Subject: Re: [PATCH net-next v7 10/10] selftests: openvswitch: add psample test

From: Aaron Conole <[email-masked]>
Date: Mon, 01 Jul 2024 14:38:44 -0400

Adrian Moreno <[email-masked]> writes:

> Add a test to verify sampling packets via psample works.
>
> In order to do that, create a subcommand in ovs-dpctl.py to listen to
> on the psample multicast group and print samples.
>
> Signed-off-by: Adrian Moreno <[email-masked]>
> ---
>  .../selftests/net/openvswitch/openvswitch.sh  | 115 +++++++++++++++++-
>  .../selftests/net/openvswitch/ovs-dpctl.py    |  73 ++++++++++-
>  2 files changed, 182 insertions(+), 6 deletions(-)
>
> diff --git a/tools/testing/selftests/net/openvswitch/openvswitch.sh b/tools/testing/selftests/net/openvswitch/openvswitch.sh
> index 15bca0708717..02a366e01004 100755
> --- a/tools/testing/selftests/net/openvswitch/openvswitch.sh
> +++ b/tools/testing/selftests/net/openvswitch/openvswitch.sh
> @@ -20,7 +20,8 @@ tests="
>  	nat_related_v4				ip4-nat-related: ICMP related matches work with SNAT
>  	netlink_checks				ovsnl: validate netlink attrs and settings
>  	upcall_interfaces			ovs: test the upcall interfaces
> -	drop_reason				drop: test drop reasons are emitted"
> +	drop_reason				drop: test drop reasons are emitted
> +	psample					psample: Sampling packets with psample"
>  
>  info() {
>      [ $VERBOSE = 0 ] || echo $*
> @@ -102,12 +103,21 @@ ovs_netns_spawn_daemon() {
>  	shift
>  	netns=$1
>  	shift
> -	info "spawning cmd: $*"
> -	ip netns exec $netns $*  >> $ovs_dir/stdout  2>> $ovs_dir/stderr &
> +	if [ "$netns" == "_default" ]; then
> +		$*  >> $ovs_dir/stdout  2>> $ovs_dir/stderr &
> +	else
> +		ip netns exec $netns $*  >> $ovs_dir/stdout  2>> $ovs_dir/stderr &
> +	fi
>  	pid=$!
>  	ovs_sbx "$sbx" on_exit "kill -TERM $pid 2>/dev/null"
>  }
>  
> +ovs_spawn_daemon() {
> +	sbx=$1
> +	shift
> +	ovs_netns_spawn_daemon $sbx "_default" $*
> +}
> +
>  ovs_add_netns_and_veths () {
>  	info "Adding netns attached: sbx:$1 dp:$2 {$3, $4, $5}"
>  	ovs_sbx "$1" ip netns add "$3" || return 1
> @@ -170,6 +180,19 @@ ovs_drop_reason_count()
>  	return `echo "$perf_output" | grep "$pattern" | wc -l`
>  }
>  
> +ovs_test_flow_fails () {
> +	ERR_MSG="Flow actions may not be safe on all matching packets"
> +
> +	PRE_TEST=$(dmesg | grep -c "${ERR_MSG}")
> +	ovs_add_flow $@ &> /dev/null $@ && return 1
> +	POST_TEST=$(dmesg | grep -c "${ERR_MSG}")
> +
> +	if [ "$PRE_TEST" == "$POST_TEST" ]; then
> +		return 1
> +	fi
> +	return 0
> +}
> +
>  usage() {
>  	echo
>  	echo "$0 [OPTIONS] [TEST]..."
> @@ -184,6 +207,92 @@ usage() {
>  	exit 1
>  }
>  
> +
> +# psample test
> +# - use psample to observe packets
> +test_psample() {
> +	sbx_add "test_psample" || return $?
> +
> +	# Add a datapath with per-vport dispatching.
> +	ovs_add_dp "test_psample" psample -V 2:1 || return 1
> +
> +	info "create namespaces"
> +	ovs_add_netns_and_veths "test_psample" "psample" \
> +		client c0 c1 172.31.110.10/24 -u || return 1
> +	ovs_add_netns_and_veths "test_psample" "psample" \
> +		server s0 s1 172.31.110.20/24 -u || return 1
> +
> +	# Check if psample actions can be configured.
> +	ovs_add_flow "test_psample" psample \
> +	'in_port(1),eth(),eth_type(0x0806),arp()' 'psample(group=1)'

Might be good to redirect this stdout/stderr line to /dev/null -
otherwise on an unsupported system there will be the following extra
splat:

