test(e2e): give the dynamips routers a detected idle-PC

Without one every c7200 busy-waits a full CPU core for the whole scenario
-- the tests create raw nodes and no template supplies a value (measured:
constant ~100 % per router, up to ~6 minutes per dynamips scenario).

harness.dynamips_idlepc() detects a value through the controller's
auto_idlepc endpoint (the GUI idle-PC finder path: a throwaway project
boots the image, candidate values are validated by measuring actual CPU
usage) and caches it in ~/.cache/gns3-e2e/idlepc.json keyed by the image
checksum, so the cost (~100 s here) is paid once per image, not per run.
GNS3_E2E_IDLEPC overrides detection; any failure returns None and the
scenarios run without one rather than fail on a CPU optimisation.

All four scenarios that boot c7200 routers (dynamips kernel/relay,
ethernet switch kernel/relay) pass the value at creation. Live: detected
0x60189234 for the M11 image (238 s first run including detection); the
routers drop from ~100 % during boot to 3-8 % steady (sampled per
process), and a re-run reports the cached value with no detection.

tests/e2e/README.md

@@ -33,6 +33,15 @@ Either way each test creates its own project and deletes it again. Set
 `GNS3_E2E_KEEP=1` to keep the project (and a started instance) on failure
 and print where to look at it.
 
+The dynamips scenarios give their routers an idle-PC: detected once per
+image through the controller's `auto_idlepc` (a throwaway project and a
+real CPU-usage measurement — the GUI's idle-PC finder path) and cached in
+`~/.cache/gns3-e2e/idlepc.json` keyed by the image checksum. Without one,
+each c7200 burns a **full CPU core** for the whole scenario — the e2e
+creates raw nodes, so no template supplies a value. Set `GNS3_E2E_IDLEPC`
+to skip the detection and use the given value (detection failing is never
+fatal: the routers simply run without one).
+
 `harness.py` holds the shared pieces — REST client, server lifecycle, the
 IOS console driver, host-side kernel inspections (bridge membership, tap
 admin state, tc qdiscs, the L2-anchor spec §E assertions) — so a new node

tests/e2e/harness.py

@@ -39,6 +39,9 @@ Environment knobs:
 * ``GNS3_E2E_USER`` / ``GNS3_E2E_PASSWORD`` — credentials for the target.
 * ``GNS3_E2E_IMAGES`` — images directory the isolated instance uses
   (default ``~/GNS3/images``); also where the dynamips test finds its image.
+* ``GNS3_E2E_IDLEPC`` — use this idle-PC value for the dynamips routers
+  instead of detecting one (see ``dynamips_idlepc``; without an idle-PC each
+  router burns a full CPU core for the whole scenario).
 * ``GNS3_E2E_KEEP=1`` — keep the project (and the isolated instance) when a
   test fails, and print their ids, for inspection.
 """
@@ -121,8 +124,10 @@ class Compute:
     def create_project(self, name="e2e"):
         return self.call("POST", "/projects", {"name": f"{name}-{int(time.time())}"})
 
-    def create_dynamips_router(self, project_id, name, image, slots, platform="c7200", ram=512):
+    def create_dynamips_router(self, project_id, name, image, slots, platform="c7200", ram=512, idlepc=None):
         properties = {"platform": platform, "image": image, "ram": ram}
+        if idlepc:
+            properties["idlepc"] = idlepc
         properties.update(slots)
         return self.call(
             "POST",
@@ -350,6 +355,79 @@ def release(server, project_id, failed=False):
         server.stop()
 
 
+# ---------------------------------------------------------------------------
+# Dynamips idle-PC (CPU)
+# ---------------------------------------------------------------------------
+
+# Detected values, keyed by image identity; the detection needs a throwaway
+# boot, so it is worth caching across runs.
+IDLEPC_CACHE_PATH = os.path.join(os.path.expanduser("~/.cache/gns3-e2e"), "idlepc.json")
+
+
+def dynamips_idlepc(server, image, platform="c7200", ram=512):
+    """The idle-PC value the scenarios' dynamips routers should be created
+    with — detected once per image and cached.
+
+    Without one, dynamips busy-waits and burns a *full CPU core per router*
+    for the whole scenario: the e2e creates raw nodes, and no template
+    supplies an idle-PC. Detection goes through the controller's
+    ``auto_idlepc`` endpoint — the GUI's idle-PC finder path: a throwaway
+    project boots the image, candidate values are validated by measuring the
+    actual process CPU (first candidate under 70 % wins) — and the result is
+    cached in ``~/.cache/gns3-e2e/idlepc.json`` keyed by the image's
+    checksum, so the cost is paid once per image, not once per run.
+
+    ``GNS3_E2E_IDLEPC`` overrides detection and cache entirely. Any failure
+    returns None: the scenarios then run without an idle-PC (and burn the
+    cores) rather than fail on a CPU optimisation.
+    """
+    override = os.environ.get("GNS3_E2E_IDLEPC")
+    if override:
+        return override
+
+    checksum = None
+    for entry in server.compute.call("GET", "/computes/local/dynamips/images"):
+        if entry["filename"] == image:
+            checksum = entry.get("md5sum")
+            break
+    key = f"{image}:{checksum}" if checksum else image
+
+    cache = {}
+    try:
+        with open(IDLEPC_CACHE_PATH) as f:
+            cache = json.load(f)
+    except (OSError, ValueError):
+        pass
+    if cache.get(key):
+        print(f".. idle-PC {cache[key]} for {image} (cached)")
+        return cache[key]
+
+    print(f".. detecting an idle-PC for {image} (once per image — this takes a few minutes)")
+    try:
+        result = server.compute.call(
+            "POST",
+            "/computes/local/dynamips/auto_idlepc",
+            {"platform": platform, "image": image, "ram": ram},
+            timeout=600,
+        )
+    except Exception as e:
+        print(f".. idle-PC detection failed ({e}); the routers will burn a core each")
+        return None
+    idlepc = (result or {}).get("idlepc")
+    if not idlepc:
+        print(f".. no idle-PC value found for {image}; the routers will burn a core each")
+        return None
+    cache[key] = idlepc
+    try:
+        os.makedirs(os.path.dirname(IDLEPC_CACHE_PATH), exist_ok=True)
+        with open(IDLEPC_CACHE_PATH, "w") as f:
+            json.dump(cache, f, indent=2, sort_keys=True)
+    except OSError as e:
+        print(f".. could not write the idle-PC cache {IDLEPC_CACHE_PATH}: {e}")
+    print(f".. idle-PC {idlepc} for {image} (cached for later runs)")
+    return idlepc
+
+
 # ---------------------------------------------------------------------------
 # IOS console (dynamips telnet console)
 # ---------------------------------------------------------------------------

