Add TUN device setup for agent and switch

.gitignore

@@ -3,3 +3,4 @@ build
 .DS_Store
 .idea
 compile_commands.json
+config/

CMakeLists.txt

@@ -41,6 +41,8 @@ include_directories(${ProtobufIncludePath})
 
 SET(VNET_SOURCE_FILES
         src/common/socket_utils.cpp
+        src/common/tun.cpp
+
         src/protocol/header.cpp
         src/protocol/types.cpp
         src/protocol/dispatch.cpp
@@ -72,11 +74,14 @@ add_subdirectory(src/agent)
 ######################## GOOGLE TEST ########################
 #############################################################
 
-include(FetchContent)
-FetchContent_Declare(
-    googletest
-    URL https://github.com/google/googletest/archive/refs/tags/v1.17.0.zip
-)
-FetchContent_MakeAvailable(googletest)
+find_package(GTest QUIET)
+if (NOT GTest_FOUND)
+    include(FetchContent)
+    FetchContent_Declare(
+        googletest
+        URL https://github.com/google/googletest/archive/refs/tags/v1.17.0.zip
+    )
+    FetchContent_MakeAvailable(googletest)
+endif()
 enable_testing()
 add_subdirectory(tests)

docker/Dockerfile.agent

@@ -5,6 +5,8 @@ RUN apt-get update && apt-get install -y \
     cmake \
     protobuf-compiler \
     libprotobuf-dev \
+    libgtest-dev \
+    libgmock-dev \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app
@@ -16,7 +18,7 @@ RUN cmake -S . -B build -DCMAKE_BUILD_TYPE=Release && \
 FROM ubuntu:24.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    libprotobuf32t64 bash \
+    libprotobuf32t64 bash iproute2 \
     && rm -rf /var/lib/apt/lists/*
 
 COPY --from=builder /app/build/agent /usr/local/bin/agent

docker/Dockerfile.conductor

@@ -5,6 +5,8 @@ RUN apt-get update && apt-get install -y \
     cmake \
     protobuf-compiler \
     libprotobuf-dev \
+    libgtest-dev \
+    libgmock-dev \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app

docker/Dockerfile.switch

@@ -5,6 +5,8 @@ RUN apt-get update && apt-get install -y \
     cmake \
     protobuf-compiler \
     libprotobuf-dev \
+    libgtest-dev \
+    libgmock-dev \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app
@@ -16,9 +18,12 @@ RUN cmake -S . -B build -DCMAKE_BUILD_TYPE=Release && \
 FROM ubuntu:24.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    libprotobuf32t64 bash \
+    libprotobuf32t64 bash iproute2 \
     && rm -rf /var/lib/apt/lists/*
 
 COPY --from=builder /app/build/switch /usr/local/bin/switch
+COPY docker/switch-entrypoint.sh /usr/local/bin/switch-entrypoint.sh
+RUN chmod +x /usr/local/bin/switch-entrypoint.sh
 
+ENTRYPOINT [ "/usr/local/bin/switch-entrypoint.sh" ]
 CMD ["/usr/local/bin/switch"]

docker/docker-compose.yml

@@ -30,6 +30,13 @@ services:
     environment:
       - CONDUCTOR_IP=vnet-conductor
       - CONDUCTOR_PORT=5000
+      - VNET_CONFIG_PATH=/etc/vnet/config.txt
+    volumes:
+      - ../config/switch1.txt:/etc/vnet/config.txt:ro
+    cap_add:
+      - NET_ADMIN
+    devices:
+      - /dev/net/tun:/dev/net/tun
     command: ["/usr/local/bin/switch", "switch1", "authkey1", "6000"]
     healthcheck:
       test: ["CMD", "bash", "-c", "timeout 1 bash -c 'echo > /dev/tcp/127.0.0.1/6000' || exit 1"]
@@ -55,6 +62,13 @@ services:
     environment:
       - CONDUCTOR_IP=vnet-conductor
       - CONDUCTOR_PORT=5000
+      - VNET_CONFIG_PATH=/etc/vnet/config.txt
+    volumes:
+      - ../config/switch2.txt:/etc/vnet/config.txt:ro
+    cap_add:
+      - NET_ADMIN
+    devices:
+      - /dev/net/tun:/dev/net/tun
     command: ["/usr/local/bin/switch", "switch2", "authkey2", "6001"]
     healthcheck:
       test: ["CMD", "bash", "-c", "timeout 1 bash -c 'echo > /dev/tcp/127.0.0.1/6001' || exit 1"]
@@ -80,6 +94,13 @@ services:
     environment:
       - CONDUCTOR_IP=vnet-conductor
       - CONDUCTOR_PORT=5000
+      - VNET_CONFIG_PATH=/etc/vnet/config.txt
+    volumes:
+      - ../config/switch3.txt:/etc/vnet/config.txt:ro
+    cap_add:
+      - NET_ADMIN
+    devices:
+      - /dev/net/tun:/dev/net/tun
     command: ["/usr/local/bin/switch", "switch3", "authkey3", "6002"]
     healthcheck:
       test: ["CMD", "bash", "-c", "timeout 1 bash -c 'echo > /dev/tcp/127.0.0.1/6002' || exit 1"]
@@ -109,6 +130,10 @@ services:
     environment:
       - CONDUCTOR_IP=vnet-conductor
       - CONDUCTOR_PORT=5000
+    cap_add:
+      - NET_ADMIN
+    devices:
+      - /dev/net/tun:/dev/net/tun
     command: ["/usr/local/bin/agent", "agent1", "agentkey1"]
     logging:
       driver: "json-file"

