File content as of revision 170:3d3b2126181c:

/// ppp-blinky.h

#include "mbed.h"
#include "sha1.h"
#include "BufferedSerial.h"

void initializePpp();
int connectedPpp();
void waitForPcConnectString();
void waitForPppFrame();
void determinePacketType();

/// PPP header
typedef struct { // [ff 03 00 21]
    unsigned int address : 8;  // always 0xff
    unsigned int control : 8;  // always 03
    unsigned int protocolR : 16; // byte reversed, 0x0021 for ip
} pppHeaderType;

/// LCP and IPCP header
typedef struct {
    // ppp part
    unsigned int address : 8;  // always 0xff
    unsigned int control : 8;  // always 03
    unsigned int protocolR : 16; // byte reversed, 0x0021 for ip

    // ipcp and lcp part
    unsigned int code : 8; // IPCP and LCP contain a code field which identifies the requested action or response
    unsigned int identifier : 8 ;
    unsigned int lengthR : 16;
} ipcpHeaderType;

/// IP header
typedef struct {
    unsigned int headerLength   :  4;  // ip headerlength / 4
    unsigned int version        :  4;  // ip version number
    unsigned int ect            :  1;  // ecn capable transport
    unsigned int ce             :  1;  // ecn-ce
    unsigned int dscp           :  6;  // differentiated services
    unsigned int lengthR        : 16;  // ip packet length (byte-reversed)

    unsigned int identR         : 16;  // ident, byte reversed
    unsigned int fragmentOffsHi :  5;
    unsigned int lastFragment   :  1;
    unsigned int dontFragment   :  1;
    unsigned int reservedIP     :  1;
    unsigned int fragmentOffsLo :  8;

    unsigned int ttl            :  8;
    unsigned int protocol       :  8;  // next protocol
    unsigned int checksumR      : 16;  // ip checksum, byte reversed
    union {
        unsigned int srcAdrR; // source IP address
        char srcAdrPtr [0]; // so we also have a char * to srcAdrR
    };
    union {
        unsigned int dstAdrR; // destination IP address
        char dstAdrPtr [0];  // so we also have a char * to dstAdrR
    };
} ipHeaderType;

/// IP pseudoheader. Used in TCP/UDP checksum calculations.
typedef struct {
    union {
        char start [0]; // a char * to avoid type conversions
        unsigned int srcAdrR; // source IP address
    };
    unsigned int dstAdrR; // destination IP address
    unsigned int zero     :  8;
    unsigned int protocol :  8;
    unsigned int lengthR  : 16; // byte reversed
} pseudoIpHeaderType;

/// TCP header
typedef struct {
    unsigned int    srcPortR : 16; // byte reversed
    unsigned int    dstPortR : 16; // byte reversed
    unsigned int    seqTcpR;      // byte reversed
    unsigned int    ackTcpR;      // byte reversed
    unsigned int resvd1  : 4;  // reserved
    unsigned int offset  : 4; // tcp header length [5..15]
    union {
        unsigned char All;  // all 8 flag bits
        struct {            // individual flag bits
            unsigned char fin:  1, // fin
                     syn    :  1, // syn
                     rst    :  1, // rst
                     psh    :  1, // psh
                     ack    :  1, // ack
                     urg    :  1, // urg
                     ece    :  1, // ece
                     cwr    :  1; // cwr
        };
    } flag;
    unsigned int windowR : 16; // byte reversed
    unsigned int    checksumR : 16; // byte reversed
    unsigned int    urgentPointerR : 16; // byte reversed;
    unsigned int    tcpOptions[10]; // up to 10 words of options possible
} tcpHeaderType;

/// UDP header.
typedef struct {
    unsigned int srcPortR  : 16; // byte reversed
    unsigned int dstPortR  : 16; // byte reversed
    unsigned int lengthR   : 16; // byte reversed
    unsigned int checksumR : 16; // byte reversed
    char data [0]; // data area
} udpHeaderType;

/// ICMP header.
typedef struct {
    unsigned int type : 8;
    unsigned int code : 8;
    unsigned int checkSumR : 16; // byte reversed
    unsigned int idR : 16; // byte reversed
    unsigned int sequenceR : 16; // byte reversed
    char data [0]; // data area
} icmpHeaderType;