crit(proto-gen): move to Python script

Previously, CRIT was using an overengineered Makefile stunt to generate
protobuf bindings for the CLI. The problem of statically linking all the
bindings while using the library as a dependency cannot be resolved in a
reasonable manner in the Makefile. The logic has been moved out into a
Python script.

Signed-off-by: Prajwal S N <prajwalnadig21@gmail.com>

scripts/README.md

@@ -5,7 +5,20 @@ CRIU uses a 32-bit integer value to determine the type of image file. These valu
 
 `Usage: magicgen.go /path/to/magic.h /path/to/magic.go`
 
-A set of Makefile targets are provided for convenience:
+Makefile targets provided:
+
 - `make` or `make magic-gen`: Generate `../magic/magic.go`
 - `make test`: Run unit test and E2E test for `magicgen.go`
 - `make clean`: Remove `../magic/magic.go` and `magic.h`
+
+## `proto-gen`
+CRIT uses protobuf bindings to serialise and deserialise CRIU image files. The definitions for these bindings are available in [criu/images](https://github.com/checkpoint-restore/criu/tree/master/images). `protogen.py` fetches these definitions and generates the `.pb.go` files used by CRIT. If the source or destination directory is not provided, the script uses `../crit/images` by default.
+
+`Usage: protogen.py /path/to/definitions/dir /path/to/destination/dir`
+
+Makefile targets provided:
+
+- `make` or `make pb-gen`: Generate the `.pb.go` bindings
+- `make proto-update`: Update the `.proto` files with the latest copy from the CRIU repo. The GIT_BRANCH variable can be used to specify the branch to fetch the files from.
+- `make clean-proto`: Delete all `.proto` bindings
+- `make clean-pb`: Delete all `.pb.go` bindings

scripts/proto-gen/Makefile

@@ -0,0 +1,30 @@
+PY ?= python3
+PROTO_PATH ?= ../../crit/images
+PB_PATH ?= ../../crit/images
+GIT_BRANCH ?= master
+
+pb-gen: clean-pb
+	@$(PY) protogen.py $(PROTO_PATH) $(PB_PATH)
+
+proto-update: clean-proto
+	git clone --depth 1 --branch $(GIT_BRANCH) https://github.com/checkpoint-restore/criu criu-temp
+	cp criu-temp/images/*.proto $(PROTO_PATH)/
+	# rpc.proto is not an image and it is used only to communicate criu-service and swrk.
+	rm -rf criu-temp $(PROTO_PATH)/rpc.proto
+	# To prevent namespace conflict with proto files
+	# in github.com/letsencrypt/boulder, we prepend
+	# a prefix to the filenames.
+	mv $(PROTO_PATH)/sa.proto $(PROTO_PATH)/criu-sa.proto
+	sed -i 's/sa\.proto/criu-sa\.proto/g' $(PROTO_PATH)/*.proto
+	mv $(PROTO_PATH)/core.proto $(PROTO_PATH)/criu-core.proto
+	sed -i 's/core\.proto/criu-core\.proto/g' $(PROTO_PATH)/*.proto
+
+clean-proto:
+	@echo "Removing existing .proto files..."
+	rm $(PROTO_PATH)/*.proto || true
+
+clean-pb:
+	@echo "Removing existing .pb.go files..."
+	find $(PB_PATH) -type f -name '*.pb.go' -delete
+
+.PHONY: pb-gen proto-update clean-proto clean-pb

scripts/proto-gen/protogen.py

@@ -0,0 +1,45 @@
+import os
+import shutil
+import argparse
+import subprocess
+
+parser = argparse.ArgumentParser(
+    description='A script to generate Go bindings for the protobuf definitions provided by CRIU')
+parser.add_argument(
+    'src', help='Path to the definitions directory', type=str)
+parser.add_argument(
+    'dest', help='Path to the destination directory', type=str)
+
+args = parser.parse_args()
+
+# The import paths for each package passed to --go_opt
+pkg_opts = ''
+# The names of the .proto files without the extension
+names = []
+
+# Loop over the files in the src dir
+for file in os.listdir(args.src):
+    if file.endswith('.proto'):
+        # Strip the .proto extension
+        name = os.path.splitext(file)[0]
+        names.append(name)
+        # Add the import path for the protoc file
+        pkg_opts += ',M{0}.proto=github.com/checkpoint-restore/go-criu/v6/crit/images/{0}'.format(
+            name)
+
+# Create the dest dir
+if not os.path.exists(args.dest):
+    os.makedirs(args.dest)
+# Generate the .pb.go files
+command = 'protoc -I {} --go_opt=paths=source_relative{} --go_out={} {}'.format(
+    args.src, pkg_opts, args.dest, ' '.join(map(lambda s: os.path.join(args.src, s + '.proto'), names)))
+result = subprocess.run(command, shell=True)
+
+# Move the files to the respective dirs
+for name in names:
+    # Create dir with the same name as the file
+    dir_name = os.path.join(args.dest, name)
+    os.makedirs(dir_name, exist_ok=True)
+    # Move the generated .pb.go file from the dest dir
+    shutil.move(os.path.join(args.dest, name + '.pb.go'),
+                os.path.join(dir_name, name + '.pb.go'))