FA-7351 / DNS resolution / Open access
Dns negative ttl is minimum of soa ttl and minimum field · case 01
Dns negative ttl is minimum of soa ttl and minimum field.
ROOT CAUSE
The faulty implementation uses `soa_ttl` for the dns-negative-ttl-is-minimum-of-soa-ttl-and-minimum-field decision.
VERIFIED REPAIR
Apply the explicit dns-negative-ttl-is-minimum-of-soa-ttl-and-minimum-field contract, including the tested boundary and negative cases.
Unsuccessful approach: The attempted repair uses `max(soa_ttl,minimum)` and still violates a separate fixture.
Case contract
Bounded offline decision model: dns negative ttl is minimum of soa ttl and minimum field. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.
Why this case matters
This deterministic dns resolution model isolates the dns-negative-ttl-is-minimum-of-soa-ttl-and-minimum-field 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(soa_ttl, minimum):
return soa_ttl
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(300, 60), 60)", "check('fixture 2', solve(30, 60), 30)", "check('fixture 3', solve(0, 60), 0)", "check('fixture 4', solve(60, 60), 60)"]
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 | 30 | 30 | Passed |
| fixture 3 | 0 | 0 | Passed |
| fixture 4 | 60 | 60 | Passed |
| fixture 1 | 300 | 60 | Failed |
SHA-256 / e427e0909b8bccafcc979952df6c7c4c96d8067e6c9cf089e4e79a0391c5d368
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(soa_ttl, minimum):
return max(soa_ttl,minimum)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(300, 60), 60)", "check('fixture 2', solve(30, 60), 30)", "check('fixture 3', solve(0, 60), 0)", "check('fixture 4', solve(60, 60), 60)"]
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 | 60 | 30 | Failed |
| fixture 3 | 60 | 0 | Failed |
| fixture 4 | 60 | 60 | Passed |
| fixture 1 | 300 | 60 | Failed |
SHA-256 / eec872345dfe11ba8e0a24092ffdf9df7fa503a23cb7c36ce00636366bf757ce
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(soa_ttl, minimum):
return min(soa_ttl,minimum)
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve(300, 60), 60)", "check('fixture 2', solve(30, 60), 30)", "check('fixture 3', solve(0, 60), 0)", "check('fixture 4', solve(60, 60), 60)"]
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 | 30 | 30 | Passed |
| fixture 3 | 0 | 0 | Passed |
| fixture 4 | 60 | 60 | Passed |
| fixture 1 | 60 | 60 | Passed |
SHA-256 / 62e8d57cac23ab21af455fd3d5bebec2fc568042eac34b937b1700baf8b68492
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 2026-09-29T14:38:10.909650+00:00.
Case digest / f77a6bb73e9295bdc7f88e01dee8757a38a5c8cc125be35e2ddef8f676a9ba10