netdev - Re: [PATCH bpf 3/3] selftests/bpf: Test freeing sockmap/sockhash with a socket in it

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Date:   Sun, 09 Feb 2020 19:55:35 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Jakub Sitnicki <jakub@...udflare.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>, bpf <bpf@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        kernel-team <kernel-team@...udflare.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: Re: [PATCH bpf 3/3] selftests/bpf: Test freeing sockmap/sockhash with
 a socket in it

Jakub Sitnicki wrote:
> On Sun, Feb 09, 2020 at 03:41 AM CET, Alexei Starovoitov wrote:
> > On Thu, Feb 6, 2020 at 3:28 AM Jakub Sitnicki <jakub@...udflare.com> wrote:
> >>
> >> Commit 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during tear
> >> down") introduced sleeping issues inside RCU critical sections and while
> >> holding a spinlock on sockmap/sockhash tear-down. There has to be at least
> >> one socket in the map for the problem to surface.
> >>
> >> This adds a test that triggers the warnings for broken locking rules. Not a
> >> fix per se, but rather tooling to verify the accompanying fixes. Run on a
> >> VM with 1 vCPU to reproduce the warnings.
> >>
> >> Fixes: 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during tear down")
> >> Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
> >
> > selftests/bpf no longer builds for me.
> > make
> >   BINARY   test_maps
> >   TEST-OBJ [test_progs] sockmap_basic.test.o
> > /data/users/ast/net/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c:
> > In function ‘connected_socket_v4’:
> > /data/users/ast/net/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c:20:11:
> > error: ‘TCP_REPAIR_ON’ undeclared (first use in this function); did
> > you mean ‘TCP_REPAIR’?
> >    20 |  repair = TCP_REPAIR_ON;
> >       |           ^~~~~~~~~~~~~
> >       |           TCP_REPAIR
> > /data/users/ast/net/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c:20:11:
> > note: each undeclared identifier is reported only once for each
> > function it appears in
> > /data/users/ast/net/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c:29:11:
> > error: ‘TCP_REPAIR_OFF_NO_WP’ undeclared (first use in this function);
> > did you mean ‘TCP_REPAIR_OPTIONS’?
> >    29 |  repair = TCP_REPAIR_OFF_NO_WP;
> >       |           ^~~~~~~~~~~~~~~~~~~~
> >       |           TCP_REPAIR_OPTIONS
> >
> > Clearly /usr/include/linux/tcp.h is too old.
> > Suggestions?
> 
> Sorry for the inconvenience. I see that tcp.h header is missing under
> linux/tools/include/uapi/.

How about we just add the couple defines needed to sockmap_basic.c I don't
see a need to pull in all of tcp.h just for a couple defines that wont
change anyways.

> 
> I have been building against my distro kernel headers, completely
> unaware of this. This is an oversight on my side.
> 
> Can I ask for a revert? I'm traveling today with limited ability to
> post patches.

I don't think we need a full revert.

> 
> I can resubmit the test with the missing header for bpf-next once it
> reopens.

If you are traveling I'll post a patch with the defines.