  Traceback (most recent call last):
    File "/home/aconole/git/linux/tools/testing/selftests/net/openvswitch/ovs-dpctl.py", line 2774, in <module>
      sys.exit(main(sys.argv))
   ...
    File "/usr/lib/python3.12/site-packages/pyroute2/netlink/nlsocket.py", line 489, in get
      raise msg['header']['error']
  pyroute2.netlink.exceptions.NetlinkError: (22, 'Invalid argument')

> +	if [ $? == 1 ]; then
> +		info "no support for psample - skipping"
> +		ovs_exit_sig
> +		return $ksft_skip
> +	fi
> +
> +	ovs_del_flows "test_psample" psample
> +
> +	# Test action verification.
> +	OLDIFS=$IFS
> +	IFS='*'
> +	min_key='in_port(1),eth(),eth_type(0x0800),ipv4()'
> +	for testcase in \
> +		"cookie to large"*"psample(group=1,cookie=1615141312111009080706050403020100)" \
> +		"no group with cookie"*"psample(cookie=abcd)" \
> +		"no group"*"psample()";
> +	do
> +		set -- $testcase;
> +		ovs_test_flow_fails "test_psample" psample $min_key $2
> +		if [ $? == 1 ]; then
> +			info "failed - $1"
> +			return 1
> +		fi
> +	done
> +	IFS=$OLDIFS
> +
> +	ovs_del_flows "test_psample" psample
> +	# Allow ARP
> +	ovs_add_flow "test_psample" psample \
> +		'in_port(1),eth(),eth_type(0x0806),arp()' '2' || return 1
> +	ovs_add_flow "test_psample" psample \
> +		'in_port(2),eth(),eth_type(0x0806),arp()' '1' || return 1
> +
> +	# Sample first 14 bytes of all traffic.
> +	ovs_add_flow "test_psample" psample \
> +	    "in_port(1),eth(),eth_type(0x0800),ipv4()" \
> +            "trunc(14),psample(group=1,cookie=c0ffee),2"
> +
> +	# Sample all traffic. In this case, use a sample() action with both
> +	# psample and an upcall emulating simultaneous local sampling and
> +	# sFlow / IPFIX.
> +	nlpid=$(grep -E "listening on upcall packet handler" \
> +            $ovs_dir/s0.out | cut -d ":" -f 2 | tr -d ' ')
> +
> +	ovs_add_flow "test_psample" psample \
> +            "in_port(2),eth(),eth_type(0x0800),ipv4()" \
> +            "sample(sample=100%,actions(psample(group=2,cookie=eeff0c),userspace(pid=${nlpid},userdata=eeff0c))),1"
> +
> +	# Record psample data.
> +	ovs_spawn_daemon "test_psample" python3 $ovs_base/ovs-dpctl.py psample-events
> +
> +	# Send a single ping.
> +	sleep 1
> +	ovs_sbx "test_psample" ip netns exec client ping -I c1 172.31.110.20 -c 1 || return 1
> +	sleep 1
> +
> +	# We should have received one userspace action upcall and 2 psample packets.
> +	grep -E "userspace action command" $ovs_dir/s0.out >/dev/null 2>&1 || return 1

I wonder if it would be better to check a few times instead of the one
shot sleep.  There are some constrained environments that may run this
test, and if you're worried about some kinds of races, maybe it makes
sense to check a few times?

Outside of that:

