On 10/14/22 11:45, Eric Dumazet wrote:

On Fri, Oct 14, 2022 at 9:39 AM Paul Gofman [off-list ref] wrote:

I think it is documented.

man 7 socket

        SO_REUSEADDR
               Indicates that the rules used in validating addresses
supplied in a bind(2) call should allow reuse of local addresses.  For
AF_INET sockets this means
               that a socket may bind, except when there is an active
listening socket bound to the address.  When the listening socket is
bound to INADDR_ANY with  a
               specific port then it is not possible to bind to this
port for any local address.  Argument is an integer boolean flag.

You seem to need another way, so you will have to ask this question in IETF.

Thanks a lot, I think it answers my question, I am afraid I was reading 
this a bit wrong.