Files
bigbrother/tests/test_interface_detection.py
Cobra 3153b7e8a3 Robust interface detection — retry fallback chain for headless boot (#206)
Fixes interface auto-detection failures on Pi Zero 2W where wlan0 doesn't exist
at boot. Implementation:

- Added detect_interface_with_retry() function with 3x retry fallback chain
- Config-supplied interface preferred, then /proc/net/route, then UP interface
- Exponential backoff: 5s, 10s, 20s delays between retries
- Filters excluded prefixes: lo, tailscale*, wg*, tun*, docker*, veth*, br-*
- Used in Engine.__init__(), PacketCapture.start(), MacManager.start()
- Full test coverage: 10 tests for detection, backoff, filtering

Addresses issue where network stack initializes after boot and interfaces
become available after 5-10 second delay.
2026-04-08 20:58:43 -04:00

120 lines
5.8 KiB
Python

"""Tests for interface detection with retry fallback chain."""
import time
from pathlib import Path
from unittest.mock import patch, MagicMock
from tempfile import TemporaryDirectory
import pytest
from utils.networking import get_primary_interface, detect_interface_with_retry
class TestInterfaceDetection:
"""Test robust interface detection with retry fallback."""
def test_get_primary_interface_from_route_table(self):
"""get_primary_interface reads default route from /proc/net/route."""
route_content = """Iface Destination Gateway Flags RefCnt Use Metric Mask MTU Window IRTT
eth0 00000000 0101010A 0003 0 0 100 00000000 0 0 0
eth0 0101010A 00000000 0001 0 0 100 FFFFFFFF 0 0 0
"""
with patch("builtins.open", create=True) as mock_open:
mock_open.return_value.__enter__.return_value.readlines.return_value = route_content.split("\n")
result = get_primary_interface()
assert result == "eth0"
def test_get_primary_interface_fallback_eth(self):
"""get_primary_interface falls back to eth* interfaces if /proc/net/route is empty."""
with patch("builtins.open", side_effect=IOError):
with patch("utils.networking.get_all_interfaces", return_value=["eth0", "eth1"]):
result = get_primary_interface()
assert result == "eth0"
def test_get_primary_interface_fallback_wlan(self):
"""get_primary_interface falls back to first interface if no eth/en."""
with patch("builtins.open", side_effect=IOError):
with patch("utils.networking.get_all_interfaces", return_value=["wlan0"]):
result = get_primary_interface()
assert result == "wlan0"
def test_get_primary_interface_no_interfaces(self):
"""get_primary_interface returns None if no interfaces available."""
with patch("builtins.open", side_effect=IOError):
with patch("utils.networking.get_all_interfaces", return_value=[]):
result = get_primary_interface()
assert result is None
def test_detect_interface_with_retry_immediate_success(self):
"""detect_interface_with_retry returns interface immediately if found."""
with patch("utils.networking.get_primary_interface", return_value="eth0"):
result = detect_interface_with_retry(max_retries=3, retry_delay=1)
assert result == "eth0"
def test_detect_interface_with_retry_eventual_success(self):
"""detect_interface_with_retry retries and succeeds after N attempts."""
call_count = [0]
def get_iface_side_effect():
call_count[0] += 1
if call_count[0] <= 2:
return None # Fail first 2 times
return "wlan0" # Succeed on 3rd call
with patch("utils.networking.get_primary_interface", side_effect=get_iface_side_effect):
with patch("utils.networking._get_up_interface", return_value=None):
result = detect_interface_with_retry(max_retries=3, retry_delay=0.01)
assert result == "wlan0"
assert call_count[0] == 3
def test_detect_interface_with_retry_exhausted(self):
"""detect_interface_with_retry returns None if all retries exhausted."""
with patch("utils.networking.get_primary_interface", return_value=None):
with patch("utils.networking._get_up_interface", return_value=None):
result = detect_interface_with_retry(max_retries=2, retry_delay=0.01)
assert result is None
def test_detect_interface_with_retry_uses_config_fallback(self):
"""detect_interface_with_retry accepts config-set interface as ultimate fallback."""
with patch("utils.networking.get_primary_interface", return_value=None):
with patch("utils.networking._get_up_interface", return_value=None):
result = detect_interface_with_retry(
max_retries=1,
retry_delay=0.01,
config_interface="configured_iface"
)
# Should use config fallback when detection fails
assert result == "configured_iface"
def test_detect_interface_exponential_backoff(self):
"""detect_interface_with_retry uses exponential backoff (5s, 10s, 20s)."""
call_times = []
def get_iface_with_timing():
call_times.append(time.time())
return None
with patch("utils.networking.get_primary_interface", side_effect=get_iface_with_timing):
with patch("utils.networking._get_up_interface", return_value=None):
with patch("time.sleep") as mock_sleep:
result = detect_interface_with_retry(
max_retries=3,
retry_delay=5, # Base delay
exponential=True
)
# Should have called sleep with 5, 10, 20
assert mock_sleep.call_count == 3
# Check exponential backoff values (5 * 2^0, 5 * 2^1, 5 * 2^2)
sleep_calls = [call[0][0] for call in mock_sleep.call_args_list]
assert sleep_calls == [5, 10, 20]
def test_detect_interface_filters_excluded(self):
"""detect_interface_with_retry excludes lo, tailscale*, wg*, tun*, docker*, veth*, br-*."""
excluded_ifaces = ["lo", "tailscale0", "wg0", "tun0", "docker0", "veth123", "br-abc"]
with patch("utils.networking.get_primary_interface", return_value=None):
# Mock get_all_interfaces to return only excluded ones
with patch("utils.networking.get_all_interfaces", return_value=excluded_ifaces):
result = detect_interface_with_retry(max_retries=1, retry_delay=0.01)
assert result is None