FAILURE MAP
← Case archive

FA-27526 / HTTP ranges / Open access

A zero-copy range sender accounts for partial progress reported with syscall errors: an interrupted zero-byte syscall is rescheduled without declaring EOF · case 01

A zero-copy range sender accounts for partial progress reported with syscall errors: an interrupted zero-byte syscall is rescheduled without declaring EOF.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The sendfile-range-events-interrupt-zero decision uses offset=x['offset'] remaining=x['remaining'] state='running' opened=True out=[] for accepted,error in x['events']: if state in ('complete','aborted','truncated'): out.append([offset,remaining,state,opened]) continue if accepted<0 or accepted>remaining: state='aborted' opened=False out.append([offset,remaining,state,opened]) continue offset+=accepted remaining-=accepted if error=='fatal': state='aborted' elif remaining==0: state='complete' elif error=='again': state='blocked' elif error=='interrupt': state='truncated' elif accepted==0: state='truncated' else: state='running' opened=state not in ('complete','aborted','truncated') out.append([offset,remaining,state,opened]) return out.

VERIFIED REPAIR

Apply the bounded decision exactly: offset=x['offset'] remaining=x['remaining'] state='running' opened=True out=[] for accepted,error in x['events']: if state in ('complete','aborted','truncated'): out.append([offset,remaining,state,opened]) continue if accepted<0 or accepted>remaining: state='aborted' opened=False out.append([offset,remaining,state,opened]) continue offset+=accepted remaining-=accepted if error=='fatal': state='aborted' elif remaining==0: state='complete' elif error=='again': state='blocked' elif error=='interrupt': state='running' elif accepted==0: state='truncated' else: state='running' opened=state not in ('complete','aborted','truncated') out.append([offset,remaining,state,opened]) return out

Unsuccessful approach: The partial repair uses offset=x['offset'] remaining=x['remaining'] state='running' opened=True out=[] for accepted,error in x['events']: if state in ('complete','aborted','truncated'): out.append([offset,remaining,state,opened]) continue if accepted<0 or accepted>remaining: state='aborted' opened=False out.append([offset,remaining,state,opened]) continue offset+=accepted remaining-=accepted if error=='fatal': state='aborted' elif remaining==0: state='complete' elif error=='again': state='blocked' elif error=='interrupt': state='blocked' elif accepted==0: state='truncated' else: state='running' opened=state not in ('complete','aborted','truncated') out.append([offset,remaining,state,opened]) return out, which still violates the stated contract.

Case contract

x contains absolute offset, remaining promised bytes, and syscall events [accepted,error], where error is none,again,interrupt,fatal. Counts outside0..remaining abort without advancing. Valid accepted bytes advance even when again or interrupt accompanies them. Fatal errors abort; zero remaining completes; again blocks; interrupt reschedules; zero bytes with none truncates. Terminal states ignore later events. Return state snapshots [offset,remaining,state,handle-open] after each event.

Why this case matters

Range responses combine representation identity, conditional requests, framing, and partial-object state.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    offset=x['offset']
    remaining=x['remaining']
    state='running'
    opened=True
    out=[]
    for accepted,error in x['events']:
        if state in ('complete','aborted','truncated'):
            out.append([offset,remaining,state,opened])
            continue
        if accepted<0 or accepted>remaining:
            state='aborted'
            opened=False
            out.append([offset,remaining,state,opened])
            continue
        offset+=accepted
        remaining-=accepted
        if error=='fatal': state='aborted'
        elif remaining==0: state='complete'
        elif error=='again': state='blocked'
        elif error=='interrupt': state='truncated'
        elif accepted==0: state='truncated'
        else: state='running'
        opened=state not in ('complete','aborted','truncated')
        out.append([offset,remaining,state,opened])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('interrupt-zero fixture 0', json.loads(json.dumps(solve({'offset':10,'remaining':5,'events':[[2,'interrupt'],[1,'again'],[2,'none']]}))), json.loads(json.dumps([[12,3,'running',True],[13,2,'blocked',True],[15,0,'complete',False]])))
check('interrupt-zero fixture 1', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[0,'again'],[0,'interrupt'],[0,'none'],[1,'none']]}))), json.loads(json.dumps([[0,2,'blocked',True],[0,2,'running',True],[0,2,'truncated',False],[0,2,'truncated',False]])))
check('interrupt-zero fixture 2', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[1,'fatal'],[1,'none']]}))), json.loads(json.dumps([[1,1,'aborted',False],[1,1,'aborted',False]])))
check('interrupt-zero fixture 3', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[-1,'none']]}))), json.loads(json.dumps([[0,2,'aborted',False]])))
check('interrupt-zero fixture 4', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[3,'none']]}))), json.loads(json.dumps([[0,2,'aborted',False]])))
check('interrupt-zero fixture 5', json.loads(json.dumps(solve({'offset':N,'remaining':N,'events':[[N,'again'],[0,'fatal']]}))), json.loads(json.dumps([[2*N,0,'complete',False],[2*N,0,'complete',False]])))
check('interrupt-zero fixture 6', json.loads(json.dumps(solve({'offset':0,'remaining':0,'events':[[0,'none']]}))), json.loads(json.dumps([[0,0,'complete',False]])))
check('interrupt-zero fixture 7', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[2,'fatal']]}))), json.loads(json.dumps([[2,0,'aborted',False]])))
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 fixtureActualExpectedOutcome
interrupt-zero fixture 0[[12, 3, 'truncated', False], [12, 3, 'truncated', False], [12, 3, 'truncated', False]][[12, 3, 'running', True], [13, 2, 'blocked', True], [15, 0, 'complete', False]]Failed
interrupt-zero fixture 1[[0, 2, 'blocked', True], [0, 2, 'truncated', False], [0, 2, 'truncated', False], [0, 2, 'truncated', False]][[0, 2, 'blocked', True], [0, 2, 'running', True], [0, 2, 'truncated', False], [0, 2, 'truncated', False]]Failed
interrupt-zero fixture 2[[1, 1, 'aborted', False], [1, 1, 'aborted', False]][[1, 1, 'aborted', False], [1, 1, 'aborted', False]]Passed
interrupt-zero fixture 3[[0, 2, 'aborted', False]][[0, 2, 'aborted', False]]Passed
interrupt-zero fixture 4[[0, 2, 'aborted', False]][[0, 2, 'aborted', False]]Passed
interrupt-zero fixture 5[[2, 0, 'complete', False], [2, 0, 'complete', False]][[2, 0, 'complete', False], [2, 0, 'complete', False]]Passed
interrupt-zero fixture 6[[0, 0, 'complete', False]][[0, 0, 'complete', False]]Passed
interrupt-zero fixture 7[[2, 0, 'aborted', False]][[2, 0, 'aborted', False]]Passed

