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@163:d1b4328e9f08, 2017-09-03 (annotated)

Committer:: nixnax
Date:: Sun Sep 03 01:29:01 2017 +0000
Revision:: 163:d1b4328e9f08
Parent:: 162:594729c0e5c1
Child:: 164:c3de3d212c4b

UDP header structure. Rewrite udp handler.

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	157:3a3530d60e96	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	142:54d1543e23e5	158	/// a structure to keep all our ppp globals in
nixnax	142:54d1543e23e5	159	struct pppType {
nixnax	154:18b2bd92f557	160	pppHeaderType * ppp; // pointer to ppp struct
nixnax	154:18b2bd92f557	161	union {
nixnax	154:18b2bd92f557	162	ipHeaderType * ip; // pointer to ip header struct
nixnax	155:9c6a1d249e26	163	char * ipStart; // char pointer to ip header struct (need a char pointer for byte offset calculations)
nixnax	154:18b2bd92f557	164	};
nixnax	154:18b2bd92f557	165	union {
nixnax	154:18b2bd92f557	166	tcpHeaderType * tcp; // pointer to tcp header struct
nixnax	155:9c6a1d249e26	167	char * tcpStart; // char pointer to tcp header struct (need a char pointer for byte offset calculations)
nixnax	163:d1b4328e9f08	168	udpHeaderType * udp; // pointer to udp header struct
nixnax	163:d1b4328e9f08	169	char * udpStart; // char pointer to udp header struct (need a char pointer for byte offset calculations)
nixnax	160:bd701ad564cb	170	};
nixnax	142:54d1543e23e5	171	int online; // we hunt for a PPP connection if this is zero
nixnax	143:c5019f856a56	172	int hostIP; // ip address of host
nixnax	145:098b6ed2f7f2	173	int fcs; // PPP "frame check sequence" - a 16-bit HDLC-like checksum used in all PPP frames
nixnax	142:54d1543e23e5	174	int ledState; // state of LED1
nixnax	146:a45f49a2b29c	175	int responseCounter;
nixnax	142:54d1543e23e5	176	int firstFrame; // cleared after first frame
nixnax	159:4d1bf96a59cd	177	unsigned int sum; // a checksum used in headers
nixnax	142:54d1543e23e5	178	struct {
nixnax	142:54d1543e23e5	179	#define RXBUFLEN (1<<11)
nixnax	142:54d1543e23e5	180	// the serial port receive buffer and packet buffer, size is RXBUFLEN (currently 2048 bytes)
nixnax	142:54d1543e23e5	181	char buf[RXBUFLEN]; // RXBUFLEN MUST be a power of two because we use & operator for fast wrap-around in ring buffer
nixnax	142:54d1543e23e5	182	int head;
nixnax	142:54d1543e23e5	183	int tail;
nixnax	142:54d1543e23e5	184	int rtail;
nixnax	142:54d1543e23e5	185	int buflevel;
nixnax	142:54d1543e23e5	186	} rx; // serial port objects
nixnax	142:54d1543e23e5	187	struct {
nixnax	142:54d1543e23e5	188	int len; // number of bytes in buffer
nixnax	142:54d1543e23e5	189	int crc; // PPP CRC (frame check)
nixnax	152:025c73b6c0a9	190	#define PPP_max_size 1600
nixnax	152:025c73b6c0a9	191	// we are assuming 100 bytes more than MTU size of 1500
nixnax	154:18b2bd92f557	192	char buf[PPP_max_size]; // send and receive buffer large enough for largest IP packet
nixnax	142:54d1543e23e5	193	} pkt; // ppp buffer objects
nixnax	142:54d1543e23e5	194	struct {
nixnax	142:54d1543e23e5	195	int frameStartIndex; // frame start marker
nixnax	142:54d1543e23e5	196	int frameEndIndex; // frame end marker
nixnax	142:54d1543e23e5	197	} hdlc; // hdlc frame objects
nixnax	142:54d1543e23e5	198	struct {
nixnax	142:54d1543e23e5	199	unsigned int ident; // our IP ident value (outgoing frame count)
nixnax	154:18b2bd92f557	200	} ipData; // ip related object
nixnax	142:54d1543e23e5	201	};
nixnax	142:54d1543e23e5	202
nixnax	142:54d1543e23e5	203	pppType ppp; // our global - definitely not thread safe
nixnax	142:54d1543e23e5	204
nixnax	142:54d1543e23e5	205	/// Initialize the ppp structure and clear the receive buffer
nixnax	142:54d1543e23e5	206	void pppInitStruct()
nixnax	142:54d1543e23e5	207	{
nixnax	142:54d1543e23e5	208	memset( ppp.rx.buf, 0, RXBUFLEN);
nixnax	142:54d1543e23e5	209	ppp.online=0;
nixnax	142:54d1543e23e5	210	ppp.rx.tail=0;
nixnax	142:54d1543e23e5	211	ppp.rx.rtail=0;
nixnax	142:54d1543e23e5	212	ppp.rx.head=0;
nixnax	142:54d1543e23e5	213	ppp.rx.buflevel=0;
nixnax	142:54d1543e23e5	214	ppp.pkt.len=0;
nixnax	154:18b2bd92f557	215	ppp.ipData.ident=10000; // easy to recognize in ip packet dumps
nixnax	142:54d1543e23e5	216	ppp.ledState=0;
nixnax	142:54d1543e23e5	217	ppp.hdlc.frameStartIndex=0;
nixnax	146:a45f49a2b29c	218	ppp.responseCounter=0;
nixnax	142:54d1543e23e5	219	ppp.firstFrame=1;
nixnax	154:18b2bd92f557	220	ppp.ppp = (pppHeaderType *)ppp.pkt.buf;
nixnax	154:18b2bd92f557	221	ppp.ip = (ipHeaderType *)(ppp.pkt.buf+4); // ppp header is 4 bytes long
nixnax	142:54d1543e23e5	222	}
nixnax	142:54d1543e23e5	223
nixnax	142:54d1543e23e5	224	/// Toggle the LED on every second PPP packet received
nixnax	142:54d1543e23e5	225	void led1Toggle()
nixnax	142:54d1543e23e5	226	{
nixnax	142:54d1543e23e5	227	led1 = (ppp.ledState >> 1) & 1; // use second bit, in other words toggle LED only every second packet
nixnax	143:c5019f856a56	228	ppp.ledState++;
nixnax	142:54d1543e23e5	229	}
nixnax	142:54d1543e23e5	230
nixnax	152:025c73b6c0a9	231	/// returns 1 after a connect message, 0 at startup or after a disconnect message
nixnax	150:3366bf3d294e	232	int connectedPpp()
nixnax	142:54d1543e23e5	233	{
nixnax	142:54d1543e23e5	234	return ppp.online;
nixnax	143:c5019f856a56	235	}
nixnax	142:54d1543e23e5	236
nixnax	143:c5019f856a56	237	/// Check for available characters from the PC and read them into our own circular serial receive buffer at ppp.rx.buf.
nixnax	143:c5019f856a56	238	/// Also, if we are offline and a 0x7e frame start character is seen, we go online immediately
nixnax	142:54d1543e23e5	239	void checkPc()
nixnax	142:54d1543e23e5	240	{
nixnax	142:54d1543e23e5	241	char ch;
nixnax	142:54d1543e23e5	242	if ( pc.readable() ) {
nixnax	142:54d1543e23e5	243	int hd = (ppp.rx.head+1)&(RXBUFLEN-1); // increment/wrap head index
nixnax	142:54d1543e23e5	244	if ( hd == ppp.rx.rtail ) {
nixnax	142:54d1543e23e5	245	debugPrintf("\nReceive buffer full\n");
nixnax	142:54d1543e23e5	246	return;
nixnax	142:54d1543e23e5	247	}
nixnax	142:54d1543e23e5	248	ch = pc.getc(); // read new character
nixnax	142:54d1543e23e5	249	ppp.rx.buf[ppp.rx.head] = ch; // insert in our receive buffer
nixnax	142:54d1543e23e5	250	if ( ppp.online == 0 ) {
nixnax	142:54d1543e23e5	251	if (ch == 0x7E) {
nixnax	142:54d1543e23e5	252	ppp.online = 1;
nixnax	142:54d1543e23e5	253	}
nixnax	142:54d1543e23e5	254	}
nixnax	142:54d1543e23e5	255	ppp.rx.head = hd; // update head pointer
nixnax	142:54d1543e23e5	256	ppp.rx.buflevel++;
nixnax	142:54d1543e23e5	257	}
nixnax	142:54d1543e23e5	258	}
nixnax	142:54d1543e23e5	259
nixnax	142:54d1543e23e5	260	/// print to debug port while checking for incoming characters
nixnax	142:54d1543e23e5	261	void putcWhileCheckingInput( char outByte )
nixnax	142:54d1543e23e5	262	{
nixnax	142:54d1543e23e5	263	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	264	checkPc();
nixnax	142:54d1543e23e5	265	debugPutc( outByte );
nixnax	142:54d1543e23e5	266	checkPc();
nixnax	142:54d1543e23e5	267	#endif
nixnax	142:54d1543e23e5	268	}
nixnax	142:54d1543e23e5	269
nixnax	142:54d1543e23e5	270	/// puts to debug port while checking the PPP input stream
nixnax	142:54d1543e23e5	271	void putsWhileCheckingInput( char * data )
nixnax	142:54d1543e23e5	272	{
nixnax	142:54d1543e23e5	273	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	274	char * nextChar = data;
nixnax	142:54d1543e23e5	275	while( *nextChar != 0 ) {
nixnax	142:54d1543e23e5	276	putcWhileCheckingInput( *nextChar ); // write one character to debug port while checking input
nixnax	142:54d1543e23e5	277	nextChar++;
nixnax	142:54d1543e23e5	278	}
nixnax	142:54d1543e23e5	279	#endif
nixnax	142:54d1543e23e5	280	}
nixnax	142:54d1543e23e5	281
nixnax	145:098b6ed2f7f2	282	/// Initialize the PPP FCS (frame check sequence) total
nixnax	145:098b6ed2f7f2	283	void fcsReset()
nixnax	142:54d1543e23e5	284	{
nixnax	145:098b6ed2f7f2	285	ppp.fcs=0xffff; // crc restart
nixnax	142:54d1543e23e5	286	}
nixnax	142:54d1543e23e5	287
nixnax	145:098b6ed2f7f2	288	/// update the cumulative PPP FCS (frame check sequence)
nixnax	145:098b6ed2f7f2	289	void fcsDo(int x)
nixnax	142:54d1543e23e5	290	{
nixnax	142:54d1543e23e5	291	for (int i=0; i<8; i++) {
nixnax	145:098b6ed2f7f2	292	ppp.fcs=((ppp.fcs&1)^(x&1))?(ppp.fcs>>1)^0x8408:ppp.fcs>>1; // crc calculator
nixnax	142:54d1543e23e5	293	x>>=1;
nixnax	142:54d1543e23e5	294	}
nixnax	142:54d1543e23e5	295	checkPc(); // handle input
nixnax	142:54d1543e23e5	296	}
nixnax	142:54d1543e23e5	297
nixnax	145:098b6ed2f7f2	298	/// calculate the PPP FCS (frame check sequence) on an entire block of memory
nixnax	145:098b6ed2f7f2	299	int fcsBuf(char * buf, int size) // crc on an entire block of memory
nixnax	142:54d1543e23e5	300	{
nixnax	145:098b6ed2f7f2	301	fcsReset();
nixnax	145:098b6ed2f7f2	302	for(int i=0; i<size; i++)fcsDo(*buf++);
nixnax	145:098b6ed2f7f2	303	return ppp.fcs;
nixnax	142:54d1543e23e5	304	}
nixnax	142:54d1543e23e5	305
nixnax	142:54d1543e23e5	306	/// Get one character from our received PPP buffer
nixnax	142:54d1543e23e5	307	int pc_getBuf()
nixnax	142:54d1543e23e5	308	{
nixnax	142:54d1543e23e5	309	int x = ppp.rx.buf[ ppp.rx.tail ];
nixnax	142:54d1543e23e5	310	ppp.rx.tail=(ppp.rx.tail+1)&(RXBUFLEN-1);
nixnax	142:54d1543e23e5	311	ppp.rx.buflevel--;
nixnax	142:54d1543e23e5	312	return x;
nixnax	142:54d1543e23e5	313	}
nixnax	142:54d1543e23e5	314
nixnax	142:54d1543e23e5	315	/// Dump a PPP frame to the debug serial port
nixnax	142:54d1543e23e5	316	/// Note - the hex output of dumpPPPFrame() can be imported into WireShark
nixnax	142:54d1543e23e5	317	/// Capture the frame's hex output in your terminal program and save as a text file
nixnax	142:54d1543e23e5	318	/// In WireShark, use "Import Hex File". Options are: Offset=None, Protocol=PPP.
