bonding: document the new _arp options for arp_validate

CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/bonding.txt

@@ -270,16 +270,15 @@ arp_ip_target
 arp_validate
 
 	Specifies whether or not ARP probes and replies should be
-	validated in any mode that supports arp monitoring.  This causes
+	validated in any mode that supports arp monitoring, or whether
-	the ARP monitor to examine the incoming ARP requests and replies,
+	non-ARP traffic should be filtered (disregarded) for link
-	and only consider a slave to be up if it is receiving the
+	monitoring purposes.
-	appropriate ARP traffic.
 
 	Possible values are:
 
 	none or 0
 
-		No validation is performed.  This is the default.
+		No validation or filtering is performed.
 
 	active or 1
 
@@ -293,31 +292,68 @@ arp_validate
 
 		Validation is performed for all slaves.
 
-	For the active slave, the validation checks ARP replies to
+	filter or 4
-	confirm that they were generated by an arp_ip_target.  Since
-	backup slaves do not typically receive these replies, the
-	validation performed for backup slaves is on the ARP request
-	sent out via the active slave.  It is possible that some
-	switch or network configurations may result in situations
-	wherein the backup slaves do not receive the ARP requests; in
-	such a situation, validation of backup slaves must be
-	disabled.
 
-	The validation of ARP requests on backup slaves is mainly
+		Filtering is applied to all slaves. No validation is
-	helping bonding to decide which slaves are more likely to
+		performed.
-	work in case of the active slave failure, it doesn't really
-	guarantee that the backup slave will work if it's selected
-	as the next active slave.
 
-	This option is useful in network configurations in which
+	filter_active or 5
-	multiple bonding hosts are concurrently issuing ARPs to one or
+
-	more targets beyond a common switch.  Should the link between
+		Filtering is applied to all slaves, validation is performed
-	the switch and target fail (but not the switch itself), the
+		only for the active slave.
-	probe traffic generated by the multiple bonding instances will
+
-	fool the standard ARP monitor into considering the links as
+	filter_backup or 6
-	still up.  Use of the arp_validate option can resolve this, as
+
-	the ARP monitor will only consider ARP requests and replies
+		Filtering is applied to all slaves, validation is performed
-	associated with its own instance of bonding.
+		only for backup slaves.
+
+	Validation:
+
+	Enabling validation causes the ARP monitor to examine the incoming
+	ARP requests and replies, and only consider a slave to be up if it
+	is receiving the appropriate ARP traffic.
+
+	For an active slave, the validation checks ARP replies to confirm
+	that they were generated by an arp_ip_target.  Since backup slaves
+	do not typically receive these replies, the validation performed
+	for backup slaves is on the broadcast ARP request sent out via the
+	active slave.  It is possible that some switch or network
+	configurations may result in situations wherein the backup slaves
+	do not receive the ARP requests; in such a situation, validation
+	of backup slaves must be disabled.
+
+	The validation of ARP requests on backup slaves is mainly helping
+	bonding to decide which slaves are more likely to work in case of
+	the active slave failure, it doesn't really guarantee that the
+	backup slave will work if it's selected as the next active slave.
+
+	Validation is useful in network configurations in which multiple
+	bonding hosts are concurrently issuing ARPs to one or more targets
+	beyond a common switch.  Should the link between the switch and
+	target fail (but not the switch itself), the probe traffic
+	generated by the multiple bonding instances will fool the standard
+	ARP monitor into considering the links as still up.  Use of
+	validation can resolve this, as the ARP monitor will only consider
+	ARP requests and replies associated with its own instance of
+	bonding.
+
+	Filtering:
+
+	Enabling filtering causes the ARP monitor to only use incoming ARP
+	packets for link availability purposes.  Arriving packets that are
+	not ARPs are delivered normally, but do not count when determining
+	if a slave is available.
+
+	Filtering operates by only considering the reception of ARP
+	packets (any ARP packet, regardless of source or destination) when
+	determining if a slave has received traffic for link availability
+	purposes.
+
+	Filtering is useful in network configurations in which significant
+	levels of third party broadcast traffic would fool the standard
+	ARP monitor into considering the links as still up.  Use of
+	filtering can resolve this, as only ARP traffic is considered for
+	link availability purposes.
 
 	This option was added in bonding version 3.1.0.