In the general case the current behavior is random and not something+1
applications can count on, and we would do well to fix it so it is less
random. In particular consider the case of an application in a
non-initial network namespace creating a new network namespace. It is
not even possible to predict what values they will get for sysctls
today.
From a backwards compatibility standpoint we are probably better off+1
with copying from the current network namespace rather than the initial
network namespace. As that more closely resembles the common case
today.