163:d1b4328e9f08	572	unsigned int udpSrcPort = __REV16( ppp.udp->srcPortR ); //(udpSrcPort[0]<<8)\|udpSrcPort[1]; // integer of UDP source port
nixnax	163:d1b4328e9f08	573	unsigned int udpDstPort = __REV16( ppp.udp->dstPortR ); //(udpDstPort[0]<<8)\|udpDstPort[1]; // integer of UDP dest port
nixnax	163:d1b4328e9f08	574
nixnax	163:d1b4328e9f08	575	if(v0) {
nixnax	163:d1b4328e9f08	576	debugPrintf("UDP %d.%d.%d.%d:%d ", srcIP[0],srcIP[1],srcIP[2],srcIP[3],udpSrcPort);
nixnax	163:d1b4328e9f08	577	debugPrintf("%d.%d.%d.%d:%d ", dstIP[0],dstIP[1],dstIP[2],dstIP[3],udpDstPort);
nixnax	163:d1b4328e9f08	578	debugPrintf("Len %03d", udpLength);
nixnax	163:d1b4328e9f08	579	}
nixnax	146:a45f49a2b29c	580	if (v1) {
nixnax	163:d1b4328e9f08	581	int printSize = udpLength.data;
nixnax	146:a45f49a2b29c	582	if (printSize > 20) printSize = 20; // print only first 20 characters
nixnax	146:a45f49a2b29c	583	for (int i=0; i<printSize; i++) {
nixnax	163:d1b4328e9f08	584	char ch = ppp.udp->data[i];
nixnax	146:a45f49a2b29c	585	if (ch>31 && ch<127) {
nixnax	146:a45f49a2b29c	586	debugPrintf("%c", ch);
nixnax	146:a45f49a2b29c	587	} else {
nixnax	146:a45f49a2b29c	588	debugPrintf("_");
nixnax	146:a45f49a2b29c	589	}
nixnax	146:a45f49a2b29c	590	}
nixnax	146:a45f49a2b29c	591	}
nixnax	146:a45f49a2b29c	592	if (v0) debugPrintf("\n");
nixnax	146:a45f49a2b29c	593	#endif
nixnax	163:d1b4328e9f08	594	int echoFound = !strncmp(ppp.udp->data,"echo ",5); // true if UDP message starts with "echo "
nixnax	163:d1b4328e9f08	595	int testFound = !strncmp(ppp.udp->data,"test" ,4); // true if UDP message starts with "test"
nixnax	146:a45f49a2b29c	596	if ( (echoFound) \|\| (testFound)) { // if the UDP message starts with "echo " or "test" we answer back
nixnax	147:0f40005cbc5f	597	swapIpAddresses(); // swap IP source and destination
nixnax	149:969d98f6fb88	598	swapIpPorts(); // swap IP source and destination ports
nixnax	146:a45f49a2b29c	599	if (echoFound) {
nixnax	163:d1b4328e9f08	600	memcpy(ppp.udp->data,"Got{",4); // in the UDP data modify "echo" to "Got:"
nixnax	146:a45f49a2b29c	601	char endString[] = "} UDP Server: PPP-Blinky\n"; // an appendix
nixnax	163:d1b4328e9f08	602	memcpy(ppp.udp->data+udpLength.data,endString,sizeof(endString)-1); // add endstring size to the UDP message
nixnax	163:d1b4328e9f08	603	udpLength.all = udpLength.data + sizeof(endString)-1; // update udp data size with the size of the appendix
nixnax	146:a45f49a2b29c	604	}
nixnax	146:a45f49a2b29c	605	if (testFound) {
nixnax	146:a45f49a2b29c	606	char udpResponse[50];
nixnax	146:a45f49a2b29c	607	int n = 0;
nixnax	146:a45f49a2b29c	608	n = n+sprintf(udpResponse+n,"Response count %d\n",ppp.responseCounter++);
nixnax	163:d1b4328e9f08	609	memcpy(ppp.udp->data,udpResponse,n); // copy response to the UDP data area
nixnax	163:d1b4328e9f08	610	udpLength.data = n; // update udp data size
nixnax	146:a45f49a2b29c	611	}
nixnax	163:d1b4328e9f08	612	// we may have changed data length, update all the lengths
nixnax	163:d1b4328e9f08	613	udpLength.all = udpLength.data+8; // update local udp packet length
nixnax	163:d1b4328e9f08	614	ipLength.all = ipLength.header + udpLength.all; // update IP Length
nixnax	163:d1b4328e9f08	615	ppp.ip->lengthR = __REV16(ipLength.all); // update IP length in buffer
nixnax	163:d1b4328e9f08	616	ppp.udp->lengthR = __REV16(udpLength.all); // update UDP length in buffer
nixnax	163:d1b4328e9f08	617	ppp.pkt.len = ipLength.all+2+4; // update ppp packet length
nixnax	164:c3de3d212c4b	618
nixnax	163:d1b4328e9f08	619	IpHeaderCheckSum(); // refresh IP header checksum
nixnax	163:d1b4328e9f08	620	ppp.udp->checkSumR = 0; // we don't yet recompute the UDP checksum (it's optional), so have to zero it
nixnax	165:c47826d07e0d	621	ppp.responseCounter++; // count UDP packet as a response
nixnax	146:a45f49a2b29c	622	sendPppFrame(); // send the UDP message back
nixnax	165:c47826d07e0d	623	} else {
nixnax	165:c47826d07e0d	624	// do nothing with other incoming UDP packets
nixnax	146:a45f49a2b29c	625	}
nixnax	142:54d1543e23e5	626	}
nixnax	142:54d1543e23e5	627
nixnax	142:54d1543e23e5	628	/// handle a PING ICMP (internet control message protocol) packet
nixnax	142:54d1543e23e5	629	void ICMPpacket() // internet control message protocol
nixnax	142:54d1543e23e5	630	{
nixnax	165:c47826d07e0d	631	struct {
nixnax	165:c47826d07e0d	632	unsigned int all; // length of entire ip packet
nixnax	165:c47826d07e0d	633	unsigned int header; // length of ip header
nixnax	165:c47826d07e0d	634	} ipLength;
nixnax	165:c47826d07e0d	635	struct {
nixnax	165:c47826d07e0d	636	unsigned int all; // length of entire udp packet
nixnax	165:c47826d07e0d	637	unsigned int data; // length of udp data segment
nixnax	165:c47826d07e0d	638	} icmpLength;
nixnax	165:c47826d07e0d	639
nixnax	165:c47826d07e0d	640	ipLength.all = __REV16( ppp.ip->lengthR ); // length of ip packet
nixnax	165:c47826d07e0d	641	ipLength.header = 4 * ppp.ip->headerLength; // length of ip header
nixnax	165:c47826d07e0d	642	ppp.icmpStart = ppp.ipStart + ipLength.header; // calculate start of udp header
nixnax	165:c47826d07e0d	643	icmpLength.all = ipLength.all - ipLength.header; // length of icmp packet
nixnax	165:c47826d07e0d	644	icmpLength.data = icmpLength.all - 8; // length of icmp data
nixnax	167:ff8a2d8beeb1	645
