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Tue, 09 Sep 2025 02:51:14 -0700 (PDT) From: Jakub Sitnicki To: Michal Luczaj Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Mykola Lysenko , Shuah Khan , bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next 1/5] selftests/bpf: sockmap_redir: Simplify try_recv() In-Reply-To: <20250905-redir-test-pass-drop-v1-1-9d9e43ff40df@rbox.co> (Michal Luczaj's message of "Fri, 05 Sep 2025 13:11:41 +0200") References: <20250905-redir-test-pass-drop-v1-0-9d9e43ff40df@rbox.co> <20250905-redir-test-pass-drop-v1-1-9d9e43ff40df@rbox.co> Date: Tue, 09 Sep 2025 11:51:13 +0200 Message-ID: <87ikhs54z2.fsf@cloudflare.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Fri, Sep 05, 2025 at 01:11 PM +02, Michal Luczaj wrote: > try_recv() was meant to support both @expect_success cases, but all the > callers use @expect_success=false anyway. Drop the unused logic and fold in > MSG_DONTWAIT. Adapt callers. > > Subtle change here: recv() return value of 0 will also be considered (an > unexpected) success. > > Signed-off-by: Michal Luczaj > --- > .../selftests/bpf/prog_tests/sockmap_redir.c | 25 +++++++++------------- > 1 file changed, 10 insertions(+), 15 deletions(-) > > diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_redir.c b/tools/testing/selftests/bpf/prog_tests/sockmap_redir.c > index 9c461d93113db20de65ac353f92dfdbe32ffbd3b..c1bf1076e8152b7d83c3e07e2dce746b5a39cf7e 100644 > --- a/tools/testing/selftests/bpf/prog_tests/sockmap_redir.c > +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_redir.c > @@ -144,17 +144,14 @@ static void get_redir_params(struct redir_spec *redir, > *redirect_flags = 0; > } > > -static void try_recv(const char *prefix, int fd, int flags, bool expect_success) > +static void fail_recv(const char *prefix, int fd, int more_flags) > { > ssize_t n; > char buf; > > - errno = 0; > - n = recv(fd, &buf, 1, flags); > - if (n < 0 && expect_success) > - FAIL_ERRNO("%s: unexpected failure: retval=%zd", prefix, n); > - if (!n && !expect_success) > - FAIL("%s: expected failure: retval=%zd", prefix, n); > + n = recv(fd, &buf, 1, MSG_DONTWAIT | more_flags); > + if (n >= 0) > + FAIL("%s: unexpected success: retval=%zd", prefix, n); > } This bit, which you highlighted in the description, I don't get. If we're expecting to receive exactly one byte, why treat a short read as a succcess? Why not make it a strict "n != 1" check? [...]