nixnax	142:54d1543e23e5	319	void dumpPPPFrame()
nixnax	142:54d1543e23e5	320	{
nixnax	142:54d1543e23e5	321	char pbuf[30];
nixnax	142:54d1543e23e5	322	for(int i=0; i<ppp.pkt.len; i++) {
nixnax	142:54d1543e23e5	323	checkPc();
nixnax	142:54d1543e23e5	324	sprintf(pbuf, "%02x ", ppp.pkt.buf[i]);
nixnax	142:54d1543e23e5	325	checkPc();
nixnax	142:54d1543e23e5	326	putsWhileCheckingInput(pbuf);
nixnax	142:54d1543e23e5	327	}
nixnax	142:54d1543e23e5	328	checkPc();
nixnax	142:54d1543e23e5	329	sprintf(pbuf, " CRC=%04x Len=%d\n", ppp.pkt.crc, ppp.pkt.len);
nixnax	142:54d1543e23e5	330	checkPc();
nixnax	142:54d1543e23e5	331	putsWhileCheckingInput(pbuf);
nixnax	142:54d1543e23e5	332	}
nixnax	142:54d1543e23e5	333
nixnax	142:54d1543e23e5	334	/// Process a received PPP frame
nixnax	142:54d1543e23e5	335	void processPPPFrame(int start, int end)
nixnax	142:54d1543e23e5	336	{
nixnax	142:54d1543e23e5	337	led1Toggle(); // change led1 state on every frame we receive
nixnax	142:54d1543e23e5	338	if(start==end) {
nixnax	142:54d1543e23e5	339	return; // empty frame
nixnax	142:54d1543e23e5	340	}
nixnax	145:098b6ed2f7f2	341	fcsReset();
nixnax	142:54d1543e23e5	342	char * dest = ppp.pkt.buf;
nixnax	142:54d1543e23e5	343	ppp.pkt.len=0;
nixnax	142:54d1543e23e5	344	int unstuff=0;
nixnax	142:54d1543e23e5	345	int idx = start;
nixnax	142:54d1543e23e5	346	while(1) {
nixnax	142:54d1543e23e5	347	checkPc();
nixnax	142:54d1543e23e5	348	if (unstuff==0) {
nixnax	142:54d1543e23e5	349	if (ppp.rx.buf[idx]==0x7d) unstuff=1;
nixnax	142:54d1543e23e5	350	else {
nixnax	142:54d1543e23e5	351	*dest = ppp.rx.buf[idx];
nixnax	142:54d1543e23e5	352	ppp.pkt.len++;
nixnax	142:54d1543e23e5	353	dest++;
nixnax	145:098b6ed2f7f2	354	fcsDo(ppp.rx.buf[idx]);
nixnax	142:54d1543e23e5	355	}
nixnax	142:54d1543e23e5	356	} else { // unstuff characters prefixed with 0x7d
nixnax	142:54d1543e23e5	357	*dest = ppp.rx.buf[idx]^0x20;
nixnax	142:54d1543e23e5	358	ppp.pkt.len++;
nixnax	142:54d1543e23e5	359	dest++;
nixnax	145:098b6ed2f7f2	360	fcsDo(ppp.rx.buf[idx]^0x20);
nixnax	142:54d1543e23e5	361	unstuff=0;
nixnax	142:54d1543e23e5	362	}
nixnax	142:54d1543e23e5	363	idx = (idx+1) & (RXBUFLEN-1);
nixnax	142:54d1543e23e5	364	if (idx == end) break;
nixnax	142:54d1543e23e5	365	}
nixnax	145:098b6ed2f7f2	366	ppp.pkt.crc = ppp.fcs & 0xffff;
nixnax	142:54d1543e23e5	367	if(0) dumpPPPFrame(); // set to 1 to dump ALL ppp frames
nixnax	142:54d1543e23e5	368	if (ppp.pkt.crc == 0xf0b8) { // check for good CRC
nixnax	142:54d1543e23e5	369	determinePacketType();
nixnax	142:54d1543e23e5	370	} else {
nixnax	142:54d1543e23e5	371	#define REPORT_FCS_ERROR_YES
nixnax	142:54d1543e23e5	372	#ifdef REPORT_FCS_ERROR_YES
nixnax	142:54d1543e23e5	373	char pbuf[50]; // local print buffer
nixnax	142:54d1543e23e5	374	checkPc();
nixnax	142:54d1543e23e5	375	sprintf(pbuf, "\nPPP FCS(crc) Error CRC=%x Length = %d\n",ppp.pkt.crc,ppp.pkt.len); // print a debug line
nixnax	142:54d1543e23e5	376	checkPc();
nixnax	142:54d1543e23e5	377	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	378	if(0) dumpPPPFrame(); // set to 1 to dump frames with errors in them
nixnax	142:54d1543e23e5	379	#endif
nixnax	142:54d1543e23e5	380	}
nixnax	142:54d1543e23e5	381	}
nixnax	142:54d1543e23e5	382
nixnax	142:54d1543e23e5	383	/// output a character to the PPP port while checking for incoming characters
nixnax	142:54d1543e23e5	384	void pcPutcWhileCheckingInput(int ch)
nixnax	142:54d1543e23e5	385	{
nixnax	142:54d1543e23e5	386	checkPc(); // check input
nixnax	142:54d1543e23e5	387	pc.putc(ch);
nixnax	142:54d1543e23e5	388	checkPc();
nixnax	142:54d1543e23e5	389	}
nixnax	142:54d1543e23e5	390
nixnax	142:54d1543e23e5	391	/// do PPP HDLC-like handling of special (flag) characters
nixnax	143:c5019f856a56	392	void hdlcPut(int ch)
nixnax	142:54d1543e23e5	393	{
nixnax	142:54d1543e23e5	394	if ( (ch<0x20) \|\| (ch==0x7d) \|\| (ch==0x7e) ) {
nixnax	142:54d1543e23e5	395	pcPutcWhileCheckingInput(0x7d);
nixnax	142:54d1543e23e5	396	pcPutcWhileCheckingInput(ch^0x20); // these characters need special handling
nixnax	142:54d1543e23e5	397	} else {
nixnax	142:54d1543e23e5	398	pcPutcWhileCheckingInput(ch);
nixnax	142:54d1543e23e5	399	}
nixnax	142:54d1543e23e5	400	}
nixnax	142:54d1543e23e5	401
nixnax	142:54d1543e23e5	402	/// send a PPP frame in HDLC format
nixnax	144:01d98cf7738e	403	void sendPppFrame()
nixnax	143:c5019f856a56	404	{
nixnax	145:098b6ed2f7f2	405	int crc = fcsBuf(ppp.pkt.buf, ppp.pkt.len-2); // update crc
nixnax	142:54d1543e23e5	406	ppp.pkt.buf[ ppp.pkt.len-2 ] = (~crc>>0); // fcs lo (crc)
nixnax	142:54d1543e23e5	407	ppp.pkt.buf[ ppp.pkt.len-1 ] = (~crc>>8); // fcs hi (crc)
nixnax	142:54d1543e23e5	408	pcPutcWhileCheckingInput(0x7e); // hdlc start-of-frame "flag"
nixnax	142:54d1543e23e5	409	for(int i=0; i<ppp.pkt.len; i++) {
nixnax	142:54d1543e23e5	410	wait_us(86); // wait one character time
nixnax	142:54d1543e23e5	411	checkPc();
nixnax	142:54d1543e23e5	412	hdlcPut( ppp.pkt.buf[i] ); // send a character
nixnax	142:54d1543e23e5	413	}
nixnax	142:54d1543e23e5	414	pcPutcWhileCheckingInput(0x7e); // hdlc end-of-frame "flag"
nixnax	142:54d1543e23e5	415	}
nixnax	142:54d1543e23e5	416
nixnax	143:c5019f856a56	417	/// 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	418	int bufferToIP(char * buffer)
nixnax	143:c5019f856a56	419	{
nixnax	143:c5019f856a56	420	int result=0;
nixnax	143:c5019f856a56	421	for(int i=0; i<4; i++) result = (result<<8)\|(*buffer++ & 0xff);
nixnax	143:c5019f856a56	422	return result;
nixnax	143:c5019f856a56	423	}
nixnax	143:c5019f856a56	424
nixnax	142:54d1543e23e5	425	/// handle IPCP configuration requests
nixnax	142:54d1543e23e5	426	void ipcpConfigRequestHandler()
nixnax	142:54d1543e23e5	427	{
nixnax	142:54d1543e23e5	428	debugPrintf("Their IPCP Config Req, Our Ack\n");
nixnax	143:c5019f856a56	429	if(ppp.pkt.buf[8]==3) {
nixnax	143:c5019f856a56	430	ppp.hostIP = bufferToIP(ppp.pkt.buf+10);
nixnax	143:c5019f856a56	431	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	432	}
nixnax	143:c5019f856a56	433
nixnax	142:54d1543e23e5	434	ppp.pkt.buf[4]=2; // change code to ack
nixnax	144:01d98cf7738e	435	sendPppFrame(); // acknowledge everything they ask for - assume it's IP addresses
nixnax	142:54d1543e23e5	436
nixnax	142:54d1543e23e5	437	debugPrintf("Our IPCP Ask (no options)\n");
nixnax	142:54d1543e23e5	438	ppp.pkt.buf[4]=1; // change code to request
nixnax	142:54d1543e23e5	439	ppp.pkt.buf[7]=4; // no options in this request
nixnax	142:54d1543e23e5	440	ppp.pkt.len=10; // no options in this request shortest ipcp packet possible (4 ppp + 4 ipcp + 2 crc)
nixnax	144:01d98cf7738e	441	sendPppFrame(); // send our request
nixnax	142:54d1543e23e5	442	}
nixnax	142:54d1543e23e5	443
nixnax	142:54d1543e23e5	444	/// handle IPCP acknowledge (do nothing)
nixnax	142:54d1543e23e5	445	void ipcpAckHandler()
nixnax	142:54d1543e23e5	446	{
nixnax	142:54d1543e23e5	447	debugPrintf("Their IPCP Grant\n");
nixnax	142:54d1543e23e5	448	}
nixnax	142:54d1543e23e5	449
nixnax	143:c5019f856a56	450	/// Handle IPCP NACK by sending our suggested IP address if there is an IP involved.
