lionsoul2014/ip2region · error · Error

invalid bytes ip with length not 4 or 16

Error message

invalid bytes ip with length not 4 or 16

What it means

After confirming the input is a Buffer, ipToString dispatches on length: 4 bytes are rendered as IPv4 and 16 bytes as IPv6. Any other length means the data is not a valid binary IP, so the library throws rather than guessing a format.

Source

Thrown at binding/javascript/util.js:228

            _.push('');
        }
    }

    return _.join(':');
}

// bytes ip to humen-readable string ip
export function ipToString(ipBytes, compress) {
    if (!Buffer.isBuffer(ipBytes)) {
        throw new Error('invalid bytes ip, not a Buffer');
    }

    if (ipBytes.length == 4) {
        return _ipv4_to_string(ipBytes, compress);
    } else if (ipBytes.length == 16) {
        return _ipv6_to_string(ipBytes, compress);
    } else {
        throw new Error('invalid bytes ip with length not 4 or 16');
    }
}

export function ipBytesString(ipBytes) {
    if (!Buffer.isBuffer(ipBytes)) {
        throw new Error('invalid bytes ip, not a Buffer');
    }

    let ps = [];
    for (var i = 0; i < ipBytes.length; i++) {
        ps.push(ipBytes[i] & 0xFF);
    }

    return ps.join('.');
}

// compare two byte ips
// ip2 = buff[offset:ip1.length]

View on GitHub (pinned to c1a1fc7d59)

Solutions

1. Verify the slice length: use exactly 4 bytes for IPv4 and 16 bytes for IPv6 (Buffer.subarray(start, start+4|16)).
2. Store/emit IPs in a fixed width matching their family; pad IPv4 into a 16-byte IPv4-mapped form if you want a single format.
3. Log ipBytes.length at the call site to find which producer emits the bad length.
4. Validate inputs with a length check before calling.

Example fix

// before
const ip = ipToString(buf.subarray(off)); // wrong length
// after
const len = version === 4 ? 4 : 16;
const ip = ipToString(buf.subarray(off, off + len));

function assertIpLength(b) {
  if (!Buffer.isBuffer(b) || (b.length !== 4 && b.length !== 16))
    throw new Error(`ip bytes must be 4 or 16 long, got ${b && b.length}`);
}
assertIpLength(ipBytes);

function isWellSizedIp(b) { return Buffer.isBuffer(b) && (b.length === 4 || b.length === 16); }

try {
  return ipToString(bytes);
} catch (e) {
  if (String(e.message).includes('length not 4 or 16')) {
    throw new Error(`bad ip slice near offset ${off}: length=${bytes.length}`);
  }
  throw e;
}

When it happens

Trigger: Passing a Buffer of wrong size: a truncated slice (e.g. bytes.slice(0, 8)), a 6-byte MAC-style buffer, a zero-length buffer from an empty read, or an IPv4-mapped address stored as 12 bytes.

Common situations: Manual offset arithmetic over the xdb content buffer slicing the wrong byte count; mixing IPv4 and IPv6 records and assuming one size; corrupt or partially written custom data blobs.

Related errors

• invalid bytes ip, not a Buffer
• ip verison not match: xdb file ${xdbFile.getAbsolutePath()}
• incomplete read (${rBytes} read, ${header.HeaderInfoLength}
• incomplete read (${rBytes} read, ${vBytes} expected)
• incomplete read (${rBytes} read, ${stats.size} expected)

AI-assisted analysis of lionsoul2014/ip2region@c1a1fc7d59 (2026-09-02). Data as JSON: /api/errors/4e411b125df662ba. Report an issue: GitHub.