Patchwork [OpenWrt-Devel,RFC/RFT] generic: Remove IPv6 depependency of bridge in 2.6.38+

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Submitter Jonas Gorski
Date 2011-05-14 14:54:56
Message ID <1305384896-21848-1-git-send-email-jonas.gorski+openwrt@gmail.com>
Download mbox | patch
Permalink /patch/992/
State Accepted
Delegated to: Jo-Philipp Wich
Headers show

Comments

Jonas Gorski - 2011-05-14 14:54:56
Since 2.6.38 the bridge module has a dependency to IPv6 if IPv6 is
enabled. Since the IPv6 module isn't exactly lightweight and bridge also
only needs a single function from IPv6, it's rather easy to create a
common "lib" module with a RCU pointer to the actual implementation, if
the IPv6 module is loaded (although slightly hackish).

The codepath seems to be only taken when using IPv6, so there should be
no negative side effects when IPv6 isn't loaded. I did not measure how
big the performance impact is.

Signed-off-by: Jonas Gorski <jonas.gorski+openwrt@gmail.com>
---
I did some basic testing, and IPv6 uni- and multicast were still working
for me with this patch. It can't hurt to do some more testing though 

 .../643-bridge_remove_ipv6_dependency.patch        |  101 ++++++++++++++++++++
 .../643-bridge_remove_ipv6_dependency.patch        |  101 ++++++++++++++++++++
 2 files changed, 202 insertions(+), 0 deletions(-)
 create mode 100644 target/linux/generic/patches-2.6.38/643-bridge_remove_ipv6_dependency.patch
 create mode 100644 target/linux/generic/patches-2.6.39/643-bridge_remove_ipv6_dependency.patch
Florian Fainelli - 2011-06-04 13:39:17
Hello Jonas,

On Saturday 14 May 2011 16:54:56 Jonas Gorski wrote:
> Since 2.6.38 the bridge module has a dependency to IPv6 if IPv6 is
> enabled. Since the IPv6 module isn't exactly lightweight and bridge also
> only needs a single function from IPv6, it's rather easy to create a
> common "lib" module with a RCU pointer to the actual implementation, if
> the IPv6 module is loaded (although slightly hackish).
> 
> The codepath seems to be only taken when using IPv6, so there should be
> no negative side effects when IPv6 isn't loaded. I did not measure how
> big the performance impact is.
> 
> Signed-off-by: Jonas Gorski <jonas.gorski+openwrt@gmail.com>

The patch looks good at first sight, can you post it on netdev to gather some 
opinions from the Linux networking stack developpers?

Thank you!
Jonas Gorski - 2011-06-05 12:07:37
On 4 June 2011 15:39, Florian Fainelli <florian@openwrt.org> wrote:
> Hello Jonas,
>
> On Saturday 14 May 2011 16:54:56 Jonas Gorski wrote:
>> Since 2.6.38 the bridge module has a dependency to IPv6 if IPv6 is
>> enabled. Since the IPv6 module isn't exactly lightweight and bridge also
>> only needs a single function from IPv6, it's rather easy to create a
>> common "lib" module with a RCU pointer to the actual implementation, if
>> the IPv6 module is loaded (although slightly hackish).
>>
>> The codepath seems to be only taken when using IPv6, so there should be
>> no negative side effects when IPv6 isn't loaded. I did not measure how
>> big the performance impact is.
>>
>> Signed-off-by: Jonas Gorski <jonas.gorski+openwrt@gmail.com>
>
> The patch looks good at first sight, can you post it on netdev to gather some
> opinions from the Linux networking stack developpers?

I can try. My top most reason why I didn't do it yet is that the code
is currently quite hackish (it's more like trying to treat the symptom
than the cause) and I didn't find a clean solution yet (not really
knowing the whole net subsystem doesn't help there either ;-).

Also I still didn't check for any negative performance impacts yet
(there is definitely one, but I don't know if the code paths are
called seldom enough for it to be neglectible).


