fix(dns): filter non-portable DNS in network-isolation + Tailscale by Copilot · Pull Request #6705 · github/gh-aw-firewall

Copilot · 2026-07-29T00:18:49Z

In network-isolation mode + Tailscale, every Squid CONNECT to api.githubcopilot.com fails with 503 TCP_TUNNEL:HIER_NONE (server field -:-, indicating DNS never resolved). When Tailscale starts as a later workflow step it modifies the host's policy routing table 52 — if a Tailscale exit node or accepted subnet route covers 0.0.0.0/0, Docker bridge traffic on awf-ext follows the from all lookup 52 rule through the Tailscale tunnel. Azure DHCP DNS (168.63.129.16) is Azure-hypervisor-intercepted and unreachable via Tailscale, so all Squid DNS queries black-hole.

Changes

`src/dns-resolver.ts` — new exports

isNonPortableDns(ip) — identifies DNS servers that depend on host-specific routing paths Tailscale can capture: Azure DHCP DNS (168.63.129.16), Tailscale Magic DNS (100.100.100.100), link-local 169.254.x.x
filterForNetworkIsolation(servers, logger) — strips non-portable servers with a warning; falls back to 8.8.8.8/8.8.4.4 if all detected servers are non-portable

`src/config-writer.ts` — apply filter in isolation mode

Before generating squid.conf, apply filterForNetworkIsolation() when config.networkIsolation is true:

const resolvedDnsServers = config.dnsServers ?? DEFAULT_DNS_SERVERS;
const squidDnsServers = config.networkIsolation
  ? filterForNetworkIsolation(resolvedDnsServers, logger)
  : resolvedDnsServers;

Users requiring specific DNS in isolation mode can still override via --dns-servers.

`src/dns-resolver.test.ts`

15 new unit tests covering portable/non-portable detection, mixed lists, all-non-portable fallback, and RFC1918 corporate DNS passthrough.

Fixes [awf] network: isolation/topology mode + Tailscale → Squid 503 TCP_TUNNEL:HIER_NONE on api.githubcopilot.com egress #6704

github-actions · 2026-07-29T04:08:56Z

⚠️ Coverage Regression Detected

This PR decreases test coverage. Please add tests to maintain coverage levels.

Overall Coverage

Metric	Base	PR	Delta
Lines	99.10%	99.13%	📈 +0.03%
Statements	98.99%	99.02%	📈 +0.03%
Functions	99.14%	99.14%	➡️ +0.00%
Branches	95.62%	95.61%	📉 -0.01%

📁 Per-file Coverage Changes (2 files)

File	Lines (Before → After)	Statements (Before → After)
`src/config-writer.ts`	95.1% → 95.2% (+0.11%)	95.1% → 95.2% (+0.11%)
`src/log-directory-setup.ts`	96.2% → 100.0% (+3.78%)	96.3% → 100.0% (+3.71%)

Coverage comparison generated by scripts/ci/compare-coverage.ts

Copilot

Pull request overview

Filters host-specific DNS resolvers in network-isolation mode to prevent Tailscale-related Squid DNS failures.

Changes:

Detects Azure, Tailscale, and link-local DNS addresses.
Falls back to public DNS when necessary.
Adds resolver unit tests.

Show a summary per file

File	Description
`src/dns-resolver.ts`	Adds DNS classification and filtering.
`src/dns-resolver.test.ts`	Tests filtering behavior.
`src/config-writer.ts`	Applies filtering to Squid configuration.

Review details

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Files reviewed: 3/3 changed files
Comments generated: 3
Review effort level: Medium

+  const resolvedDnsServers = config.dnsServers ?? DEFAULT_DNS_SERVERS;
+  const squidDnsServers = config.networkIsolation
+    ? filterForNetworkIsolation(resolvedDnsServers, logger)
+    : resolvedDnsServers;


+  const squidDnsServers = config.networkIsolation
+    ? filterForNetworkIsolation(resolvedDnsServers, logger)
+    : resolvedDnsServers;


    allowHostPorts: config.allowHostPorts,
    enableDlp: config.enableDlp,
-    dnsServers: config.dnsServers,
+    dnsServers: squidDnsServers,


lpcox · 2026-07-29T05:19:25Z

@copilot Fix the code for all comments in this review thread.

