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fix: verify macOS multicast route points to loopback #1502

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Merged
spomichter merged 1 commit into from
Mar 10, 2026
Merged

fix: verify macOS multicast route points to loopback #1502

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11 changes: 8 additions & 3 deletions dimos/protocol/service/system_configurator/lcm.py
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Original file line number Diff line number Diff line change
Expand Up @@ -146,15 +146,20 @@ def __init__(self, loopback_interface: str = "lo0"):
]

def check(self) -> bool:
# `netstat -nr` shows the routing table. We search for a 224/4 route entry.
# `netstat -nr` shows the routing table. We search for a 224/4 route entry
# that points to the loopback interface (lo0). The route often exists on
# en0 (WiFi/Ethernet), which causes cross-process LCM communication to fail.
try:
result = subprocess.run(["netstat", "-nr"], capture_output=True, text=True)
if result.returncode != 0:
print(f"ERROR: `netstat -nr` rc={result.returncode} stderr={result.stderr!r}")
return False

route_ok = ("224.0.0.0/4" in result.stdout) or ("224.0.0/4" in result.stdout)
return bool(route_ok)
for line in result.stdout.splitlines():
if "224.0.0.0/4" in line or "224.0.0/4" in line:
if self.loopback_interface in line:
return True
return False
except Exception as error:
print(f"ERROR: failed checking multicast route via netstat: {error}")
return False
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