SHA-256 / 69645e3e1dc1b499384bcd0f6375bfbfbf226aae90430b5bebcd9e5f801700be

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    offset=x['offset']
    remaining=x['remaining']
    state='running'
    opened=True
    out=[]
    for accepted,error in x['events']:
        if state in ('complete','aborted','truncated'):
            out.append([offset,remaining,state,opened])
            continue
        if accepted<0 or accepted>remaining:
            state='aborted'
            opened=False
            out.append([offset,remaining,state,opened])
            continue
        offset+=accepted
        remaining-=accepted
        if error=='fatal': state='aborted'
        elif remaining==0: state='complete'
        elif error=='again': state='blocked'
        elif error=='interrupt': state='blocked'
        elif accepted==0: state='truncated'
        else: state='running'
        opened=state not in ('complete','aborted','truncated')
        out.append([offset,remaining,state,opened])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('interrupt-zero fixture 0', json.loads(json.dumps(solve({'offset':10,'remaining':5,'events':[[2,'interrupt'],[1,'again'],[2,'none']]}))), json.loads(json.dumps([[12,3,'running',True],[13,2,'blocked',True],[15,0,'complete',False]])))
check('interrupt-zero fixture 1', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[0,'again'],[0,'interrupt'],[0,'none'],[1,'none']]}))), json.loads(json.dumps([[0,2,'blocked',True],[0,2,'running',True],[0,2,'truncated',False],[0,2,'truncated',False]])))
check('interrupt-zero fixture 2', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[1,'fatal'],[1,'none']]}))), json.loads(json.dumps([[1,1,'aborted',False],[1,1,'aborted',False]])))
check('interrupt-zero fixture 3', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[-1,'none']]}))), json.loads(json.dumps([[0,2,'aborted',False]])))
check('interrupt-zero fixture 4', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[3,'none']]}))), json.loads(json.dumps([[0,2,'aborted',False]])))
check('interrupt-zero fixture 5', json.loads(json.dumps(solve({'offset':N,'remaining':N,'events':[[N,'again'],[0,'fatal']]}))), json.loads(json.dumps([[2*N,0,'complete',False],[2*N,0,'complete',False]])))
check('interrupt-zero fixture 6', json.loads(json.dumps(solve({'offset':0,'remaining':0,'events':[[0,'none']]}))), json.loads(json.dumps([[0,0,'complete',False]])))
check('interrupt-zero fixture 7', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[2,'fatal']]}))), json.loads(json.dumps([[2,0,'aborted',False]])))
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 fixtureActualExpectedOutcome
interrupt-zero fixture 0[[12, 3, 'blocked', True], [13, 2, 'blocked', True], [15, 0, 'complete', False]][[12, 3, 'running', True], [13, 2, 'blocked', True], [15, 0, 'complete', False]]Failed
interrupt-zero fixture 1[[0, 2, 'blocked', True], [0, 2, 'blocked', True], [0, 2, 'truncated', False], [0, 2, 'truncated', False]][[0, 2, 'blocked', True], [0, 2, 'running', True], [0, 2, 'truncated', False], [0, 2, 'truncated', False]]Failed
interrupt-zero fixture 2[[1, 1, 'aborted', False], [1, 1, 'aborted', False]][[1, 1, 'aborted', False], [1, 1, 'aborted', False]]Passed
interrupt-zero fixture 3[[0, 2, 'aborted', False]][[0, 2, 'aborted', False]]Passed
interrupt-zero fixture 4[[0, 2, 'aborted', False]][[0, 2, 'aborted', False]]Passed
interrupt-zero fixture 5[[2, 0, 'complete', False], [2, 0, 'complete', False]][[2, 0, 'complete', False], [2, 0, 'complete', False]]Passed
interrupt-zero fixture 6[[0, 0, 'complete', False]][[0, 0, 'complete', False]]Passed
interrupt-zero fixture 7[[2, 0, 'aborted', False]][[2, 0, 'aborted', False]]Passed

