Merge #18077: net: Add NAT-PMP port forwarding support

a191e23b8e doc: Add release notes (Hennadii Stepanov)
ae749d12dd doc: Add libnatpmp stuff (Hennadii Stepanov)
e28f9be87a ci: Add libnatpmp-dev package to some builds (Hennadii Stepanov)
5a0185b6c9 gui: Add NAT-PMP network option (Hennadii Stepanov)
a39f7336a3 net: Add -natpmp command line option (Hennadii Stepanov)
28acffd9d5 net: Add NAT-PMP to port mapping loop (Hennadii Stepanov)
a8d9f275d0 net: Add libnatpmp support (Hennadii Stepanov)
58e8364dcd gui: Apply port mapping changes on dialog exit (Hennadii Stepanov)
cf151cc68c scripted-diff: Rename UPnP stuff (Hennadii Stepanov)
4e91b1e24d net: Add flags for port mapping protocols (Hennadii Stepanov)
8b50d1b5bb net: Keep trying to use UPnP when -upnp=1 (Hennadii Stepanov)
28e2961fd6 refactor: Replace magic number with named constant (Hennadii Stepanov)
02ccf69dd6 refactor: Move port mapping code to its own module (Hennadii Stepanov)

Pull request description:

  Close #11902
  This PR is an alternative to:
  - #12288
  - #15717

  To compile with NAT-PMP support on Ubuntu [`libnatpmp-dev`](https://packages.ubuntu.com/source/bionic/libnatpmp) should be available.

  Log excerpt:
  ```
  2020-02-05T20:12:28Z [mapport] NAT-PMP: public address = 95.164.65.194
  2020-02-05T20:12:28Z [mapport] AddLocal(95.164.65.194:18333,3)
  2020-02-05T20:12:28Z [mapport] NAT-PMP: port mapping successful.
  ```

  See: [`libnatpmp`](https://miniupnp.tuxfamily.org/libnatpmp.html)

  ---

  Some follow-ups are out of this PR's scope:
  - mention NAT-PMP library in the version message
  - ~integrate NAT-PMP into the GUI~ (already [added](https://github.com/bitcoin/bitcoin/pull/18077#issuecomment-589405068))

ACKs for top commit:
  laanwj:
    Tested and code review ACK a191e23b8e

Tree-SHA512: 10e19267c21bf30f20ff1abfc882d526049f0e790b95e12f109dc2bed7c0aef45de03eaf967f4e667e7509be04f1873a5c508087393d947205f3aab2ad6d7cf1

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=$enableval],
@@ -1206,6 +1218,7 @@ if test "x$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]])
@@ -1303,6 +1316,13 @@ 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
@@ -1561,6 +1581,31 @@ 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
@@ -1707,6 +1752,7 @@ 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)
@@ -1794,6 +1840,7 @@ 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"