RealTimeCompLab2
RealtimeCompLab2
Dependencies: mbed
Fork of
PPP-Blinky
by 
Nicolas Nackel
main.cpp
- Committer:
- nixnax
- Date:
- 2017-06-05
- Revision:
- 68:0b74763ae67f
- Parent:
- 67:a63e3486bcda
- Child:
- 69:23f560087c16
File content as of revision 68:0b74763ae67f:
#include "mbed.h"
// Copyright 2016 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.
// PPP-Blinky - "My Internet Of Thing"
// A Tiny Webserver Using Windows XP/7/8/10 Networking Over A Serial Port.
// Also receives UDP packets and responds to ping (ICMP Echo requests)
// Notes and Instructions
// http://bit.ly/PPP-Blinky-Instructions
// Handy reading material
// https://technet.microsoft.com/en-us/library/cc957992.aspx
// https://en.wikibooks.org/wiki/Serial_Programming/IP_Over_Serial_Connections
// http://bit.ly/dialup777error - how to solve Dial Up Error 777 in Windows 7/8/10
// http://atari.kensclassics.org/wcomlog.htm
// Handy tools
// https://ttssh2.osdn.jp/index.html.en - Tera Term, a good terminal program to monitor the debug output from the second serial port with!
// Wireshark - can't monitor Dial-Up network packets on windows, but useful - can import our dumpFrame routine's hex output
// Microsoft network monitor - real-time monitoring of all our packets
// http://pingtester.net/ - nice tool for high rate ping testing
// http://www.sunshine2k.de/coding/javascript/crc/crc_js.html - Correctly calculates the 16-bit FCS (crc) on our frames (Choose CRC16_CCITT_FALSE)
// The curl.exe program in Windows Powershell - use it like this to stress test the webserver: while (1) { curl 172.10.10.1 }
// https://technet.microsoft.com/en-us/sysinternals/pstools.aspx - psping for fast testing of ICMP ping function
// https://eternallybored.org/misc/netcat/ - use netcat -u 172.10.10.1 80 to send/receive UDP packets from PPP-Blinky
// The #define below enables/disables a SECOND (optional) serial port that prints out interesting diagnostic messages.
// Change to SERIAL_PORT_MONITOR_YES to enable diagnostics messages. You need to wire a second serial port to your mbed hardware to monitor this.
#define SERIAL_PORT_MONITOR_NO /* or SERIAL_PORT_MONITOR_YES */
#ifndef SERIAL_PORT_MONITOR_NO
Serial xx(PC_10, PC_11); // Not required to run, if you get compile error here, change #define SERIAL_PORT_MONITOR_YES to #define SERIAL_PORT_MONITOR_NO
#define debug(x...) xx.printf (x)
#else
#define debug(x...) {}
#endif
// verbosity flag used in debug printouts - change to 0 to see less debug info. Lots of interesting info.
#define v0 1
// verbosity flag used in debug printouts - change to 0 to see less debug info. Lots of interesting info.
#define v1 1
// this is the webpage we serve when we get an HTTP request
// keep size under 900 bytes to fit in a single frame
const static char ourWebPage[] = "\
<!DOCTYPE html>\
<html>\
<head>\
<title>mbed-PPP-Blinky</title>\
<script>\
window.onload=function(){\
setInterval(function(){function x(){return document.getElementById('w');};\
x().textContent = parseInt(x().textContent)+1;},100);};\
</script>\
</head>\
<body style=\"font-family: sans-serif; font-size:30px; color:#807070\">\
<h1>mbed PPP-Blinky Up and Running</h1>\
<h1 id=\"w\" style=\"text-align:center;\">0</h1>\
<h1><a href=\"http://bit.ly/pppBlink2\">Source on mbed</a></h1>\
</body>\
</html>"; // current size is approximately 470 characters
// The serial port on your mbed hardware. Your PC should view this as a standard dial-up networking modem. See instructions at the top.
