Creating a Makefile for **EiskaltDC++** to compile it for **OpenWrt** involves cross-compiling the software for the target architecture (e.g., MIPS, ARM, etc.) used by your OpenWrt device. Below is a step-by-step guide to create a Makefile for EiskaltDC++ in the OpenWrt build system.

---

### **1. Set Up OpenWrt Build Environment**
Before creating the Makefile, ensure you have set up the OpenWrt build environment on your system. Follow these steps:

1. **Install Dependencies**:
   ```bash
   sudo apt-get install build-essential libncurses5-dev gawk git libssl-dev gettext zlib1g-dev swig unzip time
   ```

2. **Clone OpenWrt Source Code**:
   ```bash
   git clone https://git.openwrt.org/openwrt/openwrt.git
   cd openwrt
   ```

3. **Update Feeds**:
   ```bash
   ./scripts/feeds update -a
   ./scripts/feeds install -a
   ```

4. **Configure the Build**:
   ```bash
   make menuconfig
   ```
   Select your target system (e.g., `Target System: Atheros AR7xxx/AR9xxx` for MIPS-based routers).

---

### **2. Create a Makefile for EiskaltDC++**
OpenWrt uses a specific format for Makefiles to build packages. Here’s an example Makefile for EiskaltDC++:

1. **Create a Directory for EiskaltDC++**:
   ```bash
   mkdir -p package/network/eiskaltdcpp
   cd package/network/eiskaltdcpp
   ```

2. **Create the Makefile**:
   Create a file named `Makefile` with the following content:

   ```makefile
   include $(TOPDIR)/rules.mk

   PKG_NAME:=eiskaltdcpp
   PKG_VERSION:=2.4.2
   PKG_RELEASE:=1

   PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
   PKG_SOURCE_URL:=https://github.com/eiskaltdcpp/eiskaltdcpp/archive/v$(PKG_VERSION).tar.gz
   PKG_HASH:=sha256_sum_of_the_tarball

   PKG_BUILD_DIR:=$(BUILD_DIR)/$(PKG_NAME)-$(PKG_VERSION)

   PKG_FIXUP:=autoreconf
   PKG_INSTALL:=1

   include $(INCLUDE_DIR)/package.mk

   define Package/eiskaltdcpp
     SECTION:=net
     CATEGORY:=Network
     TITLE:=EiskaltDC++ - Direct Connect client
     URL:=https://github.com/eiskaltdcpp/eiskaltdcpp
     DEPENDS:=+libstdcpp +libopenssl +zlib +libtinyxml2
   endef

   define Package/eiskaltdcpp/description
     EiskaltDC++ is a cross-platform program that uses the Direct Connect protocol.
   endef

   define Build/Configure
     $(call Build/Configure/Default,--with-openssl)
   endef

   define Package/eiskaltdcpp/install
     $(INSTALL_DIR) $(1)/usr/bin
     $(INSTALL_BIN) $(PKG_INSTALL_DIR)/usr/bin/eiskaltdcpp-* $(1)/usr/bin/
   endef

   $(eval $(call BuildPackage,eiskaltdcpp))
   ```

   Replace `sha256_sum_of_the_tarball` with the actual SHA256 hash of the source tarball.

---

### **3. Add EiskaltDC++ to OpenWrt Configuration**
1. **Update Feeds**:
   Ensure the package is recognized by OpenWrt:
   ```bash
   ./scripts/feeds update -a
   ./scripts/feeds install -a
   ```

2. **Enable EiskaltDC++ in Menuconfig**:
   ```bash
   make menuconfig
   ```
   Navigate to `Network -> EiskaltDC++` and enable it by pressing `M` (for module) or `Y` (to include it in the firmware).

---

### **4. Build EiskaltDC++**
1. **Compile the Package**:
   ```bash
   make package/network/eiskaltdcpp/compile V=s
   ```

2. **Locate the Compiled Package**:
   The compiled `.ipk` file will be located in `bin/packages/<target>/network/`.

---

### **5. Install EiskaltDC++ on OpenWrt**
1. **Transfer the `.ipk` File**:
   Use `scp` to transfer the `.ipk` file to your OpenWrt device:
   ```bash
   scp eiskaltdcpp_2.4.2-1_<target>.ipk root@<router_ip>:/tmp/
   ```

2. **Install the Package**:
   SSH into your OpenWrt device and install the package:
   ```bash
   opkg install /tmp/eiskaltdcpp_2.4.2-1_<target>.ipk
   ```

---

### **6. Run EiskaltDC++**
- Start EiskaltDC++ manually or configure it to run at boot.
- Use the command-line interface or a web interface (if available) to configure and use the client.

---

### **Notes**
- If EiskaltDC++ requires additional dependencies, ensure they are listed in the `DEPENDS` section of the Makefile.
- If you encounter issues during compilation, check the build logs in `logs/` for errors.

Let me know if you need further assistance!