nixnax	142:54d1543e23e5	646	#define ICMP_TYPE_PING_REQUEST 8
nixnax	165:c47826d07e0d	647	if ( ppp.icmp->type == ICMP_TYPE_PING_REQUEST ) {
nixnax	165:c47826d07e0d	648	ppp.ip->ttl--; // decrement time to live (so we have to update header checksum)
nixnax	147:0f40005cbc5f	649	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	167:ff8a2d8beeb1	650	char * srcAdr = ppp.ip->srcAdrPtr;
nixnax	167:ff8a2d8beeb1	651	char * dstAdr = ppp.ip->dstAdrPtr;
nixnax	165:c47826d07e0d	652	int icmpIdent = __REV16( ppp.ip->identR ); // byte reversed - big endian
nixnax	165:c47826d07e0d	653	int icmpSequence = __REV16( ppp.icmp->sequenceR ); // byte reversed - big endian
nixnax	142:54d1543e23e5	654	if(1) {
nixnax	142:54d1543e23e5	655	char pbuf[50];
nixnax	142:54d1543e23e5	656	checkPc();
nixnax	142:54d1543e23e5	657	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	658	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	659	checkPc();
nixnax	142:54d1543e23e5	660	sprintf(pbuf, "Ident %04x Sequence %04d \n",icmpIdent,icmpSequence);
nixnax	142:54d1543e23e5	661	checkPc();
nixnax	142:54d1543e23e5	662	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	663	}
nixnax	142:54d1543e23e5	664	#endif
nixnax	147:0f40005cbc5f	665	swapIpAddresses(); // swap the IP source and destination addresses
nixnax	147:0f40005cbc5f	666	IpHeaderCheckSum(); // new ip header checksum (required because we changed TTL)
nixnax	142:54d1543e23e5	667	#define ICMP_TYPE_ECHO_REPLY 0
nixnax	165:c47826d07e0d	668	ppp.icmp->type = ICMP_TYPE_ECHO_REPLY; // icmp echo reply
nixnax	165:c47826d07e0d	669	ppp.icmp->checkSumR = 0; // zero the checksum for recalculation
nixnax	165:c47826d07e0d	670	unsigned int sum = dataCheckSum(ppp.icmpStart, icmpLength.all, 1); // icmp checksum
nixnax	165:c47826d07e0d	671	ppp.icmp->checkSumR = __REV16( sum ); // save big-endian icmp checksum
nixnax	142:54d1543e23e5	672
nixnax	165:c47826d07e0d	673	int printSize = icmpLength.data; // exclude size of icmp header
nixnax	142:54d1543e23e5	674	if (printSize > 10) printSize = 10; // print up to 20 characters
nixnax	142:54d1543e23e5	675	if (0) {
nixnax	142:54d1543e23e5	676	for (int i=0; i<printSize; i++) {
nixnax	165:c47826d07e0d	677	char ch = ppp.icmp->data[i];
nixnax	142:54d1543e23e5	678	if (ch>31 && ch<127) {
nixnax	142:54d1543e23e5	679	putcWhileCheckingInput(ch);
nixnax	142:54d1543e23e5	680	} else {
nixnax	142:54d1543e23e5	681	putcWhileCheckingInput('_');
nixnax	142:54d1543e23e5	682	}
nixnax	142:54d1543e23e5	683	}
nixnax	142:54d1543e23e5	684	putcWhileCheckingInput('\n');
nixnax	142:54d1543e23e5	685	}
nixnax	165:c47826d07e0d	686	ppp.responseCounter++; // count a ping as a response
nixnax	144:01d98cf7738e	687	sendPppFrame(); // reply to the ping
nixnax	142:54d1543e23e5	688	} else {
nixnax	142:54d1543e23e5	689	if (v0) {
nixnax	165:c47826d07e0d	690	debugPrintf("ICMP type=%x \n", ppp.icmp->type);
nixnax	142:54d1543e23e5	691	}
nixnax	142:54d1543e23e5	692	}
nixnax	142:54d1543e23e5	693	}
nixnax	142:54d1543e23e5	694
nixnax	142:54d1543e23e5	695	/// handle an IGMP (internet group managment protocol) packet (by ignoring it)
nixnax	142:54d1543e23e5	696	void IGMPpacket()
nixnax	142:54d1543e23e5	697	{
nixnax	142:54d1543e23e5	698	if (v0) debugPrintf("IGMP type=%d \n", ppp.pkt.buf[28]);
nixnax	142:54d1543e23e5	699	}
nixnax	142:54d1543e23e5	700
nixnax	142:54d1543e23e5	701	/// dump the header of an IP pakcet on the (optional) debug serial port
nixnax	142:54d1543e23e5	702	void dumpHeaderIP (int outGoing)
nixnax	142:54d1543e23e5	703	{
nixnax	142:54d1543e23e5	704	#if defined(IP_HEADER_DUMP_YES) && defined(SERIAL_PORT_MONITOR_YES)
nixnax	142:54d1543e23e5	705	checkPc(); // we are expecting the first character of the next packet
nixnax	155:9c6a1d249e26	706	int IPv4Id = __REV16(ppp.ip->identR);
nixnax	152:025c73b6c0a9	707	char pbuf[80]; // local print buffer
nixnax	142:54d1543e23e5	708	int n=0;
nixnax	142:54d1543e23e5	709	n=n+sprintf(pbuf+n, outGoing ? "\x1b[34m" : "\x1b[30m" ); // VT100 color code, print black for incoming, blue for outgoing headers
nixnax	142:54d1543e23e5	710	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	711	#define DUMP_FULL_IP_ADDRESS_YES
nixnax	142:54d1543e23e5	712	#ifdef DUMP_FULL_IP_ADDRESS_YES
nixnax	167:ff8a2d8beeb1	713	char * srcAdr = ppp.ip->srcAdrPtr;
nixnax	167:ff8a2d8beeb1	714	char * dstAdr = ppp.ip->dstAdrPtr;
nixnax	142:54d1543e23e5	715	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	716	#endif
nixnax	142:54d1543e23e5	717	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	718	#ifndef TCP_HEADER_DUMP_YES
nixnax	160:bd701ad564cb	719	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	720	#endif
nixnax	142:54d1543e23e5	721	#endif
nixnax	142:54d1543e23e5	722	}
nixnax	142:54d1543e23e5	723
nixnax	142:54d1543e23e5	724	/// dump a TCP header on the optional debug serial port
nixnax	142:54d1543e23e5	725	void dumpHeaderTCP(int outGoing)
nixnax	142:54d1543e23e5	726	{
nixnax	142:54d1543e23e5	727	#if defined(TCP_HEADER_DUMP_YES) && defined(SERIAL_PORT_MONITOR_YES)
nixnax	155:9c6a1d249e26	728	char flagString[9]; // text string presenting the 8 most important TCP flags
nixnax	142:54d1543e23e5	729	#define PRINT_ALL_TCP_FLAGS_YES
nixnax	142:54d1543e23e5	730	#ifdef PRINT_ALL_TCP_FLAGS_YES
nixnax	155:9c6a1d249e26	731	memset(flagString,'.', 8); // fill string with "........"
