bonding: move IPv6 support into a separate kernel module

[Possible fix for bonding IPv6 regression reported by Andrey Borzenkov, tried to keep all Cc's]

This patch moves the IPv6 bonding code into a separate kernel module called bonding_ipv6 if either bonding or IPv6 are built as modules. If both are built into the kernel then this is as well. Bonding_ipv6.ko registers an "send_unsol_na" function pointer for the unsolicited advertisement function to be called on a failover - the default action is to do nothing. The notifier callbacks are now registered in this module and not in the base bonding module.

---
 Documentation/networking/bonding.txt |    3 ++
 drivers/net/bonding/Makefile         |    5 ++-
 drivers/net/bonding/bond_ipv6.c      |   13 +++++++-
 drivers/net/bonding/bond_main.c      |   52
++++++++++++++++++++++++++++++---
 drivers/net/bonding/bonding.h        |    9 +++--
 5 files changed, 69 insertions(+), 13 deletions(-)

b/Documentation/networking/bonding.txt
index 5ede747..c8b1c1f 100644

@@ -603,6 +603,9 @@ num_unsol_na
 	affects only the active-backup mode.  This option was added for
 	bonding version 3.4.0.
 
+	In order to get this functionality, you will need to load the
+	Bonding IPv6 module with 'modprobe bonding_ipv6'.
+
 primary
 
 	A string (eth0, eth2, etc) specifying which slave is the

index 6f9c6fa..d4f6338 100644
@@ -6,6 +6,7 @@ obj-$(CONFIG_BONDING) += bonding.o
 
 bonding-objs := bond_main.o bond_3ad.o bond_alb.o bond_sysfs.o
 
-ipv6-$(subst m,y,$(CONFIG_IPV6)) += bond_ipv6.o
-bonding-objs += $(ipv6-y)
+# build bonding_ipv6 as module whenever either IPv6 or Bonding is a module
+obj-$(subst y,$(CONFIG_BONDING),$(CONFIG_IPV6)) += bonding_ipv6.o
+bonding_ipv6-y := bond_ipv6.o
 

b/drivers/net/bonding/bond_ipv6.c
index 0d73bf5..2f10514 100644

@@ -20,6 +20,9 @@
  *
  */
 
+#include <linux/module.h>
+#include <linux/init.h>
+
 #include <linux/types.h>
 #include <linux/if_vlan.h>
 #include <net/ipv6.h>

@@ -204,13 +207,19 @@ static struct notifier_block

bond_inet6addr_notifier = {
.notifier_call = bond_inet6addr_event,
};

-void bond_register_ipv6_notifier(void)
+static int __init bonding_ipv6_init(void)
{
+ bond_register_ipv6_na(bond_send_unsolicited_na);
register_inet6addr_notifier(&bond_inet6addr_notifier);
+ return 0;
}

-void bond_unregister_ipv6_notifier(void)
+static void __exit bonding_ipv6_exit(void)
{
unregister_inet6addr_notifier(&bond_inet6addr_notifier);
+ bond_unregister_ipv6_na();
}

+module_init(bonding_ipv6_init)
+module_exit(bonding_ipv6_exit)
+MODULE_LICENSE("GPL");

b/drivers/net/bonding/bond_main.c
index 2c96b93..ff61add 100644

@@ -149,6 +149,12 @@ static const char * const version =
 	DRV_DESCRIPTION ": v" DRV_VERSION " (" DRV_RELDATE ")\n";
 
 LIST_HEAD(bond_dev_list);
+EXPORT_SYMBOL(bond_dev_list);
+
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+static DEFINE_SPINLOCK(bond_v6_na_lock);
+#endif
+static void (*bond_send_unsol_na)(struct bonding *bond);
 
 #ifdef CONFIG_PROC_FS
 static struct proc_dir_entry *bond_proc_dir = NULL;

@@ -1201,6 +1207,8 @@ void bond_change_active_slave(struct bonding

*bond, struct slave *new_active)
}

if (new_active) {
+ void (*send_unsol_na)(struct bonding *bond);
+
bond_set_slave_active_flags(new_active);

if (bond->params.fail_over_mac)
@@ -1211,7 +1219,11 @@ void bond_change_active_slave(struct bonding *bond, struct slave *new_active)
bond_send_gratuitous_arp(bond);

bond->send_unsol_na = bond->params.num_unsol_na;
- bond_send_unsolicited_na(bond);
+ rcu_read_lock();
+ send_unsol_na = rcu_dereference(bond_send_unsol_na);
+ if (send_unsol_na)
+ send_unsol_na(bond);
+ rcu_read_unlock();

write_unlock_bh(&bond->curr_slave_lock); read_unlock(&bond->lock);
@@ -2464,8 +2476,14 @@ void bond_mii_monitor(struct work_struct *work)
}

if (bond->send_unsol_na) {
+ void (*send_unsol_na)(struct bonding *bond);
+
read_lock(&bond->curr_slave_lock);
- bond_send_unsolicited_na(bond);
+ rcu_read_lock();
+ send_unsol_na = rcu_dereference(bond_send_unsol_na);
+ if (send_unsol_na)
+ send_unsol_na(bond);
+ rcu_read_unlock();
read_unlock(&bond->curr_slave_lock);
}