When a review comment includes a suggested change, apply the suggestion exactly.

Do not make changes beyond what is described in the linked review thread.

Copilot · 2026-07-29T05:30:46Z

@copilot Fix the code for all comments in this review thread.

When a review comment includes a suggested change, app...

All three review points are addressed in the latest commit (fix(dns): preserve explicit DNS; fix audit manifest and add tests):

Explicit DNS no longer filtered — Added dnsServersExplicit?: boolean to NetworkOptions / WrapperConfig. resolveNetworkConfig now sets it true when --dns-servers (or network.dnsServers in a config file) was supplied, false when auto-detected. The isolation-mode filter guard in config-writer.ts now checks !config.dnsServersExplicit before calling filterForNetworkIsolation, so an operator-specified resolver such as 168.63.129.16 is respected as-is.
Audit manifest reflects enforced DNS — writeAuditArtifacts now accepts squidDnsServers as an optional parameter and uses it (squidDnsServers ?? config.dnsServers) for generatePolicyManifest, so policy-manifest.json reports the servers Squid actually uses rather than the raw detected list.
Config-writer integration tests — src/config-writer-dns-isolation.test.ts (9 tests) verifies: non-portable servers are filtered only when networkIsolation: true + dnsServersExplicit: false; the filtered list reaches both generateSquidConfig and generatePolicyManifest; and explicitly-supplied non-portable servers are never filtered.

github-actions · 2026-07-29T05:45:36Z

✅ Copilot review passed with no inline comments.

@copilot Add the ready-for-aw label to this PR to trigger agentic CI smoke tests.

github-actions · 2026-07-29T05:46:14Z

✅ Smoke Gemini completed. All facets verified. 💎

github-actions · 2026-07-29T05:46:14Z

🔌 Smoke Services — All services reachable! ✅

github-actions · 2026-07-29T05:46:16Z

🚀 Security Guard has started processing this pull request

github-actions · 2026-07-29T05:46:17Z

✅ Build Test Suite completed successfully!

github-actions · 2026-07-29T05:46:18Z

✨ The prophecy is fulfilled... Smoke Codex has completed its mystical journey. The stars align. 🌟

github-actions · 2026-07-29T05:46:19Z

📰 VERDICT: Smoke Docker Sbx has concluded. All systems operational. This is a developing story. 🎤

github-actions · 2026-07-29T05:46:19Z

📡 Smoke OTel Tracing completed. All tracing scenarios validated. ✅

github-actions · 2026-07-29T05:46:21Z

✅ Smoke Claude passed

github-actions · 2026-07-29T05:46:25Z

🛡️ Smoke Copilot Network Isolation confirmed the egress allowlist is enforced. ✅

github-actions · 2026-07-29T05:46:25Z

📰 VERDICT: Smoke Copilot has concluded. All systems operational. This is a developing story. 🎤

github-actions · 2026-07-29T05:46:26Z

✅ Contribution Check completed successfully!

github-actions · 2026-07-29T05:46:27Z

✅ Smoke Copilot BYOK completed. Copilot BYOK mode operational. 🔓

github-actions · 2026-07-29T05:46:40Z

❌ Smoke Copilot BYOK AOAI (api-key) reports failed. AOAI BYOK (api-key) mode investigation needed...

github-actions · 2026-07-29T05:46:44Z

Chroot tests passed! Smoke Chroot - All security and functionality tests succeeded.

github-actions · 2026-07-29T05:48:04Z

Smoke Test: Claude Engine Validation

Check	Result
API status	✅ PASS
GH check	✅ PASS
File status	✅ PASS

Overall result: PASS ✅

Generated by Smoke Claude for #6705 · haiku45 · 54.5 AIC · ⊞ 3.3K · ◷
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github-actions · 2026-07-29T05:48:13Z

