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| -rw-r--r-- | doc/developer/building.rst | 1 | ||||
| -rw-r--r-- | doc/developer/static-linking.rst | 98 | ||||
| -rw-r--r-- | doc/developer/subdir.am | 1 |
3 files changed, 100 insertions, 0 deletions
diff --git a/doc/developer/building.rst b/doc/developer/building.rst index b99667124..859f61231 100644 --- a/doc/developer/building.rst +++ b/doc/developer/building.rst @@ -7,6 +7,7 @@ Building FRR .. toctree:: :maxdepth: 2 + static-linking building-frr-for-alpine building-frr-for-centos6 building-frr-for-centos7 diff --git a/doc/developer/static-linking.rst b/doc/developer/static-linking.rst new file mode 100644 index 000000000..bc33207b3 --- /dev/null +++ b/doc/developer/static-linking.rst @@ -0,0 +1,98 @@ +.. _static-linking: + +Static Linking +============== + +This document describes how to build FRR without hard dependencies on shared +libraries. Note that it's not possible to build FRR *completely* statically. +This document just covers how to statically link the dependencies that aren't +likely to be present on a given platform - libfrr and libyang. The resultant +binaries should still be fairly portable. For example, here is the DSO +dependency list for `bgpd` after using these steps: + +.. code-block:: + + $ ldd bgpd + linux-vdso.so.1 (0x00007ffe3a989000) + libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f9dc10c0000) + libcap.so.2 => /lib/x86_64-linux-gnu/libcap.so.2 (0x00007f9dc0eba000) + libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f9dc0b1c000) + libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f9dc0918000) + libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007f9dc06e0000) + libjson-c.so.3 => /lib/x86_64-linux-gnu/libjson-c.so.3 (0x00007f9dc04d5000) + librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f9dc02cd000) + libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f9dc00ae000) + libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f9dbfe96000) + libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f9dbfaa5000) + /lib64/ld-linux-x86-64.so.2 (0x00007f9dc1449000) + +Procedure +--------- +Note that these steps have only been tested with LLVM 9 / clang. + +Today, libfrr can already be statically linked by passing these configure +options:: + + --enable-static --enable-static-bin --enable-shared + +libyang is more complicated. You must build and install libyang as a static +library. To do this, follow the usual libyang build procedure as listed in the +FRR developer docs, but set the ``ENABLE_STATIC`` option in your cmake +invocation. You also need to build with PIC enabled, which today is disabled +when building libyang statically. + +The resultant cmake command is:: + + cmake -DENABLE_STATIC=ON -DENABLE_LYD_PRIV=ON \ + -DCMAKE_INSTALL_PREFIX:PATH=/usr \ + -DCMAKE_POSITION_INDEPENDENT_CODE=TRUE \ + -DCMAKE_BUILD_TYPE:String="Release" .. + +This produces a bunch of ``.a`` static archives that need to ultimately be linked +into FRR. However, not only is it 6 archives rather than the usual ``libyang.so``, +you will now also need to link FRR with ``libpcre.a``. Ubuntu's ``libpcre3-dev`` +package provides this, but it hasn't been built with PIC enabled, so it's not +usable for our purposes. So download ``libpcre`` from +`SourceForge <https://sourceforge.net/projects/pcre/>`_, and build it +like this: + +.. code-block:: + + ./configure --with-pic + make + +Hopefully you get a nice, usable, PIC ``libpcre.a``. + +So now we have to link all these static libraries into FRR. Rather than modify +FRR to accomodate this, the best option is to create an archive with all of +libyang's dependencies. Then to avoid making any changes to FRR build foo, +rename this ``libyang.a`` and copy it over the usual static library location. +Ugly but it works. To do this, go into your libyang build directory, which +should have a bunch of ``.a`` files. Copy ``libpcre.a`` into this directory. +Write the following into a shell script and run it: + +.. code-block:: shell + + #!/bin/bash + ar -M <<EOM + CREATE libyang_fat.a + ADDLIB libyang.a + ADDLIB libyangdata.a + ADDLIB libmetadata.a + ADDLIB libnacm.a + ADDLIB libuser_inet_types.a + ADDLIB libuser_yang_types.a + ADDLIB libpcre.a + SAVE + END + EOM + ranlib libyang_fat.a + +``libyang_fat.a`` is your archive. Now copy this over your install +``libyang.a``, which on my machine is located at +``/usr/lib/x86_64-linux-gnu/libyang.a`` (try ``locate libyang.a`` if not). + +Now when you build FRR with the static options enabled as above, clang should +pick up the static libyang and link it, leaving you with FRR binaries that have +no hard DSO dependencies beyond common system libraries. To verify, run ``ldd`` +over the resultant binaries. diff --git a/doc/developer/subdir.am b/doc/developer/subdir.am index 2c49d6b87..791f7679a 100644 --- a/doc/developer/subdir.am +++ b/doc/developer/subdir.am @@ -44,6 +44,7 @@ dev_RSTFILES = \ doc/developer/packaging-redhat.rst \ doc/developer/packaging.rst \ doc/developer/rcu.rst \ + doc/developer/static-linking.rst \ doc/developer/testing.rst \ doc/developer/topotests-snippets.rst \ doc/developer/topotests.rst \ |