nixnax	143:c5019f856a56	451	/// 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	452	void ipcpNackHandler()
nixnax	142:54d1543e23e5	453	{
nixnax	146:a45f49a2b29c	454	debugPrintf("Their IPCP Nack\n");
nixnax	142:54d1543e23e5	455	if (ppp.pkt.buf[8]==3) { // check if the NACK contains an IP address parameter
nixnax	142:54d1543e23e5	456	ppp.pkt.buf[4]=1; // assume the NACK contains our "suggested" IP address
nixnax	144:01d98cf7738e	457	sendPppFrame(); // let's request this IP address as ours
nixnax	143:c5019f856a56	458	debugPrintf("Our IPCP ACK (received an IP)\n");
nixnax	146:a45f49a2b29c	459	} else { // if it's not an IP nack we ignore it
nixnax	146:a45f49a2b29c	460	debugPrintf("IPCP Nack Ignored\n");
nixnax	146:a45f49a2b29c	461	}
nixnax	142:54d1543e23e5	462	}
nixnax	142:54d1543e23e5	463
nixnax	142:54d1543e23e5	464	/// handle all other IPCP requests (by ignoring them)
nixnax	142:54d1543e23e5	465	void ipcpDefaultHandler()
nixnax	142:54d1543e23e5	466	{
nixnax	142:54d1543e23e5	467	debugPrintf("Their IPCP Other\n");
nixnax	142:54d1543e23e5	468	}
nixnax	142:54d1543e23e5	469
nixnax	142:54d1543e23e5	470	/// process an incoming IPCP packet
nixnax	142:54d1543e23e5	471	void IPCPframe()
nixnax	142:54d1543e23e5	472	{
nixnax	142:54d1543e23e5	473	int code = ppp.pkt.buf[4]; // packet type is here
nixnax	142:54d1543e23e5	474	switch (code) {
nixnax	142:54d1543e23e5	475	case 1:
nixnax	142:54d1543e23e5	476	ipcpConfigRequestHandler();
nixnax	142:54d1543e23e5	477	break;
nixnax	142:54d1543e23e5	478	case 2:
nixnax	142:54d1543e23e5	479	ipcpAckHandler();
nixnax	142:54d1543e23e5	480	break;
nixnax	142:54d1543e23e5	481	case 3:
nixnax	142:54d1543e23e5	482	ipcpNackHandler();
nixnax	142:54d1543e23e5	483	break;
nixnax	142:54d1543e23e5	484	default:
nixnax	142:54d1543e23e5	485	ipcpDefaultHandler();
nixnax	142:54d1543e23e5	486	}
nixnax	142:54d1543e23e5	487	}
nixnax	142:54d1543e23e5	488
nixnax	142:54d1543e23e5	489	/// perform a 16-bit checksum. if the byte count is odd, stuff in an extra zero byte.
nixnax	161:d59f778bc8ab	490	unsigned int dataCheckSum(char * ptr, int len, int restart)
nixnax	142:54d1543e23e5	491	{
nixnax	159:4d1bf96a59cd	492	unsigned int i,hi,lo;
nixnax	142:54d1543e23e5	493	unsigned char placeHolder;
nixnax	161:d59f778bc8ab	494	if (restart) ppp.sum=0;
nixnax	142:54d1543e23e5	495	if (len&1) {
nixnax	142:54d1543e23e5	496	placeHolder = ptr[len];
nixnax	142:54d1543e23e5	497	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	498	}
nixnax	142:54d1543e23e5	499	i=0;
nixnax	142:54d1543e23e5	500	while ( i<len ) {
nixnax	142:54d1543e23e5	501	checkPc();
nixnax	142:54d1543e23e5	502	hi = ptr[i++];
nixnax	142:54d1543e23e5	503	lo = ptr[i++];
nixnax	159:4d1bf96a59cd	504	ppp.sum = ppp.sum + ((hi<<8)\|lo);
nixnax	142:54d1543e23e5	505	}
nixnax	142:54d1543e23e5	506	if (len&1) {
nixnax	142:54d1543e23e5	507	ptr[len] = placeHolder; // restore the extra byte we made zero
nixnax	142:54d1543e23e5	508	}
nixnax	159:4d1bf96a59cd	509	ppp.sum = (ppp.sum & 0xffff) + (ppp.sum>>16);
nixnax	159:4d1bf96a59cd	510	ppp.sum = (ppp.sum & 0xffff) + (ppp.sum>>16); // sum one more time to catch any carry from the carry
nixnax	159:4d1bf96a59cd	511	return ~ppp.sum;
nixnax	142:54d1543e23e5	512	}
nixnax	142:54d1543e23e5	513
nixnax	142:54d1543e23e5	514	/// perform the checksum on an IP header
nixnax	146:a45f49a2b29c	515	void IpHeaderCheckSum()
nixnax	142:54d1543e23e5	516	{
nixnax	161:d59f778bc8ab	517	ppp.ip->checksumR=0; // zero the checsum in the IP header
nixnax	161:d59f778bc8ab	518	int len = 4 * ppp.ip->headerLength; // length of IP header in bytes
nixnax	161:d59f778bc8ab	519	unsigned int sum = dataCheckSum(ppp.ipStart,len,1);
nixnax	161:d59f778bc8ab	520	ppp.ip->checksumR = __REV16( sum ); // insert fresh checksum
nixnax	146:a45f49a2b29c	521	}
nixnax	146:a45f49a2b29c	522
nixnax	147:0f40005cbc5f	523	/// swap the IP source and destination addresses
nixnax	147:0f40005cbc5f	524	void swapIpAddresses()
nixnax	147:0f40005cbc5f	525	{
nixnax	162:594729c0e5c1	526	unsigned int tempHold;
nixnax	162:594729c0e5c1	527	tempHold = ppp.ip->srcAdrR; // tempHold <- source IP
nixnax	162:594729c0e5c1	528	ppp.ip->srcAdrR = ppp.ip->dstAdrR; // source <- dest
nixnax	162:594729c0e5c1	529	ppp.ip->dstAdrR = tempHold; // dest <- tempHold*/
nixnax	147:0f40005cbc5f	530	}
nixnax	147:0f40005cbc5f	531
nixnax	149:969d98f6fb88	532	/// swap the IP source and destination ports
nixnax	149:969d98f6fb88	533	void swapIpPorts()
nixnax	149:969d98f6fb88	534	{
nixnax	149:969d98f6fb88	535	int headerSizeIP = 4*(ppp.pkt.buf[4]&0xf); // calculate size of IP header
nixnax	149:969d98f6fb88	536	char * ipSrcPort = 4 + ppp.pkt.buf + headerSizeIP + 0; // ip source port location
nixnax	149:969d98f6fb88	537	char * ipDstPort = 4 + ppp.pkt.buf + headerSizeIP + 2; // ip destin port location
nixnax	149:969d98f6fb88	538	char tempHold[2];
nixnax	149:969d98f6fb88	539	memcpy(tempHold, ipSrcPort,2); // tempHold <- source
nixnax	149:969d98f6fb88	540	memcpy(ipSrcPort,ipDstPort,2); // source <- dest
nixnax	149:969d98f6fb88	541	memcpy(ipDstPort,tempHold, 2); // dest <- tempHold
nixnax	149:969d98f6fb88	542	}
nixnax	149:969d98f6fb88	543
nixnax	146:a45f49a2b29c	544	/// Process an incoming UDP packet.
nixnax	146:a45f49a2b29c	545	/// If the packet starts with the string "echo " or "test" we echo back a special packet
nixnax	146:a45f49a2b29c	546	void UDPpacket()
nixnax	146:a45f49a2b29c	547	{
nixnax	163:d1b4328e9f08	548	struct {
nixnax	163:d1b4328e9f08	549	unsigned int all; // length of entire ip packet
nixnax	163:d1b4328e9f08	550	unsigned int header; // length of ip header
nixnax	163:d1b4328e9f08	551	} ipLength;
nixnax	163:d1b4328e9f08	552
nixnax	163:d1b4328e9f08	553	struct {
nixnax	163:d1b4328e9f08	554	unsigned int all; // lenght of entire udp packet
nixnax	163:d1b4328e9f08	555	unsigned int data; // length of udp data segment
nixnax	163:d1b4328e9f08	556	} udpLength;
nixnax	163:d1b4328e9f08	557
nixnax	163:d1b4328e9f08	558	ipLength.header = 4 * ppp.ip->headerLength; // length of ip header
nixnax	163:d1b4328e9f08	559	ppp.udpStart = ppp.ipStart + ipLength.header; // calculate start of udp header
nixnax	163:d1b4328e9f08	560	udpLength.all = __REV16( ppp.udp->lengthR ); //((udpLen[0]<<8) \| udpLen[1]); // size of udp packet
nixnax	163:d1b4328e9f08	561	udpLength.data = udpLength.all - 8; // size of udp data
nixnax	147:0f40005cbc5f	562
nixnax	146:a45f49a2b29c	563	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	163:d1b4328e9f08	564	char * srcIP = (char *)&ppp.ip->srcAdrR; //ipHeader+12; // IP source
nixnax	163:d1b4328e9f08	565	char * dstIP = (char *)&ppp.ip->dstAdrR; //ipHeader+16; // IP destination
nixnax	163:d1b4328e9f08	566
nixnax	163:d1b4328e9f08	567	unsigned int udpSrcPort = __REV16( ppp.udp->srcPortR ); //(udpSrcPort[0]<<8)\|udpSrcPort[1]; // integer of UDP source port
nixnax	163:d1b4328e9f08	568	unsigned int udpDstPort = __REV16( ppp.udp->dstPortR ); //(udpDstPort[0]<<8)\|udpDstPort[1]; // integer of UDP dest port
nixnax	163:d1b4328e9f08	569
nixnax	163:d1b4328e9f08	570	if(v0) {
nixnax	163:d1b4328e9f08	571	debugPrintf("UDP %d.%d.%d.%d:%d ", srcIP[0],srcIP[1],srcIP[2],srcIP[3],udpSrcPort);
nixnax	163:d1b4328e9f08	572	debugPrintf("%d.%d.%d.%d:%d ", dstIP[0],dstIP[1],dstIP[2],dstIP[3],udpDstPort);
nixnax	163:d1b4328e9f08	573	debugPrintf("Len %03d", udpLength);
nixnax	163:d1b4328e9f08	574	}
nixnax	146:a45f49a2b29c	575	if (v1) {
nixnax	163:d1b4328e9f08	576	int printSize = udpLength.data;
nixnax	146:a45f49a2b29c	577	if (printSize > 20) printSize = 20; // print only first 20 characters
nixnax	146:a45f49a2b29c	578	for (int i=0; i<printSize; i++) {
nixnax	163:d1b4328e9f08	579	char ch = ppp.udp->data[i];
nixnax	146:a45f49a2b29c	580	if (ch>31 && ch<127) {
nixnax	146:a45f49a2b29c	581	debugPrintf("%c", ch);
nixnax	146:a45f49a2b29c	582	} else {
nixnax	146:a45f49a2b29c	583	debugPrintf("_");
nixnax	146:a45f49a2b29c	584	}
nixnax	146:a45f49a2b29c	585	}
nixnax	146:a45f49a2b29c	586	}
nixnax	146:a45f49a2b29c	587	if (v0) debugPrintf("\n");
nixnax	146:a45f49a2b29c	588	#endif
nixnax	163:d1b4328e9f08	589	int echoFound = !strncmp(ppp.udp->data,"echo ",5); // true if UDP message starts with "echo "
nixnax	163:d1b4328e9f08	590	int testFound = !strncmp(ppp.udp->data,"test" ,4); // true if UDP message starts with "test"
nixnax	146:a45f49a2b29c	591	if ( (echoFound) \|\| (testFound)) { // if the UDP message starts with "echo " or "test" we answer back
nixnax	147:0f40005cbc5f	592	swapIpAddresses(); // swap IP source and destination
nixnax	149:969d98f6fb88	593	swapIpPorts(); // swap IP source and destination ports
nixnax	146:a45f49a2b29c	594	if (echoFound) {
nixnax	163:d1b4328e9f08	595	memcpy(ppp.udp->data,"Got{",4); // in the UDP data modify "echo" to "Got:"
nixnax	146:a45f49a2b29c	596	char endString[] = "} UDP Server: PPP-Blinky\n"; // an appendix
nixnax	163:d1b4328e9f08	597	memcpy(ppp.udp->data+udpLength.data,endString,sizeof(endString)-1); // add endstring size to the UDP message
nixnax	163:d1b4328e9f08	598	udpLength.all = udpLength.data + sizeof(endString)-1; // update udp data size with the size of the appendix
nixnax	146:a45f49a2b29c	599	}
nixnax	146:a45f49a2b29c	600	if (testFound) {
nixnax	146:a45f49a2b29c	601	char udpResponse[50];
nixnax	146:a45f49a2b29c	602	int n = 0;
nixnax	146:a45f49a2b29c	603	n = n+sprintf(udpResponse+n,"Response count %d\n",ppp.responseCounter++);
nixnax	163:d1b4328e9f08	604	memcpy(ppp.udp->data,udpResponse,n); // copy response to the UDP data area
nixnax	163:d1b4328e9f08	605	udpLength.data = n; // update udp data size
nixnax	146:a45f49a2b29c	606	}
nixnax	163:d1b4328e9f08	607	// we may have changed data length, update all the lengths
nixnax	163:d1b4328e9f08	608	udpLength.all = udpLength.data+8; // update local udp packet length
nixnax	163:d1b4328e9f08	609	ipLength.all = ipLength.header + udpLength.all; // update IP Length
nixnax	163:d1b4328e9f08	610	ppp.ip->lengthR = __REV16(ipLength.all); // update IP length in buffer
nixnax	163:d1b4328e9f08	611	ppp.udp->lengthR = __REV16(udpLength.all); // update UDP length in buffer
nixnax	163:d1b4328e9f08	612	ppp.pkt.len = ipLength.all+2+4; // update ppp packet length
nixnax	163:d1b4328e9f08	613
nixnax	163:d1b4328e9f08	614	IpHeaderCheckSum(); // refresh IP header checksum
nixnax	163:d1b4328e9f08	615	ppp.udp->checkSumR = 0; // we don't yet recompute the UDP checksum (it's optional), so have to zero it
nixnax	146:a45f49a2b29c	616	sendPppFrame(); // send the UDP message back
nixnax	146:a45f49a2b29c	617	}
nixnax	142:54d1543e23e5	618	}
nixnax	142:54d1543e23e5	619
nixnax	142:54d1543e23e5	620	/// handle a PING ICMP (internet control message protocol) packet
nixnax	142:54d1543e23e5	621	void ICMPpacket() // internet control message protocol
nixnax	142:54d1543e23e5	622	{
nixnax	142:54d1543e23e5	623	char * ipPkt = ppp.pkt.buf+4; // ip packet start
nixnax	142:54d1543e23e5	624	char * pktLen = ipPkt+2;
nixnax	142:54d1543e23e5	625	int packetLength = (pktLen[0]<<8) \| pktLen[1]; // icmp packet length
nixnax	142:54d1543e23e5	626	int headerSizeIP = (( ipPkt[0]&0xf)*4);
nixnax	142:54d1543e23e5	627	char * icmpType = ipPkt + headerSizeIP; // icmp data start
nixnax	142:54d1543e23e5	628	char * icmpSum = icmpType+2; // icmp checksum
nixnax	142:54d1543e23e5	629	#define ICMP_TYPE_PING_REQUEST 8
nixnax	142:54d1543e23e5	630	if ( icmpType[0] == ICMP_TYPE_PING_REQUEST ) {
nixnax	142:54d1543e23e5	631	char * ipTTL = ipPkt+8; // time to live
nixnax	147:0f40005cbc5f	632	ipTTL[0]--; // decrement time to live (so we have to update header checksum)
nixnax	147:0f40005cbc5f	633	#ifdef SERIAL_PORT_MONITOR_YES
nixnax	142:54d1543e23e5	634	char * srcAdr = ipPkt+12;
nixnax	142:54d1543e23e5	635	char * dstAdr = ipPkt+16;
nixnax	142:54d1543e23e5	636	int icmpIdent = (icmpType[4]<<8)\|icmpType[5];
nixnax	142:54d1543e23e5	637	int icmpSequence = (icmpType[6]<<8)\|icmpType[7];
nixnax	142:54d1543e23e5	638	if(1) {
nixnax	142:54d1543e23e5	639	char pbuf[50];
nixnax	142:54d1543e23e5	640	checkPc();
nixnax	142:54d1543e23e5	641	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	642	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	643	checkPc();
nixnax	142:54d1543e23e5	644	sprintf(pbuf, "Ident %04x Sequence %04d \n",icmpIdent,icmpSequence);
nixnax	142:54d1543e23e5	645	checkPc();
nixnax	142:54d1543e23e5	646	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	647	}
nixnax	142:54d1543e23e5	648	#endif
nixnax	147:0f40005cbc5f	649	swapIpAddresses(); // swap the IP source and destination addresses
nixnax	147:0f40005cbc5f	650	IpHeaderCheckSum(); // new ip header checksum (required because we changed TTL)
nixnax	142:54d1543e23e5	651	#define ICMP_TYPE_ECHO_REPLY 0
nixnax	142:54d1543e23e5	652	icmpType[0]=ICMP_TYPE_ECHO_REPLY; // icmp echo reply
nixnax	142:54d1543e23e5	653	icmpSum[0]=0;
nixnax	142:54d1543e23e5	654	icmpSum[1]=0; // zero the checksum for recalculation
nixnax	142:54d1543e23e5	655	int icmpLength = packetLength - headerSizeIP; // length of ICMP data portion
nixnax	161:d59f778bc8ab	656	unsigned int sum = dataCheckSum(icmpType, icmpLength, 1); // this checksum on icmp data portion
nixnax	142:54d1543e23e5	657	icmpSum[0]=(sum>>8)&0xff;
nixnax	142:54d1543e23e5	658	icmpSum[1]=(sum )&0xff; // new checksum for ICMP data portion
nixnax	142:54d1543e23e5	659
nixnax	142:54d1543e23e5	660	int printSize = icmpLength-8; // exclude size of icmp header
nixnax	142:54d1543e23e5	661	char * icmpData = icmpType+8; // the actual payload data is after the header
nixnax	142:54d1543e23e5	662	if (printSize > 10) printSize = 10; // print up to 20 characters
nixnax	142:54d1543e23e5	663	if (0) {
nixnax	142:54d1543e23e5	664	for (int i=0; i<printSize; i++) {
nixnax	142:54d1543e23e5	665	char ch = icmpData[i];
nixnax	142:54d1543e23e5	666	if (ch>31 && ch<127) {
nixnax	142:54d1543e23e5	667	putcWhileCheckingInput(ch);
nixnax	142:54d1543e23e5	668	} else {
nixnax	142:54d1543e23e5	669	putcWhileCheckingInput('_');
nixnax	142:54d1543e23e5	670	}
nixnax	142:54d1543e23e5	671	}
nixnax	142:54d1543e23e5	672	putcWhileCheckingInput('\n');
nixnax	142:54d1543e23e5	673	}
nixnax	144:01d98cf7738e	674	sendPppFrame(); // reply to the ping
nixnax	142:54d1543e23e5	675	} else {
nixnax	142:54d1543e23e5	676	if (v0) {
nixnax	142:54d1543e23e5	677	debugPrintf("ICMP type=%d \n", icmpType[0]);
nixnax	142:54d1543e23e5	678	}
nixnax	142:54d1543e23e5	679	}
nixnax	142:54d1543e23e5	680	}
nixnax	142:54d1543e23e5	681
nixnax	142:54d1543e23e5	682	/// handle an IGMP (internet group managment protocol) packet (by ignoring it)
nixnax	142:54d1543e23e5	683	void IGMPpacket()
nixnax	142:54d1543e23e5	684	{
nixnax	142:54d1543e23e5	685	if (v0) debugPrintf("IGMP type=%d \n", ppp.pkt.buf[28]);
nixnax	142:54d1543e23e5	686	}
nixnax	142:54d1543e23e5	687
nixnax	142:54d1543e23e5	688	/// dump the header of an IP pakcet on the (optional) debug serial port
nixnax	142:54d1543e23e5	689	void dumpHeaderIP (int outGoing)
nixnax	142:54d1543e23e5	690	{
nixnax	142:54d1543e23e5	691	#if defined(IP_HEADER_DUMP_YES) && defined(SERIAL_PORT_MONITOR_YES)
nixnax	142:54d1543e23e5	692	checkPc(); // we are expecting the first character of the next packet
nixnax	155:9c6a1d249e26	693	int IPv4Id = __REV16(ppp.ip->identR);
nixnax	152:025c73b6c0a9	694	char pbuf[80]; // local print buffer
nixnax	142:54d1543e23e5	695	int n=0;
nixnax	142:54d1543e23e5	696	n=n+sprintf(pbuf+n, outGoing ? "\x1b[34m" : "\x1b[30m" ); // VT100 color code, print black for incoming, blue for outgoing headers
nixnax	142:54d1543e23e5	697	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	698	#define DUMP_FULL_IP_ADDRESS_YES
nixnax	142:54d1543e23e5	699	#ifdef DUMP_FULL_IP_ADDRESS_YES
nixnax	163:d1b4328e9f08	700	char * srcAdr = (char *)&ppp.ip->srcAdrR;
nixnax	163:d1b4328e9f08	701	char * dstAdr = (char *)&ppp.ip->dstAdrR;
nixnax	142:54d1543e23e5	702	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	703	#endif
nixnax	142:54d1543e23e5	704	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	705	#ifndef TCP_HEADER_DUMP_YES
nixnax	160:bd701ad564cb	706	putsWhileCheckingInput('\x1b[30m\n'); // if there's no TCP header dump we terminate the line with \n and VT100 code for black
nixnax	142:54d1543e23e5	707	#endif
nixnax	142:54d1543e23e5	708	#endif
nixnax	142:54d1543e23e5	709	}
nixnax	142:54d1543e23e5	710
nixnax	142:54d1543e23e5	711	/// dump a TCP header on the optional debug serial port
nixnax	142:54d1543e23e5	712	void dumpHeaderTCP(int outGoing)
nixnax	142:54d1543e23e5	713	{
nixnax	142:54d1543e23e5	714	#if defined(TCP_HEADER_DUMP_YES) && defined(SERIAL_PORT_MONITOR_YES)
nixnax	155:9c6a1d249e26	715	char flagString[9]; // text string presenting the 8 most important TCP flags
nixnax	142:54d1543e23e5	716	#define PRINT_ALL_TCP_FLAGS_YES
nixnax	142:54d1543e23e5	717	#ifdef PRINT_ALL_TCP_FLAGS_YES
nixnax	155:9c6a1d249e26	718	memset(flagString,'.', 8); // fill string with "........"
nixnax	156:163c23249731	719	if (ppp.tcp->flag.fin) flagString[7]='F';
nixnax	156:163c23249731	720	if (ppp.tcp->flag.syn) flagString[6]='S';
nixnax	156:163c23249731	721	if (ppp.tcp->flag.rst) flagString[5]='R';
nixnax	156:163c23249731	722	if (ppp.tcp->flag.psh) flagString[4]='P';
nixnax	156:163c23249731	723	if (ppp.tcp->flag.ack) flagString[3]='A';
nixnax	156:163c23249731	724	if (ppp.tcp->flag.urg) flagString[2]='U';
nixnax	156:163c23249731	725	if (ppp.tcp->flag.ece) flagString[1]='E';
nixnax	156:163c23249731	726	if (ppp.tcp->flag.cwr) flagString[0]='C';
nixnax	155:9c6a1d249e26	727	flagString[8]=0; // null terminate string
nixnax	142:54d1543e23e5	728	#else
nixnax	156:163c23249731	729	if (ppp.tcp->flag.ack) flagString[0]='A'; // choose only the most important flag to print
nixnax	156:163c23249731	730	if (ppp.tcp->flag.syn) flagString[0]='S';
nixnax	156:163c23249731	731	if (ppp.tcp->flag.fin) flagString[0]='F';
nixnax	156:163c23249731	732	if (ppp.tcp->flag.psh) flagString[0]='P';
nixnax	156:163c23249731	733	if (ppp.tcp->flag.rst) flagString[0]='R';
nixnax	155:9c6a1d249e26	734	flagString[1]=0; // null terminate string
nixnax	142:54d1543e23e5	735	#endif
nixnax	155:9c6a1d249e26	736	putsWhileCheckingInput( flagString );
nixnax	142:54d1543e23e5	737	#define EVERY_PACKET_ON_A_NEW_LINE_YES
nixnax	142:54d1543e23e5	738	#ifdef EVERY_PACKET_ON_A_NEW_LINE_YES
nixnax	142:54d1543e23e5	739	putsWhileCheckingInput("\x1b[30m\n"); // write a black color and newline after every packet
nixnax	160:bd701ad564cb	740	#else
nixnax	160:bd701ad564cb	741	putsWhileCheckingInput("\x1b[30m"); // write a black color after every packet
nixnax	142:54d1543e23e5	742	#endif
nixnax	156:163c23249731	743	if( outGoing && ppp.tcp->flag.fin ) { // ACK/FIN - if this is an outgoing FIN it's the end of a tcp conversation
nixnax	160:bd701ad564cb	744	putcWhileCheckingInput('\n'); // insert an extra new line to mark the end (except for final ack) of an HTTP conversation
nixnax	142:54d1543e23e5	745	}
nixnax	142:54d1543e23e5	746	#endif
nixnax	142:54d1543e23e5	747	}
nixnax	142:54d1543e23e5	748
nixnax	143:c5019f856a56	749	/// Encode a buffer in base-64
nixnax	142:54d1543e23e5	750	void enc64(char * in, char * out, int len)
nixnax	142:54d1543e23e5	751	{
nixnax	142:54d1543e23e5	752	const static char lut [] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
nixnax	142:54d1543e23e5	753	int i,j,a,b,c;
nixnax	142:54d1543e23e5	754	i=0;
nixnax	142:54d1543e23e5	755	j=0;
nixnax	142:54d1543e23e5	756	while(1) {
nixnax	142:54d1543e23e5	757	if (i<len) {
nixnax	142:54d1543e23e5	758	a = in[i++];
nixnax	142:54d1543e23e5	759	out[j++] = lut[ ( (a >> 2) & 0x3f) ];
nixnax	142:54d1543e23e5	760	} else break;
nixnax	142:54d1543e23e5	761	if (i<len) {
nixnax	142:54d1543e23e5	762	b = in[i++];
nixnax	142:54d1543e23e5	763	out[j++] = lut[ ( (a << 4) & 0x30) \| ( (b >> 4) & 0x0f) ];
nixnax	142:54d1543e23e5	764	out[j++] = lut[ ( (b << 2) & 0x3c) ];
nixnax	142:54d1543e23e5	765	} else out[j++] = '=';
nixnax	142:54d1543e23e5	766	if (i<len) {
nixnax	142:54d1543e23e5	767	c = in[i++];
nixnax	142:54d1543e23e5	768	j--;
nixnax	142:54d1543e23e5	769	out[j++] = lut[ ( (b << 2) & 0x3c) \| ( (c >> 6) & 0x03) ];
nixnax	142:54d1543e23e5	770	out[j++] = lut[ ( (c >> 0) & 0x3f) ];
nixnax	142:54d1543e23e5	771	} else out[j++] = '=';
nixnax	142:54d1543e23e5	772	}
nixnax	142:54d1543e23e5	773	out[j]=0;
nixnax	142:54d1543e23e5	774	}
nixnax	142:54d1543e23e5	775
nixnax	160:bd701ad564cb	776	/// Handle a request for an http websocket.
nixnax	160:bd701ad564cb	777	/// 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	778	int webSocketHandler(char * dataStart)
nixnax	142:54d1543e23e5	779	{
nixnax	142:54d1543e23e5	780	int n=0; // byte counter
nixnax	142:54d1543e23e5	781	char * key = strstr(dataStart, "Sec-WebSocket-Key: "); // search for the key in the payload
nixnax	142:54d1543e23e5	782	if (key != NULL) {
nixnax	142:54d1543e23e5	783	if (v0) putsWhileCheckingInput("WebSocket Request\n");
nixnax	142:54d1543e23e5	784	char challenge [70];
nixnax	142:54d1543e23e5	785	strncpy(challenge,key+19,70); // a local buffer
nixnax	142:54d1543e23e5	786	*strchr(challenge,'\r')=0; // insert null so we can use sprintf
nixnax	142:54d1543e23e5	787	strncat(challenge,"258EAFA5-E914-47DA-95CA-C5AB0DC85B11",70); // append websocket gui code
nixnax	142:54d1543e23e5	788	char shaOutput [20]; // sha1 output
nixnax	142:54d1543e23e5	789	sha1( shaOutput, challenge, strlen(challenge));
nixnax	142:54d1543e23e5	790	char encOut[50];
nixnax	142:54d1543e23e5	791	enc64( shaOutput, encOut, 20);
nixnax	142:54d1543e23e5	792	char * versionstring = strstr(dataStart, "Sec-WebSocket-Version:");
nixnax	142:54d1543e23e5	793	char * version = challenge;
nixnax	142:54d1543e23e5	794	strncpy(version, versionstring,70); // copy version string
nixnax	142:54d1543e23e5	795	*strchr(version,'\r')=0; // null terminate so we can sprintf it
nixnax	142:54d1543e23e5	796	memset(dataStart,0,500); // blank out old data befor send the websocket response header
nixnax	142:54d1543e23e5	797	n=n+sprintf(dataStart+n, "HTTP/1.1 101 Switching Protocols\r\n");
nixnax	142:54d1543e23e5	798	n=n+sprintf(dataStart+n, "Upgrade: websocket\r\n");
nixnax	142:54d1543e23e5	799	n=n+sprintf(dataStart+n, "Connection: Upgrade\r\n");
nixnax	142:54d1543e23e5	800	n=n+sprintf(dataStart+n, "Sec-WebSocket-Accept: %s\r\n",encOut);
nixnax	142:54d1543e23e5	801	n=n+sprintf(dataStart+n, "%s\r\n",version);
nixnax	142:54d1543e23e5	802	n=n+sprintf(dataStart+n, "mbed-Code: PPP-Blinky\r\n");
nixnax	142:54d1543e23e5	803	n=n+sprintf(dataStart+n, "\r\n"); // websocket response header ending
nixnax	142:54d1543e23e5	804	}
nixnax	142:54d1543e23e5	805	return n; // this response should satisfy a web browser's websocket protocol request
nixnax	142:54d1543e23e5	806	}
nixnax	142:54d1543e23e5	807
nixnax	142:54d1543e23e5	808	#define TCP_FLAG_ACK (1<<4)
nixnax	142:54d1543e23e5	809	#define TCP_FLAG_SYN (1<<1)
nixnax	142:54d1543e23e5	810	#define TCP_FLAG_PSH (1<<3)
nixnax	142:54d1543e23e5	811	#define TCP_FLAG_RST (1<<2)
nixnax	142:54d1543e23e5	812	#define TCP_FLAG_FIN (1<<0)
nixnax	142:54d1543e23e5	813
nixnax	142:54d1543e23e5	814	/// respond to an HTTP request
nixnax	142:54d1543e23e5	815	int httpResponse(char * dataStart)
nixnax	142:54d1543e23e5	816	{
nixnax	142:54d1543e23e5	817	int n=0; // number of bytes we have printed so far
nixnax	142:54d1543e23e5	818	n = webSocketHandler( dataStart ); // test for and handle WebSocket upgrade requests
nixnax	160:bd701ad564cb	819	if (n>0) return n; // if n>0 we already have a response, so return
nixnax	142:54d1543e23e5	820
nixnax	142:54d1543e23e5	821	int nHeader; // byte size of HTTP header
nixnax	142:54d1543e23e5	822	int contentLengthStart; // index where HTML starts
nixnax	142:54d1543e23e5	823	int httpGet5,httpGet6,httpGetx, httpGetRoot; // temporary storage of strncmp results
nixnax	142:54d1543e23e5	824
nixnax	146:a45f49a2b29c	825	ppp.responseCounter++; // increment the number of frames we have made
nixnax	142:54d1543e23e5	826
nixnax	142:54d1543e23e5	827	httpGetRoot = strncmp(dataStart, "GET / HTTP/1.", 13); // found a GET to the root directory
nixnax	142:54d1543e23e5	828	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	829	httpGet5 = dataStart[5]; // the first character in the path name, we use it for special functions later on
nixnax	142:54d1543e23e5	830	httpGet6 = dataStart[6]; // the second character in the path name, we use it for special functions later on
nixnax	142:54d1543e23e5	831	// for example, you could try this using netcat (nc): echo "GET /x" \| nc 172.10.10.2
nixnax	142:54d1543e23e5	832	if( (httpGetRoot==0) \|\| (httpGetx==0) ) {
nixnax	142:54d1543e23e5	833	n=n+sprintf(n+dataStart,"HTTP/1.1 200 OK\r\nServer: mbed-PPP-Blinky-v1\r\n"); // 200 OK header
nixnax	142:54d1543e23e5	834	} else {
nixnax	142:54d1543e23e5	835	n=n+sprintf(n+dataStart,"HTTP/1.1 404 Not Found\r\nServer: mbed-PPP-Blinky\r\n"); // 404 header
nixnax	142:54d1543e23e5	836	}
nixnax	142:54d1543e23e5	837	n=n+sprintf(n+dataStart,"Content-Length: "); // http header
nixnax	142:54d1543e23e5	838	contentLengthStart = n; // remember where Content-Length is in buffer
nixnax	142:54d1543e23e5	839	n=n+sprintf(n+dataStart,"?????\r\n"); // leave five spaces for content length - will be updated later
nixnax	142:54d1543e23e5	840	n=n+sprintf(n+dataStart,"Connection: close\r\n"); // close connection immediately
nixnax	142:54d1543e23e5	841	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	842	nHeader=n; // size of HTTP header
