feat: 添加切换为 DHCP 自动获取 IP 功能

- 在主菜单新增选项3：切换为 DHCP 自动获取 IP
- 支持 NetworkManager、netplan、传统 interfaces 三种网络管理方式
- 自动备份原有网络配置
- 切换前显示警告提示

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

setup_cups.sh

@@ -447,6 +447,169 @@ EOF
     success "传统网络配置完成"
 }
 
+# 配置 DHCP 自动获取 IP
+configure_dhcp() {
+    echo ""
+    echo -e "${YELLOW}═══════════════════════════════════════════════════════════${NC}"
+    echo -e "${YELLOW}                 切换为 DHCP 自动获取 IP                    ${NC}"
+    echo -e "${YELLOW}═══════════════════════════════════════════════════════════${NC}"
+    echo ""
+
+    local current_ip=$(get_ip)
+    local current_interface=$(get_interface)
+
+    echo -e "${BLUE}当前网络配置:${NC}"
+    echo "  接口名称: $current_interface"
+    echo "  当前 IP:  $current_ip"
+    echo ""
+
+    echo -e "${YELLOW}警告: 切换为 DHCP 后，IP 地址可能会改变！${NC}"
+    echo "  请确保你能通过其他方式（如显示器/串口）访问设备"
+    echo ""
+    read -p "确定要切<E8A681><E58887>为 DHCP 吗? [y/N]: " confirm < /dev/tty
+    confirm=${confirm:-N}
+
+    if [[ ! "$confirm" =~ ^[Yy]$ ]]; then
+        echo "已取消"
+        return 0
+    fi
+
+    # 检查是否使用 NetworkManager
+    if systemctl is-active --quiet NetworkManager 2>/dev/null; then
+        configure_dhcp_networkmanager "$current_interface"
+    # 检查是否使用 netplan (Ubuntu 18.04+)
+    elif [ -d /etc/netplan ]; then
+        configure_dhcp_netplan "$current_interface"
+    # 使用传统的 /etc/network/interfaces
+    else
+        configure_dhcp_interfaces "$current_interface"
+    fi
+
+    show_dhcp_result
+}
+
+# 使用 NetworkManager 配置 DHCP
+configure_dhcp_networkmanager() {
+    local iface=$1
+
+    info "检测到 NetworkManager，使用 nmcli 配置 DHCP..."
+
+    # 获取连接名称
+    local conn_name=$(nmcli -t -f NAME,DEVICE con show --active | grep "$iface" | cut -d':' -f1)
+
+    if [ -z "$conn_name" ]; then
+        conn_name="$iface"
+    fi
+
+    # 配置 DHCP
+    nmcli con mod "$conn_name" ipv4.method auto
+    nmcli con mod "$conn_name" ipv4.addresses ""
+    nmcli con mod "$conn_name" ipv4.gateway ""
+    nmcli con mod "$conn_name" ipv4.dns ""
+
+    # 重启连接
+    nmcli con down "$conn_name" 2>/dev/null || true
+    nmcli con up "$conn_name"
+
+    success "NetworkManager DHCP 配置完成"
+}
+
+# 使用 netplan 配置 DHCP
+configure_dhcp_netplan() {
+    local iface=$1
+
+    info "检测到 netplan，创建 DHCP 配置..."
+
+    # 备份现有配置
+    for f in /etc/netplan/*.yaml; do
+        if [ -f "$f" ]; then
+            cp "$f" "$f.bak"
+            info "已备份: $f -> $f.bak"
+        fi
+    done
+
+    # 创建新的 netplan DHCP 配置
+    cat > /etc/netplan/01-dhcp.yaml << EOF
+# DHCP 配置 - 由 CUPS 一键脚本生成
+network:
+  version: 2
+  renderer: networkd
+  ethernets:
+    $iface:
+      dhcp4: yes
+EOF
+
+    # 设置正确的权限
+    chmod 600 /etc/netplan/01-dhcp.yaml
+
+    # 删除其他可能冲突的配置
+    for f in /etc/netplan/*.yaml; do
+        if [ "$f" != "/etc/netplan/01-dhcp.yaml" ] && [ -f "$f" ]; then
+            rm -f "$f"
+            info "移除冲突配置: $f"
+        fi
+    done
+
+    # 应用配置
+    info "应用 netplan 配置..."
+    netplan apply
+
+    success "Netplan DHCP 配置完成"
+}
+
+# 使用传统 interfaces 文件配置 DHCP
+configure_dhcp_interfaces() {
+    local iface=$1
+
+    info "使用传统 /etc/network/interfaces 配置 DHCP..."
+
+    # 备份原配置
+    if [ -f /etc/network/interfaces ]; then
+        cp /etc/network/interfaces /etc/network/interfaces.bak
+        info "已备份: /etc/network/interfaces -> /etc/network/interfaces.bak"
+    fi
+
+    # 创建新配置
+    cat > /etc/network/interfaces << EOF
+# DHCP 配置 - 由 CUPS 一键脚本生成
+# 备份文件: /etc/network/interfaces.bak
+
+# 本地回环接口
+auto lo
+iface lo inet loopback
+
+# 主网络接口 - DHCP
+auto $iface
+iface $iface inet dhcp
+EOF
+
+    # 重启网络服务
+    info "重启网络服务..."
+    systemctl restart networking 2>/dev/null || /etc/init.d/networking restart 2>/dev/null || true
+
+    success "传统网络配置完成"
+}
+
+# 显示 DHCP 配置结果
+show_dhcp_result() {
+    # 等待网络重新配置
+    sleep 3
+    local new_ip=$(get_ip)
+    local new_interface=$(get_interface)
+
+    echo ""
+    echo -e "${GREEN}╔══════════════════════════════════════════════════════════╗${NC}"
+    echo -e "${GREEN}║              DHCP 配置完成!                              ║${NC}"
+    echo -e "${GREEN}╚══════════════════════════════════════════════════════════╝${NC}"
+    echo ""
+    echo -e "  ${BLUE}网络接口:${NC} $new_interface"
+    echo -e "  ${BLUE}当前 IP:${NC}  $new_ip"
+    echo ""
+    echo -e "  ${YELLOW}注意:${NC} IP 地址现在由 DHCP 服务器自动分配"
+    echo -e "  ${YELLOW}      ${NC} 重启后 IP 可能会改变"
+    echo ""
+}
+
 # 显示静态IP配置结果
 show_static_ip_result() {
     local new_ip=$(get_ip)
@@ -1266,9 +1429,10 @@ show_menu() {
     echo ""
     echo "    1) 安装 CUPS 打印服务"
     echo "    2) 卸载 CUPS 打印服务"
+    echo "    3) 切换为 DHCP 自动获取 IP"
     echo "    0) 退出"
     echo ""
-    read -p "  请输入选项 [1/2/0]: " choice < /dev/tty
+    read -p "  请输入选项 [1/2/3/0]: " choice < /dev/tty
 
     case "$choice" in
         1)
@@ -1277,6 +1441,13 @@ show_menu() {
         2)
             uninstall
             ;;
+        3)
+            check_root
+            configure_dhcp
+            echo ""
+            read -p "按 Enter 返回主菜单..." < /dev/tty
+            show_menu
+            ;;
         0)
             echo "已退出"
             exit 0