net: Add libnatpmp support

14 files changed, 195 insertions, 13 deletions

diff --git a/ci/test/00_setup_env_native_qt5.sh b/ci/test/00_setup_env_native_qt5.sh
index dc6b2aecb5..567145fe47 100644
--- a/ci/test/00_setup_env_native_qt5.sh
+++ b/ci/test/00_setup_env_native_qt5.sh
@@ -9,7 +9,7 @@ export LC_ALL=C.UTF-8
 export CONTAINER_NAME=ci_native_qt5
 export DOCKER_NAME_TAG=ubuntu:18.04  # Check that bionic gcc-7 can compile our c++17 and run our functional tests in python3, see doc/dependencies.md
 export PACKAGES="python3-zmq qtbase5-dev qttools5-dev-tools libdbus-1-dev libharfbuzz-dev"
-export DEP_OPTS="NO_QT=1 NO_UPNP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1"
+export DEP_OPTS="NO_QT=1 NO_UPNP=1 NO_NATPMP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1"
 export TEST_RUNNER_EXTRA="--previous-releases --coverage --extended --exclude feature_dbcrash"  # Run extended tests so that coverage does not fail, but exclude the very slow dbcrash
 export RUN_SECURITY_TESTS="true"
 export RUN_UNIT_TESTS_SEQUENTIAL="true"
diff --git a/configure.ac b/configure.ac
index c69b793d6e..352e7aaee7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -143,6 +143,18 @@ AC_ARG_ENABLE([upnp-default],
   [use_upnp_default=$enableval],
   [use_upnp_default=no])
 
+AC_ARG_WITH([natpmp],
+            [AS_HELP_STRING([--with-natpmp],
+                            [enable NAT-PMP (default is yes if libnatpmp is found)])],
+            [use_natpmp=$withval],
+            [use_natpmp=auto])
+
+AC_ARG_ENABLE([natpmp-default],
+              [AS_HELP_STRING([--enable-natpmp-default],
+                              [if NAT-PMP is enabled, turn it on at startup (default is no)])],
+              [use_natpmp_default=$enableval],
+              [use_natpmp_default=no])
+
 AC_ARG_ENABLE(tests,
     AS_HELP_STRING([--disable-tests],[do not compile tests (default is to compile)]),
     [use_tests=$enableval],
@@ -1203,6 +1215,7 @@ if test "x$enable_fuzz" = "xyes"; then
   enable_wallet=no
   use_bench=no
   use_upnp=no
+  use_natpmp=no
   use_zmq=no
 
   AX_CHECK_PREPROC_FLAG([-DABORT_ON_FAILED_ASSUME],[[DEBUG_CPPFLAGS="$DEBUG_CPPFLAGS -DABORT_ON_FAILED_ASSUME"]],,[[$CXXFLAG_WERROR]])
@@ -1300,6 +1313,13 @@ if test x$have_miniupnpc != xno; then
 fi
 fi
 
+dnl Check for libnatpmp (optional).
+if test "x$use_natpmp" != xno; then
+  AC_CHECK_HEADERS([natpmp.h],
+                   [AC_CHECK_LIB([natpmp], [initnatpmp], [NATPMP_LIBS=-lnatpmp], [have_natpmp=no])],
+                   [have_natpmp=no])
+fi
+
 if test x$build_bitcoin_wallet$build_bitcoin_cli$build_bitcoin_tx$build_bitcoind$bitcoin_enable_qt$use_tests$use_bench = xnonononononono; then
     use_boost=no
 else
@@ -1558,6 +1578,31 @@ else
   fi
 fi
 
