test(netwatch): add patchbay network simulation tests

Add patchbay tests that exercise netwatch's interface and route
detection inside virtual network namespaces. The tests cover v4-only,
v6-only, dual-stack, and v4-to-v6 replug scenarios.

Three of the five tests are currently ignored: they expose a bug where
default_route() fails to detect IPv6 default routes on Linux because
/proc/net/route only contains IPv4 entries and the netlink fallback is
never reached.

Also adds patchbay CI workflow, nextest patchbay profile, and a
cargo-make task to match the iroh project's patchbay setup.

Author: Frando

.config/nextest.toml

@@ -7,4 +7,13 @@ run-in-isolation = { max-threads = 32 }
 [[profile.ci.overrides]]
 filter = 'test(::run_in_isolation::)'
 test-group = 'run-in-isolation'
-threads-required = 32
+threads-required = 32
+
+[profile.default]
+default-filter = 'not binary(patchbay)'
+
+[profile.patchbay]
+fail-fast = false
+test-threads = 1
+default-filter = 'binary(patchbay)'
+slow-timeout = { period = "30s", terminate-after = 4 }

.github/workflows/patchbay.yml

@@ -0,0 +1,56 @@
+name: Patchbay Tests
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+concurrency:
+  group: patchbay-${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+env:
+  RUST_BACKTRACE: 1
+  SCCACHE_CACHE_SIZE: "10G"
+
+jobs:
+  patchbay_tests:
+    name: Patchbay Tests
+    timeout-minutes: 15
+    runs-on: [self-hosted, linux, X64]
+    env:
+      RUSTC_WRAPPER: "sccache"
+    steps:
+      - name: Enable unprivileged user namespaces
+        run: sudo sysctl -w kernel.apparmor_restrict_unprivileged_userns=0
+        continue-on-error: true
+
+      - uses: actions/checkout@v6
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: mozilla-actions/sccache-action@v0.0.9
+      - name: Install cargo-make and cargo-nextest
+        uses: taiki-e/install-action@v2
+        with:
+          tool: nextest@0.9.80,cargo-make
+
+      - name: Build patchbay tests
+        run: cargo make patchbay --no-run
+
+      - name: Run patchbay tests
+        run: |
+          set -o pipefail
+          cargo make patchbay 2>&1 | tee "$RUNNER_TEMP/logs.txt"
+        env:
+          PATCHBAY_LOG: trace
+          RUST_LOG: trace
+
+      - name: Upload test results
+        if: always()
+        uses: actions/upload-artifact@v7
+        with:
+          name: patchbay-testdir-${{ github.sha }}
+          path: |
+            ${{ runner.temp }}/logs.txt
+          retention-days: 7
+          if-no-files-found: ignore