diff --git a/bessctl/commands.py b/bessctl/commands.py
index 0d39867af..eb18836e4 100644
--- a/bessctl/commands.py
+++ b/bessctl/commands.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2014-2016, The Regents of the University of California.
+# Copyright (c) 2014-2017, The Regents of the University of California.
 # Copyright (c) 2016-2017, Nefeli Networks, Inc.
 # Copyright (c) 2017, Cloudigo.
 # All rights reserved.
@@ -333,7 +333,7 @@ def get_var_attrs(cli, var_token, partial_word):
             var_candidates = complete_filename(partial_word, suffix='.so',
                                                skip_suffix=True)
 
-        if var_token == '[DIRECTION]':
+        elif var_token == '[DIRECTION]':
             var_type = 'name'
             var_desc = 'gate direction discriminator (default "out")'
             var_candidates = ['in', 'out']
@@ -1417,12 +1417,22 @@ def show_mclass_list(cli, cls_names):
 
 @cmd('import plugin PLUGIN_FILE', 'Import the specified plugin (*.so)')
 def import_plugin(cli, plugin):
-    cli.bess.import_plugin(plugin)
+    cli.bess.pause_all()
+    try:
+        cli.bess.import_plugin(plugin)
+    finally:
+        cli.bess.resume_all()
 
 
 @cmd('unload plugin PLUGIN_FILE', 'Unload the specified plugin (*.so)')
 def unload_plugin(cli, plugin):
-    cli.bess.unload_plugin(plugin)
+    # FIXME check whether the plugin is being used
+    # currently this command can crash the BESS daemon
+    cli.bess.pause_all()
+    try:
+        cli.bess.unload_plugin(plugin)
+    finally:
+        cli.bess.resume_all()
 
 
 @cmd('show plugin', 'Show all imported plugins')
diff --git a/build.py b/build.py
index b5fe3ea26..c1184e98e 100755
--- a/build.py
+++ b/build.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 
-# Copyright (c) 2014-2016, The Regents of the University of California.
+# Copyright (c) 2014-2017, The Regents of the University of California.
 # Copyright (c) 2016-2017, Nefeli Networks, Inc.
 # All rights reserved.
 #
@@ -309,14 +309,14 @@ def build_bess():
 
     print('Generating protobuf codes for pybess...')
     cmd('protoc protobuf/*.proto \
-        --proto_path=protobuf --python_out=pybess \
-        --grpc_out=pybess \
+        --proto_path=protobuf --python_out=pybess/builtin_pb \
+        --grpc_out=pybess/builtin_pb \
         --plugin=protoc-gen-grpc=`which grpc_python_plugin`')
     cmd('protoc protobuf/tests/*.proto \
-        --proto_path=protobuf/tests/ --python_out=pybess \
-        --grpc_out=pybess \
+        --proto_path=protobuf/tests/ --python_out=pybess/builtin_pb \
+        --grpc_out=pybess/builtin_pb \
         --plugin=protoc-gen-grpc=`which grpc_python_plugin`')
-    cmd('2to3 -wn pybess/*_pb2.py')
+    cmd('2to3 -wn pybess/builtin_pb/*_pb2.py')
 
     print('Building BESS daemon...')
     cmd('bin/bessctl daemon stop 2> /dev/null || true')
@@ -355,7 +355,10 @@ def do_clean():
     cmd('make -C core clean')
     cmd('rm -f bin/bessd')
     cmd('make -C core/kmod clean')
-    cmd('rm -rf pybess/*_pb2.py')
+    cmd('rm -rf pybess/builtin_pb/*_pb2.py*')
+    cmd('rm -rf pybess/builtin_pb/*_pb2_grpc.py*')
+    cmd('rm -rf pybess/plugin_pb/*_pb2.py*')
+    cmd('rm -rf pybess/plugin_pb/*_pb2_grpc.py*')
     cmd('rm -rf %s/build' % DPDK_DIR)
 
 
@@ -403,7 +406,7 @@ def main():
         nargs=1,
         help='Location of benchmark library')
     parser.add_argument('-v', '--verbose', action='store_true',
-        help='enable verbose builds (same as env V=1)')
+                        help='enable verbose builds (same as env V=1)')
     args = parser.parse_args()
 
     if args.verbose:
diff --git a/core/Makefile b/core/Makefile
index 37a59c0cc..c0346b57a 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -1,4 +1,4 @@
-# Copyright (c) 2014-2016, The Regents of the University of California.
+# Copyright (c) 2014-2017, The Regents of the University of California.
 # Copyright (c) 2016-2017, Nefeli Networks, Inc.
 # All rights reserved.
 #
@@ -44,6 +44,7 @@ $(shell mkdir -p $(DEPDIR)/utils >/dev/null)
 $(shell mkdir -p $(DEPDIR)/modules >/dev/null)
 $(shell mkdir -p $(DEPDIR)/drivers >/dev/null)
 $(shell mkdir -p $(DEPDIR)/hooks >/dev/null)
+$(shell mkdir -p $(DEPDIR)/pb >/dev/null)
 
 # 'clang' or 'g++'
 CXXCOMPILER := $(shell expr $(word 1, $(shell $(CXX) --version)) : '\(clang\|g++\)')
@@ -52,7 +53,7 @@ CXXVERSION := $(shell $(CXX) -dumpversion)
 
 ifeq "$(CXXCOMPILER)" "g++"
 ifneq "$(shell printf '$(CXXVERSION)\n5' | sort -V | head -n1)" "5"
-    $(error g++ 5 or higher is required. Use container_build.py if newer g++ is not available.)
+$(error g++ 5 or higher is required. Use container_build.py if newer g++ is not available.)
 endif
 endif
 
@@ -127,10 +128,10 @@ endif
 
 PROTO_DIR := $(abspath ../protobuf)
 PROTOS := $(wildcard $(PROTO_DIR)/*.proto)
-PROTO_SRCS := $(patsubst %.proto,%.pb.cc, $(notdir $(PROTOS)))
-PROTO_SRCS += $(patsubst %.proto,%.grpc.pb.cc, $(notdir $(PROTOS)))
+PROTO_SRCS := $(patsubst %.proto,pb/%.pb.cc, $(notdir $(PROTOS)))
+PROTO_SRCS += $(patsubst %.proto,pb/%.grpc.pb.cc, $(notdir $(PROTOS)))
 PROTO_HEADERS := $(patsubst %.cc,%.h, $(PROTO_SRCS))
-PROTOCFLAGS += --proto_path=$(PROTO_DIR) --cpp_out=. --grpc_out=. --plugin=protoc-gen-grpc=`which grpc_cpp_plugin`
+PROTOCFLAGS += --proto_path=$(PROTO_DIR) --cpp_out=./pb --grpc_out=./pb --plugin=protoc-gen-grpc=`which grpc_cpp_plugin`
 