// On a typical mbed hardware platform this is a USB virtual com port (VCP)
Serial pc(USBTX, USBRX); // usb virtual com port
DigitalOut led1(LED1); // this led toggles when a packet is received
// the standard hdlc frame start/end character. It's the tilde character "~"
#define FRAME_7E (0x7e)
// the serial port receive buffer and packet buffer
#define BUFLEN (1<<12)
char rxbufppp[BUFLEN]; // BUFLEN MUST be a power of two because we use & operator for fast wrap-around in rxHandler
char hdlcBuffer[2000]; // send and receive buffer for unstuffed (decoded) hdlc frames
// a structure to keep all our ppp globals in
struct pppType {
int online; // we hunt for a PPP connection if this is zero
int ident; // our IP ident value
unsigned int seq; // our TCP sequence number
int crc; // for calculating IP and TCP CRCs
int ledState; // state of LED1
struct {
char * buf;
volatile int head;
volatile int tail;
} rx; // serial port objects
struct {
int len; // number of bytes in buffer
int crc; // PPP CRC (frame check)
char * buf; // the actual buffer
} pkt; // ppp buffer objects
struct {
int frameStartIndex; // frame start marker
int frameEndIndex; // frame end marker
int frameBusy; // busy capturing a frame
} hdlc; // hdlc frame objects
};
pppType ppp; // our global - definitely not thread safe
// Initialize our globals
void pppInitStruct()
{
ppp.online=0;
ppp.rx.buf=rxbufppp;
ppp.rx.tail=0;
ppp.rx.head=0;
ppp.pkt.buf=hdlcBuffer;
ppp.pkt.len=0;
ppp.ident=0;
ppp.seq=1000;
ppp.ledState=0;
ppp.hdlc.frameBusy=0;
}
void led1Toggle()
{
ppp.ledState = ppp.ledState? 0 : 1;
led1 = ppp.ledState;
}
void crcReset()
{
ppp.crc=0xffff; // crc restart
}
void crcDo(int x) // cumulative crc
{
for (int i=0; i<8; i++) {
ppp.crc=((ppp.crc&1)^(x&1))?(ppp.crc>>1)^0x8408:ppp.crc>>1; // crc calculator
x>>=1;
}
}
int crcBuf(char * buf, int size) // crc on an entire block of memory
{
crcReset();
for(int i=0; i<size; i++)crcDo(*buf++);
return ppp.crc;
}
void rxHandler() // serial port receive interrupt handler
{
while ( pc.readable() ) {
int hd = (ppp.rx.head+1)&(BUFLEN-1); // increment/wrap
if ( hd == ppp.rx.tail ) break; // watch for buffer full
ppp.rx.buf[ppp.rx.head]=pc.getc(); // insert in rx buffer
ppp.rx.head = hd; // update head pointer
}
}
int rxbufNotEmpty() // check if rx buffer has data
{
__disable_irq(); // critical section start
int emptyStatus = (ppp.rx.head==ppp.rx.tail) ? 0 : 1 ;
__enable_irq(); // critical section end
return emptyStatus;
}
int pc_getBuf() // get one character from the buffer
{
__disable_irq(); // critical section start
int x = ppp.rx.buf[ ppp.rx.tail ];
ppp.rx.tail=(ppp.rx.tail+1)&(BUFLEN-1);
__enable_irq(); // critical section end
return x;
}
void processHDLCFrame(int start, int end) // process received frame
{
led1Toggle(); // change led1 state on every frame we receive
if(start==end) {
pc.putc(0x7e);
return;
}
crcReset();
char * dest = ppp.pkt.buf;
ppp.pkt.len=0;
int unstuff=0;
int idx = start;
while(1) {
if (unstuff==0) {
if (rxbufppp[idx]==0x7d) unstuff=1;
else {
*dest = rxbufppp[idx];
ppp.pkt.len++;
dest++;
crcDo(rxbufppp[idx]);
}
} else { // unstuff characters prefixed with 0x7d
*dest = rxbufppp[idx]^0x20;
ppp.pkt.len++;
dest++;
crcDo(rxbufppp[idx]^0x20);
unstuff=0;
}
idx = (idx+1) & (BUFLEN-1);
if (idx == end) break;
}
ppp.pkt.crc = ppp.crc & 0xffff;
if (ppp.pkt.crc == 0xf0b8) { // check for good CRC
void determinePacketType(); // declaration only
determinePacketType();
} else if (v0) {
debug("PPP FCS(crc) Error CRC=%x Length = %d\n",ppp.pkt.crc,ppp.pkt.len); // ignore packets with CRC errors but print a debug line
}
}
// Note - the hex output of dumpFrame() can be imported into WireShark
// Capture the frame's hex output in your terminal program and save as a text file
// In WireShark, use "Import Hex File". Options are: Offset=None, Protocol=PPP.
