can: fix WARN_ON dump in net/core/rtnetlink.c:rtmsg_ifinfo()

On older kernels, e.g. 2.6.27, a WARN_ON dump in rtmsg_ifinfo()
is thrown when the CAN device is registered due to insufficient
skb space, as reported by various users. This patch adds the
rtnl_link_ops "get_size" to fix the problem. I think this patch
is required for more recent kernels as well, even if no WARN_ON
dumps are triggered. Maybe we also need "get_xstats_size" for
the CAN xstats.

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

1 files changed, 17 insertions, 0 deletions

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index f0b9a1e1db46..564e31c9fee4 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -589,6 +589,22 @@ static int can_changelink(struct net_device *dev,
         return 0;
 }
 
+static size_t can_get_size(const struct net_device *dev)
+{
+        struct can_priv *priv = netdev_priv(dev);
+        size_t size;
+
+        size = nla_total_size(sizeof(u32));   /* IFLA_CAN_STATE */
+        size += sizeof(struct can_ctrlmode);  /* IFLA_CAN_CTRLMODE */
+        size += nla_total_size(sizeof(u32));  /* IFLA_CAN_RESTART_MS */
+        size += sizeof(struct can_bittiming); /* IFLA_CAN_BITTIMING */
+        size += sizeof(struct can_clock);     /* IFLA_CAN_CLOCK */
+        if (priv->bittiming_const)            /* IFLA_CAN_BITTIMING_CONST */
+                size += sizeof(struct can_bittiming_const);
+
+        return size;
+}
+
 static int can_fill_info(struct sk_buff *skb, const struct net_device *dev)
 {
         struct can_priv *priv = netdev_priv(dev);
@@ -639,6 +655,7 @@ static struct rtnl_link_ops can_link_ops __read_mostly = {
         .setup          = can_setup,
         .newlink        = can_newlink,
         .changelink     = can_changelink,
+        .get_size       = can_get_size,
         .fill_info      = can_fill_info,
         .fill_xstats    = can_fill_xstats,
 };