Jonas

Patch

diff --git a/target/linux/generic/patches-2.6.38/643-bridge_remove_ipv6_dependency.patch b/target/linux/generic/patches-2.6.38/643-bridge_remove_ipv6_dependency.patch
new file mode 100644
index 0000000..7f4f754
--- /dev/null
+++ b/target/linux/generic/patches-2.6.38/643-bridge_remove_ipv6_dependency.patch
@@ -0,0 +1,101 @@ 
+--- a/include/net/addrconf.h
++++ b/include/net/addrconf.h
+@@ -93,6 +93,12 @@ extern void			addrconf_join_solict(struc
+ extern void			addrconf_leave_solict(struct inet6_dev *idev,
+ 					struct in6_addr *addr);
+ 
++extern int			(*ipv6_dev_get_saddr_hook)(struct net *net,
++						struct net_device *dev,
++						const struct in6_addr *daddr,
++						unsigned int srcprefs,
++						struct in6_addr *saddr);
++
+ static inline unsigned long addrconf_timeout_fixup(u32 timeout,
+ 						    unsigned unit)
+ {
+--- a/net/bridge/Kconfig
++++ b/net/bridge/Kconfig
+@@ -6,7 +6,6 @@ config BRIDGE
+ 	tristate "802.1d Ethernet Bridging"
+ 	select LLC
+ 	select STP
+-	depends on IPV6 || IPV6=n
+ 	---help---
+ 	  If you say Y here, then your Linux box will be able to act as an
+ 	  Ethernet bridge, which means that the different Ethernet segments it
+--- a/net/ipv6/Makefile
++++ b/net/ipv6/Makefile
+@@ -40,3 +40,4 @@ obj-$(CONFIG_IPV6_TUNNEL) += ip6_tunnel.
+ obj-y += addrconf_core.o exthdrs_core.o
+ 
+ obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_hashtables.o
++obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_stubs.o
+--- a/net/ipv6/addrconf.c
++++ b/net/ipv6/addrconf.c
+@@ -1119,7 +1119,7 @@ out:
+ 	return ret;
+ }
+ 
+-int ipv6_dev_get_saddr(struct net *net, struct net_device *dst_dev,
++static int __ipv6_dev_get_saddr(struct net *net, struct net_device *dst_dev,
+ 		       const struct in6_addr *daddr, unsigned int prefs,
+ 		       struct in6_addr *saddr)
+ {
+@@ -1244,7 +1244,6 @@ try_nextdev:
+ 	in6_ifa_put(hiscore->ifa);
+ 	return 0;
+ }
+-EXPORT_SYMBOL(ipv6_dev_get_saddr);
+ 
+ int ipv6_get_lladdr(struct net_device *dev, struct in6_addr *addr,
+ 		    unsigned char banned_flags)
+@@ -4718,6 +4717,9 @@ int __init addrconf_init(void)
+ 
+ 	ipv6_addr_label_rtnl_register();
+ 
++	BUG_ON(ipv6_dev_get_saddr_hook != NULL);
++	rcu_assign_pointer(ipv6_dev_get_saddr_hook, __ipv6_dev_get_saddr);
++
+ 	return 0;
+ errout:
+ 	rtnl_af_unregister(&inet6_ops);
+@@ -4736,6 +4738,9 @@ void addrconf_cleanup(void)
+ 	struct net_device *dev;
+ 	int i;
+ 
++	rcu_assign_pointer(ipv6_dev_get_saddr_hook, NULL);
++	synchronize_rcu();
++
+ 	unregister_netdevice_notifier(&ipv6_dev_notf);
+ 	unregister_pernet_subsys(&addrconf_ops);
+ 	ipv6_addr_label_cleanup();
+--- /dev/null
++++ b/net/ipv6/inet6_stubs.c
+@@ -0,0 +1,27 @@
++/*
++ *      This program is free software; you can redistribute it and/or
++ *      modify it under the terms of the GNU General Public License
++ *      as published by the Free Software Foundation; either version
++ *      2 of the License, or (at your option) any later version.
++ */
++#include <net/ipv6.h>
++
++int (*ipv6_dev_get_saddr_hook)(struct net *net, struct net_device *dev,
++			const struct in6_addr *daddr, unsigned int srcprefs,
++			struct in6_addr *saddr);
++
++EXPORT_SYMBOL(ipv6_dev_get_saddr_hook);
++
++int ipv6_dev_get_saddr(struct net *net, struct net_device *dst_dev,
++			const struct in6_addr *daddr, unsigned int prefs,
++			struct in6_addr *saddr)
++{
++	typeof(ipv6_dev_get_saddr_hook) dev_get_saddr = rcu_dereference(ipv6_dev_get_saddr_hook);
++
++	if (dev_get_saddr)
++		return dev_get_saddr(net, dst_dev, daddr, prefs, saddr);
++
++	return -EADDRNOTAVAIL;
++}
++EXPORT_SYMBOL(ipv6_dev_get_saddr);
