[PATCH v4 3/7] dts: add optional packet filtering to scapy sniffer

[jspewock@iol.unh.edu]

From: Jeremy Spewock <jspewock@iol.unh.edu>

Added the options to filter out LLDP and ARP packets when
sniffing for packets with scapy. This was done using BPF filters to
ensure that the noise these packets provide does not interfere with test
cases.

Signed-off-by: Jeremy Spewock <jspewock@iol.unh.edu>
---
 dts/framework/test_suite.py                   | 14 ++++++++--
 .../capturing_traffic_generator.py            | 22 ++++++++++++++-
 dts/framework/testbed_model/scapy.py          | 28 ++++++++++++++++++-
 dts/framework/testbed_model/tg_node.py        | 12 ++++++--
 4 files changed, 70 insertions(+), 6 deletions(-)

diff --git a/dts/framework/test_suite.py b/dts/framework/test_suite.py
index 4a7907ec33..6dfa570041 100644
--- a/dts/framework/test_suite.py
+++ b/dts/framework/test_suite.py
@@ -27,6 +27,7 @@
 from .settings import SETTINGS
 from .test_result import BuildTargetResult, Result, TestCaseResult, TestSuiteResult
 from .testbed_model import SutNode, TGNode
+from .testbed_model.capturing_traffic_generator import PacketFilteringConfig
 from .testbed_model.hw.port import Port, PortLink
 from .utils import get_packet_summaries
 
@@ -149,7 +150,12 @@ def configure_testbed_ipv4(self, restore: bool = False) -> None:
     def _configure_ipv4_forwarding(self, enable: bool) -> None:
         self.sut_node.configure_ipv4_forwarding(enable)
 
-    def send_packet_and_capture(self, packet: Packet, duration: float = 1) -> list[Packet]:
+    def send_packet_and_capture(
+        self,
+        packet: Packet,
+        filter_config: PacketFilteringConfig = PacketFilteringConfig(),
+        duration: float = 1,
+    ) -> list[Packet]:
         """
         Send a packet through the appropriate interface and
         receive on the appropriate interface.
@@ -158,7 +164,11 @@ def send_packet_and_capture(self, packet: Packet, duration: float = 1) -> list[P
         """
         packet = self._adjust_addresses(packet)
         return self.tg_node.send_packet_and_capture(
-            packet, self._tg_port_egress, self._tg_port_ingress, duration
+            packet,
+            self._tg_port_egress,
+            self._tg_port_ingress,
+            filter_config,
+            duration,
         )
 
     def get_expected_packet(self, packet: Packet) -> Packet:
diff --git a/dts/framework/testbed_model/capturing_traffic_generator.py b/dts/framework/testbed_model/capturing_traffic_generator.py
index e6512061d7..c40b030fe4 100644
--- a/dts/framework/testbed_model/capturing_traffic_generator.py
+++ b/dts/framework/testbed_model/capturing_traffic_generator.py
@@ -11,6 +11,7 @@
 
 import uuid
 from abc import abstractmethod
+from dataclasses import dataclass
 
 import scapy.utils  # type: ignore[import]
 from scapy.packet import Packet  # type: ignore[import]
@@ -29,6 +30,19 @@ def _get_default_capture_name() -> str:
     return str(uuid.uuid4())
 
 
+@dataclass(slots=True)
+class PacketFilteringConfig:
+    """The supported filtering options for :class:`CapturingTrafficGenerator`.
+
+    Attributes:
+        no_lldp: If :data:`True`, LLDP packets will be filtered out when capturing.
+        no_arp: If :data:`True`, ARP packets will be filtered out when capturing.
+    """
+
+    no_lldp: bool = True
+    no_arp: bool = True
+
+
 class CapturingTrafficGenerator(TrafficGenerator):
     """Capture packets after sending traffic.
 
@@ -51,6 +65,7 @@ def send_packet_and_capture(
         packet: Packet,
         send_port: Port,
         receive_port: Port,
+        filter_config: PacketFilteringConfig,
         duration: float,
         capture_name: str = _get_default_capture_name(),
     ) -> list[Packet]:
@@ -64,6 +79,7 @@ def send_packet_and_capture(
             packet: The packet to send.
             send_port: The egress port on the TG node.
             receive_port: The ingress port in the TG node.
+            filter_config: Filters to apply when capturing packets.
             duration: Capture traffic for this amount of time after sending the packet.
             capture_name: The name of the .pcap file where to store the capture.
 
@@ -71,7 +87,7 @@ def send_packet_and_capture(
              A list of received packets. May be empty if no packets are captured.
         """
         return self.send_packets_and_capture(
-            [packet], send_port, receive_port, duration, capture_name
+            [packet], send_port, receive_port, filter_config, duration, capture_name
         )
 
     def send_packets_and_capture(
@@ -79,6 +95,7 @@ def send_packets_and_capture(
         packets: list[Packet],
         send_port: Port,
         receive_port: Port,
+        filter_config: PacketFilteringConfig,
         duration: float,
         capture_name: str = _get_default_capture_name(),
     ) -> list[Packet]:
@@ -92,6 +109,7 @@ def send_packets_and_capture(
             packets: The packets to send.
             send_port: The egress port on the TG node.
             receive_port: The ingress port in the TG node.
+            filter_config: Filters to apply when capturing packets.
             duration: Capture traffic for this amount of time after sending the packets.
             capture_name: The name of the .pcap file where to store the capture.
 
