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6f29169e06
Fix documentation such that it is displayed as intended. Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
99 lines
4.0 KiB
ReStructuredText
99 lines
4.0 KiB
ReStructuredText
.. _static-linking:
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Static Linking
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==============
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This document describes how to build FRR without hard dependencies on shared
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libraries. Note that it's not possible to build FRR *completely* statically.
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This document just covers how to statically link the dependencies that aren't
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likely to be present on a given platform - libfrr and libyang. The resultant
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binaries should still be fairly portable. For example, here is the DSO
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dependency list for `bgpd` after using these steps:
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.. code-block:: shell
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$ ldd bgpd
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linux-vdso.so.1 (0x00007ffe3a989000)
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libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f9dc10c0000)
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libcap.so.2 => /lib/x86_64-linux-gnu/libcap.so.2 (0x00007f9dc0eba000)
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libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f9dc0b1c000)
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libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f9dc0918000)
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libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007f9dc06e0000)
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libjson-c.so.3 => /lib/x86_64-linux-gnu/libjson-c.so.3 (0x00007f9dc04d5000)
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librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f9dc02cd000)
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libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f9dc00ae000)
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libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f9dbfe96000)
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libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f9dbfaa5000)
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/lib64/ld-linux-x86-64.so.2 (0x00007f9dc1449000)
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Procedure
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---------
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Note that these steps have only been tested with LLVM 9 / clang.
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Today, libfrr can already be statically linked by passing these configure
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options::
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--enable-static --enable-static-bin --enable-shared
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libyang is more complicated. You must build and install libyang as a static
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library. To do this, follow the usual libyang build procedure as listed in the
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FRR developer docs, but set the ``ENABLE_STATIC`` option in your cmake
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invocation. You also need to build with PIC enabled, which today is disabled
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when building libyang statically.
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The resultant cmake command is::
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cmake -DENABLE_STATIC=ON -DENABLE_LYD_PRIV=ON \
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-DCMAKE_INSTALL_PREFIX:PATH=/usr \
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-DCMAKE_POSITION_INDEPENDENT_CODE=TRUE \
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-DCMAKE_BUILD_TYPE:String="Release" ..
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This produces a bunch of ``.a`` static archives that need to ultimately be linked
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into FRR. However, not only is it 6 archives rather than the usual ``libyang.so``,
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you will now also need to link FRR with ``libpcre.a``. Ubuntu's ``libpcre3-dev``
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package provides this, but it hasn't been built with PIC enabled, so it's not
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usable for our purposes. So download ``libpcre`` from
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`SourceForge <https://sourceforge.net/projects/pcre/>`_, and build it
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like this:
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.. code-block:: shell
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./configure --with-pic
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make
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Hopefully you get a nice, usable, PIC ``libpcre.a``.
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So now we have to link all these static libraries into FRR. Rather than modify
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FRR to accomodate this, the best option is to create an archive with all of
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libyang's dependencies. Then to avoid making any changes to FRR build foo,
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rename this ``libyang.a`` and copy it over the usual static library location.
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Ugly but it works. To do this, go into your libyang build directory, which
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should have a bunch of ``.a`` files. Copy ``libpcre.a`` into this directory.
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Write the following into a shell script and run it:
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.. code-block:: shell
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#!/bin/bash
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ar -M <<EOM
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CREATE libyang_fat.a
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ADDLIB libyang.a
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ADDLIB libyangdata.a
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ADDLIB libmetadata.a
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ADDLIB libnacm.a
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ADDLIB libuser_inet_types.a
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ADDLIB libuser_yang_types.a
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ADDLIB libpcre.a
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SAVE
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END
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EOM
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ranlib libyang_fat.a
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``libyang_fat.a`` is your archive. Now copy this over your install
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``libyang.a``, which on my machine is located at
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``/usr/lib/x86_64-linux-gnu/libyang.a`` (try ``locate libyang.a`` if not).
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Now when you build FRR with the static options enabled as above, clang should
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pick up the static libyang and link it, leaving you with FRR binaries that have
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no hard DSO dependencies beyond common system libraries. To verify, run ``ldd``
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over the resultant binaries.
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