Subject: Re: [PATCH v2 net-next 5/5] selftests: openvswitch: add ct-nat test case with ipv4

From: Aaron Conole <[email-masked]>
Date: Mon, 31 Jul 2023 14:53:31 -0400

Adrian Moreno <[email-masked]> writes:

> On 7/28/23 13:59, Aaron Conole wrote:
>> Building on the previous work, add a very simplistic NAT case
>> using ipv4.  This just tests dnat transformation
>> Signed-off-by: Aaron Conole <[email-masked]>
>> ---
>>   .../selftests/net/openvswitch/openvswitch.sh  | 64 ++++++++++++++++
>>   .../selftests/net/openvswitch/ovs-dpctl.py    | 75 +++++++++++++++++++
>>   2 files changed, 139 insertions(+)
>> diff --git a/tools/testing/selftests/net/openvswitch/openvswitch.sh
>> b/tools/testing/selftests/net/openvswitch/openvswitch.sh
>> index 40a66c72af0f..dced4f612a78 100755
>> --- a/tools/testing/selftests/net/openvswitch/openvswitch.sh
>> +++ b/tools/testing/selftests/net/openvswitch/openvswitch.sh
>> @@ -14,6 +14,7 @@ tests="
>>   	arp_ping				eth-arp: Basic arp ping between two NS
>>   	ct_connect_v4				ip4-ct-xon: Basic ipv4 tcp connection using ct
>>   	connect_v4				ip4-xon: Basic ipv4 ping between two NS
>> +	nat_connect_v4				ip4-nat-xon: Basic ipv4 tcp connection via NAT
>>   	netlink_checks				ovsnl: validate netlink attrs and settings
>>   	upcall_interfaces			ovs: test the upcall interfaces"
>>   @@ -300,6 +301,69 @@ test_connect_v4 () {
>>   	return 0
>>   }
>>   +# nat_connect_v4 test
>> +#  - client has 1500 byte MTU
>> +#  - server has 1500 byte MTU
>> +#  - use ICMP to ping in each direction
>> +#  - only allow CT state stuff to pass through new in c -> s
>> +test_nat_connect_v4 () {
>> +	which nc >/dev/null 2>/dev/null || return $ksft_skip
>> +
>> +	sbx_add "test_nat_connect_v4" || return $?
>> +
>> +	ovs_add_dp "test_nat_connect_v4" nat4 || return 1
>> +	info "create namespaces"
>> +	for ns in client server; do
>> +		ovs_add_netns_and_veths "test_nat_connect_v4" "nat4" "$ns" \
>> +		    "${ns:0:1}0" "${ns:0:1}1" || return 1
>> +	done
>> +
>> +	ip netns exec client ip addr add 172.31.110.10/24 dev c1
>> +	ip netns exec client ip link set c1 up
>> +	ip netns exec server ip addr add 172.31.110.20/24 dev s1
>> +	ip netns exec server ip link set s1 up
>> +
>> +	ip netns exec client ip route add default via 172.31.110.20
>> +
>> +	ovs_add_flow "test_nat_connect_v4" nat4 \
>> +		'in_port(1),eth(),eth_type(0x0806),arp()' '2' || return 1
>> +	ovs_add_flow "test_nat_connect_v4" nat4 \
>> +		'in_port(2),eth(),eth_type(0x0806),arp()' '1' || return 1
>> +	ovs_add_flow "test_nat_connect_v4" nat4 \
>> +		"ct_state(-trk),in_port(1),eth(),eth_type(0x0800),ipv4(dst=192.168.0.20)" \
>> +		"ct(commit,nat(dst=172.31.110.20)),recirc(0x1)"
>> +	ovs_add_flow "test_nat_connect_v4" nat4 \
>> +		"ct_state(-trk),in_port(2),eth(),eth_type(0x0800),ipv4()" \
>> +		"ct(commit,nat),recirc(0x2)"
>> +
>> +	ovs_add_flow "test_nat_connect_v4" nat4 \
>> +		"recirc_id(0x1),ct_state(+trk-inv),in_port(1),eth(),eth_type(0x0800),ipv4()" "2"
>> +	ovs_add_flow "test_nat_connect_v4" nat4 \
>> +		"recirc_id(0x2),ct_state(+trk-inv),in_port(2),eth(),eth_type(0x0800),ipv4()" "1"
>> +
>> +	# do a ping
>> +	ovs_sbx "test_nat_connect_v4" ip netns exec client ping 192.168.0.20 -c 3 || return 1
>> +
>> +	# create an echo server in 'server'
>> +	echo "server" | \
>> +		ovs_netns_spawn_daemon "test_nat_connect_v4" "server" \
>> +				nc -lvnp 4443
>> +	ovs_sbx "test_nat_connect_v4" ip netns exec client nc -i 1 -zv 192.168.0.20 4443 || return 1
>> +
>> +	# Now test in the other direction (should fail)
>> +	echo "client" | \
>> +		ovs_netns_spawn_daemon "test_nat_connect_v4" "client" \
