bonding: xor/802.3ad improved slave hash

Add support for alternate slave selection algorithms to bonding
balance-xor and 802.3ad modes.  Default mode (what we have now: xor of
MAC addresses) is "layer2", new choice is "layer3+4", using IP and port
information for hashing to select peer.

Originally submitted by Jason Gabler for balance-xor mode;
modified by Jay Vosburgh to additionally support 802.3ad mode.  Jason's
original comment is as follows:

The attached patch to the Linux Etherchannel Bonding driver modifies the
driver's "balance-xor" mode as follows:

      - alternate hashing policy support for mode 2
        * Added kernel parameter "xmit_policy" to allow the specification
          of different hashing policies for mode 2.  The original mode 2
          policy is the default, now found in xmit_hash_policy_layer2().
        * Added xmit_hash_policy_layer34()

This patch was inspired by hashing policies implemented by Cisco,
Foundry and IBM, which are explained in
Foundry documentation found at:
http://www.foundrynet.com/services/documentation/sribcg/Trunking.html#112750

Signed-off-by: Jason Gabler <jygabler@lbl.gov>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>

include/linux/if_bonding.h

@@ -35,6 +35,9 @@
  *
  * 2003/12/01 - Shmulik Hen <shmulik.hen at intel dot com>
  *	- Code cleanup and style changes
+ *
+ * 2005/05/05 - Jason Gabler <jygabler at lbl dot gov>
+ *      - added definitions for various XOR hashing policies
  */
 
 #ifndef _LINUX_IF_BONDING_H
@@ -80,6 +83,10 @@
 
 #define BOND_DEFAULT_MAX_BONDS  1   /* Default maximum number of devices to support */
 
+/* hashing types */
+#define BOND_XMIT_POLICY_LAYER2		0 /* layer 2 (MAC only), default */
+#define BOND_XMIT_POLICY_LAYER34	1 /* layer 3+4 (IP ^ MAC) */
+
 typedef struct ifbond {
 	__s32 bond_mode;
 	__s32 num_slaves;