Reviewed-by: Aaron Conole <[email-masked]>

> +
> +	# client -> server samples should only contain the first 14 bytes of the packet.
> +	grep -E "rate:4294967295,group:1,cookie:c0ffee data:[0-9a-f]{28}$" \
> +			 $ovs_dir/stdout >/dev/null 2>&1 || return 1
> +	grep -E "rate:4294967295,group:2,cookie:eeff0c" \
> +			 $ovs_dir/stdout >/dev/null 2>&1 || return 1
> +
> +	return 0
> +}
> +
>  # drop_reason test
>  # - drop packets and verify the right drop reason is reported
>  test_drop_reason() {
> diff --git a/tools/testing/selftests/net/openvswitch/ovs-dpctl.py b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
> index e8dc9af10d4d..1e15b0818074 100644
> --- a/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
> +++ b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
> @@ -28,8 +28,10 @@ try:
>      from pyroute2.netlink import genlmsg
>      from pyroute2.netlink import nla
>      from pyroute2.netlink import nlmsg_atoms
> +    from pyroute2.netlink.event import EventSocket
>      from pyroute2.netlink.exceptions import NetlinkError
>      from pyroute2.netlink.generic import GenericNetlinkSocket
> +    from pyroute2.netlink.nlsocket import Marshal
>      import pyroute2
>      import pyroute2.iproute
>  
> @@ -2460,10 +2462,70 @@ class OvsFlow(GenericNetlinkSocket):
>          print("MISS upcall[%d/%s]: %s" % (seq, pktpres, keystr), flush=True)
>  
>      def execute(self, packetmsg):
> -        print("userspace execute command")
> +        print("userspace execute command", flush=True)
>  
>      def action(self, packetmsg):
> -        print("userspace action command")
> +        print("userspace action command", flush=True)
> +
> +
> +class psample_sample(genlmsg):
> +    nla_map = (
> +        ("PSAMPLE_ATTR_IIFINDEX", "none"),
> +        ("PSAMPLE_ATTR_OIFINDEX", "none"),
> +        ("PSAMPLE_ATTR_ORIGSIZE", "none"),
> +        ("PSAMPLE_ATTR_SAMPLE_GROUP", "uint32"),
> +        ("PSAMPLE_ATTR_GROUP_SEQ", "none"),
> +        ("PSAMPLE_ATTR_SAMPLE_RATE", "uint32"),
> +        ("PSAMPLE_ATTR_DATA", "array(uint8)"),
> +        ("PSAMPLE_ATTR_GROUP_REFCOUNT", "none"),
> +        ("PSAMPLE_ATTR_TUNNEL", "none"),
> +        ("PSAMPLE_ATTR_PAD", "none"),
> +        ("PSAMPLE_ATTR_OUT_TC", "none"),
> +        ("PSAMPLE_ATTR_OUT_TC_OCC", "none"),
> +        ("PSAMPLE_ATTR_LATENCY", "none"),
> +        ("PSAMPLE_ATTR_TIMESTAMP", "none"),
> +        ("PSAMPLE_ATTR_PROTO", "none"),
> +        ("PSAMPLE_ATTR_USER_COOKIE", "array(uint8)"),
> +    )
> +
> +    def dpstr(self):
> +        fields = []
> +        data = ""
> +        for (attr, value) in self["attrs"]:
> +            if attr == "PSAMPLE_ATTR_SAMPLE_GROUP":
> +                fields.append("group:%d" % value)
> +            if attr == "PSAMPLE_ATTR_SAMPLE_RATE":
> +                fields.append("rate:%d" % value)
> +            if attr == "PSAMPLE_ATTR_USER_COOKIE":
> +                value = "".join(format(x, "02x") for x in value)
> +                fields.append("cookie:%s" % value)
> +            if attr == "PSAMPLE_ATTR_DATA" and len(value) > 0:
> +                data = "data:%s" % "".join(format(x, "02x") for x in value)
> +
> +        return ("%s %s" % (",".join(fields), data)).strip()
> +
> +
> +class psample_msg(Marshal):
> +    PSAMPLE_CMD_SAMPLE = 0
> +    PSAMPLE_CMD_GET_GROUP = 1
> +    PSAMPLE_CMD_NEW_GROUP = 2
> +    PSAMPLE_CMD_DEL_GROUP = 3
> +    PSAMPLE_CMD_SET_FILTER = 4
> +    msg_map = {PSAMPLE_CMD_SAMPLE: psample_sample}
> +
> +
> +class PsampleEvent(EventSocket):
> +    genl_family = "psample"
> +    mcast_groups = ["packets"]
> +    marshal_class = psample_msg
> +
> +    def read_samples(self):
> +        while True:
> +            try:
> +                for msg in self.get():
> +                    print(msg.dpstr(), flush=True)
> +            except NetlinkError as ne:
> +                raise ne
>  
>  
>  def print_ovsdp_full(dp_lookup_rep, ifindex, ndb=NDB(), vpl=OvsVport()):
> @@ -2530,7 +2592,7 @@ def main(argv):
>          help="Increment 'verbose' output counter.",
>          default=0,
>      )
> -    subparsers = parser.add_subparsers()
> +    subparsers = parser.add_subparsers(dest="subcommand")
>  
>      showdpcmd = subparsers.add_parser("show")
>      showdpcmd.add_argument(
> @@ -2605,6 +2667,8 @@ def main(argv):
>      delfscmd = subparsers.add_parser("del-flows")
>      delfscmd.add_argument("flsbr", help="Datapath name")
>  
> +    subparsers.add_parser("psample-events")
> +
>      args = parser.parse_args()
>  
>      if args.verbose > 0:
> @@ -2619,6 +2683,9 @@ def main(argv):
>  
>      sys.setrecursionlimit(100000)
>  
> +    if args.subcommand == "psample-events":
> +        PsampleEvent().read_samples()
> +
>      if hasattr(args, "showdp"):
>          found = False
>          for iface in ndb.interfaces: