On 2023/12/7 14:00, Jason Wang wrote:
> On Tue, Dec 5, 2023 at 7:35 PM Yunsheng Lin <linyunsheng@xxxxxxxxxx> wrote:
...
>> +
>> +static int tun_alloc(void)
>> +{
>> + struct ifreq ifr;
>> + int fd, e;
>> +
>> + fd = open("/dev/net/tun", O_RDWR);
>> + if (fd < 0) {
>> + perror("Cannot open /dev/net/tun");
>> + return fd;
>> + }
>> +
>> + memset(&ifr, 0, sizeof(ifr));
>> +
>> + ifr.ifr_flags = IFF_TUN | IFF_NO_PI;
>
> Why did you use IFF_TUN but not IFF_TAP here?
To be honest, no particular reason, I just picked IFF_TUN and it happened
to work for me to test changing in vhost_net_build_xdp().
Is there a particular reason you perfer the IFF_TAP over IFF_TUN?
>
>> + strncpy(ifr.ifr_name, "tun0", IFNAMSIZ);
>
> tun0 is pretty common if there's a VPN. Do we need some randomized name here?
How about something like below?
snprintf(ifr.ifr_name, IFNAMSIZ, "tun_%d", getpid());
>
>
>> +
>> + e = ioctl(fd, TUNSETIFF, (void *) &ifr);
>> + if (e < 0) {
>> + perror("ioctl[TUNSETIFF]");
>> + close(fd);
>> + return e;
>> + }
>> +
>> + return fd;
>> +}
>> +
>> +/* Unused */
>> +void *__kmalloc_fake, *__kfree_ignore_start, *__kfree_ignore_end;
>
> Why do we need trick like these here?
That is because of the below error:
tools/virtio/./linux/kernel.h:58: undefined reference to `__kmalloc_fake'
when virtio_ring.c is compiled in the userspace, the kmalloc raleted function
is implemented in tools/virtio/./linux/kernel.h, which requires those varibles
to be defined.
>
>> +
>> +struct vq_info {
>> + int kick;
>> + int call;
>> + int num;
>> + int idx;
>> + void *ring;
>> + /* copy used for control */
>> + struct vring vring;
>> + struct virtqueue *vq;
>> +};
>> +
>> +struct vdev_info {
>> + struct virtio_device vdev;
>> + int control;
>> + struct pollfd fds[1];
>> + struct vq_info vqs[1];
>> + int nvqs;
>> + void *buf;
>> + size_t buf_size;
>> + struct vhost_memory *mem;
>> +};
>> +
>> +static struct vhost_vring_file no_backend = { .index = 1, .fd = -1 },
>> + backend = { .index = 1, .fd = 1 };
>
> A magic number like fd = 1 is pretty confusing.
>
> And I don't see why we need global variables here.
I was using the virtio_test.c as reference, will try to remove it
if it is possible.
>
>> +static const struct vhost_vring_state null_state = {};
>> +
..
>> +
>> +done:
>> + backend.fd = tun_alloc();
>> + assert(backend.fd >= 0);
>> + vdev_info_init(&dev, features);
>> + vq_info_add(&dev, 256);
>> + run_test(&dev, &dev.vqs[0], delayed, batch, reset, nbufs);
>
> I'd expect we are testing some basic traffic here. E.g can we use a
> packet socket then we can test both tx and rx?
Yes, only rx for tun is tested.
Do you have an idea how to test the tx too? As I am not familar enough
with vhost_net and tun yet.
>
> Thanks
