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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>
This commit is contained in:
Pavel Emelyanov 2013-08-21 14:31:38 +04:00 committed by David S. Miller
parent 5f1cd200c4
commit fb7589a162
2 changed files with 21 additions and 1 deletions
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21
drivers/net/tun.c
View File

@ -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);

1
include/uapi/linux/if_tun.h
View File

@ -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