void dumpFrame()
{
for(int i=0; i<ppp.pkt.len; i++) debug("%02x ", ppp.pkt.buf[i]);
debug(" C=%02x %02x L=%d\n", ppp.pkt.crc&0xff, (ppp.pkt.crc>>8)&0xff, ppp.pkt.len);
}
void hdlcPut(int ch) // do hdlc handling of special (flag) characters
{
if ( (ch<0x20) || (ch==0x7d) || (ch==0x7e) ) {
pc.putc(0x7d);
pc.putc(ch^0x20); // these characters need special handling
} else {
pc.putc(ch);
}
}
void sendFrame() // send a PPP frame in HDLC format
{
int crc = crcBuf(ppp.pkt.buf, ppp.pkt.len-2); // update crc
ppp.pkt.buf[ ppp.pkt.len-2 ] = (~crc>>0); // fcs lo (crc)
ppp.pkt.buf[ ppp.pkt.len-1 ] = (~crc>>8); // fcs hi (crc)
pc.putc(0x7e); // hdlc start-of-frame "flag"
for(int i=0; i<ppp.pkt.len; i++) hdlcPut( ppp.pkt.buf[i] );
pc.putc(0x7e); // hdlc end-of-frame "flag"
}
void ipConfigRequestHandler()
{
debug("IPCP Conf ");
if ( ppp.pkt.buf[7] != 4 ) {
debug("Rej\n"); // reject any options that are requested
ppp.pkt.buf[4]=4;
sendFrame();
} else {
debug("Ack\n");
ppp.pkt.buf[4]=2; // ack the minimum
sendFrame(); // acknowledge
debug("IPCP Ask\n");
// send our own request now
ppp.pkt.buf[4]=1; // request no options
ppp.pkt.buf[5]++; // next sequence
sendFrame(); // this is our request
}
}
void ipAckHandler()
{
debug("IPCP Grant\n");
}
void ipNackHandler()
{
debug("IPCP Nack\n");
}
void ipDefaultHandler()
{
debug("IPCP Other\n");
}
void IPCPframe()
{
int code = ppp.pkt.buf[4]; // packet type is here
switch (code) {
case 1:
ipConfigRequestHandler();
break;
case 2:
ipAckHandler();
break;
case 3:
ipNackHandler();
break;
default:
ipDefaultHandler();
}
}
void UDPpacket()
{
char * udpPkt = ppp.pkt.buf+4; // udp packet start
int headerSizeIP = (( udpPkt[0]&0xf)*4);
char * udpBlock = udpPkt + headerSizeIP; // udp info start
#ifndef SERIAL_PORT_MONITOR_NO
char * udpSrc = udpBlock; // source port
char * udpDst = udpBlock+2; // destination port
#endif
char * udpLen = udpBlock+4; // udp data length
char * udpInf = udpBlock+8; // actual start of info
#ifndef SERIAL_PORT_MONITOR_NO
int srcPort = (udpSrc[0]<<8) | udpSrc[1];
int dstPort = (udpDst[0]<<8) | udpDst[1];
char * srcIP = udpPkt+12; // udp src addr
char * dstIP = udpPkt+16; // udp dst addr
#endif
#define UDP_HEADER_SIZE 8
int udpLength = ((udpLen[0]<<8) | udpLen[1]) - UDP_HEADER_SIZE; // size of the actual udp data
if(v1) debug("UDP %d.%d.%d.%d:%d ", srcIP[0],srcIP[1],srcIP[2],srcIP[3],srcPort);
if(v1) debug("%d.%d.%d.%d:%d ", dstIP[1],dstIP[1],dstIP[1],dstIP[1],dstPort);
debug("Len %d ", udpLength);
int printSize = udpLength;
if (printSize > 20) printSize = 20; // print only first 20 characters
if (v0) {
for (int i=0; i<printSize; i++) {
char ch = udpInf[i];
if (ch>31 && ch<127) {
debug("%c", ch);
} else {
debug("_");
}
}
debug("\n");
}
}
int dataCheckSum(char * ptr, int len)
{
int sum=0;
int placeHolder;
if (len&1) {
placeHolder = ptr[len-1]; // when length is odd stuff in a zero byte
ptr[len-1]=0;
}
for (int i=0; i<len/2; i++) {
int hi = *ptr;
ptr++;
int lo = *ptr;
ptr++;
int val = ( lo & 0xff ) | ( (hi<<8) & 0xff00 );
sum = sum + val;
}
sum = sum + (sum>>16);
if (len&1) {
ptr[len-1] = placeHolder; // restore the last byte for odd lengths
}
return ~sum;
}
void headerCheckSum()
{
int len =(ppp.pkt.buf[4]&0xf)*4; // length of header in bytes
char * ptr = ppp.pkt.buf+4; // start of ip packet
int sum=0;
for (int i=0; i<len/2; i++) {
int hi = *ptr;
ptr++;
int lo = *ptr;
ptr++;
int val = ( lo & 0xff ) | ( (hi<<8) & 0xff00 );
sum = sum + val;
}
sum = sum + (sum>>16);
sum = ~sum;
ppp.pkt.buf[14]= (sum>>8);
ppp.pkt.buf[15]= (sum );
}
void ICMPpacket() // internet control message protocol
{
char * ipPkt = ppp.pkt.buf+4; // ip packet start
char * pktLen = ipPkt+2;
int packetLength = (pktLen[0]<<8) | pktLen[1]; // icmp packet length
int headerSizeIP = (( ipPkt[0]&0xf)*4);
