netdev - Re: [PATCH bpf-next v2 1/5] selftests/bpf: generalize helpers to control background listener

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Message-Id: <20200506162802.GH241848@google.com>
Date:   Wed, 6 May 2020 09:28:02 -0700
From:   sdf@...gle.com
To:     Martin KaFai Lau <kafai@...com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, davem@...emloft.net,
        ast@...nel.org, daniel@...earbox.net, Andrey Ignatov <rdna@...com>
Subject: Re: [PATCH bpf-next v2 1/5] selftests/bpf: generalize helpers to
 control background listener

On 05/06, Martin KaFai Lau wrote:
> On Tue, May 05, 2020 at 01:27:26PM -0700, Stanislav Fomichev wrote:
> > Move the following routines that let us start a background listener
> > thread and connect to a server by fd to the test_prog:
> > * start_server_thread - start background INADDR_ANY thread
> > * stop_server_thread - stop the thread
> > * connect_to_fd - connect to the server identified by fd
> >
> > These will be used in the next commit.
> The refactoring itself looks fine.

> If I read it correctly, it is a simple connect() test.
> I am not sure a thread is even needed.  accept() is also unnecessary.
> Can all be done in one thread?
I'm looking at the socket address after connection is established (to
verify that the port is the one we were supposed to be using), so
I fail to understand how accept() is unnecessary. Care to clarify?

I thought about doing a "listen() > non-blocking connect() > accept()"
in a single thread instead of background thread, but then decided that
it's better to reuse existing helpers and do proper connection instead
of writing all this new code.