Refactor iptables/ip6tables chain teardown into shared helper

src/host-iptables-cleanup.ts

@@ -1,8 +1,8 @@
-import execa from 'execa';
 import { logger } from './logger';
 import {
   CHAIN_NAME,
   CHAIN_NAME_V6,
+  cleanupChain,
   enableIpv6ViaSysctl,
   getNetworkBridgeName,
   isIp6tablesAvailable,
@@ -18,70 +18,21 @@ export async function cleanupHostIptables(): Promise<void> {
     // Get the bridge name
     const bridgeName = await getNetworkBridgeName();
 
-    // Clean up IPv4 rules
-    if (bridgeName) {
-      // Find and remove the rule that jumps to our chain
-      const { stdout } = await execa('iptables', [
-        '-t', 'filter', '-L', 'DOCKER-USER', '-n', '--line-numbers',
-      ], { reject: false });
-
-      // Parse line numbers for rules that reference our bridge
-      const lines = stdout.split('\n');
-      const lineNumbers: number[] = [];
-      for (const line of lines) {
-        if ((line.includes(`-i ${bridgeName}`) || line.includes(`-o ${bridgeName}`)) && line.includes(CHAIN_NAME)) {
-          const match = line.match(/^(\d+)/);
-          if (match) {
-            lineNumbers.push(parseInt(match[1], 10));
-          }
-        }
-      }
-
-      // Delete rules in reverse order (to maintain line numbers)
-      for (const lineNum of lineNumbers.reverse()) {
-        logger.debug(`Removing rule ${lineNum} from DOCKER-USER (IPv4)`);
-        await execa('iptables', [
-          '-t', 'filter', '-D', 'DOCKER-USER', lineNum.toString(),
-        ], { reject: false });
-      }
-    }
-
-    // Flush and delete our custom IPv4 chain
-    await execa('iptables', ['-t', 'filter', '-F', CHAIN_NAME], { reject: false });
-    await execa('iptables', ['-t', 'filter', '-X', CHAIN_NAME], { reject: false });
+    await cleanupChain('iptables', CHAIN_NAME, {
+      removeDockerUserReferences: Boolean(bridgeName),
+      matchPredicate: bridgeName
+        ? (line: string) => (line.includes(`-i ${bridgeName}`) || line.includes(`-o ${bridgeName}`)) && line.includes(CHAIN_NAME)
+        : undefined,
+    });
 
     logger.debug('IPv4 iptables rules cleaned up');
 
     // Clean up IPv6 rules (only if ip6tables is available)
     const ip6tablesAvailable = await isIp6tablesAvailable();
     if (ip6tablesAvailable) {
-      if (bridgeName) {
-        const { stdout: stdout6 } = await execa('ip6tables', [
-          '-t', 'filter', '-L', 'DOCKER-USER', '-n', '--line-numbers',
-        ], { reject: false });
-
-        const lines6 = stdout6.split('\n');
-        const lineNumbers6: number[] = [];
-        for (const line of lines6) {
-          if (line.includes(CHAIN_NAME_V6)) {
-            const match = line.match(/^(\d+)/);
-            if (match) {
-              lineNumbers6.push(parseInt(match[1], 10));
-            }
-          }
-        }
-
-        for (const lineNum of lineNumbers6.reverse()) {
-          logger.debug(`Removing rule ${lineNum} from DOCKER-USER (IPv6)`);
-          await execa('ip6tables', [
-            '-t', 'filter', '-D', 'DOCKER-USER', lineNum.toString(),
-          ], { reject: false });
-        }
-      }
-
-      // Flush and delete our custom IPv6 chain
-      await execa('ip6tables', ['-t', 'filter', '-F', CHAIN_NAME_V6], { reject: false });
-      await execa('ip6tables', ['-t', 'filter', '-X', CHAIN_NAME_V6], { reject: false });
+      await cleanupChain('ip6tables', CHAIN_NAME_V6, {
+        removeDockerUserReferences: Boolean(bridgeName),
+      });
 
       logger.debug('IPv6 ip6tables rules cleaned up');
     } else {

src/host-iptables-rules.ts

@@ -8,6 +8,7 @@ import {
   CHAIN_NAME_V6,
   NETWORK_NAME,
   addDnsRules,
+  cleanupChain,
   disableIpv6ViaSysctl,
   getDockerBridgeGateway,
   getNetworkBridgeName,
@@ -110,34 +111,7 @@ export async function setupHostIptables(squidIp: string, squidPort: number, dnsS
     const { exitCode } = await execa('iptables', ['-t', 'filter', '-L', CHAIN_NAME, '-n'], { reject: false });
     if (exitCode === 0) {
       logger.debug(`Chain '${CHAIN_NAME}' already exists, cleaning up...`);
-
-      // First, remove any references from DOCKER-USER
-      const { stdout } = await execa('iptables', [
-        '-t', 'filter', '-L', 'DOCKER-USER', '-n', '--line-numbers',
-      ], { reject: false });
-
-      const lines = stdout.split('\n');
-      const lineNumbers: number[] = [];
-      for (const line of lines) {
-        if (line.includes(CHAIN_NAME)) {
-          const match = line.match(/^(\d+)/);
-          if (match) {
-            lineNumbers.push(parseInt(match[1], 10));
-          }
-        }
-      }
-
-      // Delete rules in reverse order
-      for (const lineNum of lineNumbers.reverse()) {
-        logger.debug(`Removing reference to ${CHAIN_NAME} from DOCKER-USER line ${lineNum}`);
-        await execa('iptables', [
-          '-t', 'filter', '-D', 'DOCKER-USER', lineNum.toString(),
-        ], { reject: false });
-      }
-
-      // Then flush and delete the chain
-      await execa('iptables', ['-t', 'filter', '-F', CHAIN_NAME], { reject: false });
-      await execa('iptables', ['-t', 'filter', '-X', CHAIN_NAME], { reject: false });
+      await cleanupChain('iptables', CHAIN_NAME);
     }
   } catch (error) {
     // Ignore errors