char * icmpType = ipPkt + headerSizeIP; // icmp data start
char * icmpSum = icmpType+2; // icmp checksum
#define ICMP_TYPE_PING_REQUEST 8
if ( icmpType[0] == ICMP_TYPE_PING_REQUEST ) {
char * ipTTL = ipPkt+8; // time to live
ipTTL[0]--; // decrement time to live
char * srcAdr = ipPkt+12;
char * dstAdr = ipPkt+16;
#ifndef SERIAL_PORT_MONITOR_NO
int icmpIdent = (icmpType[4]<<8)|icmpType[5];
int icmpSequence = (icmpType[6]<<8)|icmpType[7];
#endif
debug("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]);
debug("Ident %04x Sequence %04d ",icmpIdent,icmpSequence);
char src[4];
char dst[4];
memcpy(src, srcAdr,4);
memcpy(dst, dstAdr,4);
memcpy(srcAdr, dst,4);
memcpy(dstAdr, src,4); // swap src & dest ip
char * chkSum = ipPkt+10;
chkSum[0]=0;
chkSum[1]=0;
headerCheckSum(); // new ip header checksum
#define ICMP_TYPE_ECHO_REPLY 0
icmpType[0]=ICMP_TYPE_ECHO_REPLY; // icmp echo reply
icmpSum[0]=0;
icmpSum[1]=0; // zero the checksum for recalculation
int icmpLength = packetLength - headerSizeIP; // length of ICMP data portion
int sum = dataCheckSum( icmpType, icmpLength); // this checksum on icmp data portion
icmpSum[0]=sum>>8;
icmpSum[1]=sum; // new checksum for ICMP data portion
int printSize = icmpLength-8; // exclude size of icmp header
char * icmpData = icmpType+8; // the actual payload data is after the header
if (printSize > 10) printSize = 10; // print up to 20 characters
if (v0) {
for (int i=0; i<printSize; i++) {
char ch = icmpData[i];
if (ch>31 && ch<127) {
debug("%c",ch);
} else {
debug("_");
}
}
debug("\n");
}
sendFrame(); // reply to the ping
} else {
if (v0) {
debug("ICMP type=%d \n", icmpType[0]);
}
}
}
void IGMPpacket() // internet group management protocol
{
if (v0) {
debug("IGMP type=%d \n", ppp.pkt.buf[28]);
}
}
void dumpHeaderIP ()
{
char * ipPkt = ppp.pkt.buf+4; // ip packet start
#ifndef SERIAL_PORT_MONITOR_NO
char * version = ipPkt; // top 4 bits
char * ihl = ipPkt; // bottom 4 bits
char * dscp = ipPkt+1; // top 6 bits
char * ecn = ipPkt+1; // lower 2 bits
char * pktLen = ipPkt+2; // 2 bytes
char * ident = ipPkt+4; // 2 bytes
char * flags = ipPkt+6; // 2 bits
char * ttl = ipPkt+8; // 1 byte
char * protocol = ipPkt+9; // 1 byte
char * headercheck= ipPkt+10; // 2 bytes
#endif
char * srcAdr = ipPkt+12; // 4 bytes
char * dstAdr = ipPkt+16; // 4 bytes = total of 20 bytes
#ifndef SERIAL_PORT_MONITOR_NO
int versionIP = (version[0]>>4)&0xf;
int headerSizeIP = (ihl[0]&0xf)*4;
int dscpIP = (dscp[0]>>2)&0x3f;
int ecnIP = ecn[0]&3;
int packetLength = (pktLen[0]<<8)|pktLen[1]; // ip total packet length
int identIP = (ident[0]<<8)|ident[1];
int flagsIP = flags[0]>>14&3;
int ttlIP = ttl[0];
int protocolIP = protocol[0];
int checksumIP = (headercheck[0]<<8)|headercheck[1];
#endif
char srcIP [16];
snprintf(srcIP,16, "%d.%d.%d.%d", srcAdr[0],srcAdr[1],srcAdr[2],srcAdr[3]);
char dstIP [16];
snprintf(dstIP,16, "%d.%d.%d.%d", dstAdr[0],dstAdr[1],dstAdr[2],dstAdr[3]);
if (v0) debug("IP %s %s v%d h%d d%d e%d L%d ",srcIP,dstIP,versionIP,headerSizeIP,dscpIP,ecnIP,packetLength);
if (v0) debug("i%04x f%d t%d p%d C%04x\n",identIP,flagsIP,ttlIP,protocolIP,checksumIP);
}
void dumpHeaderTCP()
{
int headerSizeIP = (ppp.pkt.buf[4]&0xf)*4; // header size of ip portion
char * tcpStart = ppp.pkt.buf+4+headerSizeIP; // start of tcp packet
#ifndef SERIAL_PORT_MONITOR_NO
char * seqtcp = tcpStart + 4; // 4 bytes
char * acktcp = tcpStart + 8; // 4 bytes
#endif
char * flagbitstcp = tcpStart + 12; // 9 bits
#ifndef SERIAL_PORT_MONITOR_NO
unsigned int seq = (seqtcp[0]<<24)|(seqtcp[1]<<16)|(seqtcp[2]<<8)|(seqtcp[3]);
unsigned int ack = (acktcp[0]<<24)|(acktcp[1]<<16)|(acktcp[2]<<8)|(acktcp[3]);
#endif
int flags = ((flagbitstcp[0]&1)<<8)|flagbitstcp[1];
char flagInfo[10]; // text string presentating the TCP flags
memset(flagInfo,'.', 9); // fill string with "........."
