debian: structure for building backports from a single branch

Source a makefile (when it exists) in debian/rules to assemble
a source package via:

* a debian.tar.gz tarball built from combining the contents of debian/
  and debian/backports/$backport/debian/ using other details under
  debian/backports/$backport
* an orig.tar.gz file (not generated by this makefile). This can (and
  should) be the same for all backports.

Details in debian/backports/README

Signed-off-by: Silas McCroskey <smccroskey@cumulusnetworks.com>

5 files changed, 276 insertions, 0 deletions

diff --git a/debian/backports/.gitignore b/debian/backports/.gitignore
new file mode 100644
index 0000000000..3b20d26891
--- /dev/null
+++ b/debian/backports/.gitignore
@@ -0,0 +1,2 @@
+*/*.dirhash
+*/debian/changelog
diff --git a/debian/backports/README b/debian/backports/README
new file mode 100644
index 0000000000..efd322e1d9
--- /dev/null
+++ b/debian/backports/README
@@ -0,0 +1,28 @@
+This directory contains the debian directories for backports to other debian
+platforms.  These are built via the `3.0 (custom)' source format, which
+allows one to build a source package directly out of tarballs (e.g. an
+orig.tar.gz tarball and a debian.tar.gz file), at which point the format can
+be changed to a real format (e.g. `3.0 (quilt)').
+
+Source packages are assembled via targets of the same name as the system to
+which the backport is done (e.g. `precise'), included in debian/rules.
+
+To create a new debian backport:
+
+* Add its name to `KNOWN_BACKPORTS', defined in debian/rules.
+* Create a directory of the same name in debian/backports.
+* Add the files `exclude', `versionext', and `debian/source/format' under
+  this directory:
+  * `exclude' contains whitespace-separated paths (relative to the root of
+    the source dir) that should be excluded from the source package (e.g.
+    debian/patches).
+  * `versionext' contains the suffix added to the version number for this
+    backport's build.  Distributions often have guidelines for what this
+    should be. If left empty, no new debian/changelog entry is created.
+  * `debian/source/format' should contain the source format of the resulting
+    source package.  As of of the writing of this document the only supported
+    format is `3.0 (quilt)'.
+* Add appropriate files under the `debian/' subdirectory.  These will be
+  included in the source package, overriding any top-level `debian/' files
+  with equivalent paths.
+
diff --git a/debian/backports/rules b/debian/backports/rules
new file mode 100644
index 0000000000..3b8699754f
--- /dev/null
+++ b/debian/backports/rules
@@ -0,0 +1,129 @@
+.PHONY: backports $(KNOWN_BACKPORTS)
+
+# error out if these files are missing
+required_files = $(foreach backport,$(KNOWN_BACKPORTS), \
+	$(addprefix debian/backports/$(backport)/, \
+		debian/source/format \
+		versionext \
+		exclude))
+$(if $(filter-out $(wildcard $(required_files)),$(required_files)), \
+	$(error missing required backports files: \
+		$(filter-out $(wildcard $(required_files)),$(required_files)). \
+		see debian/backports/README) \
+)
+
+TARBALLDIR ?= $(shell dh_testdir debian/changelog && realpath ../)
+
+define backports-targets
+# if this file is empty, no automatic changelog entry is created
+VERSIONEXT_$(1) ?= $(strip \
+	$(shell cat $(wildcard debian/backports/$(1)/versionext)))
+DEBIAN_VERSION_$(1) = $(DEBIAN_VERSION)$$(VERSIONEXT_$(1))
+BACKPORTDIR_$(1) = $(realpath debian/backports/$(1))
+
+# as of right now, must be '3.0 (quilt)'
+SOURCEFORMAT_$(1) ?= $(strip \
+	$(shell cat debian/backports/$(1)/debian/source/format))
+
+# files checked for the dirhash (see below)
+FINDCMD_$(1) = find debian/backports/$(1)/debian \
+	-type f \
+	! -path debian/backports/$(1)/debian/changelog
+
+# files *not* pulled from the root debian directory into the backport tarball:
+# debian/changelog (copied and edited for backport version entry)
