From 19e7e447c0dec65beef51508d54e8af279411613 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20K=C3=BCthe?= <m.k@mk16.de>
Date: Wed, 13 Mar 2024 21:08:58 +0000
Subject: [PATCH] Fix memory leak

See https://stackoverflow.com/questions/78143322/how-can-i-read-from-a-tap-device-via-posixstream-descriptor-simultaneously-w/78143690?noredirect=1#comment137772998_78143690
---
 bindings/cpp/tuntap++.cc | 40 ++++++++++++++++------------------------
 bindings/cpp/tuntap++.hh | 12 +++++++++---
 2 files changed, 25 insertions(+), 27 deletions(-)

diff --git a/bindings/cpp/tuntap++.cc b/bindings/cpp/tuntap++.cc
index d0c3a70..3dee788 100644
--- a/bindings/cpp/tuntap++.cc
+++ b/bindings/cpp/tuntap++.cc
@@ -7,7 +7,7 @@
 namespace tuntap {
 
 tuntap::tuntap(int mode, int id)
-    : _dev{::tuntap_init()}, _started{true}
+    : _dev{::tuntap_init()}
 {
     if (mode != TUNTAP_MODE_ETHERNET && mode != TUNTAP_MODE_TUNNEL) {
         throw std::invalid_argument("Unknown tuntap mode");
@@ -15,41 +15,33 @@ tuntap::tuntap(int mode, int id)
     if (id < 0 || id > TUNTAP_ID_MAX) {
         throw std::invalid_argument("Tunnel ID is invalid");
     }
-    if (::tuntap_start(_dev, mode, id)) {
+    if (::tuntap_start(_dev.get(), mode, id)) {
         throw std::runtime_error("tuntap_start failed");
     }
 }
 
-tuntap::~tuntap()
-{
-    if (_started) {
-        ::tuntap_destroy(_dev);
-    }
-}
-
 tuntap::tuntap(tuntap &&t) noexcept
-    : _dev(nullptr)
+    : _dev()
 {
-    std::swap(t._dev, this->_dev);
+    t._dev.swap(this->_dev);
 }
 
 void
 tuntap::release() noexcept
 {
-    ::tuntap_release(_dev);
-    _started = false;
+    _dev.release();
 }
 
 std::string
 tuntap::name() const noexcept
 {
-    return std::string(::tuntap_get_ifname(_dev));
+    return std::string(::tuntap_get_ifname(_dev.get()));
 }
 
 void
 tuntap::name(std::string const &s)
 {
-    if (::tuntap_set_ifname(_dev, s.c_str())) {
+    if (::tuntap_set_ifname(_dev.get(), s.c_str())) {
         throw std::runtime_error("Failed to set ifname");
     }
 }
@@ -57,13 +49,13 @@ tuntap::name(std::string const &s)
 t_tun
 tuntap::native_handle() const noexcept
 {
-    return ::tuntap_get_fd(this->_dev);
+    return ::tuntap_get_fd(_dev.get());
 }
 
 void
 tuntap::up()
 {
-    if (::tuntap_up(_dev)) {
+    if (::tuntap_up(_dev.get())) {
         throw std::runtime_error("Failed to bring up tuntap device");
     }
 }
@@ -71,7 +63,7 @@ tuntap::up()
 void
 tuntap::down()
 {
-    if (::tuntap_down(_dev)) {
+    if (::tuntap_down(_dev.get())) {
         throw std::runtime_error("Failed to bring down tuntap device");
     }
 }
@@ -79,7 +71,7 @@ tuntap::down()
 int
 tuntap::mtu() const noexcept
 {
-    return ::tuntap_get_mtu(_dev);
+    return ::tuntap_get_mtu(_dev.get());
 }
 
 void
@@ -88,7 +80,7 @@ tuntap::mtu(int m)
     if (m < 1 || m > 65535) {
         throw std::invalid_argument("Invalid mtu");
     }
-    if (::tuntap_set_mtu(_dev, m)) {
+    if (::tuntap_set_mtu(_dev.get(), m)) {
         throw std::runtime_error("Failed to set mtu for tuntap device");
     }
 }
@@ -99,7 +91,7 @@ tuntap::ip(std::string const &s, int netmask)
     if (netmask > 128) {
         throw std::invalid_argument("Invalid netmask");
     }
-    if (::tuntap_set_ip(_dev, s.c_str(), netmask)) {
+    if (::tuntap_set_ip(_dev.get(), s.c_str(), netmask)) {
         throw std::runtime_error("Failed to set ip for tuntap device");
     }
 }
@@ -107,19 +99,19 @@ tuntap::ip(std::string const &s, int netmask)
 int
 tuntap::read(void *buf, size_t len) noexcept
 {
-	return ::tuntap_read(_dev, buf, len);
+	return ::tuntap_read(_dev.get(), buf, len);
 }
 
 int
 tuntap::write(void *buf, size_t len) noexcept
 {
-	return ::tuntap_write(_dev, buf, len);
+	return ::tuntap_write(_dev.get(), buf, len);
 }
 
 void
 tuntap::nonblocking(bool b)
 {
-    if (::tuntap_set_nonblocking(_dev, int(b))) {
+    if (::tuntap_set_nonblocking(_dev.get(), static_cast<int>(b))) {
         throw std::runtime_error("Failed to change non-blocking state for tuntap device");
     }
 }
diff --git a/bindings/cpp/tuntap++.hh b/bindings/cpp/tuntap++.hh
index f546312..a33322f 100644
--- a/bindings/cpp/tuntap++.hh
+++ b/bindings/cpp/tuntap++.hh
@@ -3,6 +3,7 @@
 #define LIBTUNTAP_ALY0MA60
 
 #include <string>
+#include <memory>
 
 #include <tuntap.h>
 
@@ -12,7 +13,6 @@ class tuntap
 {
  public:
   tuntap(int, int = TUNTAP_ID_ANY);
-  ~tuntap();
   tuntap(tuntap const &) = delete;
   tuntap & operator = (tuntap const &) = delete;
   tuntap(tuntap &&) noexcept;
@@ -37,8 +37,14 @@ class tuntap
   void release() noexcept;
   void nonblocking(bool);
  private:
-  struct device* _dev;
-  bool _started;
+  class TunTapDestroyer final {
+      public:
+          void operator()(device * dev) const noexcept {
+              if (dev)
+                  ::tuntap_destroy(dev);
+          }
+  };
+  std::unique_ptr<device, TunTapDestroyer> _dev;
 };
 
 } /* tuntap */