Otherwise 'modprobe -r' on a module having a dependency on bridge will

implicitly unload bridge, bringing down all connectivity that was using

bridges.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
 net/bridge/br_if.c |    9 +++++++++

 1 file changed, 9 insertions(+)
--- linux-2.6.23-rc8/net/bridge/br_if.c	2007-09-26 09:23:54.000000000 +0200

+++ 2.6.23-rc8-bridge-module-get-put/net/bridge/br_if.c	2007-09-25 14:31:01.000000000 +0200

@@ -276,6 +276,11 @@ int br_add_bridge(const char *name)

 	if (!dev)

 		return -ENOMEM;
+	if (!try_module_get(THIS_MODULE)) {

+		free_netdev(dev);

+		return -ENOENT;

+	}

+

 	rtnl_lock();

 	if (strchr(dev->name, '%')) {

 		ret = dev_alloc_name(dev, dev->name);

@@ -294,6 +299,8 @@ int br_add_bridge(const char *name)

 		unregister_netdevice(dev);

  out:

 	rtnl_unlock();

+	if (ret)

+		module_put(THIS_MODULE);

 	return ret;

 }
@@ -321,6 +328,8 @@ int br_del_bridge(const char *name)

 		del_br(netdev_priv(dev));
 	rtnl_unlock();

+	if (ret == 0)

+		module_put(THIS_MODULE);

 	return ret;

 }
-

On Wed, 26 Sep 2007 08:53:27 +0100
No, network devices don't do reference counting.

What is the dependency? Where is the source of the module interacting

with the  bridge?

-

* Wed, 26 Sep 2007 08:37:05 -0700
Could you explain why, please?
After `udevd` on boot loads lots of unused crap, i surrendered, and use

$(rmmod `lsmod | just first column`). Networing bravely wipes away. OK,

there are lots of configs: udev, hotplug, modprobe, that somebody might

like to fix. But it came to the end with me. I just don't care. So,

please answer :)

____

-

On Wed, 26 Sep 2007 23:06:53 +0200
For hotplug and other reasons, the network developers decided that being

able to remove a network module at any time was a good thing. It works.
--

Stephen Hemminger <shemminger@linux-foundation.org>

-

Except that for ipv6.ko, it's all opposite. After modprobe,

it already got a refcount like 8 and you're wondering how

to get rid of that.
-

On Thu, 27 Sep 2007 00:18:55 +0200 (CEST)
ipv6 is not a network driver, it is a protocol. You might be able to remove it if you zap

all the routes and applications, ...
--

Stephen Hemminger <shemminger@linux-foundation.org>

-

Wouldn't it be enough to down all the interfaces and close all the sockets?

No need to bring down every app.
Helge Hafting

-

From: Helge Hafting <helge.hafting@aitel.hist.no>
And there are routes, and neighbour cache entries, and all sorts

of external references to the stack.  For example, if a packet

gets stuck in a device because the link just went down, that

can hold references to the ipv6 module from several angles.
But you have to add code to actually keep track of all of these

references and there is no such code in the ipv6 module at all

and it's a nontrivial time consuming job to implement it.

-

On Thu, 27 Sep 2007 13:54:23 +0200
You need every socket to close and all routes to go away including the routes through

loopback device, and still there probably are control sockets buried inside ipv6

that hold ref count.
IMHO the kernel should just admit that IPV6 can't be removed.
--- a/net/ipv6/af_inet6.c	2007-09-26 16:28:01.000000000 -0700

+++ b/net/ipv6/af_inet6.c	2007-09-26 17:38:23.000000000 -0700

@@ -914,6 +914,9 @@ out_unregister_tcp_proto:

 }

 module_init(inet6_init);
+/* Disabled at present because it is impossible to remove all references */

+#ifdef IPV6_UNLOAD

+

 static void __exit inet6_exit(void)

 {

 	/* First of all disallow new sockets creation. */

@@ -952,5 +955,6 @@ static void __exit inet6_exit(void)

 	proto_unregister(&tcpv6_prot);

 }

 module_exit(inet6_exit);

+#endif
 MODULE_ALIAS_NETPROTO(PF_INET6);

--- a/net/ipv6/addrconf.c	2007-09-26 15:07:35.000000000 -0700

+++ b/net/ipv6/addrconf.c	2007-09-26 17:36:52.000000000 -0700

@@ -4255,6 +4255,7 @@ errout:

 	return err;

 }
+#ifdef IPV6_UNLOAD

 void __exit addrconf_cleanup(void)

 {

 	struct net_device *dev;

@@ -4308,3 +4309,4 @@ void __exit addrconf_cleanup(void)

 	proc_net_remove(&init_net, "if_inet6");

 #endif

 }

+#endif

--- a/net/ipv6/ipv6_sockglue.c	2007-09-26 15:07:35.000000000 -0700

+++ b/net/ipv6/ipv6_sockglue.c	2007-09-26 17:36:17.000000000 -0700

@@ -1132,7 +1132,9 @@ void __init ipv6_packet_init(void)

 	dev_add_pack(&ipv6_packet_type);

 }
-void ipv6_packet_cleanup(void)

+#ifdef IPV6_UNLOAD

+void __exit ipv6_packet_cleanup(void)

 {

 	dev_remove_pack(&ipv6_packet_type);

 }

+#endif

-

I cannot accept that. If ipv6.ko has a way to tack ipv6 structs onto all

sockets, interfaces and addresses, it should also be able to untack it

again.

-

From: Jan Engelhardt <jengelh@computergmbh.de>
Then you do the work and see how incredibly difficult the

implementation is, others have tried.  It's not trivial

and at best it's a very time consuming piece of work to

embark on.
Until then it's un-removable, plain as that :-)
I don't know why we're wasting our fingers discussing this

at all to be honest with you.

-

From: Stephen Hemminger <shemminger@linux-foundation.org>
It is purposefully set to have a permanent elevated reference

count because it is not designed to be unloaded safely.
It has been unloadable forever.

-