Merge bitcoin/bitcoin#26896: build: Remove port-forwarding runtime setting options from configure

d51f0fa doc: add release notes for 26896 (fanquake)
2b24879 build: remove --enable-upnp-default from configure (fanquake)
02f5a5e build: remove --enable-natpmp-default from configure (fanquake)
25a0e8b Remove configure-time setting of DEFAULT_UPNP (fanquake)
06562e5 Remove configure-time setting of DEFAULT_NATPMP (fanquake)

Pull request description:

  This PR removes the `--enable-upnp-default` and `--enable-natpmp-default` options from configure.

  It's odd to me that we maintain configure-time options for setting the default port-forwarding runtime state (but no other similar options), and I'm not sure what use-case it satisfies, that can't be achieved by multiple other means. I also doubt that we'll ever restart using these in release builds, or turning on any of this by default.

  I think the only scenario these options would be used is when you want to compile your own binaries (we don't use them in Guix), with port-forwarding on by default, but otherwise can't or don't want to use a `.conf` file, can't or don't want to pass command line options at runtime, and also don't want to modify the source code?

ACKs for top commit:
  hebasto:
    ACK d51f0fa, rebased and comments have been addressed since my recent [review](bitcoin/bitcoin#26896 (review)).
  TheCharlatan:
    ACK d51f0fa

Tree-SHA512: 481decd8bddd8b03b7319591e3acf189f7b6b96c9a9a8c5bc1a3f8ec00d0b8f9b52d2f5c28a298a2ec947cfe9611cfd184e393ccb2e4e21bfce86ca7d4de60d3

Author: fanquake

configure.ac

@@ -163,24 +163,12 @@ AC_ARG_WITH([miniupnpc],
   [use_upnp=$withval],
   [use_upnp=auto])
 
-AC_ARG_ENABLE([upnp-default],
-  [AS_HELP_STRING([--enable-upnp-default],
-  [if UPNP is enabled, turn it on at startup (default is no)])],
-  [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],
@@ -1765,15 +1753,8 @@ if test "$have_miniupnpc" = "no"; then
 else
   if test "$use_upnp" != "no"; then
     AC_MSG_RESULT([yes])
-    AC_MSG_CHECKING([whether to build with UPnP enabled by default])
     use_upnp=yes
-    upnp_setting=0
-    if test "$use_upnp_default" != "no"; then
-      use_upnp_default=yes
-      upnp_setting=1
-    fi
-    AC_MSG_RESULT([$use_upnp_default])
-    AC_DEFINE_UNQUOTED([USE_UPNP],[$upnp_setting],[UPnP support not compiled if undefined, otherwise value (0 or 1) determines default state])
+    AC_DEFINE([USE_UPNP], [1], [Define to 1 if UPnP support should be compiled in.])
     if test "$TARGET_OS" = "windows"; then
       MINIUPNPC_CPPFLAGS="$MINIUPNPC_CPPFLAGS -DSTATICLIB -DMINIUPNP_STATICLIB"
     fi
@@ -1793,15 +1774,8 @@ if test "$have_natpmp" = "no"; then
 else
   if test "$use_natpmp" != "no"; then
     AC_MSG_RESULT([yes])
-    AC_MSG_CHECKING([whether to build with NAT-PMP enabled by default])
     use_natpmp=yes
-    natpmp_setting=0
-    if test "$use_natpmp_default" != "no"; 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])
+    AC_DEFINE([USE_NATPMP], [1], [Define to 1 if UPnP support should be compiled in.])
     if test "$TARGET_OS" = "windows"; then
       NATPMP_CPPFLAGS="$NATPMP_CPPFLAGS -DSTATICLIB -DNATPMP_STATICLIB"
     fi

doc/build-unix.md

@@ -72,7 +72,7 @@ executables, which are based on BerkeleyDB 4.8. If you do not care about wallet
 
 To build Bitcoin Core without wallet, see [*Disable-wallet mode*](#disable-wallet-mode)
 
-Optional port mapping libraries (see: `--with-miniupnpc`, `--enable-upnp-default`, and `--with-natpmp`, `--enable-natpmp-default`):
+Optional port mapping libraries (see: `--with-miniupnpc` and `--with-natpmp`):
 
     sudo apt install libminiupnpc-dev libnatpmp-dev
 
@@ -133,7 +133,7 @@ pass `--with-incompatible-bdb` to configure. Otherwise, you can build Berkeley D
 
 To build Bitcoin Core without wallet, see [*Disable-wallet mode*](#disable-wallet-mode)
 
-Optional port mapping libraries (see: `--with-miniupnpc`, `--enable-upnp-default`, and `--with-natpmp`, `--enable-natpmp-default`):
+Optional port mapping libraries (see: `--with-miniupnpc` and `--with-natpmp`):
 
     sudo dnf install miniupnpc-devel libnatpmp-devel
 
@@ -176,22 +176,14 @@ miniupnpc
 
 [miniupnpc](https://miniupnp.tuxfamily.org) may be used for UPnP port mapping.  It can be downloaded from [here](
 https://miniupnp.tuxfamily.org/files/).  UPnP support is compiled in and
-turned off by default.  See the configure options for UPnP behavior desired:
-
-    --without-miniupnpc      No UPnP support, miniupnp not required
-    --disable-upnp-default   (the default) UPnP support turned off by default at runtime
-    --enable-upnp-default    UPnP support turned on by default at runtime
+turned off by default.
 
 libnatpmp
 ---------
 
 [libnatpmp](https://miniupnp.tuxfamily.org/libnatpmp.html) may be used for NAT-PMP port mapping. It can be downloaded
 from [here](https://miniupnp.tuxfamily.org/files/). NAT-PMP support is compiled in and
-turned off by default. See the configure options for NAT-PMP behavior desired:
-
-    --without-natpmp          No NAT-PMP support, libnatpmp not required
-    --disable-natpmp-default  (the default) NAT-PMP support turned off by default at runtime
-    --enable-natpmp-default   NAT-PMP support turned on by default at runtime
+turned off by default.
 
 Berkeley DB
 -----------

doc/release-notes-26896.md

@@ -0,0 +1,7 @@
+Build System
+------------
+
+The --enable-upnp-default and --enable-natpmp-default options
+have been removed. If you want to use port mapping, you can
+configure it using a .conf file, or by passing the relevant
+options at runtime.

src/mapport.h

@@ -5,17 +5,9 @@
 #ifndef BITCOIN_MAPPORT_H
 #define BITCOIN_MAPPORT_H
 
-#ifdef USE_UPNP
-static constexpr bool DEFAULT_UPNP = USE_UPNP;
-#else
 static constexpr bool DEFAULT_UPNP = false;
-#endif // USE_UPNP
 
-#ifdef USE_NATPMP
-static constexpr bool DEFAULT_NATPMP = USE_NATPMP;
-#else
 static constexpr bool DEFAULT_NATPMP = false;
-#endif // USE_NATPMP
 
 enum MapPortProtoFlag : unsigned int {
     NONE = 0x00,