netdev - Re: [PATCH] net: tuntap: add ioctl() TUNGETQUEUEINDX to fetch queue index

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Message-ID: <66aa463e6bcdf_20b4e4294ea@willemb.c.googlers.com.notmuch>
Date: Wed, 31 Jul 2024 10:12:14 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Randy Li <ayaka@...lik.info>, 
 netdev@...r.kernel.org
Cc: willemdebruijn.kernel@...il.com, 
 jasowang@...hat.com, 
 davem@...emloft.net, 
 edumazet@...gle.com, 
 kuba@...nel.org, 
 pabeni@...hat.com, 
 linux-kernel@...r.kernel.org, 
 Randy Li <ayaka@...lik.info>
Subject: Re: [PATCH] net: tuntap: add ioctl() TUNGETQUEUEINDX to fetch queue
 index

Randy Li wrote:
> We need the queue index in qdisc mapping rule. There is no way to
> fetch that.

In which command exactly?

> Signed-off-by: Randy Li <ayaka@...lik.info>
> ---
>  drivers/net/tap.c           | 9 +++++++++
>  drivers/net/tun.c           | 4 ++++
>  include/uapi/linux/if_tun.h | 1 +
>  3 files changed, 14 insertions(+)
> 
> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
> index 77574f7a3bd4..6099f27a0a1f 100644
> --- a/drivers/net/tap.c
> +++ b/drivers/net/tap.c
> @@ -1120,6 +1120,15 @@ static long tap_ioctl(struct file *file, unsigned int cmd,
>  		rtnl_unlock();
>  		return ret;
>  
> +	case TUNGETQUEUEINDEX:
> +		rtnl_lock();
> +		if (!q->enabled)
> +			ret = -EINVAL;
> +

Below will just overwrite the above ret

> +		ret = put_user(q->queue_index, up);
> +		rtnl_unlock();
> +		return ret;
> +
>  	case SIOCGIFHWADDR:
>  		rtnl_lock();
>  		tap = tap_get_tap_dev(q);
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 1d06c560c5e6..5473a0fca2e1 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -3115,6 +3115,10 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
>  		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
>  			return -EPERM;
>  		return open_related_ns(&net->ns, get_net_ns);
> +	} else if (cmd == TUNGETQUEUEINDEX) {
> +		if (tfile->detached)
> +			return -EINVAL;
> +		return put_user(tfile->queue_index, (unsigned int __user*)argp);

Unless you're certain that these fields can be read without RTNL, move
below rtnl_lock() statement.

>  	}
>  
>  	rtnl_lock();
> diff --git a/include/uapi/linux/if_tun.h b/include/uapi/linux/if_tun.h
> index 287cdc81c939..2668ca3b06a5 100644
> --- a/include/uapi/linux/if_tun.h
> +++ b/include/uapi/linux/if_tun.h
> @@ -61,6 +61,7 @@
>  #define TUNSETFILTEREBPF _IOR('T', 225, int)
>  #define TUNSETCARRIER _IOW('T', 226, int)
>  #define TUNGETDEVNETNS _IO('T', 227)
> +#define TUNGETQUEUEINDEX _IOR('T', 228, unsigned int)
>  
>  /* TUNSETIFF ifr flags */
>  #define IFF_TUN		0x0001
> -- 
> 2.45.2
>