+# debian/backports itself (relevant contents are copied out separately)
+# anything provided in the current backports debian dir
+# anything specified in the 'exclude' file in the current backports debian dir
+EXCLUDEROOT_$(1) = debian/changelog debian/backports \
+	$$(subst debian/backports/$(1)/,,$$(shell $$(FINDCMD_$(1)))) \
+	$$(shell cat debian/backports/$(1)/exclude)
+
+EXCLUDEROOT_TAR_$(1) = $$(foreach file,$$(EXCLUDEROOT_$(1)),--exclude $$(file))
+EXCLUDEROOT_FIND_$(1) = $$(foreach file,$$(EXCLUDEROOT_$(1)),-o -path $$(file))
+
+# find command resulting in all files that *will* be pulled into the backport
+# tarball.
+FINDCMDROOT_$(1) = find debian/ \
+	'(' -false $$(EXCLUDEROOT_FIND_$(1)) ')' -prune -o \
+	-type f -a '!' '(' -false $$(EXCLUDEROOT_FIND_$(1)) ')'
+
+# usually using `find' output for dependencies has the downfall of not tracking
+# file removal. Work around that by introducing a dependency on a file whose
+# name contains the hash of `find' output, so that the name will change when a
+# file is deleted.
+DIRHASH_$(1) = \
+	$$(shell $$(FINDCMD_$(1)) | sha1sum | sed -r 's/^(......).*/\1/')
+DIRHASHROOT_$(1) = \
+	$$(shell $$(FINDCMDROOT_$(1)) | sha1sum | sed -r 's/^(......).*/\1/')
+
+CONTROL_$(1) = $$(strip \
+	$$(if $$(wildcard $$(BACKPORTDIR_$(1))/debian/control), \
+		$$(BACKPORTDIR_$(1))/debian/control, \
+		$(realpath debian/control) \
+	))
+
+# TARGETS:
+
+$(1): $(TARBALLDIR)/$(SRCPKG)_$$(DEBIAN_VERSION_$(1)).dsc ;
+
+# we use 3.0 (custom) to build a source package directly from tarballs,
+# bypassing the usual checks (which wouldn't like our combination-of-
+# directories approach)
+$(TARBALLDIR)/$(SRCPKG)_$$(DEBIAN_VERSION_$(1)).dsc:
+	# -b directory unused (but required) for '3.0 (custom)' source format
+	dpkg-source -l$$(BACKPORTDIR_$(1))/debian/changelog \
+		-c$$(CONTROL_$(1)) \
+		--format='3.0 (custom)' \
+		--target-format='$$(SOURCEFORMAT_$(1))' \
+		--build . $$^
+
+ifeq ($$(SOURCEFORMAT_$(1)),3.0 (quilt))
+# this target depends on the orig.tar.gz file, for which there is no target in
+# this makefile. It is assumed to either already exist or be built by a target
+# provided elsewhere in debian/rules (e.g. via pristine-tar)
+$(TARBALLDIR)/$(SRCPKG)_$$(DEBIAN_VERSION_$(1)).dsc: \
+		$(TARBALLDIR)/$(SRCPKG)_$(ORIG_VERSION).orig.tar.gz \
+		$(TARBALLDIR)/$(SRCPKG)_$$(DEBIAN_VERSION_$(1)).debian.tar.xz
+else
+$$(error unsupported source format for $(1) backport: $$(SOURCEFORMAT_$(1)))
+endif #SOURCEFORMAT_$(1)
+
+# for 3.0 (quilt)
+$(TARBALLDIR)/$(SRCPKG)_$$(DEBIAN_VERSION_$(1)).debian.tar.xz: \
+		$$(BACKPORTDIR_$(1))/debian/changelog \
+		$$(shell $$(FINDCMD_$(1))) \
+		$$(BACKPORTDIR_$(1))/$$(DIRHASH_$(1)).backport.dirhash \
+		$$(shell $$(FINDCMDROOT_$(1))) \
+		$$(BACKPORTDIR_$(1))/$$(DIRHASHROOT_$(1)).root.dirhash \
+		$$(BACKPORTDIR_$(1))/exclude
+	rm -f $$(subst .tar.xz,.tar,$$@) $$@
+	tar -cf $$(subst .tar.xz,.tar,$$@) \
+		--exclude-vcs $$(EXCLUDEROOT_TAR_$(1)) debian/
+	cd debian/backports/$(1) && tar -uf $$(subst .tar.xz,.tar,$$@) \
+		--exclude-vcs debian/
+	xz $$(subst .tar.xz,.tar,$$@)
+
+$$(BACKPORTDIR_$(1))/debian/changelog: \
+		debian/changelog \
+		debian/backports/$(1)/versionext
+	rm -f debian/backports/$(1)/debian/changelog
+	cp $$< $$@
+	$(if $$(VERSIONEXT_$(1)), \
+		dch -c $$@ -v '$$(DEBIAN_VERSION_$(1))' -b \
+			'backport to $(1) systems', \
+	)
+
+$$(BACKPORTDIR_$(1))/$$(DIRHASH_$(1)).backport.dirhash:
+	rm -f debian/backports/$(1)/*.backport.dirhash
+	touch $$@
+
+$$(BACKPORTDIR_$(1))/$$(DIRHASHROOT_$(1)).root.dirhash:
+	rm -f debian/backports/$(1)/*.root.dirhash
+	touch $$@
+
+endef # backports-targets
+$(foreach backport,$(KNOWN_BACKPORTS),$(eval \
+	$(call backports-targets,$(backport))))
+
+backports: $(KNOWN_BACKPORTS)
diff --git a/debian/rules b/debian/rules
index 5744505e64..8a13b1bcea 100755
--- a/debian/rules
+++ b/debian/rules
@@ -100,3 +100,22 @@ override_dh_systemd_start:
 override_dh_systemd_enable:
 	dh_systemd_enable frr.service
 
