feat(sniffer): implement packet sniffer with IP masking and protocol logging

Captures network packets, extracts source/destination IPs, protocol type, and
ports. Masks IPs when enabled and logs details with protocol information.

src/core/sniffer.cpp

@@ -0,0 +1,135 @@
+#include "sniffer.hpp"
+#include "logger.hpp"
+#include <tins/tins.h>
+
+Sniffer::Sniffer(std::string localIp, bool maskIp)
+    : ip_(std::move(localIp))
+    , mask_(maskIp)
+{
+}
+
+int Sniffer::run()
+{
+    const auto ifaceName = resolveIfaceNameByIp(ip_);
+
+    Tins::SnifferConfiguration cfg;
+    cfg.set_promisc_mode(true);
+    cfg.set_immediate_mode(true);
+
+    Tins::Sniffer sniffer(ifaceName, cfg);
+
+    auto running = [this] { return !stop_.load(std::memory_order_relaxed); };
+
+    auto handler = [&](Tins::PDU &pdu) -> bool {
+        if (!running())
+            return false;
+
+        std::string src, dst;
+        const char *type = "OTHER";
+        uint16_t sport = 0, dport = 0;
+
+        if (auto *arp = pdu.find_pdu<Tins::ARP>()) {
+            src = arp->sender_ip_addr().to_string();
+            dst = arp->target_ip_addr().to_string();
+            type = "ARP";
+        } else if (auto *ip4 = pdu.find_pdu<Tins::IP>()) {
+            src = ip4->src_addr().to_string();
+            dst = ip4->dst_addr().to_string();
+
+            if (auto *tcp = pdu.find_pdu<Tins::TCP>()) {
+                type = "TCP";
+                sport = tcp->sport();
+                dport = tcp->dport();
+            } else if (auto *udp = pdu.find_pdu<Tins::UDP>()) {
+                type = "UDP";
+                sport = udp->sport();
+                dport = udp->dport();
+            } else if (pdu.find_pdu<Tins::ICMP>()) {
+                type = "ICMP";
+            } else {
+                type = "IP";
+            }
+        } else if (auto *ip6 = pdu.find_pdu<Tins::IPv6>()) {
+            src = ip6->src_addr().to_string();
+            dst = ip6->dst_addr().to_string();
+
+            if (auto *tcp = pdu.find_pdu<Tins::TCP>()) {
+                type = "TCP";
+                sport = tcp->sport();
+                dport = tcp->dport();
+            } else if (auto *udp = pdu.find_pdu<Tins::UDP>()) {
+                type = "UDP";
+                sport = udp->sport();
+                dport = udp->dport();
+            } else if (pdu.find_pdu<Tins::ICMPv6>()) {
+                type = "ICMPv6";
+            } else {
+                type = "IPv6";
+            }
+        } else {
+            Logger::info("(unknown src) -> (unknown dst) [OTHER]");
+            return running();
+        }
+
+        if (mask_) {
+            src = hideHalf(src);
+            dst = hideHalf(dst);
+        }
+
+        printLine(src, dst, type, sport, dport);
+        return running();
+    };
+
+    sniffer.sniff_loop(handler);
+    return 0;
+}
+
+void Sniffer::stop()
+{
+    stop_.store(true, std::memory_order_relaxed);
+}
+
+std::string Sniffer::hideHalf(const std::string &s) const
+{
+    if (s.empty()) {
+        return s;
+    }
+
+    const size_t n = s.size();
+    const size_t hide = n / 2;
+    const size_t keep = n - hide;
+    std::string out = s.substr(0, keep);
+    out.append(hide, '*');
+
+    return out;
+}
+
+std::string Sniffer::resolveIfaceNameByIp(const std::string &ip)
+{
+    const Tins::IPv4Address want(ip);
+    for (const auto &iface : Tins::NetworkInterface::all()) {
+        const auto info = iface.addresses(); // .ip_addr/.netmask/...
+        if (info.ip_addr == want) {
+            return iface.name();
+        }
+    }
+    throw std::runtime_error("Interface with IP " + ip + " not found");
+}
+
+void Sniffer::printLine(
+    const std::string &src,
+    const std::string &dst,
+    const char *type,
+    uint16_t sport,
+    uint16_t dport
+)
+{
+    if (sport || dport) {
+        Logger::info(
+            std::string(src) + ":" + std::to_string(sport) + " -> " + dst + ":"
+            + std::to_string(dport) + " [" + type + "]"
+        );
+    } else {
+        Logger::info(std::string(src) + " -> " + dst + " [" + type + "]");
+    }
+}

src/core/sniffer.hpp

@@ -0,0 +1,32 @@
+#pragma once
+#include <atomic>
+#include <cstdint>
+#include <string>
+
+class Sniffer
+{
+  public:
+    explicit Sniffer(std::string localIp, bool maskIp = false);
+
+    Sniffer(const Sniffer &) = delete;
+    Sniffer &operator=(const Sniffer &) = delete;
+
+    std::string hideHalf(const std::string &s) const;
+
+    int run();
+    void stop();
+
+  private:
+    static std::string resolveIfaceNameByIp(const std::string &ip);
+    static void printLine(
+        const std::string &src,
+        const std::string &dst,
+        const char *type,
+        uint16_t sport = 0,
+        uint16_t dport = 0
+    );
+
+    std::string ip_;
+    std::atomic<bool> stop_{false};
+    bool mask_{false};
+};