[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 <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

drivers/net/bonding/bond_main.c

···
 	(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;
···
 	bond_dev->features |= (NETIF_F_HW_VLAN_TX |
 			       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);

drivers/net/bonding/bonding.h

···
 #include "bond_3ad.h"
 #include "bond_alb.h"
 
-#define DRV_VERSION	"2.6.4"
-#define DRV_RELDATE	"September 26, 2005"
+#define DRV_VERSION	"2.6.5"
+#define DRV_RELDATE	"November 4, 2005"
 #define DRV_NAME	"bonding"
 #define DRV_DESCRIPTION	"Ethernet Channel Bonding Driver"
 
···
 	struct   bond_params params;
 	struct   list_head vlan_list;
 	struct   vlan_group *vlgrp;
-	/* the features the bonding device supports, independently 
-	 * of any slaves */
-	int	 bond_features; 
 };
 
 /**