Add query_interface configuration for binding IP queries to specific network interfaces

README.md

@@ -72,6 +72,7 @@
   - [Miscellaneous topics](#miscellaneous-topics)
     - [IPv6 support](#ipv6-support)
     - [Network interface IP address](#network-interface-ip-address)
+    - [Query IP through specific network interface](#query-ip-through-specific-network-interface)
     - [SOCKS5 proxy support](#socks5-proxy-support)
     - [Display debug info](#display-debug-info)
     - [Obtain IP from RouterOS](#obtain-ip-from-router-os)
@@ -1190,6 +1191,32 @@ With `interface-name` replaced by the name of the network interface, e.g. `eth0`
 
 Note: If `ip_urls` is also specified, it will be used to perform an online lookup first and the network interface IP will be used as a fallback in case of failure.
 
+#### Query IP through specific network interface
+
+If you have multiple network interfaces and want to query your public IP address through a specific interface (useful when you have multiple uplinks, some behind CGNAT and others with public IPs), you can use the `query_interface` configuration option:
+
+```json
+  "query_interface": "wan0",
+```
+
+With `wan0` replaced by the name of the network interface you want to use for querying the IP address. When this option is set, GoDNS will bind the HTTP request to the specified network interface, ensuring the IP query goes through that interface rather than the default route.
+
+This is particularly useful in scenarios where:
+- You have multiple WAN connections with different routing priorities
+- One interface is behind CGNAT while another has a public IP
+- You want to ensure the IP query reflects the actual public IP of a specific interface
+
+Example configuration for dual-WAN setup:
+```json
+{
+  "ip_urls": ["https://api.ipify.org/"],
+  "query_interface": "wan0",
+  "ip_type": "IPv4"
+}
+```
+
+Note: The `query_interface` option is different from `ip_interface`. The `query_interface` specifies which interface to use when making the HTTP request to query your public IP, while `ip_interface` reads the IP address directly from the local interface without making any external requests.
+
 #### SOCKS5 proxy support
 
 You can make all remote calls go through a [SOCKS5 proxy](https://en.wikipedia.org/wiki/SOCKS#SOCKS5) by specifying it in the configuration file this way:

README_CN.md

@@ -70,6 +70,7 @@
   - [杂项主题](#杂项主题)
     - [IPv6 支持](#ipv6-支持)
     - [网络接口 IP 地址](#网络接口-ip-地址)
+    - [通过特定网络接口查询 IP](#通过特定网络接口查询-ip)
     - [SOCKS5 代理支持](#socks5-代理支持)
     - [显示调试信息](#显示调试信息)
     - [从 RouterOS 获取 IP](#从-routeros-获取-ip)
@@ -1188,6 +1189,32 @@ http://localhost:5000/api/v1/send?domain=ddns.example.com&ip=192.168.1.1&ip_type
 
 注意：如果也指定了 `ip_urls`，它将首先用于执行在线查找，网络接口 IP 将在失败情况下用作后备。
 
+#### 通过特定网络接口查询 IP
+
+如果您有多个网络接口，并希望通过特定接口查询公共 IP 地址（在有多个上行链路时很有用，其中一些在 CGNAT 后面，而其他的有公共 IP），您可以使用 `query_interface` 配置选项：
+
+```json
+  "query_interface": "wan0",
+```
+
+将 `wan0` 替换为要用于查询 IP 地址的网络接口名称。设置此选项后，GoDNS 将 HTTP 请求绑定到指定的网络接口，确保 IP 查询通过该接口而不是默认路由。
+
+这在以下场景中特别有用：
+- 您有多个具有不同路由优先级的 WAN 连接
+- 一个接口在 CGNAT 后面，而另一个有公共 IP
+- 您想确保 IP 查询反映特定接口的实际公共 IP
+
+双 WAN 设置的示例配置：
+```json
+{
+  "ip_urls": ["https://api.ipify.org/"],
+  "query_interface": "wan0",
+  "ip_type": "IPv4"
+}
+```
+
+注意：`query_interface` 选项与 `ip_interface` 不同。`query_interface` 指定进行 HTTP 请求查询公共 IP 时使用哪个接口，而 `ip_interface` 直接从本地接口读取 IP 地址，不进行任何外部请求。
+
 #### SOCKS5 代理支持
 
 您可以通过在配置文件中指定 [SOCKS5 代理](https://en.wikipedia.org/wiki/SOCKS#SOCKS5) 来使所有远程调用通过该代理：

configs/config_multi_sample.yaml

@@ -46,6 +46,7 @@ interval: 300
 resolver: 8.8.8.8
 user_agent: "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.111 Safari/537.36"
 ip_interface: eth0
+query_interface:
 
 mikrotik:
   enabled: false

configs/config_sample.json

@@ -31,6 +31,7 @@
   "resolver": "8.8.8.8",
   "user_agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.111 Safari/537.36",
   "ip_interface": "eth0",
+  "query_interface": "",
   "mikrotik": {
     "enabled": false,
     "addr": "http://192.168.88.1:81",

configs/config_sample.yaml

@@ -25,6 +25,7 @@ interval: 300
 resolver: 8.8.8.8
 user_agent: "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2125.111 Safari/537.36"
 ip_interface: eth0
+query_interface:
 mikrotik:
   enabled: false
   addr: "http://192.168.20.1:81"

internal/settings/settings.go

@@ -172,13 +172,14 @@ type Settings struct {
 	Domains []Domain `json:"domains" yaml:"domains"`
 
