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@155:9c6a1d249e26, 2017-09-01 (annotated)

Committer:: nixnax
Date:: Fri Sep 01 23:04:41 2017 +0000
Revision:: 155:9c6a1d249e26
Parent:: 154:18b2bd92f557
Child:: 156:163c23249731

Working TCP flags in tcpHeaderType.

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	154:18b2bd92f557	48	#define SERIAL_PORT_MONITOR_NO /* change to SERIAL_PORT_MONITOR_YES for debug messages */
nixnax	142:54d1543e23e5	49
nixnax	142:54d1543e23e5	50	// here we define the OPTIONAL, second debug serial port for various mbed target boards
nixnax	142:54d1543e23e5	51	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	52	#if defined(TARGET_LPC1768)
nixnax	142:54d1543e23e5	53	Serial xx(p9, p10); // Second serial port on LPC1768 - not required to run, if you get compile error here, change #define SERIAL_PORT_MONITOR_YES to #define SERIAL_PORT_MONITOR_NO
nixnax	142:54d1543e23e5	54	#elif defined(TARGET_NUCLEO_F446RE) \|\| defined(TARGET_NUCLEO_L152RE) \|\| defined(TARGET_NUCLEO_L053R8) \|\| defined(TARGET_NUCLEO_L476RG) \|\| defined(TARGET_NUCLEO_F401RE)
nixnax	142:54d1543e23e5	55	Serial xx(PC_10, PC_11); // Second serial port on NUCLEO boards - not required to run, if you get compile error here, change #define SERIAL_PORT_MONITOR_YES to #define SERIAL_PORT_MONITOR_NO
nixnax	142:54d1543e23e5	56	#elif defined(TARGET_LPC11U24)
nixnax	142:54d1543e23e5	57	#error The LPC11U24 does not have a second serial port to use for debugging - change SERIAL_PORT_MONITOR_YES back to SERIAL_PORT_MONITOR_NO
nixnax	142:54d1543e23e5	58	#elif defined (TARGET_KL46Z) \|\| (TARGET_KL25Z)
nixnax	142:54d1543e23e5	59	Serial xx(PTE0,PTE1); // Second serial port on FRDM-KL46Z board
nixnax	142:54d1543e23e5	60	#elif defined(YOUR_TARGET_BOARD_NAME_HERE)
nixnax	142:54d1543e23e5	61	// change the next line to YOUR target board's second serial port pin definition if it's not present - and if it works, please send it to me - thanks!!!
nixnax	142:54d1543e23e5	62	Serial xx(p9, p10); // change this to YOUR board second serial port pin definition - and please send it to me if it works!!!
nixnax	142:54d1543e23e5	63	#else
nixnax	142:54d1543e23e5	64	#error Add your target board's second serial port here if you want to use debugging - or simply change SERIAL_PORT_MONITOR_YES to SERIAL_PORT_MONITOR_NO
nixnax	142:54d1543e23e5	65	#endif
nixnax	142:54d1543e23e5	66	#define debugPrintf(x...) xx.printf (x) /* if we have a serial port we print debug messages */
nixnax	142:54d1543e23e5	67	#define debugPutc(x...) xx.putc(x)
nixnax	142:54d1543e23e5	68	#define debugBaudRate(x...) xx.baud(x)
nixnax	142:54d1543e23e5	69	#else
nixnax	142:54d1543e23e5	70	// if we don't have a debug port the debug print functions do nothing
nixnax	142:54d1543e23e5	71	#define debugPrintf(x...) {}
nixnax	142:54d1543e23e5	72	#define debugPutc(x...) {}
nixnax	142:54d1543e23e5	73	#define debugBaudRate(x...) {}
nixnax	142:54d1543e23e5	74	#endif
nixnax	142:54d1543e23e5	75
nixnax	142:54d1543e23e5	76	// verbosity flags used in debug printouts - change to 1 to see increasingly more detailed debug info.
nixnax	142:54d1543e23e5	77	#define v0 1
nixnax	142:54d1543e23e5	78	#define v1 0
nixnax	142:54d1543e23e5	79	#define v2 0
nixnax	142:54d1543e23e5	80	#define IP_HEADER_DUMP_YES /* YES for ip header dump */
nixnax	142:54d1543e23e5	81	#define TCP_HEADER_DUMP_YES /* YES for tcp header dump */
nixnax	142:54d1543e23e5	82
nixnax	142:54d1543e23e5	83	// this is the webpage we serve when we get an HTTP request to root (/)
nixnax	142:54d1543e23e5	84	// keep size under ~900 bytes to fit into a single PPP packet
nixnax	142:54d1543e23e5	85
nixnax	142:54d1543e23e5	86	const static char rootWebPage[] = "\
nixnax	142:54d1543e23e5	87	<!DOCTYPE html>\
nixnax	142:54d1543e23e5	88	<html>\
nixnax	142:54d1543e23e5	89	<head>\
nixnax	146:a45f49a2b29c	90	<title>mbed PPP-Blinky</title>\r\n\
nixnax	146:a45f49a2b29c	91	<script>\r\n\
nixnax	142:54d1543e23e5	92	window.onload=function(){\
nixnax	142:54d1543e23e5	93	setInterval(function(){function x(){return document.getElementById('w');};\
nixnax	146:a45f49a2b29c	94	x().textContent=parseInt(x().textContent)+1;},100);};\r\n\
nixnax	146:a45f49a2b29c	95	</script>\r\n\
nixnax	142:54d1543e23e5	96	</head>\
nixnax	142:54d1543e23e5	97	<body style=\"font-family: sans-serif; font-size:20px; text-align:center; color:#807070\">\
nixnax	142:54d1543e23e5	98	<h1>mbed PPP-Blinky Up and Running</h1>\
nixnax	142:54d1543e23e5	99	<h1 id=\"w\">0</h1>\
nixnax	142:54d1543e23e5	100	<h1><a href=\"http://bit.ly/pppBlink2\">Source on mbed</a></h1>\
nixnax	142:54d1543e23e5	101	<h1><a href=\"/ws\">WebSocket Demo</a></h1>\
nixnax	142:54d1543e23e5	102	<h1><a href=\"/x\">Benchmark 1</a></h1>\
nixnax	142:54d1543e23e5	103	<h1><a href=\"/xb\">Benchmark 2</a></h1>\
nixnax	142:54d1543e23e5	104	<h1><a href=\"http://jsfiddle.net/d26cyuh2/\">JSFiddle Demo</a></h1>\
nixnax	142:54d1543e23e5	105	</body>\
nixnax	146:a45f49a2b29c	106	</html>\r\n"; // size = 644 bytes plus 1 null byte = 645 bytes
nixnax	142:54d1543e23e5	107
nixnax	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	152:025c73b6c0a9	158
nixnax	142:54d1543e23e5	159	/// a structure to keep all our ppp globals in
nixnax	142:54d1543e23e5	160	struct pppType {
nixnax	154:18b2bd92f557	161	pppHeaderType * ppp; // pointer to ppp struct
nixnax	154:18b2bd92f557	162	union {
nixnax	154:18b2bd92f557	163	ipHeaderType * ip; // pointer to ip header struct
nixnax	155:9c6a1d249e26	164	char * ipStart; // char pointer to ip header struct (need a char pointer for byte offset calculations)
nixnax	154:18b2bd92f557	165	};
nixnax	154:18b2bd92f557	166	union {
nixnax	154:18b2bd92f557	167	tcpHeaderType * tcp; // pointer to tcp header struct
nixnax	155:9c6a1d249e26	168	char * tcpStart; // char pointer to tcp header struct (need a char pointer for byte offset calculations)
nixnax	154:18b2bd92f557	169	};
nixnax	142:54d1543e23e5	170	int online; // we hunt for a PPP connection if this is zero
nixnax	143:c5019f856a56	171	int hostIP; // ip address of host
nixnax	145:098b6ed2f7f2	172	int fcs; // PPP "frame check sequence" - a 16-bit HDLC-like checksum used in all PPP frames
nixnax	142:54d1543e23e5	173	int ledState; // state of LED1
nixnax	146:a45f49a2b29c	174	int responseCounter;
nixnax	142:54d1543e23e5	175	int firstFrame; // cleared after first frame
nixnax	142:54d1543e23e5	176	struct {
nixnax	142:54d1543e23e5	177	#define RXBUFLEN (1<<11)
nixnax	142:54d1543e23e5	178	// the serial port receive buffer and packet buffer, size is RXBUFLEN (currently 2048 bytes)
nixnax	142:54d1543e23e5	179	char buf[RXBUFLEN]; // RXBUFLEN MUST be a power of two because we use & operator for fast wrap-around in ring buffer
nixnax	142:54d1543e23e5	180	int head;
nixnax	142:54d1543e23e5	181	int tail;
nixnax	142:54d1543e23e5	182	int rtail;
nixnax	142:54d1543e23e5	183	int buflevel;
nixnax	142:54d1543e23e5	184	} rx; // serial port objects
nixnax	142:54d1543e23e5	185	struct {
nixnax	142:54d1543e23e5	186	int len; // number of bytes in buffer
nixnax	142:54d1543e23e5	187	int crc; // PPP CRC (frame check)
nixnax	152:025c73b6c0a9	188	#define PPP_max_size 1600
nixnax	152:025c73b6c0a9	189	// we are assuming 100 bytes more than MTU size of 1500
nixnax	154:18b2bd92f557	190	char buf[PPP_max_size]; // send and receive buffer large enough for largest IP packet
nixnax	142:54d1543e23e5	191	} pkt; // ppp buffer objects
nixnax	142:54d1543e23e5	192	struct {
nixnax	142:54d1543e23e5	193	int frameStartIndex; // frame start marker
nixnax	142:54d1543e23e5	194	int frameEndIndex; // frame end marker
nixnax	142:54d1543e23e5	195	} hdlc; // hdlc frame objects
nixnax	142:54d1543e23e5	196	struct {
nixnax	142:54d1543e23e5	197	unsigned int ident; // our IP ident value (outgoing frame count)
nixnax	154:18b2bd92f557	198	} ipData; // ip related object
nixnax	142:54d1543e23e5	199	};
nixnax	142:54d1543e23e5	200
nixnax	142:54d1543e23e5	201	pppType ppp; // our global - definitely not thread safe
nixnax	142:54d1543e23e5	202
nixnax	142:54d1543e23e5	203	/// Initialize the ppp structure and clear the receive buffer
nixnax	142:54d1543e23e5	204	void pppInitStruct()
nixnax	142:54d1543e23e5	205	{
nixnax	142:54d1543e23e5	206	memset( ppp.rx.buf, 0, RXBUFLEN);
nixnax	142:54d1543e23e5	207	ppp.online=0;
nixnax	142:54d1543e23e5	208	ppp.rx.tail=0;
nixnax	142:54d1543e23e5	209	ppp.rx.rtail=0;
nixnax	142:54d1543e23e5	210	ppp.rx.head=0;
nixnax	142:54d1543e23e5	211	ppp.rx.buflevel=0;
nixnax	142:54d1543e23e5	212	ppp.pkt.len=0;
nixnax	154:18b2bd92f557	213	ppp.ipData.ident=10000; // easy to recognize in ip packet dumps
nixnax	142:54d1543e23e5	214	ppp.ledState=0;
nixnax	142:54d1543e23e5	215	ppp.hdlc.frameStartIndex=0;
nixnax	146:a45f49a2b29c	216	ppp.responseCounter=0;
nixnax	142:54d1543e23e5	217	ppp.firstFrame=1;
nixnax	154:18b2bd92f557	218	ppp.ppp = (pppHeaderType *)ppp.pkt.buf;
nixnax	154:18b2bd92f557	219	ppp.ip = (ipHeaderType *)(ppp.pkt.buf+4); // ppp header is 4 bytes long
nixnax	142:54d1543e23e5	220	}
nixnax	142:54d1543e23e5	221
nixnax	142:54d1543e23e5	222	/// Toggle the LED on every second PPP packet received
nixnax	142:54d1543e23e5	223	void led1Toggle()
nixnax	142:54d1543e23e5	224	{
nixnax	142:54d1543e23e5	225	led1 = (ppp.ledState >> 1) & 1; // use second bit, in other words toggle LED only every second packet
nixnax	143:c5019f856a56	226	ppp.ledState++;
nixnax	142:54d1543e23e5	227	}
nixnax	142:54d1543e23e5	228
nixnax	152:025c73b6c0a9	229	/// returns 1 after a connect message, 0 at startup or after a disconnect message
nixnax	150:3366bf3d294e	230	int connectedPpp()
nixnax	142:54d1543e23e5	231	{
nixnax	142:54d1543e23e5	232	return ppp.online;
nixnax	143:c5019f856a56	233	}
nixnax	142:54d1543e23e5	234
nixnax	143:c5019f856a56	235	/// Check for available characters from the PC and read them into our own circular serial receive buffer at ppp.rx.buf.
