Re: DHCP Automatic Configure at Driver Connect

["Cohen, Eugene" <eugene@hp.com>]

Jiaxin,

> Ip4Config2OnDhcp4SbInstalled() maybe confused you, but it's not accurate
> as you said "when the DHCP SB is installed you do a configure automatically".
> It's more proper to say "IPv4 driver is requiring DHCP SB due to it detects the
> DHCP policy." In such a case, it's reasonable with the function
> Ip4Config2OnDhcp4SbInstalled().

I see - my observation was based on the fact that removing this prevented the undesirable automatic configuration, but what you say makes sense.

> I agree with you this code did not exist in *Ip4Dxe* before. We implemented
> this function because of we need start the AutoConfig due to the DHCP
> policy is detected by Ip4Dxe driver (DHCP policy (note: NOT DHCP SB)
> together with D.O.R.A process). It does may appear AutoConfig straight away
> with DHCP SB if Ip4Dxe ahead of Dhcp4Dxe. But the precondition is that the
> DHCP policy has been detected.  If the policy is not DHCP during the system
> boot, I think your concern will not appear.

Are you saying the IP4 interface will not come "up" even for a static IP policy?  I was assuming it would in this case.  I'm not sure how big a deal this is because if there are no listeners or connections initiated it's kind of a don't-care - I think the only difference would be whether responses to ARP are provided.

> Now, compared to old Ip4Config behavior, we take 'ifconfig' tool command
> as example - "ifconfig -s eth0 dhcp":
> The Ip4Config->Start will be invoked to start the auto configuration. It was
> implemented in the deprecated driver -- Ip4ConfigDxe. When the system
> boot next time, the previous IP configuration will cleaned and the interface
> will be in UN-CONFIG status again.  Current implementation don't have this
> clean-up operation no matter Static/DHCP policy has been set. Is this the
> difference you mentioned?

Okay - this must be it - so DHCP magically turned back into "unconfigured" effectively creating the on-demand Configure() effect, at least for DHCP cases, that we now desire.  Interesting.

> Now, let us  consider your requirement:
> 1) The IP config information stored in NVRAM
> 2) A separate policy to delay the IP interface coming up until a component
> calls Configure ().
>
> #1 is also the current implementation. For 2), I remember you have one
> patch to do this implementation, can you share it to us for better
> understanding?

Yes, my first thought was to make the handling of Ip4Config2OnDhcp4SbInstalled conditional based on a PCD value (the policy in this case, would be in the PCD value).  Based on the limited experiment I did this seems to have the desired effect but based on your expertise perhaps there is a better location for such a check?

Thank you for patiently helping me with this - it's been enlightening to learn the history and thinking behind the config process.

Eugene