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https://github.com/Horizontal42/netsleuth.git
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a64022b12a
Shipped half of the original design on purpose: generalizing BSD's alt: same-TTL annotation across backends is impossible - mtr's JSON aggregates cycles and discards per-cycle next-hop variance, icmp_win/icmplib send one probe per TTL by construction, and the Linux system-traceroute parser doesn't model multi-IP hops even though the text can contain them. A finding that only ever fires on macOS/Linux-system-binary would be worse than not having it. New probes/ecmp.py::detect_ecmp() takes N independently-run TraceResults for the same target and diffs which IP showed up at each TTL - pure and backend-agnostic, since it never touches capability detection. Flags path.ecmp (info, multiple next hops exist - normal on a load-balanced network) and path.ecmp_asymmetric (warn, branches differ by >20ms - the diagnostic case, since one degraded branch of a load-balanced pair causes intermittent slowness a single traceroute would never catch). --ecmp is opt-in and deliberately excluded from --full: it multiplies traceroute traffic against the same targets by ecmp.runs (capped at 5) across ecmp.max_targets (capped at 3), sequential and sharing one semaphore, only after the main fan-out has finished. Live-tested against 2 real targets x 3 runs each - ran cleanly, correctly reported no divergence on this network. Part of plans/zesty-zooming-wilkinson.md (gitignored).
104 lines
3.2 KiB
Python
104 lines
3.2 KiB
Python
from __future__ import annotations
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from netsleuth.interpret import ecmp_findings
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from netsleuth.models import TraceHop, TraceResult
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from netsleuth.probes.ecmp import detect_ecmp
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def hop(ttl: int, ip: str | None, avg_ms: float | None = 10.0, asn: str | None = None) -> TraceHop:
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return TraceHop(ttl=ttl, ip=ip, avg_ms=avg_ms, asn=asn)
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def trace(*hops: TraceHop, target: str = "1.1.1.1") -> TraceResult:
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return TraceResult(target=target, hops=list(hops))
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def test_detect_ecmp_on_a_single_run_has_no_divergence():
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report = detect_ecmp([trace(hop(1, "192.168.1.1"), hop(2, "1.1.1.1"))])
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assert report.divergent_ttls == []
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assert report.runs == 1
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def test_detect_ecmp_on_three_identical_runs_has_no_divergence():
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runs = [trace(hop(1, "192.168.1.1"), hop(2, "1.1.1.1")) for _ in range(3)]
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report = detect_ecmp(runs)
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assert report.divergent_ttls == []
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assert report.runs == 3
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def test_detect_ecmp_flags_a_ttl_with_different_next_hops():
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runs = [
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trace(hop(1, "192.168.1.1"), hop(2, "10.0.0.1")),
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trace(hop(1, "192.168.1.1"), hop(2, "10.0.0.2")),
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trace(hop(1, "192.168.1.1"), hop(2, "10.0.0.1")),
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]
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report = detect_ecmp(runs)
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assert report.divergent_ttls == [2]
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hop2 = next(h for h in report.hops if h.ttl == 2)
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assert set(hop2.ips) == {"10.0.0.1", "10.0.0.2"}
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def test_detect_ecmp_computes_a_large_rtt_gap_between_branches():
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runs = [
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trace(hop(1, "10.0.0.1", avg_ms=10.0)),
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trace(hop(1, "10.0.0.2", avg_ms=80.0)),
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]
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report = detect_ecmp(runs)
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hop1 = report.hops[0]
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assert hop1.rtt_spread_ms == 70.0
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def test_detect_ecmp_handles_runs_of_differing_length():
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runs = [
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trace(hop(1, "10.0.0.1"), hop(2, "1.1.1.1")),
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trace(hop(1, "10.0.0.1")),
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]
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report = detect_ecmp(runs)
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assert report.divergent_ttls == []
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assert {h.ttl for h in report.hops} == {1, 2}
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def test_detect_ecmp_excludes_none_ip_hops():
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runs = [
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trace(hop(1, "10.0.0.1")),
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trace(hop(1, None)),
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]
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report = detect_ecmp(runs)
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assert report.hops[0].ips == ["10.0.0.1"]
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assert report.divergent_ttls == []
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def test_detect_ecmp_on_no_runs():
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report = detect_ecmp([])
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assert report.hops == []
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assert report.runs == 0
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def test_ecmp_findings_silent_when_no_divergence():
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report = detect_ecmp([trace(hop(1, "10.0.0.1"))])
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assert ecmp_findings(report) == []
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def test_ecmp_findings_info_when_divergent_but_close_in_rtt():
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runs = [
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trace(hop(1, "10.0.0.1", avg_ms=10.0)),
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trace(hop(1, "10.0.0.2", avg_ms=12.0)),
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]
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report = detect_ecmp(runs)
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findings = ecmp_findings(report)
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assert [f.id for f in findings] == [f"path.ecmp.{report.target}"]
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assert findings[0].severity == "info"
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def test_ecmp_findings_warns_on_asymmetric_branches():
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runs = [
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trace(hop(1, "10.0.0.1", avg_ms=10.0)),
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trace(hop(1, "10.0.0.2", avg_ms=80.0)),
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]
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report = detect_ecmp(runs)
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findings = ecmp_findings(report)
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ids = [f.id for f in findings]
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assert f"path.ecmp.{report.target}" in ids
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assert f"path.ecmp_asymmetric.{report.target}" in ids
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asymmetric = [f for f in findings if f.id.startswith("path.ecmp_asymmetric")][0]
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assert asymmetric.severity == "warn"
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