Linux Ethernet Bridging - Aug 2010 - [Bridge] [patch net-next-2.6] bridge: allow hub-like behaviour

This patch allows bridge to behave much like ordinary hub. That means that
every frame received is forwarded to all ports. This functionality is of course
disabled by default, can be enabled via sysfs. This could be handy mainly for
testing purposes.

Signed-off-by: Jiri Pirko <jpirko at redhat.com>
---
 net/bridge/br_device.c   |   14 +++++++++-----
 net/bridge/br_input.c    |   12 +++++++++---
 net/bridge/br_private.h  |    1 +
 net/bridge/br_sysfs_br.c |   25 +++++++++++++++++++++++++
 4 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index cf09fe5..1bfc1c5 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -60,14 +60,18 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct
net_device *dev)
 		}
 
 		mdst = br_mdb_get(br, skb);
-		if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb))
+		if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
+		     likely(!br->hub_mode))
 			br_multicast_deliver(mdst, skb);
 		else
 			br_flood_deliver(br, skb);
-	} else if ((dst = __br_fdb_get(br, dest)) != NULL)
-		br_deliver(dst->dst, skb);
-	else
-		br_flood_deliver(br, skb);
+	} else {
+		dst = __br_fdb_get(br, dest);
+		if (dst && likely(!br->hub_mode))
+			br_deliver(dst->dst, skb);
+		else
+			br_flood_deliver(br, skb);
+	}
 
 out:
 	rcu_read_unlock();
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 826cd52..24ee87e 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -75,7 +75,8 @@ int br_handle_frame_finish(struct sk_buff *skb)
 
 	if (is_multicast_ether_addr(dest)) {
 		mdst = br_mdb_get(br, skb);
-		if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
+		if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
+		    likely(!br->hub_mode)) {
 			if ((mdst && !hlist_unhashed(&mdst->mglist)) ||
 			    br_multicast_is_router(br))
 				skb2 = skb;
@@ -89,8 +90,13 @@ int br_handle_frame_finish(struct sk_buff *skb)
 		br->dev->stats.multicast++;
 	} else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
 		skb2 = skb;
-		/* Do not forward the packet since it's local. */
-		skb = NULL;
+		if (likely(!br->hub_mode)) {
+			/* Do not forward the packet since it's local. */
+			skb = NULL;
+		} else {
+			/* In hub mode we want to forward the packet to all. */
+			dst = NULL;
+		}
 	}
 
 	if (skb) {
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 75c90ed..b6a9a7e 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -194,6 +194,7 @@ struct net_bridge
 	unsigned long			ageing_time;
 	unsigned long			bridge_hello_time;
 	unsigned long			bridge_forward_delay;
+	bool				hub_mode;
 
 	u8				group_addr[ETH_ALEN];
 	u16				root_port;
diff --git a/net/bridge/br_sysfs_br.c b/net/bridge/br_sysfs_br.c
index 5c1e555..ac98aa4 100644
--- a/net/bridge/br_sysfs_br.c
+++ b/net/bridge/br_sysfs_br.c
@@ -345,6 +345,30 @@ static ssize_t store_flush(struct device *d,
 }
 static DEVICE_ATTR(flush, S_IWUSR, NULL, store_flush);
 
+static ssize_t show_hub_mode(struct device *d,
+			     struct device_attribute *attr, char *buf)
+{
+	struct net_bridge *br = to_bridge(d);
+
+	return sprintf(buf, "%d\n", br->hub_mode ? 1 : 0);
+}
+
+static int set_hub_mode(struct net_bridge *br, unsigned long val)
+{
+	br->hub_mode = val ? true : false;
+	return 0;
+}
+
+static ssize_t store_hub_mode(struct device *d,
+			      struct device_attribute *attr,
+			      const char *buf, size_t len)
+{
+	return store_bridge_parm(d, buf, len, set_hub_mode);
+}
+
+static DEVICE_ATTR(hub_mode, S_IRUGO | S_IWUSR,
+		   show_hub_mode, store_hub_mode);
+
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 static ssize_t show_multicast_router(struct device *d,
 				     struct device_attribute *attr, char *buf)
@@ -698,6 +722,7 @@ static struct attribute *bridge_attrs[] = {
 	&dev_attr_gc_timer.attr,
 	&dev_attr_group_addr.attr,
 	&dev_attr_flush.attr,
+	&dev_attr_hub_mode.attr,
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
 	&dev_attr_multicast_router.attr,
 	&dev_attr_multicast_snooping.attr,
-- 
1.7.2.1

NO. unnecessary

Already possible, without patch. Just set the hold time
on the bridge to 0!

Wed, Aug 11, 2010 at 06:07:41PM CEST, shemminger at vyatta.com
wrote:
>NO. unnecessary
>
>Already possible, without patch. Just set the hold time
>on the bridge to 0!
Sorry, but could you please point me a sysfs node where should I do this
setting? Unable to find this.

Thanks.

On Thu, 12 Aug 2010 13:15:24 +0200
Jiri Pirko <jpirko at redhat.com> wrote:
> Wed, Aug 11, 2010 at 06:07:41PM CEST, shemminger at vyatta.com wrote:
> >NO. unnecessary
> >
> >Already possible, without patch. Just set the hold time
> >on the bridge to 0!
> 
> Sorry, but could you please point me a sysfs node where should I do this
> setting? Unable to find this.
> 
> Thanks.
> 
/sys/class/net/ethX/brport/hold_timer

Thu, Aug 12, 2010 at 03:02:51PM CEST, shemminger at vyatta.com
wrote:
>On Thu, 12 Aug 2010 14:48:48 +0200
>Jiri Pirko <jpirko at redhat.com> wrote:
>
>> Thu, Aug 12, 2010 at 02:35:41PM CEST, shemminger at vyatta.com wrote:
>> >On Thu, 12 Aug 2010 13:15:24 +0200
>> >Jiri Pirko <jpirko at redhat.com> wrote:
>> >
>> >> Wed, Aug 11, 2010 at 06:07:41PM CEST, shemminger at vyatta.com
wrote:
>> >> >NO. unnecessary
>> >> >
>> >> >Already possible, without patch. Just set the hold time
>> >> >on the bridge to 0!
>> >> 
>> >> Sorry, but could you please point me a sysfs node where should
I do this
>> >> setting? Unable to find this.
>> >> 
>> >> Thanks.
>> >> 
>> >
>> >/sys/class/net/ethX/brport/hold_timer
>
>Too early...
>
>hold_time is computed from ageing time, so that is the value
>you need to set:
>
>$ ls -l /sys/class/net/br0/bridge/ageing_time 
>-rw-r--r-- 1 root root 4096 2010-08-12 08:34
/sys/class/net/br0/bridge/ageing_time
Yep, figured that out. Works as expected. Thanks Stephen.

hello
very useful option i must say
i was looking for something like this for quiet a while and now i have a few
comments/question

1.after initially not being able to find this solution i started looking at
the code thinking that a small modification might do the trick
under br_input.c (kernel 2.6.18) around line 58 there is a section that
starts with
"if (br->dev->flags & IFF_PROMISC)
{
 ..
br_pass_frame_up(br,skb2));
..
}
"
to my understanding this should have then the job, all i needed to do was
set the bridge to promsicous mode
that didn't work,
did i get it wrong? what is the meaning of this piece of code

 2. why is this working? what is the logic behind it (ageing=0)
3. why isn't this documented?

finding this thread took a long time and along the way i read other people's
forum posts\mailing list questions,
too bad it's not in the man
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