to_sum16
expec = to_sum16(expected_results[len]);
expec = to_sum16((len & 1) ? 0xff00 : 0);
expec = to_sum16(0xff00);
expec = to_sum16(0xffff);
expec = to_sum16(len ? 0xfffe : 0xffff);
CHECK_EQ(to_sum16(expected), csum_result);
CHECK_EQ(to_sum16(expected_csum_ipv6_magic[i]),