Subject: Re: [net-next v3 7/7] selftests: openvswitch: add explicit drop testcase

From: Aaron Conole <[email-masked]>
Date: Wed, 09 Aug 2023 11:18:32 -0400

Adrian Moreno <[email-masked]> writes:

> On 8/8/23 17:02, Aaron Conole wrote:
>> Adrian Moreno <[email-masked]> writes:
>> 
>>> Make ovs-dpctl.py support explicit drops as:
>>> "drop" -> implicit empty-action drop
>>> "drop(0)" -> explicit non-error action drop
>> I also suggest a test in netlink_checks to make sure drop can't be
>> followed by additional actions.  Something like:
>>    3,drop(0),2
>> which should generate a NL message that has the drop attribute with
>> additional action data following it.
>
> Ack, will do.
>
> The check I've added in flow_netlink.c does not include any custom
> message. Just returning -EINVAL in __ovs_nla_copy_actions() ends up
> printing "Flow actions may not be safe on all matching packets" to
> dmesg. Maybe it's too generic or even misleading in some cases but I
> saw other action verifications do the same so I thought it might be
> kind of expected at this point.
>
> Do you think a custom message (in addition to the generic one) is needed?

I think the message is fine.  There could be a bigger effort at some
point to try and do per-attribute rejection messages.

> Thanks.
> --
> Adrián
>
>> 
>>> "drop(42)" -> explicit error action drop
>>>
>>> Signed-off-by: Adrian Moreno <[email-masked]>
>>> ---
>>>   .../selftests/net/openvswitch/openvswitch.sh  | 25 +++++++++++++++++++
>>>   .../selftests/net/openvswitch/ovs-dpctl.py    | 21 ++++++++++++----
>>>   2 files changed, 41 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/tools/testing/selftests/net/openvswitch/openvswitch.sh b/tools/testing/selftests/net/openvswitch/openvswitch.sh
>>> index a10c345f40ef..c568ba1b7900 100755
>>> --- a/tools/testing/selftests/net/openvswitch/openvswitch.sh
>>> +++ b/tools/testing/selftests/net/openvswitch/openvswitch.sh
>>> @@ -217,6 +217,31 @@ test_drop_reason() {
>>>   		return 1
>>>   	fi
>>>   +	# Drop UDP 6000 traffic with an explicit action and an error
>>> code.
>>> +	ovs_add_flow "test_drop_reason" dropreason \
>>> +		"in_port(1),eth(),eth_type(0x0800),ipv4(src=172.31.110.10,proto=17),udp(dst=6000)" \
>>> +                'drop(42)'
>>> +	# Drop UDP 7000 traffic with an explicit action with no error code.
>>> +	ovs_add_flow "test_drop_reason" dropreason \
>>> +		"in_port(1),eth(),eth_type(0x0800),ipv4(src=172.31.110.10,proto=17),udp(dst=7000)" \
>>> +                'drop(0)'
>>> +
>>> +	ovs_drop_record_and_run \
>>> +            "test_drop_reason" ip netns exec client nc -i 1 -zuv 172.31.110.20 6000
>>> +	ovs_drop_reason_count 0x30004 # OVS_DROP_EXPLICIT_ACTION_ERROR
>>> +	if [[ "$?" -ne "1" ]]; then
>>> +		info "Did not detect expected explicit error drops: $?"
>>> +		return 1
>>> +	fi
>>> +
>>> +	ovs_drop_record_and_run \
>>> +            "test_drop_reason" ip netns exec client nc -i 1 -zuv 172.31.110.20 7000
>>> +	ovs_drop_reason_count 0x30003 # OVS_DROP_EXPLICIT_ACTION
>>> +	if [[ "$?" -ne "1" ]]; then
>>> +		info "Did not detect expected explicit drops: $?"
>>> +		return 1
>>> +	fi
>>> +
>>>   	return 0
>>>   }
>>>   diff --git a/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
>>> b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
>>> index 5fee330050c2..912dc8c49085 100644
>>> --- a/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
>>> +++ b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
>>> @@ -449,7 +449,7 @@ class ovsactions(nla):
>>>                   elif field[0] == "OVS_ACTION_ATTR_TRUNC":
>>>                       print_str += "trunc(%d)" % int(self.get_attr(field[0]))
>>>                   elif field[0] == "OVS_ACTION_ATTR_DROP":
>>> -                    print_str += "drop"
>>> +                    print_str += "drop(%d)" % int(self.get_attr(field[0]))
>>>               elif field[1] == "flag":
>>>                   if field[0] == "OVS_ACTION_ATTR_CT_CLEAR":
>>>                       print_str += "ct_clear"
>>> @@ -471,10 +471,21 @@ class ovsactions(nla):
>>>           while len(actstr) != 0:
>>>               parsed = False
>>>               if actstr.startswith("drop"):
>>> -                # for now, drops have no explicit action, so we
>>> -                # don't need to set any attributes.  The final
>>> -                # act of the processing chain will just drop the packet
>>> -                return
>>> +                # If no reason is provided, the implicit drop is used (i.e no
>>> +                # action). If some reason is given, an explicit action is used.
>>> +                actstr, reason = parse_extract_field(
>>> +                    actstr,
>>> +                    "drop(",
>>> +                    "([0-9]+)",
>>> +                    lambda x: int(x, 0),
>>> +                    False,
>>> +                    None,
>>> +                )
>>> +                if reason is not None:
>>> +                    self["attrs"].append(["OVS_ACTION_ATTR_DROP", reason])
>>> +                    parsed = True
>>> +                else:
>>> +                    return
>>>                 elif parse_starts_block(actstr, "^(\d+)", False,
>>> True):
>>>                   actstr, output = parse_extract_field(
>>