[PATCH net-next 0/6] bonding: only rely on arp packets if arp monitor is used

[Veaceslav Falico <vfalico@redhat.com>]

Hi,

Currently, if arp_validate is off (0), slave_last_rx() returns the
slave->dev->last_rx, which is always updated on *any* packet received by
slave, and not only arps. This means that, if the validation of arps is
off, we're treating *any* incoming packet as a proof of slave being up, and
not only arps.

This might seem logical at the first glance, however it can cause a lot of
troubles and false-positives, one example would be:

The arp_ip_target is NOT accessible, however someone in the broadcast domain
spams with any broadcast traffic. This way bonding will be tricked that the
slave is still up (as in - can access arp_ip_target), while it's not.

The documentation for arp_validate also states that *ARPs* will (not) be
validated if it's on/off, and that the arp monitoring works on arps as
traffic generators.

Also, the net_device->last_rx is already used in a lot of drivers (even
though the comment states to NOT do it :)), and it's also ugly to modify it
from bonding.

So, to fix this, remove the last_rx from bonding, *always* call
bond_arp_rcv() in slave's rx_handler (bond_handle_frame), and if we spot an
arp there - update the slave->last_arp_rx - and use it instead of
net_device->last_rx. Finally, rename slave_last_rx() to slave_last_arp_rx()
to reflect the changes.

As the changes touch really sensitive parts, I've tried to split them as
much as possible, for easier debugging/bisecting.

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

---
 drivers/net/bonding/bond_main.c    | 18 ++++++++----------
 drivers/net/bonding/bond_options.c | 12 ++----------
 drivers/net/bonding/bonding.h      | 16 ++++++----------
 include/linux/netdevice.h          |  8 +-------
 4 files changed, 17 insertions(+), 37 deletions(-)