nixnax	143:c5019f856a56	236	/// Also, if we are offline and a 0x7e frame start character is seen, we go online immediately
nixnax	142:54d1543e23e5	237	void checkPc()
nixnax	142:54d1543e23e5	238	{
nixnax	142:54d1543e23e5	239	char ch;
nixnax	142:54d1543e23e5	240	if ( pc.readable() ) {
nixnax	142:54d1543e23e5	241	int hd = (ppp.rx.head+1)&(RXBUFLEN-1); // increment/wrap head index
nixnax	142:54d1543e23e5	242	if ( hd == ppp.rx.rtail ) {
nixnax	142:54d1543e23e5	243	debugPrintf("\nReceive buffer full\n");
nixnax	142:54d1543e23e5	244	return;
nixnax	142:54d1543e23e5	245	}
nixnax	142:54d1543e23e5	246	ch = pc.getc(); // read new character
nixnax	142:54d1543e23e5	247	ppp.rx.buf[ppp.rx.head] = ch; // insert in our receive buffer
nixnax	142:54d1543e23e5	248	if ( ppp.online == 0 ) {
nixnax	142:54d1543e23e5	249	if (ch == 0x7E) {
nixnax	142:54d1543e23e5	250	ppp.online = 1;
nixnax	142:54d1543e23e5	251	}
nixnax	142:54d1543e23e5	252	}
nixnax	142:54d1543e23e5	253	ppp.rx.head = hd; // update head pointer
nixnax	142:54d1543e23e5	254	ppp.rx.buflevel++;
nixnax	142:54d1543e23e5	255	}
nixnax	142:54d1543e23e5	256	}
nixnax	142:54d1543e23e5	257
nixnax	142:54d1543e23e5	258	/// print to debug port while checking for incoming characters
nixnax	142:54d1543e23e5	259	void putcWhileCheckingInput( char outByte )
nixnax	142:54d1543e23e5	260	{
nixnax	142:54d1543e23e5	261	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	262	checkPc();
nixnax	142:54d1543e23e5	263	debugPutc( outByte );
nixnax	142:54d1543e23e5	264	checkPc();
nixnax	142:54d1543e23e5	265	#endif
nixnax	142:54d1543e23e5	266	}
nixnax	142:54d1543e23e5	267
nixnax	142:54d1543e23e5	268	/// puts to debug port while checking the PPP input stream
nixnax	142:54d1543e23e5	269	void putsWhileCheckingInput( char * data )
nixnax	142:54d1543e23e5	270	{
nixnax	142:54d1543e23e5	271	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	272	char * nextChar = data;
nixnax	142:54d1543e23e5	273	while( *nextChar != 0 ) {
nixnax	142:54d1543e23e5	274	putcWhileCheckingInput( *nextChar ); // write one character to debug port while checking input
nixnax	142:54d1543e23e5	275	nextChar++;
nixnax	142:54d1543e23e5	276	}
nixnax	142:54d1543e23e5	277	#endif
nixnax	142:54d1543e23e5	278	}
nixnax	142:54d1543e23e5	279
nixnax	145:098b6ed2f7f2	280	/// Initialize the PPP FCS (frame check sequence) total
nixnax	145:098b6ed2f7f2	281	void fcsReset()
nixnax	142:54d1543e23e5	282	{
nixnax	145:098b6ed2f7f2	283	ppp.fcs=0xffff; // crc restart
nixnax	142:54d1543e23e5	284	}
nixnax	142:54d1543e23e5	285
nixnax	145:098b6ed2f7f2	286	/// update the cumulative PPP FCS (frame check sequence)
nixnax	145:098b6ed2f7f2	287	void fcsDo(int x)
nixnax	142:54d1543e23e5	288	{
nixnax	142:54d1543e23e5	289	for (int i=0; i<8; i++) {
nixnax	145:098b6ed2f7f2	290	ppp.fcs=((ppp.fcs&1)^(x&1))?(ppp.fcs>>1)^0x8408:ppp.fcs>>1; // crc calculator
nixnax	142:54d1543e23e5	291	x>>=1;
nixnax	142:54d1543e23e5	292	}
nixnax	142:54d1543e23e5	293	checkPc(); // handle input
nixnax	142:54d1543e23e5	294	}
nixnax	142:54d1543e23e5	295
nixnax	145:098b6ed2f7f2	296	/// calculate the PPP FCS (frame check sequence) on an entire block of memory
nixnax	145:098b6ed2f7f2	297	int fcsBuf(char * buf, int size) // crc on an entire block of memory
nixnax	142:54d1543e23e5	298	{
nixnax	145:098b6ed2f7f2	299	fcsReset();
nixnax	145:098b6ed2f7f2	300	for(int i=0; i<size; i++)fcsDo(*buf++);
nixnax	145:098b6ed2f7f2	301	return ppp.fcs;
nixnax	142:54d1543e23e5	302	}
nixnax	142:54d1543e23e5	303
nixnax	142:54d1543e23e5	304	/// Get one character from our received PPP buffer
nixnax	142:54d1543e23e5	305	int pc_getBuf()
nixnax	142:54d1543e23e5	306	{
nixnax	142:54d1543e23e5	307	int x = ppp.rx.buf[ ppp.rx.tail ];
nixnax	142:54d1543e23e5	308	ppp.rx.tail=(ppp.rx.tail+1)&(RXBUFLEN-1);
nixnax	142:54d1543e23e5	309	ppp.rx.buflevel--;
nixnax	142:54d1543e23e5	310	return x;
nixnax	142:54d1543e23e5	311	}
nixnax	142:54d1543e23e5	312
nixnax	142:54d1543e23e5	313	/// Dump a PPP frame to the debug serial port
nixnax	142:54d1543e23e5	314	/// Note - the hex output of dumpPPPFrame() can be imported into WireShark
nixnax	142:54d1543e23e5	315	/// Capture the frame's hex output in your terminal program and save as a text file
nixnax	142:54d1543e23e5	316	/// In WireShark, use "Import Hex File". Options are: Offset=None, Protocol=PPP.
nixnax	142:54d1543e23e5	317	void dumpPPPFrame()
nixnax	142:54d1543e23e5	318	{
nixnax	142:54d1543e23e5	319	char pbuf[30];
nixnax	142:54d1543e23e5	320	for(int i=0; i<ppp.pkt.len; i++) {
nixnax	142:54d1543e23e5	321	checkPc();
nixnax	142:54d1543e23e5	322	sprintf(pbuf, "%02x ", ppp.pkt.buf[i]);
nixnax	142:54d1543e23e5	323	checkPc();
nixnax	142:54d1543e23e5	324	putsWhileCheckingInput(pbuf);
nixnax	142:54d1543e23e5	325	}
nixnax	142:54d1543e23e5	326	checkPc();
nixnax	142:54d1543e23e5	327	sprintf(pbuf, " CRC=%04x Len=%d\n", ppp.pkt.crc, ppp.pkt.len);
nixnax	142:54d1543e23e5	328	checkPc();
nixnax	142:54d1543e23e5	329	putsWhileCheckingInput(pbuf);
nixnax	142:54d1543e23e5	330	}
nixnax	142:54d1543e23e5	331
nixnax	142:54d1543e23e5	332	/// Process a received PPP frame
nixnax	142:54d1543e23e5	333	void processPPPFrame(int start, int end)
nixnax	142:54d1543e23e5	334	{
nixnax	142:54d1543e23e5	335	led1Toggle(); // change led1 state on every frame we receive
nixnax	142:54d1543e23e5	336	if(start==end) {
nixnax	142:54d1543e23e5	337	return; // empty frame
nixnax	142:54d1543e23e5	338	}
nixnax	145:098b6ed2f7f2	339	fcsReset();
nixnax	142:54d1543e23e5	340	char * dest = ppp.pkt.buf;
nixnax	142:54d1543e23e5	341	ppp.pkt.len=0;
nixnax	142:54d1543e23e5	342	int unstuff=0;
nixnax	142:54d1543e23e5	343	int idx = start;
nixnax	142:54d1543e23e5	344	while(1) {
nixnax	142:54d1543e23e5	345	checkPc();
nixnax	142:54d1543e23e5	346	if (unstuff==0) {
nixnax	142:54d1543e23e5	347	if (ppp.rx.buf[idx]==0x7d) unstuff=1;
nixnax	142:54d1543e23e5	348	else {
nixnax	142:54d1543e23e5	349	*dest = ppp.rx.buf[idx];
nixnax	142:54d1543e23e5	350	ppp.pkt.len++;
nixnax	142:54d1543e23e5	351	dest++;
nixnax	145:098b6ed2f7f2	352	fcsDo(ppp.rx.buf[idx]);
nixnax	142:54d1543e23e5	353	}
nixnax	142:54d1543e23e5	354	} else { // unstuff characters prefixed with 0x7d
nixnax	142:54d1543e23e5	355	*dest = ppp.rx.buf[idx]^0x20;
nixnax	142:54d1543e23e5	356	ppp.pkt.len++;
nixnax	142:54d1543e23e5	357	dest++;
nixnax	145:098b6ed2f7f2	358	fcsDo(ppp.rx.buf[idx]^0x20);
nixnax	142:54d1543e23e5	359	unstuff=0;
nixnax	142:54d1543e23e5	360	}
nixnax	142:54d1543e23e5	361	idx = (idx+1) & (RXBUFLEN-1);
nixnax	142:54d1543e23e5	362	if (idx == end) break;
nixnax	142:54d1543e23e5	363	}
nixnax	145:098b6ed2f7f2	364	ppp.pkt.crc = ppp.fcs & 0xffff;
nixnax	142:54d1543e23e5	365	if(0) dumpPPPFrame(); // set to 1 to dump ALL ppp frames
nixnax	142:54d1543e23e5	366	if (ppp.pkt.crc == 0xf0b8) { // check for good CRC
nixnax	142:54d1543e23e5	367	determinePacketType();
nixnax	142:54d1543e23e5	368	} else {
nixnax	142:54d1543e23e5	369	#define REPORT_FCS_ERROR_YES
nixnax	142:54d1543e23e5	370	#ifdef REPORT_FCS_ERROR_YES
nixnax	142:54d1543e23e5	371	char pbuf[50]; // local print buffer
nixnax	142:54d1543e23e5	372	checkPc();
nixnax	142:54d1543e23e5	373	sprintf(pbuf, "\nPPP FCS(crc) Error CRC=%x Length = %d\n",ppp.pkt.crc,ppp.pkt.len); // print a debug line
nixnax	142:54d1543e23e5	374	checkPc();
nixnax	142:54d1543e23e5	375	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	376	if(0) dumpPPPFrame(); // set to 1 to dump frames with errors in them
nixnax	142:54d1543e23e5	377	#endif
nixnax	142:54d1543e23e5	378	}
nixnax	142:54d1543e23e5	379	}
nixnax	142:54d1543e23e5	380
nixnax	142:54d1543e23e5	381	/// output a character to the PPP port while checking for incoming characters
nixnax	142:54d1543e23e5	382	void pcPutcWhileCheckingInput(int ch)
nixnax	142:54d1543e23e5	383	{
nixnax	142:54d1543e23e5	384	checkPc(); // check input
nixnax	142:54d1543e23e5	385	pc.putc(ch);
nixnax	142:54d1543e23e5	386	checkPc();
nixnax	142:54d1543e23e5	387	}
nixnax	142:54d1543e23e5	388
nixnax	142:54d1543e23e5	389	/// do PPP HDLC-like handling of special (flag) characters
nixnax	143:c5019f856a56	390	void hdlcPut(int ch)
nixnax	142:54d1543e23e5	391	{
nixnax	142:54d1543e23e5	392	if ( (ch<0x20) \|\| (ch==0x7d) \|\| (ch==0x7e) ) {
nixnax	142:54d1543e23e5	393	pcPutcWhileCheckingInput(0x7d);
nixnax	142:54d1543e23e5	394	pcPutcWhileCheckingInput(ch^0x20); // these characters need special handling
nixnax	142:54d1543e23e5	395	} else {
nixnax	142:54d1543e23e5	396	pcPutcWhileCheckingInput(ch);
nixnax	142:54d1543e23e5	397	}
nixnax	142:54d1543e23e5	398	}
nixnax	142:54d1543e23e5	399
nixnax	142:54d1543e23e5	400	/// send a PPP frame in HDLC format