++
diff --git a/target/linux/generic/patches-2.6.39/643-bridge_remove_ipv6_dependency.patch b/target/linux/generic/patches-2.6.39/643-bridge_remove_ipv6_dependency.patch
new file mode 100644
index 0000000..679561e
--- /dev/null
+++ b/target/linux/generic/patches-2.6.39/643-bridge_remove_ipv6_dependency.patch
@@ -0,0 +1,101 @@ 
+--- a/include/net/addrconf.h
++++ b/include/net/addrconf.h
+@@ -93,6 +93,12 @@ extern void			addrconf_join_solict(struc
+ extern void			addrconf_leave_solict(struct inet6_dev *idev,
+ 					struct in6_addr *addr);
+ 
++extern int			(*ipv6_dev_get_saddr_hook)(struct net *net,
++						struct net_device *dev,
++						const struct in6_addr *daddr,
++						unsigned int srcprefs,
++						struct in6_addr *saddr);
++
+ static inline unsigned long addrconf_timeout_fixup(u32 timeout,
+ 						    unsigned unit)
+ {
+--- a/net/bridge/Kconfig
++++ b/net/bridge/Kconfig
+@@ -6,7 +6,6 @@ config BRIDGE
+ 	tristate "802.1d Ethernet Bridging"
+ 	select LLC
+ 	select STP
+-	depends on IPV6 || IPV6=n
+ 	---help---
+ 	  If you say Y here, then your Linux box will be able to act as an
+ 	  Ethernet bridge, which means that the different Ethernet segments it
+--- a/net/ipv6/Makefile
++++ b/net/ipv6/Makefile
+@@ -40,3 +40,4 @@ obj-$(CONFIG_IPV6_TUNNEL) += ip6_tunnel.
+ obj-y += addrconf_core.o exthdrs_core.o
+ 
+ obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_hashtables.o
++obj-$(subst m,y,$(CONFIG_IPV6)) += inet6_stubs.o
+--- a/net/ipv6/addrconf.c
++++ b/net/ipv6/addrconf.c
+@@ -1116,7 +1116,7 @@ out:
+ 	return ret;
+ }
+ 
+-int ipv6_dev_get_saddr(struct net *net, struct net_device *dst_dev,
++static int __ipv6_dev_get_saddr(struct net *net, struct net_device *dst_dev,
+ 		       const struct in6_addr *daddr, unsigned int prefs,
+ 		       struct in6_addr *saddr)
+ {
+@@ -1241,7 +1241,6 @@ try_nextdev:
+ 	in6_ifa_put(hiscore->ifa);
+ 	return 0;
+ }
+-EXPORT_SYMBOL(ipv6_dev_get_saddr);
+ 
+ int ipv6_get_lladdr(struct net_device *dev, struct in6_addr *addr,
+ 		    unsigned char banned_flags)
+@@ -4715,6 +4714,9 @@ int __init addrconf_init(void)
+ 
+ 	ipv6_addr_label_rtnl_register();
+ 
++	BUG_ON(ipv6_dev_get_saddr_hook != NULL);
++	rcu_assign_pointer(ipv6_dev_get_saddr_hook, __ipv6_dev_get_saddr);
++
+ 	return 0;
+ errout:
+ 	rtnl_af_unregister(&inet6_ops);
+@@ -4733,6 +4735,9 @@ void addrconf_cleanup(void)
+ 	struct net_device *dev;
+ 	int i;
+ 
++	rcu_assign_pointer(ipv6_dev_get_saddr_hook, NULL);
++	synchronize_rcu();
++
+ 	unregister_netdevice_notifier(&ipv6_dev_notf);
+ 	unregister_pernet_subsys(&addrconf_ops);
+ 	ipv6_addr_label_cleanup();
+--- /dev/null
++++ b/net/ipv6/inet6_stubs.c
+@@ -0,0 +1,27 @@
++/*
++ *      This program is free software; you can redistribute it and/or
++ *      modify it under the terms of the GNU General Public License
++ *      as published by the Free Software Foundation; either version
++ *      2 of the License, or (at your option) any later version.
++ */
++#include <net/ipv6.h>
++
++int (*ipv6_dev_get_saddr_hook)(struct net *net, struct net_device *dev,
++			const struct in6_addr *daddr, unsigned int srcprefs,
++			struct in6_addr *saddr);
++
++EXPORT_SYMBOL(ipv6_dev_get_saddr_hook);
++
++int ipv6_dev_get_saddr(struct net *net, struct net_device *dst_dev,
++			const struct in6_addr *daddr, unsigned int prefs,
++			struct in6_addr *saddr)
++{
++	typeof(ipv6_dev_get_saddr_hook) dev_get_saddr = rcu_dereference(ipv6_dev_get_saddr_hook);
++
++	if (dev_get_saddr)
++		return dev_get_saddr(net, dst_dev, daddr, prefs, saddr);
++
++	return -EADDRNOTAVAIL;
++}
++EXPORT_SYMBOL(ipv6_dev_get_saddr);
++