Dual-stack fixes for Upstreams by #798

Co-Authored-By: brekotis <93345790+brekotis@users.noreply.github.com>

src/config/load.rs

@@ -1007,6 +1007,14 @@ fn validate_upstreams(config: &ProxyConfig) -> Result<()> {
                 "upstream.ipv4 and upstream.ipv6 cannot both be false".to_string(),
             ));
         }
+        if let Some(prefer) = upstream.prefer
+            && prefer != 4
+            && prefer != 6
+        {
+            return Err(ProxyError::Config(
+                "upstream.prefer must be 4 or 6".to_string(),
+            ));
+        }
 
         if let UpstreamType::Shadowsocks { url, .. } = &upstream.upstream_type {
             let parsed = ShadowsocksServerConfig::from_url(url)
@@ -1022,6 +1030,26 @@ fn validate_upstreams(config: &ProxyConfig) -> Result<()> {
     Ok(())
 }
 
+fn normalize_upstream_family_policy(config: &mut ProxyConfig) {
+    for (idx, upstream) in config.upstreams.iter_mut().enumerate() {
+        if matches!(upstream.ipv4, Some(false)) && upstream.prefer == Some(4) {
+            warn!(
+                upstream = idx,
+                "upstream.prefer=4 but upstream.ipv4=false; forcing prefer=6"
+            );
+            upstream.prefer = Some(6);
+        }
+
+        if matches!(upstream.ipv6, Some(false)) && upstream.prefer == Some(6) {
+            warn!(
+                upstream = idx,
+                "upstream.prefer=6 but upstream.ipv6=false; forcing prefer=4"
+            );
+            upstream.prefer = Some(4);
+        }
+    }
+}
+
 // ============= Main Config =============
 
 #[derive(Debug, Clone, Serialize, Deserialize, Default)]
@@ -2200,8 +2228,10 @@ impl ProxyConfig {
                 selected_scope: String::new(),
                 ipv4: None,
                 ipv6: None,
+                prefer: None,
             });
         }
+        normalize_upstream_family_policy(&mut config);
 
         // Ensure default DC203 override is present.
         config

src/config/types.rs

@@ -2065,6 +2065,20 @@ pub struct UpstreamConfig {
     /// `None` means auto-detect from runtime connectivity state.
     #[serde(default)]
     pub ipv6: Option<bool>,
+    /// Per-upstream IP family preference for Telegram DC targets.
+    /// `None` inherits the effective global `[network].prefer` decision.
+    #[serde(default)]
+    pub prefer: Option<u8>,
+}
+
+impl UpstreamConfig {
+    pub fn prefer_ipv6(&self, default_prefer_ipv6: bool) -> bool {
+        match self.prefer {
+            Some(6) => true,
+            Some(4) => false,
+            _ => default_prefer_ipv6,
+        }
+    }
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]