+dnl Enable NAT-PMP support.
+AC_MSG_CHECKING([whether to build with support for NAT-PMP])
+if test "x$have_natpmp" = xno; then
+  if test "x$use_natpmp" = xyes; then
+     AC_MSG_ERROR([NAT-PMP requested but cannot be built. Use --without-natpmp])
+  fi
+  AC_MSG_RESULT([no])
+  use_natpmp=no
+else
+  if test "x$use_natpmp" != xno; then
+    AC_MSG_RESULT([yes])
+    AC_MSG_CHECKING([whether to build with NAT-PMP enabled by default])
+    use_natpmp=yes
+    natpmp_setting=0
+    if test "x$use_natpmp_default" != xno; then
+      use_natpmp_default=yes
+      natpmp_setting=1
+    fi
+    AC_MSG_RESULT($use_natpmp_default)
+    AC_DEFINE_UNQUOTED([USE_NATPMP], [$natpmp_setting], [NAT-PMP support not compiled if undefined, otherwise value (0 or 1) determines default state])
+  else
+    AC_MSG_RESULT([no])
+  fi
+fi
+
 dnl these are only used when qt is enabled
 BUILD_TEST_QT=""
 if test x$bitcoin_enable_qt != xno; then
@@ -1704,6 +1749,7 @@ AC_SUBST(SQLITE_LIBS)
 AC_SUBST(TESTDEFS)
 AC_SUBST(MINIUPNPC_CPPFLAGS)
 AC_SUBST(MINIUPNPC_LIBS)
+AC_SUBST(NATPMP_LIBS)
 AC_SUBST(EVENT_LIBS)
 AC_SUBST(EVENT_PTHREADS_LIBS)
 AC_SUBST(ZMQ_LIBS)
@@ -1791,6 +1837,7 @@ else
 fi
 echo "  with bench    = $use_bench"
 echo "  with upnp     = $use_upnp"
+echo "  with natpmp   = $use_natpmp"
 echo "  use asm       = $use_asm"
 echo "  sanitizers    = $use_sanitizers"
 echo "  debug enabled = $enable_debug"
diff --git a/depends/Makefile b/depends/Makefile
index 1ad21f6821..0de98f8e3c 100644
--- a/depends/Makefile
+++ b/depends/Makefile
@@ -37,6 +37,7 @@ NO_QR ?=
 NO_WALLET ?=
 NO_ZMQ ?=
 NO_UPNP ?=
+NO_NATPMP ?=
 MULTIPROCESS ?=
 FALLBACK_DOWNLOAD_PATH ?= https://bitcoincore.org/depends-sources
 
@@ -139,10 +140,12 @@ sqlite_packages_$(NO_SQLITE) = $(sqlite_packages)
 wallet_packages_$(NO_WALLET) = $(bdb_packages_) $(sqlite_packages_)
 
 upnp_packages_$(NO_UPNP) = $(upnp_packages)
+natpmp_packages_$(NO_NATPMP) = $(natpmp_packages)
+
 zmq_packages_$(NO_ZMQ) = $(zmq_packages)
 multiprocess_packages_$(MULTIPROCESS) = $(multiprocess_packages)
 
-packages += $($(host_arch)_$(host_os)_packages) $($(host_os)_packages) $(qt_packages_) $(wallet_packages_) $(upnp_packages_)
+packages += $($(host_arch)_$(host_os)_packages) $($(host_os)_packages) $(qt_packages_) $(wallet_packages_) $(upnp_packages_) $(natpmp_packages_)
 native_packages += $($(host_arch)_$(host_os)_native_packages) $($(host_os)_native_packages)
 
 ifneq ($(zmq_packages_),)
@@ -200,6 +203,7 @@ $(host_prefix)/share/config.site : config.site.in $(host_prefix)/.stamp_$(final_
             -e 's|@no_zmq@|$(NO_ZMQ)|' \
             -e 's|@no_wallet@|$(NO_WALLET)|' \
             -e 's|@no_upnp@|$(NO_UPNP)|' \
+            -e 's|@no_natpmp@|$(NO_NATPMP)|' \
             -e 's|@multiprocess@|$(MULTIPROCESS)|' \
             -e 's|@debug@|$(DEBUG)|' \
             $< > $@
diff --git a/depends/config.site.in b/depends/config.site.in
index f4531830c8..bbfbd42460 100644
--- a/depends/config.site.in
+++ b/depends/config.site.in
@@ -46,6 +46,10 @@ if test -z $with_miniupnpc && test -n "@no_upnp@"; then
   with_miniupnpc=no
 fi
 