memset(flagInfo,0,1); // null terminate string
if (flags & (1<<0)) flagInfo[0]='F';
if (flags & (1<<1)) flagInfo[1]='S';
if (flags & (1<<2)) flagInfo[2]='R';
if (flags & (1<<3)) flagInfo[3]='P';
if (flags & (1<<4)) flagInfo[4]='A';
if (flags & (1<<5)) flagInfo[5]='U';
if (flags & (1<<6)) flagInfo[6]='E';
if (flags & (1<<7)) flagInfo[7]='C';
if (flags & (1<<8)) flagInfo[8]='N';
if (v0) {
debug("Flags %s Seq %u Ack %u", flagInfo, seq, ack); // show the flags in debug
}
}
int httpResponse(char * dataStart)
{
int n=0; // number of bytes we have printed so far
if(strncmp(dataStart, "GET / HTTP/1.1", 14) == 0 ) {
n=n+sprintf(n+dataStart,"HTTP/1.1 200 OK\r\nServer: PPP-Blinky\r\n"); // http header
n=n+sprintf(n+dataStart,"Content-Length: "); // http header
int contentLengthStart = n; // remember where Content-Length is in buffer
n=n+sprintf(n+dataStart,"?????\r\n"); // leave five spaces for content length - will be updated later
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)
int nHeader=n; // byte size of the HTTP header. Note - seems like this must be 1+(multiple of four)
// this is where we insert our web page into the buffer
n=n+sprintf(n+dataStart,"%s\r\n", ourWebPage);
#define CONTENTLENGTHSIZE 5
char contentLengthString[CONTENTLENGTHSIZE+1]; // temporary buffer to create Content-Length string
snprintf(contentLengthString,CONTENTLENGTHSIZE+1,"%*d",CONTENTLENGTHSIZE,n-nHeader); // print Content-Length with leading spaces and fixed width equal to csize
memcpy(dataStart+contentLengthStart, contentLengthString, CONTENTLENGTHSIZE); // copy Content-Length to it's place in the send buffer
if (v0) {
debug("HTTP GET BufferSize %d*32=%d Header %d Content-Length %d Total %d Available %d\n",dataLen/32,dataLen,nHeader,contentLength,n,dataLen-n);
}
} else { // all remaining requests get 404 Not Found response
n=n+sprintf(n+dataStart,"HTTP/1.1 404 Not Found\r\nServer: PPP-Blinky\r\n"); // http header
n=n+sprintf(n+dataStart,"Content-Length: "); // http header
int contentLengthStart = n; // remember where Content-Length is in buffer
n=n+sprintf(n+dataStart,"?????\r\n"); // leave five spaces for content length - will be updated later
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)
int nHeader=n; // byte total of all headers. Note - seems like this must be 1+(multiple of four)
n=n+sprintf(n+dataStart,"<!DOCTYPE html><html><head></head>"); // html start
n=n+sprintf(n+dataStart,"<body><h1>File Not Found</h1></body>");
n=n+sprintf(n+dataStart,"</html>\r\n"); // html end
char contentLengthString[CONTENTLENGTHSIZE+1]; // temporary buffer to create Content-Length string
snprintf(contentLengthString,CONTENTLENGTHSIZE+1,"%*d",CONTENTLENGTHSIZE,n-nHeader); // print Content-Length with leading spaces and fixed width equal to csize
memcpy(dataStart+contentLengthStart, contentLengthString, CONTENTLENGTHSIZE); // copy Content-Length to it's place in the send buffer
if (v0) {
debug("HTTP GET BufSize %d*32=%d Header %d Content-Length %d Total %d Available %d\n",dataLen/32,dataLen,nHeader,contentLength,n,dataLen-n);
}
}
return n; // total byte size of our response
}
void tcpHandler()
{
char * ipPkt = ppp.pkt.buf+4; // ip packet start
char * headercheck= ipPkt+10; // 2 bytes
char * ihl = ipPkt; // bottom 4 bits
char * ident = ipPkt+4; // 2 bytes
char * pktLen = ipPkt+2; // 2 bytes
char * protocol = ipPkt+9; // 1 byte
char * srcAdr = ipPkt+12; // 4 bytes
char * dstAdr = ipPkt+16; // 4 bytes = total of 20 bytes
int headerSizeIP = (ihl[0]&0xf)*4;
int packetLength = (pktLen[0]<<8)|pktLen[1]; // ip total packet length
ident[0] = ppp.ident>>8;
ident[1] = ppp.ident>>0; // insert OUR ident
char * s = ppp.pkt.buf+4+headerSizeIP; // start of tcp packet
char * srctcp = s + 0; // 2 bytes
char * dsttcp = s + 2; // 2 bytes
char * seqtcp = s + 4; // 4 bytes
char * acktcp = s + 8; // 4 bytes
char * offset = s + 12; // 4 bits