nixnax	142:54d1543e23e5	843	if( httpGetRoot == 0 ) {
nixnax	142:54d1543e23e5	844	// this is where we insert our web page into the buffer
nixnax	142:54d1543e23e5	845	memcpy(n+dataStart,rootWebPage,sizeof(rootWebPage));
nixnax	142:54d1543e23e5	846	n = n + sizeof(rootWebPage)-1; // one less than sizeof because we don't count the null byte at the end
nixnax	142:54d1543e23e5	847	} else if ( (httpGet5 == 'w') && (httpGet6 == 's') ) { // "ws" is a special page for websocket demo
nixnax	142:54d1543e23e5	848	memcpy(n+dataStart,webSocketPage,sizeof(webSocketPage));
nixnax	142:54d1543e23e5	849	n = n + sizeof(webSocketPage)-1; // one less than size
nixnax	142:54d1543e23e5	850	} else {
nixnax	142:54d1543e23e5	851	if (httpGetx == 0) { // the page request started with "GET /x" - here we treat anything starting with /x special:
nixnax	142:54d1543e23e5	852
nixnax	142:54d1543e23e5	853	#define W3C_COMPLIANT_RESPONSE_NO
nixnax	142:54d1543e23e5	854	// change the above to W3C_COMPLIANT_RESPONSE_YES if you want a W3C.org compliant HTTP response
nixnax	142:54d1543e23e5	855	#ifdef W3C_COMPLIANT_RESPONSE_YES
nixnax	142:54d1543e23e5	856	n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (W3C.org required elements)
nixnax	146:a45f49a2b29c	857	n=n+sprintf(n+dataStart,"<body>%d</body>",ppp.responseCounter); // body = the http frame count
nixnax	142:54d1543e23e5	858	#else
nixnax	142:54d1543e23e5	859	if( httpGet6 == 'b' ) { // if the fetched page is "xb" send a meta command to let the browser continuously reload
nixnax	142:54d1543e23e5	860	n=n+sprintf(n+dataStart, "<meta http-equiv=\"refresh\" content=\"0\">"); // reload loop - handy for benchmarking
nixnax	142:54d1543e23e5	861	}
nixnax	142:54d1543e23e5	862	// /x is a very short page, in fact, it is only a decimal number showing the http Page count
nixnax	146:a45f49a2b29c	863	n=n+sprintf(n+dataStart,"%d ",ppp.responseCounter); // not really valid html but most browsers and curl are ok with it
nixnax	142:54d1543e23e5	864	#endif
nixnax	142:54d1543e23e5	865	} else {
nixnax	142:54d1543e23e5	866	// all other requests get 404 Not Found response with a http frame count - nice for debugging
nixnax	142:54d1543e23e5	867	n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (required element)
nixnax	142:54d1543e23e5	868	n=n+sprintf(n+dataStart,"<body>Not Found</body>"); // not found message
nixnax	142:54d1543e23e5	869	}
nixnax	142:54d1543e23e5	870	}
nixnax	142:54d1543e23e5	871	#define CONTENTLENGTHSIZE 5
nixnax	142:54d1543e23e5	872	char contentLengthString[CONTENTLENGTHSIZE+1];
nixnax	142:54d1543e23e5	873	snprintf(contentLengthString,CONTENTLENGTHSIZE+1,"%*d",CONTENTLENGTHSIZE,n-nHeader); // print Content-Length with leading spaces and fixed width equal to csize
nixnax	142:54d1543e23e5	874	memcpy(dataStart+contentLengthStart, contentLengthString, CONTENTLENGTHSIZE); // copy Content-Length to it's place in the send buffer
nixnax	142:54d1543e23e5	875	return n; // total byte size of our response
nixnax	142:54d1543e23e5	876	}
nixnax	142:54d1543e23e5	877
nixnax	160:bd701ad564cb	878	/// Handle TCP data that is not an HTTP GET.
nixnax	160:bd701ad564cb	879	/// This is handy when for example you want to use netcat (nc.exe) to talk to PPP-Blinky.
nixnax	160:bd701ad564cb	880	/// This could also be a websocket receive event - especially if the first byte is 0x81 (websocket data push)
nixnax	142:54d1543e23e5	881	int tcpResponse(char * dataStart, int len, int * outFlags)
nixnax	142:54d1543e23e5	882	{
nixnax	142:54d1543e23e5	883	int n=0; // number of bytes we have printed so far
nixnax	142:54d1543e23e5	884	if (dataStart[0] == 0x81) { // check if this is a websocket push message
nixnax	160:bd701ad564cb	885	char mask [4];
nixnax	160:bd701ad564cb	886	memcpy ( mask, dataStart+2, 4); // websocket messages are "masked", so first we obtain the 4-byte mask
nixnax	160:bd701ad564cb	887	int websocketMessageSize = len - 6; // 1 byte prefix (0x81), 1 byte, 4 bytes mask = 6 bytes
nixnax	160:bd701ad564cb	888	if((dataStart[1]&0x80)==0x80) // test if the mask bit is set, which means all data is xor'ed with the mask
nixnax	160:bd701ad564cb	889	for (int i=0; i<websocketMessageSize; i++) dataStart[i+6]^= mask[i%4]; // unmask each byte with one of the mask bytes
nixnax	160:bd701ad564cb	890	dataStart[1] = len-2; // add four extra bytes to the message length because we don't use mask bytes for the send
nixnax	160:bd701ad564cb	891	memcpy(dataStart+2, "Got:",4); // insert our own text into the four mask bytes
nixnax	160:bd701ad564cb	892	n = len; // our response size remains exactly the same length as what we received
nixnax	142:54d1543e23e5	893	} else if ( (dataStart[0]==0x88) && (dataStart[1]==0x80) && (len == 6) ) { // test for a websocket close request
nixnax	142:54d1543e23e5	894	n=2; // our close command is only two bytes long because we don't use the four mask bytes
nixnax	142:54d1543e23e5	895	dataStart[1]=0; // we don't have mask bytes on
nixnax	160:bd701ad564cb	896	} else {
nixnax	160:bd701ad564cb	897	if (v1) putsWhileCheckingInput("TCP data received\n"); // all other tcp push packets
nixnax	163:d1b4328e9f08	898	}
nixnax	142:54d1543e23e5	899	return n; // total byte size of our response
nixnax	142:54d1543e23e5	900	}
nixnax	142:54d1543e23e5	901
nixnax	142:54d1543e23e5	902	/// handle an incoming TCP packet
nixnax	142:54d1543e23e5	903	/// 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	904	void tcpHandler()
nixnax	142:54d1543e23e5	905	{
nixnax	142:54d1543e23e5	906	// IP header
nixnax	154:18b2bd92f557	907	int packetLengthIp = __REV16(ppp.ip->lengthR ); // size of ip packet
nixnax	154:18b2bd92f557	908	int headerSizeIp = 4 * ppp.ip->headerLength; // size of ip header
nixnax	142:54d1543e23e5	909
nixnax	142:54d1543e23e5	910	// TCP header
nixnax	160:bd701ad564cb	911
nixnax	155:9c6a1d249e26	912	ppp.tcpStart = ppp.ipStart + headerSizeIp; // calculate where the TCP header starts
nixnax	154:18b2bd92f557	913	int tcpSize = packetLengthIp - headerSizeIp; // tcp size = size of ip payload
nixnax	160:bd701ad564cb	914	char * tcp = ppp.ipStart+headerSizeIp; // calculate start of tcp packet
nixnax	142:54d1543e23e5	915
nixnax	154:18b2bd92f557	916	int headerSizeTcp = 4 * (ppp.tcp->offset); // tcp "offset" for start of data is also the header size
nixnax	152:025c73b6c0a9	917
nixnax	154:18b2bd92f557	918	char * tcpDataIn = tcp + headerSizeTcp; // start of data block after TCP header
nixnax	154:18b2bd92f557	919	int tcpDataSize = tcpSize - headerSizeTcp; // size of data block after TCP header
nixnax	154:18b2bd92f557	920
nixnax	154:18b2bd92f557	921	unsigned int seq_in = __REV(ppp.tcp->seqTcpR);
nixnax	154:18b2bd92f557	922	unsigned int ack_in = __REV(ppp.tcp->ackTcpR);
nixnax	142:54d1543e23e5	923	unsigned int ack_out = seq_in + tcpDataSize;
nixnax	142:54d1543e23e5	924	unsigned int seq_out = ack_in; // use their version of our current sequence number
nixnax	142:54d1543e23e5	925
nixnax	142:54d1543e23e5	926	// first we shorten the TCP response header to only 20 bytes. This means we ignore all TCP option requests
nixnax	142:54d1543e23e5	927	tcpSize = 20; // shorten total TCP packet size to 20 bytes (no data)
nixnax	154:18b2bd92f557	928	headerSizeTcp = 20; // shorten outgoing TCP header size 20 bytes
nixnax	154:18b2bd92f557	929	ppp.ip->headerLength = 5; // ip header is 20 bytes long
nixnax	154:18b2bd92f557	930	ppp.tcp->offset = (headerSizeTcp/4);
nixnax	154:18b2bd92f557	931	ppp.ip->lengthR = __REV(40);
nixnax	154:18b2bd92f557	932	char * tcpDataOut = tcp + 20; // start of outgoing data
nixnax	154:18b2bd92f557	933
nixnax	154:18b2bd92f557	934	ppp.ip->lengthR = __REV16(40);
nixnax	142:54d1543e23e5	935
nixnax	142:54d1543e23e5	936	int dataLen = 0; // most of our responses will have zero TCP data, only a header
nixnax	142:54d1543e23e5	937	int flagsOut = TCP_FLAG_ACK; // the default case is an ACK packet
nixnax	155:9c6a1d249e26	938	//int flagsTCP = ((flagbitstcp[0]&1)<<8)\|flagbitstcp[1]; // the tcp flags we received
nixnax	160:bd701ad564cb	939
nixnax	159:4d1bf96a59cd	940	ppp.tcp->windowR = __REV16( 700 ); // set tcp window size to 700 bytes
nixnax	142:54d1543e23e5	941
nixnax	142:54d1543e23e5	942	// A sparse TCP flag interpreter that implements stateless TCP connections
nixnax	142:54d1543e23e5	943
nixnax	156:163c23249731	944	switch ( ppp.tcp->flag.All ) {
nixnax	158:841592aed956	945	case TCP_FLAG_ACK: // handle ack messages by ignoring them
nixnax	142:54d1543e23e5	946	return;
nixnax	142:54d1543e23e5	947	case TCP_FLAG_SYN:
