netdev - Re: Question on Bonding driver

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Date:	Sat, 14 Feb 2015 08:25:33 -0800
From:	Jay Vosburgh <jay.vosburgh@...onical.com>
To:	Murali Karicheri <m-karicheri2@...com>
cc:	netdev <netdev@...r.kernel.org>, WingMan Kwok <w-kwok2@...com>
Subject: Re: Question on Bonding driver

Murali Karicheri <m-karicheri2@...com> wrote:

>Hi,
>
>I am working to enable bonding driver on my hardware and trying to
>understand this.
>
>I am using the alb mode. I create a bond interface with 2 ethernet
>interfaces. First one is the basic question about net driver itself and
>second is about bonding.
>
>1. Each ethernet interface has a MAC address. The hardware has MAC filter
>and the driver fills the net_device's dev_addr with its MAC address before
>calling register_netdev() API. When the net core calls ndo_start(), is the
>low level driver responsible for setting up its MAC address in the MAC
>filter of the hardware or low level driver will be told to do so by upper
>layer. Or is it required to set it up as part of ndo_set_rx_mode() or
>ndo_set_mac_address()?
>
>2. In the case of bonding, the bond interface MAC address is copied from
>the active slave's MAC address. Also it updates the dev_addr in the netdev
>struct of each of the slave with its own MAC address. So I assume, the
>device/NIC now needs to accept packets to its original MAC address as well
>the bond's MAC address. This is especially more important for the slave's
>that are not active slave as it can be target of packets from Peers as
>part of rlb. So for the slave that is not active slave, MAC filter needs
>to include its original hw address as well unless the slave is put to
>promiscuous mode. So I am trying to figure out how this is expected to
>work? All slaves put to promiscuous mode or MAC filter updated by slave
>driver to include MAC addresses it is expected to filter on (bond MAC
>address and its own MAC address)

	I'm travelling at the moment, but the short answer for #2 is
that the way the alb mode works is basically that the non-active slaves
only receive for their own individual MAC.  Peers within the L2 network
are "assigned" to those slaves via tailored ARPs sent to the specific
peers.  The slaves do not generally go into promisc mode (there are
exceptions during failover type events), nor are they programmed with
multiple unicast MAC addreeses.

	I'd suggest you look at rlb_update_client in bond_alb.c and the
functions that call it to understand the logic.

	-J

---
	-Jay Vosburgh, jay.vosburgh@...onical.com


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