src/host-iptables-shared.test.ts

@@ -0,0 +1,40 @@
+import { execaResult, mockedExeca } from './test-helpers/host-iptables-test-setup';
+import { cleanupChain } from './host-iptables-shared';
+
+describe('host-iptables-shared', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  describe('cleanupChain', () => {
+    it('removes matching DOCKER-USER references in reverse order before deleting the chain', async () => {
+      mockedExeca.mockImplementation(((cmd: string, args: string[]) => {
+        if (cmd === 'iptables' && args.includes('DOCKER-USER') && args.includes('--line-numbers')) {
+          return Promise.resolve(execaResult({
+            stdout: '1 FW_WRAPPER all -- 0.0.0.0/0 0.0.0.0/0\n3 FW_WRAPPER all -- 0.0.0.0/0 0.0.0.0/0\n',
+          }));
+        }
+        return Promise.resolve(execaResult());
+      }) as any);
+
+      await cleanupChain('iptables', 'FW_WRAPPER');
+
+      expect(mockedExeca).toHaveBeenCalledWith('iptables', ['-t', 'filter', '-D', 'DOCKER-USER', '3'], { reject: false });
+      expect(mockedExeca).toHaveBeenCalledWith('iptables', ['-t', 'filter', '-D', 'DOCKER-USER', '1'], { reject: false });
+      expect(mockedExeca).toHaveBeenCalledWith('iptables', ['-t', 'filter', '-F', 'FW_WRAPPER'], { reject: false });
+      expect(mockedExeca).toHaveBeenCalledWith('iptables', ['-t', 'filter', '-X', 'FW_WRAPPER'], { reject: false });
+    });
+
+    it('skips DOCKER-USER reference removal when configured', async () => {
+      mockedExeca.mockResolvedValue(execaResult());
+
+      await cleanupChain('ip6tables', 'FW_WRAPPER_V6', { removeDockerUserReferences: false });
+
+      expect(mockedExeca).not.toHaveBeenCalledWith('ip6tables', [
+        '-t', 'filter', '-L', 'DOCKER-USER', '-n', '--line-numbers',
+      ], { reject: false });
+      expect(mockedExeca).toHaveBeenCalledWith('ip6tables', ['-t', 'filter', '-F', 'FW_WRAPPER_V6'], { reject: false });
+      expect(mockedExeca).toHaveBeenCalledWith('ip6tables', ['-t', 'filter', '-X', 'FW_WRAPPER_V6'], { reject: false });
+    });
+  });
+});

src/host-iptables-shared.ts

@@ -145,6 +145,44 @@ export async function addDnsRules(
   }
 }
 
+/**
+ * Removes references to a chain from DOCKER-USER, then flushes and deletes the chain.
+ */
+export async function cleanupChain(
+  cmd: 'iptables' | 'ip6tables',
+  chainName: string,
+  options: {
+    removeDockerUserReferences?: boolean;
+    matchPredicate?: (line: string) => boolean;
+  } = {},
+): Promise<void> {
+  const { removeDockerUserReferences = true, matchPredicate } = options;
+
+  if (removeDockerUserReferences) {
+    const { stdout } = await execa(cmd, [
+      '-t', 'filter', '-L', 'DOCKER-USER', '-n', '--line-numbers',
+    ], { reject: false });
+
+    const lineNumbers: number[] = [];
+    for (const line of stdout.split('\n')) {
+      const shouldDelete = matchPredicate ? matchPredicate(line) : line.includes(chainName);
+      if (shouldDelete) {
+        const match = line.match(/^(\d+)/);
+        if (match) {
+          lineNumbers.push(parseInt(match[1], 10));
+        }
+      }
+    }
+
+    for (const lineNum of lineNumbers.reverse()) {
+      await execa(cmd, ['-t', 'filter', '-D', 'DOCKER-USER', lineNum.toString()], { reject: false });
+    }
+  }
+
+  await execa(cmd, ['-t', 'filter', '-F', chainName], { reject: false });
+  await execa(cmd, ['-t', 'filter', '-X', chainName], { reject: false });
+}
+
 /**
  * Re-enables IPv6 via sysctl if it was previously disabled.
  */