SHA-256 / 764737d6f35fae3986baa82062542a8863dad77b022566156daef2530589cb9e

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    offset=x['offset']
    remaining=x['remaining']
    state='running'
    opened=True
    out=[]
    for accepted,error in x['events']:
        if state in ('complete','aborted','truncated'):
            out.append([offset,remaining,state,opened])
            continue
        if accepted<0 or accepted>remaining:
            state='aborted'
            opened=False
            out.append([offset,remaining,state,opened])
            continue
        offset+=accepted
        remaining-=accepted
        if error=='fatal': state='aborted'
        elif remaining==0: state='complete'
        elif error=='again': state='blocked'
        elif error=='interrupt': state='running'
        elif accepted==0: state='truncated'
        else: state='running'
        opened=state not in ('complete','aborted','truncated')
        out.append([offset,remaining,state,opened])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('interrupt-zero fixture 0', json.loads(json.dumps(solve({'offset':10,'remaining':5,'events':[[2,'interrupt'],[1,'again'],[2,'none']]}))), json.loads(json.dumps([[12,3,'running',True],[13,2,'blocked',True],[15,0,'complete',False]])))
check('interrupt-zero fixture 1', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[0,'again'],[0,'interrupt'],[0,'none'],[1,'none']]}))), json.loads(json.dumps([[0,2,'blocked',True],[0,2,'running',True],[0,2,'truncated',False],[0,2,'truncated',False]])))
check('interrupt-zero fixture 2', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[1,'fatal'],[1,'none']]}))), json.loads(json.dumps([[1,1,'aborted',False],[1,1,'aborted',False]])))
check('interrupt-zero fixture 3', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[-1,'none']]}))), json.loads(json.dumps([[0,2,'aborted',False]])))
check('interrupt-zero fixture 4', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[3,'none']]}))), json.loads(json.dumps([[0,2,'aborted',False]])))
check('interrupt-zero fixture 5', json.loads(json.dumps(solve({'offset':N,'remaining':N,'events':[[N,'again'],[0,'fatal']]}))), json.loads(json.dumps([[2*N,0,'complete',False],[2*N,0,'complete',False]])))
check('interrupt-zero fixture 6', json.loads(json.dumps(solve({'offset':0,'remaining':0,'events':[[0,'none']]}))), json.loads(json.dumps([[0,0,'complete',False]])))
check('interrupt-zero fixture 7', json.loads(json.dumps(solve({'offset':0,'remaining':2,'events':[[2,'fatal']]}))), json.loads(json.dumps([[2,0,'aborted',False]])))
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 fixtureActualExpectedOutcome
interrupt-zero fixture 0[[12, 3, 'running', True], [13, 2, 'blocked', True], [15, 0, 'complete', False]][[12, 3, 'running', True], [13, 2, 'blocked', True], [15, 0, 'complete', False]]Passed
interrupt-zero fixture 1[[0, 2, 'blocked', True], [0, 2, 'running', True], [0, 2, 'truncated', False], [0, 2, 'truncated', False]][[0, 2, 'blocked', True], [0, 2, 'running', True], [0, 2, 'truncated', False], [0, 2, 'truncated', False]]Passed
interrupt-zero fixture 2[[1, 1, 'aborted', False], [1, 1, 'aborted', False]][[1, 1, 'aborted', False], [1, 1, 'aborted', False]]Passed
interrupt-zero fixture 3[[0, 2, 'aborted', False]][[0, 2, 'aborted', False]]Passed
interrupt-zero fixture 4[[0, 2, 'aborted', False]][[0, 2, 'aborted', False]]Passed
interrupt-zero fixture 5[[2, 0, 'complete', False], [2, 0, 'complete', False]][[2, 0, 'complete', False], [2, 0, 'complete', False]]Passed
interrupt-zero fixture 6[[0, 0, 'complete', False]][[0, 0, 'complete', False]]Passed
interrupt-zero fixture 7[[2, 0, 'aborted', False]][[2, 0, 'aborted', False]]Passed

SHA-256 / 6f6754f4a3c5fc5d8910d790d5fa97e1ef18d841f7f2f300e54e7aa1076f175d

Verification & scope

Deterministic simplified range service, with stipulated local policies and already parsed trusted inputs; not a complete HTTP implementation. 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 2026-09-29T14:41:25.829773+00:00.

Case digest / f72dbfc77e649d178c6675a769c1615cbd75673c14b68fe33e111f81e51b1ad9