 ALL_SRCS := $(wildcard *.cc utils/*.cc modules/*.cc drivers/*.cc hooks/*.cc)
 
@@ -161,7 +162,7 @@ all: $(EXEC) modules tests benchmarks
 
 clean:
 	rm -rf $(EXEC) .deps/*.d .deps/*/*.d *_test */*_test *_bench */*_bench \
-		*.a *.pb.* *.o */*.o *.so */*.so *.gcov *.gcda *.gcno */*.gcda */*.gcno \
+		*.a pb/*.pb.* *.o */*.o *.so */*.so *.gcov *.gcda *.gcno */*.gcda */*.gcno \
 		coverage.info coverage_html
 
 tags:
@@ -218,14 +219,14 @@ endef
 
 $(eval $(call BUILD, \
 	PROTOC, \
-	%.pb.cc %.pb.h %.grpc.pb.cc %.grpc.pb.h, \
+	pb/%.pb.cc pb/%.pb.h pb/%.grpc.pb.cc pb/%.grpc.pb.h, \
 	$(PROTO_DIR)/%.proto, \
 	$(PROTOC) $$< $(PROTOCFLAGS)))
 
 $(eval $(call BUILD, \
 	CXX, \
-	%.pb.o, \
-	%.pb.cc, \
+	pb/%.pb.o, \
+	pb/%.pb.cc, \
 	$(CXX) -o $$@ -c $$< $(CXXFLAGS) $(PERMISSIVE) $$(DEPFLAGS)))
 
 $(eval $(call BUILD, \
diff --git a/core/bess_plugin.mk b/core/bess_plugin.mk
new file mode 100644
index 000000000..8eff94dff
--- /dev/null
+++ b/core/bess_plugin.mk
@@ -0,0 +1,116 @@
+# Copyright (c) 2017, The Regents of the University of California.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# * Redistributions of source code must retain the above copyright notice, this
+# list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright notice,
+# this list of conditions and the following disclaimer in the documentation
+# and/or other materials provided with the distribution.
+#
+# * Neither the names of the copyright holders nor the names of their
+# contributors may be used to endorse or promote products derived from this
+# software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+
+CXX ?= g++
+PROTOC ?= protoc
+
+# 'clang' or 'g++'
+CXXCOMPILER := $(shell expr $(word 1, $(shell $(CXX) --version)) : '\(clang\|g++\)')
+
+CXXVERSION := $(shell $(CXX) -dumpversion)
+
+
+ifeq "$(CXXCOMPILER)" "g++"
+ifneq "$(shell printf '$(CXXVERSION)\n5' | sort -V | head -n1)" "5"
+$(error g++ 5 or higher is required. Use container_build.py if newer g++ is not available.)
+endif
+endif
+
+RTE_SDK ?= $(BESS_HOME)/deps/dpdk-17.05
+RTE_TARGET ?= $(shell uname -m)-native-linuxapp-gcc
+DPDK_LIB ?= dpdk
+
+ifneq ($(wildcard $(RTE_SDK)/$(RTE_TARGET)/*),)
+	DPDK_INC_DIR := $(RTE_SDK)/$(RTE_TARGET)/include
+else ifneq ($(wildcard $(RTE_SDK)/build/*),)
+	# if the user didn't do "make install" for DPDK
+	DPDK_INC_DIR := $(RTE_SDK)/build/include
+else ifeq ($(words $(MAKECMDGOALS)),1)
+	ifneq ($(MAKECMDGOALS),clean)
+	$(error DPDK is not available. \
+		Make sure $(abspath $(RTE_SDK)) is available and built.)
+	endif
+endif
+
+BESS_INC_DIR := $(BESS_HOME)/core
+
+CXXARCHFLAGS ?= -march=native
+CXXFLAGS += -std=c++11 -g3 -ggdb3 $(CXXARCHFLAGS) \
+	    -Werror -isystem $(DPDK_INC_DIR) -isystem . -D_GNU_SOURCE \
+	    -isystem $(BESS_INC_DIR) \
+	    -Wall -Wextra -Wcast-align
+
+PERMISSIVE := -Wno-unused-parameter -Wno-missing-field-initializers \
+	      -Wno-unused-private-field
+
+# -Wshadow should not be used for g++ 4.x, as it has too many false positives
+ifeq "$(shell expr $(CXXCOMPILER) = g++ \& $(CXXVERSION) \< 50000)" "0"
+	CXXFLAGS += -Wshadow
+endif
+
+# Disable GNU_UNIQUE symbol for g++
+ifeq "$(shell expr $(CXXCOMPILER) = g++)" "1"
+	CXXFLAGS += -fno-gnu-unique
+endif
+
+ifdef SANITIZE
+	CXXFLAGS += -fsanitize=address -fsanitize=undefined -fno-omit-frame-pointer
+	LDFLAGS += -fsanitize=address -fsanitize=undefined
+endif
+
+ifdef DEBUG
+	CXXFLAGS += -O0
+else
+	CXXFLAGS += -Ofast -DNDEBUG
+endif
+
+PROTOCFLAGS += --proto_path=$(PROTO_DIR) \
+	       --cpp_out=$(PROTO_DIR) --grpc_out=$(PROTO_DIR) \
+	       --plugin=protoc-gen-grpc=$(shell which grpc_cpp_plugin)
+
+PROTOPYFLAGS += --proto_path=$(PROTO_DIR) \
+	        --python_out=$(PROTO_DIR) --grpc_out=$(PROTO_DIR) \
+	        --plugin=protoc-gen-grpc=$(shell which grpc_python_plugin)
+
+%.pb.o: %.pb.cc
+	$(CXX) -o $@ -c $< $(CXXFLAGS) $(PERMISSIVE) -fPIC
+
+%.pb.cc:
+	$(PROTOC) $< $(PROTOCFLAGS)
+
+%_pb2.py:
+	protoc $< $(PROTOPYFLAGS)
+	2to3 -wn $(PROTO_DIR)/*_pb2.py 2> /dev/null
+	mv $(PROTO_DIR)/*_pb2.py $(BESS_HOME)/pybess/plugin_pb/
+
+%.o: %.cc
+	$(CXX) -o $@ -c $^ $(CXXFLAGS) $(MODULE_CXXFLAGS) -fPIC
+
+%.so:
+	$(CXX) -shared -o $@ $^ $(LDFLAGS) $(MODULE_LDFLAGS)
diff --git a/core/bessctl.cc b/core/bessctl.cc
index d43d44cd6..ad948be90 100644
--- a/core/bessctl.cc
+++ b/core/bessctl.cc
@@ -40,7 +40,7 @@
 
