Why does OpenBMC use Avahi mDNS instead of SSDP?

[Gunnar Mills]

On 4/8/2020 3:27 PM, Joseph Reynolds wrote:
> On 4/7/20 10:46 AM, Patrick Williams wrote:
>> On Tue, Apr 07, 2020 at 09:58:15AM -0500, Joseph Reynolds wrote:
>>> Redfish specifies SSDP [1] [2] as the standard discovery service but
>>> OpenBMC uses the Avahi mDNS discovery service [3].  I asked Redfish to
>>> add mDNS to the spec [4] but they don't want to, and pointed to 
>>> their spec.
>>
>> mDNS is used more in the UNIX world, SSDP is used more in Windows.
>>
Was on the Redfish call earlier and this forum thread was discussed. The 
Redfish members on the call did not totally agree with this statement. 
They believe SSDP has a wider adaption than just Windows. A wider 
adaption than mDNS.  Since SSDP is already in the Redfish specification 
and has been adapted by Redfish implementations, adding a 2nd discovery 
service would damage interoperability in Redfish.
The members on the call really wanted to encourage OpenBMC to implement 
SSDP instead.
Posted the same to the forum thread.


>
>>> I want to allow the BMC admin to enable and disable the mDNS discovery
>>> service.  How can this be done?  Options:
>>> 1. Implement ManagerNetworkProtocol.Oem.OpenBMC.mDNS.
>>> 2. Move OpenBMC to SSDP and away from mDNS.
>>> 3. Re-ask Redfish to add a ManagerNetworkProtocol.mDNS protocol.
>> I don't see a strong reason to "move away" from mDNS, but I certainly
>> think that *any* network service should be able to be disabled by an
>> administrator to reduce the security footprint if the service is unused.
>>
>> So, either #1 or #3 seems best to me.  Adding optional SSDP support 
>> would
>> be reasonable, but likely only to be added by someone who cares about
>> discovery in a Windows environment.
>
> I've appended the thread to re-ask Redfish if they would support 
> ManagerNetworkProtocol.mDNS.
> https://redfishforum.com/thread/267/add-avahi-managernetworkprotocol
>
If think we are down to #1 or #2.

Thanks,
Gunnar