Implement an option to ignore generation of test entries for specific…

… control plane elements.

backends/p4tools/modules/testgen/core/small_step/table_stepper.cpp

@@ -546,8 +546,6 @@ void TableStepper::evalTargetTable(
 }
 
 bool TableStepper::eval() {
-    // Set the appropriate properties when the table is immutable, meaning it has constant entries.
-    TableUtils::checkTableImmutability(*table, properties);
     // Resolve any non-symbolic table keys. The function returns true when a key needs replacement.
     if (resolveTableKeys()) {
         return false;
@@ -578,6 +576,15 @@ TableStepper::TableStepper(ExprStepper *stepper, const IR::P4Table *table)
         const auto *action = table->getActionList()->actionList.at(index);
         properties.actionIdMap.emplace(action->controlPlaneName(), index);
     }
+
+    // Set the appropriate properties when the table is immutable, meaning it has constant entries.
+    TableUtils::checkTableImmutability(*table, properties);
+
+    // If the table is in the set of entities to skip, we set it immutable.
+    // P4Testgen will not add a control plane entry for this table.
+    if (TestgenOptions::get().skippedControlPlaneEntities.count(properties.tableName) != 0U) {
+        properties.tableIsImmutable = true;
+    }
 }
 
 }  // namespace P4Tools::P4Testgen

backends/p4tools/modules/testgen/options.cpp

@@ -113,9 +113,8 @@ TestgenOptions::TestgenOptions()
             // Each element is then again split by colon (':').
             std::stringstream argStream(arg);
             while (argStream.good()) {
-                std::string substr;
-                std::getline(argStream, substr, ',');
-                auto rangeStr = std::string(arg);
+                std::string rangeStr;
+                std::getline(argStream, rangeStr, ',');
                 size_t portStr = rangeStr.find_first_of(':');
                 try {
                     auto loPortStr = rangeStr.substr(0, portStr);
@@ -154,6 +153,22 @@ TestgenOptions::TestgenOptions()
         "target-specific port variable, it will overflow. Default behavior is delegated to the "
         "test back end. Some test back ends may restrict the available port ranges.");
 
+    registerOption(
+        "--skip-control-plane-entities", "skippedControlPlaneEntities",
+        [this](const char *arg) {
+            // Convert the input into a StringStream and split by comma (',').
+            std::stringstream argStream(arg);
+            while (argStream.good()) {
+                std::string substr;
+                std::getline(argStream, substr, ',');
+                skippedControlPlaneEntities.emplace(substr);
+            }
+            return true;
+        },
+        "Specify the set of control plane entities where P4Testgen should not generate a "
+        "configuration for. For example, if a particular table is in the set, P4Testgen will "
+        "assume that only the default action or constant entries can be executed. ");
+
     registerOption(
         "--out-dir", "outputDir",
         [this](const char *arg) {

backends/p4tools/modules/testgen/options.h

@@ -69,6 +69,9 @@ class TestgenOptions : public AbstractP4cToolOptions {
     /// TestGen will consider these when choosing input and output ports.
     std::vector<std::pair<int, int>> permittedPortRanges;
 
+    /// Skip generating a control plane entry for the entities in this list.
+    std::set<cstring> skippedControlPlaneEntities;
+
     /// Enforces the test generation of tests with mandatory output packet.
     bool outputPacketOnly = false;
 

backends/p4tools/modules/testgen/targets/bmv2/CMakeLists.txt

@@ -33,6 +33,7 @@ set(TESTGEN_SOURCES
 set(TESTGEN_GTEST_SOURCES
   ${TESTGEN_GTEST_SOURCES}
   ${CMAKE_CURRENT_SOURCE_DIR}/test/testgen_api/api_test.cpp
+  ${CMAKE_CURRENT_SOURCE_DIR}/test/testgen_api/control_plane_filter_test.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/test/test_backend/ptf.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/test/test_backend/stf.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/test/small-step/binary.cpp

backends/p4tools/modules/testgen/targets/bmv2/expr_stepper.cpp

@@ -572,7 +572,7 @@ void Bmv2V1ModelExprStepper::evalExternMethodCall(const IR::MethodCallExpression
              const auto &externInstance = state.findDecl(externRef);
              // Retrieve the register state from the object store. If it is already present, just
              // cast the object to the correct class and retrieve the current value according to the
-             // index. If the register has not been added had, create a new register object.
+             // index. If the register has not been added yet, create a new register object.
              const auto *registerState =
                  state.getTestObject("registervalues", externInstance->controlPlaneName(), false);
              const Bmv2V1ModelRegisterValue *registerValue = nullptr;

backends/p4tools/modules/testgen/targets/bmv2/test/testgen_api/control_plane_filter_test.cpp