nixnax	156:163c23249731	732	if (ppp.tcp->flag.fin) flagString[7]='F';
nixnax	156:163c23249731	733	if (ppp.tcp->flag.syn) flagString[6]='S';
nixnax	156:163c23249731	734	if (ppp.tcp->flag.rst) flagString[5]='R';
nixnax	156:163c23249731	735	if (ppp.tcp->flag.psh) flagString[4]='P';
nixnax	156:163c23249731	736	if (ppp.tcp->flag.ack) flagString[3]='A';
nixnax	156:163c23249731	737	if (ppp.tcp->flag.urg) flagString[2]='U';
nixnax	156:163c23249731	738	if (ppp.tcp->flag.ece) flagString[1]='E';
nixnax	156:163c23249731	739	if (ppp.tcp->flag.cwr) flagString[0]='C';
nixnax	155:9c6a1d249e26	740	flagString[8]=0; // null terminate string
nixnax	142:54d1543e23e5	741	#else
nixnax	156:163c23249731	742	if (ppp.tcp->flag.ack) flagString[0]='A'; // choose only the most important flag to print
nixnax	156:163c23249731	743	if (ppp.tcp->flag.syn) flagString[0]='S';
nixnax	156:163c23249731	744	if (ppp.tcp->flag.fin) flagString[0]='F';
nixnax	156:163c23249731	745	if (ppp.tcp->flag.psh) flagString[0]='P';
nixnax	156:163c23249731	746	if (ppp.tcp->flag.rst) flagString[0]='R';
nixnax	155:9c6a1d249e26	747	flagString[1]=0; // null terminate string
nixnax	142:54d1543e23e5	748	#endif
nixnax	155:9c6a1d249e26	749	putsWhileCheckingInput( flagString );
nixnax	142:54d1543e23e5	750	#define EVERY_PACKET_ON_A_NEW_LINE_YES
nixnax	142:54d1543e23e5	751	#ifdef EVERY_PACKET_ON_A_NEW_LINE_YES
nixnax	142:54d1543e23e5	752	putsWhileCheckingInput("\x1b[30m\n"); // write a black color and newline after every packet
nixnax	160:bd701ad564cb	753	#else
nixnax	160:bd701ad564cb	754	putsWhileCheckingInput("\x1b[30m"); // write a black color after every packet
nixnax	142:54d1543e23e5	755	#endif
nixnax	156:163c23249731	756	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	757	putcWhileCheckingInput('\n'); // insert an extra new line to mark the end (except for final ack) of an HTTP conversation
nixnax	142:54d1543e23e5	758	}
nixnax	142:54d1543e23e5	759	#endif
nixnax	142:54d1543e23e5	760	}
nixnax	142:54d1543e23e5	761
nixnax	143:c5019f856a56	762	/// Encode a buffer in base-64
nixnax	142:54d1543e23e5	763	void enc64(char * in, char * out, int len)
nixnax	142:54d1543e23e5	764	{
nixnax	142:54d1543e23e5	765	const static char lut [] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
nixnax	142:54d1543e23e5	766	int i,j,a,b,c;
nixnax	142:54d1543e23e5	767	i=0;
nixnax	142:54d1543e23e5	768	j=0;
nixnax	142:54d1543e23e5	769	while(1) {
nixnax	142:54d1543e23e5	770	if (i<len) {
nixnax	142:54d1543e23e5	771	a = in[i++];
nixnax	142:54d1543e23e5	772	out[j++] = lut[ ( (a >> 2) & 0x3f) ];
nixnax	142:54d1543e23e5	773	} else break;
nixnax	142:54d1543e23e5	774	if (i<len) {
nixnax	142:54d1543e23e5	775	b = in[i++];
nixnax	142:54d1543e23e5	776	out[j++] = lut[ ( (a << 4) & 0x30) \| ( (b >> 4) & 0x0f) ];
nixnax	142:54d1543e23e5	777	out[j++] = lut[ ( (b << 2) & 0x3c) ];
nixnax	142:54d1543e23e5	778	} else out[j++] = '=';
nixnax	142:54d1543e23e5	779	if (i<len) {
nixnax	142:54d1543e23e5	780	c = in[i++];
nixnax	142:54d1543e23e5	781	j--;
nixnax	142:54d1543e23e5	782	out[j++] = lut[ ( (b << 2) & 0x3c) \| ( (c >> 6) & 0x03) ];
nixnax	142:54d1543e23e5	783	out[j++] = lut[ ( (c >> 0) & 0x3f) ];
nixnax	142:54d1543e23e5	784	} else out[j++] = '=';
nixnax	142:54d1543e23e5	785	}
nixnax	142:54d1543e23e5	786	out[j]=0;
nixnax	142:54d1543e23e5	787	}
nixnax	142:54d1543e23e5	788
nixnax	160:bd701ad564cb	789	/// Handle a request for an http websocket.
nixnax	160:bd701ad564cb	790	/// 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	791	int webSocketHandler(char * dataStart)
nixnax	142:54d1543e23e5	792	{
nixnax	142:54d1543e23e5	793	int n=0; // byte counter
nixnax	142:54d1543e23e5	794	char * key = strstr(dataStart, "Sec-WebSocket-Key: "); // search for the key in the payload
nixnax	142:54d1543e23e5	795	if (key != NULL) {
nixnax	142:54d1543e23e5	796	if (v0) putsWhileCheckingInput("WebSocket Request\n");
nixnax	142:54d1543e23e5	797	char challenge [70];
nixnax	142:54d1543e23e5	798	strncpy(challenge,key+19,70); // a local buffer
nixnax	142:54d1543e23e5	799	*strchr(challenge,'\r')=0; // insert null so we can use sprintf
nixnax	142:54d1543e23e5	800	strncat(challenge,"258EAFA5-E914-47DA-95CA-C5AB0DC85B11",70); // append websocket gui code
nixnax	142:54d1543e23e5	801	char shaOutput [20]; // sha1 output
nixnax	142:54d1543e23e5	802	sha1( shaOutput, challenge, strlen(challenge));
nixnax	142:54d1543e23e5	803	char encOut[50];
nixnax	142:54d1543e23e5	804	enc64( shaOutput, encOut, 20);
nixnax	142:54d1543e23e5	805	char * versionstring = strstr(dataStart, "Sec-WebSocket-Version:");
nixnax	142:54d1543e23e5	806	char * version = challenge;
nixnax	142:54d1543e23e5	807	strncpy(version, versionstring,70); // copy version string
nixnax	142:54d1543e23e5	808	*strchr(version,'\r')=0; // null terminate so we can sprintf it
nixnax	142:54d1543e23e5	809	memset(dataStart,0,500); // blank out old data befor send the websocket response header
nixnax	142:54d1543e23e5	810	n=n+sprintf(dataStart+n, "HTTP/1.1 101 Switching Protocols\r\n");
nixnax	142:54d1543e23e5	811	n=n+sprintf(dataStart+n, "Upgrade: websocket\r\n");
nixnax	142:54d1543e23e5	812	n=n+sprintf(dataStart+n, "Connection: Upgrade\r\n");
nixnax	142:54d1543e23e5	813	n=n+sprintf(dataStart+n, "Sec-WebSocket-Accept: %s\r\n",encOut);
nixnax	142:54d1543e23e5	814	n=n+sprintf(dataStart+n, "%s\r\n",version);
nixnax	142:54d1543e23e5	815	n=n+sprintf(dataStart+n, "mbed-Code: PPP-Blinky\r\n");
nixnax	142:54d1543e23e5	816	n=n+sprintf(dataStart+n, "\r\n"); // websocket response header ending
nixnax	142:54d1543e23e5	817	}
nixnax	142:54d1543e23e5	818	return n; // this response should satisfy a web browser's websocket protocol request
nixnax	142:54d1543e23e5	819	}
nixnax	142:54d1543e23e5	820
nixnax	142:54d1543e23e5	821	#define TCP_FLAG_ACK (1<<4)
