bonding: Add new layer2+3 hash for xor/802.3ad modes

 	Add new hash for balance-xor and 802.3ad modes.  Originally
 submitted by "Glenn Griffin" <ggriffin.kernel@gmail.com>; modified by
 Jay Vosburgh to move setting of hash policy out of line, tweak the
 documentation update and add version update to 3.2.2.

	Glenn's original comment follows:

Included is a patch for a new xmit_hash_policy for the bonding driver
that selects slaves based on MAC and IP information.  This is a middle
ground between what currently exists in the layer2 only policy and the
layer3+4 policy.  This policy strives to be fully 802.3ad compliant by
transmitting every packet of any particular flow over the same link.
As documented the layer3+4 policy is not fully compliant for extreme
cases such as ip fragmentation, so this policy is a nice compromise
for environments that require full compliance but desire more than the
layer2 only policy.

Signed-off-by: "Glenn Griffin" <ggriffin.kernel@gmail.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 27 insertions, 2 deletions

diff --git a/Documentation/networking/bonding.txt b/Documentation/networking/bonding.txt
index 11340625e36..6cc30e0d579 100644
--- a/Documentation/networking/bonding.txt
+++ b/Documentation/networking/bonding.txt
@@ -554,6 +554,30 @@ xmit_hash_policy
 
                 This algorithm is 802.3ad compliant.
 
+        layer2+3
+
+                This policy uses a combination of layer2 and layer3
+                protocol information to generate the hash.
+
+                Uses XOR of hardware MAC addresses and IP addresses to
+                generate the hash.  The formula is
+
+                (((source IP XOR dest IP) AND 0xffff) XOR
+                        ( source MAC XOR destination MAC ))
+                                modulo slave count
+
+                This algorithm will place all traffic to a particular
+                network peer on the same slave.  For non-IP traffic,
+                the formula is the same as for the layer2 transmit
+                hash policy.
+
+                This policy is intended to provide a more balanced
+                distribution of traffic than layer2 alone, especially
+                in environments where a layer3 gateway device is
+                required to reach most destinations.
+
+                This algorithm is 802.3ad complient.
+
         layer3+4
 
                 This policy uses upper layer protocol information,
@@ -589,8 +613,9 @@ xmit_hash_policy
                 or may not tolerate this noncompliance.
 
         The default value is layer2.  This option was added in bonding
-version 2.6.3.  In earlier versions of bonding, this parameter does
-not exist, and the layer2 policy is the only policy.
+        version 2.6.3.  In earlier versions of bonding, this parameter
+        does not exist, and the layer2 policy is the only policy.  The
+        layer2+3 value was added for bonding version 3.2.2.
 
 
 3. Configuring Bonding Devices