doc: Add Debian 12 Build documentation

Signed-off-by: Rodrigo Nardi <rnardi@netdef.org>
Signed-off-by: Martin Winter <mwinter@opensourcerouting.org>

doc/developer/building-frr-for-debian12.rst

@@ -0,0 +1,119 @@
+Debian 12
+=========
+
+Install required packages
+-------------------------
+
+Add packages:
+
+::
+
+   sudo apt-get install git autoconf automake libtool make \
+      libprotobuf-c-dev protobuf-c-compiler build-essential \
+      python3-dev python3-pytest python3-sphinx libjson-c-dev \
+      libelf-dev libreadline-dev cmake libcap-dev bison flex \
+      pkg-config texinfo gdb libgrpc-dev python3-grpc-tools
+
+.. include:: building-libunwind-note.rst
+
+.. include:: building-libyang.rst
+
+Get FRR, compile it and install it (from Git)
+---------------------------------------------
+
+**This assumes you want to build and install FRR from source and not
+using any packages**
+
+Add frr groups and user
+^^^^^^^^^^^^^^^^^^^^^^^
+
+::
+
+    sudo addgroup --system --gid 92 frr
+    sudo addgroup --system --gid 85 frrvty
+    sudo adduser --system --ingroup frr --home /var/opt/frr/ \
+       --gecos "FRR suite" --shell /bin/false frr
+    sudo usermod -a -G frrvty frr
+
+Download Source, configure and compile it
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+(You may prefer different options on configure statement. These are just
+an example.)
+
+::
+
+    git clone https://github.com/frrouting/frr.git frr
+    cd frr
+    ./bootstrap.sh
+    ./configure \
+        --localstatedir=/var/opt/frr \
+        --sbindir=/usr/lib/frr \
+        --sysconfdir=/etc/frr \
+        --enable-multipath=64 \
+        --enable-user=frr \
+        --enable-group=frr \
+        --enable-vty-group=frrvty \
+        --enable-configfile-mask=0640 \
+        --enable-logfile-mask=0640 \
+        --enable-fpm \
+        --with-pkg-git-version \
+        --with-pkg-extra-version=-MyOwnFRRVersion
+    make
+    make check
+    sudo make install
+
+For more compile options, see ``./configure --help``
+
+Create empty FRR configuration files
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+::
+
+    sudo install -m 640 -o frr -g frr /dev/null /etc/frr/frr.conf
+    sudo install -m 640 -o frr -g frr tools/etc/frr/daemons /etc/frr/daemons
+
+Edit ``/etc/frr/daemons`` and enable the FRR daemons for the protocols you need
+
+Enable IP & IPv6 forwarding
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Edit ``/etc/sysctl.conf`` and uncomment the following values (ignore the
+other settings)
+
+::
+
+    # Uncomment the next line to enable packet forwarding for IPv4
+    net.ipv4.ip_forward=1
+
+    # Uncomment the next line to enable packet forwarding for IPv6
+    #  Enabling this option disables Stateless Address Autoconfiguration
+    #  based on Router Advertisements for this host
+    net.ipv6.conf.all.forwarding=1
+
+**Reboot** or use ``sysctl -p`` to apply the same config to the running
+system
+
+Troubleshooting
+---------------
+
+Shared library error
+^^^^^^^^^^^^^^^^^^^^
+
+If you try and start any of the frrouting daemons you may see the below
+error due to the frrouting shared library directory not being found:
+
+::
+
+   ./zebra: error while loading shared libraries: libfrr.so.0: cannot open
+   shared object file: No such file or directory
+
+The fix is to add the following line to /etc/ld.so.conf which will
+continue to reference the library directory after the system reboots. To
+load the library directory path immediately run the ldconfig command
+after adding the line to the file eg:
+
+::
+
+   echo include /usr/local/lib >> /etc/ld.so.conf
+   ldconfig

doc/developer/subdir.am

@@ -11,6 +11,7 @@ dev_RSTFILES = \
 	doc/developer/building-frr-for-centos7.rst \
 	doc/developer/building-frr-for-debian8.rst \
 	doc/developer/building-frr-for-debian9.rst \
+	doc/developer/building-frr-for-debian12.rst \
 	doc/developer/building-frr-for-fedora.rst \
 	doc/developer/building-frr-for-freebsd10.rst \
 	doc/developer/building-frr-for-freebsd11.rst \