@@ -106,6 +124,7 @@ def send_packets_and_capture(
             packets,
             send_port,
             receive_port,
+            filter_config,
             duration,
         )
 
@@ -119,6 +138,7 @@ def _send_packets_and_capture(
         packets: list[Packet],
         send_port: Port,
         receive_port: Port,
+        filter_config: PacketFilteringConfig,
         duration: float,
     ) -> list[Packet]:
         """
diff --git a/dts/framework/testbed_model/scapy.py b/dts/framework/testbed_model/scapy.py
index 9083e92b3d..94b0af7c6f 100644
--- a/dts/framework/testbed_model/scapy.py
+++ b/dts/framework/testbed_model/scapy.py
@@ -30,6 +30,7 @@
 
 from .capturing_traffic_generator import (
     CapturingTrafficGenerator,
+    PacketFilteringConfig,
     _get_default_capture_name,
 )
 from .hw.port import Port
@@ -69,6 +70,7 @@ def scapy_send_packets_and_capture(
     send_iface: str,
     recv_iface: str,
     duration: float,
+    sniff_filter: str,
 ) -> list[bytes]:
     """RPC function to send and capture packets.
 
@@ -90,6 +92,7 @@ def scapy_send_packets_and_capture(
         iface=recv_iface,
         store=True,
         started_callback=lambda *args: scapy.all.sendp(scapy_packets, iface=send_iface),
+        filter=sniff_filter,
     )
     sniffer.start()
     time.sleep(duration)
@@ -249,16 +252,38 @@ def _send_packets(self, packets: list[Packet], port: Port) -> None:
         packets = [packet.build() for packet in packets]
         self.rpc_server_proxy.scapy_send_packets(packets, port.logical_name)
 
+    def _create_packet_filter(self, filter_config: PacketFilteringConfig) -> str:
+        """Combines filter settings from `filter_config` into a BPF that scapy can use.
+
+        Scapy allows for the use of Berkeley Packet Filters (BPFs) to filter what packets are
+        collected based on various attributes of the packet.
+
+        Args:
+            filter_config: Config class that specifies which filters should be applied.
+
+        Returns:
+            A string representing the combination of BPF filters to be passed to scapy. For
+            example:
+
+            "ether[12:2] != 0x88cc && ether[12:2] != 0x0806"
+        """
+        bpf_filter: list[str] = []
+        if filter_config.no_arp:
+            bpf_filter.append("ether[12:2] != 0x0806")
+        if filter_config.no_lldp:
+            bpf_filter.append("ether[12:2] != 0x88cc")
+        return " && ".join(bpf_filter)
+
     def _send_packets_and_capture(
         self,
         packets: list[Packet],
         send_port: Port,
         receive_port: Port,
+        filter_config: PacketFilteringConfig,
         duration: float,
         capture_name: str = _get_default_capture_name(),
     ) -> list[Packet]:
         binary_packets = [packet.build() for packet in packets]
-
         xmlrpc_packets: list[
             xmlrpc.client.Binary
         ] = self.rpc_server_proxy.scapy_send_packets_and_capture(
@@ -266,6 +291,7 @@ def _send_packets_and_capture(
             send_port.logical_name,
             receive_port.logical_name,
             duration,
+            self._create_packet_filter(filter_config),
         )  # type: ignore[assignment]
 
         scapy_packets = [Ether(packet.data) for packet in xmlrpc_packets]
diff --git a/dts/framework/testbed_model/tg_node.py b/dts/framework/testbed_model/tg_node.py
index 79a55663b5..475dc2968d 100644
--- a/dts/framework/testbed_model/tg_node.py
+++ b/dts/framework/testbed_model/tg_node.py
@@ -23,7 +23,10 @@
 )
 from framework.exception import ConfigurationError
 
-from .capturing_traffic_generator import CapturingTrafficGenerator
+from .capturing_traffic_generator import (
+    CapturingTrafficGenerator,
+    PacketFilteringConfig,
+)
 from .hw.port import Port
 from .node import Node
 
@@ -53,6 +56,7 @@ def send_packet_and_capture(
         packet: Packet,
         send_port: Port,
         receive_port: Port,
+        filter_config: PacketFilteringConfig = PacketFilteringConfig(),
         duration: float = 1,
     ) -> list[Packet]:
         """Send a packet, return received traffic.
@@ -71,7 +75,11 @@ def send_packet_and_capture(
              A list of received packets. May be empty if no packets are captured.
         """
         return self.traffic_generator.send_packet_and_capture(
-            packet, send_port, receive_port, duration
+            packet,
+            send_port,
+            receive_port,
+            filter_config,
+            duration,
         )
 
     def close(self) -> None:
-- 
2.43.0