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

[Randy Li]

On 2024/7/31 22:12, Willem de Bruijn wrote:
> Randy Li wrote:
> > We need the queue index in qdisc mapping rule. There is no way to
> > fetch that.
> In which command exactly?

That is for sch_multiq, here is an example

tc qdisc add dev  tun0 root handle 1: multiq

tc filter add dev tun0 parent 1: protocol ip prio 1 u32 match ip dst 
172.16.10.1 action skbedit queue_mapping 0
tc filter add dev tun0 parent 1: protocol ip prio 1 u32 match ip dst 
172.16.10.20 action skbedit queue_mapping 1

tc filter add dev tun0 parent 1: protocol ip prio 1 u32 match ip dst 
172.16.10.10 action skbedit queue_mapping 2


The purpose here is taking advantage of the multiple threads. For the 
the server side(gateway of the tunnel's subnet), usually a different 
peer would invoked a different encryption/decryption key pair, it would 
be better to handle each in its own thread. Or the application would 
need to implement a dispatcher here.


I am newbie to the tc(8), I verified the command above with a tun type 
multiple threads demo. But I don't know how to drop the unwanted ingress 
filter here, the queue 0 may be a little broken.

> > Signed-off-by: Randy Li <ayaka@xxxxxxxxxxx>
> > ---
> >   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
Sorry, I didn't verify the tap type.
> > +		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.
Would fix in v2.
> >   	}
> >   
> >   	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