Reallocate packet (#3344)

* reallocate_packet.

* PR Feedback.

docs/eBpfExtensions.md

@@ -141,13 +141,32 @@ in the context descriptor.
 
 #### `ebpf_helper_function_prototype_t` Struct
 This structure is used to describe the prototypes of the various helper functions implemented by the extension.
+```c
+typedef struct _ebpf_helper_function_prototype_flags
+{
+    bool reallocate_packet : 1;
+} ebpf_helper_function_prototype_flags_t;
+
+typedef struct _ebpf_helper_function_prototype
+{
+    ebpf_extension_header_t header;
+    uint32_t helper_id;
+    const char* name;
+    ebpf_return_type_t return_type;
+    ebpf_argument_type_t arguments[5];
+    ebpf_helper_function_prototype_flags_t flags;
+} ebpf_helper_function_prototype_t;
+```
 * `header`: Version and size.
 * `helper_id`: Integer signifying the helper function ID. (See section 2.6).
 Helper function IDs for different program types need not be unique.
 * `name`: Helper function name.
 * `return_type`: Set the appropriate value for the `ebpf_return_type_t` enum that represents the return type of the
 helper function.
 * `arguments`: Array of (at most) five helper function arguments of type `ebpf_argument_type_t`.
+* `flags`: Bit field of flags.
+   * `reallocate_packet`: Flag indicating if this helper function performs packet reallocation.
+
 
 #### `ebpf_argument_type_t` Enum
 This enum describes the various argument types that can be passed to an eBPF helper function. This is defined in the

include/ebpf_program_types.h

@@ -21,6 +21,11 @@ typedef struct _ebpf_program_type_descriptor
     char is_privileged;
 } ebpf_program_type_descriptor_t;
 
+typedef struct _ebpf_helper_function_prototype_flags
+{
+    bool reallocate_packet : 1;
+} ebpf_helper_function_prototype_flags_t;
+
 // This is the type definition for the eBPF helper function prototype
 // when version is EBPF_HELPER_FUNCTION_PROTOTYPE_CURRENT_VERSION.
 typedef struct _ebpf_helper_function_prototype
@@ -30,6 +35,7 @@ typedef struct _ebpf_helper_function_prototype
     const char* name;
     ebpf_return_type_t return_type;
     ebpf_argument_type_t arguments[5];
+    ebpf_helper_function_prototype_flags_t flags;
 } ebpf_helper_function_prototype_t;
 
 // This is the type definition for the eBPF program information

include/ebpf_windows.h

@@ -23,6 +23,7 @@ typedef unsigned short wchar_t;
 typedef unsigned int uint32_t;
 typedef unsigned long long uint64_t;
 typedef unsigned long long size_t;
+#define bool _Bool
 #endif
 
 // This file contains eBPF definitions needed by eBPF programs as well as
@@ -52,6 +53,7 @@ typedef unsigned long long size_t;
 #define EBPF_PROGRAM_DATA_HELPER_COUNT L"HelperCount"
 
 #define EBPF_HELPER_DATA_PROTOTYPE L"Prototype"
+#define EBPF_HELPER_DATA_REALLOCATE_PACKET L"ReallocatePacket"
 
 #define EBPF_DATA_BPF_PROG_TYPE L"BpfProgType"
 #define EBPF_DATA_BPF_ATTACH_TYPE L"BpfAttachType"
@@ -81,7 +83,7 @@ typedef enum _ebpf_helper_function
 
 #define EBPF_HELPER_FUNCTION_PROTOTYPE_CURRENT_VERSION 1
 #define EBPF_HELPER_FUNCTION_PROTOTYPE_CURRENT_VERSION_SIZE \
-    EBPF_SIZE_INCLUDING_FIELD(ebpf_helper_function_prototype_t, arguments)
+    EBPF_SIZE_INCLUDING_FIELD(ebpf_helper_function_prototype_t, flags)
 