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wunused-parameter"
-#include "service.grpc.pb.h"
+#include "pb/service.grpc.pb.h"
 #pragma GCC diagnostic pop
 
 #include "bessd.h"
diff --git a/core/bessd.cc b/core/bessd.cc
index 50e0ead0f..8273eff2b 100644
--- a/core/bessd.cc
+++ b/core/bessd.cc
@@ -411,11 +411,13 @@ std::vector<std::string> ListPlugins() {
 }
 
 bool LoadPlugin(const std::string &path) {
+  LOG(INFO) << "Loading module: " << path;
   void *handle = dlopen(path.c_str(), RTLD_NOW);
   if (handle != nullptr) {
     plugin_handles.emplace(path, handle);
     return true;
   }
+  LOG(WARNING) << "Error loading module " << path << ": " << dlerror();
   return false;
 }
 
@@ -443,10 +445,7 @@ bool LoadPlugins(const std::string &directory) {
   while ((entry = readdir(dir)) != nullptr) {
     if (entry->d_type == DT_REG && HasSuffix(entry->d_name, ".so")) {
       const std::string full_path = directory + "/" + entry->d_name;
-      LOG(INFO) << "Loading module: " << full_path;
       if (!LoadPlugin(full_path)) {
-        LOG(WARNING) << "Error loading module " << full_path << ": "
-                     << dlerror();
         closedir(dir);
         return false;
       }
diff --git a/core/message.h b/core/message.h
index b697bf9f2..4ced6c4c9 100644
--- a/core/message.h
+++ b/core/message.h
@@ -33,8 +33,9 @@
 #include <cstdarg>
 #include <functional>
 
-#include "bess_msg.pb.h"
-#include "error.pb.h"
+#include "pb/bess_msg.pb.h"
+#include "pb/error.pb.h"
+#include "pb/module_msg.pb.h"
 
 typedef bess::pb::Error pb_error_t;
 
diff --git a/core/modules/acl.h b/core/modules/acl.h
index 708820d3f..4597dcac2 100644
--- a/core/modules/acl.h
+++ b/core/modules/acl.h
@@ -33,7 +33,7 @@
 #include <vector>
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../utils/ip.h"
 
 using bess::utils::be16_t;
diff --git a/core/modules/arp_responder.h b/core/modules/arp_responder.h
index 2401f9ba0..367706efb 100644
--- a/core/modules/arp_responder.h
+++ b/core/modules/arp_responder.h
@@ -34,7 +34,7 @@
 #include <map>
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../utils/endian.h"
 #include "../utils/ether.h"
 #include "../utils/ip.h"
diff --git a/core/modules/bpf.h b/core/modules/bpf.h
index aa90c80ef..586a6898c 100644
--- a/core/modules/bpf.h
+++ b/core/modules/bpf.h
@@ -36,7 +36,7 @@
 #include <vector>
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 using bpf_filter_func_t = u_int (*)(u_char *, u_int, u_int);
 
diff --git a/core/modules/drr.h b/core/modules/drr.h
index 3f822d810..fc6eb6aa8 100644
--- a/core/modules/drr.h
+++ b/core/modules/drr.h
@@ -37,7 +37,7 @@
 
 #include "../kmod/llring.h"
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../pktbatch.h"
 #include "../utils/cuckoo_map.h"
 #include "../utils/ip.h"
diff --git a/core/modules/dump.h b/core/modules/dump.h
index 5bc385aaf..c7a2e8b47 100644
--- a/core/modules/dump.h
+++ b/core/modules/dump.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_DUMP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class Dump final : public Module {
  public:
diff --git a/core/modules/ether_encap.h b/core/modules/ether_encap.h
index 839a3f8ed..e15d39382 100644
--- a/core/modules/ether_encap.h
+++ b/core/modules/ether_encap.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_ETHERENCAP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class EtherEncap final : public Module {
  public:
diff --git a/core/modules/exact_match.h b/core/modules/exact_match.h
index eea909c21..7d1425d62 100644
--- a/core/modules/exact_match.h
+++ b/core/modules/exact_match.h
@@ -35,7 +35,7 @@
 #include <rte_hash_crc.h>
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../utils/cuckoo_map.h"
 
 #define MAX_FIELDS 8
diff --git a/core/modules/flowgen.h b/core/modules/flowgen.h
index 9fbd4ec5c..defb2303d 100644
--- a/core/modules/flowgen.h
+++ b/core/modules/flowgen.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_FLOWGEN_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 #include <queue>
 #include <stack>
diff --git a/core/modules/generic_decap.h b/core/modules/generic_decap.h
index 6b3341ebc..5e32273a3 100644
--- a/core/modules/generic_decap.h
+++ b/core/modules/generic_decap.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_GENERICDECAP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class GenericDecap final : public Module {
  public:
diff --git a/core/modules/generic_encap.h b/core/modules/generic_encap.h
index f8d4aeda2..cee15405e 100644
--- a/core/modules/generic_encap.h
+++ b/core/modules/generic_encap.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_GENERICENCAP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 #define MAX_FIELDS 8
 #define MAX_FIELD_SIZE 8
diff --git a/core/modules/hash_lb.h b/core/modules/hash_lb.h
index 0ca7cb210..904383293 100644
--- a/core/modules/hash_lb.h
+++ b/core/modules/hash_lb.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_HASHLB_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 #define MAX_HLB_GATES 16384
 
diff --git a/core/modules/ip_encap.h b/core/modules/ip_encap.h
index e63a6ae3c..592f92f18 100644
--- a/core/modules/ip_encap.h
+++ b/core/modules/ip_encap.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_IPENCAP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class IPEncap final : public Module {
  public:
diff --git a/core/modules/ip_lookup.h b/core/modules/ip_lookup.h
index 6ba4e1e6d..a43cef352 100644
--- a/core/modules/ip_lookup.h
+++ b/core/modules/ip_lookup.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_IPLOOKUP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class IPLookup final : public Module {
  public:
diff --git a/core/modules/l2_forward.h b/core/modules/l2_forward.h
index 4a749bf8f..49ce5e5fa 100644
--- a/core/modules/l2_forward.h
+++ b/core/modules/l2_forward.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_L2FORWARD_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 #if __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__
 #error this code assumes little endian architecture (x86)
diff --git a/core/modules/measure.h b/core/modules/measure.h
index eeb768fd9..4b7c6d3ef 100644
--- a/core/modules/measure.h
+++ b/core/modules/measure.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_MEASURE_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../utils/histogram.h"
 #include "../utils/random.h"
 
