Re: [PATCH net-next 3/3] selftests: drv-net: add a simple TSO test

Willem de Bruijn
2025-02-13T16:02:54Z

Stanislav Fomichev wrote:
> On 02/12, Jakub Kicinski wrote:
> > Add a simple test for TSO. Send a few MB of data and check device
> > stats to verify that the device was performing segmentation.
> > Do the same thing over a few tunnel types.
> >
> > Injecting GSO packets directly would give us more ability to test
> > corner cases, but perhaps starting simple is good enough?
> >
> > # ./ksft-net-drv/drivers/net/hw/tso.py
> > # Detected qstat for LSO wire-packets
> > KTAP version 1
> > 1..14
> > ok 1 tso.ipv4 # SKIP Test requires IPv4 connectivity
> > ok 2 tso.vxlan4_ipv4 # SKIP Test requires IPv4 connectivity
> > ok 3 tso.vxlan6_ipv4 # SKIP Test requires IPv4 connectivity
> > ok 4 tso.vxlan_csum4_ipv4 # SKIP Test requires IPv4 connectivity
> > ok 5 tso.vxlan_csum6_ipv4 # SKIP Test requires IPv4 connectivity
> > ok 6 tso.gre4_ipv4 # SKIP Test requires IPv4 connectivity
> > ok 7 tso.gre6_ipv4 # SKIP Test requires IPv4 connectivity
> > ok 8 tso.ipv6
> > ok 9 tso.vxlan4_ipv6
> > ok 10 tso.vxlan6_ipv6
> > ok 11 tso.vxlan_csum4_ipv6
> > ok 12 tso.vxlan_csum6_ipv6
> > ok 13 tso.gre4_ipv6
> > ok 14 tso.gre6_ipv6
> > # Totals: pass:7 fail:0 xfail:0 xpass:0 skip:7 error:0
> >
> > Note that the test currently depends on the driver reporting
> > the LSO count via qstat, which appears to be relatively rare
> > (virtio, cisco/enic, sfc/efc; but virtio needs host support).
> >
> > Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> > ---
> > .../testing/selftests/drivers/net/hw/Makefile | 1 +
> > tools/testing/selftests/drivers/net/hw/tso.py | 226 ++++++++++++++++++
> > 2 files changed, 227 insertions(+)
> > create mode 100755 tools/testing/selftests/drivers/net/hw/tso.py
> >
> > diff --git a/tools/testing/selftests/drivers/net/hw/Makefile b/tools/testing/selftests/drivers/net/hw/Makefile
> > index 21ba64ce1e34..ae783e18be83 100644
> > --- a/tools/testing/selftests/drivers/net/hw/Makefile
> > +++ b/tools/testing/selftests/drivers/net/hw/Makefile
> > @@ -15,6 +15,7 @@ TEST_PROGS = \
> > nic_performance.py \
> > pp_alloc_fail.py \
> > rss_ctx.py \
> > + tso.py \
> > #
> >
> > TEST_FILES := \
> > diff --git a/tools/testing/selftests/drivers/net/hw/tso.py b/tools/testing/selftests/drivers/net/hw/tso.py
> > new file mode 100755
> > index 000000000000..ee3e207d85b3
> > --- /dev/null
> > +++ b/tools/testing/selftests/drivers/net/hw/tso.py
> > @@ -0,0 +1,226 @@
> > +#!/usr/bin/env python3
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +"""Run the tools/testing/selftests/net/csum testsuite."""
> > +
> > +import fcntl
> > +import socket
> > +import struct
> > +import termios
> > +import time
> > +
> > +from lib.py import ksft_pr, ksft_run, ksft_exit, KsftSkipEx, KsftXfailEx
> > +from lib.py import ksft_eq, ksft_ge, ksft_lt
> > +from lib.py import EthtoolFamily, NetdevFamily, NetDrvEpEnv
> > +from lib.py import bkg, cmd, defer, ethtool, ip, rand_port, wait_port_listen
> > +
> > +
> > +def sock_wait_drain(sock, max_wait=1000):
> > + """Wait for all pending write data on the socket to get ACKed."""
> > + for _ in range(max_wait):
> > + one = b'\0' * 4
> > + outq = fcntl.ioctl(sock.fileno(), termios.TIOCOUTQ, one)
> > + outq = struct.unpack("I", outq)[0]
> > + if outq == 0:
> > + break
> > + time.sleep(0.01)
> > + ksft_eq(outq, 0)
> > +
> > +
> > +def tcp_sock_get_retrans(sock):
> > + """Get the number of retransmissions for the TCP socket."""
> > + info = sock.getsockopt(socket.SOL_TCP, socket.TCP_INFO, 512)
> > + return struct.unpack("I", info[100:104])[0]
> > +
> > +
> > +def run_one_stream(cfg, ipv4, remote_v4, remote_v6, should_lso):
> > + cfg.require_cmd("socat", remote=True)
> > +
> > + port = rand_port()
> > + listen_cmd = f"socat -{cfg.addr_ipver} -t 2 -u TCP-LISTEN:{port},reuseport /dev/null,ignoreeof"
> > +
> > + with bkg(listen_cmd, host=cfg.remote) as nc:
> > + wait_port_listen(port, host=cfg.remote)
> > +
> > + if ipv4:
> > + sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
> > + sock.connect((remote_v4, port))
> > + else:
> > + sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
> > + sock.connect((remote_v6, port))
> > +
> > + # Small send to make sure the connection is working.
> > + sock.send("ping".encode())
> > + sock_wait_drain(sock)
> > +
> > + # Send 4MB of data, record the LSO packet count.
> > + qstat_old = cfg.netnl.qstats_get({"ifindex": cfg.ifindex}, dump=True)[0]
> > + buf = b"0" * 1024 * 1024 * 4
> > + sock.send(buf)
> > + sock_wait_drain(sock)
> > + qstat_new = cfg.netnl.qstats_get({"ifindex": cfg.ifindex}, dump=True)[0]
> > +
> > + # No math behind the 10 here, but try to catch cases where
> > + # TCP falls back to non-LSO.
> > + ksft_lt(tcp_sock_get_retrans(sock), 10)
> > + sock.close()
> > +
> > + # Check that at least 90% of the data was sent as LSO packets.
> > + # System noise may cause false negatives, it is what it is.
> > + total_lso_wire = len(buf) * 0.90 // cfg.dev["mtu"]
> > + total_lso_super = len(buf) * 0.90 // cfg.dev["tso_max_size"]

Besides noise this also includes the payload to wire length with headers
fudge factor, right?

> > + if should_lso:
> > + if cfg.have_stat_super_count:
> > + ksft_ge(qstat_new['tx-hw-gso-packets'] -
> > + qstat_old['tx-hw-gso-packets'],
> > + total_lso_super,
> > + comment="Number of LSO super-packets with LSO enabled")
> > + if cfg.have_stat_wire_count:
> > + ksft_ge(qstat_new['tx-hw-gso-wire-packets'] -
> > + qstat_old['tx-hw-gso-wire-packets'],
> > + total_lso_wire,
> > + comment="Number of LSO wire-packets with LSO enabled")