diff mbox series

[net-next,v3,2/4] net: hdlc_fr: Change the use of "dev" in fr_rx to make the code cleaner

Message ID 20201028184310.7017-3-xie.he.0141@gmail.com (mailing list archive)
State Not Applicable
Delegated to: Netdev Maintainers
Headers show
Series net: hdlc_fr: Add support for any Ethertype | expand

Commit Message

Xie He Oct. 28, 2020, 6:43 p.m. UTC 
The eth_type_trans function is called when we receive frames carrying
Ethernet frames. This function expects a non-NULL pointer as an argument,
and assigns it directly to skb->dev.

However, the code handling other types of frames first assigns a pointer
to "dev", and then at the end checks whether the value is NULL, and if it
is not NULL, assigns it to skb->dev.

The two flows are different. Mixing them in this function makes the code
messy. It's better that we convert the second flow to align with how
eth_type_trans does things.

So this patch changes the code to: first make sure the pointer is not
NULL, then assign it directly to skb->dev. "dev" is no longer needed until
the end where we use it to update stats.

Cc: Krzysztof Halasa <khc@pm.waw.pl>
Signed-off-by: Xie He <xie.he.0141@gmail.com>
---
 drivers/net/wan/hdlc_fr.c | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

Comments

Willem de Bruijn Oct. 29, 2020, 4:58 p.m. UTC | #1 
On Wed, Oct 28, 2020 at 10:12 PM Xie He <xie.he.0141@gmail.com> wrote:
>
> The eth_type_trans function is called when we receive frames carrying
> Ethernet frames. This function expects a non-NULL pointer as an argument,
> and assigns it directly to skb->dev.
>
> However, the code handling other types of frames first assigns a pointer
> to "dev", and then at the end checks whether the value is NULL, and if it
> is not NULL, assigns it to skb->dev.
>
> The two flows are different. Mixing them in this function makes the code
> messy. It's better that we convert the second flow to align with how
> eth_type_trans does things.
>
> So this patch changes the code to: first make sure the pointer is not
> NULL, then assign it directly to skb->dev. "dev" is no longer needed until
> the end where we use it to update stats.

No need for dev at all then?
Xie He Oct. 29, 2020, 11:15 p.m. UTC | #2 
On Thu, Oct 29, 2020 at 9:58 AM Willem de Bruijn
<willemdebruijn.kernel@gmail.com> wrote:
>
> No need for dev at all then?

Right, there's no need for "dev" at all actually. I kept "dev" just to
keep the code for updating "dev->stats" simpler, because otherwise we
need to write "skb->dev->stats" instead, and there are 3 lines where
we need to write it.
diff mbox series

Patch

diff --git a/drivers/net/wan/hdlc_fr.c b/drivers/net/wan/hdlc_fr.c
index c774eff44534..ac65f5c435ef 100644
--- a/drivers/net/wan/hdlc_fr.c
+++ b/drivers/net/wan/hdlc_fr.c
@@ -880,7 +880,7 @@  static int fr_rx(struct sk_buff *skb)
 	u8 *data = skb->data;
 	u16 dlci;
 	struct pvc_device *pvc;
-	struct net_device *dev = NULL;
+	struct net_device *dev;
 
 	if (skb->len <= 4 || fh->ea1 || data[2] != FR_UI)
 		goto rx_error;
@@ -930,13 +930,17 @@  static int fr_rx(struct sk_buff *skb)
 	}
 
 	if (data[3] == NLPID_IP) {
+		if (!pvc->main)
+			goto rx_drop;
 		skb_pull(skb, 4); /* Remove 4-byte header (hdr, UI, NLPID) */
-		dev = pvc->main;
+		skb->dev = pvc->main;
 		skb->protocol = htons(ETH_P_IP);
 
 	} else if (data[3] == NLPID_IPV6) {
+		if (!pvc->main)
+			goto rx_drop;
 		skb_pull(skb, 4); /* Remove 4-byte header (hdr, UI, NLPID) */
-		dev = pvc->main;
+		skb->dev = pvc->main;
 		skb->protocol = htons(ETH_P_IPV6);
 
 	} else if (skb->len > 10 && data[3] == FR_PAD &&
@@ -950,13 +954,16 @@  static int fr_rx(struct sk_buff *skb)
 		case ETH_P_IPX:
 		case ETH_P_IP:	/* a long variant */
 		case ETH_P_IPV6:
-			dev = pvc->main;
+			if (!pvc->main)
+				goto rx_drop;
+			skb->dev = pvc->main;
 			skb->protocol = htons(pid);
 			break;
 
 		case 0x80C20007: /* bridged Ethernet frame */
-			if ((dev = pvc->ether) != NULL)
-				skb->protocol = eth_type_trans(skb, dev);
+			if (!pvc->ether)
+				goto rx_drop;
+			skb->protocol = eth_type_trans(skb, pvc->ether);
 			break;
 
 		default:
@@ -970,17 +977,13 @@  static int fr_rx(struct sk_buff *skb)
 		goto rx_drop;
 	}
 
-	if (dev) {
-		dev->stats.rx_packets++; /* PVC traffic */
-		dev->stats.rx_bytes += skb->len;
-		if (pvc->state.becn)
-			dev->stats.rx_compressed++;
-		skb->dev = dev;
-		netif_rx(skb);
-		return NET_RX_SUCCESS;
-	} else {
-		goto rx_drop;
-	}
+	dev = skb->dev;
+	dev->stats.rx_packets++; /* PVC traffic */
+	dev->stats.rx_bytes += skb->len;
+	if (pvc->state.becn)
+		dev->stats.rx_compressed++;
+	netif_rx(skb);
+	return NET_RX_SUCCESS;
 
 rx_error:
 	frad->stats.rx_errors++; /* Mark error */