[marios]

Had a quick glance and while the content seems worthwhile I am a little saddened by the code.

There are numerous calls to strcpy() which is a buffer overflow waiting to happen. I know this is not production code but it's just as important. This code is to be used as a learning tool so I think it's important to use correct idioms.

Apologies for nitpicking, but code gets copied, often in a hurry and you get bugs all over the place.

One more comment: in the intro you mention that while the code is mostly tested on Linux, it's likely it works on other Unixes such as Free/OpenBSD. You might want to remind the reader that epoll() is Linux-only (bonus points if you mention the BSDs have something similar called kqueue() :)).

[GuB-42]

strcpy() is actually fine when used with literal/constant strings and the buffer is large enough. The compiler can even optimize it and issue warnings in case of overflow.

However, using strcpy() with arbitrary strings, is a bad idea, even using the safer variants (strncpy, strlcpy, ...) is not ideal. In the case of ZeroHTTPd, the length of the path should be checked during request parsing and a 414 error be returned in case it is too long. Once you know the maximum size of your path, you should be able to size your buffers to do all your manipulation safely, and it includes using strcpy/strcat. I wouldn't recommend it but it can be safe.

Done right, string manipulation in C can be very efficient, it is also very tricky, because you need to be aware of your buffer sizes at all times. Ideally, you should avoid copies.

All the string manipulation trickery may be a little too much for such a simple project and it isn't the point, so I suggest maybe just add a few comments along the lines as "this is unsafe". strncpy() is not the right way to do it, it is just a band-aid so that instead of buffer overflows, you get truncated data, which is usually a less severe bug.

Since we are nitpicking, the return values of system calls like recv() are not properly checked. EINTR and EAGAIN have to be taken into account. It it rarely a problem except when the server is overloaded. And considering that the point of ZeroHTTPd is to measure performance, being robust to such conditions matter.

BTW, flooding your server is very educative. I wrote a small, performance-oriented HTTP server myself (with epoll()) and that's at 100% CPU with all queues full that you realize that you really need to read the man pages. The Linux network stack is pretty stable under load but you need to do your part.

Finally, thank you for your work, I had a feeling that epoll() was "the right way" but I didn't test it. You did ;)

[shuss]

Points well taken, marios. Will try and fix strcpy(). Should certainly mention kqueue(), too. Will fix. Thanks.

[cyberpunk]

OpenBSD doesn't have sendfile as far as I know so maybe s/Open// there too

[shuss]

OpenBSD and FreeBSD do have sendfile(), but args are different compared to the interface presented by Linux. It should be trivial to write a wrapper, though:

https://man.openbsd.org/FreeBSD-11.1/sendfile.2 https://linux.die.net/man/2/sendfile

[cyberpunk]

That manpage is an import from freebsd, not part of base -- As far as I can see on my system it's not there:

OpenBSD:

    $ man 2 sendfile
    man: No entry for sendfile in section 2 of the manual.

    $ grep -rni sendfile /usr/include | wc -l
       0

FreeBSD:

    # grep -rni sendfile /usr/include | wc -l
          30

edit: typo

[dallbee]

On Openbsd you have sosplice, which can be used much like sendfile.

[cyberpunk]

Oh neat, I had no idea that existed. Will have a play, thanks for the tip!

[shuss]

OK, noted. Thanks for sharing.