netdev - Re: [PATCH bpf-next v9 0/9] bpf: getsockopt and setsockopt hooks

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Date:   Thu, 27 Jun 2019 15:43:41 -0700
From:   Stanislav Fomichev <sdf@...ichev.me>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Stanislav Fomichev <sdf@...gle.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, davem@...emloft.net, ast@...nel.org,
        daniel@...earbox.net
Subject: Re: [PATCH bpf-next v9 0/9] bpf: getsockopt and setsockopt hooks

On 06/27, Alexei Starovoitov wrote:
> On Thu, Jun 27, 2019 at 01:38:46PM -0700, Stanislav Fomichev wrote:
> > This series implements two new per-cgroup hooks: getsockopt and
> > setsockopt along with a new sockopt program type. The idea is pretty
> > similar to recently introduced cgroup sysctl hooks, but
> > implementation is simpler (no need to convert to/from strings).
> > 
> > What this can be applied to:
> > * move business logic of what tos/priority/etc can be set by
> >   containers (either pass or reject)
> > * handle existing options (or introduce new ones) differently by
> >   propagating some information in cgroup/socket local storage
> > 
> > Compared to a simple syscall/{g,s}etsockopt tracepoint, those
> > hooks are context aware. Meaning, they can access underlying socket
> > and use cgroup and socket local storage.
> > 
> > v9:
> > * allow overwriting setsocktop arguments (Alexei Starovoitov)
> >   (see individual changes for more changelog details)
> 
> Applied. Thanks.
Great, thanks for all the reviews!

> There is a build warning though:
> test_sockopt_sk.c: In function ‘getsetsockopt’:
> test_sockopt_sk.c:115:2: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
>   if (*(__u32 *)buf != 0x55AA*2) {
>   ^~
> test_sockopt_sk.c:116:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
>    log_err("Unexpected getsockopt(SO_SNDBUF) 0x%x != 0x55AA*2",
>    ^~~~~~~
> 
> Pls fix it in the follow up.
Sure, but I can't reproduce it with gcc7 nor with clang9 :-/
Presumably, a switch to __get_unaligned_cpu32 should help,
I'll try to play with compilers a bit before sending a fix.