is this done for more reliability ? or indeed this is useless and not needed ?

The general approach reminds me a bit of Jon Oberheide’s half-nelson.c, which involves colliding two Linux kernel stacks.

> I found it interesting that the code looks as though it may have been written with memory management issues in mind, as the check to ensure content_length is not zero would catch an integer overflow caused by adding one to the value.

I think they’re just checking that content_length got set within the for loop. At any rate, content_length is a signed int, so overflow behavior is undefined — of course, many developers don’t know this.