private CidrBlock addByteRaw(int byteOffset, int n) {
        BigInteger bit = addressInteger.add(BigInteger.valueOf(n).shiftLeft(addressLength - 8 * (byteOffset + 1)));
        return new CidrBlock(bit, prefixLength, addressLength);
    }
Add 'n' to the byte at the given offset, truncating overflow bits.  0 refers to the most significant byte of the address.
vespajlib/src/main/java/ai/vespa/net/CidrBlock.java