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)

1 files changed, 122 insertions, 0 deletions

diff --git a/tests/test_capture_queue.cpp b/tests/test_capture_queue.cpp
new file mode 100644
index 0000000..da2da28
--- /dev/null
+++ b/tests/test_capture_queue.cpp
@@ -0,0 +1,122 @@
+#include <doctest/doctest.h>
+
+#include <atomic>
+#include <chrono>
+#include <thread>
+
+#include "wireframe/capture_queue.hpp"
+
+using namespace wireframe;
+
+TEST_CASE("try_push/pop returns packets in FIFO order") {
+    CaptureQueue queue(4);
+    for (std::uint32_t i = 0; i < 3; ++i) {
+        CapturedPacket p;
+        p.ts_sec = i;
+        p.data = {static_cast<unsigned char>(i)};
+        CHECK(queue.try_push(std::move(p)));
+    }
+    for (std::uint32_t i = 0; i < 3; ++i) {
+        auto p = queue.pop();
+        REQUIRE(p.has_value());
+        CHECK(p->ts_sec == i);
+    }
+    CHECK(queue.dropped() == 0);
+}
+
+TEST_CASE("try_push drops and counts once the queue is full") {
+    CaptureQueue queue(2);
+    CapturedPacket a, b, c;
+    CHECK(queue.try_push(std::move(a)));
+    CHECK(queue.try_push(std::move(b)));
+    CHECK_FALSE(queue.try_push(std::move(c)));  // full: dropped, not blocked
+    CHECK(queue.dropped() == 1);
+}
+
+TEST_CASE("stop() drains items already queued before pop() returns nullopt") {
+    CaptureQueue queue(4);
+    CapturedPacket a, b;
+    queue.try_push(std::move(a));
+    queue.try_push(std::move(b));
+    queue.stop();
+
+    CHECK(queue.pop().has_value());
+    CHECK(queue.pop().has_value());
+    CHECK_FALSE(queue.pop().has_value());  // drained and stopped
+}
+
+TEST_CASE("pop() blocks until a packet is pushed") {
+    CaptureQueue queue(4);
+    std::thread producer([&] {
+        std::this_thread::sleep_for(std::chrono::milliseconds(50));
+        CapturedPacket p;
+        p.data = {0x42};
+        queue.try_push(std::move(p));
+    });
+
+    auto p = queue.pop();
+    REQUIRE(p.has_value());
+    CHECK(p->data[0] == 0x42);
+    producer.join();
+}
+
+TEST_CASE("push() succeeds immediately when there's room") {
+    CaptureQueue queue(4);
+    CapturedPacket p;
+    p.data = {0x01};
+    CHECK(queue.push(std::move(p)));
+    CHECK(queue.dropped() == 0);
+}
+
+TEST_CASE("push() blocks for room instead of dropping, unlike try_push()") {
+    CaptureQueue queue(1);
+    CapturedPacket a;
+    a.data = {0xAA};
+    CHECK(queue.try_push(std::move(a)));  // fills the only slot
+
+    std::atomic<bool> pushed{false};
+    std::thread producer([&] {
+        CapturedPacket b;
+        b.data = {0xBB};
+        CHECK(queue.push(std::move(b)));  // must block until the pop() below frees room
+        pushed.store(true);
+    });
+
+    std::this_thread::sleep_for(std::chrono::milliseconds(50));
+    CHECK_FALSE(pushed.load());  // still blocked: queue was full this whole time
+
+    auto first = queue.pop();  // frees a slot
+    REQUIRE(first.has_value());
+    CHECK(first->data[0] == 0xAA);
+
+    producer.join();
+    CHECK(pushed.load());
+    CHECK(queue.dropped() == 0);  // never dropped - it waited instead
+
+    auto second = queue.pop();
+    REQUIRE(second.has_value());
+    CHECK(second->data[0] == 0xBB);
+}
+
+TEST_CASE("push() returns false without pushing if stop() is called while it's waiting") {
+    CaptureQueue queue(1);
+    CapturedPacket a;
+    a.data = {0xAA};
+    queue.try_push(std::move(a));  // fill the only slot
+
+    std::atomic<bool> result_ready{false};
+    std::atomic<bool> push_result{true};
+    std::thread producer([&] {
+        CapturedPacket b;
+        b.data = {0xBB};
+        push_result.store(queue.push(std::move(b)));
+        result_ready.store(true);
+    });
+
+    std::this_thread::sleep_for(std::chrono::milliseconds(50));
+    queue.stop();
+    producer.join();
+
+    CHECK(result_ready.load());
+    CHECK_FALSE(push_result.load());
+}