utun2/!/test_virtual_tun.h

#ifndef TEST_VIRTUAL_TUN_H
#define TEST_VIRTUAL_TUN_H

#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>
#include <sys/types.h>

#define VIRTUAL_TUN_MAX_PACKET_SIZE 65536

struct virtual_tun {
    int read_pipe[2];   // [0] = read end, [1] = write end  
    int write_pipe[2];  // [0] = read end, [1] = write end
    char ifname[32];    // Virtual interface name
    bool enabled;
    void* test_context; // For callbacks
    
    // Statistics
    struct {
        size_t packets_sent;
        size_t packets_received;
        size_t bytes_sent;
        size_t bytes_received;
    } stats;
};

// Create virtual TUN with bidirectional pipes
struct virtual_tun* virtual_tun_create(const char* ifname);

// Cleanup virtual TUN
void virtual_tun_destroy(struct virtual_tun* vtun);

// Get file descriptor for reading (simulates TUN device)
int virtual_tun_get_read_fd(struct virtual_tun* vtun);

// Get file descriptor for writing (simulates TUN device)
int virtual_tun_get_write_fd(struct virtual_tun* vtun);

// Inject packet into virtual TUN (simulates packet from network)
int virtual_tun_inject_packet(struct virtual_tun* vtun, const uint8_t* packet, size_t len);

// Read packet from virtual TUN (captures packets going to network)
ssize_t virtual_tun_read_packet(struct virtual_tun* vtun, uint8_t* buffer, size_t max_len);

// Write packet to virtual TUN (sends packet to network)
ssize_t virtual_tun_write_packet(struct virtual_tun* vtun, const uint8_t* packet, size_t len);

// Get virtual TUN statistics
void virtual_tun_get_stats(struct virtual_tun* vtun, size_t* packets_sent, size_t* packets_received,
                          size_t* bytes_sent, size_t* bytes_received);

// Reset virtual TUN statistics
void virtual_tun_reset_stats(struct virtual_tun* vtun);

#endif // TEST_VIRTUAL_TUN_H