@@ -3165,8 +3183,14 @@ void bond_activebackup_arp_mon(struct work_struct *work)
}

if (bond->send_unsol_na) {
+ void (*send_unsol_na)(struct bonding *bond);
+
read_lock(&bond->curr_slave_lock);
- bond_send_unsolicited_na(bond);
+ rcu_read_lock();
+ send_unsol_na = rcu_dereference(bond_send_unsol_na);
+ if (send_unsol_na)
+ send_unsol_na(bond);
+ rcu_read_unlock();
read_unlock(&bond->curr_slave_lock);
}

@@ -5203,6 +5227,26 @@ out_rtnl:
return res;
}

+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) +void bond_register_ipv6_na(void (*send_unsol_na) (struct bonding *bond)) +{
+ spin_lock_bh(&bond_v6_na_lock);
+ rcu_assign_pointer(bond_send_unsol_na, send_unsol_na);
+ spin_unlock_bh(&bond_v6_na_lock);
+ synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(bond_register_ipv6_na);
+
+void bond_unregister_ipv6_na(void)
+{
+ spin_lock_bh(&bond_v6_na_lock);
+ rcu_assign_pointer(bond_send_unsol_na, NULL);
+ spin_unlock_bh(&bond_v6_na_lock);
+ synchronize_rcu();
+}
+EXPORT_SYMBOL(bond_unregister_ipv6_na);
+#endif
+
static int __init bonding_init(void)
{
int i;
@@ -5234,7 +5278,6 @@ static int __init bonding_init(void)

register_netdevice_notifier(&bond_netdev_notifier); register_inetaddr_notifier(&bond_inetaddr_notifier);
- bond_register_ipv6_notifier();

goto out;
err:
@@ -5257,7 +5300,6 @@ static void __exit bonding_exit(void)
{
unregister_netdevice_notifier(&bond_netdev_notifier); unregister_inetaddr_notifier(&bond_inetaddr_notifier);
- bond_unregister_ipv6_notifier();

bond_destroy_sysfs();

index ca849d2..9e5e092 100644
@@ -23,15 +23,13 @@
 #include "bond_3ad.h"
 #include "bond_alb.h"
 
-#define DRV_VERSION	"3.5.0"
-#define DRV_RELDATE	"November 4, 2008"
+#define DRV_VERSION	"3.6.0"
+#define DRV_RELDATE	"February 20, 2009"
 #define DRV_NAME	"bonding"
 #define DRV_DESCRIPTION	"Ethernet Channel Bonding Driver"
 
 #define BOND_MAX_ARP_TARGETS	16
 
-extern struct list_head bond_dev_list;
-
 #define IS_UP(dev)					   \
 	      ((((dev)->flags & IFF_UP) == IFF_UP)	&& \
 	       netif_running(dev)			&& \

@@ -360,6 +358,9 @@ extern struct rw_semaphore bonding_rwsem;
 void bond_send_unsolicited_na(struct bonding *bond);
 void bond_register_ipv6_notifier(void);
 void bond_unregister_ipv6_notifier(void);
+
+void bond_register_ipv6_na(void (*send_unsol_na) (struct bonding *bond));
+void bond_unregister_ipv6_na(void);
 #else
 static inline void bond_send_unsolicited_na(struct bonding *bond)
 {

1.5.4.3

From: Brian Haley <[email protected]>
Date: Fri, 20 Feb 2009 19:31:29 -0500

Thanks for taking the time to work on this Brian.

I wonder if we aren't just trading one evil for another.

Right now just configuring bonding will get the bonding module loaded and the ipv6 facilities will be visible.

Now with your change, the user has to explicitly load the module. That's extremely user-unfriendly.

Especially since bonding is working between layers 1 and 2 and provides a protocol-agnostic ethernet-like interface. It would seem very confusing to load ethernet drivers depending on the protocols we expect to run on top of them :-/

Willy

I agree, part of me just wanted to make sure it could be done, and figured it was just a matter of time before my hand was forced, or the original commit was reverted.

One idea is that the IPv6 notifier, addrconf_notify(), could try and load the bonding_ipv6 module if a device with IFF_MASTER registered. I haven't prototyped it to see if it would actually work, seemed like a hack.

-Brian