nixnax	142:54d1543e23e5	822	#define TCP_FLAG_SYN (1<<1)
nixnax	142:54d1543e23e5	823	#define TCP_FLAG_PSH (1<<3)
nixnax	142:54d1543e23e5	824	#define TCP_FLAG_RST (1<<2)
nixnax	142:54d1543e23e5	825	#define TCP_FLAG_FIN (1<<0)
nixnax	142:54d1543e23e5	826
nixnax	142:54d1543e23e5	827	/// respond to an HTTP request
nixnax	142:54d1543e23e5	828	int httpResponse(char * dataStart)
nixnax	142:54d1543e23e5	829	{
nixnax	142:54d1543e23e5	830	int n=0; // number of bytes we have printed so far
nixnax	142:54d1543e23e5	831	n = webSocketHandler( dataStart ); // test for and handle WebSocket upgrade requests
nixnax	160:bd701ad564cb	832	if (n>0) return n; // if n>0 we already have a response, so return
nixnax	142:54d1543e23e5	833
nixnax	142:54d1543e23e5	834	int nHeader; // byte size of HTTP header
nixnax	142:54d1543e23e5	835	int contentLengthStart; // index where HTML starts
nixnax	142:54d1543e23e5	836	int httpGet5,httpGet6,httpGetx, httpGetRoot; // temporary storage of strncmp results
nixnax	142:54d1543e23e5	837
nixnax	146:a45f49a2b29c	838	ppp.responseCounter++; // increment the number of frames we have made
nixnax	142:54d1543e23e5	839
nixnax	142:54d1543e23e5	840	httpGetRoot = strncmp(dataStart, "GET / HTTP/1.", 13); // found a GET to the root directory
nixnax	142:54d1543e23e5	841	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	842	httpGet5 = dataStart[5]; // the first character in the path name, we use it for special functions later on
nixnax	142:54d1543e23e5	843	httpGet6 = dataStart[6]; // the second character in the path name, we use it for special functions later on
nixnax	142:54d1543e23e5	844	// for example, you could try this using netcat (nc): echo "GET /x" \| nc 172.10.10.2
nixnax	142:54d1543e23e5	845	if( (httpGetRoot==0) \|\| (httpGetx==0) ) {
nixnax	142:54d1543e23e5	846	n=n+sprintf(n+dataStart,"HTTP/1.1 200 OK\r\nServer: mbed-PPP-Blinky-v1\r\n"); // 200 OK header
nixnax	142:54d1543e23e5	847	} else {
nixnax	142:54d1543e23e5	848	n=n+sprintf(n+dataStart,"HTTP/1.1 404 Not Found\r\nServer: mbed-PPP-Blinky\r\n"); // 404 header
nixnax	142:54d1543e23e5	849	}
nixnax	142:54d1543e23e5	850	n=n+sprintf(n+dataStart,"Content-Length: "); // http header
nixnax	142:54d1543e23e5	851	contentLengthStart = n; // remember where Content-Length is in buffer
nixnax	142:54d1543e23e5	852	n=n+sprintf(n+dataStart,"?????\r\n"); // leave five spaces for content length - will be updated later
nixnax	142:54d1543e23e5	853	n=n+sprintf(n+dataStart,"Connection: close\r\n"); // close connection immediately
nixnax	142:54d1543e23e5	854	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	855	nHeader=n; // size of HTTP header
nixnax	142:54d1543e23e5	856	if( httpGetRoot == 0 ) {
nixnax	142:54d1543e23e5	857	// this is where we insert our web page into the buffer
nixnax	142:54d1543e23e5	858	memcpy(n+dataStart,rootWebPage,sizeof(rootWebPage));
nixnax	142:54d1543e23e5	859	n = n + sizeof(rootWebPage)-1; // one less than sizeof because we don't count the null byte at the end
nixnax	142:54d1543e23e5	860	} else if ( (httpGet5 == 'w') && (httpGet6 == 's') ) { // "ws" is a special page for websocket demo
nixnax	142:54d1543e23e5	861	memcpy(n+dataStart,webSocketPage,sizeof(webSocketPage));
nixnax	142:54d1543e23e5	862	n = n + sizeof(webSocketPage)-1; // one less than size
nixnax	142:54d1543e23e5	863	} else {
nixnax	142:54d1543e23e5	864	if (httpGetx == 0) { // the page request started with "GET /x" - here we treat anything starting with /x special:
nixnax	142:54d1543e23e5	865
nixnax	142:54d1543e23e5	866	#define W3C_COMPLIANT_RESPONSE_NO
nixnax	142:54d1543e23e5	867	// change the above to W3C_COMPLIANT_RESPONSE_YES if you want a W3C.org compliant HTTP response
nixnax	142:54d1543e23e5	868	#ifdef W3C_COMPLIANT_RESPONSE_YES
nixnax	142:54d1543e23e5	869	n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (W3C.org required elements)
nixnax	146:a45f49a2b29c	870	n=n+sprintf(n+dataStart,"<body>%d</body>",ppp.responseCounter); // body = the http frame count
nixnax	142:54d1543e23e5	871	#else
nixnax	142:54d1543e23e5	872	if( httpGet6 == 'b' ) { // if the fetched page is "xb" send a meta command to let the browser continuously reload
nixnax	167:ff8a2d8beeb1	873	n=n+sprintf(n+dataStart, "<meta http-equiv=\"refresh\" content=\"0\">"); // reload loop - handy for benchmarking
nixnax	142:54d1543e23e5	874	}
nixnax	142:54d1543e23e5	875	// /x is a very short page, in fact, it is only a decimal number showing the http Page count
nixnax	146:a45f49a2b29c	876	n=n+sprintf(n+dataStart,"%d ",ppp.responseCounter); // not really valid html but most browsers and curl are ok with it
nixnax	142:54d1543e23e5	877	#endif
nixnax	142:54d1543e23e5	878	} else {
nixnax	142:54d1543e23e5	879	// all other requests get 404 Not Found response with a http frame count - nice for debugging
nixnax	142:54d1543e23e5	880	n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (required element)
nixnax	142:54d1543e23e5	881	n=n+sprintf(n+dataStart,"<body>Not Found</body>"); // not found message
nixnax	142:54d1543e23e5	882	}
nixnax	142:54d1543e23e5	883	}
nixnax	142:54d1543e23e5	884	#define CONTENTLENGTHSIZE 5
nixnax	142:54d1543e23e5	885	char contentLengthString[CONTENTLENGTHSIZE+1];
nixnax	142:54d1543e23e5	886	snprintf(contentLengthString,CONTENTLENGTHSIZE+1,"%*d",CONTENTLENGTHSIZE,n-nHeader); // print Content-Length with leading spaces and fixed width equal to csize
nixnax	142:54d1543e23e5	887	memcpy(dataStart+contentLengthStart, contentLengthString, CONTENTLENGTHSIZE); // copy Content-Length to it's place in the send buffer
nixnax	142:54d1543e23e5	888	return n; // total byte size of our response
nixnax	142:54d1543e23e5	889	}
nixnax	142:54d1543e23e5	890
nixnax	160:bd701ad564cb	891	/// Handle TCP data that is not an HTTP GET.
