PF_AT_ADDR
snl_add_msg_attr_ip6(nw, PF_AT_ADDR, &addr->v.a.addr.v6);
{ .type = PF_AT_ADDR, .off = _OUT(v.a.addr), .cb = snl_attr_get_in6_addr },
{ .type = PF_AT_ADDR, .off = _OUT(v.a.addr), .cb = nlattr_get_in6_addr },
nlattr_add_in6_addr(nw, PF_AT_ADDR, &a->v.a.addr.v6);