nixnax	144:01d98cf7738e	401	void sendPppFrame()
nixnax	143:c5019f856a56	402	{
nixnax	145:098b6ed2f7f2	403	int crc = fcsBuf(ppp.pkt.buf, ppp.pkt.len-2); // update crc
nixnax	142:54d1543e23e5	404	ppp.pkt.buf[ ppp.pkt.len-2 ] = (~crc>>0); // fcs lo (crc)
nixnax	142:54d1543e23e5	405	ppp.pkt.buf[ ppp.pkt.len-1 ] = (~crc>>8); // fcs hi (crc)
nixnax	142:54d1543e23e5	406	pcPutcWhileCheckingInput(0x7e); // hdlc start-of-frame "flag"
nixnax	142:54d1543e23e5	407	for(int i=0; i<ppp.pkt.len; i++) {
nixnax	142:54d1543e23e5	408	wait_us(86); // wait one character time
nixnax	142:54d1543e23e5	409	checkPc();
nixnax	142:54d1543e23e5	410	hdlcPut( ppp.pkt.buf[i] ); // send a character
nixnax	142:54d1543e23e5	411	}
nixnax	142:54d1543e23e5	412	pcPutcWhileCheckingInput(0x7e); // hdlc end-of-frame "flag"
nixnax	142:54d1543e23e5	413	}
nixnax	142:54d1543e23e5	414
nixnax	143:c5019f856a56	415	/// 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	416	int bufferToIP(char * buffer)
nixnax	143:c5019f856a56	417	{
nixnax	143:c5019f856a56	418	int result=0;
nixnax	143:c5019f856a56	419	for(int i=0; i<4; i++) result = (result<<8)\|(*buffer++ & 0xff);
nixnax	143:c5019f856a56	420	return result;
nixnax	143:c5019f856a56	421	}
nixnax	143:c5019f856a56	422
nixnax	142:54d1543e23e5	423	/// handle IPCP configuration requests
nixnax	142:54d1543e23e5	424	void ipcpConfigRequestHandler()
nixnax	142:54d1543e23e5	425	{
nixnax	142:54d1543e23e5	426	debugPrintf("Their IPCP Config Req, Our Ack\n");
nixnax	143:c5019f856a56	427	if(ppp.pkt.buf[8]==3) {
nixnax	143:c5019f856a56	428	ppp.hostIP = bufferToIP(ppp.pkt.buf+10);
nixnax	143:c5019f856a56	429	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	430	}
nixnax	143:c5019f856a56	431
nixnax	142:54d1543e23e5	432	ppp.pkt.buf[4]=2; // change code to ack
nixnax	144:01d98cf7738e	433	sendPppFrame(); // acknowledge everything they ask for - assume it's IP addresses
nixnax	142:54d1543e23e5	434
nixnax	142:54d1543e23e5	435	debugPrintf("Our IPCP Ask (no options)\n");
nixnax	142:54d1543e23e5	436	ppp.pkt.buf[4]=1; // change code to request
nixnax	142:54d1543e23e5	437	ppp.pkt.buf[7]=4; // no options in this request
nixnax	142:54d1543e23e5	438	ppp.pkt.len=10; // no options in this request shortest ipcp packet possible (4 ppp + 4 ipcp + 2 crc)
nixnax	144:01d98cf7738e	439	sendPppFrame(); // send our request
nixnax	142:54d1543e23e5	440	}
nixnax	142:54d1543e23e5	441
nixnax	142:54d1543e23e5	442	/// handle IPCP acknowledge (do nothing)
nixnax	142:54d1543e23e5	443	void ipcpAckHandler()
nixnax	142:54d1543e23e5	444	{
nixnax	142:54d1543e23e5	445	debugPrintf("Their IPCP Grant\n");
nixnax	142:54d1543e23e5	446	}
nixnax	142:54d1543e23e5	447
nixnax	143:c5019f856a56	448	/// Handle IPCP NACK by sending our suggested IP address if there is an IP involved.
nixnax	143:c5019f856a56	449	/// 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	450	void ipcpNackHandler()
nixnax	142:54d1543e23e5	451	{
nixnax	146:a45f49a2b29c	452	debugPrintf("Their IPCP Nack\n");
nixnax	142:54d1543e23e5	453	if (ppp.pkt.buf[8]==3) { // check if the NACK contains an IP address parameter
nixnax	142:54d1543e23e5	454	ppp.pkt.buf[4]=1; // assume the NACK contains our "suggested" IP address
nixnax	144:01d98cf7738e	455	sendPppFrame(); // let's request this IP address as ours
nixnax	143:c5019f856a56	456	debugPrintf("Our IPCP ACK (received an IP)\n");
nixnax	146:a45f49a2b29c	457	} else { // if it's not an IP nack we ignore it
nixnax	146:a45f49a2b29c	458	debugPrintf("IPCP Nack Ignored\n");
nixnax	146:a45f49a2b29c	459	}
nixnax	142:54d1543e23e5	460	}
nixnax	142:54d1543e23e5	461
nixnax	142:54d1543e23e5	462	/// handle all other IPCP requests (by ignoring them)
nixnax	142:54d1543e23e5	463	void ipcpDefaultHandler()
nixnax	142:54d1543e23e5	464	{
nixnax	142:54d1543e23e5	465	debugPrintf("Their IPCP Other\n");
nixnax	142:54d1543e23e5	466	}
nixnax	142:54d1543e23e5	467
nixnax	142:54d1543e23e5	468	/// process an incoming IPCP packet
nixnax	142:54d1543e23e5	469	void IPCPframe()
nixnax	142:54d1543e23e5	470	{
nixnax	142:54d1543e23e5	471	int code = ppp.pkt.buf[4]; // packet type is here
nixnax	142:54d1543e23e5	472	switch (code) {
nixnax	142:54d1543e23e5	473	case 1:
nixnax	142:54d1543e23e5	474	ipcpConfigRequestHandler();
nixnax	142:54d1543e23e5	475	break;
nixnax	142:54d1543e23e5	476	case 2:
nixnax	142:54d1543e23e5	477	ipcpAckHandler();
nixnax	142:54d1543e23e5	478	break;
nixnax	142:54d1543e23e5	479	case 3:
nixnax	142:54d1543e23e5	480	ipcpNackHandler();
nixnax	142:54d1543e23e5	481	break;
nixnax	142:54d1543e23e5	482	default:
nixnax	142:54d1543e23e5	483	ipcpDefaultHandler();
nixnax	142:54d1543e23e5	484	}
nixnax	142:54d1543e23e5	485	}
nixnax	142:54d1543e23e5	486
nixnax	142:54d1543e23e5	487	/// perform a 16-bit checksum. if the byte count is odd, stuff in an extra zero byte.
nixnax	142:54d1543e23e5	488	unsigned int dataCheckSum(unsigned char * ptr, int len)
nixnax	142:54d1543e23e5	489	{
nixnax	142:54d1543e23e5	490	unsigned int i,hi,lo,sum;
nixnax	142:54d1543e23e5	491	unsigned char placeHolder;
nixnax	142:54d1543e23e5	492	if (len&1) {
nixnax	142:54d1543e23e5	493	placeHolder = ptr[len];
nixnax	142:54d1543e23e5	494	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	495	}
nixnax	142:54d1543e23e5	496	sum=0;
nixnax	142:54d1543e23e5	497	i=0;
nixnax	142:54d1543e23e5	498	while ( i<len ) {
nixnax	142:54d1543e23e5	499	checkPc();
nixnax	142:54d1543e23e5	500	hi = ptr[i++];
nixnax	142:54d1543e23e5	501	lo = ptr[i++];
nixnax	142:54d1543e23e5	502	sum = sum + ( (hi<<8) \| lo );
nixnax	142:54d1543e23e5	503	}
nixnax	142:54d1543e23e5	504	if (len&1) {
nixnax	142:54d1543e23e5	505	ptr[len] = placeHolder; // restore the extra byte we made zero
nixnax	142:54d1543e23e5	506	}
nixnax	142:54d1543e23e5	507	sum = (sum & 0xffff) + (sum>>16);
nixnax	142:54d1543e23e5	508	sum = (sum & 0xffff) + (sum>>16); // sum one more time to catch any carry from the carry
nixnax	142:54d1543e23e5	509	return ~sum;
nixnax	142:54d1543e23e5	510	}
nixnax	142:54d1543e23e5	511
nixnax	142:54d1543e23e5	512	/// perform the checksum on an IP header
nixnax	146:a45f49a2b29c	513	void IpHeaderCheckSum()
nixnax	142:54d1543e23e5	514	{
nixnax	146:a45f49a2b29c	515	ppp.pkt.buf[4+10]=0; // zero the checsum in the IP header
nixnax	146:a45f49a2b29c	516	ppp.pkt.buf[4+11]=0; // zero the checksum in the IP header
nixnax	146:a45f49a2b29c	517	int len =(ppp.pkt.buf[4]&0xf)*4; // length of IP header in bytes
nixnax	146:a45f49a2b29c	518	char * ptr = ppp.pkt.buf+4; // start of IP packet
nixnax	142:54d1543e23e5	519	int sum=0;
nixnax	142:54d1543e23e5	520	for (int i=0; i<len/2; i++) {
nixnax	142:54d1543e23e5	521	int hi = *ptr;
nixnax	142:54d1543e23e5	522	ptr++;
nixnax	142:54d1543e23e5	523	int lo = *ptr;
nixnax	142:54d1543e23e5	524	ptr++;
nixnax	142:54d1543e23e5	525	int val = ( lo & 0xff ) \| ( (hi<<8) & 0xff00 );
nixnax	142:54d1543e23e5	526	sum = sum + val;
nixnax	142:54d1543e23e5	527	checkPc();
nixnax	142:54d1543e23e5	528	}
nixnax	142:54d1543e23e5	529	sum = sum + (sum>>16);
nixnax	142:54d1543e23e5	530	sum = ~sum;
nixnax	146:a45f49a2b29c	531	ppp.pkt.buf[4+10]= (sum>>8);
nixnax	146:a45f49a2b29c	532	ppp.pkt.buf[4+11]= (sum );
nixnax	146:a45f49a2b29c	533	}
nixnax	146:a45f49a2b29c	534
nixnax	147:0f40005cbc5f	535	/// swap the IP source and destination addresses
nixnax	147:0f40005cbc5f	536	void swapIpAddresses()
nixnax	147:0f40005cbc5f	537	{
nixnax	147:0f40005cbc5f	538	char tempHold[4];
nixnax	147:0f40005cbc5f	539	memcpy(tempHold, ppp.pkt.buf+16,4); // tempHold <- source IP
nixnax	147:0f40005cbc5f	540	memcpy(ppp.pkt.buf+16, ppp.pkt.buf+20,4); // source <- dest
nixnax	147:0f40005cbc5f	541	memcpy(ppp.pkt.buf+20, tempHold,4); // dest <- tempHold
nixnax	147:0f40005cbc5f	542	}
nixnax	147:0f40005cbc5f	543
nixnax	149:969d98f6fb88	544	/// swap the IP source and destination ports
nixnax	149:969d98f6fb88	545	void swapIpPorts()
nixnax	149:969d98f6fb88	546	{
nixnax	149:969d98f6fb88	547	int headerSizeIP = 4*(ppp.pkt.buf[4]&0xf); // calculate size of IP header
nixnax	149:969d98f6fb88	548	char * ipSrcPort = 4 + ppp.pkt.buf + headerSizeIP + 0; // ip source port location
nixnax	149:969d98f6fb88	549	char * ipDstPort = 4 + ppp.pkt.buf + headerSizeIP + 2; // ip destin port location
nixnax	149:969d98f6fb88	550	char tempHold[2];
nixnax	149:969d98f6fb88	551	memcpy(tempHold, ipSrcPort,2); // tempHold <- source
nixnax	149:969d98f6fb88	552	memcpy(ipSrcPort,ipDstPort,2); // source <- dest
nixnax	149:969d98f6fb88	553	memcpy(ipDstPort,tempHold, 2); // dest <- tempHold
nixnax	149:969d98f6fb88	554	}
nixnax	149:969d98f6fb88	555
nixnax	146:a45f49a2b29c	556	/// Process an incoming UDP packet.