 #define EBPF_PROGRAM_INFORMATION_CURRENT_VERSION 1
 #define EBPF_PROGRAM_INFORMATION_CURRENT_VERSION_SIZE \

libs/api_common/store_helper_internal.cpp

@@ -63,6 +63,7 @@ _ebpf_store_load_helper_prototype(
     char serialized_data[sizeof(ebpf_helper_function_prototype_t)] = {0};
     size_t expected_size = sizeof(helper_prototype->helper_id) + sizeof(helper_prototype->return_type) +
                            sizeof(helper_prototype->arguments);
+    uint32_t reallocate_packet_value = 0;
 
     EBPF_LOG_ENTRY();
 
@@ -95,6 +96,9 @@ _ebpf_store_load_helper_prototype(
     memcpy(&helper_prototype->arguments, serialized_data + offset, sizeof(helper_prototype->arguments));
     offset += sizeof(helper_prototype->arguments);
 
+    (void)ebpf_read_registry_value_dword(helper_info_key, EBPF_HELPER_DATA_REALLOCATE_PACKET, &reallocate_packet_value);
+    helper_prototype->flags.reallocate_packet = !!reallocate_packet_value;
+
     try {
         helper_prototype->name =
             cxplat_duplicate_string(ebpf_down_cast_from_wstring(std::wstring(helper_name)).c_str());

libs/api_common/windows_helpers.cpp

@@ -64,5 +64,7 @@ get_helper_prototype_windows(int32_t n)
         verifier_prototype.argument_type[i] = raw_prototype->arguments[i];
     }
 
+    verifier_prototype.reallocate_packet = raw_prototype->flags.reallocate_packet == TRUE;
+
     return verifier_prototype;
 }

libs/execution_context/ebpf_program.c

@@ -2090,6 +2090,7 @@ _IRQL_requires_max_(PASSIVE_LEVEL) static ebpf_result_t _ebpf_program_compute_pr
     //   b. Helper name.
     //   c. Helper return type.
     //   d. Helper argument types.
+    //   e. reallocate_packet flag (if set).
 
     // Note:
     // Order and fields being hashed is important. The order and fields being hashed must match the order and fields
@@ -2155,6 +2156,14 @@ _IRQL_requires_max_(PASSIVE_LEVEL) static ebpf_result_t _ebpf_program_compute_pr
                 goto Exit;
             }
         }
+
+        // This check for flags is temporary, until https://github.com/microsoft/ebpf-for-windows/issues/3429 is fixed.
+        if (helper_function_prototype->flags.reallocate_packet != 0) {
+            result = EBPF_CRYPTOGRAPHIC_HASH_APPEND_VALUE(cryptographic_hash, helper_function_prototype->flags);
+            if (result != EBPF_SUCCESS) {
+                goto Exit;
+            }
+        }
     }
     *hash_length = 0;
     result = ebpf_cryptographic_hash_get_hash_length(cryptographic_hash, hash_length);

libs/shared/ebpf_serialize.c

@@ -32,6 +32,7 @@ typedef struct _ebpf_serialized_helper_function_prototype
     uint32_t helper_id;
     ebpf_return_type_t return_type;
     ebpf_argument_type_t arguments[5];
+    ebpf_helper_function_prototype_flags_t flags;
     size_t name_length;
     uint8_t name[1];
 } ebpf_serialized_helper_function_prototype_t;
@@ -477,6 +478,7 @@ ebpf_serialize_program_info(
             for (uint16_t index = 0; index < EBPF_COUNT_OF(helper_prototype->arguments); index++) {
                 serialized_helper_prototype->arguments[index] = helper_prototype->arguments[index];
             }
+            serialized_helper_prototype->flags = helper_prototype->flags;
             serialized_helper_prototype->name_length = helper_function_name_length;
             // Copy the program type descriptor name buffer.
             memcpy(serialized_helper_prototype->name, helper_prototype->name, helper_function_name_length);
@@ -657,6 +659,7 @@ ebpf_deserialize_program_info(
         for (int i = 0; i < EBPF_COUNT_OF(helper_prototype->arguments); i++) {
             helper_prototype->arguments[i] = serialized_helper_prototype->arguments[i];
         }
+        helper_prototype->flags = serialized_helper_prototype->flags;
 
