WIP: MPTCP and ID-INT

SCION-CPP:
* Parse and emit MPTCP options
* Improve handling of TCP
* Improve checksum update
* Add ID-INT client API and tests

Scitra-TUN:
* Add support for MPTCP
* mptcpd connector (WIP)
* Add --daemon option

Applications:
* idint-traceroute port from Go (WIP)

Author: lschulz

.gitmodules

@@ -16,3 +16,6 @@
 [submodule "deps/spdlog"]
 	path = deps/spdlog
 	url = https://github.com/gabime/spdlog.git
+[submodule "deps/mptcpd"]
+	path = deps/mptcpd
+	url = https://github.com/multipath-tcp/mptcpd.git

.vscode/c_cpp_properties.json

@@ -12,6 +12,7 @@
                 "${workspaceFolder}/deps/imtui/include",
                 "${workspaceFolder}/deps/imtui/third-party/imgui",
                 "${workspaceFolder}/deps/spdlog/include",
+                "${workspaceFolder}/deps/mptcpd/include",
                 "${workspaceFolder}/examples/c/include",
                 "${workspaceFolder}/examples/include",
                 "${workspaceFolder}/include",

.vscode/settings.json

@@ -153,10 +153,15 @@
     "C_Cpp.default.cppStandard": "c++23",
     "C_Cpp.default.cStandard": "c17",
     "cSpell.words": [
+        "demultiplex",
         "drkey",
+        "MPTCP",
+        "mptcpd",
         "pmtu",
         "recvmmsg",
         "sendmmsg",
+        "subflow",
+        "subflows",
         "urgptr"
     ],
     "python.analysis.extraPaths": [

CMakeLists.txt

@@ -199,9 +199,12 @@ target_sources(scion-cpp
         "src/addr/generic_ip.cpp"
         "src/addr/isd_asn.cpp"
         "src/bit_stream.cpp"
+        "src/crypto/aes.cpp"
         "src/daemon/client.cpp"
         "src/default_address.cpp"
+        "src/detect_cpu.cpp"
         "src/error_codes.cpp"
+        "src/extensions/idint.cpp"
         "src/hdr/details.cpp"
         "src/murmur_hash3.cpp"
         "src/path/path_meta.cpp"
@@ -223,6 +226,7 @@ target_sources(scion-cpp
         "include/scion/asio/scmp_socket.hpp"
         "include/scion/asio/udp_socket.hpp"
         "include/scion/bit_stream.hpp"
+        "include/scion/crypto/aes.hpp"
         "include/scion/daemon/client.hpp"
         "include/scion/daemon/co_client.hpp"
         "include/scion/details/bit.hpp"
@@ -231,9 +235,13 @@ target_sources(scion-cpp
         "include/scion/details/flags.hpp"
         "include/scion/details/from_chars.hpp"
         "include/scion/details/protobuf_time.hpp"
+        "include/scion/detect_cpu.hpp"
         "include/scion/drkey/drkey.hpp"
+        "include/scion/drkey/key_cache.hpp"
         "include/scion/error_codes.hpp"
         "include/scion/extensions/extension.hpp"
+        "include/scion/extensions/idint_instr.hpp"
+        "include/scion/extensions/idint.hpp"
         "include/scion/extensions/idint.hpp"
         "include/scion/hdr/details.hpp"
         "include/scion/hdr/ethernet.hpp"
@@ -364,6 +372,9 @@ set(SRC_TEST
     "tests/asio/test_addresses.cpp"
     "tests/asio/test_scmp_socket.cpp"
     "tests/asio/test_udp_socket.cpp"
+    "tests/crypto/test_aes.cpp"
+    "tests/drkey/test_key_cache.cpp"
+    "tests/extensions/test_idint_api.cpp"
     "tests/hdr/test_checksum.cpp"
     "tests/hdr/test_idint.cpp"
     "tests/hdr/test_ip.cpp"
@@ -418,6 +429,12 @@ endif()
 
 add_subdirectory(scitra)
 
