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datapath: Fix mutual exclusion with bridge module.

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Mutual exclusion with the Linux bridge module has always been a problem.
But I think that this new approach should work reliably.  It is also
simpler.
This commit is contained in:
Ben Pfaff
2010-06-02 15:35:15 -07:00
parent 1e82e503c5
commit 106eab5dfd
1 changed files with 16 additions and 65 deletions
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81
datapath/vport-netdev.c
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@@ -26,64 +26,6 @@ struct vport_ops netdev_vport_ops;
static void netdev_port_receive(struct net_bridge_port *, struct sk_buff *);
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,27)
static struct llc_sap *netdev_stp_sap;
static int
netdev_stp_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt, struct net_device *orig_dev)
{
/* We don't really care about STP packets, we just listen for them for
* mutual exclusion with the bridge module, so this just discards
* them. */
kfree_skb(skb);
return 0;
}
static int
netdev_avoid_bridge_init(void)
{
/* Register to receive STP packets because the bridge module also
* attempts to do so. Since there can only be a single listener for a
* given protocol, this provides mutual exclusion against the bridge
* module, preventing both of them from being loaded at the same
* time. */
netdev_stp_sap = llc_sap_open(LLC_SAP_BSPAN, netdev_stp_rcv);
if (!netdev_stp_sap) {
printk(KERN_ERR "openvswitch: can't register sap for STP (probably the bridge module is loaded)\n");
return -EADDRINUSE;
}
return 0;
}
static void
netdev_avoid_bridge_exit(void)
{
llc_sap_put(netdev_stp_sap);
}
#else /* Linux 2.6.27 or later. */
static int
netdev_avoid_bridge_init(void)
{
/* Linux 2.6.27 introduces a way for multiple clients to register for
* STP packets, which interferes with what we try to do above.
* Instead, just check whether there's a bridge hook defined. This is
* not as safe--the bridge module is willing to load over the top of
* us--but it provides a little bit of protection. */
if (br_handle_frame_hook) {
printk(KERN_ERR "openvswitch: bridge module is loaded, cannot load over it\n");
return -EADDRINUSE;
}
return 0;
}
static void
netdev_avoid_bridge_exit(void)
{
/* Nothing to do. */
}
#endif /* Linux 2.6.27 or later */
/*
* Used as br_handle_frame_hook. (Cannot run bridge at the same time, even on
* different set of devices!)
@@ -111,12 +53,6 @@ netdev_frame_hook(struct net_bridge_port *p, struct sk_buff **pskb)
static int
netdev_init(void)
{
int err;
err = netdev_avoid_bridge_init();
if (err)
return err;
/* Hook into callback used by the bridge to intercept packets.
* Parasites we are. */
br_handle_frame_hook = netdev_frame_hook;
@@ -128,7 +64,6 @@ static void
netdev_exit(void)
{
br_handle_frame_hook = NULL;
netdev_avoid_bridge_exit();
}
static struct vport *
@@ -379,3 +314,19 @@ struct vport_ops netdev_vport_ops = {
.get_mtu = netdev_get_mtu,
.send = netdev_send,
};
/*
* Open vSwitch cannot safely coexist with the Linux bridge module on any
* released version of Linux, because there is only a single bridge hook
* function and only a single br_port member in struct net_device.
*
* Declaring and exporting this symbol enforces mutual exclusion. The bridge
* module also exports the same symbol, so the module loader will refuse to
* load both modules at the same time (e.g. "bridge: exports duplicate symbol
* br_should_route_hook (owned by openvswitch_mod)").
*
* The use of "typeof" here avoids the need to track changes in the type of
* br_should_route_hook over various kernel versions.
*/
typeof(br_should_route_hook) br_should_route_hook;
EXPORT_SYMBOL(br_should_route_hook);