From d8151b64769e730f504a69ff6c52d090b3f06a62 Mon Sep 17 00:00:00 2001
From: Paul Bargewell <paul.bargewell@firebolt-group.com>
Date: Mon, 13 Jul 2026 14:32:17 +0100
Subject: [PATCH] fix: Detect interfaces without external connectivity probe

Interface detection previously bound an HTTPS request to
speed.cloudflare.com per interface and only listed interfaces where
that request succeeded. In many valid Docker setups (custom bridge
networks, ipvlan, restrictive DNS) that probe fails even though the
interface itself is fine, so it gets reported as "not found" and the
saved config is silently overwritten. Since requestInterfaces() reruns
hourly, a transient probe failure could keep resetting the user's
chosen interface.

List interfaces directly from os.networkInterfaces() instead, and
only fall back/reset the config when the interface has actually
disappeared from that list.

Fixes #806
---
 server/util/loadInterfaces.js | 50 +++++++++--------------------------
 1 file changed, 12 insertions(+), 38 deletions(-)

diff --git a/server/util/loadInterfaces.js b/server/util/loadInterfaces.js
index 0f896a021..7d280869f 100644
--- a/server/util/loadInterfaces.js
+++ b/server/util/loadInterfaces.js
@@ -1,5 +1,4 @@
 import os from 'node:os';
-import https from 'node:https';
 import * as config from '../controller/config.js';
 
 export let interfaces = {};
@@ -15,40 +14,14 @@ export const requestInterfaces = async () => {
 
             if (address.internal) continue;
 
-            let options = {hostname: "speed.cloudflare.com", path: "/__down?bytes=1", method: "GET",
-                family: address.family === "IPv4" ? 4 : 6, timeout: 5000};
-
-            options.agent = new https.Agent(options);
-            options.localAddress = address.address;
-
-            await new Promise((resolve) => {
-
-                const req = https.request(options, () => {
-                    if (!interfacesResult[i]) interfacesResult[i] = [];
-                    interfacesResult[i].push(address.address);
-                    req.destroy();
-                    resolve();
-                });
-
-                req.on('error', () => resolve());
-                req.on('timeout', () => req.destroy());
-
-                req.end();
-            });
+            if (!interfacesResult[i]) interfacesResult[i] = [];
+            interfacesResult[i].push(address.address);
         }
-
-        if (!interfacesResult[i]) delete interfacesResult[i];
     }
 
+    interfaces = {};
     for (let i in interfacesResult) {
-        for (let j in interfacesResult[i]) {
-            if (interfacesResult[i][j].includes(".")) {
-                interfaces[i] = interfacesResult[i][j];
-                break;
-            }
-        }
-
-        if (!interfaces[i]) interfaces[i] = interfacesResult[i][0];
+        interfaces[i] = interfacesResult[i].find((address) => address.includes(".")) || interfacesResult[i][0];
     }
 
     for (let i in interfaces) {
@@ -57,12 +30,13 @@ export const requestInterfaces = async () => {
 
     const currentInterface = await config.getValue("interface");
 
-    if (!interfaces[currentInterface]) {
-        if (!currentInterface) {
-            console.warn("No interface set. Falling back to default.");
-        } else {
-            console.warn(`Interface ${currentInterface} not found. Falling back to default.`);
-        }
-        await config.updateValue("interface", Object.keys(interfaces)[0]);
+    if (currentInterface && interfaces[currentInterface]) return;
+
+    if (!currentInterface) {
+        console.warn("No interface set. Falling back to default.");
+    } else {
+        console.warn(`Interface ${currentInterface} not found. Falling back to default.`);
     }
+
+    await config.updateValue("interface", Object.keys(interfaces)[0] || "none");
 };
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