+# ============
+# Applications
+# ============
+
+add_subdirectory(applications/idint-traceroute)
+
 # ========
 # Examples
 # ========

Doxyfile

@@ -48,7 +48,7 @@ PROJECT_NAME           = "SCION-CPP"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = "0.0.4"
+PROJECT_NUMBER         = "0.0.5"
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a

Makefile

@@ -7,7 +7,7 @@ BUILD_DIR := $(SRC_ROOT)/build
 PKG_DIR := $(SRC_ROOT)/out
 PYTHONPATH := $(PYTHONPATH):$(SRC_ROOT)/python
 
-DOCKER_TAG := 0.0.4
+DOCKER_TAG := 0.0.5
 HOST_UID := $(shell id -u):$(shell id -g)
 
 TEST_DATA=$(addsuffix .bin,$(basename $(shell find tests scitra/tests -name '*.py')))

README.md

@@ -40,6 +40,7 @@ with SCION-aware wrappers.
   - [Scitra-TUN](scitra/docs/scitra-tun.md) A SCION-IP translator using TUN interfaces on Linux.
 - [SCION API Interposers](interposer/): Deep SCION integration without touching application code.
     Currently only available for glibc in Linux-like environments.
+- [ID-INT Traceroute](applications/idint-traceroute/): TODO
 
 ### Documentation ###
 API documentation is generated with Doxygen.
@@ -133,6 +134,7 @@ test .............. scion++ and scionc unit tests
 For scitra-tun (Linux only):
 - libmnl >= 1.0.5
 - libcap >= 3.1.3
+- libsystemd-dev >= 255.4
 - [ImTui](https://github.com/ggerganov/imtui) (included as submodule)
 - [spdlog](https://github.com/gabime/spdlog) (included as submodule)
 
@@ -144,7 +146,8 @@ Most dependencies can be built and installed with vcpkg:
 ```bash
 vcpkg install
 ```
-In Linux, `libmnl` and `libcap` must be installed using the system's package manager.
+In Linux, `libmnl`, `libcap`, and `libsystemd-dev` must be installed using the system's package
+manager.
 
 All required build tools and dependencies can also be installed with apt (Ubuntu 24.04).
 ```bash

applications/README.md

@@ -0,0 +1,8 @@
+cmake_minimum_required(VERSION 3.28)
+
+set(IDINT_TRACEROUTE_SRC
+    "main.cpp"
+    "tables.cpp"
+)
+add_executable(idint-traceroute ${IDINT_TRACEROUTE_SRC})
+target_link_libraries(idint-traceroute PRIVATE scion-cpp CLI11::CLI11)

applications/idint-traceroute/CMakeLists.txt

@@ -0,0 +1,61 @@
+// Copyright (c) 2026 Lars-Christian Schulz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#include <scion/scion.hpp>
+
+#include <string>
+
+
+struct ServerCfg
+{
+    bool verbose = false;
+};
+
+struct ClientCfg
+{
+    scion::ScIPEndpoint remote;
+    float timeout = 1.0f;
+    float period = 1.0f;
+    std::uint8_t skip = 0;
+    unsigned limit = 0;
+    int path = -1;
+    scion::idint::Instr instrs[4] = {};
+    scion::idint::AM agrMode = scion::idint::AM::Off;
+    scion::idint::AF agrFuncs[4] = {};
+    bool stun = false;
+    bool reqNodeId = false;
+    bool reqNodeCnt = false;
+    bool reqIgr = false;
+    bool reqEgr = false;
+    bool noVerify = false;
+    bool encrypt = false;
+    bool tui = false;
+};
+
+struct Config
+{
+    std::string sciond = "127.0.0.1:30255";
+    scion::generic::IPEndpoint local;
+    bool serverMode = false;
+    ServerCfg server;
+    ClientCfg client;
+};