tuntap: add ioctl to attach or detach a file form tuntap device

Sometimes usespace may need to active/deactive a queue, this could be done by
detaching and attaching a file from tuntap device.

This patch introduces a new ioctls - TUNSETQUEUE which could be used to do
this. Flag IFF_ATTACH_QUEUE were introduced to do attaching while
IFF_DETACH_QUEUE were introduced to do the detaching.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 48 insertions, 8 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 2762c55aeb66..79b6f9ecc12c 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -195,6 +195,15 @@ static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb)
         return txq;
 }
 
+static inline bool tun_not_capable(struct tun_struct *tun)
+{
+        const struct cred *cred = current_cred();
+
+        return ((uid_valid(tun->owner) && !uid_eq(cred->euid, tun->owner)) ||
+                  (gid_valid(tun->group) && !in_egroup_p(tun->group))) &&
+                !capable(CAP_NET_ADMIN);
+}
+
 static void tun_set_real_num_queues(struct tun_struct *tun)
 {
         netif_set_real_num_tx_queues(tun->dev, tun->numqueues);
@@ -1310,8 +1319,6 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 
         dev = __dev_get_by_name(net, ifr->ifr_name);
         if (dev) {
-                const struct cred *cred = current_cred();
-
                 if (ifr->ifr_flags & IFF_TUN_EXCL)
                         return -EBUSY;
                 if ((ifr->ifr_flags & IFF_TUN) && dev->netdev_ops == &tun_netdev_ops)
@@ -1321,9 +1328,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
                 else
                         return -EINVAL;
 
-                if (((uid_valid(tun->owner) && !uid_eq(cred->euid, tun->owner)) ||
-                     (gid_valid(tun->group) && !in_egroup_p(tun->group))) &&
-                    !capable(CAP_NET_ADMIN))
+                if (tun_not_capable(tun))
                         return -EPERM;
                 err = security_tun_dev_attach(tfile->socket.sk);
                 if (err < 0)
@@ -1530,6 +1535,40 @@ static void tun_set_sndbuf(struct tun_struct *tun)
         }
 }
 
+static int tun_set_queue(struct file *file, struct ifreq *ifr)
+{
+        struct tun_file *tfile = file->private_data;
+        struct tun_struct *tun;
+        struct net_device *dev;
+        int ret = 0;
+
+        rtnl_lock();
+
+        if (ifr->ifr_flags & IFF_ATTACH_QUEUE) {
+                dev = __dev_get_by_name(tfile->net, ifr->ifr_name);
+                if (!dev) {
+                        ret = -EINVAL;
+                        goto unlock;
+                }
+
+                tun = netdev_priv(dev);
+                if (dev->netdev_ops != &tap_netdev_ops &&
+                        dev->netdev_ops != &tun_netdev_ops)
+                        ret = -EINVAL;
+                else if (tun_not_capable(tun))
+                        ret = -EPERM;
+                else
+                        ret = tun_attach(tun, file);
+        } else if (ifr->ifr_flags & IFF_DETACH_QUEUE)
+                __tun_detach(tfile, false);
+        else
+                ret = -EINVAL;
+
+unlock:
+        rtnl_unlock();
+        return ret;
+}
+
 static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
                             unsigned long arg, int ifreq_len)
 {
@@ -1543,7 +1582,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
         int vnet_hdr_sz;
         int ret;
 
-        if (cmd == TUNSETIFF || _IOC_TYPE(cmd) == 0x89) {
+        if (cmd == TUNSETIFF || cmd == TUNSETQUEUE || _IOC_TYPE(cmd) == 0x89) {
                 if (copy_from_user(&ifr, argp, ifreq_len))
                         return -EFAULT;
         } else {
@@ -1554,9 +1593,10 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
                  * This is needed because we never checked for invalid flags on
                  * TUNSETIFF. */
                 return put_user(IFF_TUN | IFF_TAP | IFF_NO_PI | IFF_ONE_QUEUE |
-                                IFF_VNET_HDR,
+                                IFF_VNET_HDR | IFF_MULTI_QUEUE,
                                 (unsigned int __user*)argp);
-        }
+        } else if (cmd == TUNSETQUEUE)
+                return tun_set_queue(file, &ifr);
 
         ret = 0;
         rtnl_lock();