+if test -z $with_natpmp && test -n "@no_natpmp@"; then
+  with_natpmp=no
+fi
+
 if test -z $with_gui && test -n "@no_qt@"; then
   with_gui=no
 fi
diff --git a/depends/packages/libnatpmp.mk b/depends/packages/libnatpmp.mk
new file mode 100644
index 0000000000..a24f201859
--- /dev/null
+++ b/depends/packages/libnatpmp.mk
@@ -0,0 +1,19 @@
+package=libnatpmp
+$(package)_version=20150609
+$(package)_download_path=https://miniupnp.tuxfamily.org/files/
+$(package)_file_name=$(package)-$($(package)_version).tar.gz
+$(package)_sha256_hash=e1aa9c4c4219bc06943d6b2130f664daee213fb262fcb94dd355815b8f4536b0
+
+define $(package)_set_vars
+  $(package)_build_opts=CC="$($(package)_cc)"
+endef
+
+define $(package)_build_cmds
+  $(MAKE) libnatpmp.a $($(package)_build_opts)
+endef
+
+define $(package)_stage_cmds
+  mkdir -p $($(package)_staging_prefix_dir)/include $($(package)_staging_prefix_dir)/lib &&\
+  install *.h $($(package)_staging_prefix_dir)/include &&\
+  install libnatpmp.a $($(package)_staging_prefix_dir)/lib
+endef
diff --git a/depends/packages/packages.mk b/depends/packages/packages.mk
index d4fd23a47b..0f35ca0d2d 100644
--- a/depends/packages/packages.mk
+++ b/depends/packages/packages.mk
@@ -16,6 +16,7 @@ sqlite_packages=sqlite
 zmq_packages=zeromq
 
 upnp_packages=miniupnpc
+natpmp_packages=libnatpmp
 
 multiprocess_packages = libmultiprocess capnp
 multiprocess_native_packages = native_libmultiprocess native_capnp
diff --git a/src/Makefile.am b/src/Makefile.am
index ec697515d9..d5975ccc79 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -598,7 +598,7 @@ bitcoin_bin_ldadd = \
   $(LIBMEMENV) \
   $(LIBSECP256K1)
 
-bitcoin_bin_ldadd += $(BOOST_LIBS) $(BDB_LIBS) $(MINIUPNPC_LIBS) $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(ZMQ_LIBS) $(SQLITE_LIBS)
+bitcoin_bin_ldadd += $(BOOST_LIBS) $(BDB_LIBS) $(MINIUPNPC_LIBS) $(NATPMP_LIBS) $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(ZMQ_LIBS) $(SQLITE_LIBS)
 
 bitcoind_SOURCES = $(bitcoin_daemon_sources)
 bitcoind_CPPFLAGS = $(bitcoin_bin_cppflags)
diff --git a/src/Makefile.bench.include b/src/Makefile.bench.include
index beb3f8dfd2..56b8ca8ce6 100644
--- a/src/Makefile.bench.include
+++ b/src/Makefile.bench.include
@@ -74,7 +74,7 @@ bench_bench_bitcoin_SOURCES += bench/coin_selection.cpp
 bench_bench_bitcoin_SOURCES += bench/wallet_balance.cpp
 endif
 
-bench_bench_bitcoin_LDADD += $(BOOST_LIBS) $(BDB_LIBS) $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(MINIUPNPC_LIBS) $(SQLITE_LIBS)
+bench_bench_bitcoin_LDADD += $(BOOST_LIBS) $(BDB_LIBS) $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(MINIUPNPC_LIBS) $(NATPMP_LIBS) $(SQLITE_LIBS)
 bench_bench_bitcoin_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS) $(PTHREAD_FLAGS)
 
