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#pragma once
#include <algorithm>
#include <array>
#include <cstdint>
#include <optional>
#include <span>
#include "wireframe/byteio.hpp"
namespace wireframe::net {
inline constexpr std::uint8_t kProtoIcmp = 1;
inline constexpr std::uint8_t kProtoTcp = 6;
inline constexpr std::uint8_t kProtoUdp = 17;
struct Ipv4Address {
std::array<unsigned char, 4> bytes;
};
struct Ipv4Header {
std::uint8_t version;
std::uint8_t ihl; // header length in 32-bit words
std::uint16_t total_length;
std::uint8_t ttl;
std::uint8_t protocol;
Ipv4Address src;
Ipv4Address dst;
};
struct Ipv4Packet {
Ipv4Header header;
std::span<const unsigned char> payload;
};
inline std::optional<Ipv4Packet> parse_ipv4(std::span<const unsigned char> bytes) {
if (bytes.size() < 20) return std::nullopt;
std::uint8_t version = static_cast<std::uint8_t>(bytes[0] >> 4);
std::uint8_t ihl = bytes[0] & 0x0F;
std::size_t header_len = static_cast<std::size_t>(ihl) * 4;
if (version != 4 || header_len < 20 || bytes.size() < header_len) return std::nullopt;
Ipv4Header header{};
header.version = version;
header.ihl = ihl;
header.total_length = read_be16(bytes, 2);
header.ttl = bytes[8];
header.protocol = bytes[9];
std::copy_n(bytes.begin() + 12, 4, header.src.bytes.begin());
std::copy_n(bytes.begin() + 16, 4, header.dst.bytes.begin());
return Ipv4Packet{header, bytes.subspan(header_len)};
}
} // namespace wireframe::net
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