diff --git a/core/modules/mpls_pop.h b/core/modules/mpls_pop.h
index 45e43cfc9..d5ffd6954 100644
--- a/core/modules/mpls_pop.h
+++ b/core/modules/mpls_pop.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_MPLSPOP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../utils/ether.h"
 
 using bess::utils::be16_t;
diff --git a/core/modules/mttest.h b/core/modules/mttest.h
index a59c1a531..7f97b3e4a 100644
--- a/core/modules/mttest.h
+++ b/core/modules/mttest.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_MTTEST_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 using bess::metadata::Attribute;
 
diff --git a/core/modules/nat.h b/core/modules/nat.h
index 0dd5eb607..322ba8aba 100644
--- a/core/modules/nat.h
+++ b/core/modules/nat.h
@@ -31,7 +31,7 @@
 #define BESS_MODULES_NAT_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 #include <rte_config.h>
 #include <rte_hash_crc.h>
diff --git a/core/modules/noop.h b/core/modules/noop.h
index 9d9f75173..d328b7616 100644
--- a/core/modules/noop.h
+++ b/core/modules/noop.h
@@ -32,13 +32,11 @@
 #define BESS_MODULES_NOOP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class NoOP final : public Module {
  public:
-  NoOP() : Module() {
-    is_task_ = true;
-  };
+  NoOP() : Module() { is_task_ = true; };
   CommandResponse Init(const bess::pb::EmptyArg &arg);
 
   struct task_result RunTask(void *arg) override;
diff --git a/core/modules/port_inc.h b/core/modules/port_inc.h
index 3c146f1ae..d43090410 100644
--- a/core/modules/port_inc.h
+++ b/core/modules/port_inc.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_PORTINC_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../port.h"
 
 class PortInc final : public Module {
@@ -41,9 +41,7 @@ class PortInc final : public Module {
 
   static const Commands cmds;
 
-  PortInc() : Module(), port_(), prefetch_(), burst_() {
-    is_task_ = true;
-  }
+  PortInc() : Module(), port_(), prefetch_(), burst_() { is_task_ = true; }
 
   CommandResponse Init(const bess::pb::PortIncArg &arg);
 
diff --git a/core/modules/port_out.h b/core/modules/port_out.h
index 323ab51fe..49e48cb9b 100644
--- a/core/modules/port_out.h
+++ b/core/modules/port_out.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_PORTOUT_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../port.h"
 
 class PortOut final : public Module {
diff --git a/core/modules/queue.h b/core/modules/queue.h
index e93d3708d..91a3cd53c 100644
--- a/core/modules/queue.h
+++ b/core/modules/queue.h
@@ -33,7 +33,7 @@
 
 #include "../kmod/llring.h"
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class Queue final : public Module {
  public:
diff --git a/core/modules/queue_inc.h b/core/modules/queue_inc.h
index 89a07ebdc..14508637d 100644
--- a/core/modules/queue_inc.h
+++ b/core/modules/queue_inc.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_QUEUEINC_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../port.h"
 
 class QueueInc final : public Module {
diff --git a/core/modules/queue_out.h b/core/modules/queue_out.h
index ee208a02b..b0318a9e6 100644
--- a/core/modules/queue_out.h
+++ b/core/modules/queue_out.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_QUEUEOUT_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../port.h"
 
 class QueueOut final : public Module {
diff --git a/core/modules/random_drop.h b/core/modules/random_drop.h
index b2522ca5f..79fed79e3 100644
--- a/core/modules/random_drop.h
+++ b/core/modules/random_drop.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_RANDOM_DROP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../utils/random.h"
 
 // RandomDrop drops packets with a specified probability [0, 1].
diff --git a/core/modules/random_update.cc b/core/modules/random_update.cc
index 1fb3d1d69..694c656ec 100644
--- a/core/modules/random_update.cc
+++ b/core/modules/random_update.cc
@@ -44,10 +44,10 @@ CommandResponse RandomUpdate::Init(const bess::pb::RandomUpdateArg &arg) {
 }
 
 CommandResponse RandomUpdate::CommandAdd(const bess::pb::RandomUpdateArg &arg) {
-  int curr = num_vars_;
-  if (curr + arg.fields_size() > MAX_VARS) {
-    return CommandFailure(EINVAL, "max %d variables can be specified",
-                          MAX_VARS);
+  size_t curr = num_vars_;
+  if (curr + arg.fields_size() > kMaxVariable) {
+    return CommandFailure(EINVAL, "max %zu variables can be specified",
+                          kMaxVariable);
   }
 
   for (int i = 0; i < arg.fields_size(); i++) {
@@ -116,7 +116,7 @@ CommandResponse RandomUpdate::CommandClear(const bess::pb::EmptyArg &) {
 void RandomUpdate::ProcessBatch(bess::PacketBatch *batch) {
   int cnt = batch->cnt();
 
-  for (int i = 0; i < num_vars_; i++) {
+  for (size_t i = 0; i < num_vars_; i++) {
     const auto var = &vars_[i];
 
     be32_t mask = var->mask;
diff --git a/core/modules/random_update.h b/core/modules/random_update.h
index e06415f29..2ba38ecbe 100644
--- a/core/modules/random_update.h
+++ b/core/modules/random_update.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2014-2016, The Regents of the University of California.
+// Copyright (c) 2014-2017, The Regents of the University of California.
 // Copyright (c) 2016-2017, Nefeli Networks, Inc.
 // All rights reserved.
 //
@@ -32,12 +32,12 @@
 #define BESS_MODULES_RANDOMUPDATE_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 #include "../utils/endian.h"
 #include "../utils/random.h"
 
-#define MAX_VARS 16
+static const size_t kMaxVariable = 16;
 
 class RandomUpdate final : public Module {
  public:
@@ -53,7 +53,7 @@ class RandomUpdate final : public Module {
   CommandResponse CommandClear(const bess::pb::EmptyArg &arg);
 
  private:
-  int num_vars_;
+  size_t num_vars_;
 
   struct {
     bess::utils::be32_t mask;  // bits with 1 won't be updated
@@ -61,7 +61,7 @@ class RandomUpdate final : public Module {
     uint32_t range;  // max - min + 1
     size_t offset;
     size_t bit_shift;
-  } vars_[MAX_VARS];
+  } vars_[kMaxVariable];
 
