Comment 5 for bug 1157943

(assuming "David" means me: Better ask Michael Vogt as he is debugging another https problem at the moment)

That said, step 4 is incorrect, Range answers with an error code of 416. The behavior described is that of Range with If-Range.
I haven't tested this at all, but browsing documentation makes me doubt that this is sent by curl (which date it should sent?).

So we need to check for a range error and retry without one – still doesn't really solve the problem as we still get the "wrong" data in the scenario above (just replace "smaller" with "bigger" to have valid ranges).

I guess to really fix this we have to bit the bullet and work with a CURLOPT_HEADERFUNCTION to see what the response is. I might be complete wrong though and will leave that up to someone who actually has access to infrastructure for testing this.