nixnax	146:a45f49a2b29c	557	/// If the packet starts with the string "echo " or "test" we echo back a special packet
nixnax	146:a45f49a2b29c	558	void UDPpacket()
nixnax	146:a45f49a2b29c	559	{
nixnax	146:a45f49a2b29c	560	char * ipHeader = ppp.pkt.buf+4; // udp packet start
nixnax	146:a45f49a2b29c	561	char * ipSizeBuf = ipHeader+2; // size of IP packet
nixnax	146:a45f49a2b29c	562	int headerSizeIP = 4*(ipHeader[0]&0xf); // size of IP header
nixnax	146:a45f49a2b29c	563	char * udpHeader = ipHeader + headerSizeIP; // udp info start
nixnax	146:a45f49a2b29c	564	char * udpLen = udpHeader+4; // udp data length
nixnax	146:a45f49a2b29c	565	char * udpCheckSum = udpHeader+6; // udp checksum
nixnax	146:a45f49a2b29c	566	char * udpData = udpHeader+8; // start of UDP data
nixnax	146:a45f49a2b29c	567	int udpLength = ((udpLen[0]<<8) \| udpLen[1]); // size of udp packet
nixnax	146:a45f49a2b29c	568	int udpDataSize = udpLength - 8; // size of udp data
nixnax	147:0f40005cbc5f	569
nixnax	146:a45f49a2b29c	570	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	147:0f40005cbc5f	571	char * srcIP = ipHeader+12; // IP source
nixnax	147:0f40005cbc5f	572	char * dstIP = ipHeader+16; // IP destination
nixnax	149:969d98f6fb88	573	char * udpSrcPort = udpHeader+0; // source port
nixnax	149:969d98f6fb88	574	char * udpDstPort = udpHeader+2; // destination port
nixnax	146:a45f49a2b29c	575	int udpSrc = (udpSrcPort[0]<<8)\|udpSrcPort[1]; // integer of UDP source port
nixnax	146:a45f49a2b29c	576	int udpDst = (udpDstPort[0]<<8)\|udpDstPort[1]; // integer of UDP dest port
nixnax	146:a45f49a2b29c	577	if(v0) debugPrintf("UDP %d.%d.%d.%d:%d ", srcIP[0],srcIP[1],srcIP[2],srcIP[3],udpSrc);
nixnax	146:a45f49a2b29c	578	if(v0) debugPrintf("%d.%d.%d.%d:%d ", dstIP[0],dstIP[1],dstIP[2],dstIP[3],udpDst);
nixnax	146:a45f49a2b29c	579	if(v0) debugPrintf("Len %03d", udpLength);
nixnax	146:a45f49a2b29c	580	if (v1) {
nixnax	146:a45f49a2b29c	581	int printSize = udpLength-8;
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	146:a45f49a2b29c	584	char ch = udpData[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	146:a45f49a2b29c	594	int echoFound = !strncmp(udpData,"echo ",5); // true if UDP message starts with "echo "
nixnax	146:a45f49a2b29c	595	int testFound = !strncmp(udpData,"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	146:a45f49a2b29c	600	memcpy(udpData,"Got{",4); // in the UDP data modify "echo" to "Got:"
nixnax	146:a45f49a2b29c	601	char endString[] = "} UDP Server: PPP-Blinky\n"; // an appendix
nixnax	146:a45f49a2b29c	602	memcpy(udpData+udpLength-8,endString,sizeof(endString)-1); // add endstring size to the UDP message
nixnax	146:a45f49a2b29c	603	udpDataSize = udpDataSize + 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	146:a45f49a2b29c	609	memcpy(udpData,udpResponse,n); // copy response to the UDP data area
nixnax	146:a45f49a2b29c	610	udpDataSize = n; // new udp data size
nixnax	146:a45f49a2b29c	611	}
nixnax	146:a45f49a2b29c	612	udpLength = udpDataSize+8; // update udp packet length
nixnax	146:a45f49a2b29c	613	int ipSize = headerSizeIP + udpLength; // update ip packet length
nixnax	146:a45f49a2b29c	614	ppp.pkt.len = ipSize+2+4; // update ppp packet length
nixnax	146:a45f49a2b29c	615	udpLen[0] = udpLength>>8;
nixnax	146:a45f49a2b29c	616	udpLen[1] = udpLength; // update UDP length
nixnax	146:a45f49a2b29c	617	ipSizeBuf[0] = ipSize>>8;
nixnax	146:a45f49a2b29c	618	ipSizeBuf[1] = ipSize; // update IP length
nixnax	146:a45f49a2b29c	619	IpHeaderCheckSum(); // update IP header checksum
nixnax	146:a45f49a2b29c	620	memset(udpCheckSum,0,2); // we don't yet recompute the checksum (it's optional), so have to zero it
nixnax	146:a45f49a2b29c	621	sendPppFrame(); // send the UDP message back
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	142:54d1543e23e5	628	char * ipPkt = ppp.pkt.buf+4; // ip packet start
nixnax	142:54d1543e23e5	629	char * pktLen = ipPkt+2;
nixnax	142:54d1543e23e5	630	int packetLength = (pktLen[0]<<8) \| pktLen[1]; // icmp packet length
nixnax	142:54d1543e23e5	631	int headerSizeIP = (( ipPkt[0]&0xf)*4);
nixnax	142:54d1543e23e5	632	char * icmpType = ipPkt + headerSizeIP; // icmp data start
nixnax	142:54d1543e23e5	633	char * icmpSum = icmpType+2; // icmp checksum
nixnax	142:54d1543e23e5	634	#define ICMP_TYPE_PING_REQUEST 8
nixnax	142:54d1543e23e5	635	if ( icmpType[0] == ICMP_TYPE_PING_REQUEST ) {
nixnax	142:54d1543e23e5	636	char * ipTTL = ipPkt+8; // time to live
nixnax	147:0f40005cbc5f	637	ipTTL[0]--; // decrement time to live (so we have to update header checksum)
nixnax	147:0f40005cbc5f	638	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	639	char * srcAdr = ipPkt+12;
nixnax	142:54d1543e23e5	640	char * dstAdr = ipPkt+16;
nixnax	142:54d1543e23e5	641	int icmpIdent = (icmpType[4]<<8)\|icmpType[5];
nixnax	142:54d1543e23e5	642	int icmpSequence = (icmpType[6]<<8)\|icmpType[7];
nixnax	142:54d1543e23e5	643	if(1) {
nixnax	142:54d1543e23e5	644	char pbuf[50];
nixnax	142:54d1543e23e5	645	checkPc();
nixnax	142:54d1543e23e5	646	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	647	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	648	checkPc();
nixnax	142:54d1543e23e5	649	sprintf(pbuf, "Ident %04x Sequence %04d \n",icmpIdent,icmpSequence);
nixnax	142:54d1543e23e5	650	checkPc();
nixnax	142:54d1543e23e5	651	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	652	}
nixnax	142:54d1543e23e5	653	#endif
nixnax	147:0f40005cbc5f	654	swapIpAddresses(); // swap the IP source and destination addresses
nixnax	147:0f40005cbc5f	655	IpHeaderCheckSum(); // new ip header checksum (required because we changed TTL)
nixnax	142:54d1543e23e5	656	#define ICMP_TYPE_ECHO_REPLY 0
nixnax	142:54d1543e23e5	657	icmpType[0]=ICMP_TYPE_ECHO_REPLY; // icmp echo reply
nixnax	142:54d1543e23e5	658	icmpSum[0]=0;
nixnax	142:54d1543e23e5	659	icmpSum[1]=0; // zero the checksum for recalculation
nixnax	142:54d1543e23e5	660	int icmpLength = packetLength - headerSizeIP; // length of ICMP data portion
nixnax	142:54d1543e23e5	661	unsigned int sum = dataCheckSum( (unsigned char *)icmpType, icmpLength); // this checksum on icmp data portion
nixnax	142:54d1543e23e5	662	icmpSum[0]=(sum>>8)&0xff;
nixnax	142:54d1543e23e5	663	icmpSum[1]=(sum )&0xff; // new checksum for ICMP data portion
nixnax	142:54d1543e23e5	664
nixnax	142:54d1543e23e5	665	int printSize = icmpLength-8; // exclude size of icmp header
nixnax	142:54d1543e23e5	666	char * icmpData = icmpType+8; // the actual payload data is after the header
nixnax	142:54d1543e23e5	667	if (printSize > 10) printSize = 10; // print up to 20 characters
nixnax	142:54d1543e23e5	668	if (0) {
nixnax	142:54d1543e23e5	669	for (int i=0; i<printSize; i++) {
nixnax	142:54d1543e23e5	670	char ch = icmpData[i];
nixnax	142:54d1543e23e5	671	if (ch>31 && ch<127) {
nixnax	142:54d1543e23e5	672	putcWhileCheckingInput(ch);
nixnax	142:54d1543e23e5	673	} else {
nixnax	142:54d1543e23e5	674	putcWhileCheckingInput('_');
nixnax	142:54d1543e23e5	675	}
nixnax	142:54d1543e23e5	676	}
nixnax	142:54d1543e23e5	677	putcWhileCheckingInput('\n');
nixnax	142:54d1543e23e5	678	}
nixnax	144:01d98cf7738e	679	sendPppFrame(); // reply to the ping
nixnax	142:54d1543e23e5	680	} else {
nixnax	142:54d1543e23e5	681	if (v0) {
nixnax	142:54d1543e23e5	682	debugPrintf("ICMP type=%d \n", icmpType[0]);
nixnax	142:54d1543e23e5	683	}
nixnax	142:54d1543e23e5	684	}
nixnax	142:54d1543e23e5	685	}
nixnax	142:54d1543e23e5	686
nixnax	142:54d1543e23e5	687	/// handle an IGMP (internet group managment protocol) packet (by ignoring it)
nixnax	142:54d1543e23e5	688	void IGMPpacket()
nixnax	142:54d1543e23e5	689	{
nixnax	142:54d1543e23e5	690	if (v0) debugPrintf("IGMP type=%d \n", ppp.pkt.buf[28]);
nixnax	142:54d1543e23e5	691	}
nixnax	142:54d1543e23e5	692
nixnax	142:54d1543e23e5	693	/// dump the header of an IP pakcet on the (optional) debug serial port
nixnax	142:54d1543e23e5	694	void dumpHeaderIP (int outGoing)
nixnax	142:54d1543e23e5	695	{
nixnax	142:54d1543e23e5	696	#if defined(IP_HEADER_DUMP_YES) && defined(SERIAL_PORT_MONITOR_YES)
nixnax	142:54d1543e23e5	697	checkPc(); // we are expecting the first character of the next packet
nixnax	155:9c6a1d249e26	698	int IPv4Id = __REV16(ppp.ip->identR);
nixnax	152:025c73b6c0a9	699	char pbuf[80]; // local print buffer
nixnax	142:54d1543e23e5	700	int n=0;
nixnax	142:54d1543e23e5	701	n=n+sprintf(pbuf+n, outGoing ? "\x1b[34m" : "\x1b[30m" ); // VT100 color code, print black for incoming, blue for outgoing headers
nixnax	142:54d1543e23e5	702	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	703	#define DUMP_FULL_IP_ADDRESS_YES
nixnax	142:54d1543e23e5	704	#ifdef DUMP_FULL_IP_ADDRESS_YES
nixnax	154:18b2bd92f557	705	char * srcAdr = (char *)&ppp.ip->srcAdrR; // 4 bytes
nixnax	154:18b2bd92f557	706	char * dstAdr = (char *)&ppp.ip->dstAdrR; // 4 bytes = total of 20 bytes
nixnax	152:025c73b6c0a9	707	//n=n+sprintf(pbuf+n, " %x %x ", ppp.pkt.ip.x, ppp.pkt.ip.y);
nixnax	142:54d1543e23e5	708	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	709	#endif
nixnax	142:54d1543e23e5	710	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	711	#ifndef TCP_HEADER_DUMP_YES
nixnax	142:54d1543e23e5	712	putsWhileCheckingInput('\x1b[30m\n'); // there is no TCP header dump, so terminate the line with \n and VT100 code for black
nixnax	142:54d1543e23e5	713	#endif
nixnax	142:54d1543e23e5	714	#endif
nixnax	142:54d1543e23e5	715	}
nixnax	142:54d1543e23e5	716
nixnax	142:54d1543e23e5	717	/// dump a TCP header on the optional debug serial port
nixnax	142:54d1543e23e5	718	void dumpHeaderTCP(int outGoing)
nixnax	142:54d1543e23e5	719	{
nixnax	142:54d1543e23e5	720	#if defined(TCP_HEADER_DUMP_YES) && defined(SERIAL_PORT_MONITOR_YES)
nixnax	155:9c6a1d249e26	721	char flagString[9]; // text string presenting the 8 most important TCP flags
nixnax	142:54d1543e23e5	722	#define PRINT_ALL_TCP_FLAGS_YES
nixnax	142:54d1543e23e5	723	#ifdef PRINT_ALL_TCP_FLAGS_YES
nixnax	155:9c6a1d249e26	724	memset(flagString,'.', 8); // fill string with "........"
