> On 20 Mar 2017, at 20:25, Jon Loeliger <j...@netgate.com> wrote:
>
> Folks,
>
> I am trying to understand a bit more about the "host" interface
> for some AF_PACKET interfaces.
>
> Currently, there is a single API call to create an AF_PACKET interface.
> It simultaneously sets the HW_ADDR (ie, MAC address) of the interface
> to either user-specified value, or a randomly generated value.
>
> I'd like to separate the two steps, or at the very least, be able to set
> the MAC address in a separate API call that isn't the initial CREATE call.
> Why? Imagine the sequence of commands that might look like this:
>
> # interface host fred
> # mac 11:22:33:44:55:66
> # no shutdown
> # exit
>
> So, at the time of "interface host fred", we'd like to cause the interface
> to be created, but the MAC isn't really available yet. Then later, when
> we see the "mac ...." line, we'd like to set, or change, the MAC with the
> new user-supplied value.
>
> In the case of a "normal" or DPDK interface, the VNET_DEVICE_CLASS
> functions specify a .mac_addr_change_function. Roughly from
> src/plugins/dpdk/device/device.c lines 774 or so:
>
> VNET_DEVICE_CLASS (dpdk_device_class) = {
> .mac_addr_change_function = dpdk_set_mac_address,
> };
>
> That's all well and good.
>
> Naturally, no such mac_addr_change_function exists for the
> AF_PACKET device class.
>
> My question is: Is there a fundamental reason that prevents such
> a function from being written, or is it a case of simply "we just haven't
> gotten to that detail yet”?
If I remember correctly mac_addr_change_function is optional callback
for interfaces which need to do some special work when mac address is changed.
DPDK is such change as we need to call rte_eth_dev_default_mac_addr_set DPDK
API.
as AF_PACKET doesn’t need to do any special work, it is not defined.
So what are you asking should simply work, have you tried "set interface mac
address” CLI?
> The latter case implying that someone
> could actually achieve a MAC addr change on the AF_PACKET
> interface, if an enterprising young engineer were to, say, write a new
> API function to get there.
>
> So, yeah, I know the actual MAC might not be really important, but
> maybe the user is trying to match some external requirement or so?
> I don't know.
>
> Thoughts?
> jdl
>
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