tests/e2e/test_dynamips_kernel_datapath.py

@@ -84,13 +84,14 @@ def test_dynamips_kernel_datapath():
     if compute.capabilities().get("ubridge_tap") is not True:
         pytest.skip("this compute's uBridge cannot create persistent TAPs (ubridge_tap != True)")
     image = _pick_image(server)
+    idlepc = harness.dynamips_idlepc(server, image)
 
     project = compute.create_project("dyn-e2e")
     pid = project["project_id"]
     t1 = t2 = None
     try:
-        r1 = compute.create_dynamips_router(pid, "E2E-R1", image, SLOTS)
+        r1 = compute.create_dynamips_router(pid, "E2E-R1", image, SLOTS, idlepc=idlepc)
-        r2 = compute.create_dynamips_router(pid, "E2E-R2", image, SLOTS)
+        r2 = compute.create_dynamips_router(pid, "E2E-R2", image, SLOTS, idlepc=idlepc)
         r1_id, r2_id = r1["node_id"], r2["node_id"]
         t1 = harness.anchor_name(r1_id, *ETH)
         t2 = harness.anchor_name(r2_id, *ETH)
@@ -244,13 +245,14 @@ def test_dynamips_relay_control():
     server = harness.live_server(kernel=False)
     compute = server.compute
     image = _pick_image(server)
+    idlepc = harness.dynamips_idlepc(server, image)
 
     project = compute.create_project("dyn-e2e-relay")
     pid = project["project_id"]
     t1 = None
     try:
-        r1 = compute.create_dynamips_router(pid, "E2E-R1", image, SLOTS)
+        r1 = compute.create_dynamips_router(pid, "E2E-R1", image, SLOTS, idlepc=idlepc)
-        r2 = compute.create_dynamips_router(pid, "E2E-R2", image, SLOTS)
+        r2 = compute.create_dynamips_router(pid, "E2E-R2", image, SLOTS, idlepc=idlepc)
         r1_id, r2_id = r1["node_id"], r2["node_id"]
         t1 = harness.anchor_name(r1_id, *ETH)
 

tests/e2e/test_ethernet_switch_kernel_datapath.py

@@ -67,7 +67,7 @@ def _switch_bridge_name(switch_id):
     return "gns3" + switch_id.replace("-", "")[:6]
 
 
-def _create_topology(compute, pid, image, name):
+def _create_topology(compute, pid, image, name, idlepc=None):
     switch = compute.call(
         "POST",
         f"/projects/{pid}/nodes",
@@ -83,8 +83,8 @@ def _create_topology(compute, pid, image, name):
             },
         },
     )
-    r1 = compute.create_dynamips_router(pid, f"{name}-R1", image, SLOTS)
+    r1 = compute.create_dynamips_router(pid, f"{name}-R1", image, SLOTS, idlepc=idlepc)
-    r2 = compute.create_dynamips_router(pid, f"{name}-R2", image, SLOTS)
+    r2 = compute.create_dynamips_router(pid, f"{name}-R2", image, SLOTS, idlepc=idlepc)
     return switch, r1, r2
 
 
@@ -100,12 +100,13 @@ def test_ethernet_switch_kernel_fast_path():
     if compute.capabilities().get("ubridge_tap") is not True:
         pytest.skip("this compute's uBridge cannot create persistent TAPs (ubridge_tap != True)")
     image = _pick_image(server)
+    idlepc = harness.dynamips_idlepc(server, image)
 
     project = compute.create_project("esw-e2e")
     pid = project["project_id"]
     sw_bridge = None
     try:
-        switch, r1, r2 = _create_topology(compute, pid, image, "E2E")
+        switch, r1, r2 = _create_topology(compute, pid, image, "E2E", idlepc)
         switch_id = switch["node_id"]
         r1_id, r2_id = r1["node_id"], r2["node_id"]
         sw_bridge = _switch_bridge_name(switch_id)
@@ -262,12 +263,13 @@ def test_ethernet_switch_relay_control():
     server = harness.live_server(kernel=False)
     compute = server.compute
     image = _pick_image(server)
+    idlepc = harness.dynamips_idlepc(server, image)
 
     project = compute.create_project("esw-e2e-relay")
     pid = project["project_id"]
     sw_bridge = None
     try:
-        switch, r1, r2 = _create_topology(compute, pid, image, "E2E")
+        switch, r1, r2 = _create_topology(compute, pid, image, "E2E", idlepc)
         sw_bridge = _switch_bridge_name(switch["node_id"])
         r1_id, r2_id = r1["node_id"], r2["node_id"]
         a1 = harness.anchor_name(r1_id, *ETH)