[PATCH] bonding: fix feature consolidation

This should resolve http://bugzilla.kernel.org/show_bug.cgi?id=5519

The current feature computation loses bits that it doesn't know about,
resulting in an inability to add VLANs and possibly other havoc.
Rewrote function to preserve bits it doesn't know about, remove an
unneeded state variable, and simplify the code.

Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 11 insertions, 21 deletions

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 8032126fd589..94cec3cf2a13 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1604,35 +1604,27 @@ static int bond_sethwaddr(struct net_device *bond_dev, struct net_device *slave_
         (NETIF_F_SG|NETIF_F_IP_CSUM|NETIF_F_NO_CSUM|NETIF_F_HW_CSUM)
 
 /* 
- * Compute the features available to the bonding device by 
- * intersection of all of the slave devices' BOND_INTERSECT_FEATURES.
- * Call this after attaching or detaching a slave to update the 
- * bond's features.
+ * Compute the common dev->feature set available to all slaves.  Some
+ * feature bits are managed elsewhere, so preserve feature bits set on
+ * master device that are not part of the examined set.
  */
 static int bond_compute_features(struct bonding *bond)
 {
-        int i;
+        unsigned long features = BOND_INTERSECT_FEATURES;
         struct slave *slave;
         struct net_device *bond_dev = bond->dev;
-        int features = bond->bond_features;
+        int i;
 
-        bond_for_each_slave(bond, slave, i) {
-                struct net_device * slave_dev = slave->dev;
-                if (i == 0) {
-                        features |= BOND_INTERSECT_FEATURES;
-                }
-                features &=
-                        ~(~slave_dev->features & BOND_INTERSECT_FEATURES);
-        }
+        bond_for_each_slave(bond, slave, i)
+                features &= (slave->dev->features & BOND_INTERSECT_FEATURES);
 
-        /* turn off NETIF_F_SG if we need a csum and h/w can't do it */
         if ((features & NETIF_F_SG) && 
-                !(features & (NETIF_F_IP_CSUM |
-                              NETIF_F_NO_CSUM |
-                              NETIF_F_HW_CSUM))) {
+            !(features & (NETIF_F_IP_CSUM |
+                          NETIF_F_NO_CSUM |
+                          NETIF_F_HW_CSUM)))
                 features &= ~NETIF_F_SG;
-        }
 
+        features |= (bond_dev->features & ~BOND_INTERSECT_FEATURES);
         bond_dev->features = features;
 
         return 0;
@@ -4561,8 +4553,6 @@ static int __init bond_init(struct net_device *bond_dev, struct bond_params *par
                                NETIF_F_HW_VLAN_RX |
                                NETIF_F_HW_VLAN_FILTER);
 
-        bond->bond_features = bond_dev->features;
-
 #ifdef CONFIG_PROC_FS
         bond_create_proc_entry(bond);
 #endif