Populate ingress_ifindex in xdp_md struct. (#449)

* fix

* add tests

* export program info

* delete ebpfapi post build

* fix tests

* code cleanup

* cr comment

src/xdp/program.c

@@ -238,7 +238,7 @@ XdpInvokeEbpf(
     XdpMd.Base.data = Va;
     XdpMd.Base.data_end = Va + Buffer->DataLength;
     XdpMd.Base.data_meta = 0;
-    XdpMd.Base.ingress_ifindex = IFI_UNSPECIFIED;
+    XdpMd.Base.ingress_ifindex = InspectionContext->IfIndex;
 
     ebpf_program_batch_invoke_function_t EbpfInvokeProgram =
         EbpfExtensionClientGetProgramDispatch(Client)->ebpf_program_batch_invoke_function;

src/xdp/program.h

@@ -15,6 +15,7 @@ typedef ebpf_execution_context_state_t XDP_INSPECTION_EBPF_CONTEXT;
 typedef struct _XDP_INSPECTION_CONTEXT {
     XDP_INSPECTION_EBPF_CONTEXT EbpfContext;
     XDP_REDIRECT_CONTEXT RedirectContext;
+    ULONG IfIndex;
 } XDP_INSPECTION_CONTEXT;
 
 //

src/xdp/rx.c

@@ -1009,6 +1009,7 @@ XdpRxQueueCreate(
     XdpQueueSyncInitialize(&RxQueue->Sync);
     RxQueue->Binding = Binding;
     RxQueue->Key = Key;
+    RxQueue->InspectionContext.IfIndex = XdpIfGetIfIndex(Binding);
     XdpInitializeQueueInfo(&RxQueue->QueueInfo, XDP_QUEUE_TYPE_DEFAULT_RSS, QueueId);
     XdbgInitializeQueueEc(RxQueue);
 

test/bpf/bpf.vcxproj

@@ -34,14 +34,16 @@
   <ItemDefinitionGroup>
     <PreBuildEvent>
       <Command>
-       set PATH=%PATH%;$(EbpfPackagePath)build\native\bin
+        xcopy $(EbpfPackagePath)build\native\bin\EbpfApi.dll $(SolutionDir)artifacts\bin\$(Platform)_$(Configuration) /Y
+        $(EbpfPackagePath)build\native\bin\export_program_info.exe
         $(SolutionDir)artifacts\bin\$(Platform)_$(Configuration)\xdp_bpfexport.exe
       </Command>
     </PreBuildEvent>
     <PostBuildEvent>
       <Command>
-        set PATH=%PATH%;$(EbpfPackagePath)build\native\bin
         $(SolutionDir)artifacts\bin\$(Platform)_$(Configuration)\xdp_bpfexport.exe --clear
+        $(EbpfPackagePath)build\native\bin\export_program_info.exe --clear
+        del $(SolutionDir)artifacts\bin\$(Platform)_$(Configuration)\ebpfapi.dll /F
       </Command>
     </PostBuildEvent>
   </ItemDefinitionGroup>
@@ -66,6 +68,16 @@
         rmdir /s /q $(OutDir)\drop_km
         popd</Command>
     </CustomBuild>
+    <CustomBuild Include="selective_drop.c">
+      <FileType>CppCode</FileType>
+      <Outputs>$(OutDir)selective_drop.sys</Outputs>
+      <Command>
+        clang -g -target bpf -O2 -Werror $(ClangIncludes) -c %(Filename).c -o $(OutDir)%(Filename).o
+        pushd $(OutDir)
+        powershell -NonInteractive -ExecutionPolicy Unrestricted $(EbpfBinPath)\Convert-BpfToNative.ps1 -FileName %(Filename) -IncludeDir $(EbpfIncludePath) -Platform $(Platform) -Configuration $(Configuration) -KernelMode $true
+        rmdir /s /q $(OutDir)\selective_drop_km
+        popd</Command>
+    </CustomBuild>
     <CustomBuild Include="l1fwd.c">
       <FileType>CppCode</FileType>
       <Outputs>$(OutDir)l1fwd.sys</Outputs>

test/bpf/selective_drop.c

@@ -0,0 +1,57 @@
+//
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+//
+
+#include "bpf_endian.h"
+#include "bpf_helpers.h"
+
+// Map configured by user mode to drop packets from a specific interface.
+struct
+{
+    __uint(type, BPF_MAP_TYPE_ARRAY);
+    __type(key, uint32_t);
+    __type(value, uint32_t);
+    __uint(max_entries, 1);
+} interface_map SEC(".maps");
+
+// Map to track the number of dropped packets.
+struct
+{
+    __uint(type, BPF_MAP_TYPE_ARRAY);
+    __type(key, uint32_t);
+    __type(value, uint64_t);
+    __uint(max_entries, 1);
+} dropped_packet_map SEC(".maps");
+
+SEC("xdp/selective_drop")
+int
+selective_drop(xdp_md_t *ctx)
+{
+    int action = XDP_PASS;
+    int zero = 0;
+
+    uint32_t *interface_index = bpf_map_lookup_elem(&interface_map, &zero);
+    if (!interface_index) {
+        bpf_printk("selective_drop: interface_map lookup failed.");
+        goto Exit;
+    }
+
+    if (*interface_index == ctx->ingress_ifindex) {
+        action = XDP_DROP;
+        bpf_printk("selective_drop: interface_map lookup found matching interface %d", *interface_index);
+
+        uint64_t *dropped_packet_count = bpf_map_lookup_elem(&dropped_packet_map, &zero);
+        if (dropped_packet_count) {
+            *dropped_packet_count += 1;
+        } else {
+            uint64_t dropped_packet_count = 1;
+            bpf_map_update_elem(&dropped_packet_map, &zero, &dropped_packet_count, BPF_ANY);
+        }
+    } else {
+        bpf_printk("selective_drop: interface_map lookup found non-matching interface %d, expected %d", *interface_index, ctx->ingress_ifindex);
+    }
+
+Exit:
+    return action;
+}