nixnax	142:54d1543e23e5	948	flagsOut = TCP_FLAG_SYN \| TCP_FLAG_ACK; // something wants to connect - acknowledge it
nixnax	142:54d1543e23e5	949	seq_out = seq_in+0x10000000U; // create a new sequence number using their sequence as a starting point, increase the highest digit
nixnax	142:54d1543e23e5	950	ack_out++; // for SYN flag we have to increase the sequence by 1
nixnax	142:54d1543e23e5	951	break;
nixnax	142:54d1543e23e5	952	case TCP_FLAG_ACK \| TCP_FLAG_PSH:
nixnax	142:54d1543e23e5	953	if ( (strncmp(tcpDataIn, "GET /", 5) == 0) ) { // check for an http GET command
nixnax	142:54d1543e23e5	954	flagsOut = TCP_FLAG_ACK \| TCP_FLAG_PSH; // set outgoing FIN flag to ask them to close from their side
nixnax	142:54d1543e23e5	955	dataLen = httpResponse(tcpDataOut); // send an http response
nixnax	142:54d1543e23e5	956	} else {
nixnax	158:841592aed956	957	dataLen = tcpResponse(tcpDataOut,tcpDataSize, &flagsOut); // not an http GET, handle as a tcp connection
nixnax	142:54d1543e23e5	958	}
nixnax	142:54d1543e23e5	959	break;
nixnax	142:54d1543e23e5	960	case TCP_FLAG_FIN:
nixnax	142:54d1543e23e5	961	case TCP_FLAG_FIN \| TCP_FLAG_ACK:
nixnax	142:54d1543e23e5	962	case TCP_FLAG_FIN \| TCP_FLAG_PSH \| TCP_FLAG_ACK:
nixnax	142:54d1543e23e5	963	flagsOut = TCP_FLAG_ACK \| TCP_FLAG_FIN; // set outgoing FIN flag to ask them to close from their side
nixnax	142:54d1543e23e5	964	ack_out++; // for FIN flag we have to increase the sequence by 1
nixnax	142:54d1543e23e5	965	break;
nixnax	142:54d1543e23e5	966	default:
nixnax	142:54d1543e23e5	967	return; // ignore remaining packets
nixnax	142:54d1543e23e5	968	} // switch
nixnax	142:54d1543e23e5	969
nixnax	142:54d1543e23e5	970	// The TCP flag handling is now done
nixnax	142:54d1543e23e5	971	// first we swap source and destination TCP addresses and insert the new ack and seq numbers
nixnax	147:0f40005cbc5f	972	swapIpAddresses(); // swap IP source and destination addresses
nixnax	149:969d98f6fb88	973	swapIpPorts(); // swap IP source and destination ports
nixnax	142:54d1543e23e5	974
nixnax	158:841592aed956	975	ppp.tcp->ackTcpR = __REV( ack_out ); // byte reversed - tcp/ip messages are big-endian (high byte first)
nixnax	158:841592aed956	976	ppp.tcp->seqTcpR = __REV( seq_out ); // byte reversed - tcp/ip messages are big-endian (high byte first)
nixnax	160:bd701ad564cb	977
nixnax	156:163c23249731	978	ppp.tcp->flag.All = flagsOut; // update the TCP flags
nixnax	142:54d1543e23e5	979
nixnax	159:4d1bf96a59cd	980	// recalculate all the header sizes
nixnax	154:18b2bd92f557	981	tcpSize = headerSizeTcp + dataLen; // tcp packet size
nixnax	154:18b2bd92f557	982	int newPacketSize = headerSizeIp + tcpSize; // calculate size of the outgoing packet
nixnax	159:4d1bf96a59cd	983	ppp.ip->lengthR = __REV16 ( newPacketSize );
nixnax	142:54d1543e23e5	984	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	985
nixnax	142:54d1543e23e5	986	// the header is all set up, now do the IP and TCP checksums
nixnax	146:a45f49a2b29c	987	IpHeaderCheckSum(); // calculate new IP header checksum
nixnax	142:54d1543e23e5	988
nixnax	159:4d1bf96a59cd	989	// create the TCP "pseudo-header" (containing some IP header values) in order to correctly calculate the TCP checksum
nixnax	142:54d1543e23e5	990	// this header contains the most important parts of the IP header, i.e. source and destination address, protocol number and data length.
nixnax	159:4d1bf96a59cd	991	pseudoIpHeaderType pseudoHeader; // create pseudo header
nixnax	159:4d1bf96a59cd	992	pseudoHeader.srcAdrR = ppp.ip->srcAdrR; // copy in ip source address
nixnax	159:4d1bf96a59cd	993	pseudoHeader.dstAdrR = ppp.ip->dstAdrR; // copy in ip dest address
nixnax	159:4d1bf96a59cd	994	pseudoHeader.zero = 0; // padding
nixnax	160:bd701ad564cb	995	pseudoHeader.protocol = ppp.ip->protocol; // protocol number
nixnax	159:4d1bf96a59cd	996	pseudoHeader.lengthR = __REV16( tcpSize ); // size of tcp packet
nixnax	159:4d1bf96a59cd	997	dataCheckSum(pseudoHeader.start, 12, 1); // start with the TCP checksum of the pseudoheader
nixnax	159:4d1bf96a59cd	998	ppp.tcp->checksumR = 0; // before TCP checksum calculations the checksum bytes must be set cleared
nixnax	161:d59f778bc8ab	999	unsigned int pseudoHeaderSum=dataCheckSum(ppp.tcpStart,tcpSize, 0); // continue the TCP checksum on the whole TCP packet
nixnax	159:4d1bf96a59cd	1000	ppp.tcp->checksumR = __REV16( pseudoHeaderSum); // tcp checksum done, store it in the TCP header
nixnax	160:bd701ad564cb	1001
nixnax	142:54d1543e23e5	1002	dumpHeaderIP(1); // dump outgoing IP header
nixnax	142:54d1543e23e5	1003	dumpHeaderTCP(1); // dump outgoing TCP header
nixnax	142:54d1543e23e5	1004	for (int i=0; i<45*1000/10; i++) { // 45 ms delay before sending frame - a typical internet delay time
nixnax	142:54d1543e23e5	1005	checkPc(); // catch any incoming characters
nixnax	142:54d1543e23e5	1006	wait_us(10); // wait less than 1 character duration at 115200
nixnax	142:54d1543e23e5	1007	}
nixnax	144:01d98cf7738e	1008	sendPppFrame(); // All preparation complete - send the TCP response
nixnax	142:54d1543e23e5	1009	if(0) dumpPPPFrame(); // set to 1 to dump transmitted ppp frame
nixnax	142:54d1543e23e5	1010	memset(ppp.pkt.buf+44,0,500); // flush out traces of previous data that we may scan for
nixnax	142:54d1543e23e5	1011	}
nixnax	142:54d1543e23e5	1012
nixnax	142:54d1543e23e5	1013	/// dump the TCP data to the debug serial port
nixnax	142:54d1543e23e5	1014	void dumpDataTCP()
nixnax	142:54d1543e23e5	1015	{
nixnax	142:54d1543e23e5	1016	int ipPktLen = (ppp.pkt.buf[6]<<8)\|ppp.pkt.buf[7]; // overall length of ip packet
nixnax	142:54d1543e23e5	1017	int ipHeaderLen = (ppp.pkt.buf[4]&0xf)*4; // length of ip header
nixnax	154:18b2bd92f557	1018	int headerSizeTcp = ((ppp.pkt.buf[4+ipHeaderLen+12]>>4)&0xf)*4;; // length of tcp header
nixnax	154:18b2bd92f557	1019	int dataLen = ipPktLen - ipHeaderLen - headerSizeTcp; // data is what's left after the two headers
nixnax	142:54d1543e23e5	1020	if (v1) {
nixnax	142:54d1543e23e5	1021	char pbuf[50]; // local print buffer
nixnax	142:54d1543e23e5	1022	checkPc();
nixnax	154:18b2bd92f557	1023	sprintf(pbuf, "TCP %d ipHeader %d tcpHeader %d Data %d\n", ipPktLen, ipHeaderLen, headerSizeTcp, dataLen); // 1 for more verbose
nixnax	142:54d1543e23e5	1024	checkPc();
nixnax	142:54d1543e23e5	1025	putsWhileCheckingInput( pbuf );
nixnax	142:54d1543e23e5	1026	}
nixnax	142:54d1543e23e5	1027	if (dataLen > 0) {
nixnax	154:18b2bd92f557	1028	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	1029	putsWhileCheckingInput( ppp.pkt.buf+4+ipHeaderLen+headerSizeTcp ); // print the tcp payload data
nixnax	142:54d1543e23e5	1030	putsWhileCheckingInput("\n");
nixnax	142:54d1543e23e5	1031	}
nixnax	142:54d1543e23e5	1032	}
nixnax	142:54d1543e23e5	1033
nixnax	142:54d1543e23e5	1034	/// handle an incoming TCP packet
nixnax	142:54d1543e23e5	1035	void TCPpacket()
nixnax	142:54d1543e23e5	1036	{
nixnax	142:54d1543e23e5	1037	dumpHeaderIP(0); // dump incoming packet header
nixnax	142:54d1543e23e5	1038	dumpHeaderTCP(0); // dump incoming packet header
nixnax	142:54d1543e23e5	1039	if (v2) dumpDataTCP();
nixnax	142:54d1543e23e5	1040	tcpHandler();
nixnax	142:54d1543e23e5	1041	}
nixnax	142:54d1543e23e5	1042
nixnax	142:54d1543e23e5	1043	/// handle the remaining IP protocols by ignoring them
nixnax	142:54d1543e23e5	1044	void otherProtocol()
nixnax	142:54d1543e23e5	1045	{
nixnax	142:54d1543e23e5	1046	debugPrintf("Other IP protocol");
nixnax	142:54d1543e23e5	1047	}
nixnax	142:54d1543e23e5	1048
nixnax	142:54d1543e23e5	1049	/// process an incoming IP packet
nixnax	142:54d1543e23e5	1050	void IPframe()
nixnax	142:54d1543e23e5	1051	{
nixnax	142:54d1543e23e5	1052	int protocol = ppp.pkt.buf[13];
nixnax	142:54d1543e23e5	1053	switch (protocol) {
nixnax	142:54d1543e23e5	1054	case 1:
nixnax	142:54d1543e23e5	1055	ICMPpacket();
nixnax	142:54d1543e23e5	1056	break;
nixnax	142:54d1543e23e5	1057	case 2:
nixnax	142:54d1543e23e5	1058	IGMPpacket();
nixnax	142:54d1543e23e5	1059	break;
nixnax	142:54d1543e23e5	1060	case 17:
nixnax	142:54d1543e23e5	1061	UDPpacket();
nixnax	142:54d1543e23e5	1062	break;
nixnax	142:54d1543e23e5	1063	case 6:
nixnax	142:54d1543e23e5	1064	TCPpacket();
nixnax	142:54d1543e23e5	1065	break;
nixnax	142:54d1543e23e5	1066	default:
nixnax	142:54d1543e23e5	1067	otherProtocol();
nixnax	142:54d1543e23e5	1068	}
nixnax	142:54d1543e23e5	1069	}
nixnax	142:54d1543e23e5	1070
nixnax	142:54d1543e23e5	1071	/// respond to LCP (line configuration protocol) configuration request) by allowing no options