 CLEAN_BITCOIN_BENCH = bench/*.gcda bench/*.gcno $(GENERATED_BENCH_FILES)
diff --git a/src/Makefile.qt.include b/src/Makefile.qt.include
index f46310a603..3d41d203d3 100644
--- a/src/Makefile.qt.include
+++ b/src/Makefile.qt.include
@@ -320,7 +320,7 @@ if ENABLE_ZMQ
 bitcoin_qt_ldadd += $(LIBBITCOIN_ZMQ) $(ZMQ_LIBS)
 endif
 bitcoin_qt_ldadd += $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL) $(LIBBITCOIN_CONSENSUS) $(LIBBITCOIN_CRYPTO) $(LIBUNIVALUE) $(LIBLEVELDB) $(LIBLEVELDB_SSE42) $(LIBMEMENV) \
-  $(BOOST_LIBS) $(QT_LIBS) $(QT_DBUS_LIBS) $(QR_LIBS) $(BDB_LIBS) $(MINIUPNPC_LIBS) $(LIBSECP256K1) \
+  $(BOOST_LIBS) $(QT_LIBS) $(QT_DBUS_LIBS) $(QR_LIBS) $(BDB_LIBS) $(MINIUPNPC_LIBS) $(NATPMP_LIBS) $(LIBSECP256K1) \
   $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(SQLITE_LIBS)
 bitcoin_qt_ldflags = $(RELDFLAGS) $(AM_LDFLAGS) $(QT_LDFLAGS) $(LIBTOOL_APP_LDFLAGS) $(PTHREAD_FLAGS)
 bitcoin_qt_libtoolflags = $(AM_LIBTOOLFLAGS) --tag CXX
diff --git a/src/Makefile.qttest.include b/src/Makefile.qttest.include
index c05dd38737..a6a857d952 100644
--- a/src/Makefile.qttest.include
+++ b/src/Makefile.qttest.include
@@ -55,7 +55,7 @@ qt_test_test_bitcoin_qt_LDADD += $(LIBBITCOIN_ZMQ) $(ZMQ_LIBS)
 endif
 qt_test_test_bitcoin_qt_LDADD += $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL) $(LIBBITCOIN_CONSENSUS) $(LIBBITCOIN_CRYPTO) $(LIBUNIVALUE) $(LIBLEVELDB) \
   $(LIBLEVELDB_SSE42) $(LIBMEMENV) $(BOOST_LIBS) $(QT_DBUS_LIBS) $(QT_TEST_LIBS) $(QT_LIBS) \
-  $(QR_LIBS) $(BDB_LIBS) $(MINIUPNPC_LIBS) $(LIBSECP256K1) \
+  $(QR_LIBS) $(BDB_LIBS) $(MINIUPNPC_LIBS) $(NATPMP_LIBS) $(LIBSECP256K1) \
   $(EVENT_PTHREADS_LIBS) $(EVENT_LIBS) $(SQLITE_LIBS)
 qt_test_test_bitcoin_qt_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(QT_LDFLAGS) $(LIBTOOL_APP_LDFLAGS) $(PTHREAD_FLAGS)
 qt_test_test_bitcoin_qt_CXXFLAGS = $(AM_CXXFLAGS) $(QT_PIE_FLAGS)
diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index 3faa5ac968..4abf388bcc 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -167,7 +167,7 @@ test_test_bitcoin_LDADD += $(LIBBITCOIN_SERVER) $(LIBBITCOIN_CLI) $(LIBBITCOIN_C
   $(LIBLEVELDB) $(LIBLEVELDB_SSE42) $(LIBMEMENV) $(BOOST_LIBS) $(BOOST_UNIT_TEST_FRAMEWORK_LIB) $(LIBSECP256K1) $(EVENT_LIBS) $(EVENT_PTHREADS_LIBS)
 test_test_bitcoin_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 
-test_test_bitcoin_LDADD += $(BDB_LIBS) $(MINIUPNPC_LIBS) $(SQLITE_LIBS)
+test_test_bitcoin_LDADD += $(BDB_LIBS) $(MINIUPNPC_LIBS) $(NATPMP_LIBS) $(SQLITE_LIBS)
 test_test_bitcoin_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS) $(PTHREAD_FLAGS) -static
 
 if ENABLE_ZMQ
diff --git a/src/mapport.cpp b/src/mapport.cpp
index 5f0aeb5e40..f3ede623a3 100644
--- a/src/mapport.cpp
+++ b/src/mapport.cpp
@@ -16,6 +16,11 @@
 #include <threadinterrupt.h>
 #include <util/system.h>
 