char * flagbitstcp = s + 12; // 9 bits
char * checksumtcp = s + 16; // 2 bytes
int tcpSize = packetLength - headerSizeIP;
int headerSizeTCP = ((offset[0]>>4)&0x0f)*4; // size of tcp header only
int protocolIP = protocol[0];
unsigned int seq = (seqtcp[0]<<24)|(seqtcp[1]<<16)|(seqtcp[2]<<8)|(seqtcp[3]);
unsigned int ack = (acktcp[0]<<24)|(acktcp[1]<<16)|(acktcp[2]<<8)|(acktcp[3]);
int flagsTCP = ((flagbitstcp[0]&1)<<8)|flagbitstcp[1];
char * dataStart = ppp.pkt.buf + 4 + headerSizeIP + headerSizeTCP; // start of data block after TCP header
int tcpDataSize = tcpSize - headerSizeTCP; // size of data block after TCP header
#define TCP_FLAG_ACK (1<<4)
#define TCP_FLAG_SYN (1<<1)
#define TCP_FLAG_PSH (1<<3)
#define TCP_FLAG_RST (1<<2)
#define TCP_FLAG_FIN (1<<0)
// A sparse TCP flag interpreter that implements simple TCP connections from a single source
// Clients are allowed ONE push packet, after which the link is closed with a FIN flag in the ACK packet
// This strategy allows web browsers, netcat and curl to work ok while keeping the state machine simple
int dataLen = 0; // most of our responses will have zero TCP data, only a header
int flagsOut = TCP_FLAG_ACK; // the default case is an ACK packet
int fastResponse = 0; // normally you wait 200ms before sending a packet but this can make it faster
ppp.seq = ack; // always adopt their sequence number calculation in place of doing our own calculation
if ( flagsTCP == TCP_FLAG_ACK ) {
if (tcpDataSize == 0) { // ignore - just an empty ack packet
return;
}
} else if ( (flagsTCP & TCP_FLAG_SYN) != 0 ) { // got SYN flag
flagsOut = TCP_FLAG_SYN | TCP_FLAG_ACK; // do a syn-ack
seq++; // for SYN flag we have to increase sequence by 1
} else if ( (flagsTCP & TCP_FLAG_FIN) != 0 ) { // got FIN flag
seq++; // for FIN flag we have to increase sequence by 1
} else if ( (flagsTCP & TCP_FLAG_PSH) != 0 ) { // got PSH flag (push)
flagsOut = TCP_FLAG_ACK | TCP_FLAG_FIN; // for every push we answer once AND close the link
fastResponse = 1; // we can respond fast to a push
// It's a push, so let's check the incoming data for an HTTP GET request
if ( strncmp(dataStart, "GET ", 4) == 0) { // do we see an http GET command
dataLen = httpResponse(dataStart); // send an http response
}
}
// All the TCP flag handling is now done
// Now we have to recalculate all the header sizes, swap IP address/port source and destination, and do the IP and TCP checksums
char tempHold[12]; // it's 12 long because we later reuse it when building the TCP pseudo-header
memcpy(tempHold, srcAdr,4);
memcpy(srcAdr, dstAdr,4);
memcpy(dstAdr, tempHold,4); // swap ip address source/dest
memcpy(tempHold, srctcp,2);
memcpy(srctcp, dsttcp,2);
memcpy(dsttcp, tempHold,2); // swap ip port source/dest
ack = seq + tcpDataSize; // acknowledge the number of data bytes that they sent by adding it to "our" sequence number
seq = ppp.seq; // set up the sequence number we have to respond with
acktcp[0]=ack>>24;
acktcp[1]=ack>>16;
acktcp[2]=ack>>8;
acktcp[3]=ack>>0; // save ack 32-bit integer
seqtcp[0]=seq>>24;
seqtcp[1]=seq>>16;
seqtcp[2]=seq>>8;
seqtcp[3]=seq>>0; // save seq 32-bit integer
flagbitstcp[1] = flagsOut; // set up the new flags
int newPacketSize = headerSizeIP + headerSizeTCP + dataLen; // calculate size of the outgoing packet
pktLen[0] = (newPacketSize>>8);
pktLen[1]=newPacketSize; // ip total packet size
ppp.pkt.len = newPacketSize+6; // ppp packet length
tcpSize = headerSizeTCP + dataLen; // tcp packet size
// the header is all set up, now do the IP and TCP checksums
headercheck[0]=0; // IP header checksum
headercheck[1]=0; // IP header checksum
headerCheckSum(); // calculate the IP header checksum
// 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
// this header contains the most important parts of the IP header, i.e. source and destination address, protocol number and data length.
