// icmp_proxy.h — ICMP echo (ping) прокси: client ↔ exit через etcp_router
#ifndef ICMP_PROXY_H
#define ICMP_PROXY_H

#include <stdint.h>
#include "../lib/socket_compat.h"

struct UTUN_INSTANCE;
struct UASYNC;
struct ll_entry;
struct ETCP_CONN;

// Sub-commands
#define ICMP_PROXY_SUBCMD_REQUEST 0x01  // client→exit: пингани dst_ip
#define ICMP_PROXY_SUBCMD_REPLY   0x02  // exit→client: echo reply

// Message header (excluding svc_id byte)
// svc_id(1) + subcmd(1) + sender_node_id(8) + dst_ip(4) + orig_src_ip(4) + icmp_id(2) + icmp_seq(2) + payload
#define ICMP_PROXY_HDR_SIZE       22

// In-flight ICMP echo request (exit node side)
struct icmp_request {
    struct icmp_request* next;
    uint64_t client_node_id;
    uint32_t dst_ip;
    uint32_t orig_src_ip;    // IP исходного отправителя (чтобы вернуть reply правильному адресату)
    uint16_t echo_id;
    uint16_t echo_seq;
    uint8_t  payload[1500];
    size_t   payload_len;
    uint64_t sent_tb;
    socket_t sock;         // raw socket (only if we use per-request)
};

struct icmp_proxy_ctx {
    int          initialized;
    int          is_exit;
    struct UTUN_INSTANCE* inst;
    struct UASYNC* ua;
    socket_t     raw_sock;        // one SOCK_RAW for all ICMP on exit
    void*        raw_read_id;
    struct icmp_request* pending;
    uint64_t     request_timeout_tb;
    int          test_loopback;    // 1 = virtual loopback when no raw socket (test only)
};

int icmp_proxy_init(struct UTUN_INSTANCE* inst, struct UASYNC* ua);
void icmp_proxy_destroy(struct UTUN_INSTANCE* inst);

// Unified etcp_router callback
void icmp_proxy_recv_cb(struct ETCP_CONN* conn, struct ll_entry* entry);

// Client side: принять IP/ICMP echo request с TUN, отправить через etcp
int icmp_proxy_send_to_exit(struct UTUN_INSTANCE* inst, uint64_t exit_node_id,
                            uint32_t dst_ip, uint32_t orig_src_ip, uint16_t echo_id, uint16_t echo_seq,
                            const uint8_t* payload, size_t payload_len);

int icmp_proxy_deliver_reply(struct UTUN_INSTANCE* inst,
                             uint32_t dst_ip, uint32_t src_ip, uint16_t echo_id, uint16_t echo_seq,
                             const uint8_t* payload, size_t payload_len);

void icmp_proxy_set_test_loopback(struct UTUN_INSTANCE* inst, int enabled);

#endif // ICMP_PROXY_H