+# backports
+SRCPKG = frr
+KNOWN_BACKPORTS = ubuntu12.04 ubuntu14.04 ubuntu16.04
+ORIG_VERSION := $(shell dh_testdir && grep -E < configure.ac '^AC_INIT\(.*\)' \
+		| cut -d, -f2 | xargs echo)
+DEBIAN_VERSION := $(shell dh_testdir && \
+		dpkg-parsechangelog -c1 -Sversion < debian/changelog)
+-include debian/backports/rules
+
+ifneq ($(TARBALLDIR),)
+# better error message on missing .orig.tar.gz
+$(TARBALLDIR)/$(SRCPKG)_$(ORIG_VERSION).orig.tar.gz:
+	@ echo "\`$(TARBALLDIR)/$(SRCPKG)_$(ORIG_VERSION).orig.tar.gz'" not
+		found and not generated by debian/rules. Provided you have the \
+		necessary packages installed, you can generate it yourself via \
+		"\"./bootstrap.sh && ./configure && make dist\"" \
+		and renaming the resulting file.
+	exit 1
+endif # def TARBALLDIR
diff --git a/debian/rules.orig b/debian/rules.orig
new file mode 100755
index 0000000000..42c0d5f63a
--- /dev/null
+++ b/debian/rules.orig
@@ -0,0 +1,98 @@
+#!/usr/bin/make -f
+
+export DH_VERBOSE=1
+export DEB_BUILD_HARDENING=1
+export DH_OPTIONS=-v
+
+ifeq ($(WANT_SNMP), 1)
+  USE_SNMP=--enable-snmp
+  $(warning "DEBIAN: SNMP enabled, sorry for your inconvenience")
+else
+  $(warning "DEBIAN: SNMP disabled, see README.Debian")
+endif
+
+ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
+  DEBIAN_JOBS := $(subst parallel=,,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
+endif
+
+ifdef DEBIAN_JOBS
+MAKEFLAGS += -j$(DEBIAN_JOBS)
+endif
+
+%:
+	dh $@ --with=systemd,autoreconf --parallel --dbg-package=frr-dbg --list-missing
+
+override_dh_auto_configure:
+	# Frr needs /proc to check some BSD vs Linux specific stuff.
+	# Else it fails with an obscure error message pointing out that
+	# IPCTL_FORWARDING is an undefined symbol which is not very helpful.
+	@if ! [ -d /proc/1 ]; then \
+		echo "./configure needs a mounted /proc"; \
+		exit 1; \
+	fi
+
+	if ! [ -e config.status ]; then \
+	dh_auto_configure -- \
+		--enable-exampledir=/usr/share/doc/frr/examples/ \
+		--localstatedir=/var/run/frr \
+		--sbindir=/usr/lib/frr \
+		--sysconfdir=/etc/frr \
+		$(USE_SNMP) \
+		--enable-ospfapi=yes \
+		--enable-vtysh=yes \
+		--enable-isisd=yes \
+		--enable-multipath=256 \
+		--enable-user=frr \
+		--enable-group=frr \
+		--enable-vty-group=frrvty \
+		--enable-configfile-mask=0640 \
+		--enable-logfile-mask=0640 \
+		--enable-werror \
+		--enable-gcc-rdynamic \
+		--with-libpam \
+		--enable-systemd=yes \
+		--enable-poll=yes \
+		--enable-cumulus=yes \
+		--enable-pimd=yes \
+		--enable-dependency-tracking \
+		--enable-bgp-vnc=no; \
+	fi
+
+override_dh_auto_build:
+	#dh_auto_build
+	$(MAKE)
+	dh_auto_build -- -C doc draft-zebra-00.txt
+
+
+	# doc/ is a bit crazy
+ifeq ($(GENERATE_PDF), 1)
+	dh_auto_build -- -C doc frr.pdf || true # pdfetex fails with exit code 1 but still produces a good looking .pdf
+endif
+	rm -vf doc/frr.info
+	dh_auto_build -- -C doc frr.info
+	rm -vf doc/frr.info.html*
+
+override_dh_auto_test:
+
+override_dh_auto_install:
+	dh_auto_install
+
+	# cleaning up the info dir
+	rm -f debian/tmp/usr/share/info/dir*
+
+	# install config files
+	mkdir -p debian/tmp/etc/frr/
+	perl -pi -e 's#^!log file #!log file /var/log/frr/#' debian/tmp/usr/share/doc/frr/examples/*sample*
+
+	# installing the Frr specific SNMP MIB
+	install -D -m 644 ./zebra/GNOME-PRODUCT-ZEBRA-MIB debian/tmp/usr/share/snmp/mibs/GNOME-PRODUCT-ZEBRA-MIB
+
+	# cleaning .la files
+	sed -i "/dependency_libs/ s/'.*'/''/" debian/tmp/usr/lib/*.la
+
+override_dh_systemd_start:
+	dh_systemd_start frr.service
+
+override_dh_systemd_enable:
+	dh_systemd_enable frr.service
+