[asio-users] Usage of FIONBIO causes problems on FreeBSD

[Vinícius d. S. O. <vin...@gm...>]

I've been facing problems trying to use Github, so I can't report issues
(nor send PRs) through Github.

For now, I'll just report issues here in the list.

In the last months I made extensive use of Boost.Asio on FreeBSD and I
faced some problems. Almost all of them were related to indiscriminate
usage of FIONBIO. By doing a quick search on Google I found out this
ioctl() kinda predates POSIX and had inconsistent behaviour among different
systems and even different objects in the same system. So it was a surprise
to learn that Boost.Asio favours FIONBIO over fcntl().

A quick search for FIONBIO on ASIO's repo reveals it's not the first time
this ioctl causes problems:
https://github.com/chriskohlhoff/asio/commit/607f99ba80df71f1a96f0df71725059ee71e46ff

For FreeBSD, the first problem I faced was related to Capsicum. Sending a
Capsicum-protected file descriptor over an UNIX socket to a Boost.Asio
process will block usage of ioctls on the file descriptor. The call for
FIONBIO fails with ENOTCAPABLE and Boost.Asio refuses to work with the
object for no good reason.

The second problem I faced was trying to use posix::stream_descriptor to
monitor a kqueue file descriptor. Boost.Asio doesn't try to support every
feature the underlying system has so it offers some escape latches and
posix::stream_descriptor is just one of these. However,
posix::stream_descriptor will perform FIONBIO on the underlying descriptor
(which of course isn't supported on kqueue file descriptors nor on many
other file descriptors). This will cause async_wait() to fail.

I think any usage of FIONBIO on Boost.Asio codebase should just be removed
altogether. Recently ASIO started to require C++11 which is way way newer
than fcntl() so it doesn't make sense to still depend on such problematic
ioctl().

I have more issues to report (not all of them related to FreeBSD), but
indiscriminate usage of ioctls (FIONBIO) is one that really bites my back
and it's the only one I feel compelled to report sooner even if Github is
playing games with me.


-- 
Vinícius dos Santos Oliveira
https://vinipsmaker.github.io/