Increase MAX_TAIL_CALL_CNT to 33 tail calls

include/bpf_helpers.h

@@ -26,5 +26,3 @@
 #endif
 
 #include "bpf_helper_defs.h"
-
-#define MAX_TAIL_CALL_CNT 32

include/ebpf_structs.h

@@ -20,6 +20,8 @@ typedef unsigned int uint32_t;
 typedef unsigned long long uint64_t;
 #endif
 
+#define MAX_TAIL_CALL_CNT 33
+
 #define BPF_ENUM_TO_STRING(X) #X
 
 typedef enum bpf_map_type

installer/Product.wxs

@@ -994,6 +994,18 @@ SPDX-License-Identifier: MIT
 			<Component Id="TAIL_CALL_MULTIPLE_UM.PDB" DiskId="1" Guid="{D918F2DB-BC80-406F-B0AD-0C340D5EF280}">
 				<File Id="TAIL_CALL_MULTIPLE_UM.PDB" Name="tail_call_multiple_um.pdb" Source="$(var.SolutionDir)$(var.Platform)\$(var.Configuration)\tail_call_multiple_um.pdb" />
 			</Component>
+			<Component Id="TAIL_CALL_MAX_EXCEED.O" DiskId="1" Guid="{A3E840BD-B510-4F02-80A6-1EA0553C6746}">
+				<File Id="TAIL_CALL_MAX_EXCEED.O" Name="tail_call_max_exceed.o" Source="$(var.SolutionDir)$(var.Platform)\$(var.Configuration)\tail_call_recursive.o" />
+			</Component>
+			<Component Id="TAIL_CALL_MAX_EXCEED.SYS" DiskId="1" Guid="{D3EE01E4-8258-46D4-89FA-C207960C90E6}">
+				<File Id="TAIL_CALL_MAX_EXCEED.SYS" Name="tail_call_max_exceed.sys" Source="$(var.SolutionDir)$(var.Platform)\$(var.Configuration)\tail_call_recursive.sys" />
+			</Component>
+			<Component Id="TAIL_CALL_MAX_EXCEED_UM.DLL" DiskId="1" Guid="{916F7BF5-6B8A-4C99-A09F-102CBB404AA5}">
+				<File Id="TAIL_CALL_MAX_EXCEED_UM.DLL" Name="tail_call_max_exceed_um.dll" Source="$(var.SolutionDir)$(var.Platform)\$(var.Configuration)\tail_call_recursive_um.dll" />
+			</Component>
+			<Component Id="TAIL_CALL_MAX_EXCEED_UM.PDB" DiskId="1" Guid="{9A1BFAAD-D94F-4805-842F-B8DB77B6FC6C}">
+				<File Id="TAIL_CALL_MAX_EXCEED_UM.PDB" Name="tail_call_max_exceed_um.pdb" Source="$(var.SolutionDir)$(var.Platform)\$(var.Configuration)\tail_call_recursive_um.pdb" />
+			</Component>
 			<Component Id="TAIL_CALL_RECURSIVE.O" DiskId="1" Guid="{7469C19C-7706-44B7-BA35-6F27195F311A}">
 				<File Id="TAIL_CALL_RECURSIVE.O" Name="tail_call_recursive.o" Source="$(var.SolutionDir)$(var.Platform)\$(var.Configuration)\tail_call_recursive.o" />
 			</Component>

libs/execution_context/ebpf_program.c

@@ -1348,10 +1348,12 @@ ebpf_program_set_tail_call(_In_ const ebpf_program_t* next_program)
     }
 
     if (state == NULL) {
+        EBPF_LOG_MESSAGE_STRING(
+            EBPF_TRACELOG_LEVEL_ERROR, EBPF_TRACELOG_KEYWORD_PROGRAM, "ebpf tail call state load:", "NULL");
         return EBPF_INVALID_ARGUMENT;
     }
 
-    if (state->tail_call_state.count == (MAX_TAIL_CALL_CNT - 1)) {
+    if (state->tail_call_state.count == (MAX_TAIL_CALL_CNT)) {
         EBPF_OBJECT_RELEASE_REFERENCE(&((ebpf_program_t*)next_program)->object);
         return EBPF_NO_MORE_TAIL_CALLS;
     }
@@ -1389,7 +1391,8 @@ ebpf_program_invoke(
     // High volume call - Skip entry/exit logging.
     const ebpf_program_t* current_program = program;
 
