[NET]: Share correct feature code between bridging and bonding

http://bugzilla.kernel.org/show_bug.cgi?id=8797 shows that the
bonding driver may produce bogus combinations of the checksum
flags and SG/TSO.

For example, if you bond devices with NETIF_F_HW_CSUM and
NETIF_F_IP_CSUM you'll end up with a bonding device that
has neither flag set.  If both have TSO then this produces
an illegal combination.

The bridge device on the other hand has the correct code to
deal with this.

In fact, the same code can be used for both.  So this patch
moves that logic into net/core/dev.c and uses it for both
bonding and bridging.

In the process I've made small adjustments such as only
setting GSO_ROBUST if at least one constituent device
supports it.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 4a616d73cc25..e679b2751665 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1131,6 +1131,8 @@ extern void dev_seq_stop(struct seq_file *seq, void *v);
 
 extern void linkwatch_run_queue(void);
 
+extern int netdev_compute_features(unsigned long all, unsigned long one);
+
 static inline int net_gso_ok(int features, int gso_type)
 {
         int feature = gso_type << NETIF_F_GSO_SHIFT;