Commit c8d68e6be1c3b242f1c598595830890b65cea64a removed carrier off call from tun_detach since it's now called on queue disable and not only on tun close. This confuses userspace which used this flag to detect a free tun. To fix, move on/off calls to setiff/close respectively.
Signed-off-by: Michael S. Tsirkin <m...@redhat.com> --- On Mon, Jan 28, 2013 at 05:38:24PM +0800, Jason Wang wrote: > On Saturday, January 26, 2013 11:29:49 AM Toralf Förster wrote: > > Re: How to find an unused TAP device with kernel 3.8 ? > > With kernel 3.8. I just realized that all pre-defined TAP devices are > > RUNNING even if no virtual linux system is using it. Now I'm wondering > > whether this is a new feature of the upcoming kernel, a bug of the old - > > and how I can avoid that. > > > > Background : When I start a user mode linux instance, I currently grep > > for the next free tap device in this way : > > > > Code: > > for t in $(ifconfig | grep "^tap" | cut -f1 -d:) > > do > > ethtool $t | grep -q 'Link detected: no' > > if [[ $? -eq 0 ]]; then > > NET="tuntap,$t" > > break > > fi > > done > > > > but this doesn't work now anymore. > > > > Here is the diff in dmesg > > > > $ diff 3.7.1 3.8.0-rc1+ | grep UP > > > > < br0: flags=4355<UP,BROADCAST,PROMISC,MULTICAST> mtu 1500 > > > > > br0: flags=4419<UP,BROADCAST,RUNNING,PROMISC,MULTICAST> mtu 1500 > > > > < tap0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 > > > > > tap0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 > > > > more details : http://forums.gentoo.org/viewtopic-p-7211498.html#7211498 > > Looks like something wrong with the carrier detection of tap. > > Please try the following patch to see if it helps. > > Thanks. > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > > > index cc09b67..d8a53c3 100644 > > > --- a/drivers/net/tun.c > > > +++ b/drivers/net/tun.c > > > @@ -438,6 +438,9 @@ static void __tun_detach(struct tun_file *tfile, bool > clean) > sock_put(&tfile->sk); > > > } > > > > > > + if (tun && tun->numqueues == 0) > > > + netif_carrier_off(tun->dev); > > > + > > > if (clean) { > > > if (tun && tun->numqueues == 0 && tun->numdisabled == 0 && > > > !(tun->flags & TUN_PERSIST)) > > > @@ -473,6 +476,7 @@ static void tun_detach_all(struct net_device *dev) > BUG_ON(tun->numqueues != 0); > > > > > > synchronize_net(); > > > + netif_carrier_off(dev); > > > for (i = 0; i < n; i++) { > > > tfile = rtnl_dereference(tun->tfiles[i]); > > > /* Drop read queue */ > > > @@ -531,6 +535,7 @@ static int tun_attach(struct tun_struct *tun, struct file > *file) > sock_hold(&tfile->sk); > > > > > > tun_set_real_num_queues(tun); > > > + netif_carrier_on(tun->dev); > > > > > > /* device is allowed to go away first, so no need to hold extra > > > * refcnt. > > This will set carrier off if all queues are disabled, which I think is a problem as it would confuse the script. How about the following instead: diff --git a/drivers/net/tun.c b/drivers/net/tun.c index af372d0..00dfdad 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1644,10 +1644,10 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) device_create_file(&tun->dev->dev, &dev_attr_owner) || device_create_file(&tun->dev->dev, &dev_attr_group)) pr_err("Failed to create tun sysfs files\n"); - - netif_carrier_on(tun->dev); } + netif_carrier_on(tun->dev); + tun_debug(KERN_INFO, tun, "tun_set_iff\n"); if (ifr->ifr_flags & IFF_NO_PI) @@ -2124,6 +2124,8 @@ static int tun_chr_close(struct inode *inode, struct file *file) struct tun_file *tfile = file->private_data; struct net *net = tfile->net; + netif_carrier_off(tun->dev); + tun_detach(tfile, true); put_net(net); -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
