From 08332a4195956611db80a2cfe3710d760cbd6acf Mon Sep 17 00:00:00 2001 From: srdusr <99972264+srdusr@users.noreply.github.com> Date: Tue, 14 May 2024 01:42:00 +0200 Subject: Initial commit: wireframe packet capture/analysis tool Terminal packet capture and analysis tool built to learn the C++ memory model (byte layout, alignment, endianness, std::span over unowned buffers) via a real capture pipeline. - Hand-rolled L2-L4 decoders (Ethernet, IPv4, IPv6 with extension header walking, TCP, UDP) over std::span, no struct-casting - L7 dissector interface with DNS, HTTP, and TLS SNI implementations - pcapng read/write for Wireshark-compatible capture files - Bounded capture queue: drop-on-backpressure for live capture, blocking push for faithful file replay - Kernel-level BPF filtering (-f) and a separate display-only search (-g / interactive) that doesn't touch what's captured - Replay mode (-r) reads a saved pcapng file back through the same pipeline as live capture, no root or live device needed - pcap_stats() surfaces kernel/interface drops invisible to the capture queue's own counter - Three frontends sharing one CaptureSession setup path: CLI, TUI (FTXUI, primary), GUI (Dear ImGui + SDL3, secondary) - 89 unit tests (doctest) plus 9 libFuzzer harnesses covering every hand-rolled parser; fuzzing found and fixed a real OOM in the pcapng reader (unbounded allocation from an untrusted length field) --- src/main.cpp | 326 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 326 insertions(+) create mode 100644 src/main.cpp (limited to 'src/main.cpp') diff --git a/src/main.cpp b/src/main.cpp new file mode 100644 index 0000000..3a3e925 --- /dev/null +++ b/src/main.cpp @@ -0,0 +1,326 @@ +// Stage 2 (PLAN.md): Ethernet/IP/TCP/UDP decoders producing a live +// packet-list line per capture. The TUI itself is still an open +// question (PLAN.md), so this prints to stdout for now; -x keeps the +// stage-1 hex dump available underneath each summary. +// +// Stage 3: -w writes the same capture out as pcapng alongside +// the summary, so files stay Wireshark-compatible (PLAN.md). +// +// Stage 4: capture thread -> bounded CaptureQueue -> render loop on +// the main thread (PLAN.md's architecture sketch). The capture thread +// only copies raw bytes into the queue; decoding, printing, and +// pcapng-writing all happen on the consumer side, so a slow render +// path can never block the capture thread - a full queue drops the +// packet and counts it instead. +// +// Stage 5: L7 dissectors register into an L7Registry keyed by port +// (wireframe/l7/dissector.hpp) and get consulted from summarize_packet +// once TCP/UDP decode a port number. DNS is the first one, proving the +// interface against real traffic rather than synthetic bytes. +// +// IPv6: dispatched by version nibble rather than assumed absent -- +// every live-capture test so far has shown real IPv6 background +// traffic silently dropped once the decoder only handled IPv4. +// +// Stage 6: -f compiles a tcpdump-style BPF expression via +// libpcap's own compiler (wireframe/filter.hpp) and installs it with +// pcap_setfilter(), filtering in the kernel before packets ever reach +// userspace - rather than hand-rolling a second BPF parser. +// +// Device-open/datalink-validate/filter/pcapng/signal-handler setup all +// goes through wireframe::CaptureSession (wireframe/capture_session.hpp) +// - the same one gui_main.cpp uses - so the CLI/TUI and GUI frontends +// can't drift apart on that setup path. + +#include + +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include + +#include "wireframe/capture_session.hpp" +#include "wireframe/search.hpp" +#include "wireframe/summarize.hpp" + +namespace { + +// Queue capacity: how many packets can be buffered between the capture +// thread and the render loop before new packets get dropped. Sized as +// a fixed constant rather than a flag - tune later if a real workload +// needs it, not speculatively now. +constexpr std::size_t kQueueCapacity = 4096; + +void hex_dump(std::span bytes) { + for (const auto& line : wireframe::hex_dump_lines(bytes)) { + std::printf("%s\n", line.c_str()); + } + std::printf("\n"); +} + +struct RenderOptions { + bool verbose_hex; + int datalink; + wireframe::pcapng::Writer* pcapng_writer; + std::string search_term; // display filter - see wireframe/search.hpp +}; + +void render_packet(const wireframe::CapturedPacket& packet, const RenderOptions& opts) { + std::span bytes{packet.data}; + + std::string line = wireframe::summarize_packet(bytes, opts.datalink); + + // -g is a display filter, not a capture filter: still written to + // -w regardless of whether it matches, since -w should reflect + // what was actually captured (that's -f's job), not what's shown. + if (opts.pcapng_writer) { + opts.pcapng_writer->write_packet(/*interface_id=*/0, packet.ts_sec, packet.ts_usec, bytes, + packet.original_len); + } + + if (!wireframe::matches_search(line, opts.search_term)) return; + + std::printf("%s\n", line.c_str()); + if (opts.verbose_hex) hex_dump(bytes); + + // Flush per packet: stdout is fully buffered off a tty, and this is + // a live capture tool, not a batch one. + std::fflush(stdout); +} + +// TUI mode (-t): a scrolling packet list in a full-screen view, built +// with FTXUI (see NAMES.md-adjacent decision: chosen over notcurses for +// pure-C++ portability - no C build-system/dependency chain to fight +// on every platform PLAN.md targets, and genuine Windows console +// support, which notcurses lacks). +// +// A dedicated consumer thread pops from the capture queue and appends +// formatted rows to shared state; the UI thread just redraws on +// Event::Custom. 'q'/Esc triggers the same pcap_breakloop() shutdown +// path as Ctrl-C, so there's one shutdown sequence, not two: breakloop +// -> capture thread's pcap_loop returns -> queue.stop() -> consumer +// drains and calls screen.Exit() -> screen.Loop() returns. +void run_tui(wireframe::CaptureSession& session, wireframe::CaptureQueue& queue, + RenderOptions& opts) { + using namespace ftxui; + + constexpr std::size_t kMaxRows = 2000; // cap memory; oldest rows scroll off + + std::mutex state_mutex; + std::deque rows; + std::uint64_t packet_count = 0; + + // '/' search: a display filter over `rows`, independent of the + // capture itself (wireframe/search.hpp) - typed and read only on + // the UI thread (the consumer thread never touches it), so unlike + // `rows`/`packet_count` it doesn't need state_mutex. + bool searching = false; + std::string search_term; + bool replay_finished = false; // guarded by state_mutex, like rows/packet_count + + auto screen = ScreenInteractive::Fullscreen(); + + std::thread consumer_thread([&] { + while (auto packet = queue.pop()) { + std::span bytes{packet->data}; + std::string line = wireframe::summarize_packet(bytes, opts.datalink); + + if (opts.pcapng_writer) { + opts.pcapng_writer->write_packet(/*interface_id=*/0, packet->ts_sec, + packet->ts_usec, bytes, packet->original_len); + } + + { + std::lock_guard lock(state_mutex); + rows.push_back(std::move(line)); + if (rows.size() > kMaxRows) rows.pop_front(); + ++packet_count; + } + screen.PostEvent(Event::Custom); + } + // Replay reaching end-of-file on its own (stop_requested() still + // false) shouldn't close the window - the point of replaying a + // file is browsing/searching it afterward, not watching it flash + // by. An explicit stop (q/Esc below, or an external signal, both + // of which set stop_requested()) always closes, live capture + // included - that's still the same behavior as before. + if (session.is_replay() && !session.stop_requested()) { + { + std::lock_guard lock(state_mutex); + replay_finished = true; + } + screen.PostEvent(Event::Custom); // one more redraw for the final state + } else { + screen.Exit(); + } + }); + + auto renderer = Renderer([&] { + std::lock_guard lock(state_mutex); + Elements lines; + std::size_t shown = 0; + for (const auto& row : rows) { + if (!wireframe::matches_search(row, search_term)) continue; + lines.push_back(text(row)); + ++shown; + } + + std::string status = "packets: " + std::to_string(packet_count); + if (!search_term.empty()) status += " (" + std::to_string(shown) + " shown)"; + if (replay_finished) status += " [replay finished]"; + status += " dropped: " + std::to_string(queue.dropped()) + + (searching ? " (Enter to apply, Esc to clear)" : " (/ to search, q to quit)"); + // Kernel/interface-level drops: a traffic spike can drop + // packets before libpcap ever hands them to our callback, + // which the queue-side counter above can't see. + Elements footer = {text(status) | dim}; + if (auto stats = session.stats()) { + if (stats->dropped > 0 || stats->if_dropped > 0) { + std::string kernel_status = "kernel/interface dropped " + + std::to_string(stats->dropped) + "/" + + std::to_string(stats->if_dropped) + " (received " + + std::to_string(stats->received) + ")"; + footer.push_back(text(kernel_status) | color(Color::Yellow)); + } + } + if (searching || !search_term.empty()) { + footer.push_back(text("search: " + search_term + (searching ? "_" : "")) | + color(Color::Green)); + } + std::string title = session.is_replay() ? ("wireframe - replaying " + session.device()) + : "wireframe - live capture"; + return vbox({ + text(title) | bold | color(Color::Cyan), + separator(), + vbox(std::move(lines)) | yframe | flex, + separator(), + vbox(std::move(footer)), + }) | + border; + }); + + auto component = CatchEvent(renderer, [&](const Event& event) { + if (searching) { + if (event == Event::Return) { + searching = false; + return true; + } + if (event == Event::Escape) { + searching = false; + search_term.clear(); + return true; + } + if (event == Event::Backspace) { + if (!search_term.empty()) search_term.pop_back(); + return true; + } + if (event.is_character()) { + search_term += event.character(); + return true; + } + return true; // swallow anything else while typing (don't let it fall through to quit) + } + if (event == Event::Character('/')) { + searching = true; + return true; + } + if (event == Event::Character('q') || event == Event::Escape) { + session.request_stop(); + // Closes immediately rather than waiting for the capture/ + // replay thread to actually finish and drain the queue -- + // necessary for replay mode specifically (that thread may + // already be long gone once the user quits after browsing a + // finished replay, so nothing else would ever call this). + // main() still joins the thread properly afterward either way. + screen.Exit(); + return true; + } + return false; + }); + + screen.Loop(component); + consumer_thread.join(); +} + +} // namespace + +int main(int argc, char** argv) { + wireframe::CaptureSessionOptions options; + bool tui_mode = false; + RenderOptions opts{ + .verbose_hex = false, .datalink = 0, .pcapng_writer = nullptr, .search_term = ""}; + + for (int i = 1; i < argc; ++i) { + if (std::strcmp(argv[i], "-x") == 0) { + opts.verbose_hex = true; + } else if (std::strcmp(argv[i], "-t") == 0 || std::strcmp(argv[i], "--tui") == 0) { + tui_mode = true; + } else if (std::strcmp(argv[i], "-w") == 0 && i + 1 < argc) { + options.pcapng_output_path = argv[++i]; + } else if (std::strcmp(argv[i], "-f") == 0 && i + 1 < argc) { + options.filter_expr = argv[++i]; + } else if (std::strcmp(argv[i], "-r") == 0 && i + 1 < argc) { + options.replay_input_path = argv[++i]; + } else if (std::strcmp(argv[i], "-g") == 0 && i + 1 < argc) { + opts.search_term = argv[++i]; + } else if (options.device.empty()) { + options.device = argv[i]; + } + } + + wireframe::CaptureSession session; + if (auto err = session.open(options)) { + std::fprintf(stderr, "%s\n", err->c_str()); + return 1; + } + opts.datalink = session.datalink(); + opts.pcapng_writer = session.pcapng_writer(); + session.install_signal_handlers(); + + if (!tui_mode) { + if (session.is_replay()) { + std::printf("replaying %s (%s)\n", session.device().c_str(), + pcap_datalink_val_to_name(session.datalink())); + } else { + std::printf("capturing on %s (%s, ctrl-c to stop)\n", session.device().c_str(), + pcap_datalink_val_to_name(session.datalink())); + } + } + + wireframe::CaptureQueue queue(kQueueCapacity); + std::thread capture_thread = session.start_capture_thread(queue); + + if (tui_mode) { + run_tui(session, queue, opts); + } else { + while (auto packet = queue.pop()) { + render_packet(*packet, opts); + } + } + + capture_thread.join(); + + if (queue.dropped() > 0) { + std::fprintf(stderr, "dropped %llu packets (render side fell behind)\n", + static_cast(queue.dropped())); + } + // Kernel-level counters, queried before the session closes its + // handle: a traffic spike can drop packets before libpcap ever + // hands them to our callback, which queue.dropped() can't see. + if (auto stats = session.stats()) { + if (stats->dropped > 0 || stats->if_dropped > 0) { + std::fprintf(stderr, "kernel/interface dropped %u/%u packets (received %u)\n", + stats->dropped, stats->if_dropped, stats->received); + } + } + + return 0; +} -- cgit v1.2.3