[PATCH net-next v3] packet: uses kfree_skb() for errors.

[PATCH net-next v3] packet: uses kfree_skb() for errors.

[Weongyo Jeong]

consume_skb() isn't for error cases that kfree_skb() is more proper
one.  At this patch, it fixed tpacket_rcv() and packet_rcv() to be
consistent for error or non-error cases letting perf trace its event
properly.

Signed-off-by: Weongyo Jeong <weongyo.linux@gmail.com>
---
 net/packet/af_packet.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 1ecfa71..4e054bb 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2042,6 +2042,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
 	u8 *skb_head = skb->data;
 	int skb_len = skb->len;
 	unsigned int snaplen, res;
+	bool err = false;
 
 	if (skb->pkt_type == PACKET_LOOPBACK)
 		goto drop;
@@ -2130,6 +2131,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
 	return 0;
 
 drop_n_acct:
+	err = true;
 	spin_lock(&sk->sk_receive_queue.lock);
 	po->stats.stats1.tp_drops++;
 	atomic_inc(&sk->sk_drops);
@@ -2141,7 +2143,10 @@ drop_n_restore:
 		skb->len = skb_len;
 	}
 drop:
-	consume_skb(skb);
+	if (!err)
+		consume_skb(skb);
+	else
+		kfree_skb(skb);
 	return 0;
 }
 
@@ -2160,6 +2165,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 	struct sk_buff *copy_skb = NULL;
 	struct timespec ts;
 	__u32 ts_status;
+	bool err = false;
 
 	/* struct tpacket{2,3}_hdr is aligned to a multiple of TPACKET_ALIGNMENT.
 	 * We may add members to them until current aligned size without forcing
@@ -2367,10 +2373,14 @@ drop_n_restore:
 		skb->len = skb_len;
 	}
 drop:
-	kfree_skb(skb);
+	if (!err)
+		consume_skb(skb);
+	else
+		kfree_skb(skb);
 	return 0;
 
 drop_n_account:
+	err = true;
 	po->stats.stats1.tp_drops++;
 	spin_unlock(&sk->sk_receive_queue.lock);
 
-- 
2.1.3

Re: [PATCH net-next v3] packet: uses kfree_skb() for errors.

[David Miller]

From: Weongyo Jeong <weongyo.linux@gmail.com>
Date: Fri,  8 Apr 2016 09:25:48 -0700

> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index 1ecfa71..4e054bb 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -2042,6 +2042,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
>  	u8 *skb_head = skb->data;
>  	int skb_len = skb->len;
>  	unsigned int snaplen, res;
> +	bool err = false;
>  
>  	if (skb->pkt_type == PACKET_LOOPBACK)
>  		goto drop;

It is non-canonical to use a variable named 'err' as a boolean.
Instead, all programmers expect a variable named 'err' to be an
integer type and to hold an error code.

Therefore please use a more appropriate name for this variable.

Name it in a way which describes the exact important condition
which is true or false.

Thank you.

Re: [PATCH net-next v3] packet: uses kfree_skb() for errors.

[Weongyo Jeong]

On Wed, Apr 13, 2016 at 10:56:01PM -0400, David Miller wrote:
> From: Weongyo Jeong <weongyo.linux@gmail.com>
> Date: Fri,  8 Apr 2016 09:25:48 -0700
> 
> > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> > index 1ecfa71..4e054bb 100644
> > --- a/net/packet/af_packet.c
> > +++ b/net/packet/af_packet.c
> > @@ -2042,6 +2042,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
> >  	u8 *skb_head = skb->data;
> >  	int skb_len = skb->len;
> >  	unsigned int snaplen, res;
> > +	bool err = false;
> >  
> >  	if (skb->pkt_type == PACKET_LOOPBACK)
> >  		goto drop;
> 
> It is non-canonical to use a variable named 'err' as a boolean.
> Instead, all programmers expect a variable named 'err' to be an
> integer type and to hold an error code.
> 
> Therefore please use a more appropriate name for this variable.
> 
> Name it in a way which describes the exact important condition
> which is true or false.
> 
> Thank you.

Thank you for your opinion.  I'd fixed it to proper name and
submitted v4 patch.

Regards,
Weongyo Jeong