FA-7216 / Transport flow control / Open access
Receive window overlap clips both segment ends · case 01
Receive window overlap clips both segment ends.
ROOT CAUSE
The faulty implementation uses `(start,end)` for the receive-window-overlap-clips-both-segment-ends decision.
VERIFIED REPAIR
Apply the explicit receive-window-overlap-clips-both-segment-ends contract, including the tested boundary and negative cases.
Unsuccessful approach: The attempted repair uses `(max(start,window[0]),end) if start < window[1] else None` and still violates a separate fixture.
Case contract
Bounded offline decision model: receive window overlap clips both segment ends. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.
Why this case matters
This deterministic transport flow control model isolates the receive-window-overlap-clips-both-segment-ends policy at a network component boundary.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(start, end, window):
return (start,end)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(0, 10, (3, 7)), (3, 7))", "check('fixture 2', solve(8, 10, (3, 7)), None)", "check('fixture 3', solve(3, 7, (3, 7)), (3, 7))", "check('fixture 4', solve(0, 3, (3, 7)), None)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
exec(_line)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| fixture 2 | [8, 10] | None | Failed |
| fixture 3 | [3, 7] | [3, 7] | Passed |
| fixture 4 | [0, 3] | None | Failed |
| fixture 1 | [0, 10] | [3, 7] | Failed |
SHA-256 / 0bb48bef59a340c0e486d2ab617ea72e2ffda758f6fc96a3f2305930221c88ee
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(start, end, window):
return (max(start,window[0]),end) if start < window[1] else None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(0, 10, (3, 7)), (3, 7))", "check('fixture 2', solve(8, 10, (3, 7)), None)", "check('fixture 3', solve(3, 7, (3, 7)), (3, 7))", "check('fixture 4', solve(0, 3, (3, 7)), None)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
exec(_line)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| fixture 2 | None | None | Passed |
| fixture 3 | [3, 7] | [3, 7] | Passed |
| fixture 4 | [3, 3] | None | Failed |
| fixture 1 | [3, 10] | [3, 7] | Failed |
SHA-256 / 914475663abd0c6df577e472ed4f58b10bbaeea4a51867a64053e6d1133c9089
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(start, end, window):
return (max(start,window[0]),min(end,window[1])) if max(start,window[0]) < min(end,window[1]) else None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(0, 10, (3, 7)), (3, 7))", "check('fixture 2', solve(8, 10, (3, 7)), None)", "check('fixture 3', solve(3, 7, (3, 7)), (3, 7))", "check('fixture 4', solve(0, 3, (3, 7)), None)"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
exec(_line)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| fixture 2 | None | None | Passed |
| fixture 3 | [3, 7] | [3, 7] | Passed |
| fixture 4 | None | None | Passed |
| fixture 1 | [3, 7] | [3, 7] | Passed |
SHA-256 / a8b170835c2f2dac987532348d42385e4cfe8e3e330d7eae243d2b156cbc7b43
Verification & scope
Bounded deterministic policy model over validated inputs; not a complete protocol stack or an interoperability claim. The five variants rotate the same explicit fixture set. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.
Observations recorded using Python 3.12.14 at 2026-09-29T14:38:09.481684+00:00.
Case digest / a076840ba151112116f16d72ae34ae9325cb7cada6e8e23cc2f4c272e459e245