nixnax	155:9c6a1d249e26	725	if (ppp.tcp->flagFin) flagString[7]='F';
nixnax	155:9c6a1d249e26	726	if (ppp.tcp->flagSyn) flagString[6]='S';
nixnax	155:9c6a1d249e26	727	if (ppp.tcp->flagRst) flagString[5]='R';
nixnax	155:9c6a1d249e26	728	if (ppp.tcp->flagPsh) flagString[4]='P';
nixnax	155:9c6a1d249e26	729	if (ppp.tcp->flagAck) flagString[3]='A';
nixnax	155:9c6a1d249e26	730	if (ppp.tcp->flagUrg) flagString[2]='U';
nixnax	155:9c6a1d249e26	731	if (ppp.tcp->flagEce) flagString[1]='E';
nixnax	155:9c6a1d249e26	732	if (ppp.tcp->flagCwr) flagString[0]='C';
nixnax	155:9c6a1d249e26	733	flagString[8]=0; // null terminate string
nixnax	142:54d1543e23e5	734	#else
nixnax	155:9c6a1d249e26	735	if (ppp.tcp->flagAck) flagString[0]='A'; // choose only the most important flag to print
nixnax	155:9c6a1d249e26	736	if (ppp.tcp->flagSyn) flagString[0]='S';
nixnax	155:9c6a1d249e26	737	if (ppp.tcp->flagFin) flagString[0]='F';
nixnax	155:9c6a1d249e26	738	if (ppp.tcp->flagPsh) flagString[0]='P';
nixnax	155:9c6a1d249e26	739	if (ppp.tcp->flagRst) flagString[0]='R';
nixnax	155:9c6a1d249e26	740	flagString[1]=0; // null terminate string
nixnax	142:54d1543e23e5	741	#endif
nixnax	155:9c6a1d249e26	742	putsWhileCheckingInput( flagString );
nixnax	142:54d1543e23e5	743	#define EVERY_PACKET_ON_A_NEW_LINE_YES
nixnax	142:54d1543e23e5	744	#ifdef EVERY_PACKET_ON_A_NEW_LINE_YES
nixnax	142:54d1543e23e5	745	putsWhileCheckingInput("\x1b[30m\n"); // write a black color and newline after every packet
nixnax	142:54d1543e23e5	746	#endif
nixnax	155:9c6a1d249e26	747	if( outGoing && ppp.tcp->flagFin ) { // ACK/FIN - if this is an outgoing FIN its the end of a tcp conversation
nixnax	142:54d1543e23e5	748	putcWhileCheckingInput('\n'); // insert an extra new line to mark the end of an HTTP the conversation
nixnax	142:54d1543e23e5	749	}
nixnax	142:54d1543e23e5	750	#endif
nixnax	142:54d1543e23e5	751	}
nixnax	142:54d1543e23e5	752
nixnax	143:c5019f856a56	753	/// Encode a buffer in base-64
nixnax	142:54d1543e23e5	754	void enc64(char * in, char * out, int len)
nixnax	142:54d1543e23e5	755	{
nixnax	142:54d1543e23e5	756	const static char lut [] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
nixnax	142:54d1543e23e5	757	int i,j,a,b,c;
nixnax	142:54d1543e23e5	758	i=0;
nixnax	142:54d1543e23e5	759	j=0;
nixnax	142:54d1543e23e5	760	while(1) {
nixnax	142:54d1543e23e5	761	if (i<len) {
nixnax	142:54d1543e23e5	762	a = in[i++];
nixnax	142:54d1543e23e5	763	out[j++] = lut[ ( (a >> 2) & 0x3f) ];
nixnax	142:54d1543e23e5	764	} else break;
nixnax	142:54d1543e23e5	765	if (i<len) {
nixnax	142:54d1543e23e5	766	b = in[i++];
nixnax	142:54d1543e23e5	767	out[j++] = lut[ ( (a << 4) & 0x30) \| ( (b >> 4) & 0x0f) ];
nixnax	142:54d1543e23e5	768	out[j++] = lut[ ( (b << 2) & 0x3c) ];
nixnax	142:54d1543e23e5	769	} else out[j++] = '=';
nixnax	142:54d1543e23e5	770	if (i<len) {
nixnax	142:54d1543e23e5	771	c = in[i++];
nixnax	142:54d1543e23e5	772	j--;
nixnax	142:54d1543e23e5	773	out[j++] = lut[ ( (b << 2) & 0x3c) \| ( (c >> 6) & 0x03) ];
nixnax	142:54d1543e23e5	774	out[j++] = lut[ ( (c >> 0) & 0x3f) ];
nixnax	142:54d1543e23e5	775	} else out[j++] = '=';
nixnax	142:54d1543e23e5	776	}
nixnax	142:54d1543e23e5	777	out[j]=0;
nixnax	142:54d1543e23e5	778	}
nixnax	142:54d1543e23e5	779
nixnax	142:54d1543e23e5	780	/// handle a request for an http websocket
nixnax	142:54d1543e23e5	781	/// 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	782	int webSocketHandler(char * dataStart)
nixnax	142:54d1543e23e5	783	{
nixnax	142:54d1543e23e5	784	int n=0; // byte counter
nixnax	142:54d1543e23e5	785	char * key = strstr(dataStart, "Sec-WebSocket-Key: "); // search for the key in the payload
nixnax	142:54d1543e23e5	786	if (key != NULL) {
nixnax	142:54d1543e23e5	787	if (v0) putsWhileCheckingInput("WebSocket Request\n");
nixnax	142:54d1543e23e5	788	char challenge [70];
nixnax	142:54d1543e23e5	789	strncpy(challenge,key+19,70); // a local buffer
nixnax	142:54d1543e23e5	790	*strchr(challenge,'\r')=0; // insert null so we can use sprintf
nixnax	142:54d1543e23e5	791	strncat(challenge,"258EAFA5-E914-47DA-95CA-C5AB0DC85B11",70); // append websocket gui code
nixnax	142:54d1543e23e5	792	char shaOutput [20]; // sha1 output
nixnax	142:54d1543e23e5	793	sha1( shaOutput, challenge, strlen(challenge));
nixnax	142:54d1543e23e5	794	char encOut[50];
nixnax	142:54d1543e23e5	795	enc64( shaOutput, encOut, 20);
nixnax	142:54d1543e23e5	796	char * versionstring = strstr(dataStart, "Sec-WebSocket-Version:");
nixnax	142:54d1543e23e5	797	char * version = challenge;
nixnax	142:54d1543e23e5	798	strncpy(version, versionstring,70); // copy version string
nixnax	142:54d1543e23e5	799	*strchr(version,'\r')=0; // null terminate so we can sprintf it
nixnax	142:54d1543e23e5	800	memset(dataStart,0,500); // blank out old data befor send the websocket response header
nixnax	142:54d1543e23e5	801	n=n+sprintf(dataStart+n, "HTTP/1.1 101 Switching Protocols\r\n");
nixnax	142:54d1543e23e5	802	n=n+sprintf(dataStart+n, "Upgrade: websocket\r\n");
nixnax	142:54d1543e23e5	803	n=n+sprintf(dataStart+n, "Connection: Upgrade\r\n");
nixnax	142:54d1543e23e5	804	n=n+sprintf(dataStart+n, "Sec-WebSocket-Accept: %s\r\n",encOut);
nixnax	142:54d1543e23e5	805	n=n+sprintf(dataStart+n, "%s\r\n",version);
nixnax	142:54d1543e23e5	806	n=n+sprintf(dataStart+n, "mbed-Code: PPP-Blinky\r\n");
nixnax	142:54d1543e23e5	807	n=n+sprintf(dataStart+n, "\r\n"); // websocket response header ending
nixnax	142:54d1543e23e5	808	}
nixnax	142:54d1543e23e5	809	return n; // this response should satisfy a web browser's websocket protocol request
nixnax	142:54d1543e23e5	810	}
nixnax	142:54d1543e23e5	811
nixnax	142:54d1543e23e5	812	#define TCP_FLAG_ACK (1<<4)
nixnax	142:54d1543e23e5	813	#define TCP_FLAG_SYN (1<<1)
nixnax	142:54d1543e23e5	814	#define TCP_FLAG_PSH (1<<3)
nixnax	142:54d1543e23e5	815	#define TCP_FLAG_RST (1<<2)
nixnax	142:54d1543e23e5	816	#define TCP_FLAG_FIN (1<<0)
nixnax	142:54d1543e23e5	817
nixnax	142:54d1543e23e5	818	/// respond to an HTTP request
nixnax	142:54d1543e23e5	819	int httpResponse(char * dataStart)
nixnax	142:54d1543e23e5	820	{
nixnax	142:54d1543e23e5	821	int n=0; // number of bytes we have printed so far
nixnax	142:54d1543e23e5	822	n = webSocketHandler( dataStart ); // test for and handle WebSocket upgrade requests
nixnax	142:54d1543e23e5	823	if (n>0) return n; // if it's a WebSocket we already have the response, so return
nixnax	142:54d1543e23e5	824
nixnax	142:54d1543e23e5	825	int nHeader; // byte size of HTTP header
nixnax	142:54d1543e23e5	826	int contentLengthStart; // index where HTML starts
nixnax	142:54d1543e23e5	827	int httpGet5,httpGet6,httpGetx, httpGetRoot; // temporary storage of strncmp results
nixnax	142:54d1543e23e5	828
nixnax	146:a45f49a2b29c	829	ppp.responseCounter++; // increment the number of frames we have made
nixnax	142:54d1543e23e5	830
nixnax	142:54d1543e23e5	831	httpGetRoot = strncmp(dataStart, "GET / HTTP/1.", 13); // found a GET to the root directory
nixnax	142:54d1543e23e5	832	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	833	httpGet5 = dataStart[5]; // the first character in the path name, we use it for special functions later on
nixnax	142:54d1543e23e5	834	httpGet6 = dataStart[6]; // the second character in the path name, we use it for special functions later on
nixnax	142:54d1543e23e5	835	// for example, you could try this using netcat (nc): echo "GET /x" \| nc 172.10.10.2
nixnax	142:54d1543e23e5	836	if( (httpGetRoot==0) \|\| (httpGetx==0) ) {
nixnax	142:54d1543e23e5	837	n=n+sprintf(n+dataStart,"HTTP/1.1 200 OK\r\nServer: mbed-PPP-Blinky-v1\r\n"); // 200 OK header
nixnax	142:54d1543e23e5	838	} else {
nixnax	142:54d1543e23e5	839	n=n+sprintf(n+dataStart,"HTTP/1.1 404 Not Found\r\nServer: mbed-PPP-Blinky\r\n"); // 404 header
nixnax	142:54d1543e23e5	840	}
nixnax	142:54d1543e23e5	841	n=n+sprintf(n+dataStart,"Content-Length: "); // http header
nixnax	142:54d1543e23e5	842	contentLengthStart = n; // remember where Content-Length is in buffer
nixnax	142:54d1543e23e5	843	n=n+sprintf(n+dataStart,"?????\r\n"); // leave five spaces for content length - will be updated later
nixnax	142:54d1543e23e5	844	n=n+sprintf(n+dataStart,"Connection: close\r\n"); // close connection immediately
nixnax	142:54d1543e23e5	845	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	846	nHeader=n; // size of HTTP header
nixnax	142:54d1543e23e5	847	if( httpGetRoot == 0 ) {
nixnax	142:54d1543e23e5	848	// this is where we insert our web page into the buffer
nixnax	142:54d1543e23e5	849	memcpy(n+dataStart,rootWebPage,sizeof(rootWebPage));
nixnax	142:54d1543e23e5	850	n = n + sizeof(rootWebPage)-1; // one less than sizeof because we don't count the null byte at the end
nixnax	142:54d1543e23e5	851	} else if ( (httpGet5 == 'w') && (httpGet6 == 's') ) { // "ws" is a special page for websocket demo
