//
//  ICMPHeader.h
//  GBPing
//
//  Created by Luka Mirosevic on 15/11/2012.
//  Copyright (c) 2012 Goonbee. All rights reserved.
//

#ifndef GBPing_ICMPHeader_h
#define GBPing_ICMPHeader_h

#include <AssertMacros.h>

#pragma mark - IP and ICMP On-The-Wire Format

// The following declarations specify the structure of ping packets on the wire.

// IP header structure:

struct IPHeader {
    uint8_t versionAndHeaderLength;
    uint8_t differentiatedServices;
    uint16_t totalLength;
    uint16_t identification;
    uint16_t flagsAndFragmentOffset;
    uint8_t timeToLive;
    uint8_t protocol;
    uint16_t headerChecksum;
    uint8_t sourceAddress[4];
    uint8_t destinationAddress[4];
    // options...
    // data...
};
typedef struct IPHeader IPHeader;

__Check_Compile_Time(sizeof(IPHeader) == 20);
__Check_Compile_Time(offsetof(IPHeader, versionAndHeaderLength) == 0);
__Check_Compile_Time(offsetof(IPHeader, differentiatedServices) == 1);
__Check_Compile_Time(offsetof(IPHeader, totalLength) == 2);
__Check_Compile_Time(offsetof(IPHeader, identification) == 4);
__Check_Compile_Time(offsetof(IPHeader, flagsAndFragmentOffset) == 6);
__Check_Compile_Time(offsetof(IPHeader, timeToLive) == 8);
__Check_Compile_Time(offsetof(IPHeader, protocol) == 9);
__Check_Compile_Time(offsetof(IPHeader, headerChecksum) == 10);
__Check_Compile_Time(offsetof(IPHeader, sourceAddress) == 12);
__Check_Compile_Time(offsetof(IPHeader, destinationAddress) == 16);

// ICMP type and code combinations:

enum {
    kICMPv4TypeEchoRequest = 8,
    kICMPv4TypeEchoReply   = 0
};

enum {
    kICMPv6TypeEchoRequest = 128,
    kICMPv6TypeEchoReply   = 129
};

// ICMP header structure:

struct ICMPHeader {
    uint8_t type;
    uint8_t code;
    uint16_t checksum;
    uint16_t identifier;
    uint16_t sequenceNumber;
    // data...
};
typedef struct ICMPHeader ICMPHeader;

__Check_Compile_Time(sizeof(ICMPHeader) == 8);
__Check_Compile_Time(offsetof(ICMPHeader, type) == 0);
__Check_Compile_Time(offsetof(ICMPHeader, code) == 1);
__Check_Compile_Time(offsetof(ICMPHeader, checksum) == 2);
__Check_Compile_Time(offsetof(ICMPHeader, identifier) == 4);
__Check_Compile_Time(offsetof(ICMPHeader, sequenceNumber) == 6);

#endif