Re: [PATCH] tap-linux: Open ipvtap and macvtap

[Jason Wang <jasowang@redhat.com>]

On Tue, Oct 8, 2024 at 2:52 PM Akihiko Odaki <akihiko.odaki@daynix.com> wrote:
>
> ipvtap and macvtap create a file for each interface unlike tuntap, which
> creates one file shared by all interfaces. Try to open a file dedicated
> to the interface first for ipvtap and macvtap.
>

Management layers usually pass these fds via SCM_RIGHTS. Is this for
testing purposes? (Note that we can use something like -netdev
tap,fd=10 10<>/dev/tap0).

> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> ---
>  net/tap-linux.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/net/tap-linux.c b/net/tap-linux.c
> index 1226d5fda2d9..22ec2f45d2b7 100644
> --- a/net/tap-linux.c
> +++ b/net/tap-linux.c
> @@ -45,10 +45,21 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
>      int len = sizeof(struct virtio_net_hdr);
>      unsigned int features;
>
> -    fd = RETRY_ON_EINTR(open(PATH_NET_TUN, O_RDWR));
> +
> +    ret = if_nametoindex(ifname);
> +    if (ret) {
> +        g_autofree char *file = g_strdup_printf("/dev/tap%d", ret);
> +        fd = open(file, O_RDWR);
> +    } else {
> +        fd = -1;
> +    }
> +
>      if (fd < 0) {
> -        error_setg_errno(errp, errno, "could not open %s", PATH_NET_TUN);
> -        return -1;
> +        fd = RETRY_ON_EINTR(open(PATH_NET_TUN, O_RDWR));

Any reason tuntap were tried after the macvtap/ipvtap?

> +        if (fd < 0) {
> +            error_setg_errno(errp, errno, "could not open %s", PATH_NET_TUN);
> +            return -1;
> +        }
>      }
>      memset(&ifr, 0, sizeof(ifr));
>      ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
>
> ---
> base-commit: 31669121a01a14732f57c49400bc239cf9fd505f
> change-id: 20241008-macvtap-b152e5abb457
>
> Best regards,
> --
> Akihiko Odaki <akihiko.odaki@daynix.com>

Thanks

>