nixnax	142:54d1543e23e5	852	memcpy(n+dataStart,webSocketPage,sizeof(webSocketPage));
nixnax	142:54d1543e23e5	853	n = n + sizeof(webSocketPage)-1; // one less than size
nixnax	142:54d1543e23e5	854	} else {
nixnax	142:54d1543e23e5	855	if (httpGetx == 0) { // the page request started with "GET /x" - here we treat anything starting with /x special:
nixnax	142:54d1543e23e5	856
nixnax	142:54d1543e23e5	857	#define W3C_COMPLIANT_RESPONSE_NO
nixnax	142:54d1543e23e5	858	// change the above to W3C_COMPLIANT_RESPONSE_YES if you want a W3C.org compliant HTTP response
nixnax	142:54d1543e23e5	859	#ifdef W3C_COMPLIANT_RESPONSE_YES
nixnax	142:54d1543e23e5	860	n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (W3C.org required elements)
nixnax	146:a45f49a2b29c	861	n=n+sprintf(n+dataStart,"<body>%d</body>",ppp.responseCounter); // body = the http frame count
nixnax	142:54d1543e23e5	862	#else
nixnax	142:54d1543e23e5	863	if( httpGet6 == 'b' ) { // if the fetched page is "xb" send a meta command to let the browser continuously reload
nixnax	142:54d1543e23e5	864	n=n+sprintf(n+dataStart, "<meta http-equiv=\"refresh\" content=\"0\">"); // reload loop - handy for benchmarking
nixnax	142:54d1543e23e5	865	}
nixnax	142:54d1543e23e5	866	// /x is a very short page, in fact, it is only a decimal number showing the http Page count
nixnax	146:a45f49a2b29c	867	n=n+sprintf(n+dataStart,"%d ",ppp.responseCounter); // not really valid html but most browsers and curl are ok with it
nixnax	142:54d1543e23e5	868	#endif
nixnax	142:54d1543e23e5	869	} else {
nixnax	142:54d1543e23e5	870	// all other requests get 404 Not Found response with a http frame count - nice for debugging
nixnax	142:54d1543e23e5	871	n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (required element)
nixnax	142:54d1543e23e5	872	n=n+sprintf(n+dataStart,"<body>Not Found</body>"); // not found message
nixnax	142:54d1543e23e5	873	}
nixnax	142:54d1543e23e5	874	}
nixnax	142:54d1543e23e5	875	#define CONTENTLENGTHSIZE 5
nixnax	142:54d1543e23e5	876	char contentLengthString[CONTENTLENGTHSIZE+1];
nixnax	142:54d1543e23e5	877	snprintf(contentLengthString,CONTENTLENGTHSIZE+1,"%*d",CONTENTLENGTHSIZE,n-nHeader); // print Content-Length with leading spaces and fixed width equal to csize
nixnax	142:54d1543e23e5	878	memcpy(dataStart+contentLengthStart, contentLengthString, CONTENTLENGTHSIZE); // copy Content-Length to it's place in the send buffer
nixnax	142:54d1543e23e5	879	return n; // total byte size of our response
nixnax	142:54d1543e23e5	880	}
nixnax	142:54d1543e23e5	881
nixnax	142:54d1543e23e5	882	/// handle TCP data that is not an HTTP get
nixnax	142:54d1543e23e5	883	/// this is the response if we have TCP data but it's not an HTTP GET
nixnax	142:54d1543e23e5	884	/// this is handy when you for example want to use netcat (nc.exe) to talk to PPP-Blinky
nixnax	142:54d1543e23e5	885	/// this could also be a websocket receive event - especially if the first byte is 0x81 (websocket data push)
nixnax	142:54d1543e23e5	886	int tcpResponse(char * dataStart, int len, int * outFlags)
nixnax	142:54d1543e23e5	887	{
nixnax	142:54d1543e23e5	888	int n=0; // number of bytes we have printed so far
nixnax	142:54d1543e23e5	889	if (dataStart[0] == 0x81) { // check if this is a websocket push message
nixnax	142:54d1543e23e5	890	// this is most likely a websocket push message. you get this when you enter this in your browser console: x.send("my message");
nixnax	142:54d1543e23e5	891	if (0) putsWhileCheckingInput( "Got data from websocket send()\n" );
nixnax	142:54d1543e23e5	892
nixnax	142:54d1543e23e5	893	// for now we simply echo the websocket data back to the client - the client should therefore see an onmessage event
nixnax	142:54d1543e23e5	894	// to display the echoed data in your browser, enter the following into the browser console: x.onmessage = function(msg){ console.log( msg.data ); }
nixnax	142:54d1543e23e5	895	if (1) {
nixnax	142:54d1543e23e5	896	char mask [4];
nixnax	142:54d1543e23e5	897	memcpy ( mask, dataStart+2, 4); // websocket messages are "masked", so first we obtain the 4-byte mask
nixnax	142:54d1543e23e5	898	int websocketMessageSize = len - 6; // 1 byte prefix (0x81), 1 byte, 4 bytes mask = 6 bytes
nixnax	142:54d1543e23e5	899	if((dataStart[1]&0x80)==0x80) // test if the mask bit is set, which means all data is xor'ed with the mask
nixnax	142:54d1543e23e5	900	for (int i=0; i<websocketMessageSize; i++) dataStart[i+6]^= mask[i%4]; // unmask each byte with one of the mask bytes
nixnax	142:54d1543e23e5	901	dataStart[1] = len-2; // add four extra bytes to the message length because we don't use mask bytes for the send
nixnax	142:54d1543e23e5	902	memcpy(dataStart+2, "Got:",4); // insert our own text into the four mask bytes
nixnax	142:54d1543e23e5	903	n = len; // our response size remains exactly the same length as what we received
nixnax	142:54d1543e23e5	904	}
nixnax	142:54d1543e23e5	905	} else if ( (dataStart[0]==0x88) && (dataStart[1]==0x80) && (len == 6) ) { // test for a websocket close request
nixnax	142:54d1543e23e5	906	n=2; // our close command is only two bytes long because we don't use the four mask bytes
nixnax	142:54d1543e23e5	907	dataStart[1]=0; // we don't have mask bytes on
nixnax	142:54d1543e23e5	908	} else if (v1) putsWhileCheckingInput("TCP data received\n");
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	142:54d1543e23e5	917	char * ipPkt = ppp.pkt.buf+4; // ip packet start
nixnax	142:54d1543e23e5	918	char * pktLen = ipPkt+2; // 2 bytes
nixnax	142:54d1543e23e5	919	char * protocol = ipPkt+9; // 1 byte
nixnax	142:54d1543e23e5	920	char * srcAdr = ipPkt+12; // 4 bytes
nixnax	154:18b2bd92f557	921
nixnax	154:18b2bd92f557	922	int packetLengthIp = __REV16(ppp.ip->lengthR ); // size of ip packet
nixnax	154:18b2bd92f557	923	int headerSizeIp = 4 * ppp.ip->headerLength; // size of ip header
nixnax	142:54d1543e23e5	924
nixnax	142:54d1543e23e5	925	// TCP header
nixnax	155:9c6a1d249e26	926
nixnax	155:9c6a1d249e26	927	ppp.tcpStart = ppp.ipStart + headerSizeIp; // calculate where the TCP header starts
nixnax	154:18b2bd92f557	928	int tcpSize = packetLengthIp - headerSizeIp; // tcp size = size of ip payload
nixnax	154:18b2bd92f557	929	char * tcp = ppp.ipStart+headerSizeIp; // start of tcp packet
nixnax	155:9c6a1d249e26	930	//char * flagbitstcp = tcp + 12; // 9 bits
nixnax	142:54d1543e23e5	931	char * windowsizetcp = tcp + 14; // 2 bytes
nixnax	142:54d1543e23e5	932	char * checksumtcp = tcp + 16; // 2 bytes
nixnax	142:54d1543e23e5	933
nixnax	154:18b2bd92f557	934	int headerSizeTcp = 4 * (ppp.tcp->offset); // tcp "offset" for start of data is also the header size
nixnax	152:025c73b6c0a9	935
nixnax	142:54d1543e23e5	936	int protocolIP = protocol[0];
nixnax	154:18b2bd92f557	937	char * tcpDataIn = tcp + headerSizeTcp; // start of data block after TCP header
nixnax	154:18b2bd92f557	938	int tcpDataSize = tcpSize - headerSizeTcp; // size of data block after TCP header
nixnax	154:18b2bd92f557	939
nixnax	154:18b2bd92f557	940	unsigned int seq_in = __REV(ppp.tcp->seqTcpR);
nixnax	154:18b2bd92f557	941	unsigned int ack_in = __REV(ppp.tcp->ackTcpR);
nixnax	142:54d1543e23e5	942	unsigned int ack_out = seq_in + tcpDataSize;
nixnax	142:54d1543e23e5	943	unsigned int seq_out = ack_in; // use their version of our current sequence number
nixnax	142:54d1543e23e5	944
nixnax	142:54d1543e23e5	945	// first we shorten the TCP response header to only 20 bytes. This means we ignore all TCP option requests
nixnax	142:54d1543e23e5	946	tcpSize = 20; // shorten total TCP packet size to 20 bytes (no data)
nixnax	154:18b2bd92f557	947	headerSizeTcp = 20; // shorten outgoing TCP header size 20 bytes
nixnax	154:18b2bd92f557	948	ppp.ip->headerLength = 5; // ip header is 20 bytes long
nixnax	154:18b2bd92f557	949	ppp.tcp->offset = (headerSizeTcp/4);
nixnax	154:18b2bd92f557	950	ppp.ip->lengthR = __REV(40);
nixnax	154:18b2bd92f557	951	char * tcpDataOut = tcp + 20; // start of outgoing data
nixnax	154:18b2bd92f557	952
nixnax	154:18b2bd92f557	953	ppp.ip->lengthR = __REV16(40);
nixnax	142:54d1543e23e5	954
nixnax	142:54d1543e23e5	955	int dataLen = 0; // most of our responses will have zero TCP data, only a header
nixnax	142:54d1543e23e5	956	int flagsOut = TCP_FLAG_ACK; // the default case is an ACK packet
nixnax	155:9c6a1d249e26	957	//int flagsTCP = ((flagbitstcp[0]&1)<<8)\|flagbitstcp[1]; // the tcp flags we received
nixnax	142:54d1543e23e5	958	windowsizetcp[0] = (700 >> 8 ); // tcp window size hi byte
nixnax	142:54d1543e23e5	959	windowsizetcp[1] = (700 & 0xff); // tcp window size lo byte
nixnax	142:54d1543e23e5	960
nixnax	142:54d1543e23e5	961	// A sparse TCP flag interpreter that implements stateless TCP connections
nixnax	142:54d1543e23e5	962
nixnax	155:9c6a1d249e26	963	switch ( ppp.tcp->flagsTcp ) {
nixnax	142:54d1543e23e5	964	case TCP_FLAG_ACK:
nixnax	142:54d1543e23e5	965	return;
