what do jails map 127.0.0.1 to?

[Rick Macklem]

Bjoern A. Zeeb wrote:
>On 11 Feb 2019, at 0:50, Rick Macklem wrote:
>> I am finally back to looking at an old PR#205193.
>>
>> The problem is that the nfsuserd daemon expects upcalls from the
>> kernel
>> that are from localhost (127.0.0.1) and when jails are running on the
>> system,
>> 127.0.0.1 is mapped to some other IP#. (I think it might be the
>> address of the
>> first net interface on the machine, but I'm not sure?)
>
>And what does it do on system that have no 127.1 or no IPv4 at all
>anymore or don’t even support IPv4 anymore?
It doesn't work. It uses UDP over IPv4 for the upcalls.

>> Is there a way that nfsuserd.c can find out what this IP# is?
>
>Yes, could do easily but wouldn’t work for my above case, would it?  I
>can help you with the code for v4 and jails if you help me with the code
>for IPv6?
I suspect the main trick is how it can figure out that it needs to use IPv6 instead of
IPv4? (If there is no easy way, I suppose it could be a command option.)

rick
ps: The kernel RPC knows what it calls "udp6". I never really understood how to
      tell when an IPv6 address is from the local machine? (I'll admit I never use
      IPv6, so I don't even know if NFS works on it. I just assume someone would
      complain if it didn't work.)