   Random rng_;
 };
diff --git a/core/modules/replicate.h b/core/modules/replicate.h
index 1df1141d6..3ac21d36d 100644
--- a/core/modules/replicate.h
+++ b/core/modules/replicate.h
@@ -31,7 +31,7 @@
 #define BESS_MODULES_REPLICATE_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class Replicate final : public Module {
  public:
diff --git a/core/modules/rewrite.h b/core/modules/rewrite.h
index 36536dba7..931e63efa 100644
--- a/core/modules/rewrite.h
+++ b/core/modules/rewrite.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_REWRITE_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class Rewrite final : public Module {
  public:
diff --git a/core/modules/round_robin.h b/core/modules/round_robin.h
index 4021a493c..ed9a1a183 100644
--- a/core/modules/round_robin.h
+++ b/core/modules/round_robin.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_ROUNDROBIN_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 /*!
  * TODO: RoundRobin currently does not support multiple workers.
diff --git a/core/modules/set_metadata.h b/core/modules/set_metadata.h
index a081bf626..e7a560e20 100644
--- a/core/modules/set_metadata.h
+++ b/core/modules/set_metadata.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_SETMETADATA_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 typedef struct { char bytes[bess::metadata::kMetadataAttrMaxSize]; } value_t;
 
diff --git a/core/modules/source.h b/core/modules/source.h
index 7272d78c9..5b6893048 100644
--- a/core/modules/source.h
+++ b/core/modules/source.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_FLOWGEN_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class Source final : public Module {
  public:
@@ -40,9 +40,7 @@ class Source final : public Module {
 
   static const Commands cmds;
 
-  Source() : Module(), pkt_size_(), burst_() {
-    is_task_ = true;
-  }
+  Source() : Module(), pkt_size_(), burst_() { is_task_ = true; }
 
   CommandResponse Init(const bess::pb::SourceArg &arg);
 
diff --git a/core/modules/split.h b/core/modules/split.h
index 94a4640bc..6a0ccab8e 100644
--- a/core/modules/split.h
+++ b/core/modules/split.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_SPLIT_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class Split final : public Module {
  public:
diff --git a/core/modules/timestamp.h b/core/modules/timestamp.h
index ab1f6169b..3f1ed7b5f 100644
--- a/core/modules/timestamp.h
+++ b/core/modules/timestamp.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_TIMESTAMP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class Timestamp final : public Module {
  public:
diff --git a/core/modules/update.h b/core/modules/update.h
index c43082b1b..440f7a259 100644
--- a/core/modules/update.h
+++ b/core/modules/update.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_UPDATE_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 #include "../utils/endian.h"
 
diff --git a/core/modules/url_filter.h b/core/modules/url_filter.h
index 1848e9f87..afbcfb784 100644
--- a/core/modules/url_filter.h
+++ b/core/modules/url_filter.h
@@ -39,8 +39,8 @@
 #include <vector>
 
 #include "../module.h"
-#include "../module_msg.pb.h"
 #include "../packet.h"
+#include "../pb/module_msg.pb.h"
 #include "../utils/tcp_flow_reconstruct.h"
 #include "../utils/trie.h"
 
diff --git a/core/modules/vlan_push.h b/core/modules/vlan_push.h
index 8e7a5250d..29310cfc7 100644
--- a/core/modules/vlan_push.h
+++ b/core/modules/vlan_push.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_VLANPUSH_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 #include "../utils/endian.h"
 
diff --git a/core/modules/vxlan_decap.h b/core/modules/vxlan_decap.h
index 766f7418d..f5b50bc04 100644
--- a/core/modules/vxlan_decap.h
+++ b/core/modules/vxlan_decap.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_VXLANDECAP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 class VXLANDecap final : public Module {
  public:
diff --git a/core/modules/vxlan_encap.h b/core/modules/vxlan_encap.h
index adc752eba..529542314 100644
--- a/core/modules/vxlan_encap.h
+++ b/core/modules/vxlan_encap.h
@@ -32,7 +32,7 @@
 #define BESS_MODULES_VXLANENCAP_H_
 
 #include "../module.h"
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 
 #include "../utils/endian.h"
 
diff --git a/core/modules/wildcard_match.h b/core/modules/wildcard_match.h
index 5ed681e94..1dadffc8d 100644
--- a/core/modules/wildcard_match.h
+++ b/core/modules/wildcard_match.h
@@ -36,7 +36,7 @@
 #include <rte_config.h>
 #include <rte_hash_crc.h>
 
-#include "../module_msg.pb.h"
+#include "../pb/module_msg.pb.h"
 #include "../utils/cuckoo_map.h"
 
 using bess::utils::HashResult;
diff --git a/core/pb/.gitignore b/core/pb/.gitignore
new file mode 100644
index 000000000..f935021a8
--- /dev/null
+++ b/core/pb/.gitignore
@@ -0,0 +1 @@
+!.gitignore
diff --git a/core/port.h b/core/port.h
index 29d18977c..410ad1ea6 100644
--- a/core/port.h
+++ b/core/port.h
@@ -43,7 +43,7 @@
 #include "message.h"
 #include "module.h"
 #include "packet.h"
-#include "port_msg.pb.h"
+#include "pb/port_msg.pb.h"
 #include "utils/common.h"
 
 typedef uint8_t queue_t;
diff --git a/protobuf/bess_msg.proto b/protobuf/bess_msg.proto
index 80303f23a..b182c7859 100644
--- a/protobuf/bess_msg.proto
+++ b/protobuf/bess_msg.proto
@@ -1,4 +1,5 @@
 // Copyright (c) 2016-2017, Nefeli Networks, Inc.
+// Copyright (c) 2017, The Regents of the University of California.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -41,9 +42,6 @@ import "error.proto";
 
 package bess.pb;
 
-message EmptyArg {
-}
-
 message EmptyRequest {
 }
 
diff --git a/protobuf/module_msg.proto b/protobuf/module_msg.proto
index f6499e5fd..539f92cc5 100644
--- a/protobuf/module_msg.proto
+++ b/protobuf/module_msg.proto
@@ -1,4 +1,5 @@
 // Copyright (c) 2016-2017, Nefeli Networks, Inc.
+// Copyright (c) 2017, The Regents of the University of California.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -46,6 +47,8 @@ import "util_msg.proto";
 /// is called on modules in bessd. This file lists all modules, their initialization parameters
 /// and any functions that may be called on them.
 
