From 0037ae72497e576808d69c9ef3fe55dabd4b64fe Mon Sep 17 00:00:00 2001
From: Peter Hedenskog <peter@soulgalore.com>
Date: Mon, 23 Mar 2026 22:57:05 +0100
Subject: [PATCH 1/2] Remove retry for default interface and cache the used one

---
 lib/tc.js | 45 +++++++++++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 18 deletions(-)

diff --git a/lib/tc.js b/lib/tc.js
index 00d14a1..557d143 100644
--- a/lib/tc.js
+++ b/lib/tc.js
@@ -1,30 +1,21 @@
 import shell from './shell.js';
 import sudo from './sudo.js';
 
-const delay = (ms) => new Promise((result) => setTimeout(result, ms));
+let cachedInterface;
 
 async function getDefaultInterface() {
   const command =
     "sudo ip route | awk '/default/ {print $5; exit}' | tr -d '\n'";
+  const result = await shell(command);
 
-  // Retry a few times since GitHub Actions sometimes temporarily loses the default route
-  for (let attempt = 0; attempt < 3; attempt++) {
-    const result = await shell(command);
-    if (result.stdout.length > 0) {
-      return result.stdout;
-    }
-    if (result.stderr.length > 0) {
-      throw new Error(
-        'There was an error getting the default interface:\n\n' + result.stderr
-      );
-    }
-    await delay(1000);
+  if (result.stdout.length === 0) {
+    const detail = result.stderr || '';
+    throw new Error(
+      'There was an error getting the default interface:\n\n' + detail
+    );
   }
 
-  const result = await shell('sudo ip route show');
-  throw new Error(
-    `There was an error getting the default interface ${result.stdout}`
-  );
+  return result.stdout;
 }
 
 async function moduleProbe() {
@@ -181,13 +172,31 @@ export async function start(up, down, rtt = 0, packetLoss = 0) {
   }
 
   const indexFace = await getDefaultInterface();
+  cachedInterface = indexFace;
   await moduleProbe();
   await setupifb0();
   await setup(indexFace);
   await setLimits(up, down, halfWayRTT, packetLoss, indexFace);
 }
+async function getThrottledInterface() {
+  // Find the interface that has our ingress qdisc, since the default route
+  // may not be available while throttling is active
+  const result = await shell(
+    "tc qdisc show | awk '/ingress/ {print $5; exit}'"
+  );
+  return result.stdout.trim();
+}
+
 export async function stop() {
-  const indexFace = await getDefaultInterface();
+  let indexFace = cachedInterface;
+  if (!indexFace) {
+    // Try to find the interface with our tc rules first, fall back to default route
+    indexFace = await getThrottledInterface();
+    if (!indexFace) {
+      indexFace = await getDefaultInterface();
+    }
+  }
+  cachedInterface = undefined;
 
   try {
     try {

From 76ee5cb8676a34e162bab49943493e51835458d3 Mon Sep 17 00:00:00 2001
From: Peter Hedenskog <peter@soulgalore.com>
Date: Mon, 23 Mar 2026 23:04:23 +0100
Subject: [PATCH 2/2] new try

---
 lib/tc.js | 48 +++++++++++++++++-------------------------------
 1 file changed, 17 insertions(+), 31 deletions(-)

diff --git a/lib/tc.js b/lib/tc.js
index 557d143..745fb59 100644
--- a/lib/tc.js
+++ b/lib/tc.js
@@ -1,21 +1,25 @@
 import shell from './shell.js';
 import sudo from './sudo.js';
 
-let cachedInterface;
-
 async function getDefaultInterface() {
-  const command =
-    "sudo ip route | awk '/default/ {print $5; exit}' | tr -d '\n'";
-  const result = await shell(command);
-
-  if (result.stdout.length === 0) {
-    const detail = result.stderr || '';
-    throw new Error(
-      'There was an error getting the default interface:\n\n' + detail
-    );
+  // Try the default route first
+  const routeResult = await shell(
+    "sudo ip route | awk '/default/ {print $5; exit}' | tr -d '\n'"
+  );
+  if (routeResult.stdout.length > 0) {
+    return routeResult.stdout;
+  }
+
+  // Fall back to finding the interface with a global IP address,
+  // since the default route may be gone while throttling is active
+  const addrResult = await shell(
+    "ip -o -4 addr show scope global | awk '{print $2; exit}'"
+  );
+  if (addrResult.stdout.trim().length > 0) {
+    return addrResult.stdout.trim();
   }
 
-  return result.stdout;
+  throw new Error('Could not find the default network interface');
 }
 
 async function moduleProbe() {
@@ -172,31 +176,13 @@ export async function start(up, down, rtt = 0, packetLoss = 0) {
   }
 
   const indexFace = await getDefaultInterface();
-  cachedInterface = indexFace;
   await moduleProbe();
   await setupifb0();
   await setup(indexFace);
   await setLimits(up, down, halfWayRTT, packetLoss, indexFace);
 }
-async function getThrottledInterface() {
-  // Find the interface that has our ingress qdisc, since the default route
-  // may not be available while throttling is active
-  const result = await shell(
-    "tc qdisc show | awk '/ingress/ {print $5; exit}'"
-  );
-  return result.stdout.trim();
-}
-
 export async function stop() {
-  let indexFace = cachedInterface;
-  if (!indexFace) {
-    // Try to find the interface with our tc rules first, fall back to default route
-    indexFace = await getThrottledInterface();
-    if (!indexFace) {
-      indexFace = await getDefaultInterface();
-    }
-  }
-  cachedInterface = undefined;
+  const indexFace = await getDefaultInterface();
 
   try {
     try {