         // Adjust remaining buffer length.
         result = ebpf_safe_size_t_subtract(

libs/shared/shared_common.c

@@ -34,12 +34,12 @@ size_t _ebpf_attach_provider_data_supported_size[] = {EBPF_ATTACH_PROVIDER_DATA_
 #define EBPF_PROGRAM_TYPE_DESCRIPTOR_SIZE_0 EBPF_OFFSET_OF(ebpf_program_type_descriptor_t, is_privileged) + sizeof(char)
 size_t _ebpf_program_type_descriptor_supported_size[] = {EBPF_PROGRAM_TYPE_DESCRIPTOR_SIZE_0};
 
-#define EBPF_HELPER_FUNCTION_PROTOTYPE_SIZE_0 \
-    EBPF_OFFSET_OF(ebpf_helper_function_prototype_t, arguments) + 5 * sizeof(ebpf_argument_type_t)
-size_t _ebpf_helper_function_prototype_supported_size[] = {EBPF_HELPER_FUNCTION_PROTOTYPE_SIZE_0};
+#define EBPF_HELPER_FUNCTION_PROTOTYPE_SIZE_0 EBPF_SIZE_INCLUDING_FIELD(ebpf_helper_function_prototype_t, arguments)
+#define EBPF_HELPER_FUNCTION_PROTOTYPE_SIZE_1 EBPF_SIZE_INCLUDING_FIELD(ebpf_helper_function_prototype_t, flags)
+size_t _ebpf_helper_function_prototype_supported_size[] = {
+    EBPF_HELPER_FUNCTION_PROTOTYPE_SIZE_0, EBPF_HELPER_FUNCTION_PROTOTYPE_SIZE_1};
 
-#define EBPF_PROGRAM_INFO_SIZE_0 \
-    EBPF_OFFSET_OF(ebpf_program_info_t, global_helper_prototype) + sizeof(ebpf_helper_function_prototype_t*)
+#define EBPF_PROGRAM_INFO_SIZE_0 EBPF_SIZE_INCLUDING_FIELD(ebpf_program_info_t, global_helper_prototype)
 size_t _ebpf_program_info_supported_size[] = {EBPF_PROGRAM_INFO_SIZE_0};
 
 #define EBPF_HELPER_FUNCTION_ADDRESSES_SIZE_0 \
@@ -49,7 +49,7 @@ size_t _ebpf_helper_function_addresses_supported_size[] = {EBPF_HELPER_FUNCTION_
 #define EBPF_PROGRAM_DATA_SIZE_0 EBPF_OFFSET_OF(ebpf_program_data_t, required_irql) + sizeof(uint8_t)
 size_t _ebpf_program_data_supported_size[] = {EBPF_PROGRAM_DATA_SIZE_0};
 
-#define EBPF_PROGRAM_SECTION_SIZE_0 EBPF_OFFSET_OF(ebpf_program_section_info_t, bpf_attach_type) + sizeof(uint32_t)
+#define EBPF_PROGRAM_SECTION_SIZE_0 EBPF_SIZE_INCLUDING_FIELD(ebpf_program_section_info_t, bpf_attach_type)
 size_t _ebpf_program_section_supported_size[] = {EBPF_PROGRAM_SECTION_SIZE_0};
 
 struct _ebpf_extension_data_structure_supported_sizes

libs/store_helper/ebpf_store_helper.c

@@ -88,6 +88,16 @@ _ebpf_store_update_helper_prototype(
         goto Exit;
     }
 
+    if (helper_info->header.size >= EBPF_SIZE_INCLUDING_FIELD(ebpf_helper_function_prototype_t, flags)) {
+        // Save the reallocate_packet flag.
+        uint32_t reallocate_packet_value = helper_info->flags.reallocate_packet ? 1 : 0;
+        result = ebpf_write_registry_value_dword(
+            helper_function_key, EBPF_HELPER_DATA_REALLOCATE_PACKET, reallocate_packet_value);
+        if (!IS_SUCCESS(result)) {
+            goto Exit;
+        }
+    }
+
 Exit:
     ebpf_free_wstring(wide_helper_name);
     ebpf_close_registry_key(helper_function_key);

