In OpenSSL, they create socket BIOs. The distinction isn't important on UNIX.
On Windows, file descriptors are provided by the C runtime, while sockets must
use separate recv and send APIs. Document how these APIs are intended to work.
Also add a TODO to resolve the SOCKET vs int thing. This code assumes that
Windows HANDLEs only use the bottom 32 bits of precision. (Which is currently
true and probably will continue to be true for the foreseeable future[*], but
it'd be nice to do this right.)
Thanks to Gisle Vanem and Daniel Stenberg for reporting the bug.
[*] Both so Windows can continue to run 32-bit programs and because of all the
random UNIX software, like OpenSSL and ourselves, out there which happily
assumes sockets are ints.
Change-Id: I67408c218572228cb1a7d269892513cda4261c82
Reviewed-on: https://boringssl-review.googlesource.com/7333
Reviewed-by: David Benjamin <davidben@google.com>