tun: Add ability to create tun device with given index

Tun devices cannot be created with ifidex user wants, but it's
required by checkpoint-restore project.

Long time ago such ability was implemented for rtnl_ops-based
interface for creating links (9c7dafbf net: Allow to create links
with given ifindex), but the only API for creating and managing
tuntap devices is ioctl-based and is evolving with adding new ones
(cde8b15f tuntap: add ioctl to attach or detach a file form tuntap
device).

Following that trend, here's how a new ioctl that sets the ifindex
for device, that _will_ be created by TUNSETIFF ioctl looks like.
So those who want a tuntap device with the ifindex N, should open
the tun device, call ioctl(fd, TUNSETIFINDEX, &N), then call TUNSETIFF.
If the index N is busy, then the register_netdev will find this out
and the ioctl would be failed with -EBUSY.

If setifindex is not called, then it will be generated as before.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 7ed13cc0dcb2d3577c3ce38e756afa63838d23f1..4b65fbcc490f3da34f981b2dff763ffeb682954f 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -138,7 +138,10 @@ struct tun_file {
        struct fasync_struct *fasync;
        /* only used for fasnyc */
        unsigned int flags;
-       u16 queue_index;
+       union {
+               u16 queue_index;
+               unsigned int ifindex;
+       };
        struct list_head next;
        struct tun_struct *detached;
 };
@@ -1601,6 +1604,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 
                dev_net_set(dev, net);
                dev->rtnl_link_ops = &tun_link_ops;
+               dev->ifindex = tfile->ifindex;
 
                tun = netdev_priv(dev);
                tun->dev = dev;
@@ -1817,6 +1821,7 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
        kgid_t group;
        int sndbuf;
        int vnet_hdr_sz;
+       unsigned int ifindex;
        int ret;
 
        if (cmd == TUNSETIFF || cmd == TUNSETQUEUE || _IOC_TYPE(cmd) == 0x89) {
@@ -1851,6 +1856,19 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
                        ret = -EFAULT;
                goto unlock;
        }
+       if (cmd == TUNSETIFINDEX) {
+               ret = -EPERM;
+               if (tun)
+                       goto unlock;
+
+               ret = -EFAULT;
+               if (copy_from_user(&ifindex, argp, sizeof(ifindex)))
+                       goto unlock;
+
+               ret = 0;
+               tfile->ifindex = ifindex;
+               goto unlock;
+       }
 
        ret = -EBADFD;
        if (!tun)
@@ -2099,6 +2117,7 @@ static int tun_chr_open(struct inode *inode, struct file * file)
        rcu_assign_pointer(tfile->tun, NULL);
        tfile->net = get_net(current->nsproxy->net_ns);
        tfile->flags = 0;
+       tfile->ifindex = 0;
 
        rcu_assign_pointer(tfile->socket.wq, &tfile->wq);
        init_waitqueue_head(&tfile->wq.wait);

diff --git a/include/uapi/linux/if_tun.h b/include/uapi/linux/if_tun.h
index 1870ee29bb37bf84ee9fda20b9d3c3c9b5a8b430..c58d023c48225600956f12e5a4ec13f846553f2c 100644 (file)
--- a/include/uapi/linux/if_tun.h
+++ b/include/uapi/linux/if_tun.h
@@ -56,6 +56,7 @@
 #define TUNGETVNETHDRSZ _IOR('T', 215, int)
 #define TUNSETVNETHDRSZ _IOW('T', 216, int)
 #define TUNSETQUEUE  _IOW('T', 217, int)
+#define TUNSETIFINDEX  _IOW('T', 218, unsigned int)
 
 /* TUNSETIFF ifr flags */
 #define IFF_TUN                0x0001