nixnax	142:54d1543e23e5	1072	void LCPconfReq()
nixnax	142:54d1543e23e5	1073	{
nixnax	142:54d1543e23e5	1074	debugPrintf("LCP Config ");
nixnax	142:54d1543e23e5	1075	if (ppp.pkt.buf[7] != 4) {
nixnax	142:54d1543e23e5	1076	ppp.pkt.buf[4]=4; // allow only "no options" which means Maximum Receive Unit (MRU) is default 1500 bytes
nixnax	142:54d1543e23e5	1077	debugPrintf("Reject\n");
nixnax	144:01d98cf7738e	1078	sendPppFrame();
nixnax	142:54d1543e23e5	1079	} else {
nixnax	142:54d1543e23e5	1080	ppp.pkt.buf[4]=2; // ack zero conf
nixnax	142:54d1543e23e5	1081	debugPrintf("Ack\n");
nixnax	144:01d98cf7738e	1082	sendPppFrame();
nixnax	142:54d1543e23e5	1083	debugPrintf("LCP Ask\n");
nixnax	142:54d1543e23e5	1084	ppp.pkt.buf[4]=1; // request no options
nixnax	144:01d98cf7738e	1085	sendPppFrame();
nixnax	142:54d1543e23e5	1086	}
nixnax	142:54d1543e23e5	1087	}
nixnax	142:54d1543e23e5	1088
nixnax	142:54d1543e23e5	1089	/// handle LCP acknowledge packets by ignoring them
nixnax	142:54d1543e23e5	1090	void LCPconfAck()
nixnax	142:54d1543e23e5	1091	{
nixnax	142:54d1543e23e5	1092	debugPrintf("LCP Ack\n");
nixnax	142:54d1543e23e5	1093	}
nixnax	142:54d1543e23e5	1094
nixnax	143:c5019f856a56	1095	/// handle LCP end (disconnect) packets by acknowledging them and by setting ppp.online to false
nixnax	142:54d1543e23e5	1096	void LCPend()
nixnax	142:54d1543e23e5	1097	{
nixnax	142:54d1543e23e5	1098	ppp.pkt.buf[4]=6;
nixnax	144:01d98cf7738e	1099	sendPppFrame(); // acknowledge
nixnax	142:54d1543e23e5	1100	ppp.online=0; // start hunting for connect string again
nixnax	142:54d1543e23e5	1101	pppInitStruct(); // flush the receive buffer
nixnax	143:c5019f856a56	1102	debugPrintf("LCP End (Disconnect from host)\n");
nixnax	142:54d1543e23e5	1103	}
nixnax	142:54d1543e23e5	1104
nixnax	142:54d1543e23e5	1105	/// respond to other LCP requests by ignoring them
nixnax	142:54d1543e23e5	1106	void LCPother()
nixnax	142:54d1543e23e5	1107	{
nixnax	142:54d1543e23e5	1108	debugPrintf("LCP Other\n");
nixnax	142:54d1543e23e5	1109	dumpPPPFrame();
nixnax	142:54d1543e23e5	1110	}
nixnax	142:54d1543e23e5	1111
nixnax	142:54d1543e23e5	1112	/// process incoming LCP packets
nixnax	142:54d1543e23e5	1113	void LCPframe()
nixnax	142:54d1543e23e5	1114	{
nixnax	142:54d1543e23e5	1115	int code = ppp.pkt.buf[4];
nixnax	142:54d1543e23e5	1116	switch (code) {
nixnax	142:54d1543e23e5	1117	case 1:
nixnax	142:54d1543e23e5	1118	LCPconfReq();
nixnax	142:54d1543e23e5	1119	break; // config request
nixnax	142:54d1543e23e5	1120	case 2:
nixnax	142:54d1543e23e5	1121	LCPconfAck();
nixnax	142:54d1543e23e5	1122	break; // config ack
nixnax	142:54d1543e23e5	1123	case 5:
nixnax	142:54d1543e23e5	1124	LCPend();
nixnax	142:54d1543e23e5	1125	break; // end connection
nixnax	142:54d1543e23e5	1126	default:
nixnax	142:54d1543e23e5	1127	LCPother();
nixnax	142:54d1543e23e5	1128	}
nixnax	142:54d1543e23e5	1129	}
nixnax	142:54d1543e23e5	1130
nixnax	142:54d1543e23e5	1131	/// discard packets that are not IP, IPCP, or LCP
nixnax	142:54d1543e23e5	1132	void discardedFrame()
nixnax	142:54d1543e23e5	1133	{
nixnax	142:54d1543e23e5	1134	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	1135	}
nixnax	142:54d1543e23e5	1136
nixnax	142:54d1543e23e5	1137	/// determine the packet type (IP, IPCP or LCP) of incoming packets
nixnax	142:54d1543e23e5	1138	void determinePacketType()
nixnax	142:54d1543e23e5	1139	{
nixnax	142:54d1543e23e5	1140	if ( ppp.pkt.buf[0] != 0xff ) {
nixnax	142:54d1543e23e5	1141	debugPrintf("byte0 != ff\n");
nixnax	142:54d1543e23e5	1142	return;
nixnax	142:54d1543e23e5	1143	}
nixnax	142:54d1543e23e5	1144	if ( ppp.pkt.buf[1] != 3 ) {
nixnax	142:54d1543e23e5	1145	debugPrintf("byte1 != 3\n");
nixnax	142:54d1543e23e5	1146	return;
nixnax	142:54d1543e23e5	1147	}
nixnax	142:54d1543e23e5	1148	if ( ppp.pkt.buf[3] != 0x21 ) {
nixnax	142:54d1543e23e5	1149	debugPrintf("byte2 != 21\n");
nixnax	142:54d1543e23e5	1150	return;
nixnax	142:54d1543e23e5	1151	}
nixnax	142:54d1543e23e5	1152	int packetType = ppp.pkt.buf[2];
nixnax	142:54d1543e23e5	1153	switch (packetType) {
nixnax	142:54d1543e23e5	1154	case 0xc0:
nixnax	142:54d1543e23e5	1155	LCPframe();
nixnax	142:54d1543e23e5	1156	break; // link control
nixnax	142:54d1543e23e5	1157	case 0x80:
nixnax	142:54d1543e23e5	1158	IPCPframe();
nixnax	142:54d1543e23e5	1159	break; // IP control
nixnax	142:54d1543e23e5	1160	case 0x00:
nixnax	142:54d1543e23e5	1161	IPframe();
nixnax	142:54d1543e23e5	1162	break; // IP itself
nixnax	142:54d1543e23e5	1163	default:
nixnax	142:54d1543e23e5	1164	discardedFrame();
nixnax	142:54d1543e23e5	1165	}
nixnax	142:54d1543e23e5	1166	}
nixnax	142:54d1543e23e5	1167
nixnax	146:a45f49a2b29c	1168	/// a sniffer tool to assist in figuring out where in the code we are having characters in the input buffer
nixnax	146:a45f49a2b29c	1169	void sniff()
nixnax	146:a45f49a2b29c	1170	{
nixnax	146:a45f49a2b29c	1171	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	1172	}
nixnax	146:a45f49a2b29c	1173
nixnax	142:54d1543e23e5	1174	/// scan the PPP serial input stream for frame start markers
nixnax	143:c5019f856a56	1175	void waitForPppFrame()
nixnax	142:54d1543e23e5	1176	{
nixnax	142:54d1543e23e5	1177	while(1) {
nixnax	142:54d1543e23e5	1178	checkPc(); // handle received characters
nixnax	142:54d1543e23e5	1179	if ( ppp.rx.head != ppp.rx.tail ) {
nixnax	142:54d1543e23e5	1180	int oldTail = ppp.rx.tail; // remember where the character is located in the buffer
nixnax	142:54d1543e23e5	1181	int rx = pc_getBuf(); // get the character
nixnax	142:54d1543e23e5	1182	if (rx==FRAME_7E) {
nixnax	142:54d1543e23e5	1183	if (ppp.firstFrame) { // is this the start of the first frame start
nixnax	142:54d1543e23e5	1184	ppp.firstFrame=0;
nixnax	142:54d1543e23e5	1185	ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
nixnax	142:54d1543e23e5	1186	ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where first frame started
nixnax	142:54d1543e23e5	1187	} else {
nixnax	142:54d1543e23e5	1188	ppp.hdlc.frameEndIndex=oldTail; // mark the frame end character
nixnax	142:54d1543e23e5	1189	processPPPFrame(ppp.hdlc.frameStartIndex, ppp.hdlc.frameEndIndex); // process the frame
nixnax	142:54d1543e23e5	1190	ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
nixnax	142:54d1543e23e5	1191	ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where next frame started
nixnax	142:54d1543e23e5	1192	break;
nixnax	142:54d1543e23e5	1193	}
nixnax	142:54d1543e23e5	1194	}
nixnax	142:54d1543e23e5	1195	}
nixnax	142:54d1543e23e5	1196	}
nixnax	142:54d1543e23e5	1197	}
nixnax	142:54d1543e23e5	1198
nixnax	153:7993def8663f	1199	/// 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	1200	// Note: a 0x7E in the input stream (ppp start of frame character) will also set ppp.online to true - see checkPc();
nixnax	153:7993def8663f	1201	void waitForPcConnectString()
nixnax	142:54d1543e23e5	1202	{
nixnax	142:54d1543e23e5	1203	while(ppp.online == 0) {
nixnax	142:54d1543e23e5	1204	checkPc(); // gather received characters
nixnax	142:54d1543e23e5	1205	// search for Windows Dialup Networking "Direct Connection Between Two Computers" expected connect string
nixnax	142:54d1543e23e5	1206	char * found1 = strstr( (char *)ppp.rx.buf, "CLIENT" );
nixnax	142:54d1543e23e5	1207	if (found1 != NULL) {
nixnax	142:54d1543e23e5	1208	// respond with Windows Dialup networking expected "Direct Connection Between Two Computers" response string
nixnax	143:c5019f856a56	1209	if (v0) debugPrintf("Connected: Found connect string \"CLIENT\", sent \"CLIENTSERVER\"\n");
nixnax	142:54d1543e23e5	1210	pc.puts("CLIENTSERVER");
nixnax	142:54d1543e23e5	1211	ppp.online=1; // we are connected - set flag so we stop looking for the connect string
nixnax	142:54d1543e23e5	1212	checkPc();
nixnax	142:54d1543e23e5	1213	}
nixnax	142:54d1543e23e5	1214	}
nixnax	142:54d1543e23e5	1215	}
nixnax	142:54d1543e23e5	1216
nixnax	144:01d98cf7738e	1217	/// Initialize PPP data structure and set serial port(s) baud rate(s)
nixnax	144:01d98cf7738e	1218	void initializePpp()
nixnax	142:54d1543e23e5	1219	{
nixnax	142:54d1543e23e5	1220	pc.baud(115200); // USB serial port to pc
nixnax	144:01d98cf7738e	1221	debugBaudRate(115200); // baud rate for (optional) debug serial port
nixnax	142:54d1543e23e5	1222	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	1223	pppInitStruct(); // initialize all the PPP properties
nixnax	143:c5019f856a56	1224	}

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Repository details

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

The code in this repository is MIT licensed.