 	// Network and IP configuration
-	IPUrl       string   `json:"ip_url" yaml:"ip_url"`
-	IPUrls      []string `json:"ip_urls" yaml:"ip_urls"`
-	IPV6Url     string   `json:"ipv6_url" yaml:"ipv6_url"`
-	IPV6Urls    []string `json:"ipv6_urls" yaml:"ipv6_urls"`
-	IPInterface string   `json:"ip_interface" yaml:"ip_interface"`
-	IPType      string   `json:"ip_type" yaml:"ip_type"`
-	Resolver    string   `json:"resolver" yaml:"resolver"`
+	IPUrl          string   `json:"ip_url" yaml:"ip_url"`
+	IPUrls         []string `json:"ip_urls" yaml:"ip_urls"`
+	IPV6Url        string   `json:"ipv6_url" yaml:"ipv6_url"`
+	IPV6Urls       []string `json:"ipv6_urls" yaml:"ipv6_urls"`
+	IPInterface    string   `json:"ip_interface" yaml:"ip_interface"`
+	QueryInterface string   `json:"query_interface" yaml:"query_interface"`
+	IPType         string   `json:"ip_type" yaml:"ip_type"`
+	Resolver       string   `json:"resolver" yaml:"resolver"`
 
 	// Application configuration
 	Interval      int    `json:"interval" yaml:"interval"`

internal/settings/settings_test.go

@@ -81,3 +81,27 @@ func TestLoadWithEnvPath(t *testing.T) {
 
 	t.Log(settings)
 }
+
+func TestQueryInterfaceField(t *testing.T) {
+	// Test JSON config
+	var jsonSettings Settings
+	err := LoadSettings("../../configs/config_sample.json", &jsonSettings)
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+
+	// Query interface field should exist (even if empty)
+	_ = jsonSettings.QueryInterface
+
+	// Test YAML config
+	var yamlSettings Settings
+	err = LoadSettings("../../configs/config_sample.yaml", &yamlSettings)
+	if err != nil {
+		t.Fatal(err.Error())
+	}
+
+	// Query interface field should exist (even if empty)
+	_ = yamlSettings.QueryInterface
+
+	t.Log("query_interface field loaded successfully")
+}

pkg/lib/ip_helper.go

@@ -273,10 +273,69 @@ func (helper *IPHelper) getIPOnline() string {
 				proto = "tcp4"
 			}
 
-			return (&net.Dialer{
+			dialer := &net.Dialer{
 				Timeout:   time.Second * utils.DefaultTimeout,
 				KeepAlive: 30 * time.Second,
-			}).DialContext(ctx, proto, addr)
+			}
+
+			// Bind to specific network interface if configured
+			if helper.configuration.QueryInterface != "" {
+				iface, err := net.InterfaceByName(helper.configuration.QueryInterface)
+				if err != nil {
+					log.Errorf("Failed to find query interface %s: %v", helper.configuration.QueryInterface, err)
+					return nil, err
+				}
+
+				addrs, err := iface.Addrs()
+				if err != nil {
+					log.Errorf("Failed to get addresses for query interface %s: %v", helper.configuration.QueryInterface, err)
+					return nil, err
+				}
+
+				// Find a suitable local address from the interface
+				var localAddr net.IP
+				for _, addr := range addrs {
+					var ip net.IP
+					switch v := addr.(type) {
+					case *net.IPNet:
+						ip = v.IP
+					case *net.IPAddr:
+						ip = v.IP
+					}
+
+					if ip == nil {
+						continue
+					}
+
+					// Match IP version with protocol
+					if proto == "tcp4" && ip.To4() != nil {
+						localAddr = ip
+						break
+					} else if proto == "tcp6" && ip.To4() == nil {
+						localAddr = ip
+						break
+					} else if proto == "tcp" {
+						// For generic tcp, prefer IPv4
+						if ip.To4() != nil {
+							localAddr = ip
+							break
+						}
+						if localAddr == nil {
+							localAddr = ip
+						}
+					}
+				}
+
+				if localAddr == nil {
+					log.Errorf("No suitable address found on query interface %s for protocol %s", helper.configuration.QueryInterface, proto)
+					return nil, errors.New("no suitable address on interface")
+				}
+
+				dialer.LocalAddr = &net.TCPAddr{IP: localAddr}
+				log.Debugf("Binding query to interface %s with local address %s", helper.configuration.QueryInterface, localAddr)
+			}
+
+			return dialer.DialContext(ctx, proto, addr)
 		},
 	}