nixnax	160:bd701ad564cb	892	/// This is handy when for example you want to use netcat (nc.exe) to talk to PPP-Blinky.
nixnax	160:bd701ad564cb	893	/// This could also be a websocket receive event - especially if the first byte is 0x81 (websocket data push)
nixnax	142:54d1543e23e5	894	int tcpResponse(char * dataStart, int len, int * outFlags)
nixnax	142:54d1543e23e5	895	{
nixnax	142:54d1543e23e5	896	int n=0; // number of bytes we have printed so far
nixnax	142:54d1543e23e5	897	if (dataStart[0] == 0x81) { // check if this is a websocket push message
nixnax	160:bd701ad564cb	898	char mask [4];
nixnax	160:bd701ad564cb	899	memcpy ( mask, dataStart+2, 4); // websocket messages are "masked", so first we obtain the 4-byte mask
nixnax	160:bd701ad564cb	900	int websocketMessageSize = len - 6; // 1 byte prefix (0x81), 1 byte, 4 bytes mask = 6 bytes
nixnax	160:bd701ad564cb	901	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	902	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	903	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	904	memcpy(dataStart+2, "Got:",4); // insert our own text into the four mask bytes
nixnax	160:bd701ad564cb	905	n = len; // our response size remains exactly the same length as what we received
nixnax	142:54d1543e23e5	906	} else if ( (dataStart[0]==0x88) && (dataStart[1]==0x80) && (len == 6) ) { // test for a websocket close request
nixnax	142:54d1543e23e5	907	n=2; // our close command is only two bytes long because we don't use the four mask bytes
nixnax	142:54d1543e23e5	908	dataStart[1]=0; // we don't have mask bytes on
nixnax	160:bd701ad564cb	909	} else {
nixnax	160:bd701ad564cb	910	if (v1) putsWhileCheckingInput("TCP data received\n"); // all other tcp push packets
nixnax	163:d1b4328e9f08	911	}
nixnax	142:54d1543e23e5	912	return n; // total byte size of our response
nixnax	142:54d1543e23e5	913	}
nixnax	142:54d1543e23e5	914
nixnax	142:54d1543e23e5	915	/// handle an incoming TCP packet
nixnax	142:54d1543e23e5	916	/// 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	917	void tcpHandler()
nixnax	142:54d1543e23e5	918	{
nixnax	142:54d1543e23e5	919	// IP header
nixnax	154:18b2bd92f557	920	int packetLengthIp = __REV16(ppp.ip->lengthR ); // size of ip packet
nixnax	154:18b2bd92f557	921	int headerSizeIp = 4 * ppp.ip->headerLength; // size of ip header
nixnax	142:54d1543e23e5	922
nixnax	142:54d1543e23e5	923	// TCP header
nixnax	160:bd701ad564cb	924
nixnax	155:9c6a1d249e26	925	ppp.tcpStart = ppp.ipStart + headerSizeIp; // calculate where the TCP header starts
nixnax	154:18b2bd92f557	926	int tcpSize = packetLengthIp - headerSizeIp; // tcp size = size of ip payload
nixnax	160:bd701ad564cb	927	char * tcp = ppp.ipStart+headerSizeIp; // calculate start of tcp packet
nixnax	142:54d1543e23e5	928
nixnax	154:18b2bd92f557	929	int headerSizeTcp = 4 * (ppp.tcp->offset); // tcp "offset" for start of data is also the header size
nixnax	152:025c73b6c0a9	930
nixnax	154:18b2bd92f557	931	char * tcpDataIn = tcp + headerSizeTcp; // start of data block after TCP header
nixnax	154:18b2bd92f557	932	int tcpDataSize = tcpSize - headerSizeTcp; // size of data block after TCP header
nixnax	154:18b2bd92f557	933
nixnax	154:18b2bd92f557	934	unsigned int seq_in = __REV(ppp.tcp->seqTcpR);
nixnax	154:18b2bd92f557	935	unsigned int ack_in = __REV(ppp.tcp->ackTcpR);
nixnax	142:54d1543e23e5	936	unsigned int ack_out = seq_in + tcpDataSize;
nixnax	142:54d1543e23e5	937	unsigned int seq_out = ack_in; // use their version of our current sequence number
nixnax	142:54d1543e23e5	938
nixnax	142:54d1543e23e5	939	// first we shorten the TCP response header to only 20 bytes. This means we ignore all TCP option requests
nixnax	142:54d1543e23e5	940	tcpSize = 20; // shorten total TCP packet size to 20 bytes (no data)
nixnax	154:18b2bd92f557	941	headerSizeTcp = 20; // shorten outgoing TCP header size 20 bytes
nixnax	154:18b2bd92f557	942	ppp.ip->headerLength = 5; // ip header is 20 bytes long
nixnax	154:18b2bd92f557	943	ppp.tcp->offset = (headerSizeTcp/4);
nixnax	154:18b2bd92f557	944	ppp.ip->lengthR = __REV(40);
nixnax	154:18b2bd92f557	945	char * tcpDataOut = tcp + 20; // start of outgoing data
nixnax	154:18b2bd92f557	946
nixnax	154:18b2bd92f557	947	ppp.ip->lengthR = __REV16(40);
nixnax	142:54d1543e23e5	948
nixnax	142:54d1543e23e5	949	int dataLen = 0; // most of our responses will have zero TCP data, only a header
nixnax	142:54d1543e23e5	950	int flagsOut = TCP_FLAG_ACK; // the default case is an ACK packet
nixnax	155:9c6a1d249e26	951	//int flagsTCP = ((flagbitstcp[0]&1)<<8)\|flagbitstcp[1]; // the tcp flags we received
nixnax	160:bd701ad564cb	952
nixnax	159:4d1bf96a59cd	953	ppp.tcp->windowR = __REV16( 700 ); // set tcp window size to 700 bytes
nixnax	142:54d1543e23e5	954
nixnax	142:54d1543e23e5	955	// A sparse TCP flag interpreter that implements stateless TCP connections
nixnax	142:54d1543e23e5	956
nixnax	156:163c23249731	957	switch ( ppp.tcp->flag.All ) {
nixnax	158:841592aed956	958	case TCP_FLAG_ACK: // handle ack messages by ignoring them
nixnax	142:54d1543e23e5	959	return;
nixnax	142:54d1543e23e5	960	case TCP_FLAG_SYN:
nixnax	142:54d1543e23e5	961	flagsOut = TCP_FLAG_SYN \| TCP_FLAG_ACK; // something wants to connect - acknowledge it
nixnax	142:54d1543e23e5	962	seq_out = seq_in+0x10000000U; // create a new sequence number using their sequence as a starting point, increase the highest digit
nixnax	142:54d1543e23e5	963	ack_out++; // for SYN flag we have to increase the sequence by 1