char * pseudoHeader = s-12; // mark the start of the TCP pseudo-header
memcpy(tempHold, pseudoHeader, 12); // preserve the 12 bytes of the IP header where the TCP pseudo-Header will be built
memcpy( pseudoHeader+0, srcAdr, 8); // IP source and destination addresses from IP header
memset( pseudoHeader+8, 0, 1); // reserved, set to zero
memset( pseudoHeader+9, protocolIP, 1); // protocol from IP header
memset( pseudoHeader+10, tcpSize>>8, 1); // size of IP data (TCP packet size)
memset( pseudoHeader+11, tcpSize, 1); // size of IP data (TCP packet size)
// pseudo-header built, now we can calculate TCP checksum
checksumtcp[0]=0;
checksumtcp[1]=0;
int pseudoHeaderSum=dataCheckSum(pseudoHeader,tcpSize+12); // calculate the TCP checksum starting at the pseudo-header
checksumtcp[0]=pseudoHeaderSum>>8;
checksumtcp[1]=pseudoHeaderSum;
memcpy( s-12, tempHold, 12); // restore the 12 bytes that the pseudo-header overwrote
if (fastResponse==1) {
fastResponse=0; // reset and skip 200 ms wait
} else {
// normally, you wait 200 ms before sending a TCP packet
// remove the wait to respond faster
// wait(0.2);
}
sendFrame(); // All done! Send the TCP packet
ppp.seq = ppp.seq + dataLen; // increase OUR sequence by the outgoing data length - for the next round
}
void dumpDataTCP()
{
int ipPktLen = (ppp.pkt.buf[6]<<8)|ppp.pkt.buf[7]; // overall length of ip packet
int ipHeaderLen = (ppp.pkt.buf[4]&0xf)*4; // length of ip header
int headerSizeTCP = ((ppp.pkt.buf[4+ipHeaderLen+12]>>4)&0xf)*4;; // length of tcp header
int dataLen = ipPktLen - ipHeaderLen - headerSizeTCP; // data is what's left after the two headers
if (v1) {
debug("TCP %d ipHeader %d tcpHeader %d Data %d\n", ipPktLen, ipHeaderLen, headerSizeTCP, dataLen); // 1 for more verbose
}
if (dataLen > 0) {
ppp.pkt.buf[4+ipHeaderLen+headerSizeTCP+dataLen]=0; // insert a null after the data so debug printf stops printing after the data
debug("%s\n",ppp.pkt.buf+4+ipHeaderLen+headerSizeTCP); // show the data
}
}
void TCPpacket()
{
char * ipPkt = ppp.pkt.buf+4; // ip packet start
#ifndef SERIAL_PORT_MONITOR_NO
char * version = ipPkt; // top 4 bits
char * ihl = ipPkt; // bottom 4 bits
char * dscp = ipPkt+1; // top 6 bits
char * ecn = ipPkt+1; // lower 2 bits
char * pktLen = ipPkt+2; // 2 bytes
char * ident = ipPkt+4; // 2 bytes
char * flags = ipPkt+6; // 2 bits
char * ttl = ipPkt+8; // 1 byte
char * protocol = ipPkt+9; // 1 byte
char * headercheck= ipPkt+10; // 2 bytes
#endif
char * srcAdr = ipPkt+12; // 4 bytes
char * dstAdr = ipPkt+16; // 4 bytes = total of 20 bytes
#ifndef SERIAL_PORT_MONITOR_NO
int versionIP = (version[0]>>4)&0xf;
int headerSizeIP = (ihl[0]&0xf)*4;
int dscpIP = (dscp[0]>>2)&0x3f;
int ecnIP = ecn[0]&3;
int packetLength = (pktLen[0]<<8)|pktLen[1]; // ip total packet length
int identIP = (ident[0]<<8)|ident[1];
int flagsIP = flags[0]>>14&3;
int ttlIP = ttl[0];
int protocolIP = protocol[0];
int checksumIP = (headercheck[0]<<8)|headercheck[1];
#endif
char srcIP [16];
snprintf(srcIP,16, "%d.%d.%d.%d", srcAdr[0],srcAdr[1],srcAdr[2],srcAdr[3]);
char dstIP [16];
snprintf(dstIP,16, "%d.%d.%d.%d", dstAdr[0],dstAdr[1],dstAdr[2],dstAdr[3]);
if (v0) {
debug("IP %s %s v%d h%d d%d e%d L%d ",srcIP,dstIP,versionIP,headerSizeIP,dscpIP,ecnIP,packetLength);
