From f5b2b966f032f22d3a289045a5afd4afa09f09c6 Mon Sep 17 00:00:00 2001 From: Jay Vosburgh Date: Fri, 22 Sep 2006 21:54:53 -0700 Subject: [PATCH] bonding: Validate probe replies in ARP monitor Add logic to check ARP request / reply packets used for ARP monitor link integrity checking. The current method simply examines the slave device to see if it has sent and received traffic; this can be fooled by extraneous traffic. For example, if multiple hosts running bonding are behind a common switch, the probe traffic from the multiple instances of bonding will update the tx/rx times on each other's slave devices. Signed-off-by: Jay Vosburgh Signed-off-by: Jeff Garzik --- Documentation/networking/bonding.txt | 59 ++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) (limited to 'Documentation/networking/bonding.txt') diff --git a/Documentation/networking/bonding.txt b/Documentation/networking/bonding.txt index afac780..dc942ea 100644 --- a/Documentation/networking/bonding.txt +++ b/Documentation/networking/bonding.txt @@ -192,6 +192,17 @@ or, for backwards compatibility, the option value. E.g., arp_interval Specifies the ARP link monitoring frequency in milliseconds. + + The ARP monitor works by periodically checking the slave + devices to determine whether they have sent or received + traffic recently (the precise criteria depends upon the + bonding mode, and the state of the slave). Regular traffic is + generated via ARP probes issued for the addresses specified by + the arp_ip_target option. + + This behavior can be modified by the arp_validate option, + below. + If ARP monitoring is used in an etherchannel compatible mode (modes 0 and 2), the switch should be configured in a mode that evenly distributes packets across all links. If the @@ -213,6 +224,54 @@ arp_ip_target maximum number of targets that can be specified is 16. The default value is no IP addresses. +arp_validate + + Specifies whether or not ARP probes and replies should be + validated in the active-backup mode. This 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. + + Possible values are: + + none or 0 + + No validation is performed. This is the default. + + active or 1 + + Validation is performed only for the active slave. + + backup or 2 + + Validation is performed only for backup slaves. + + all or 3 + + Validation is performed for all slaves. + + For the 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 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. + + This option 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 the arp_validate option can resolve this, as + the ARP monitor will only consider ARP requests and replies + associated with its own instance of bonding. + + This option was added in bonding version 3.1.0. + downdelay Specifies the time, in milliseconds, to wait before disabling -- cgit v1.1