+#ifdef USE_NATPMP
+#include <compat.h>
+#include <natpmp.h>
+#endif // USE_NATPMP
+
 #ifdef USE_UPNP
 #include <miniupnpc/miniupnpc.h>
 #include <miniupnpc/upnpcommands.h>
@@ -23,7 +28,7 @@
 // The minimum supported miniUPnPc API version is set to 10. This keeps compatibility
 // with Ubuntu 16.04 LTS and Debian 8 libminiupnpc-dev packages.
 static_assert(MINIUPNPC_API_VERSION >= 10, "miniUPnPc API version >= 10 assumed");
-#endif
+#endif // USE_UPNP
 
 #include <atomic>
 #include <cassert>
@@ -32,7 +37,7 @@ static_assert(MINIUPNPC_API_VERSION >= 10, "miniUPnPc API version >= 10 assumed"
 #include <string>
 #include <thread>
 
-#ifdef USE_UPNP
+#if defined(USE_NATPMP) || defined(USE_UPNP)
 static CThreadInterrupt g_mapport_interrupt;
 static std::thread g_mapport_thread;
 static std::atomic_uint g_mapport_target_proto{MapPortProtoFlag::NONE};
@@ -41,6 +46,106 @@ using namespace std::chrono_literals;
 static constexpr auto PORT_MAPPING_REANNOUNCE_PERIOD{20min};
 static constexpr auto PORT_MAPPING_RETRY_PERIOD{5min};
 
+#ifdef USE_NATPMP
+static uint16_t g_mapport_external_port = 0;
+static bool NatpmpInit(natpmp_t* natpmp)
+{
+    const int r_init = initnatpmp(natpmp, /* detect gateway automatically */ 0, /* forced gateway - NOT APPLIED*/ 0);
+    if (r_init == 0) return true;
+    LogPrintf("natpmp: initnatpmp() failed with %d error.\n", r_init);
+    return false;
+}
+
+static bool NatpmpDiscover(natpmp_t* natpmp, struct in_addr& external_ipv4_addr)
+{
+    const int r_send = sendpublicaddressrequest(natpmp);
+    if (r_send == 2 /* OK */) {
+        int r_read;
+        natpmpresp_t response;
+        do {
+            r_read = readnatpmpresponseorretry(natpmp, &response);
+        } while (r_read == NATPMP_TRYAGAIN);
+
+        if (r_read == 0) {
+            external_ipv4_addr = response.pnu.publicaddress.addr;
+            return true;
+        } else if (r_read == NATPMP_ERR_NOGATEWAYSUPPORT) {
+            LogPrintf("natpmp: The gateway does not support NAT-PMP.\n");
+        } else {
+            LogPrintf("natpmp: readnatpmpresponseorretry() for public address failed with %d error.\n", r_read);
+        }
+    } else {
+        LogPrintf("natpmp: sendpublicaddressrequest() failed with %d error.\n", r_send);
+    }
+
+    return false;
+}
+
+static bool NatpmpMapping(natpmp_t* natpmp, const struct in_addr& external_ipv4_addr, uint16_t private_port, bool& external_ip_discovered)
+{
+    const uint16_t suggested_external_port = g_mapport_external_port ? g_mapport_external_port : private_port;
+    const int r_send = sendnewportmappingrequest(natpmp, NATPMP_PROTOCOL_TCP, private_port, suggested_external_port, 3600 /*seconds*/);
+    if (r_send == 12 /* OK */) {
+        int r_read;
+        natpmpresp_t response;
+        do {
+            r_read = readnatpmpresponseorretry(natpmp, &response);
+        } while (r_read == NATPMP_TRYAGAIN);
+
+        if (r_read == 0) {
+            auto pm = response.pnu.newportmapping;
+            if (private_port == pm.privateport && pm.lifetime > 0) {
+                g_mapport_external_port = pm.mappedpublicport;
+                const CService external{external_ipv4_addr, pm.mappedpublicport};
+                if (!external_ip_discovered && fDiscover) {
+                    AddLocal(external, LOCAL_MAPPED);
+                    external_ip_discovered = true;
+                }
+                LogPrintf("natpmp: Port mapping successful. External address = %s\n", external.ToString());
+                return true;
+            } else {
+                LogPrintf("natpmp: Port mapping failed.\n");
+            }
+        } else if (r_read == NATPMP_ERR_NOGATEWAYSUPPORT) {
+            LogPrintf("natpmp: The gateway does not support NAT-PMP.\n");
+        } else {
+            LogPrintf("natpmp: readnatpmpresponseorretry() for port mapping failed with %d error.\n", r_read);
+        }
+    } else {
+        LogPrintf("natpmp: sendnewportmappingrequest() failed with %d error.\n", r_send);
+    }
+
+    return false;
+}
+
+static bool ProcessNatpmp()
+{
+    bool ret = false;
+    natpmp_t natpmp;
+    struct in_addr external_ipv4_addr;
+    if (NatpmpInit(&natpmp) && NatpmpDiscover(&natpmp, external_ipv4_addr)) {
+        bool external_ip_discovered = false;
+        const uint16_t private_port = GetListenPort();
+        do {
+            ret = NatpmpMapping(&natpmp, external_ipv4_addr, private_port, external_ip_discovered);
+        } while (ret && g_mapport_interrupt.sleep_for(PORT_MAPPING_REANNOUNCE_PERIOD));
+        g_mapport_interrupt.reset();
+
+        const int r_send = sendnewportmappingrequest(&natpmp, NATPMP_PROTOCOL_TCP, private_port, g_mapport_external_port, /* remove a port mapping */ 0);
+        g_mapport_external_port = 0;
+        if (r_send == 12 /* OK */) {
+            LogPrintf("natpmp: Port mapping removed successfully.\n");
+        } else {
+            LogPrintf("natpmp: sendnewportmappingrequest(0) failed with %d error.\n", r_send);
+        }
+    }
+
+    closenatpmp(&natpmp);
+    return ret;
+}
+#endif // USE_NATPMP
+
+#ifdef USE_UPNP
 static bool ProcessUpnp()
 {
     bool ret = false;
@@ -111,6 +216,7 @@ static bool ProcessUpnp()
 
