Re: [PATCH v3 1/4] dts: add send_packets to test suites and rework packet addressing

[Nicholas Pratte <npratte@iol.unh.edu>]

I'll make sure to look over the other parts of this series and leave
reviews at some point next week, but I prioritized this since I will
be using this patch at some point in my GRE suites.


> diff --git a/dts/framework/test_suite.py b/dts/framework/test_suite.py
> index 694b2eba65..0b678ed62d 100644
> --- a/dts/framework/test_suite.py
> +++ b/dts/framework/test_suite.py
> @@ -199,7 +199,7 @@ def send_packet_and_capture(
>          Returns:
>              A list of received packets.
>          """
> -        packet = self._adjust_addresses(packet)
> +        packet = self._adjust_addresses([packet])[0]
>          return self.tg_node.send_packet_and_capture(
>              packet,
>              self._tg_port_egress,
> @@ -208,6 +208,18 @@ def send_packet_and_capture(
>              duration,
>          )
>
> +    def send_packets(
> +        self,
> +        packets: list[Packet],
> +    ) -> None:
> +        """Send packets using the traffic generator and do not capture received traffic.
> +
> +        Args:
> +            packets: Packets to send.
> +        """
> +        packets = self._adjust_addresses(packets)
> +        self.tg_node.send_packets(packets, self._tg_port_egress)
> +
>      def get_expected_packet(self, packet: Packet) -> Packet:
>          """Inject the proper L2/L3 addresses into `packet`.
>
> @@ -219,39 +231,59 @@ def get_expected_packet(self, packet: Packet) -> Packet:
>          """
>          return self._adjust_addresses(packet, expected=True)
>
> -    def _adjust_addresses(self, packet: Packet, expected: bool = False) -> Packet:
> +    def _adjust_addresses(self, packets: list[Packet], expected: bool = False) -> list[Packet]:
>          """L2 and L3 address additions in both directions.
>
> +        Only missing addresses are added to packets, existing addressed will not be overridden.

addressed should be addresses. Only saw this because of Chrome's
built-in grammar correction.

> +
>          Assumptions:
>              Two links between SUT and TG, one link is TG -> SUT, the other SUT -> TG.
>
>          Args:
> -            packet: The packet to modify.
> +            packets: The packets to modify.
>              expected: If :data:`True`, the direction is SUT -> TG,
>                  otherwise the direction is TG -> SUT.
>          """
> -        if expected:
> -            # The packet enters the TG from SUT
> -            # update l2 addresses
> -            packet.src = self._sut_port_egress.mac_address
> -            packet.dst = self._tg_port_ingress.mac_address
> +        ret_packets = []
> +        for packet in packets:
> +            default_pkt_src = type(packet)().src
> +            default_pkt_dst = type(packet)().dst

This is really just a probing question for my sake, but what is the
difference between the solution you have above type(packet)().src and
Ether().src? Is there a preferred means of doing this?

> +            default_pkt_payload_src = IP().src if hasattr(packet.payload, "src") else None
> +            default_pkt_payload_dst = IP().dst if hasattr(packet.payload, "dst") else None
> +            # If `expected` is :data:`True`, the packet enters the TG from SUT, otherwise the
> +            # packet leaves the TG towards the SUT
>
> -            # The packet is routed from TG egress to TG ingress
> -            # update l3 addresses
> -            packet.payload.src = self._tg_ip_address_egress.ip.exploded
> -            packet.payload.dst = self._tg_ip_address_ingress.ip.exploded

This is where it gets a little tricky. There will be circumstances,
albeit probably infrequently, where a user-created packet has more
than one IP layer, such as the ones I am using in the ipgre and nvgre
test suites that I am writing. In these cases, you need to specify an
index of the IP layer you want to modify, otherwise it will modify the
outermost IP layer in the packet (the IP layer outside the GRE layer.
See my previous comment for an example packet). Should be pretty easy
to fix, you just need to check if a packet contains an GRE layer, and
if it does, modify the packet by doing something like
packet[IP][1].src = self._tg_ip_address_egress.ip.exploded.

> -        else:
> -            # The packet leaves TG towards SUT
>              # update l2 addresses
> -            packet.src = self._tg_port_egress.mac_address
> -            packet.dst = self._sut_port_ingress.mac_address

You wouldn't need to make changes to how Ether addresses get allocated
if accounting for GRE as described above, since I'm pretty sure there
aren't really circumstances where packets would have more than one
Ethernet header, at least not that I've seen (GRE packets only have
one).

> +            if packet.src == default_pkt_src:
> +                packet.src = (
> +                    self._sut_port_egress.mac_address
> +                    if expected
> +                    else self._tg_port_egress.mac_address
> +                )
> +            if packet.dst == default_pkt_dst:
> +                packet.dst = (
> +                    self._tg_port_ingress.mac_address
> +                    if expected
> +                    else self._sut_port_ingress.mac_address
> +                )
> +
> +            # The packet is routed from TG egress to TG ingress regardless of if it is expected or

Maybe change 'regardless of if it is expected' to 'regardless of
whether it is expected.' It's admittedly picky of me, but I think it
reads a little bit better.

> +            # not.
>
> -            # The packet is routed from TG egress to TG ingress
>              # update l3 addresses
> -            packet.payload.src = self._tg_ip_address_egress.ip.exploded
> -            packet.payload.dst = self._tg_ip_address_ingress.ip.exploded
> -
> -        return Ether(packet.build())
> +            if (
> +                default_pkt_payload_src is not None
> +                and packet.payload.src == default_pkt_payload_src
> +            ):
> +                packet.payload.src = self._tg_ip_address_egress.ip.exploded
> +            if (
> +                default_pkt_payload_dst is not None
> +                and packet.payload.dst == default_pkt_payload_dst
> +            ):
> +                packet.payload.dst = self._tg_ip_address_ingress.ip.exploded
> +            ret_packets.append(Ether(packet.build()))
> +
> +        return ret_packets
>
>      def verify(self, condition: bool, failure_description: str) -> None:
>          """Verify `condition` and handle failures.
> diff --git a/dts/framework/testbed_model/tg_node.py b/dts/framework/testbed_model/tg_node.py
> index 4ee326e99c..758b676258 100644
> --- a/dts/framework/testbed_model/tg_node.py
> +++ b/dts/framework/testbed_model/tg_node.py
> @@ -83,6 +83,15 @@ def send_packet_and_capture(
>              duration,
>          )
>
> +    def send_packets(self, packets: list[Packet], port: Port):
> +        """Send packets without capturing resulting received packets.
> +
> +        Args:
> +            packets: Packets to send.
> +            port: Port to send the packets on.
> +        """
> +        self.traffic_generator.send_packets(packets, port)
> +
>      def close(self) -> None:
>          """Free all resources used by the node.
>
> --
> 2.45.2
>