#include "kni_utils.h"
#include <sys/ioctl.h>
#include <fcntl.h>
#include <net/if.h>
#include <linux/if_tun.h> 
#include <kni_tun.h>

struct kni_tun_handle{
    int fd;
    void *logger;
    enum kni_tun_mode mode;
};

void kni_tun_destroy(struct kni_tun_handle *tun_handle){
    if(tun_handle != NULL){
        close(tun_handle->fd);
        FREE(&tun_handle);
    }
}

struct kni_tun_handle* kni_tun_init(char *tun_name, enum kni_tun_mode mode, void *logger){
    struct kni_tun_handle *tun_handle = ALLOC(struct kni_tun_handle, 1);
    tun_handle->logger = logger;
    char *tun_path = (char*)"/dev/net/tun";
    struct ifreq ifr;
    memset(&ifr, 0, sizeof(ifr));
    int fd = -1, ret;
	ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_ONE_QUEUE;
    if(tun_name == NULL || *tun_name == '\0'){
        KNI_LOG_ERROR(logger, "Tap device name is NULL");
        goto error_out;
    }
    strncpy(ifr.ifr_name, tun_name, IFNAMSIZ);
    fd = open(tun_path, O_RDWR);
    if(fd < 0){
        KNI_LOG_ERROR(logger, "Failed at open file, filename = %s, errno = %d(%s)", tun_path, errno, strerror(errno));
        goto error_out;
    }
    tun_handle->fd = fd;
    tun_handle->mode = KNI_TUN_MODE_NOBLOCK;
    if(tun_handle->mode == KNI_TUN_MODE_NOBLOCK){
        int flags = fcntl(fd, F_GETFL, 0);
        ret = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
        if(ret < 0){
            KNI_LOG_ERROR(logger ,"Failed at fcntl, fd = %d, flags = F_GETFL | O_NONBLOCK, errno = %d(%s)", errno, strerror(errno));
            goto error_out;
        }
    }
    ret = ioctl(tun_handle->fd, TUNSETIFF, (void *)&ifr);
	if(ret < 0){
		KNI_LOG_ERROR(logger ,"Failed at ioctl, fd = %d, errno = %d(%s)", errno, strerror(errno));
		goto error_out;
	}
    return tun_handle;

error_out:
    kni_tun_destroy(tun_handle);
    return NULL;
}


int kni_tun_write(struct kni_tun_handle *handle, char *buff, uint16_t buff_len){
	uint16_t ret = write(handle->fd, buff, buff_len);
	if(ret < 0){
        KNI_LOG_ERROR(handle->logger, "Failed at write, errno = %d(%s)", errno, strerror(errno));
        return -1;
	}
    if(ret < buff_len){
        KNI_LOG_ERROR(handle->logger, "Failed at write: need send %dB, only send %dB", buff_len, ret);
        return -1;
    }
	return 0;
}

/*
*   >= 0 : read data length
*   = -1 : error
*/
int kni_tun_read(struct kni_tun_handle *handle, char *buff, uint16_t buff_len){
    int ret = 0;
	ret = read(handle->fd, buff, buff_len);
	if(ret < 0){
        if(ret == -1 && handle->mode == KNI_TUN_MODE_NOBLOCK){
            if(errno == EWOULDBLOCK || errno == EAGAIN){
                return 0;
            }
        }
        KNI_LOG_ERROR(handle -> logger, "Failed at read, error = %d(%s)", errno, strerror(errno));
	}
	return ret;
}