     return ret;
 }
+#endif // USE_UPNP
 
 static void ThreadMapPort()
 {
@@ -123,7 +229,7 @@ void StartThreadMapPort()
 {
     if (!g_mapport_thread.joinable()) {
         assert(!g_mapport_interrupt);
-        g_mapport_thread = std::thread((std::bind(&TraceThread<void (*)()>, "mapport", &ThreadMapPort)));
+        g_mapport_thread = std::thread(std::bind(&TraceThread<void (*)()>, "mapport", &ThreadMapPort));
     }
 }
 
@@ -167,7 +273,7 @@ void StopMapPort()
     }
 }
 
-#else
+#else  // #if defined(USE_NATPMP) || defined(USE_UPNP)
 void StartMapPort(bool use_upnp)
 {
     // Intentionally left blank.
@@ -180,4 +286,4 @@ void StopMapPort()
 {
     // Intentionally left blank.
 }
-#endif
+#endif // #if defined(USE_NATPMP) || defined(USE_UPNP)
diff --git a/src/mapport.h b/src/mapport.h
index 6e33b6ef74..2cdde775d3 100644
--- a/src/mapport.h
+++ b/src/mapport.h
@@ -15,6 +15,7 @@ static const bool DEFAULT_UPNP = false;
 enum MapPortProtoFlag : unsigned int {
     NONE = 0x00,
     UPNP = 0x01,
+    NAT_PMP = 0x02,
 };
 
 void StartMapPort(bool use_upnp);
diff --git a/src/net.h b/src/net.h
index 2f4576016d..6c167954df 100644
--- a/src/net.h
+++ b/src/net.h
@@ -182,7 +182,7 @@ enum
     LOCAL_NONE,   // unknown
     LOCAL_IF,     // address a local interface listens on
     LOCAL_BIND,   // address explicit bound to
-    LOCAL_MAPPED, // address reported by UPnP
+    LOCAL_MAPPED, // address reported by UPnP or NAT-PMP
     LOCAL_MANUAL, // address explicitly specified (-externalip=)
 
     LOCAL_MAX