✅ Coverage Check Passed

Overall Coverage

Metric	Base	PR	Delta
Lines	99.10%	99.13%	📈 +0.03%
Statements	98.99%	99.02%	📈 +0.03%
Functions	99.14%	99.14%	➡️ +0.00%
Branches	95.62%	95.64%	📈 +0.02%

📁 Per-file Coverage Changes (2 files)

File	Lines (Before → After)	Statements (Before → After)
`src/config-writer.ts`	95.1% → 95.2% (+0.11%)	95.1% → 95.2% (+0.11%)
`src/log-directory-setup.ts`	96.2% → 100.0% (+3.78%)	96.3% → 100.0% (+3.71%)

Coverage comparison generated by scripts/ci/compare-coverage.ts

github-actions · 2026-07-29T05:48:17Z

@lpcox — Smoke test results for network isolation egress enforcement:

EGRESS_RESULT allow=pass deny=pass

✅ Allowed domain (api.github.com): HTTP 200
✅ Blocked domain (example.com): blocked by proxy (403)

Overall: PASS

Warning

Firewall blocked 1 domain

The following domain was blocked by the firewall during workflow execution:

example.com

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "example.com"

See Network Configuration for more information.

🛡️ Egress verdict from Smoke Copilot Network Isolation
_{Add label ready-for-aw to run again}

github-actions · 2026-07-29T05:48:21Z

Smoke Test: Services Connectivity

Check	Result
Redis PING	❌ Name resolution failed for `host.docker.internal`
PostgreSQL pg_isready	❌ No response
PostgreSQL SELECT 1	❌ Name resolution failed

Overall: FAIL — host.docker.internal is not resolvable in this environment.

🔌 Service connectivity validated by Smoke Services
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github-actions · 2026-07-29T05:48:30Z

Looks good overall, but I think this PR still needs a small docs update for the new network-isolation DNS behavior. CONTRIBUTING.md asks contributors to update documentation for new features/behavior changes (Documentation and Pull Request Process sections), and this change adds a new filtering/fallback path that users may want to know about in the README or DNS/network-isolation docs.

The PR description is clear and already references the related issue, and the new tests are in the right place.

Generated by Contribution Check for #6705 · gpt54mini · 3.93 AIC · ⊞ 22.5K · ◷
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github-actions · 2026-07-29T05:48:35Z

🔬 Smoke Test Results

Test	Status
GitHub MCP Connectivity	✅ Connected (secrecy policy filtered data)
GitHub.com HTTP	⚠️ Pre-step data unavailable (template vars unexpanded)
File Write/Read	⚠️ Pre-step data unavailable (template vars unexpanded)

Overall: PARTIAL — MCP connectivity verified; pre-computed test data was not injected (workflow template variables unexpanded).

cc @lpcox

📰 BREAKING: Report filed by Smoke Copilot
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github-actions · 2026-07-29T05:48:43Z

Smoke Test: Copilot BYOK (Direct) — PR #6705

Test	Status
GitHub MCP connectivity	✅ (filtered by secrecy policy, but MCP responded)
GitHub.com connectivity	⚠️ Pre-fetched data not available (template vars unresolved)
File write/read	⚠️ Pre-fetched data not available (template vars unresolved)
BYOK inference (api-proxy → api.githubcopilot.com)	✅

Running in direct BYOK mode (COPILOT_PROVIDER_API_KEY) via api-proxy → api.githubcopilot.com.

@lpcox — Overall status: PARTIAL (pre-computed step outputs were not resolved; BYOK inference confirmed working)

🔑 BYOK report filed by Smoke Copilot BYOK
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github-actions · 2026-07-29T05:48:52Z

Smoke Test Results

GitHub MCP: ✅ (Redacted titles: feat(api-proxy): use runtime model metadata and pricing overlays #6695, Deduplicate main-action Jest harness setup across coverage-gap suites #6691)
Connectivity: ❌ (Status 000)
File Writing: ✅
Bash Tool: ✅

Overall Status: FAIL

Warning

Firewall blocked 1 domain

The following domain was blocked by the firewall during workflow execution:

localhost

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "localhost"

See Network Configuration for more information.