+message EmptyArg {
+}
 
 /**
  * The BPF module has a command `clear()` that takes no parameters.
@@ -735,8 +738,8 @@ message RandomDropArg {
 }
 
 /**
- * The RandomUpdate module rewrites a random field in a packet with a random value
- * between a specified min and max values.
+ * The RandomUpdate module rewrites a specified field (`offset` and `size`) in a packet
+ * with a random value between a specified min and max values.
  *
  * __Input Gates__: 1
  * __Output Gates__: 1
diff --git a/pybess/bess.py b/pybess/bess.py
index fafe498f4..5c53d3575 100644
--- a/pybess/bess.py
+++ b/pybess/bess.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2014-2016, The Regents of the University of California.
+# Copyright (c) 2014-2017, The Regents of the University of California.
 # Copyright (c) 2016-2017, Nefeli Networks, Inc.
 # Copyright (c) 2017, Cloudigo.
 # All rights reserved.
@@ -38,12 +38,14 @@
 import pprint
 import time
 
-from . import service_pb2
 from . import protobuf_to_dict as pb_conv
 
-from . import module_msg
-from . import bess_msg_pb2 as bess_msg
-from . import port_msg_pb2 as port_msg
+from . import module_pb_loader as module_pb
+
+from .builtin_pb import service_pb2
+from .builtin_pb import bess_msg_pb2 as bess_msg
+from .builtin_pb import module_msg_pb2 as module_msg
+from .builtin_pb import port_msg_pb2 as port_msg
 
 
 def _constraints_to_list(constraint):
@@ -294,7 +296,7 @@ def create_port(self, driver, name=None, arg=None):
         request.size_out_q = arg.pop('size_out_q', 0)
         request.mac_addr = arg.pop('mac_addr', '')
 
-        message_type = getattr(port_msg, driver + 'Arg', bess_msg.EmptyArg)
+        message_type = getattr(port_msg, driver + 'Arg', module_msg.EmptyArg)
         arg_msg = pb_conv.dict_to_protobuf(message_type, arg)
         request.arg.Pack(arg_msg)
 
@@ -349,7 +351,7 @@ def create_module(self, mclass, name=None, arg=None):
         request.name = name or ''
         request.mclass = mclass
 
-        message_type = getattr(module_msg, mclass + 'Arg', bess_msg.EmptyArg)
+        message_type = getattr(module_pb, mclass + 'Arg', module_msg.EmptyArg)
         arg_msg = pb_conv.dict_to_protobuf(message_type, arg)
         request.arg.Pack(arg_msg)
 
@@ -385,7 +387,7 @@ def run_module_command(self, name, cmd, arg_type, arg):
         request.cmd = cmd
 
         try:
-            message_type = getattr(module_msg, arg_type)
+            message_type = getattr(module_pb, arg_type)
         except AttributeError as e:
             raise self.APIError('Unknown arg "%s"' % arg_type)
 
@@ -404,8 +406,8 @@ def run_module_command(self, name, cmd, arg_type, arg):
 
         if response.HasField('data'):
             response_type_str = response.data.type_url.split('.')[-1]
-            response_type = getattr(module_msg, response_type_str,
-                                    bess_msg.EmptyArg)
+            response_type = getattr(module_pb, response_type_str,
+                                    module_msg.EmptyArg)
             result = response_type()
             response.data.Unpack(result)
             return result
diff --git a/pybess/builtin_pb/__init__.py b/pybess/builtin_pb/__init__.py
new file mode 100644
index 000000000..8b1378917
--- /dev/null
+++ b/pybess/builtin_pb/__init__.py
@@ -0,0 +1 @@
+
diff --git a/pybess/module_pb_loader.py b/pybess/module_pb_loader.py
new file mode 100644
index 000000000..2a2ba7253
--- /dev/null
+++ b/pybess/module_pb_loader.py
@@ -0,0 +1,65 @@
+# Copyright (c) 2014-2017, The Regents of the University of California.
+# Copyright (c) 2016-2017, Nefeli Networks, Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# * Redistributions of source code must retain the above copyright notice, this
+# list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright notice,
+# this list of conditions and the following disclaimer in the documentation
+# and/or other materials provided with the distribution.
+#
+# * Neither the names of the copyright holders nor the names of their
+# contributors may be used to endorse or promote products derived from this
+# software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+
+import importlib
+import glob
+import os
+
+__all__ = []
+
+blacklist = ['builtin_pb.bess_msg_pb2', 'builtin_pb.port_msg_pb2']
+
+
+def update_symbols(module, symbols):
+    globals().update({name: module.__dict__[name] for name in symbols})
+
+
+def import_module(module_name, update_symbol=True):
+    module = importlib.import_module('..' + module_name, __name__)
+    symbols = [n for n in module.__dict__ if
+               n.endswith('Arg') or n.endswith('Response')]
+
+    if update_symbol:
+        update_symbols(module, symbols)
+
+
+def import_package(package_name):
+    cur_path = os.path.dirname(os.path.relpath(__file__))
+    module_files = glob.glob(cur_path + '/' + package_name + '/*_msg_pb2.py')
+    modules = [package_name + '.' + m
+               for m in [os.path.basename(m)[:-3] for m in module_files]]
+
+    for module_name in modules:
+        if module_name not in blacklist:
+            import_module(module_name)
+
+import_package('builtin_pb')
+import_package('plugin_pb')
+import_module('builtin_pb.bess_msg_pb2', False)
diff --git a/pybess/plugin_pb/__init__.py b/pybess/plugin_pb/__init__.py
new file mode 100644
index 000000000..8b1378917
--- /dev/null
+++ b/pybess/plugin_pb/__init__.py
@@ -0,0 +1 @@
+
diff --git a/pybess/test_bess.py b/pybess/test_bess.py
index 0ea8cec20..1559fd677 100644
--- a/pybess/test_bess.py
+++ b/pybess/test_bess.py
@@ -35,8 +35,8 @@
 from concurrent import futures
 
 from . import bess
-from . import bess_msg_pb2 as bess_msg
-from . import service_pb2
+from .builtin_pb import bess_msg_pb2 as bess_msg
+from .builtin_pb import service_pb2
 
 
 class DummyServiceImpl(service_pb2.BESSControlServicer):
@@ -141,5 +141,5 @@ def test_run_module_command(self):
                                              'add',
                                              'ExactMatchCommandAddArg',
                                              {'gate': 0,
-                                                 'fields': [{'value_bin':b'\x11'}, {'value_bin':b'\x22'}]})
+                                                 'fields': [{'value_bin': b'\x11'}, {'value_bin': b'\x22'}]})
         self.assertEqual(0, response.error.code)
diff --git a/pybess/test_protobuf_to_dict.py b/pybess/test_protobuf_to_dict.py
index 96c4e2576..229d4ef28 100644
--- a/pybess/test_protobuf_to_dict.py
+++ b/pybess/test_protobuf_to_dict.py
@@ -30,9 +30,9 @@
 
 from __future__ import absolute_import
 import unittest
-from . import bess_msg_pb2 as bess_msg
 from . import protobuf_to_dict as pb_conv
-from . import test_msg_pb2 as test_msg
+from .builtin_pb import bess_msg_pb2 as bess_msg
+from .builtin_pb import test_msg_pb2 as test_msg
 