>> +				nc -lvnp 4443
>> +	ovs_sbx "test_nat_connect_v4" ip netns exec client nc -i 1 -zv 172.31.110.10 4443
>> +	if [ $? == 0 ]; then
>> +	   info "connect to client was successful"
>> +	   return 1
>> +	fi
>> +
>> +	info "done..."
>> +	return 0
>> +}
>> +
>>   # netlink_validation
>>   # - Create a dp
>>   # - check no warning with "old version" simulation
>> diff --git a/tools/testing/selftests/net/openvswitch/ovs-dpctl.py b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
>> index 6e258ab9e635..258c9ef263d9 100644
>> --- a/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
>> +++ b/tools/testing/selftests/net/openvswitch/ovs-dpctl.py
>> @@ -530,6 +530,81 @@ class ovsactions(nla):
>>                           else:
>>                               ctact["attrs"].append([scan[1], None])
>>                           actstr = actstr[strspn(actstr, ", ") :]
>> +                    # it seems strange to put this here, but nat() is a complex
>> +                    # sub-action and this lets it sit anywhere in the ct() action
>> +                    if actstr.startswith("nat"):
>> +                        actstr = actstr[3:]
>> +                        natact = ovsactions.ctact.natattr()
>> +
>> +                        if actstr.startswith("("):
>> +                            t = None
>> +                            actstr = actstr[1:]
>> +                            if actstr.startswith("src"):
>> +                                t = "OVS_NAT_ATTR_SRC"
>> +                                actstr = actstr[3:]
>> +                            elif actstr.startswith("dst"):
>> +                                t = "OVS_NAT_ATTR_DST"
>> +                                actstr = actstr[3:]
>> +
>> +                            actstr, ip_block_min = parse_extract_field(
>> +                                actstr, "=", "([0-9a-fA-F:\.\[]+)", str, False
>> +                            )
>> +                            actstr, ip_block_max = parse_extract_field(
>> +                                actstr, "-", "([0-9a-fA-F:\.\[]+)", str, False
>> +                            )
>> +
>> +                            # [XXXX:YYY::Z]:123
>> +                            # following RFC 3986
>> +                            # More complete parsing, ala RFC5952 isn't
>> +                            # supported.
>> +                            if actstr.startswith("]"):
>> +                                actstr = actstr[1:]
>> +                            if ip_block_min is not None and \
>> +                               ip_block_min.startswith("["):
>> +                                ip_block_min = ip_block_min[1:]
>> +                            if ip_block_max is not None and \
>> +                               ip_block_max.startswith("["):
>> +                                ip_block_max = ip_block_max[1:]
>> +
>> +                            actstr, proto_min = parse_extract_field(
>> +                                actstr, ":", "(\d+)", int, False
>> +                            )
>> +                            actstr, proto_max = parse_extract_field(
>> +                                actstr, "-", "(\d+)", int, False
>> +                            )
>
> I'm still struggling to make this part work:
> On the one hand, ipv6 seems not fully supported by ovs-dpctl.py. If I
> try adding an ipv6 flow I end up needing to add a function such as as
> the following and use it to parse "ipv6()" field:

Let's just drop the ipv6 stuff from the NAT action support, and we can
add it later when I address the flow key side of it.