nixnax	142:54d1543e23e5	966	case TCP_FLAG_SYN:
nixnax	142:54d1543e23e5	967	flagsOut = TCP_FLAG_SYN \| TCP_FLAG_ACK; // something wants to connect - acknowledge it
nixnax	142:54d1543e23e5	968	seq_out = seq_in+0x10000000U; // create a new sequence number using their sequence as a starting point, increase the highest digit
nixnax	142:54d1543e23e5	969	ack_out++; // for SYN flag we have to increase the sequence by 1
nixnax	142:54d1543e23e5	970	break;
nixnax	142:54d1543e23e5	971	case TCP_FLAG_ACK \| TCP_FLAG_PSH:
nixnax	142:54d1543e23e5	972	if ( (strncmp(tcpDataIn, "GET /", 5) == 0) ) { // check for an http GET command
nixnax	142:54d1543e23e5	973	flagsOut = TCP_FLAG_ACK \| TCP_FLAG_PSH; // set outgoing FIN flag to ask them to close from their side
nixnax	142:54d1543e23e5	974	dataLen = httpResponse(tcpDataOut); // send an http response
nixnax	142:54d1543e23e5	975	} else {
nixnax	142:54d1543e23e5	976	dataLen = tcpResponse(tcpDataOut,tcpDataSize, &flagsOut); // not a web request, send a packet reporting number of received bytes
nixnax	142:54d1543e23e5	977	}
nixnax	142:54d1543e23e5	978	break;
nixnax	142:54d1543e23e5	979	case TCP_FLAG_FIN:
nixnax	142:54d1543e23e5	980	case TCP_FLAG_FIN \| TCP_FLAG_ACK:
nixnax	142:54d1543e23e5	981	case TCP_FLAG_FIN \| TCP_FLAG_PSH \| TCP_FLAG_ACK:
nixnax	142:54d1543e23e5	982	flagsOut = TCP_FLAG_ACK \| TCP_FLAG_FIN; // set outgoing FIN flag to ask them to close from their side
nixnax	142:54d1543e23e5	983	ack_out++; // for FIN flag we have to increase the sequence by 1
nixnax	142:54d1543e23e5	984	break;
nixnax	142:54d1543e23e5	985	default:
nixnax	142:54d1543e23e5	986	return; // ignore remaining packets
nixnax	142:54d1543e23e5	987	} // switch
nixnax	142:54d1543e23e5	988
nixnax	142:54d1543e23e5	989	// The TCP flag handling is now done
nixnax	142:54d1543e23e5	990	// first we swap source and destination TCP addresses and insert the new ack and seq numbers
nixnax	147:0f40005cbc5f	991	swapIpAddresses(); // swap IP source and destination addresses
nixnax	149:969d98f6fb88	992	swapIpPorts(); // swap IP source and destination ports
nixnax	142:54d1543e23e5	993
nixnax	154:18b2bd92f557	994	ppp.tcp->ackTcpR = __REV( ack_out );
nixnax	154:18b2bd92f557	995	ppp.tcp->seqTcpR = __REV( seq_out );
nixnax	154:18b2bd92f557	996
nixnax	155:9c6a1d249e26	997	ppp.tcp->flagsTcp = flagsOut; // update the TCP flags
nixnax	142:54d1543e23e5	998
nixnax	142:54d1543e23e5	999	// increment our outgoing ip packet counter
nixnax	154:18b2bd92f557	1000	//ppp.ipData.ident++; // get next ident number for our packet
nixnax	142:54d1543e23e5	1001
nixnax	142:54d1543e23e5	1002	// Now we recalculate all the header sizes
nixnax	154:18b2bd92f557	1003	tcpSize = headerSizeTcp + dataLen; // tcp packet size
nixnax	154:18b2bd92f557	1004	int newPacketSize = headerSizeIp + tcpSize; // calculate size of the outgoing packet
nixnax	142:54d1543e23e5	1005	pktLen[0] = (newPacketSize>>8);
nixnax	142:54d1543e23e5	1006	pktLen[1]=newPacketSize; // ip total packet size
nixnax	142:54d1543e23e5	1007	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	1008
nixnax	142:54d1543e23e5	1009	// the header is all set up, now do the IP and TCP checksums
nixnax	146:a45f49a2b29c	1010	IpHeaderCheckSum(); // calculate new IP header checksum
nixnax	142:54d1543e23e5	1011
nixnax	142:54d1543e23e5	1012	// now we have to build the so-called 12-byte TCP "pseudo-header" in front of the TCP header (containing some IP header values) in order to correctly calculate the TCP checksum
nixnax	142:54d1543e23e5	1013	// this header contains the most important parts of the IP header, i.e. source and destination address, protocol number and data length.
nixnax	149:969d98f6fb88	1014	char tempHold[12]; // it's 12 long because we later reuse it when building the TCP pseudo-header
nixnax	142:54d1543e23e5	1015	char * pseudoHeader = tcp-12; // mark the start of the TCP pseudo-header
nixnax	142:54d1543e23e5	1016	memcpy(tempHold, pseudoHeader, 12); // preserve the 12 bytes of the IP header where the TCP pseudo-Header will be built
nixnax	142:54d1543e23e5	1017	memcpy( pseudoHeader+0, srcAdr, 8); // IP source and destination addresses from IP header
nixnax	142:54d1543e23e5	1018	memset( pseudoHeader+8, 0, 1); // reserved, set to zero
nixnax	142:54d1543e23e5	1019	memset( pseudoHeader+9, protocolIP, 1); // protocol from IP header
nixnax	142:54d1543e23e5	1020	memset( pseudoHeader+10, tcpSize>>8, 1); // size of IP data (TCP packet size)
nixnax	142:54d1543e23e5	1021	memset( pseudoHeader+11, tcpSize, 1); // size of IP data (TCP packet size)
nixnax	142:54d1543e23e5	1022	// pseudo-header built, now we can calculate TCP checksum
nixnax	142:54d1543e23e5	1023	checksumtcp[0]=0;
nixnax	142:54d1543e23e5	1024	checksumtcp[1]=0;
nixnax	142:54d1543e23e5	1025	unsigned int pseudoHeaderSum=dataCheckSum((unsigned char *)pseudoHeader,tcpSize+12); // calculate the TCP checksum starting at the pseudo-header
nixnax	142:54d1543e23e5	1026	checksumtcp[0]=pseudoHeaderSum>>8;
nixnax	142:54d1543e23e5	1027	checksumtcp[1]=pseudoHeaderSum;
nixnax	142:54d1543e23e5	1028	memcpy( tcp-12, tempHold, 12); // restore the 12 bytes that the pseudo-header overwrote
nixnax	147:0f40005cbc5f	1029	// IP and TCP checksums done
nixnax	142:54d1543e23e5	1030	dumpHeaderIP(1); // dump outgoing IP header
nixnax	142:54d1543e23e5	1031	dumpHeaderTCP(1); // dump outgoing TCP header
nixnax	142:54d1543e23e5	1032	for (int i=0; i<45*1000/10; i++) { // 45 ms delay before sending frame - a typical internet delay time
nixnax	142:54d1543e23e5	1033	checkPc(); // catch any incoming characters
nixnax	142:54d1543e23e5	1034	wait_us(10); // wait less than 1 character duration at 115200
nixnax	142:54d1543e23e5	1035	}
nixnax	144:01d98cf7738e	1036	sendPppFrame(); // All preparation complete - send the TCP response
nixnax	142:54d1543e23e5	1037	if(0) dumpPPPFrame(); // set to 1 to dump transmitted ppp frame
nixnax	142:54d1543e23e5	1038	memset(ppp.pkt.buf+44,0,500); // flush out traces of previous data that we may scan for
nixnax	142:54d1543e23e5	1039	}
nixnax	142:54d1543e23e5	1040
nixnax	142:54d1543e23e5	1041
nixnax	142:54d1543e23e5	1042	/// dump the TCP data to the debug serial port
nixnax	142:54d1543e23e5	1043	void dumpDataTCP()
nixnax	142:54d1543e23e5	1044	{
nixnax	142:54d1543e23e5	1045	int ipPktLen = (ppp.pkt.buf[6]<<8)\|ppp.pkt.buf[7]; // overall length of ip packet
nixnax	142:54d1543e23e5	1046	int ipHeaderLen = (ppp.pkt.buf[4]&0xf)*4; // length of ip header
nixnax	154:18b2bd92f557	1047	int headerSizeTcp = ((ppp.pkt.buf[4+ipHeaderLen+12]>>4)&0xf)*4;; // length of tcp header
nixnax	154:18b2bd92f557	1048	int dataLen = ipPktLen - ipHeaderLen - headerSizeTcp; // data is what's left after the two headers
nixnax	142:54d1543e23e5	1049	if (v1) {
nixnax	142:54d1543e23e5	1050	char pbuf[50]; // local print buffer
nixnax	142:54d1543e23e5	1051	checkPc();
nixnax	154:18b2bd92f557	1052	sprintf(pbuf, "TCP %d ipHeader %d tcpHeader %d Data %d\n", ipPktLen, ipHeaderLen, headerSizeTcp, dataLen); // 1 for more verbose
nixnax	142:54d1543e23e5	1053	checkPc();
nixnax	142:54d1543e23e5	1054	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	1055	}
nixnax	142:54d1543e23e5	1056	if (dataLen > 0) {
nixnax	154:18b2bd92f557	1057	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	1058	putsWhileCheckingInput( ppp.pkt.buf+4+ipHeaderLen+headerSizeTcp ); // print the tcp payload data
nixnax	142:54d1543e23e5	1059	putsWhileCheckingInput("\n");
nixnax	142:54d1543e23e5	1060	}
nixnax	142:54d1543e23e5	1061	}
nixnax	142:54d1543e23e5	1062
nixnax	142:54d1543e23e5	1063	/// handle an incoming TCP packet
nixnax	142:54d1543e23e5	1064	void TCPpacket()
nixnax	142:54d1543e23e5	1065	{
nixnax	142:54d1543e23e5	1066	dumpHeaderIP(0); // dump incoming packet header
nixnax	142:54d1543e23e5	1067	dumpHeaderTCP(0); // dump incoming packet header
nixnax	142:54d1543e23e5	1068	if (v2) dumpDataTCP();
nixnax	142:54d1543e23e5	1069	tcpHandler();
nixnax	142:54d1543e23e5	1070	}
nixnax	142:54d1543e23e5	1071
nixnax	142:54d1543e23e5	1072	/// handle the remaining IP protocols by ignoring them
nixnax	142:54d1543e23e5	1073	void otherProtocol()
nixnax	142:54d1543e23e5	1074	{
nixnax	142:54d1543e23e5	1075	debugPrintf("Other IP protocol");
nixnax	142:54d1543e23e5	1076	}
nixnax	142:54d1543e23e5	1077
nixnax	142:54d1543e23e5	1078	/// process an incoming IP packet
nixnax	142:54d1543e23e5	1079	void IPframe()
nixnax	142:54d1543e23e5	1080	{
nixnax	142:54d1543e23e5	1081	int protocol = ppp.pkt.buf[13];
nixnax	142:54d1543e23e5	1082	switch (protocol) {
nixnax	142:54d1543e23e5	1083	case 1:
nixnax	142:54d1543e23e5	1084	ICMPpacket();
nixnax	142:54d1543e23e5	1085	break;
nixnax	142:54d1543e23e5	1086	case 2:
nixnax	142:54d1543e23e5	1087	IGMPpacket();
nixnax	142:54d1543e23e5	1088	break;
nixnax	142:54d1543e23e5	1089	case 17:
nixnax	142:54d1543e23e5	1090	UDPpacket();
nixnax	142:54d1543e23e5	1091	break;
