Function isIpv6LinkLocal

lib/net.js:2404–2419

(ip)

};

function isIpv6LinkLocal(ip) {
  if (!isIPv6(ip)) { return false; }

  const ipv6Buffer = convertIpv6StringToBuffer(ip);
  const firstByte = ipv6Buffer[0];  // The first 8 bits
  const secondByte = ipv6Buffer[1]; // The next 8 bits

  // The link-local prefix is `1111111010`, which in hexadecimal is `fe80`
  // First 8 bits (firstByte) should be `11111110` (0xfe)
  // The next 2 bits of the second byte should be `10` (0x80)

  const isFirstByteCorrect = (firstByte === 0xfe); // 0b11111110 == 0xfe
  const isSecondByteCorrect = (secondByte & 0xc0) === 0x80; // 0b10xxxxxx == 0x80

  return isFirstByteCorrect && isSecondByteCorrect;
}

function filterOnlyValidAddress(addresses) {
  // Return the first non IPV6 link-local address if present