intel / dps-for-iot

DISCONTINUATION OF PROJECT

This project will no longer be maintained by Intel.

Intel has ceased development and contributions including, but not limited to, maintenance, bug fixes, new releases, or updates, to this project.

Intel no longer accepts patches to this project.

If you have an ongoing need to use this project, are interested in independently developing it, or would like to maintain patches for the open source software community, please create your own fork of this project.

Contact: [email protected]

Distributed Publish & Subscribe for IoT

Distributed Publish & Subscribe for IoT (DPS) is a new protocol that implements the publish/subscribe (pub/sub) communication pattern.

Devices or applications running the protocol form a dynamic multiply-connected mesh where each node functions as a message router. The protocol is light-weight and amenable to implementation on very small devices such as sensors that primarily publish data. The architecture is well suited for applications that leverage edge computing in combination with cloud-based analytics.

Building and Running

Documentation

dps-for-iot's Issues

Node discovery does not work with publications supporting wildcards

The test case is something along the lines of (to exercise wildcards and multiple subscriptions):

1. ./build/test/bin/discover -s A -p B -s C
2. ./build/test/bin/discover -p A -s B -s D
   Node 1 should receive pub A and node 2 should receive pub B, but they do not.

The root cause is the removal of the needs from discovery in bdd8141.

Nonce may be reused on sequence number wraparound

The nonce used in content encryption is derived from the publication UUID and the sequence number, thus it may be reused when the sequence number (a 32-bit number) wraps.

Add support for retained messages over multicast

A late joining subscriber will receive retained messages only when it links to a node. This feature is to support receiving retained messages when the subscriber does not link to a node.

Add a minimal size release variant

Currently, the build variants supported are debug and release, the latter implies -O3.

It would be useful to add a min-size-release option (analogue to CMake's MinSizeRel) to better fit resource-constrained environments.

At the very least it should specify -Os. Additional relevant options might be -s, -fdata-sections -ffunction-sections, -flto, -Wl,--gc-sections, -Wl,--strip-all.

RTOS Support

Is there any plan in progress to support DPS on an RTOS?

How to guarantee Subscription messages are delivered

When running DPS over UDP there is no guarantee a Subscription message will be delivered to all nodes from the network. If a Subscription message is lost, the network 'interests' might not converge so publications may be dropped even if there is a node interested in it.

The following example shows the case:

A---B---C---D

'A' sends a Subscription on topic "/foo/bar" to 'B'. 'B' sends the Subscription to 'C' but for some reason it is lost. Later on, D publishes a message on topic "/foo/bar". Since 'C' has never received the Subscription from 'B', it believes the network has no interest in that Publication and drops it.

Maybe this issue could be fixed with an Acknowledgement message between hops.

RPC

On the ROS forum you mentioned "Built-in support for RPC". I don't see anything obvious specifically supporting this in the code, please could you explain this point further?

Notify user in case something goes wrong with Publication transmission

DPS_Publish() API returns DPS_OK in case the publication was successfully scheduled to be transmitted. However, it is possible something goes wrong during the transmission itself (DPS_OnPubSendComplete() is called with 'status' != 0). In that case, we should probably notify the user application so it is able to handle it.

Minimum compiler and (runtime) library versions, static linking?

Not too familiar with SCons, so perhaps this is glaringly obvious for someone who is, but I could not find any statements regarding minimum versions of compilers, C standards, versions of libraries and/or runtime platforms. Could you list that somewhere?

The building and running page only states gcc or clang as a compiler requirement. Which C version are you targeting?

Additionally: would this be suitable to build fully statically linked applications? Yocto is mentioned as a deployment tool, but one of my candidate platforms is not compatible with that. I do have a cross-compiler for it that can generate binaries and the platform has some support for dynamic linking, but going fully static would simplify things significantly.