netebpfext/net_ebpf_ext_program_info.h

@@ -9,13 +9,17 @@
 
 #define XDP_EXT_HELPER_FUNCTION_START EBPF_MAX_GENERAL_HELPER_FUNCTION
 
+#define HELPER_FUNCTION_REALLOCATE_PACKET TRUE
+
 // XDP_TEST helper function prototype descriptors.
 static const ebpf_helper_function_prototype_t _xdp_test_ebpf_extension_helper_function_prototype[] = {
     {{EBPF_HELPER_FUNCTION_PROTOTYPE_CURRENT_VERSION, EBPF_HELPER_FUNCTION_PROTOTYPE_CURRENT_VERSION_SIZE},
      XDP_EXT_HELPER_FUNCTION_START + 1,
      "bpf_xdp_adjust_head",
      EBPF_RETURN_TYPE_INTEGER,
-     {EBPF_ARGUMENT_TYPE_PTR_TO_CTX, EBPF_ARGUMENT_TYPE_ANYTHING}}};
+     {EBPF_ARGUMENT_TYPE_PTR_TO_CTX, EBPF_ARGUMENT_TYPE_ANYTHING},
+     // Flags.
+     {HELPER_FUNCTION_REALLOCATE_PACKET}}};
 
 // XDP_TEST program information.
 static const ebpf_context_descriptor_t _ebpf_xdp_test_context_descriptor = {

scripts/config_test_vm.psm1

@@ -600,7 +600,7 @@ function Get-RegressionTestArtifacts
 
     # Download regression test artifacts for each version.
     $DownloadPath = "$RegressionTestArtifactsPath"
-    $ArtifactName = "Release-v$ArtifactVersion/Build-x64.$Configuration.zip"
+    $ArtifactName = "Release-v$ArtifactVersion/Build-x64-$Configuration.zip"
     $ArtifactUrl = "https://github.com/microsoft/ebpf-for-windows/releases/download/" + $ArtifactName
 
     Write-Log "Downloading regression test artifacts for version $ArtifactVersion" -ForegroundColor Green

tests/end_to_end/netsh_test.cpp

@@ -355,6 +355,29 @@ TEST_CASE("show verification droppacket.o", "[netsh][verification]")
                   "Program terminates within 0 loop iterations\n");
 }
 
+TEST_CASE("show verification xdp_adjust_head_unsafe.o", "[netsh][verification]")
+{
+    _test_helper_netsh test_helper;
+    test_helper.initialize();
+
+    int result;
+    std::string output =
+        _run_netsh_command(handle_ebpf_show_verification, L"xdp_adjust_head_unsafe.o", L"xdp", nullptr, &result);
+    REQUIRE(result == ERROR_SUPPRESS_OUTPUT);
+    output = strip_paths(output);
+    REQUIRE(
+        output == "Verification failed\n"
+                  "\n"
+                  "Verification report:\n"
+                  "\n"
+                  "; ./tests/sample/unsafe/xdp_adjust_head_unsafe.c:42\n"
+                  ";     ethernet_header->Type = 0x0800;\n"
+                  "17: Upper bound must be at most packet_size (valid_access(r1.offset+12, width=2) for write)\n"
+                  "\n"
+                  "1 errors\n"
+                  "\n");
+}
+
 TEST_CASE("show verification droppacket_unsafe.o", "[netsh][verification]")
 {
     _test_helper_netsh test_helper;

