selftests: drv-net: add checksum tests

Run tools/testing/selftest/net/csum.c as part of drv-net.
This binary covers multiple scenarios, based on arguments given,
for both IPv4 and IPv6:

- Accept UDP correct checksum
- Detect UDP invalid checksum
- Accept TCP correct checksum
- Detect TCP invalid checksum

- Transmit UDP: basic checksum offload
- Transmit UDP: zero checksum conversion

The test direction is reversed between receive and transmit tests, so
that the NIC under test is always the local machine.

In total this adds up to 12 testcases, with more to follow. For
conciseness, I replaced individual functions with a function factory.

Also detect hardware offload feature availability using Ethtool
netlink and skip tests when either feature is off. This need may be
common for offload feature tests and eventually deserving of a thin
wrapper in lib.py.

Missing are the PF_PACKET based send tests ('-P'). These use
virtio_net_hdr to program hardware checksum offload. Which requires
looking up the local MAC address and (harder) the MAC of the next hop.
I'll have to give it some though how to do that robustly and where
that code would belong.

Tested:

        make -C tools/testing/selftests/ \
                TARGETS="drivers/net drivers/net/hw" \
                install INSTALL_PATH=/tmp/ksft
        cd /tmp/ksft

	sudo NETIF=ens4 REMOTE_TYPE=ssh \
		REMOTE_ARGS="root@10.40.0.2" \
		LOCAL_V4="10.40.0.1" \
		REMOTE_V4="10.40.0.2" \
		./run_kselftest.sh -t drivers/net/hw:csum.py

Signed-off-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240507154216.501111-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/drivers/net/hw/Makefile

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0+ OR MIT
 
 TEST_PROGS = \
+	csum.py \
 	devlink_port_split.py \
 	ethtool.sh \
 	ethtool_extended_state.sh \