 
 class TestProtobufConvert(unittest.TestCase):
diff --git a/sample_plugin/Makefile b/sample_plugin/Makefile
new file mode 100644
index 000000000..c57a1d92a
--- /dev/null
+++ b/sample_plugin/Makefile
@@ -0,0 +1,47 @@
+# BESS must be already built.
+# Set your BESS_HOME environment variable to that directory.
+#BESS_HOME ?= /your/bess/home
+
+ifeq ($(BESS_HOME),)
+$(error BESS_HOME is not defined.)
+endif
+
+# Library target
+target_a := modules/sequential_update.so
+# Objects for the target
+objects_a := modules/sequential_update.o
+
+# Add all your targets here
+all: $(target_a) # $(target_b) ...
+
+# You can specify per-target flags like this
+#$(target): LDFLAGS+=
+
+# Protobuf file location in 'absolute path'
+protobuf := $(abspath protobuf/supdate_msg.proto)
+
+#### You don't need to modify from here ####
+proto_h := $(patsubst %.proto,%.pb.h, $(protobuf)) \
+	   $(patsubst %.proto,%.grpc.pb.h, $(protobuf))
+proto_cc := $(patsubst %.proto,%.pb.cc, $(protobuf)) \
+	    $(patsubst %.proto,%.grpc.pb.cc, $(protobuf))
+proto_o := $(patsubst %.cc,%.o, $(proto_cc))
+proto_py := $(patsubst %.proto, %_pb2.py, $(protobuf)) \
+	    $(patsubst %.proto, %_pb2_grpc.py, $(protobuf))
+
+$(proto_cc): $(protobuf) $(proto_py)
+$(proto_cc): PROTO_DIR=$(dir $(protobuf))
+$(proto_py): $(protobuf)
+$(proto_py): PROTO_DIR=$(dir $(protobuf))
+####             up to here            ####
+
+# Mapping between target library, protobuf, objects
+# protobuf objects should appear before objects
+$(target_a): $(proto_o) $(objects_a)
+# $(target_b): $(proto_o) $(objects_b)
+
+clean:
+	rm -f $(proto_o) $(proto_cc) $(proto_h) $(proto_py) \
+		$(target_a) $(objects_a)
+
+include $(BESS_HOME)/core/bess_plugin.mk
diff --git a/pybess/module_msg.py b/sample_plugin/bessctl_conf/sequential_update.bess
similarity index 63%
rename from pybess/module_msg.py
rename to sample_plugin/bessctl_conf/sequential_update.bess
index eec0cc4fa..d5e12db6b 100644
--- a/pybess/module_msg.py
+++ b/sample_plugin/bessctl_conf/sequential_update.bess
@@ -1,4 +1,4 @@
-# Copyright (c) 2014-2016, The Regents of the University of California.
+# Copyright (c) 2014-2017, The Regents of the University of California.
 # Copyright (c) 2016-2017, Nefeli Networks, Inc.
 # All rights reserved.
 #
@@ -28,35 +28,24 @@
 # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 # POSSIBILITY OF SUCH DAMAGE.
 
-import importlib
-import glob
-import os
+import scapy.all as scapy
 
-exclude_list = ['bess_msg_pb2', 'port_msg_pb2']
+eth = scapy.Ether(src='02:1e:67:9f:4d:ae', dst='06:16:3e:1b:72:32')
+ip = scapy.IP(src='192.168.1.1', dst='10.0.0.1')
+udp = scapy.UDP(sport=10001, dport=10002)
+payload = 'helloworld'
+pkt_bytes = bytes(eth/ip/udp/payload)
 
+Source() -> Rewrite(templates=[pkt_bytes]) -> rr::RoundRobin(gates=[1, 2])
 
-def _load_symbols(mod, *symbols):
-    globals().update({name: mod.__dict__[name] for name in symbols})
+# src MAC address
+rr:1 \
+    -> Update(fields=[{'offset': 6, 'size': 6, 'value': 0x1234567890ab}]) \
+    -> Sink()
 
+# UDP src/dst ports
+rr:2 \
+    -> su::SequentialUpdate(fields=[{'offset': 34, 'size': 2, 'min': 20000, 'max': 30000}]) \
+    -> Sink()
 