tests/sample/unsafe/xdp_adjust_head_unsafe.c

@@ -0,0 +1,46 @@
+// Copyright (c) Microsoft Corporation
+// SPDX-License-Identifier: MIT
+
+// clang -O2 -Werror -c xdp_adjust_head_unsafe.c -o xdp_adjust_head_unsafe_jit.o
+//
+// For bpf code: clang -target bpf -O2 -Werror -c xdp_adjust_head_unsafe.c -o xdp_adjust_head_unsafe.o
+//
+
+#include "bpf_endian.h"
+#include "bpf_helpers.h"
+#include "net/if_ether.h"
+#include "net/ip.h"
+#include "net/udp.h"
+
+SEC("xdp")
+int
+xdp_adjust_head_unsafe(xdp_md_t* ctx)
+{
+    int rc = XDP_PASS;
+
+    ETHERNET_HEADER* ethernet_header = NULL;
+    char* next_header = (char*)ctx->data;
+
+    // Access the Ethernet header fields after checking for safety.
+    // This will pass verifier test.
+    if (next_header + sizeof(ETHERNET_HEADER) > (char*)ctx->data_end) {
+        rc = XDP_DROP;
+        goto Done;
+    }
+    ethernet_header = (ETHERNET_HEADER*)next_header;
+    ethernet_header->Type = 0x0800;
+
+    // Adjust the head of the packet by removing the Ethernet header.
+    if (bpf_xdp_adjust_head(ctx, sizeof(ETHERNET_HEADER)) < 0) {
+        rc = XDP_DROP;
+        goto Done;
+    }
+
+    // Access the packet without checking for safety.
+    // This will fail verifier test.
+    ethernet_header = (ETHERNET_HEADER*)ctx->data;
+    ethernet_header->Type = 0x0800;
+
+Done:
+    return rc;
+}

tools/bpf2c/bpf2c.cpp

@@ -116,6 +116,12 @@ get_program_info_type_hash(const std::vector<int32_t>& actual_helper_ids, const
                 hash_t::append_byte_range(
                     byte_range, program_info->program_type_specific_helper_prototype[index].arguments[argument]);
             }
+            // This check for flags is temporary, until https://github.com/microsoft/ebpf-for-windows/issues/3429 is
+            // fixed.
+            if (program_info->program_type_specific_helper_prototype[index].flags.reallocate_packet != 0) {
+                hash_t::append_byte_range(
+                    byte_range, program_info->program_type_specific_helper_prototype[index].flags);
+            }
         }
     }
     hash_t hash(algorithm);

tools/bpf2c/bpf2c.vcxproj

@@ -108,7 +108,7 @@
     </ClCompile>
     <Link>
       <SubSystem>Console</SubSystem>
-      <GenerateDebugInformation>true</GenerateDebugInformation>
+      <GenerateDebugInformation>DebugFull</GenerateDebugInformation>
       <AdditionalDependencies>$(FuzzerLibs);%(AdditionalDependencies)</AdditionalDependencies>
     </Link>
     <PreBuildEvent>
@@ -126,7 +126,7 @@
     </ClCompile>
     <Link>
       <SubSystem>Console</SubSystem>
-      <GenerateDebugInformation>true</GenerateDebugInformation>
+      <GenerateDebugInformation>DebugFull</GenerateDebugInformation>
       <AdditionalDependencies>$(FuzzerLibs);%(AdditionalDependencies)</AdditionalDependencies>
     </Link>
     <PreBuildEvent>
@@ -141,7 +141,7 @@
     </ClCompile>
     <Link>
       <SubSystem>Console</SubSystem>
-      <GenerateDebugInformation>true</GenerateDebugInformation>
+      <GenerateDebugInformation>DebugFull</GenerateDebugInformation>
       <AdditionalDependencies>$(FuzzerLibs);%(AdditionalDependencies)</AdditionalDependencies>
     </Link>
     <PreBuildEvent>
@@ -159,7 +159,7 @@
       <SubSystem>Console</SubSystem>
       <EnableCOMDATFolding>true</EnableCOMDATFolding>
       <OptimizeReferences>true</OptimizeReferences>
-      <GenerateDebugInformation>true</GenerateDebugInformation>
+      <GenerateDebugInformation>DebugFull</GenerateDebugInformation>
       <AdditionalDependencies>$(FuzzerLibs);%(AdditionalDependencies)</AdditionalDependencies>
     </Link>
     <PreBuildEvent>
@@ -177,7 +177,7 @@
       <SubSystem>Console</SubSystem>
       <EnableCOMDATFolding>true</EnableCOMDATFolding>
       <OptimizeReferences>true</OptimizeReferences>
-      <GenerateDebugInformation>true</GenerateDebugInformation>
+      <GenerateDebugInformation>DebugFull</GenerateDebugInformation>
       <AdditionalDependencies>$(FuzzerLibs);%(AdditionalDependencies)</AdditionalDependencies>
     </Link>
     <PreBuildEvent>