Does not build on ubuntu 20.04

I tried building this on a standard x86_64 ubuntu 20.04 machine, and it seems to choke when linking to libuv. I installed libuv1 and libuv1-dev through apt, then ran

scons -Q variant=debug transport=tcp bindings=none

It failed at the linking step, so I figured it was because libuv gets installed in /usr/lib/x86_64-linux-gnu. I'm not very familiar with scons, so I just did a quick & dirty change to SConstruct:

@@ -267,7 +267,7 @@ elif env['PLATFORM'] == 'posix':
     # Data relocation and protection (RELRO):
     env.Append(LINKFLAGS = ['-z', 'relro', '-z', 'now'])
 
-env.Append(LIBPATH=['./ext'])
+env.Append(LIBPATH=['./ext','/usr/lib/x86_64-linux-gnu'])

It still failed, and it appears to be because of the linking order, so I also changed:

@@ -125,7 +125,7 @@ elif env['PLATFORM'] == 'posix':
             env['PY_CPPPATH'] = [inc[2:] for inc in py_cpppath]
             env['PY_LIBPATH'] = []
 
-    env['DPS_LIBS'] = ['pthread', 'dl']
+    env['DPS_LIBS'] = ['uv', 'pthread', 'dl']

Definitely not the right way to fix it, but it builds now.

Not compiling on arm64

I tried to compile it on an arm64 arch (raspberry pi4) but it's failing.
/usr/bin/ld: ext/intel-ipsec-mb/lib/sse/sha512_one_block_sse.os: Relocations in generic ELF (EM: 62) /usr/bin/ld: ext/intel-ipsec-mb/lib/sse/sha512_one_block_sse.os: Relocations in generic ELF (EM: 62) /usr/bin/ld: ext/intel-ipsec-mb/lib/sse/sha512_one_block_sse.os: Relocations in generic ELF (EM: 62) /usr/bin/ld: ext/intel-ipsec-mb/lib/sse/sha512_one_block_sse.os: Relocations in generic ELF (EM: 62) /usr/bin/ld: ext/intel-ipsec-mb/lib/sse/sha512_one_block_sse.os: error adding symbols: file in wrong format collect2: error: ld returned 1 exit status scons: *** [build/obj/lib/libdps_ns3.so] Error 1 scons: building terminated because of errors.
I've tried with different compilers and even tried cross-compile with arm-linux-gnueabi-gcc and aarch64-linux-gnu-gcc but also having the same issue.

Running with python, help needed

I could install this project with python bindings, and run the example pub/sub scripts, but pub and sub are not exchanging messages.

The output of pub:

/dps-for-iot/py_scripts# PYTHONPATH=../build/dist/py python simple_pub.py 
Publisher is listening on [::]:57575
Pub UUID f4d1c799-8bcb-2574-6155-f11c9e9f8074(1)
Pub UUID f4d1c799-8bcb-2574-6155-f11c9e9f8074(2)
Traceback (most recent call last):
  File "simple_pub.py", line 185, in <module>
    dps.destroy_publication(pub)
TypeError: destroy_publication expected 2 arguments, got 1

The output of sub:

/dps-for-iot/py_scripts# PYTHONPATH=../build/dist/py python simple_sub.py 
Subscriber is listening on [::]:48070

I did start the subscriber before the publisher and I think i'm missing some network options.
What do I need to do to get this work?

And another question, I would like to use it with python3 instead of python2, but in this case i get following error:

Traceback (most recent call last):
  File "simple_sub.py", line 2, in <module>
    import dps
  File "/dps-for-iot/build/dist/py/dps.py", line 24, in <module>
    _dps = swig_import_helper()
  File "/dps-for-iot/build/dist/py/dps.py", line 23, in swig_import_helper
    return importlib.import_module('_dps')
  File "/usr/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
ImportError: /dps-for-iot/build/dist/py/_dps.so: undefined symbol: PyInstance_Type

Is python3 supported or do you plan to support it?

dps-micro tries to free a static variable when destroying a node

The dps-micro DPS_CreateKeyStore() method is called by DPS_CreateNode(). DPS_CreateKeyStore() creates a static variable for the keystore and returns a pointer to it. Then, when we destroy the node, we call DPS_DestroyKeyStore() and try to free various parts of the static keystore. This can (will?) segfault on some (all?) systems.

We could allocate the keystore on the heap instead, or if it needs to be static, we can reinitialize the keystore to zero when destroying it.

CBOR_Peek size argument inconsistent with other CBOR functions

CBOR_Peek takes a uint64_t as the size argument, but CBOR_DecodeArray (and others) take a size_t.

This is an issue on 32-bit platforms (such as RaspberryPi) where size_t and uint64_t are different sizes.

python-config is only needed for python bindings

A warning is emitted when python-config is not found. This should only be emitted when the python bindings are being built.