💎 Faceted by Smoke Gemini
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github-actions · 2026-07-29T05:49:09Z

🔭 Smoke Test: API Proxy OpenTelemetry Tracing

Scenario	Result	Notes
1. Module Loading	✅	`otel.js` loads successfully; exports: `startRequestSpan`, `setTokenAttributes`, `setBudgetAttributes`, `endSpan`, `endSpanError`, `shutdown`, `isEnabled` + test helpers
2. Test Suite	✅	39/39 tests passed (`otel.test.js`) in 1.5s
3. Env Var Forwarding	✅	`src/services/api-proxy-env-config.ts` forwards `GH_AW_OTLP_ENDPOINTS`, `OTEL_EXPORTER_OTLP_ENDPOINT`, `OTEL_EXPORTER_OTLP_HEADERS`, `GITHUB_AW_OTEL_TRACE_ID`, `GITHUB_AW_OTEL_PARENT_SPAN_ID`, `OTEL_SERVICE_NAME`
4. Token Tracker Integration	✅	`onUsage` callback exists in `token-tracker-http.js` (line 348/406) as the OTEL hook point
5. OTEL Diagnostics	✅	Fallback file exporter writes spans to `/var/log/api-proxy/otel.jsonl` when no OTLP endpoint configured; graceful degradation confirmed

All scenarios pass. OTEL tracing integration is fully functional.

📡 OTel tracing validated by Smoke OTel Tracing
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github-actions · 2026-07-29T05:49:43Z

🏗️ Build Test Suite Results

Ecosystem	Project	Build/Install	Tests	Status
Bun	elysia	✅	1/1 passed	✅ PASS
Bun	hono	✅	1/1 passed	✅ PASS
C++	fmt	✅	N/A	✅ PASS
C++	json	✅	N/A	✅ PASS
Deno	oak	N/A	1/1 passed	✅ PASS
Deno	std	N/A	1/1 passed	✅ PASS
.NET	hello-world	✅	N/A	✅ PASS
.NET	json-parse	✅	N/A	✅ PASS
Go	color	✅	1/1 passed	✅ PASS
Go	env	✅	1/1 passed	✅ PASS
Go	uuid	✅	1/1 passed	✅ PASS
Java	gson	✅	1/1 passed	✅ PASS
Java	caffeine	✅	1/1 passed	✅ PASS
Node.js	clsx	✅	All passed	✅ PASS
Node.js	execa	✅	All passed	✅ PASS
Node.js	p-limit	✅	All passed	✅ PASS
Rust	fd	✅	1/1 passed	✅ PASS
Rust	zoxide	✅	1/1 passed	✅ PASS

Overall: 8/8 ecosystems passed — ✅ PASS

Generated by Build Test Suite for #6705 · sonnet46 · 33.1 AIC · ⊞ 8.4K · ◷
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github-actions · 2026-07-29T05:50:38Z

Chroot Version Comparison Results

Runtime	Host Version	Chroot Version	Match?
Python	`Python 3.12.13`	`Python 3.12.13`	✅ YES
Node.js	`v24.18.0`	`v22.23.1`	❌ NO
Go	`go1.22.12`	`go1.22.12`	✅ YES

Result: ❌ FAILED — Node.js version mismatch (host: v24.18.0, chroot: v22.23.1).

Tested by Smoke Chroot
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github-actions · 2026-07-29T05:50:49Z

Smoke Test

Reviewed: feat(api-proxy): use runtime model metadata and pricing overlays
Reviewed: Deduplicate main-action Jest harness setup across coverage-gap suites
Results: GitHub PRs ✅ | SafeInputs GH CLI ✅ | Playwright ✅ | File ✅ | Discussion ✅ | Build ❌
Overall: FAIL

Warning

Firewall blocked 1 domain

The following domain was blocked by the firewall during workflow execution:

registry.npmjs.org

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "registry.npmjs.org"

See Network Configuration for more information.

