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Wed, 11 Feb 2026 17:01:51 -0800 (PST) From: Bobby Eshleman Date: Wed, 11 Feb 2026 17:00:44 -0800 Subject: [PATCH net 4/4] selftests: drv-net: add HDS payload sweep test for devmem TCP 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: quoted-printable Message-Id: <20260211-fbnic-tcp-hds-fixes-v1-4-55d050e6f606@meta.com> References: <20260211-fbnic-tcp-hds-fixes-v1-0-55d050e6f606@meta.com> In-Reply-To: <20260211-fbnic-tcp-hds-fixes-v1-0-55d050e6f606@meta.com> To: Alexander Duyck , Jakub Kicinski , kernel-team@meta.com, Andrew Lunn , "David S. Miller" , Eric Dumazet , Paolo Abeni , Mohsin Bashir , Shuah Khan Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Bobby Eshleman X-Mailer: b4 0.14.3 From: Bobby Eshleman Add check_rx_hds test that verifies header/data split works across payload sizes. The test sweeps payload sizes from 1 byte to 8KB, if any data propagates up to userspace as SCM_DEVMEM_LINEAR, then the test fails. This shows that regardless of payload size, ncdevmem's configuration of hds-thresh to 0 is respected. Add -L (--fail-on-linear) flag to ncdevmem that causes the receiver to fail if any SCM_DEVMEM_LINEAR cmsg is received. Use socat option for fixed block sizing and tcp nodelay to disable nagle's algo to avoid buffering. Signed-off-by: Bobby Eshleman --- tools/testing/selftests/drivers/net/hw/devmem.py | 19 ++++++++++++++++++- tools/testing/selftests/drivers/net/hw/ncdevmem.c | 11 ++++++++++- 2 files changed, 28 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/drivers/net/hw/devmem.py b/tools/testi= ng/selftests/drivers/net/hw/devmem.py index 45c2d49d55b6..ee863e90d1e0 100755 --- a/tools/testing/selftests/drivers/net/hw/devmem.py +++ b/tools/testing/selftests/drivers/net/hw/devmem.py @@ -63,12 +63,29 @@ def check_tx_chunks(cfg) -> None: ksft_eq(socat.stdout.strip(), "hello\nworld") =20 =20 +def check_rx_hds(cfg) -> None: + """Test HDS splitting across payload sizes.""" + require_devmem(cfg) + + for size in [1, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192]: + port =3D rand_port() + listen_cmd =3D f"{cfg.bin_local} -L -l -f {cfg.ifname} -s {cfg.add= r} -p {port}" + + with bkg(listen_cmd, exit_wait=3DTrue) as ncdevmem: + wait_port_listen(port) + cmd(f"dd if=3D/dev/zero bs=3D{size} count=3D1 2>/dev/null | " + + f"socat -b {size} -u - TCP{cfg.addr_ipver}:{cfg.baddr}:{po= rt},nodelay", + host=3Dcfg.remote, shell=3DTrue) + + ksft_eq(ncdevmem.ret, 0, f"HDS failed for payload size {size}") + + def main() -> None: with NetDrvEpEnv(__file__) as cfg: cfg.bin_local =3D path.abspath(path.dirname(__file__) + "/ncdevmem= ") cfg.bin_remote =3D cfg.remote.deploy(cfg.bin_local) =20 - ksft_run([check_rx, check_tx, check_tx_chunks], + ksft_run([check_rx, check_tx, check_tx_chunks, check_rx_hds], args=3D(cfg, )) ksft_exit() =20 diff --git a/tools/testing/selftests/drivers/net/hw/ncdevmem.c b/tools/test= ing/selftests/drivers/net/hw/ncdevmem.c index 3288ed04ce08..adc89591c834 100644 --- a/tools/testing/selftests/drivers/net/hw/ncdevmem.c +++ b/tools/testing/selftests/drivers/net/hw/ncdevmem.c @@ -97,6 +97,7 @@ static unsigned int ifindex; static unsigned int dmabuf_id; static uint32_t tx_dmabuf_id; static int waittime_ms =3D 500; +static bool fail_on_linear; =20 /* System state loaded by current_config_load() */ #define MAX_FLOWS 8 @@ -974,6 +975,11 @@ static int do_server(struct memory_buffer *mem) "SCM_DEVMEM_LINEAR. dmabuf_cmsg->frag_size=3D%u\n", dmabuf_cmsg->frag_size); =20 + if (fail_on_linear) { + pr_err("received SCM_DEVMEM_LINEAR but --fail-on-linear (-L) set"); + goto err_close_client; + } + continue; } =20 @@ -1397,8 +1403,11 @@ int main(int argc, char *argv[]) int is_server =3D 0, opt; int ret, err =3D 1; =20 - while ((opt =3D getopt(argc, argv, "ls:c:p:v:q:t:f:z:")) !=3D -1) { + while ((opt =3D getopt(argc, argv, "Lls:c:p:v:q:t:f:z:")) !=3D -1) { switch (opt) { + case 'L': + fail_on_linear =3D true; + break; case 'l': is_server =3D 1; break; --=20 2.47.3