init: icmp traceroute

.github/workflows/ci.yml

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+name: ci
+
+on:
+  push:
+    branches: [master]
+
+jobs:
+  build:
+    runs-on: windows-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ilammy/msvc-dev-cmd@v1
+      - run: cmake -B build
+      - run: cmake --build build --config Release

.gitignore

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+build/
+.claude/
+*.obj
+*.exe
+*.pdb
+*.ilk

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.16)
+project(ttlprobe CXX)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+add_executable(ttlprobe src/main.cpp)
+
+if(WIN32)
+    target_link_libraries(ttlprobe ws2_32)
+endif()

README.md

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+# ttl-probe
+
+свой traceroute на C++ через сырые ICMP-сокеты. шлёт echo-запросы с растущим TTL и смотрит кто отвечает "time exceeded" на каждом хопе.
+
+```mermaid
+sequenceDiagram
+    ttl-probe->>Hop1: ICMP echo, TTL=1
+    Hop1-->>ttl-probe: time exceeded
+    ttl-probe->>Hop2: ICMP echo, TTL=2
+    Hop2-->>ttl-probe: time exceeded
+    ttl-probe->>Target: ICMP echo, TTL=N
+    Target-->>ttl-probe: echo reply (дошли)
+```
+
+изначально планировал сюда честный fake-packet TTL-трюк (как в zapret), но на винде это требует сырых TCP-пакетов, а винда с висты их резать не даёт без отдельного драйвера (WinDivert/Npcap) — это уже не "просто". traceroute зато честно показывает сколько хопов до сервера, полезно прежде чем городить любой TTL-трюк вручную.
+
+## сборка
+
+```
+cmake -B build
+cmake --build build --config Release
+```
+
+## юзать
+
+нужны права администратора (сырые сокеты):
+
+```
+build\Release\ttlprobe.exe example.com 30
+```

src/main.cpp

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+#include <winsock2.h>
+#include <ws2tcpip.h>
+#include <windows.h>
+#include <iostream>
+#include <string>
+#include <vector>
+#include <chrono>
+
+#pragma comment(lib, "ws2_32.lib")
+
+#pragma pack(push, 1)
+struct IcmpHeader {
+    uint8_t type;
+    uint8_t code;
+    uint16_t checksum;
+    uint16_t id;
+    uint16_t seq;
+};
+#pragma pack(pop)
+
+static uint16_t checksum16(const uint8_t* data, size_t len) {
+    uint32_t sum = 0;
+    for (size_t i = 0; i + 1 < len; i += 2) {
+        sum += (static_cast<uint16_t>(data[i]) << 8) | data[i + 1];
+    }
+    if (len % 2 == 1) sum += static_cast<uint16_t>(data[len - 1]) << 8;
+    while (sum >> 16) sum = (sum & 0xFFFF) + (sum >> 16);
+    return static_cast<uint16_t>(~sum);
+}
+
+int main(int argc, char** argv) {
+    if (argc < 2) {
+        std::cerr << "usage: ttlprobe <host> [max-hops]" << std::endl;
+        return 1;
+    }
+    std::string target = argv[1];
+    int max_hops = argc > 2 ? std::stoi(argv[2]) : 30;
+
+    WSADATA wsa;
+    if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0) {
+        std::cerr << "WSAStartup failed" << std::endl;
+        return 1;
+    }
+
+    addrinfo hints{};
+    hints.ai_family = AF_INET;
+    hints.ai_socktype = SOCK_RAW;
+    addrinfo* res = nullptr;
+    if (getaddrinfo(target.c_str(), nullptr, &hints, &res) != 0 || !res) {
+        std::cerr << "cant resolve " << target << std::endl;
+        return 1;
+    }
+    sockaddr_in dest = *reinterpret_cast<sockaddr_in*>(res->ai_addr);
+    freeaddrinfo(res);
+
+    char dest_ip[INET_ADDRSTRLEN];
+    inet_ntop(AF_INET, &dest.sin_addr, dest_ip, sizeof(dest_ip));
+    std::cout << "probing " << target << " (" << dest_ip << "), " << max_hops << " hops max" << std::endl;
+
+    SOCKET sock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
+    if (sock == INVALID_SOCKET) {
+        std::cerr << "raw socket failed, run as administrator" << std::endl;
+        WSACleanup();
+        return 1;
+    }
+
+    DWORD timeout = 1500;
+    setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, reinterpret_cast<const char*>(&timeout), sizeof(timeout));
+
+    for (int ttl = 1; ttl <= max_hops; ++ttl) {
+        setsockopt(sock, IPPROTO_IP, IP_TTL, reinterpret_cast<const char*>(&ttl), sizeof(ttl));
+
+        uint8_t packet[64] = {};
+        IcmpHeader* icmp = reinterpret_cast<IcmpHeader*>(packet);
+        icmp->type = 8;
+        icmp->code = 0;
+        icmp->id = static_cast<uint16_t>(GetCurrentProcessId());
+        icmp->seq = static_cast<uint16_t>(ttl);
+        icmp->checksum = 0;
+        icmp->checksum = htons(checksum16(packet, sizeof(packet)));
+
+        auto start = std::chrono::steady_clock::now();
+        sendto(sock, reinterpret_cast<char*>(packet), sizeof(packet), 0,
+            reinterpret_cast<sockaddr*>(&dest), sizeof(dest));
+
+        uint8_t reply[512];
+        sockaddr_in from{};
+        int from_len = sizeof(from);
+        int n = recvfrom(sock, reinterpret_cast<char*>(reply), sizeof(reply), 0,
+            reinterpret_cast<sockaddr*>(&from), &from_len);
+
+        auto end = std::chrono::steady_clock::now();
+        double ms = std::chrono::duration<double, std::milli>(end - start).count();
+
+        std::cout << ttl << "\t";
+        if (n <= 0) {
+            std::cout << "*" << std::endl;
+            continue;
+        }
+
+        char from_ip[INET_ADDRSTRLEN];
+        inet_ntop(AF_INET, &from.sin_addr, from_ip, sizeof(from_ip));
+        std::cout << from_ip << "\t" << ms << " ms" << std::endl;
+
+        int ip_header_len = (reply[0] & 0x0F) * 4;
+        if (n > ip_header_len) {
+            uint8_t icmp_type = reply[ip_header_len];
+            if (icmp_type == 0 || from.sin_addr.S_un.S_addr == dest.sin_addr.S_un.S_addr) {
+                std::cout << "reached destination" << std::endl;
+                break;
+            }
+        }
+    }
+
+    closesocket(sock);
+    WSACleanup();
+    return 0;
+}