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#pragma once
#include <stdint.h>
#define IP_HEADER_SIZE 40
#define MIN_MTU 576
#define MAX_IP_PACKET_SIZE 65535
#define MAX_DATAGRAM_SIZE (MAX_IP_PACKET_SIZE - IP_HEADER_SIZE)
#define ICMP_PAYLOAD_OFFSET 8
struct __attribute__((packed)) icmp_echo {
uint8_t type;
uint8_t code;
uint16_t checksum;
uint16_t id;
uint16_t seqnum;
uint8_t payload[MAX_DATAGRAM_SIZE - ICMP_PAYLOAD_OFFSET];
};
#define ICMP_MAX_PAYLOAD_LENGTH (MAX_DATAGRAM_SIZE - ICMP_PAYLOAD_OFFSET)
#define ICMP_SAFE_PAYLOAD_LENGTH (MIN_MTU - IP_HEADER_SIZE - ICMP_PAYLOAD_OFFSET)
struct icmp_reply {
const uint8_t *data; // points to internal buffer
size_t length; // length of 'data'
int seqnum;
};
// Returns -1 on error with errno.
int icmp_open_socket(void);
// Only actual IPv4 addresses allowed. Sends data in 'data' with length 'length', and
// returns pointer to internal buffer with reply data. Buffer is invalidated on next
// call to the function.
// Returns {.data=NULL} on error with errno.
struct icmp_reply icmp_communicate(int sock, const char *ip_address, int seqnum, const void *data, size_t length);
// Returns -1 on error with errno.
int icmp_send_echo_reply(const char *ip_address, int id, int seqnum, const void *data, size_t length);
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