ZealOS/src/Home/Net/ICMP.CC

#include "IPV4"

#define ICMP_TYPE_ECHO_REPLY	0
#define ICMP_TYPE_ECHO_REQUEST	8

class CICMPHeader // Shrine's use of id and seq indicate this header is for Address Mask Reply/Request
{
	U8 type;
	U8 code;
	U16 checksum;

	U16 identifier;
	U16 sequence_number;
};


I64 ICMPSendReply(U32 destination_ip_address,
					U16 identifier,
					U16 sequence_number,
					U16 request_checksum,
					U8 *payload,
					I64 length)
{
	U8 *frame;
	I64 de_index;
	CICMPHeader *header;

	de_index = IPV4PacketAllocate(&frame,
									IP_PROTOCOL_ICMP,
									IPV4GetAddress(),
									destination_ip_address,
									sizeof(CICMPHeader) + length);
	if (de_index < 0)
	{
		ZenithLog("ICMP Send Reply failed to allocate IPV4 packet.\n");
		return de_index;
	}

	header = frame;


	header->type = ICMP_TYPE_ECHO_REPLY;

	header->code = 0; // why is 0 okay?

	header->checksum = EndianU16(EndianU16(request_checksum) + 0x0800);// this is awful. Shrine says hack alert.

	header->identifier = identifier;

	header->sequence_number = sequence_number;

	MemCopy(frame + sizeof(CICMPHeader), payload, length);

	IPV4PacketFinish(de_index);
	//return IPV4PacketFinish
}

I64 ICMPHandler(CIPV4Packet *packet)
{
	CICMPHeader *header;

	if (packet->length < sizeof(CICMPHeader))
	{
		ZenithLog("ICMP Handler caught wrong IPV4 length.\n");
		return -1;
	}

	header = packet->data;

	if (header->type == ICMP_TYPE_ECHO_REQUEST && header->code == 0)//why zero? need more #defines in here
	{
		ARPCachePut(packet->source_ip_address, packet->ethernet_frame->source_address);

		ICMPSendReply(packet->source_ip_address,
						header->identifier,
						header->sequence_number,
						header->checksum,
						packet->data + sizeof(CICMPHeader),
						packet->length - sizeof(CICMPHeader)); // wut
	}

	return 0;
}