Anchoring compared the full socket, so a peer answering from a source port
other than the one we send to was refused: its name resolved to the right
host, but the port differed and every frame was discarded. NAT rewrites that
port, and a peer needs not bind the port it is reached on.
A name now pins the host only. The wire may still refine the port within
that host, and a re-resolution that moves the peer elsewhere drops a port
learned for the host it just left.
A name that has never resolved anchors nothing. normalize_obp_config leaves
TARGET_SOCK as (None, port) when startup resolution fails, and anchoring on
that refused every source forever, taking the link off the air until the
process restarted. Those bridges fall back to RELAX_CHECKS instead.