}
if (v0) {
debug("i%04x f%d t%d p%d C%04x\n",identIP,flagsIP,ttlIP,protocolIP,checksumIP);
}
dumpHeaderTCP();
dumpDataTCP();
tcpHandler();
}
void otherProtocol()
{
debug("Other IP protocol");
}
void IPframe()
{
int protocol = ppp.pkt.buf[13];
switch (protocol) {
case 1:
ICMPpacket();
break;
case 2:
IGMPpacket();
break;
case 17:
UDPpacket();
break;
case 6:
TCPpacket();
break;
default:
otherProtocol();
}
}
void LCPconfReq()
{
debug("LCP Config ");
if (ppp.pkt.buf[7] != 4) {
ppp.pkt.buf[4]=4; // allow only no options
debug("Reject\n");
sendFrame();
} else {
ppp.pkt.buf[4]=2; // ack zero conf
debug("Ack\n");
sendFrame();
debug("LCP Ask\n");
ppp.pkt.buf[4]=1; // request no options
sendFrame();
}
}
void LCPconfAck()
{
debug("LCP Ack\n");
}
void LCPend()
{
debug("LCP End\n");
ppp.online=0; // start hunting for connect string again
ppp.pkt.buf[4]=6;
sendFrame(); // acknowledge
}
void LCPother()
{
debug("LCP Other\n");
dumpFrame();
}
void LCPframe()
{
int code = ppp.pkt.buf[4];
switch (code) {
case 1:
LCPconfReq();
break; // config request
case 2:
LCPconfAck();
break; // config ack
case 5:
LCPend();
break; // end connection
default:
LCPother();
}
}
void discardedFrame()
{
if (v0) {
debug("Dropping frame %02x %02x %02x %02x\n", ppp.pkt.buf[0],ppp.pkt.buf[1],ppp.pkt.buf[2],ppp.pkt.buf[3]);
}
}
void determinePacketType()
{
if ( ppp.pkt.buf[0] != 0xff ) {
debug("byte0 != ff\n");
return;
}
if ( ppp.pkt.buf[1] != 3 ) {
debug("byte1 != 3\n");
return;
}
if ( ppp.pkt.buf[3] != 0x21 ) {
debug("byte2 != 21\n");
return;
}
int packetType = ppp.pkt.buf[2];
switch (packetType) {
case 0xc0:
LCPframe();
break; // link control
case 0x80:
IPCPframe();
break; // IP control
case 0x00:
IPframe();
break; // IP itself
default:
discardedFrame();
}
}
void wait_for_HDLC_frame()
{
while ( rxbufNotEmpty() ) {
int rx = pc_getBuf();
if (ppp.hdlc.frameBusy) {
if (rx==FRAME_7E) {
ppp.hdlc.frameBusy=0; // done gathering frame
if (ppp.rx.tail == 0) { // did we just wrap around?
ppp.hdlc.frameEndIndex=BUFLEN-1; // wrap back to end of buffer
} else {
ppp.hdlc.frameEndIndex=ppp.rx.tail-1; // remember where frame ends
}
processHDLCFrame(ppp.hdlc.frameStartIndex, ppp.hdlc.frameEndIndex);
}
} else {
if (rx==FRAME_7E) {
ppp.hdlc.frameBusy=1; // start gathering frame
ppp.hdlc.frameStartIndex=ppp.rx.tail; // remember where frame started
}
}
}
}
void scanForConnectString()
{
if ( ppp.online==0 ) {
char * clientFound = strstr( (char *)rxbufppp, "CLIENTCLIENT" ); // look for PC string
if( clientFound ) {
strcpy( clientFound, "FOUND!FOUND!" ); // overwrite so we don't find it again
pc.printf("CLIENTSERVER"); // respond to PC
ppp.online=1; // we can stop looking for the string
debug("Connect string found\n");
}
}
}
int main()
{
pc.baud(115200); // USB virtual serial port
#ifndef SERIAL_PORT_MONITOR_NO
xx.baud(115200); // second serial port for debug messages
xx.puts("\x1b[2J\x1b[HReady\n"); // VT100 code for clear screen & home
#endif
pppInitStruct(); // initialize all the PPP properties
pc.attach(&rxHandler,Serial::RxIrq); // start the receive handler
while(1) {
scanForConnectString(); // respond to connect command from windows dial up networking
wait_for_HDLC_frame();
}
}