IP_FREEBIND (since Linux 2.4)
If enabled, this boolean option allows binding to an IP address that is nonlocal or does not (yet) exist. This permits listening on a socket, without requiring the underlying network interface or the specified dynamic IP address to be up at the time that the application is trying to
bind to it. This option is the per-socket equivalent of the ip_nonlocal_bind /proc interface described below.
I understand that binding to ipv6 addresses that haven't finished Duplicate Address Detection causes the bind() to fail.
http:// www.freedesktop .org/wiki/ Software/ systemd/ NetworkTarget/ suggests using IP_FREEBIND:
IP_FREEBIND (since Linux 2.4)
address that is nonlocal or does not (yet) exist. This
permits listening on a socket, without requiring the
underlying network interface or the specified dynamic IP
address to be up at the time that the application is trying to
ip_nonlocal_ bind /proc interface described below.
If enabled, this boolean option allows binding to an IP
bind to it. This option is the per-socket equivalent of the