limen/icmp/icmp.h

#pragma once
#include <cstdint>
#include <span>
#include "eth.h"
#include "ipv4.h"
#include "span_writer.h"

namespace icmp {

struct __attribute__((packed)) echo {
    uint8_t type;
    uint8_t code;
    uint16_t checksum;
    uint16_t id;
    uint16_t seq;
};
static_assert(sizeof(echo) == 8);

void init();
void handle(std::span<const uint8_t> frame, span_writer& tx);

template <typename Buf>
void prepend_echo_request(Buf& buf,
                          eth::mac_addr src_mac, ipv4::ip4_addr src_ip,
                          eth::mac_addr dst_mac, ipv4::ip4_addr dst_ip,
                          uint16_t id, uint16_t seq,
                          size_t payload_len = 0) {
    auto* e = buf.template prepend<echo>();
    e->type = 8;
    e->code = 0;
    e->checksum = 0;
    e->id = id;
    e->seq = seq;
    size_t icmp_len = sizeof(echo) + payload_len;
    e->checksum = ipv4::checksum(e, icmp_len);
    ipv4::prepend(buf, dst_mac, src_mac, src_ip, dst_ip, 1, icmp_len);
}

bool parse_echo_reply(std::span<const uint8_t> frame, ipv4::ip4_addr& src_ip, uint16_t expected_id);

} // namespace icmp