-    for (execution_state->tail_call_state.count = 0; execution_state->tail_call_state.count < MAX_TAIL_CALL_CNT;
+    // Top-level tail caller(1) + tail callees(33).
+    for (execution_state->tail_call_state.count = 0; execution_state->tail_call_state.count < MAX_TAIL_CALL_CNT + 1;
          execution_state->tail_call_state.count++) {
 
         if (current_program->parameters.code_type == EBPF_CODE_JIT ||

scripts/deploy-ebpf.ps1.in

@@ -189,6 +189,10 @@ $source_directory="."
     "tail_call_map_um.dll",
     "tail_call_map_um.pdb",
     "tail_call_map.sys",
+    "tail_call_max_exceed.o",
+    "tail_call_max_exceed_um.dll",
+    "tail_call_max_exceed_um.pdb",
+    "tail_call_max_exceed.sys",
     "tail_call_multiple.o",
     "tail_call_multiple_um.dll",
     "tail_call_multiple_um.pdb",

tests/api_test/api_test.cpp

@@ -714,6 +714,63 @@ TEST_CASE("bindmonitor_tailcall_native_test", "[native_tests]")
     cleanup();
 }
 
+void
+bind_tailcall_test(_In_ struct bpf_object* object)
+{
+    UNREFERENCED_PARAMETER(object);
+    WSAData data;
+    SOCKET sockets[2];
+    REQUIRE(WSAStartup(2, &data) == 0);
+
+    // Now, trigger bind. bind should not succeed.
+    REQUIRE(perform_bind(&sockets[0], 30000) != 0);
+    REQUIRE(perform_bind(&sockets[1], 30001) != 0);
+
+    WSACleanup();
+}
+
+#define MAX_TAIL_CALL_PROGS MAX_TAIL_CALL_CNT + 2
+
+TEST_CASE("bind_tailcall_max_native_test", "[native_tests]")
+{
+    struct bpf_object* object = nullptr;
+    hook_helper_t hook(EBPF_ATTACH_TYPE_BIND);
+
+    program_load_attach_helper_t _helper;
+    _helper.initialize(
+        "tail_call_max_exceed.sys",
+        BPF_PROG_TYPE_BIND,
+        "bind_test_caller",
+        EBPF_EXECUTION_NATIVE,
+        nullptr,
+        0,
+        hook);
+    object = _helper.get_object();
+
+    fd_t prog_map_fd = bpf_object__find_map_fd_by_name(object, "bind_tail_call_map");
+    REQUIRE(prog_map_fd > 0);
+
+    struct bpf_program* caller = bpf_object__find_program_by_name(object, "bind_test_caller");
+    REQUIRE(caller != nullptr);
+
+    // Check each tail call program in the map.
+    for (int i = 0; i < MAX_TAIL_CALL_PROGS; i++) {
+        std::string program_name{"bind_test_callee"};
+        program_name += std::to_string(i);
+
+        struct bpf_program* program = bpf_object__find_program_by_name(object, program_name.c_str());
+        REQUIRE(program != nullptr);
+    }
+
+    // Perform bind test.
+    bind_tailcall_test(object);
+
+    // Clean up tail calls.
+    for (int index = 0; index < MAX_TAIL_CALL_PROGS; index++) {
+        REQUIRE(bpf_map_update_elem(prog_map_fd, &index, &ebpf_fd_invalid, 0) == 0);
+    }
+}
+
 #define SOCKET_TEST_PORT 0x3bbf
 
 TEST_CASE("bpf_get_current_pid_tgid", "[helpers]")

tests/bpf2c_tests/elf_bpf.cpp

@@ -238,6 +238,7 @@ DECLARE_TEST("sockops", _test_mode::Verify)
 DECLARE_TEST("tail_call", _test_mode::Verify)
 DECLARE_TEST("tail_call_bad", _test_mode::Verify)
 DECLARE_TEST("tail_call_map", _test_mode::Verify)
+DECLARE_TEST("tail_call_max_exceed", _test_mode::Verify)
 DECLARE_TEST("tail_call_multiple", _test_mode::Verify)
 DECLARE_TEST("tail_call_recursive", _test_mode::Verify)
 DECLARE_TEST("tail_call_sequential", _test_mode::Verify)