docker/switch-entrypoint.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+set -e
+
+if [ ! -f "${VNET_CONFIG_PATH:-/etc/vnet/config.txt}" ]; then
+    echo "[Switch] ERROR: config file not found or is a directory: ${VNET_CONFIG_PATH:-/etc/vnet/config.txt}"
+    exit 1
+fi
+
+exec "$@"

include/common/tun.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <string>
+#include <cstdint>
+
+/**
+ * @brief Open a TUN device and configure it.
+ *
+ * Creates a TUN interface with the given name, assigns the given
+ * IPv4 address with a /24 prefix, and brings the interface up.
+ *
+ * @param name          Interface name (e.g. "vnet0"). Max 15 chars.
+ * @param ipv4          Virtual IPv4 address in network order.
+ * @param prefix_len    Subnet prefix length (default 24 = /24).
+ * @return              File descriptor for the TUN device, or -1 on failure.
+ */
+int tun_open(const std::string& name, uint32_t ipv4, uint8_t prefix_len = 24);
+
+/**
+ * @brief Close a TUN device and bring the interface down.
+ */
+void tun_close(int fd, const std::string& name);

include/vnet/protocol/dispatch.hpp

@@ -26,6 +26,11 @@ namespace vnet::protocol {
         /** Reconnection */
         virtual void onAgentMRP (netqueue::socket_data data, mip::PacketAgentMRP &packet);
 
+        /** Routing */
+        virtual void onPrepareRouteForTarget(netqueue::socket_data data, mip::PacketPrepareRouteForTarget &packet);
+        virtual void onNextForTarget(netqueue::socket_data data, mip::PacketNextForTarget &packet);
+        virtual void onIPv4Raw(netqueue::socket_data data, mip::PacketIPv4Raw &packet);
+
         virtual ~Dispatch() = default;
     };
 

include/vnet/protocol/types.hpp

@@ -8,6 +8,7 @@ namespace vnet::protocol {
     enum PacketType : uint16_t {
         HEARTBEAT = 0,
 
+        // MIP
         SWITCH_MIP,
         AGENT_MIP,
 
@@ -16,7 +17,13 @@ namespace vnet::protocol {
         AUTH_CONNECT_TO_SWITCH,
         CONNECTION_ACCEPTED,
 
-        AGENT_MRP
+        // Reconnection
+        AGENT_MRP,
+
+        // Routing
+        PREPARE_ROUTE_FOR_TARGET,
+        NEXT_FOR_TARGET,
+        IPV4_RAW
     };
 
     PacketType    ntoh_packet_type (uint_packet_t type);

proto/mip.proto

@@ -34,9 +34,29 @@ message PacketAuthConnectToSwitch {
     fixed64 connection_token = 1;
 }
 
-message PacketConnectionAccepted {}
+message PacketConnectionAccepted {
+    fixed32 virtual_ipv4 = 1;
+}
 
 message PacketAgentMRP {
     string name     = 1;
     string auth_key = 2;
 }
+
+message PacketPrepareRouteForTarget {
+    fixed32 dest_ipv4 = 1;
+}
+
+message PacketNextForTarget {
+    fixed32 dest_ipv4       = 1;
+
+    // next_switch_ipv4 = 0 means the target disconnected, remove the route
+    fixed32 next_switch_ipv4 = 2;
+
+    uint32  next_switch_port = 3;
+    string  next_switch_name = 4;
+}
+
+message PacketIPv4Raw {
+    bytes payload = 1;
+}

src/agent/setup.cpp

@@ -10,6 +10,7 @@
 #include <netinet/tcp.h>
 #include <unistd.h>
 
+#include "common/tun.h"
 #include "mip.pb.h"
 #include "common/config.h"
 #include "common/socket_utils.h"
@@ -206,11 +207,25 @@ int main(int argc, char** argv) {
         return 1;
     }
 
-    std::cout << "[Agent] Authenticated with switch "
-              << assignment.switch_name() << "!\n";
+    uint32_t virtual_ipv4 = ack.virtual_ipv4();
+    std::cout << "[Agent] Authenticated with switch " << assignment.switch_name()
+          << ", virtual IP: " << ipv4_to_string(virtual_ipv4) << "\n";
 
     // ===================================================================
-    //  STEP 4 — Switch both fds to non-blocking, enter event loop
+    //  STEP 4 — Open TUN device with assigned virtual IP
+    // ===================================================================
+
+    std::string tun_name = "vnet-" + agent_name;
+    int tun_fd = tun_open(tun_name, virtual_ipv4);
+    if (tun_fd < 0) {
+        std::cerr << "[Agent] Failed to open TUN device\n";
+        close(sw_sock);
+        close(cdt_sock);
+        return 1;
+    }
+
+    // ===================================================================
+    //  STEP 5 — Switch both fds to non-blocking, enter event loop
     // ===================================================================
     set_nonblocking(cdt_sock);
     set_nonblocking(sw_sock);
@@ -235,6 +250,8 @@ int main(int argc, char** argv) {
     g_state.sw = sw_info;
     queue.put_sck(sw_sock, sw_info);
 
+    queue.put_tun(tun_fd, nullptr);
+
     std::cout << "[Agent] Entering event loop.\n";
 
     while (g_running) {
@@ -243,6 +260,7 @@ int main(int argc, char** argv) {
     }
 
     std::cout << "[Agent] Shutting down.\n";
+    tun_close(tun_fd, tun_name);
     google::protobuf::ShutdownProtobufLibrary();
     return 0;
 }