nixnax	142:54d1543e23e5	964	break;
nixnax	142:54d1543e23e5	965	case TCP_FLAG_ACK \| TCP_FLAG_PSH:
nixnax	142:54d1543e23e5	966	if ( (strncmp(tcpDataIn, "GET /", 5) == 0) ) { // check for an http GET command
nixnax	142:54d1543e23e5	967	flagsOut = TCP_FLAG_ACK \| TCP_FLAG_PSH; // set outgoing FIN flag to ask them to close from their side
nixnax	142:54d1543e23e5	968	dataLen = httpResponse(tcpDataOut); // send an http response
nixnax	142:54d1543e23e5	969	} else {
nixnax	158:841592aed956	970	dataLen = tcpResponse(tcpDataOut,tcpDataSize, &flagsOut); // not an http GET, handle as a tcp connection
nixnax	142:54d1543e23e5	971	}
nixnax	142:54d1543e23e5	972	break;
nixnax	142:54d1543e23e5	973	case TCP_FLAG_FIN:
nixnax	142:54d1543e23e5	974	case TCP_FLAG_FIN \| TCP_FLAG_ACK:
nixnax	142:54d1543e23e5	975	case TCP_FLAG_FIN \| TCP_FLAG_PSH \| TCP_FLAG_ACK:
nixnax	142:54d1543e23e5	976	flagsOut = TCP_FLAG_ACK \| TCP_FLAG_FIN; // set outgoing FIN flag to ask them to close from their side
nixnax	142:54d1543e23e5	977	ack_out++; // for FIN flag we have to increase the sequence by 1
nixnax	142:54d1543e23e5	978	break;
nixnax	142:54d1543e23e5	979	default:
nixnax	142:54d1543e23e5	980	return; // ignore remaining packets
nixnax	142:54d1543e23e5	981	} // switch
nixnax	142:54d1543e23e5	982
nixnax	142:54d1543e23e5	983	// The TCP flag handling is now done
nixnax	142:54d1543e23e5	984	// first we swap source and destination TCP addresses and insert the new ack and seq numbers
nixnax	147:0f40005cbc5f	985	swapIpAddresses(); // swap IP source and destination addresses
nixnax	149:969d98f6fb88	986	swapIpPorts(); // swap IP source and destination ports
nixnax	142:54d1543e23e5	987
nixnax	158:841592aed956	988	ppp.tcp->ackTcpR = __REV( ack_out ); // byte reversed - tcp/ip messages are big-endian (high byte first)
nixnax	158:841592aed956	989	ppp.tcp->seqTcpR = __REV( seq_out ); // byte reversed - tcp/ip messages are big-endian (high byte first)
nixnax	160:bd701ad564cb	990
nixnax	156:163c23249731	991	ppp.tcp->flag.All = flagsOut; // update the TCP flags
nixnax	142:54d1543e23e5	992
nixnax	159:4d1bf96a59cd	993	// recalculate all the header sizes
nixnax	154:18b2bd92f557	994	tcpSize = headerSizeTcp + dataLen; // tcp packet size
nixnax	154:18b2bd92f557	995	int newPacketSize = headerSizeIp + tcpSize; // calculate size of the outgoing packet
nixnax	159:4d1bf96a59cd	996	ppp.ip->lengthR = __REV16 ( newPacketSize );
nixnax	142:54d1543e23e5	997	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	998
nixnax	142:54d1543e23e5	999	// the header is all set up, now do the IP and TCP checksums
nixnax	146:a45f49a2b29c	1000	IpHeaderCheckSum(); // calculate new IP header checksum
nixnax	142:54d1543e23e5	1001
nixnax	159:4d1bf96a59cd	1002	// create the TCP "pseudo-header" (containing some IP header values) in order to correctly calculate the TCP checksum
nixnax	142:54d1543e23e5	1003	// 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	1004	pseudoIpHeaderType pseudoHeader; // create pseudo header
nixnax	159:4d1bf96a59cd	1005	pseudoHeader.srcAdrR = ppp.ip->srcAdrR; // copy in ip source address
nixnax	159:4d1bf96a59cd	1006	pseudoHeader.dstAdrR = ppp.ip->dstAdrR; // copy in ip dest address
nixnax	159:4d1bf96a59cd	1007	pseudoHeader.zero = 0; // padding
nixnax	160:bd701ad564cb	1008	pseudoHeader.protocol = ppp.ip->protocol; // protocol number
nixnax	159:4d1bf96a59cd	1009	pseudoHeader.lengthR = __REV16( tcpSize ); // size of tcp packet
nixnax	159:4d1bf96a59cd	1010	dataCheckSum(pseudoHeader.start, 12, 1); // start with the TCP checksum of the pseudoheader
nixnax	159:4d1bf96a59cd	1011	ppp.tcp->checksumR = 0; // before TCP checksum calculations the checksum bytes must be set cleared
nixnax	161:d59f778bc8ab	1012	unsigned int pseudoHeaderSum=dataCheckSum(ppp.tcpStart,tcpSize, 0); // continue the TCP checksum on the whole TCP packet
nixnax	159:4d1bf96a59cd	1013	ppp.tcp->checksumR = __REV16( pseudoHeaderSum); // tcp checksum done, store it in the TCP header
nixnax	160:bd701ad564cb	1014
nixnax	142:54d1543e23e5	1015	dumpHeaderIP(1); // dump outgoing IP header
nixnax	142:54d1543e23e5	1016	dumpHeaderTCP(1); // dump outgoing TCP header
nixnax	142:54d1543e23e5	1017	for (int i=0; i<45*1000/10; i++) { // 45 ms delay before sending frame - a typical internet delay time
nixnax	142:54d1543e23e5	1018	checkPc(); // catch any incoming characters
nixnax	142:54d1543e23e5	1019	wait_us(10); // wait less than 1 character duration at 115200
nixnax	142:54d1543e23e5	1020	}
nixnax	144:01d98cf7738e	1021	sendPppFrame(); // All preparation complete - send the TCP response
nixnax	142:54d1543e23e5	1022	if(0) dumpPPPFrame(); // set to 1 to dump transmitted ppp frame
nixnax	142:54d1543e23e5	1023	memset(ppp.pkt.buf+44,0,500); // flush out traces of previous data that we may scan for
nixnax	142:54d1543e23e5	1024	}
nixnax	142:54d1543e23e5	1025
nixnax	142:54d1543e23e5	1026	/// dump the TCP data to the debug serial port
nixnax	142:54d1543e23e5	1027	void dumpDataTCP()
nixnax	142:54d1543e23e5	1028	{
nixnax	142:54d1543e23e5	1029	int ipPktLen = (ppp.pkt.buf[6]<<8)\|ppp.pkt.buf[7]; // overall length of ip packet
nixnax	142:54d1543e23e5	1030	int ipHeaderLen = (ppp.pkt.buf[4]&0xf)*4; // length of ip header
nixnax	154:18b2bd92f557	1031	int headerSizeTcp = ((ppp.pkt.buf[4+ipHeaderLen+12]>>4)&0xf)*4;; // length of tcp header
nixnax	154:18b2bd92f557	1032	int dataLen = ipPktLen - ipHeaderLen - headerSizeTcp; // data is what's left after the two headers
