[PATCH net-2.6.25] [BRIDGE] Remove useless code in net/bridge/br_netfilter.c

[PATCH net-2.6.25] [BRIDGE] Remove useless code in net/bridge/br_netfilter.c

[Rami Rosen]

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Hi,

These following two commands in br_nf_forward_arp() achieve nothing and
should be removed; the d variable is not used later in this method:

	...
	struct net_device **d = (struct net_device **)(skb->cb);
	...
	*d = (struct net_device *)in;
	...

Regards,
Rami Rosen


Signed-off-by: Rami Rosen <ramirose@gmail.com>

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diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index 32ac035..288e102 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -664,8 +664,6 @@ static unsigned int br_nf_forward_arp(unsigned int hook, struct sk_buff *skb,
 				      const struct net_device *out,
 				      int (*okfn)(struct sk_buff *))
 {
-	struct net_device **d = (struct net_device **)(skb->cb);
-
 #ifdef CONFIG_SYSCTL
 	if (!brnf_call_arptables)
 		return NF_ACCEPT;
@@ -682,7 +680,6 @@ static unsigned int br_nf_forward_arp(unsigned int hook, struct sk_buff *skb,
 			nf_bridge_push_encap_header(skb);
 		return NF_ACCEPT;
 	}
-	*d = (struct net_device *)in;
 	NF_HOOK(NF_ARP, NF_ARP_FORWARD, skb, (struct net_device *)in,
 		(struct net_device *)out, br_nf_forward_finish);
 

Re: [PATCH net-2.6.25] [BRIDGE] Remove useless code in net/bridge/br_netfilter.c

[David Miller]

From: "Rami Rosen" <ramirose@gmail.com>
Date: Tue, 1 Jan 2008 12:48:14 +0200

> These following two commands in br_nf_forward_arp() achieve nothing and
> should be removed; the d variable is not used later in this method:
> 
> 	...
> 	struct net_device **d = (struct net_device **)(skb->cb);
> 	...
> 	*d = (struct net_device *)in;
> 	...
> 
> Signed-off-by: Rami Rosen <ramirose@gmail.com>

It's a pointer dereference assignment, this last line has a
side effect, therefore you can't remove it.

The code is equivalent to:

struct skb_bridge_info {
	struct net_device *dev;
};

	struct skb_bridge_info *d;

	d = (struct skb_bridge_info *) skb->cb;

	d->dev = in;

What automated tool showed this as useless to you?

Please correct it's logic so it doesn't mark real side effects like
this as superfluous.

Thanks.

Re: [PATCH net-2.6.25] [BRIDGE] Remove useless code in net/bridge/br_netfilter.c

[Rami Rosen]

Hi,
> It's a pointer dereference assignment,
Sorry, I was wrong here !

> What automated tool showed this as useless to you?
> Please correct it's logic so it doesn't mark real side effects like
> this as superfluous.

I am not using any automated tool, only my eyes. And I
missed the intention here. It could be implemnted differently
but since it not marked as superfluous anywhere I suggest
to leave it as it is.

Sorry,

Regards,
Rami Rosen





On Jan 2, 2008 7:20 AM, David Miller <davem@davemloft.net> wrote:
> From: "Rami Rosen" <ramirose@gmail.com>
> Date: Tue, 1 Jan 2008 12:48:14 +0200
>
> > These following two commands in br_nf_forward_arp() achieve nothing and
> > should be removed; the d variable is not used later in this method:
> >
> >       ...
> >       struct net_device **d = (struct net_device **)(skb->cb);
> >       ...
> >       *d = (struct net_device *)in;
> >       ...
> >
> > Signed-off-by: Rami Rosen <ramirose@gmail.com>
>
> It's a pointer dereference assignment, this last line has a
> side effect, therefore you can't remove it.
>
> The code is equivalent to:
>
> struct skb_bridge_info {
>         struct net_device *dev;
> };
>
>         struct skb_bridge_info *d;
>
>         d = (struct skb_bridge_info *) skb->cb;
>
>         d->dev = in;
>
> What automated tool showed this as useless to you?
>
> Please correct it's logic so it doesn't mark real side effects like
> this as superfluous.
>
> Thanks.
>