-def load_symbol(mod_name, symbol):
-    mod = importlib.import_module('..' + mod_name, __name__)
-    _load_symbols(mod, symbol)
-
-
-def load_symbols(mod_name):
-    mod = importlib.import_module('..' + mod_name, __name__)
-    symbols = [n for n in mod.__dict__ if
-               n.endswith('Arg') or n.endswith('Response')]
-    _load_symbols(mod, *symbols)
-
-
-dir_path = os.path.dirname(os.path.realpath(__file__))
-mod_files = glob.glob(dir_path + '/*_msg_pb2.py')
-mods = [m for m in [os.path.basename(m)[:-3] for m in mod_files]
-        if m not in exclude_list]
-
-for mod_name in mods:
-    load_symbols(mod_name)
-
-load_symbol('bess_msg_pb2', 'EmptyArg')
+su.add(fields=[{'offset': 36, 'size': 2, 'min': 40000, 'max': 50000}])
diff --git a/sample_plugin/modules/sequential_update.cc b/sample_plugin/modules/sequential_update.cc
new file mode 100644
index 000000000..a0358ac5a
--- /dev/null
+++ b/sample_plugin/modules/sequential_update.cc
@@ -0,0 +1,150 @@
+// Copyright (c) 2014-2017, The Regents of the University of California.
+// Copyright (c) 2016-2017, Nefeli Networks, Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice, this
+// list of conditions and the following disclaimer.
+//
+// * Redistributions in binary form must reproduce the above copyright notice,
+// this list of conditions and the following disclaimer in the documentation
+// and/or other materials provided with the distribution.
+//
+// * Neither the names of the copyright holders nor the names of their
+// contributors may be used to endorse or promote products derived from this
+// software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+#include "sequential_update.h"
+
+using bess::utils::be32_t;
+
+const Commands SequentialUpdate::cmds = {
+    {"add", "SequentialUpdateArg",
+     MODULE_CMD_FUNC(&SequentialUpdate::CommandAdd), Command::THREAD_UNSAFE},
+    {"clear", "EmptyArg", MODULE_CMD_FUNC(&SequentialUpdate::CommandClear),
+     Command::THREAD_UNSAFE},
+};
+
+CommandResponse
+SequentialUpdate::Init(const sample::supdate::pb::SequentialUpdateArg &arg) {
+  return CommandAdd(arg);
+}
+
+CommandResponse SequentialUpdate::CommandAdd(
+    const sample::supdate::pb::SequentialUpdateArg &arg) {
+  size_t curr = num_vars_;
+  if (curr + arg.fields_size() > kMaxVariable) {
+    return CommandFailure(EINVAL, "max %zu variables can be specified",
+                          kMaxVariable);
+  }
+
+  for (int i = 0; i < arg.fields_size(); i++) {
+    const auto &var = arg.fields(i);
+
+    size_t size;
+    size_t offset;
+    be32_t mask;
+    uint32_t min;
+    uint32_t max;
+
+    offset = var.offset();
+    size = var.size();
+    min = var.min();
+    max = var.max();
+
+    switch (size) {
+    case 1:
+      mask = be32_t(0x00ffffff);
+      min = std::min(min, static_cast<uint32_t>(0xff));
+      max = std::min(max, static_cast<uint32_t>(0xff));
+      break;
+
+    case 2:
+      mask = be32_t(0x0000ffff);
+      min = std::min(min, static_cast<uint32_t>(0xffff));
+      max = std::min(max, static_cast<uint32_t>(0xffff));
+      break;
+
+    case 4:
+      mask = be32_t(0x00000000);
+      min = std::min(min, static_cast<uint32_t>(0xffffffffu));
+      max = std::min(max, static_cast<uint32_t>(0xffffffffu));
+      break;
+
+    default:
+      return CommandFailure(EINVAL, "'size' must be 1, 2, or 4");
+    }
+
+    if (offset + size > SNBUF_DATA) {
+      return CommandFailure(EINVAL, "too large 'offset'");
+    }
+
+    if (min > max) {
+      return CommandFailure(EINVAL, "'min' should not be greater than 'max'");
+    }
+
+    vars_[curr + i].offset = offset;
+    vars_[curr + i].mask = mask;
+    vars_[curr + i].min = min;
+
+    // avoid modulo 0
+    vars_[curr + i].range = (max - min + 1) ?: 0xffffffff;
+    vars_[curr + i].cur = 0;
+    vars_[curr + i].bit_shift = (4 - size) * 8;
+  }
+
+  num_vars_ = curr + arg.fields_size();
+  return CommandSuccess();
+}
+
+CommandResponse SequentialUpdate::CommandClear(const bess::pb::EmptyArg &) {
+  num_vars_ = 0;
+  return CommandSuccess();
+}
+
+void SequentialUpdate::ProcessBatch(bess::PacketBatch *batch) {
+  int cnt = batch->cnt();
+
+  for (size_t i = 0; i < num_vars_; i++) {
+    const auto var = &vars_[i];
+
+    be32_t mask = var->mask;
+    uint32_t min = var->min;
+    uint32_t range = var->range;
+    uint32_t cur = var->cur;
+    size_t offset = var->offset;
+    size_t bit_shift = var->bit_shift;
+
+    for (int j = 0; j < cnt; j++) {
+      be32_t *p = batch->pkts()[j]->head_data<be32_t *>(offset);
+      uint32_t value = min + cur;
+      cur = cur + 1;
+      if (cur >= range) {
+        cur = 0;
+      }
+
+      *p = (*p & mask) | (be32_t(value) << bit_shift);
+    }
+
+    var->cur = cur;
+  }
+
+  RunNextModule(batch);
+}
+
+ADD_MODULE(SequentialUpdate, "supdate",
+           "updates packet data sequentially in a range")
diff --git a/sample_plugin/modules/sequential_update.h b/sample_plugin/modules/sequential_update.h
new file mode 100644
index 000000000..359f1148c
--- /dev/null
+++ b/sample_plugin/modules/sequential_update.h
@@ -0,0 +1,68 @@
+// Copyright (c) 2014-2017, The Regents of the University of California.
+// Copyright (c) 2016-2017, Nefeli Networks, Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice, this
+// list of conditions and the following disclaimer.
+//
+// * Redistributions in binary form must reproduce the above copyright notice,
+// this list of conditions and the following disclaimer in the documentation
+// and/or other materials provided with the distribution.
+//
+// * Neither the names of the copyright holders nor the names of their
+// contributors may be used to endorse or promote products derived from this
+// software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef BESS_MODULES_SEQUENTIALUPDATE_H_
+#define BESS_MODULES_SEQUENTIALUPDATE_H_
+
+#include "module.h"
+#include "utils/endian.h"
+
+#include "protobuf/supdate_msg.pb.h"
+
+static const size_t kMaxVariable = 16;
+
+class SequentialUpdate final : public Module {
+public:
+  static const Commands cmds;
+
+  SequentialUpdate() : Module(), num_vars_(), vars_() {}
+
+  CommandResponse Init(const sample::supdate::pb::SequentialUpdateArg &arg);
+
+  void ProcessBatch(bess::PacketBatch *batch) override;
+
+  CommandResponse
+  CommandAdd(const sample::supdate::pb::SequentialUpdateArg &arg);
+  CommandResponse CommandClear(const bess::pb::EmptyArg &arg);
+
+private:
+  size_t num_vars_;
+
+  struct {
+    bess::utils::be32_t mask; // bits with 1 won't be updated
+    uint32_t min;
+    uint32_t range; // max - min + 1
+    uint32_t cur;
+    size_t offset;
+    size_t bit_shift;
+  } vars_[kMaxVariable];
+};
+
+#endif // BESS_MODULES_SEQUENTIALUPDATE_H_
diff --git a/sample_plugin/protobuf/supdate_msg.proto b/sample_plugin/protobuf/supdate_msg.proto
new file mode 100644
index 000000000..bca8070e3
--- /dev/null
+++ b/sample_plugin/protobuf/supdate_msg.proto
@@ -0,0 +1,60 @@
+// Copyright (c) 2017, The Regents of the University of California.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice, this
+// list of conditions and the following disclaimer.
+//
+// * Redistributions in binary form must reproduce the above copyright notice,
+// this list of conditions and the following disclaimer in the documentation
+// and/or other materials provided with the distribution.
+//
+// * Neither the names of the copyright holders nor the names of their
+// contributors may be used to endorse or promote products derived from this
+// software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package sample.supdate.pb;
+
+/**
+ * The function `clear()` for SequentialUpdate takes no parameters and clears all
+ * state in the module.
+ */
+message SequentialUpdateCommandClearArg {
+}
+
+/**
+ * The SequentialUpdate module rewrites a specified field (`offset` and `size`) in a packet
+ * with a sequentially increased value from a specified min to max values.
+ *
+ * __Input Gates__: 1
+ * __Output Gates__: 1
+ */
+message SequentialUpdateArg {
+  /**
+   * SequentialUpdate's Field specifies where to rewrite, and what values to rewrite
+   * in each packet processed.
+   */
+  message Field {
+    int64 offset = 1; /// Offset in bytes for where to rewrite.
+    uint64 size = 2; /// The number of bytes to write.
+    uint64 min = 3; /// The minimum value to insert into the packet.
+    uint64 max = 4; /// The maximum value to insert into the packet.
+  }
+  repeated Field fields = 1; /// A list of SequentialUpdate Fields.
+}