@@ -0,0 +1,124 @@
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include "test/gtest/helpers.h"
+
+#include "backends/p4tools/modules/testgen/options.h"
+#include "backends/p4tools/modules/testgen/targets/bmv2/test_backend/protobuf_ir.h"
+#include "backends/p4tools/modules/testgen/testgen.h"
+
+namespace Test {
+
+namespace {
+
+TEST(P4TestgenControlPlaneFilterTest, FiltersControlPlaneEntities) {
+    std::stringstream streamTest;
+    streamTest << R"p4(
+header ethernet_t {
+    bit<48> dst_addr;
+    bit<48> src_addr;
+    bit<16> ether_type;
+}
+
+struct Headers {
+  ethernet_t eth_hdr;
+}
+
+struct Metadata {  }
+parser parse(packet_in pkt, out Headers hdr, inout Metadata m, inout standard_metadata_t sm) {
+  state start {
+      pkt.extract(hdr.eth_hdr);
+      transition accept;
+  }
+}
+control ingress(inout Headers hdr, inout Metadata meta, inout standard_metadata_t sm) {
+    // Drop the packet.
+    action acl_drop() {
+        mark_to_drop(sm);
+    }
+
+    table drop_table {
+        key = {
+            hdr.eth_hdr.dst_addr : ternary @name("dst_eth");
+        }
+        actions = {
+            acl_drop();
+            @defaultonly NoAction();
+        }
+    }
+
+    apply {
+        if (hdr.eth_hdr.isValid()) {
+            drop_table.apply();
+        }
+    }
+}
+control egress(inout Headers hdr, inout Metadata meta, inout standard_metadata_t sm) {
+  apply {}
+}
+control deparse(packet_out pkt, in Headers hdr) {
+  apply {
+    pkt.emit(hdr.eth_hdr);
+  }
+}
+control verifyChecksum(inout Headers hdr, inout Metadata meta) {
+  apply {}
+}
+control computeChecksum(inout Headers hdr, inout Metadata meta) {
+  apply {}
+}
+V1Switch(parse(), verifyChecksum(), ingress(), egress(), computeChecksum(), deparse()) main;
+)p4";
+    auto source = P4_SOURCE(P4Headers::V1MODEL, streamTest.str().c_str());
+    auto compilerOptions = CompilerOptions();
+    compilerOptions.target = "bmv2";
+    compilerOptions.arch = "v1model";
+    auto &testgenOptions = P4Tools::P4Testgen::TestgenOptions::get();
+    testgenOptions.testBackend = "PROTOBUF_IR";
+    testgenOptions.testBaseName = "dummy";
+    testgenOptions.seed = 1;
+    testgenOptions.maxTests = 0;
+    // Create a bespoke packet for the Ethernet extract call.
+    testgenOptions.minPktSize = 112;
+    testgenOptions.maxPktSize = 112;
+
+    // First, we ensure that tests are generated correctly. We expect two tests.
+    // One which exercises action acl_drop and one which exercises the default action, NoAction.
+    {
+        auto testListOpt =
+            P4Tools::P4Testgen::Testgen::generateTests(source, compilerOptions, testgenOptions);
+
+        ASSERT_TRUE(testListOpt.has_value());
+        auto testList = testListOpt.value();
+        ASSERT_EQ(testList.size(), 2);
+        const auto *testWithDrop =
+            testList[0]->checkedTo<P4Tools::P4Testgen::Bmv2::ProtobufIrTest>();
+        EXPECT_THAT(testWithDrop->getFormattedTest(),
+                    testing::Not(testing::HasSubstr(R"(expected_packet)")));
+        const auto *testWithForwarding =
+            testList[1]->checkedTo<P4Tools::P4Testgen::Bmv2::ProtobufIrTest>();
+        EXPECT_THAT(testWithForwarding->getFormattedTest(),
+                    testing::HasSubstr(R"(expected_output_packet)"));
+    }
+
+    // Now we install a filter.
+    // Since we can not generate a config for the table we should only generate one test.
+    {
+        testgenOptions.skippedControlPlaneEntities = {"ingress.drop_table"};
+
+        auto testListOpt =
+            P4Tools::P4Testgen::Testgen::generateTests(source, compilerOptions, testgenOptions);
+
+        ASSERT_TRUE(testListOpt.has_value());
+        auto testList = testListOpt.value();
+        ASSERT_EQ(testList.size(), 1);
+        const auto *test = testList[0];
+        const auto *protobufIrTest = test->checkedTo<P4Tools::P4Testgen::Bmv2::ProtobufIrTest>();
+        EXPECT_THAT(protobufIrTest->getFormattedTest(),
+                    testing::Not(testing::HasSubstr(R"(expected_packet)")));
+    }
+}
+
+}  // namespace
+
+}  // namespace Test