nixnax	142:54d1543e23e5	1092	case 6:
nixnax	142:54d1543e23e5	1093	TCPpacket();
nixnax	142:54d1543e23e5	1094	break;
nixnax	142:54d1543e23e5	1095	default:
nixnax	142:54d1543e23e5	1096	otherProtocol();
nixnax	142:54d1543e23e5	1097	}
nixnax	142:54d1543e23e5	1098	}
nixnax	142:54d1543e23e5	1099
nixnax	142:54d1543e23e5	1100	/// respond to LCP (line configuration protocol) configuration request) by allowing no options
nixnax	142:54d1543e23e5	1101	void LCPconfReq()
nixnax	142:54d1543e23e5	1102	{
nixnax	142:54d1543e23e5	1103	debugPrintf("LCP Config ");
nixnax	142:54d1543e23e5	1104	if (ppp.pkt.buf[7] != 4) {
nixnax	142:54d1543e23e5	1105	ppp.pkt.buf[4]=4; // allow only "no options" which means Maximum Receive Unit (MRU) is default 1500 bytes
nixnax	142:54d1543e23e5	1106	debugPrintf("Reject\n");
nixnax	144:01d98cf7738e	1107	sendPppFrame();
nixnax	142:54d1543e23e5	1108	} else {
nixnax	142:54d1543e23e5	1109	ppp.pkt.buf[4]=2; // ack zero conf
nixnax	142:54d1543e23e5	1110	debugPrintf("Ack\n");
nixnax	144:01d98cf7738e	1111	sendPppFrame();
nixnax	142:54d1543e23e5	1112	debugPrintf("LCP Ask\n");
nixnax	142:54d1543e23e5	1113	ppp.pkt.buf[4]=1; // request no options
nixnax	144:01d98cf7738e	1114	sendPppFrame();
nixnax	142:54d1543e23e5	1115	}
nixnax	142:54d1543e23e5	1116	}
nixnax	142:54d1543e23e5	1117
nixnax	142:54d1543e23e5	1118	/// handle LCP acknowledge packets by ignoring them
nixnax	142:54d1543e23e5	1119	void LCPconfAck()
nixnax	142:54d1543e23e5	1120	{
nixnax	142:54d1543e23e5	1121	debugPrintf("LCP Ack\n");
nixnax	142:54d1543e23e5	1122	}
nixnax	142:54d1543e23e5	1123
nixnax	143:c5019f856a56	1124	/// handle LCP end (disconnect) packets by acknowledging them and by setting ppp.online to false
nixnax	142:54d1543e23e5	1125	void LCPend()
nixnax	142:54d1543e23e5	1126	{
nixnax	142:54d1543e23e5	1127	ppp.pkt.buf[4]=6;
nixnax	144:01d98cf7738e	1128	sendPppFrame(); // acknowledge
nixnax	142:54d1543e23e5	1129	ppp.online=0; // start hunting for connect string again
nixnax	142:54d1543e23e5	1130	pppInitStruct(); // flush the receive buffer
nixnax	143:c5019f856a56	1131	debugPrintf("LCP End (Disconnect from host)\n");
nixnax	142:54d1543e23e5	1132	}
nixnax	142:54d1543e23e5	1133
nixnax	142:54d1543e23e5	1134	/// respond to other LCP requests by ignoring them
nixnax	142:54d1543e23e5	1135	void LCPother()
nixnax	142:54d1543e23e5	1136	{
nixnax	142:54d1543e23e5	1137	debugPrintf("LCP Other\n");
nixnax	142:54d1543e23e5	1138	dumpPPPFrame();
nixnax	142:54d1543e23e5	1139	}
nixnax	142:54d1543e23e5	1140
nixnax	142:54d1543e23e5	1141	/// process incoming LCP packets
nixnax	142:54d1543e23e5	1142	void LCPframe()
nixnax	142:54d1543e23e5	1143	{
nixnax	142:54d1543e23e5	1144	int code = ppp.pkt.buf[4];
nixnax	142:54d1543e23e5	1145	switch (code) {
nixnax	142:54d1543e23e5	1146	case 1:
nixnax	142:54d1543e23e5	1147	LCPconfReq();
nixnax	142:54d1543e23e5	1148	break; // config request
nixnax	142:54d1543e23e5	1149	case 2:
nixnax	142:54d1543e23e5	1150	LCPconfAck();
nixnax	142:54d1543e23e5	1151	break; // config ack
nixnax	142:54d1543e23e5	1152	case 5:
nixnax	142:54d1543e23e5	1153	LCPend();
nixnax	142:54d1543e23e5	1154	break; // end connection
nixnax	142:54d1543e23e5	1155	default:
nixnax	142:54d1543e23e5	1156	LCPother();
nixnax	142:54d1543e23e5	1157	}
nixnax	142:54d1543e23e5	1158	}
nixnax	142:54d1543e23e5	1159
nixnax	142:54d1543e23e5	1160	/// discard packets that are not IP, IPCP, or LCP
nixnax	142:54d1543e23e5	1161	void discardedFrame()
nixnax	142:54d1543e23e5	1162	{
nixnax	142:54d1543e23e5	1163	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	1164	}
nixnax	142:54d1543e23e5	1165
nixnax	142:54d1543e23e5	1166	/// determine the packet type (IP, IPCP or LCP) of incoming packets
nixnax	142:54d1543e23e5	1167	void determinePacketType()
nixnax	142:54d1543e23e5	1168	{
nixnax	142:54d1543e23e5	1169	if ( ppp.pkt.buf[0] != 0xff ) {
nixnax	142:54d1543e23e5	1170	debugPrintf("byte0 != ff\n");
nixnax	142:54d1543e23e5	1171	return;
nixnax	142:54d1543e23e5	1172	}
nixnax	142:54d1543e23e5	1173	if ( ppp.pkt.buf[1] != 3 ) {
nixnax	142:54d1543e23e5	1174	debugPrintf("byte1 != 3\n");
nixnax	142:54d1543e23e5	1175	return;
nixnax	142:54d1543e23e5	1176	}
nixnax	142:54d1543e23e5	1177	if ( ppp.pkt.buf[3] != 0x21 ) {
nixnax	142:54d1543e23e5	1178	debugPrintf("byte2 != 21\n");
nixnax	142:54d1543e23e5	1179	return;
nixnax	142:54d1543e23e5	1180	}
nixnax	142:54d1543e23e5	1181	int packetType = ppp.pkt.buf[2];
nixnax	142:54d1543e23e5	1182	switch (packetType) {
nixnax	142:54d1543e23e5	1183	case 0xc0:
nixnax	142:54d1543e23e5	1184	LCPframe();
nixnax	142:54d1543e23e5	1185	break; // link control
nixnax	142:54d1543e23e5	1186	case 0x80:
nixnax	142:54d1543e23e5	1187	IPCPframe();
nixnax	142:54d1543e23e5	1188	break; // IP control
nixnax	142:54d1543e23e5	1189	case 0x00:
nixnax	142:54d1543e23e5	1190	IPframe();
nixnax	142:54d1543e23e5	1191	break; // IP itself
nixnax	142:54d1543e23e5	1192	default:
nixnax	142:54d1543e23e5	1193	discardedFrame();
nixnax	142:54d1543e23e5	1194	}
nixnax	142:54d1543e23e5	1195	}
nixnax	142:54d1543e23e5	1196
nixnax	146:a45f49a2b29c	1197	/// a sniffer tool to assist in figuring out where in the code we are having characters in the input buffer
nixnax	146:a45f49a2b29c	1198	void sniff()
nixnax	146:a45f49a2b29c	1199	{
nixnax	146:a45f49a2b29c	1200	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	1201	}
nixnax	146:a45f49a2b29c	1202
nixnax	142:54d1543e23e5	1203	/// scan the PPP serial input stream for frame start markers
nixnax	143:c5019f856a56	1204	void waitForPppFrame()
nixnax	142:54d1543e23e5	1205	{
nixnax	142:54d1543e23e5	1206	while(1) {
nixnax	142:54d1543e23e5	1207	checkPc(); // handle received characters
nixnax	142:54d1543e23e5	1208	if ( ppp.rx.head != ppp.rx.tail ) {
nixnax	142:54d1543e23e5	1209	int oldTail = ppp.rx.tail; // remember where the character is located in the buffer
nixnax	142:54d1543e23e5	1210	int rx = pc_getBuf(); // get the character
nixnax	142:54d1543e23e5	1211	if (rx==FRAME_7E) {
nixnax	142:54d1543e23e5	1212	if (ppp.firstFrame) { // is this the start of the first frame start
nixnax	142:54d1543e23e5	1213	ppp.firstFrame=0;
nixnax	142:54d1543e23e5	1214	ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
nixnax	142:54d1543e23e5	1215	ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where first frame started
nixnax	142:54d1543e23e5	1216	} else {
nixnax	142:54d1543e23e5	1217	ppp.hdlc.frameEndIndex=oldTail; // mark the frame end character
nixnax	142:54d1543e23e5	1218	processPPPFrame(ppp.hdlc.frameStartIndex, ppp.hdlc.frameEndIndex); // process the frame
nixnax	142:54d1543e23e5	1219	ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
nixnax	142:54d1543e23e5	1220	ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where next frame started
nixnax	142:54d1543e23e5	1221	break;
nixnax	142:54d1543e23e5	1222	}
nixnax	142:54d1543e23e5	1223	}
nixnax	142:54d1543e23e5	1224	}
nixnax	142:54d1543e23e5	1225	}
nixnax	142:54d1543e23e5	1226	}
nixnax	142:54d1543e23e5	1227
nixnax	153:7993def8663f	1228	/// 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	1229	// Note: a 0x7E in the input stream (ppp start of frame character) will also set ppp.online to true - see checkPc();
nixnax	153:7993def8663f	1230	void waitForPcConnectString()
nixnax	142:54d1543e23e5	1231	{
nixnax	142:54d1543e23e5	1232	while(ppp.online == 0) {
nixnax	142:54d1543e23e5	1233	checkPc(); // gather received characters
nixnax	142:54d1543e23e5	1234	// search for Windows Dialup Networking "Direct Connection Between Two Computers" expected connect string
nixnax	142:54d1543e23e5	1235	char * found1 = strstr( (char *)ppp.rx.buf, "CLIENT" );
nixnax	142:54d1543e23e5	1236	if (found1 != NULL) {
nixnax	142:54d1543e23e5	1237	// respond with Windows Dialup networking expected "Direct Connection Between Two Computers" response string
nixnax	143:c5019f856a56	1238	if (v0) debugPrintf("Connected: Found connect string \"CLIENT\", sent \"CLIENTSERVER\"\n");
nixnax	142:54d1543e23e5	1239	pc.puts("CLIENTSERVER");
nixnax	142:54d1543e23e5	1240	ppp.online=1; // we are connected - set flag so we stop looking for the connect string
nixnax	142:54d1543e23e5	1241	checkPc();
nixnax	142:54d1543e23e5	1242	}
nixnax	142:54d1543e23e5	1243	}
nixnax	142:54d1543e23e5	1244	}
nixnax	142:54d1543e23e5	1245
nixnax	144:01d98cf7738e	1246	/// Initialize PPP data structure and set serial port(s) baud rate(s)
nixnax	144:01d98cf7738e	1247	void initializePpp()
nixnax	142:54d1543e23e5	1248	{
nixnax	142:54d1543e23e5	1249	pc.baud(115200); // USB serial port to pc
nixnax	144:01d98cf7738e	1250	debugBaudRate(115200); // baud rate for (optional) debug serial port
nixnax	142:54d1543e23e5	1251	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	1252	pppInitStruct(); // initialize all the PPP properties
nixnax	143:c5019f856a56	1253	}

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

The code in this repository is MIT licensed.