nixnax	142:54d1543e23e5	1033	if (v1) {
nixnax	142:54d1543e23e5	1034	char pbuf[50]; // local print buffer
nixnax	142:54d1543e23e5	1035	checkPc();
nixnax	154:18b2bd92f557	1036	sprintf(pbuf, "TCP %d ipHeader %d tcpHeader %d Data %d\n", ipPktLen, ipHeaderLen, headerSizeTcp, dataLen); // 1 for more verbose
nixnax	142:54d1543e23e5	1037	checkPc();
nixnax	142:54d1543e23e5	1038	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	1039	}
nixnax	142:54d1543e23e5	1040	if (dataLen > 0) {
nixnax	154:18b2bd92f557	1041	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	1042	putsWhileCheckingInput( ppp.pkt.buf+4+ipHeaderLen+headerSizeTcp ); // print the tcp payload data
nixnax	142:54d1543e23e5	1043	putsWhileCheckingInput("\n");
nixnax	142:54d1543e23e5	1044	}
nixnax	142:54d1543e23e5	1045	}
nixnax	142:54d1543e23e5	1046
nixnax	142:54d1543e23e5	1047	/// handle an incoming TCP packet
nixnax	142:54d1543e23e5	1048	void TCPpacket()
nixnax	142:54d1543e23e5	1049	{
nixnax	142:54d1543e23e5	1050	dumpHeaderIP(0); // dump incoming packet header
nixnax	142:54d1543e23e5	1051	dumpHeaderTCP(0); // dump incoming packet header
nixnax	142:54d1543e23e5	1052	if (v2) dumpDataTCP();
nixnax	142:54d1543e23e5	1053	tcpHandler();
nixnax	142:54d1543e23e5	1054	}
nixnax	142:54d1543e23e5	1055
nixnax	142:54d1543e23e5	1056	/// handle the remaining IP protocols by ignoring them
nixnax	142:54d1543e23e5	1057	void otherProtocol()
nixnax	142:54d1543e23e5	1058	{
nixnax	142:54d1543e23e5	1059	debugPrintf("Other IP protocol");
nixnax	142:54d1543e23e5	1060	}
nixnax	142:54d1543e23e5	1061
nixnax	142:54d1543e23e5	1062	/// process an incoming IP packet
nixnax	142:54d1543e23e5	1063	void IPframe()
nixnax	142:54d1543e23e5	1064	{
nixnax	167:ff8a2d8beeb1	1065	int protocol = ppp.ip->protocol;
nixnax	142:54d1543e23e5	1066	switch (protocol) {
nixnax	142:54d1543e23e5	1067	case 1:
nixnax	142:54d1543e23e5	1068	ICMPpacket();
nixnax	142:54d1543e23e5	1069	break;
nixnax	142:54d1543e23e5	1070	case 2:
nixnax	142:54d1543e23e5	1071	IGMPpacket();
nixnax	142:54d1543e23e5	1072	break;
nixnax	142:54d1543e23e5	1073	case 17:
nixnax	142:54d1543e23e5	1074	UDPpacket();
nixnax	142:54d1543e23e5	1075	break;
nixnax	142:54d1543e23e5	1076	case 6:
nixnax	142:54d1543e23e5	1077	TCPpacket();
nixnax	142:54d1543e23e5	1078	break;
nixnax	142:54d1543e23e5	1079	default:
nixnax	142:54d1543e23e5	1080	otherProtocol();
nixnax	142:54d1543e23e5	1081	}
nixnax	142:54d1543e23e5	1082	}
nixnax	142:54d1543e23e5	1083
nixnax	142:54d1543e23e5	1084	/// respond to LCP (line configuration protocol) configuration request) by allowing no options
nixnax	142:54d1543e23e5	1085	void LCPconfReq()
nixnax	142:54d1543e23e5	1086	{
nixnax	142:54d1543e23e5	1087	debugPrintf("LCP Config ");
nixnax	142:54d1543e23e5	1088	if (ppp.pkt.buf[7] != 4) {
nixnax	142:54d1543e23e5	1089	ppp.pkt.buf[4]=4; // allow only "no options" which means Maximum Receive Unit (MRU) is default 1500 bytes
nixnax	142:54d1543e23e5	1090	debugPrintf("Reject\n");
nixnax	144:01d98cf7738e	1091	sendPppFrame();
nixnax	142:54d1543e23e5	1092	} else {
nixnax	142:54d1543e23e5	1093	ppp.pkt.buf[4]=2; // ack zero conf
nixnax	142:54d1543e23e5	1094	debugPrintf("Ack\n");
nixnax	144:01d98cf7738e	1095	sendPppFrame();
nixnax	142:54d1543e23e5	1096	debugPrintf("LCP Ask\n");
nixnax	142:54d1543e23e5	1097	ppp.pkt.buf[4]=1; // request no options
nixnax	144:01d98cf7738e	1098	sendPppFrame();
nixnax	142:54d1543e23e5	1099	}
nixnax	142:54d1543e23e5	1100	}
nixnax	142:54d1543e23e5	1101
nixnax	142:54d1543e23e5	1102	/// handle LCP acknowledge packets by ignoring them
nixnax	142:54d1543e23e5	1103	void LCPconfAck()
nixnax	142:54d1543e23e5	1104	{
nixnax	142:54d1543e23e5	1105	debugPrintf("LCP Ack\n");
nixnax	142:54d1543e23e5	1106	}
nixnax	142:54d1543e23e5	1107
nixnax	143:c5019f856a56	1108	/// handle LCP end (disconnect) packets by acknowledging them and by setting ppp.online to false
nixnax	142:54d1543e23e5	1109	void LCPend()
nixnax	142:54d1543e23e5	1110	{
nixnax	142:54d1543e23e5	1111	ppp.pkt.buf[4]=6;
nixnax	144:01d98cf7738e	1112	sendPppFrame(); // acknowledge
nixnax	142:54d1543e23e5	1113	ppp.online=0; // start hunting for connect string again
nixnax	142:54d1543e23e5	1114	pppInitStruct(); // flush the receive buffer
nixnax	143:c5019f856a56	1115	debugPrintf("LCP End (Disconnect from host)\n");
nixnax	142:54d1543e23e5	1116	}
nixnax	142:54d1543e23e5	1117
nixnax	142:54d1543e23e5	1118	/// respond to other LCP requests by ignoring them
nixnax	142:54d1543e23e5	1119	void LCPother()
nixnax	142:54d1543e23e5	1120	{
nixnax	142:54d1543e23e5	1121	debugPrintf("LCP Other\n");
nixnax	142:54d1543e23e5	1122	dumpPPPFrame();
nixnax	142:54d1543e23e5	1123	}
nixnax	142:54d1543e23e5	1124
nixnax	142:54d1543e23e5	1125	/// process incoming LCP packets
nixnax	142:54d1543e23e5	1126	void LCPframe()
nixnax	142:54d1543e23e5	1127	{
nixnax	142:54d1543e23e5	1128	int code = ppp.pkt.buf[4];
nixnax	142:54d1543e23e5	1129	switch (code) {
nixnax	142:54d1543e23e5	1130	case 1:
nixnax	142:54d1543e23e5	1131	LCPconfReq();
nixnax	142:54d1543e23e5	1132	break; // config request
nixnax	142:54d1543e23e5	1133	case 2:
nixnax	142:54d1543e23e5	1134	LCPconfAck();
nixnax	142:54d1543e23e5	1135	break; // config ack
nixnax	142:54d1543e23e5	1136	case 5:
nixnax	142:54d1543e23e5	1137	LCPend();
nixnax	142:54d1543e23e5	1138	break; // end connection
nixnax	142:54d1543e23e5	1139	default:
nixnax	142:54d1543e23e5	1140	LCPother();
nixnax	142:54d1543e23e5	1141	}
nixnax	142:54d1543e23e5	1142	}