test/functional/lib/tests.cpp

@@ -4708,6 +4708,69 @@ ProgTestRunRxEbpfPayload()
     TEST_EQUAL(memcmp(UdpFrameV4, UdpFrameOutV4, sizeof(UdpFrameV4)), 0);
 }
 
+VOID
+GenericRxEbpfIfIndex()
+{
+    auto If = FnMpIf;
+    wil::unique_handle GenericMp;
+    wil::unique_handle FnLwf;
+    const UCHAR Payload[] = "GenericRxEbpfIfIndex";
+    UINT32 Zero = 0;
+
+    unique_bpf_object BpfObject = AttachEbpfXdpProgram(If, "\\bpf\\selective_drop.sys", "selective_drop");
+
+    GenericMp = MpOpenGeneric(If.GetIfIndex());
+    FnLwf = LwfOpenDefault(If.GetIfIndex());
+
+    // Get the interface_map fd.
+    fd_t interface_map_fd = bpf_object__find_map_fd_by_name(BpfObject.get(), "interface_map");
+    TEST_NOT_EQUAL(interface_map_fd, ebpf_fd_invalid);
+
+    // Update the interface_map with the interface index of the test interface.
+    UINT32 IfIndex = If.GetIfIndex();
+    TEST_NOT_EQUAL(IfIndex, IFI_UNSPECIFIED);
+
+    TEST_EQUAL(0, bpf_map_update_elem(interface_map_fd, &Zero, &IfIndex, BPF_ANY));
+
+    std::vector<UCHAR> Mask(sizeof(Payload), 0xFF);
+    LwfRxFilter(FnLwf, Payload, &Mask[0], sizeof(Payload));
+
+    RX_FRAME Frame;
+    RxInitializeFrame(&Frame, If.GetQueueId(), Payload, sizeof(Payload));
+    TEST_HRESULT(MpRxEnqueueFrame(GenericMp, &Frame));
+    MpRxFlush(GenericMp);
+
+    Sleep(TEST_TIMEOUT_ASYNC_MS);
+
+    UINT32 FrameLength = 0;
+    // Packet should be dropped.
+    TEST_EQUAL(
+        HRESULT_FROM_WIN32(ERROR_NOT_FOUND),
+        LwfRxGetFrame(FnLwf, If.GetQueueId(), &FrameLength, NULL));
+
+    // Validate that the dropped_packet_map contains a non-0 entry for the IfIndex.
+    fd_t dropped_packet_map_fd = bpf_object__find_map_fd_by_name(BpfObject.get(), "dropped_packet_map");
+    TEST_NOT_EQUAL(dropped_packet_map_fd, ebpf_fd_invalid);
+
+    UINT64 DroppedPacketCount = 0;
+    TEST_EQUAL(0, bpf_map_lookup_elem(dropped_packet_map_fd, &Zero, &DroppedPacketCount));
+    TEST_EQUAL(DroppedPacketCount, 1);
+
+    // Now set the ifIndex to some other value and verify that the packet is not dropped.
+    UINT32 OtherIfIndex = If.GetIfIndex() + 1;
+    TEST_EQUAL(0, bpf_map_update_elem(interface_map_fd, &Zero, &OtherIfIndex, BPF_ANY));
+
+    TEST_HRESULT(MpRxEnqueueFrame(GenericMp, &Frame));
+    MpRxFlush(GenericMp);
+
+    Sleep(TEST_TIMEOUT_ASYNC_MS);
+
+    // Packet should not be dropped.
+    TEST_EQUAL(
+        HRESULT_FROM_WIN32(ERROR_MORE_DATA),
+        LwfRxGetFrame(FnLwf, If.GetQueueId(), &FrameLength, NULL));
+}
+
 VOID
 GenericRxEbpfFragments()
 {

test/functional/lib/tests.h

@@ -121,6 +121,9 @@ GenericRxEbpfPayload();
 VOID
 ProgTestRunRxEbpfPayload();
 
+VOID
+GenericRxEbpfIfIndex();
+
 VOID
 GenericRxEbpfFragments();
 

test/functional/taef/tests.cpp

@@ -424,6 +424,10 @@ TEST_CLASS(xdpfunctionaltests)
         ::ProgTestRunRxEbpfPayload();
     }
 
+    TEST_METHOD(GenericRxEbpfIfIndex) {
+        ::GenericRxEbpfIfIndex();
+    }
+
     TEST_METHOD(GenericRxEbpfFragments) {
         ::GenericRxEbpfFragments();
     }