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Wed, 15 Apr 2026 08:09:42 -0700 (PDT) Received: from lleonard-thinkpadx1carbongen13.rmtit.csb ([176.206.19.176]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43ead35bf1esm5907557f8f.16.2026.04.15.08.09.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Apr 2026 08:09:42 -0700 (PDT) From: Luigi Leonardi Date: Wed, 15 Apr 2026 17:09:29 +0200 Subject: [PATCH net v4 2/3] vsock/test: fix MSG_PEEK handling in recv_buf() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260415-fix_peek-v4-2-8207e872759e@redhat.com> References: <20260415-fix_peek-v4-0-8207e872759e@redhat.com> In-Reply-To: <20260415-fix_peek-v4-0-8207e872759e@redhat.com> To: Stefan Hajnoczi , Stefano Garzarella , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?utf-8?q?Eugenio_P=C3=A9rez?= , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Arseniy Krasnov Cc: kvm@vger.kernel.org, virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Luigi Leonardi X-Mailer: b4 0.14.3 `recv_buf` does not handle the MSG_PEEK flag correctly: it keeps calling `recv` until all requested bytes are available or an error occurs. The problem is how it calculates the number of bytes read: MSG_PEEK doesn't consume any bytes and will re-read the same bytes from the buffer head, so summing the return value every time is wrong. Moreover, MSG_PEEK doesn't consume the bytes in the buffer, so if more bytes are requested than are available, the loop will never terminate, because `recv` will never return EOF. For this reason, we need to compare the number of bytes read with the number of bytes expected. Add a check: if the MSG_PEEK flag is present, update the byte counter and break out of the loop only after at least the expected number of bytes have been received; otherwise, retry after a short delay to avoid consuming too many CPU cycles. This allows us to simplify the `test_stream_credit_update_test` by reusing `recv_buf`, like some other tests already do. Suggested-by: Stefano Garzarella Signed-off-by: Luigi Leonardi --- tools/testing/vsock/util.c | 15 +++++++++++++++ tools/testing/vsock/vsock_test.c | 13 +------------ 2 files changed, 16 insertions(+), 12 deletions(-) diff --git a/tools/testing/vsock/util.c b/tools/testing/vsock/util.c index 1fe1338c79cd..fe316b02a590 100644 --- a/tools/testing/vsock/util.c +++ b/tools/testing/vsock/util.c @@ -381,7 +381,13 @@ void send_buf(int fd, const void *buf, size_t len, int flags, } } +#define RECV_PEEK_RETRY_USEC (10 * 1000) + /* Receive bytes in a buffer and check the return value. + * + * When MSG_PEEK is set, recv() is retried until it returns at least + * expected_ret bytes. The function returns on error, EOF, or timeout + * as usual. * * expected_ret: * <0 Negative errno (for testing errors) @@ -403,6 +409,15 @@ void recv_buf(int fd, void *buf, size_t len, int flags, ssize_t expected_ret) if (ret <= 0) break; + if (flags & MSG_PEEK) { + if (ret >= expected_ret) { + nread = ret; + break; + } + timeout_usleep(RECV_PEEK_RETRY_USEC); + continue; + } + nread += ret; } while (nread < len); timeout_end(); diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c index 5bd20ccd9335..bdb0754965df 100644 --- a/tools/testing/vsock/vsock_test.c +++ b/tools/testing/vsock/vsock_test.c @@ -1500,18 +1500,7 @@ static void test_stream_credit_update_test(const struct test_opts *opts, } /* Wait until there will be 128KB of data in rx queue. */ - while (1) { - ssize_t res; - - res = recv(fd, buf, buf_size, MSG_PEEK); - if (res == buf_size) - break; - - if (res <= 0) { - fprintf(stderr, "unexpected 'recv()' return: %zi\n", res); - exit(EXIT_FAILURE); - } - } + recv_buf(fd, buf, buf_size, MSG_PEEK, buf_size); /* There is 128KB of data in the socket's rx queue, dequeue first * 64KB, credit update is sent if 'low_rx_bytes_test' == true. -- 2.53.0