nixnax	142:54d1543e23e5	1143
nixnax	142:54d1543e23e5	1144	/// discard packets that are not IP, IPCP, or LCP
nixnax	142:54d1543e23e5	1145	void discardedFrame()
nixnax	142:54d1543e23e5	1146	{
nixnax	142:54d1543e23e5	1147	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	1148	}
nixnax	142:54d1543e23e5	1149
nixnax	142:54d1543e23e5	1150	/// determine the packet type (IP, IPCP or LCP) of incoming packets
nixnax	142:54d1543e23e5	1151	void determinePacketType()
nixnax	142:54d1543e23e5	1152	{
nixnax	167:ff8a2d8beeb1	1153	if ( ppp.ppp->address != 0xff ) {
nixnax	167:ff8a2d8beeb1	1154	debugPrintf("Unexpected: PPP address != ff\n");
nixnax	142:54d1543e23e5	1155	return;
nixnax	142:54d1543e23e5	1156	}
nixnax	167:ff8a2d8beeb1	1157	if ( ppp.ppp->control != 3 ) {
nixnax	167:ff8a2d8beeb1	1158	debugPrintf("Unexpected: PPP control != 3\n");
nixnax	142:54d1543e23e5	1159	return;
nixnax	142:54d1543e23e5	1160	}
nixnax	167:ff8a2d8beeb1	1161	unsigned int protocol = __REV16( ppp.ppp->protocolR );
nixnax	167:ff8a2d8beeb1	1162	switch ( protocol ) {
nixnax	167:ff8a2d8beeb1	1163	case 0xc021:
nixnax	142:54d1543e23e5	1164	LCPframe();
nixnax	142:54d1543e23e5	1165	break; // link control
nixnax	167:ff8a2d8beeb1	1166	case 0x8021:
nixnax	142:54d1543e23e5	1167	IPCPframe();
nixnax	142:54d1543e23e5	1168	break; // IP control
nixnax	167:ff8a2d8beeb1	1169	case 0x0021:
nixnax	142:54d1543e23e5	1170	IPframe();
nixnax	142:54d1543e23e5	1171	break; // IP itself
nixnax	142:54d1543e23e5	1172	default:
nixnax	142:54d1543e23e5	1173	discardedFrame();
nixnax	142:54d1543e23e5	1174	}
nixnax	142:54d1543e23e5	1175	}
nixnax	142:54d1543e23e5	1176
nixnax	146:a45f49a2b29c	1177	/// a sniffer tool to assist in figuring out where in the code we are having characters in the input buffer
nixnax	146:a45f49a2b29c	1178	void sniff()
nixnax	146:a45f49a2b29c	1179	{
nixnax	146:a45f49a2b29c	1180	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	1181	}
nixnax	146:a45f49a2b29c	1182
nixnax	142:54d1543e23e5	1183	/// scan the PPP serial input stream for frame start markers
nixnax	143:c5019f856a56	1184	void waitForPppFrame()
nixnax	142:54d1543e23e5	1185	{
nixnax	142:54d1543e23e5	1186	while(1) {
nixnax	142:54d1543e23e5	1187	checkPc(); // handle received characters
nixnax	142:54d1543e23e5	1188	if ( ppp.rx.head != ppp.rx.tail ) {
nixnax	142:54d1543e23e5	1189	int oldTail = ppp.rx.tail; // remember where the character is located in the buffer
nixnax	142:54d1543e23e5	1190	int rx = pc_getBuf(); // get the character
nixnax	142:54d1543e23e5	1191	if (rx==FRAME_7E) {
nixnax	142:54d1543e23e5	1192	if (ppp.firstFrame) { // is this the start of the first frame start
nixnax	142:54d1543e23e5	1193	ppp.firstFrame=0;
nixnax	142:54d1543e23e5	1194	ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
nixnax	142:54d1543e23e5	1195	ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where first frame started
nixnax	142:54d1543e23e5	1196	} else {
nixnax	142:54d1543e23e5	1197	ppp.hdlc.frameEndIndex=oldTail; // mark the frame end character
nixnax	142:54d1543e23e5	1198	processPPPFrame(ppp.hdlc.frameStartIndex, ppp.hdlc.frameEndIndex); // process the frame
nixnax	142:54d1543e23e5	1199	ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
nixnax	142:54d1543e23e5	1200	ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where next frame started
nixnax	142:54d1543e23e5	1201	break;
nixnax	142:54d1543e23e5	1202	}
nixnax	142:54d1543e23e5	1203	}
nixnax	142:54d1543e23e5	1204	}
nixnax	142:54d1543e23e5	1205	}
nixnax	142:54d1543e23e5	1206	}
nixnax	142:54d1543e23e5	1207
nixnax	153:7993def8663f	1208	/// 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	1209	// Note: a 0x7E in the input stream (ppp start of frame character) will also set ppp.online to true - see checkPc();
nixnax	153:7993def8663f	1210	void waitForPcConnectString()
nixnax	142:54d1543e23e5	1211	{
nixnax	142:54d1543e23e5	1212	while(ppp.online == 0) {
nixnax	142:54d1543e23e5	1213	checkPc(); // gather received characters
nixnax	142:54d1543e23e5	1214	// search for Windows Dialup Networking "Direct Connection Between Two Computers" expected connect string
nixnax	142:54d1543e23e5	1215	char * found1 = strstr( (char *)ppp.rx.buf, "CLIENT" );
nixnax	142:54d1543e23e5	1216	if (found1 != NULL) {
nixnax	142:54d1543e23e5	1217	// respond with Windows Dialup networking expected "Direct Connection Between Two Computers" response string
nixnax	143:c5019f856a56	1218	if (v0) debugPrintf("Connected: Found connect string \"CLIENT\", sent \"CLIENTSERVER\"\n");
nixnax	142:54d1543e23e5	1219	pc.puts("CLIENTSERVER");
nixnax	142:54d1543e23e5	1220	ppp.online=1; // we are connected - set flag so we stop looking for the connect string
nixnax	142:54d1543e23e5	1221	checkPc();
nixnax	142:54d1543e23e5	1222	}
nixnax	142:54d1543e23e5	1223	}
nixnax	142:54d1543e23e5	1224	}
nixnax	142:54d1543e23e5	1225
nixnax	144:01d98cf7738e	1226	/// Initialize PPP data structure and set serial port(s) baud rate(s)
nixnax	144:01d98cf7738e	1227	void initializePpp()
nixnax	142:54d1543e23e5	1228	{
nixnax	142:54d1543e23e5	1229	pc.baud(115200); // USB serial port to pc
nixnax	144:01d98cf7738e	1230	debugBaudRate(115200); // baud rate for (optional) debug serial port
nixnax	142:54d1543e23e5	1231	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	1232	pppInitStruct(); // initialize all the PPP properties
nixnax	143:c5019f856a56	1233	}

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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.