🔮 The oracle has spoken through Smoke Codex
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github-actions · 2026-07-29T05:51:06Z

🔬 Smoke Test Results — Docker Sbx

Test	Status
GitHub MCP connectivity	✅ Connected (2 PRs listed)
GitHub.com HTTP	⚠️ Pre-step output unavailable (template vars not expanded)
File write/read	⚠️ Pre-step output unavailable (template vars not expanded)

Overall: ⚠️ PARTIAL — MCP works, but pre-computed step outputs were not injected into the prompt.

@lpcox — smoke test ran but pre-step outputs (steps.smoke-data.outputs.*) were not substituted. The workflow may need to pass these values differently.

📰 BREAKING: Report filed by Smoke Docker Sbx
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Initial plan

b4a6292

Copilot AI assigned Copilot and lpcox Jul 29, 2026

Copilot started work on behalf of lpcox July 29, 2026 00:19 View session

Copilot AI linked an issue Jul 29, 2026 that may be closed by this pull request

[awf] network: isolation/topology mode + Tailscale → Squid 503 TCP_TUNNEL:HIER_NONE on api.githubcopilot.com egress #6704

Closed

fix(dns): filter non-portable DNS in network-isolation mode

143d02e

Copilot AI changed the title ~~[WIP] Fix 503 TCP_TUNNEL:HIER_NONE error with Tailscale~~ fix(dns): filter non-portable DNS in network-isolation + Tailscale Jul 29, 2026

Copilot finished work on behalf of lpcox July 29, 2026 00:39

Copilot AI requested a review from lpcox July 29, 2026 00:39

lpcox marked this pull request as ready for review July 29, 2026 04:06

Copilot AI review requested due to automatic review settings July 29, 2026 04:06

Copilot started reviewing on behalf of lpcox July 29, 2026 04:06 View session

Copilot AI reviewed Jul 29, 2026

View reviewed changes

Copilot started work on behalf of lpcox July 29, 2026 05:20 View session

fix(dns): preserve explicit DNS; fix audit manifest and add tests

5b6a8b2

Copilot finished work on behalf of lpcox July 29, 2026 05:31

lpcox added the ready-for-aw label Jul 29, 2026

lpcox enabled auto-merge (squash) July 29, 2026 05:45

lpcox had a problem deploying to aoai-model July 29, 2026 05:46 — with GitHub Actions Failure

github-actions Bot added the smoke-claude label Jul 29, 2026

github-actions Bot added the smoke-copilot-network-isolation Copilot network-isolation egress smoke test label Jul 29, 2026

lpcox temporarily deployed to aoai-model July 29, 2026 05:48 — with GitHub Actions Inactive

github-actions Bot added the build-test label Jul 29, 2026

lpcox merged commit 7b6a767 into main Jul 29, 2026
136 of 139 checks passed

lpcox deleted the copilot/awf-network-isolation-fix branch July 29, 2026 05:57

This was referenced Jul 29, 2026

🩺 Runner Doctor Update2026-07-29 scan — B17 Tailscale+isolation DNS black-hole, B18 Azure CLI/.azure whitelist #6727

Closed

[aw] No-Op Runs #6709

Open

Copilot AI mentioned this pull request Jul 29, 2026

docs(runner-doctor): add B17 (Tailscale DNS black-hole) and B18 (Azure CLI/.azure) failure modes #6735

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Changes

src/dns-resolver.ts — new exports

src/config-writer.ts — apply filter in isolation mode

src/dns-resolver.test.ts

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`src/dns-resolver.ts` — new exports

`src/config-writer.ts` — apply filter in isolation mode

`src/dns-resolver.test.ts`

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