can: provide library functions for skb allocation

This patch makes the private functions alloc_can_skb() and
alloc_can_err_skb() of the at91_can driver public and adapts all
drivers to use these. While making the patch I realized, that
the skb's are *not* setup consistently. It's now done as shown
below:

  skb->protocol = htons(ETH_P_CAN);
  skb->pkt_type = PACKET_BROADCAST;
  skb->ip_summed = CHECKSUM_UNNECESSARY;
  *cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));
  memset(*cf, 0, sizeof(struct can_frame));

The frame is zeroed out to avoid uninitialized data to be passed to
user space. Some drivers or library code did not set "pkt_type" or
"ip_summed". Also,  "__constant_htons()" should not be used for
runtime invocations, as pointed out by David Miller.

Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 35 insertions, 7 deletions

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 39b99f5..c3db111 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -366,17 +366,12 @@ void can_restart(unsigned long data)
 	can_flush_echo_skb(dev);
 
 	/* send restart message upstream */
-	skb = dev_alloc_skb(sizeof(struct can_frame));
+	skb = alloc_can_err_skb(dev, &cf);
 	if (skb == NULL) {
 		err = -ENOMEM;
 		goto restart;
 	}
-	skb->dev = dev;
-	skb->protocol = htons(ETH_P_CAN);
-	cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));
-	memset(cf, 0, sizeof(struct can_frame));
-	cf->can_id = CAN_ERR_FLAG | CAN_ERR_RESTARTED;
-	cf->can_dlc = CAN_ERR_DLC;
+	cf->can_id |= CAN_ERR_RESTARTED;
 
 	netif_rx(skb);
 
@@ -449,6 +444,39 @@ static void can_setup(struct net_device *dev)
 	dev->features = NETIF_F_NO_CSUM;
 }
 
+struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf)
+{
+	struct sk_buff *skb;
+
+	skb = netdev_alloc_skb(dev, sizeof(struct can_frame));
+	if (unlikely(!skb))
+		return NULL;
+
+	skb->protocol = htons(ETH_P_CAN);
+	skb->pkt_type = PACKET_BROADCAST;
+	skb->ip_summed = CHECKSUM_UNNECESSARY;
+	*cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));
+	memset(*cf, 0, sizeof(struct can_frame));
+
+	return skb;
+}
+EXPORT_SYMBOL_GPL(alloc_can_skb);
+
+struct sk_buff *alloc_can_err_skb(struct net_device *dev, struct can_frame **cf)
+{
+	struct sk_buff *skb;
+
+	skb = alloc_can_skb(dev, cf);
+	if (unlikely(!skb))
+		return NULL;
+
+	(*cf)->can_id = CAN_ERR_FLAG;
+	(*cf)->can_dlc = CAN_ERR_DLC;
+
+	return skb;
+}
+EXPORT_SYMBOL_GPL(alloc_can_err_skb);
+
 /*
  * Allocate and setup space for the CAN network device
  */