> def convert_ipv6(data):
>     ip, _, mask = data.partition('/')
>     max_ip = pow(2, 128) - 1
>
>     if not ip:
>         ip = mask = 0
>     elif not mask:
>         mask = max
>     elif mask.isdigit():
>         mask = (max_ip << (128 - int(mask))) & max_ip
>
>     return ipaddress.IPv6Address(ip).packed, ipaddress.IPv6Address(mask).packed
>
> OTOH, trying to support ipv6 makes ct ip/port range parsing more
> complex, for instance, this action:
> "ct(nat(src=10.0.0.240-10.0.0.254:32768-65535))"
>
> fails, because it's parsed as:
> ip_block_min = 10.0.0.240
> ip_block_max = 10.0.0.254:32768
> proto_min = None
> proto_max = 65535
>
> I would say we could drop ipv6 support for nat() action, making it
> simpler to parse or first detect if we're parsing ipv4 or ipv6 and use
> appropriate regexp on each case. E.g:
> https://github.com/openvswitch/ovs/blob/d460c473ebf9e9ab16da44cbfbb13a4911352195/python/ovs/flow/decoders.py#L430-L486

ACK

> Another approach would be to stop trying to be human friendly and use
> an easier to parse syntax, something closer to key-value, e.g:
> "ct(ip_block_min=10.0.0.240, ip_block_max=10.0.0.254, proto_min=32768,
> proto_max=65535)". It'd be more verbose and not compatible with ovs
> tooling but this is a testing tool afterall. WDYT?

I do like that we can use the flow output from the running ovs-vswitchd
to generate test cases.  I'd like, as much as possible, to try and keep
it compatible.

>> +
>> +                            if t is not None:
>> +                                natact["attrs"].append([t, None])
>> +
>> +                                if ip_block_min is not None:
>> +                                    natact["attrs"].append(
>> +                                        ["OVS_NAT_ATTR_IP_MIN", ip_block_min]
>> +                                    )
>> +                                if ip_block_max is not None:
>> +                                    natact["attrs"].append(
>> +                                        ["OVS_NAT_ATTR_IP_MAX", ip_block_max]
>> +                                    )
>> +                                if proto_min is not None:
>> +                                    natact["attrs"].append(
>> +                                        ["OVS_NAT_ATTR_PROTO_MIN", proto_min]
>> +                                    )
>> +                                if proto_max is not None:
>> +                                    natact["attrs"].append(
>> +                                        ["OVS_NAT_ATTR_PROTO_MAX", proto_max]
>> +                                    )
>> +
>> +                            for natscan in (
>> +                                ("persist", "OVS_NAT_ATTR_PERSISTENT"),
>
> odp-util.c defines this flag as "persistent", not sure if you intend
> to keep it compatible at all.

I will adjust when I resubmit.

>> +                                ("hash", "OVS_NAT_ATTR_PROTO_HASH"),
>> +                                ("random", "OVS_NAT_ATTR_PROTO_RANDOM"),
>> +                            ):
>> +                                if actstr.startswith(natscan[0]):
>> +                                    actstr = actstr[len(natscan[0]) :]
>> +                                    natact["attrs"].append([natscan[1], None])
>> +                                    actstr = actstr[strspn(actstr, ", ") :]
>> +
>> +                        ctact["attrs"].append(["OVS_CT_ATTR_NAT", natact])
>> +                        actstr = actstr[strspn(actstr, ",) ") :]
>>                     self["attrs"].append(["OVS_ACTION_ATTR_CT",
>> ctact])
>>                   parsed = True