tools/testing/selftests/drivers/net/hw/csum.py

@@ -0,0 +1,122 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""Run the tools/testing/selftests/net/csum testsuite."""
+
+from os import path
+
+from lib.py import ksft_run, ksft_exit, KsftSkipEx
+from lib.py import EthtoolFamily, NetDrvEpEnv
+from lib.py import bkg, cmd, wait_port_listen
+
+def test_receive(cfg, ipv4=False, extra_args=None):
+    """Test local nic checksum receive. Remote host sends crafted packets."""
+    if not cfg.have_rx_csum:
+        raise KsftSkipEx(f"Test requires rx checksum offload on {cfg.ifname}")
+
+    if ipv4:
+        ip_args = f"-4 -S {cfg.remote_v4} -D {cfg.v4}"
+    else:
+        ip_args = f"-6 -S {cfg.remote_v6} -D {cfg.v6}"
+
+    rx_cmd = f"{cfg.bin_local} -i {cfg.ifname} -n 100 {ip_args} -r 1 -R {extra_args}"
+    tx_cmd = f"{cfg.bin_remote} -i {cfg.ifname} -n 100 {ip_args} -r 1 -T {extra_args}"
+
+    with bkg(rx_cmd, exit_wait=True):
+        wait_port_listen(34000, proto="udp")
+        cmd(tx_cmd, host=cfg.remote)
+
+
+def test_transmit(cfg, ipv4=False, extra_args=None):
+    """Test local nic checksum transmit. Remote host verifies packets."""
+    if (not cfg.have_tx_csum_generic and
+        not (cfg.have_tx_csum_ipv4 and ipv4) and
+        not (cfg.have_tx_csum_ipv6 and not ipv4)):
+        raise KsftSkipEx(f"Test requires tx checksum offload on {cfg.ifname}")
+
+    if ipv4:
+        ip_args = f"-4 -S {cfg.v4} -D {cfg.remote_v4}"
+    else:
+        ip_args = f"-6 -S {cfg.v6} -D {cfg.remote_v6}"
+
+    # Cannot randomize input when calculating zero checksum
+    if extra_args != "-U -Z":
+        extra_args += " -r 1"
+
+    rx_cmd = f"{cfg.bin_remote} -i {cfg.ifname} -L 1 -n 100 {ip_args} -R {extra_args}"
+    tx_cmd = f"{cfg.bin_local} -i {cfg.ifname} -L 1 -n 100 {ip_args} -T {extra_args}"
+
+    with bkg(rx_cmd, host=cfg.remote, exit_wait=True):
+        wait_port_listen(34000, proto="udp", host=cfg.remote)
+        cmd(tx_cmd)
+
+
+def test_builder(name, cfg, ipv4=False, tx=False, extra_args=""):
+    """Construct specific tests from the common template.
+
+       Most tests follow the same basic pattern, differing only in
+       Direction of the test and optional flags passed to csum."""
+    def f(cfg):
+        if ipv4:
+            cfg.require_v4()
+        else:
+            cfg.require_v6()
+
+        if tx:
+            test_transmit(cfg, ipv4, extra_args)
+        else:
+            test_receive(cfg, ipv4, extra_args)
+
+    if ipv4:
+        f.__name__ = "ipv4_" + name
+    else:
+        f.__name__ = "ipv6_" + name
+    return f
+
+
+def check_nic_features(cfg) -> None:
+    """Test whether Tx and Rx checksum offload are enabled.
+
+       If the device under test has either off, then skip the relevant tests."""
+    cfg.have_tx_csum_generic = False
+    cfg.have_tx_csum_ipv4 = False
+    cfg.have_tx_csum_ipv6 = False
+    cfg.have_rx_csum = False
+
+    ethnl = EthtoolFamily()
+    features = ethnl.features_get({"header": {"dev-index": cfg.ifindex}})
+    for f in features["active"]["bits"]["bit"]:
+        if f["name"] == "tx-checksum-ip-generic":
+            cfg.have_tx_csum_generic = True
+        elif f["name"] == "tx-checksum-ipv4":
+            cfg.have_tx_csum_ipv4 = True
+        elif f["name"] == "tx-checksum-ipv6":
+            cfg.have_tx_csum_ipv6 = True
+        elif f["name"] == "rx-checksum":
+            cfg.have_rx_csum = True
+
+
+def main() -> None:
+    with NetDrvEpEnv(__file__, nsim_test=False) as cfg:
+        check_nic_features(cfg)
+
+        cfg.bin_local = path.abspath(path.dirname(__file__) + "/../../../net/lib/csum")
+        cfg.bin_remote = cfg.remote.deploy(cfg.bin_local)
+
+        cases = []
+        for ipv4 in [True, False]:
+            cases.append(test_builder("rx_tcp", cfg, ipv4, False, "-t"))
+            cases.append(test_builder("rx_tcp_invalid", cfg, ipv4, False, "-t -E"))
+
+            cases.append(test_builder("rx_udp", cfg, ipv4, False, ""))
+            cases.append(test_builder("rx_udp_invalid", cfg, ipv4, False, "-E"))
+
+            cases.append(test_builder("tx_udp_csum_offload", cfg, ipv4, True, "-U"))
+            cases.append(test_builder("tx_udp_zero_checksum", cfg, ipv4, True, "-U -Z"))
+
+        ksft_run(cases=cases, args=(cfg, ))
+    ksft_exit()
+
+
+if __name__ == "__main__":
+    main()

tools/testing/selftests/net/.gitignore

@@ -2,7 +2,6 @@
 bind_bhash
 bind_timewait
 bind_wildcard
-csum
 cmsg_sender
 diag_uid
 fin_ack_lat

tools/testing/selftests/net/Makefile

@@ -81,7 +81,6 @@ TEST_PROGS += test_ingress_egress_chaining.sh
 TEST_GEN_PROGS += so_incoming_cpu
 TEST_PROGS += sctp_vrf.sh
 TEST_GEN_FILES += sctp_hello
-TEST_GEN_FILES += csum
 TEST_GEN_FILES += ip_local_port_range
 TEST_GEN_FILES += bind_wildcard
 TEST_PROGS += test_vxlan_mdb.sh

tools/testing/selftests/net/lib/.gitignore

@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+csum

tools/testing/selftests/net/lib/Makefile

@@ -1,8 +1,15 @@
 # SPDX-License-Identifier: GPL-2.0
 
+CFLAGS =  -Wall -Wl,--no-as-needed -O2 -g
+CFLAGS += -I../../../../../usr/include/ $(KHDR_INCLUDES)
+# Additional include paths needed by kselftest.h
+CFLAGS += -I../../
+
 TEST_FILES := ../../../../../Documentation/netlink/specs
 TEST_FILES += ../../../../net/ynl
 
+TEST_GEN_FILES += csum
+
 TEST_INCLUDES := $(wildcard py/*.py)
 
 include ../../lib.mk