[Wintun] DEPENDENTLOADFLAG for wintun.dll?

[Jason A. Donenfeld]

Hi Brad,

On Wed, Feb 10, 2021 at 3:04 PM Brad Spencer <bspencer at blackberry.com> wrote:
>
> Would it make sense to link the official wintun.dll with the MSVC
> linker's -DEPENDENTLOADFLAG:0x800 option?
>
> https://docs.microsoft.com/en-us/cpp/build/reference/dependentloadflag
>
> Doing so restricts the search path for immediate dependencies to the
> %windows%\system32\ directory, and I think all of the DLLs Wintun needs
> are there.

That flag is a bit of a can of worms, which I haven't been too
inclined to open. See:
https://skanthak.homepage.t-online.de/snafu.html

Instead, wintun.dll uses delay loading for all DLLs except for
kernel32.dll and ntdll.dll, and then forces the delay loader hook
through LoadLibraryEx. See:
https://git.zx2c4.com/wintun/tree/api/entry.c#n25 You can see this in
action by putting wintun.dll into depends:
https://data.zx2c4.com/depends-for-wintun-dll-feb-2021.png

(CCing Stefan, in case he's curious. The DLLs in question are
https://www.wintun.net/builds/wintun-0.10.1.zip )

Jason