When a phrase ends with a period, do you put ... or .. after it?

I was just reading this question: When "etc." is at the end of a phrase, do you place a period after it?

And it brought to mind something similar. If a phrase ends with a . (such as e.g. or etc.), and you want to use ..., how many periods should you put?

That is, which of these is correct?

something something etc...

something something etc....

To preempt the objection that ellipses never follow abbreviations, they can when used for aposiopesis in dialogue.

Answer

An ellipsis is always 3 dots. A period is always one dot. If you need both an ellipsis and a period, that totals up to 4 dots.

Chicago Manual of Style, 14th Edition, section 10.55:

When the last part of a quoted sentence is omitted and what remains is still grammatically complete, four dots—a period followed by three ellipsis dots—are used to indicate the omission.

Ideally the ellipsis would be set distinctly from the period, using for example the Unicode Horizontal Ellipsis codepoint (U+2026):

…

Although the CMoS indicates "period followed by ellipsis", I believe that sometimes the ellipsis may come before the period, depending on the nature of your sentence.