R430 + Intel X710 (i40e) interface bonding

Hi,

Has anyone successful experience of the Intel X710 (i40e ethernet
driver) 10G interface bonding?

Everything we try comes up against failure, yet all the driver
releases say bonding is supported.

Using the stock RHEL6 driver, trying to get interfaces into a bond is met with:
bond1: option slaves: invalid value (-p1p1)

or when manually trying with ifenslave:
# ifenslave bond1 p1p1
Master 'bond1', Slave 'p1p1': Error: Enslave failed

strace on this shows:
ioctl(3, SIOCBONDENSLAVE, 0x7ffd6c35c560) = -1 EINVAL (Invalid argument)

If updating the drivers to 1.2.21(Dell) or 1.3.47 (Intel), whenever
the bond interface it brought up it causes a kernel panic, usually as
a result of the arping command that is executed when bringing the
interface up. The system then locks. (see below).

It seems to make no difference which method of bonding is used, the
outcome is exactly he same. also no different if bonding_opts includes
user_carrier=0.

Details:
RHEL/CentOS 6.7
Kernel: 2.6.32-573.8.1.el6.x86_64
NIC Firmware: 16.5.20
NIC Driver: 1.2.9-k (RHEL6) and 1.2.21 (Dell) and 1.3.47 (Intel)

Kernel panic:
<6>bond1: Enslaving p2p1 as an active interface with an up link
<1>BUG: unable to handle kernel NULL pointer dereference at 000000000000001c
<1>IP: [<ffffffffa02b4b57>] i40e_tx_map+0x77/0x4b0 [i40e]
<4>PGD 0
<4>Oops: 0002 [#1] SMP
<4>last sysfs file: /sys/devices/virtual/net/bond1/broadcast
<4>CPU 18
<4>Modules linked in: bonding i40e(U) ipv6 microcode sg joydev
ipmi_devintf iTCO_wdt iTCO_vendor_support dcdbas tg3 power_meter
acpi_ipmi ipmi_si ipmi_msghandler configfs ptp pps_core sb_edac
edac_core lpc_ich mfd_core shpchp ext4 jbd2 mbcache sr_mod cdrom
sd_mod crc_t10dif megaraid_sas ahci wmi dm_mirror dm_region_hash
dm_log dm_mod [last unloaded: i40e]
<4>
<4>Pid: 5959, comm: arping Not tainted 2.6.32-573.8.1.el6.x86_64 #1
Dell Inc. PowerEdge R430/