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, 2 insertions, 14 deletions

diff --git a/drivers/net/can/usb/ems_usb.c b/drivers/net/can/usb/ems_usb.c
index a65f56a9cd3..3685f3e42d1 100644
--- a/drivers/net/can/usb/ems_usb.c
+++ b/drivers/net/can/usb/ems_usb.c
@@ -311,14 +311,10 @@ static void ems_usb_rx_can_msg(struct ems_usb *dev, struct ems_cpc_msg *msg)
 	int i;
 	struct net_device_stats *stats = &dev->netdev->stats;
 
-	skb = netdev_alloc_skb(dev->netdev, sizeof(struct can_frame));
+	skb = alloc_can_skb(dev->netdev, &cf);
 	if (skb == NULL)
 		return;
 
-	skb->protocol = htons(ETH_P_CAN);
-
-	cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));
-
 	cf->can_id = msg->msg.can_msg.id;
 	cf->can_dlc = min_t(u8, msg->msg.can_msg.length, 8);
 
@@ -346,18 +342,10 @@ static void ems_usb_rx_err(struct ems_usb *dev, struct ems_cpc_msg *msg)
 	struct sk_buff *skb;
 	struct net_device_stats *stats = &dev->netdev->stats;
 
-	skb = netdev_alloc_skb(dev->netdev, sizeof(struct can_frame));
+	skb = alloc_can_err_skb(dev->netdev, &cf);
 	if (skb == NULL)
 		return;
 
-	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;
-	cf->can_dlc = CAN_ERR_DLC;
-
 	if (msg->type == CPC_MSG_TYPE_CAN_STATE) {
 		u8 state = msg->msg.can_state;