From: "Luis R. Rodriguez" <mcg...@suse.com>
The networking bridge module allows us to specify a
root block preference on net_devices but this feature
is a bridge port primitive. The bridge module assumes
that once a device is added as a slave to the brige
that it can be considered for the the root port.
Furthermore ndo_add_slave() only lets us pass on the
net_device, but drivers that want to root block
since the beginning need specify their root block
preference prior to register_netdevice(). This means
the tun driver must expose a knob to userspace to
enable toggling this feature prior to adding the
device to a bridge to prevent any undesired link
bouncing issues on the bridge.
This should be useful for TAP interfaces which are used
for virtualization.
Cc: Stephen Hemminger <step...@networkplumber.org>
Cc: bridge@lists.linux-foundation.org
Cc: net...@vger.kernel.org
Cc: linux-ker...@vger.kernel.org
Cc: xen-de...@lists.xenproject.org
Cc: k...@vger.kernel.org
Signed-off-by: Luis R. Rodriguez <mcg...@suse.com>
---
drivers/net/tun.c | 6 +++++-
include/uapi/linux/if_tun.h | 1 +
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 8fe9cb7..e763fad 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1693,6 +1693,9 @@ static int tun_set_iff(struct net *net, struct file
*file, struct ifreq *ifr)
if (err < 0)
goto err_free_flow;
+ if (ifr->ifr_flags & IFF_ROOT_BLOCK)
+ dev->priv_flags |= IFF_BRIDGE_ROOT_BLOCK;
+
err = register_netdevice(tun->dev);
if (err < 0)
goto err_detach;
@@ -1898,7 +1901,8 @@ 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_MULTI_QUEUE,
+ IFF_VNET_HDR | IFF_MULTI_QUEUE |
+ IFF_ROOT_BLOCK,
(unsigned int __user*)argp);
} else if (cmd == TUNSETQUEUE)
return tun_set_queue(file, &ifr);
diff --git a/include/uapi/linux/if_tun.h b/include/uapi/linux/if_tun.h
index e9502dd..f814a85 100644
--- a/include/uapi/linux/if_tun.h
+++ b/include/uapi/linux/if_tun.h
@@ -73,6 +73,7 @@
/* read-only flag */
#define IFF_PERSIST 0x0800
#define IFF_NOFILTER 0x1000
+#define IFF_ROOT_BLOCK 0x2000
/* Socket options */
#define TUN_TX_TIMESTAMP 1
--
1.9.0
