[bug] Supposed memory leak

[andrea3x]

Describe the bug
I implemented a simple chat application with this library and when testing, the board often froze after sending or receiving a few messages.

Specifically, sending or receiving 15-20 messages of variable length (25-40 characters) is enough to cause my CubeCell devices to freeze.

The last log before the board often blocked was:
[I][PacketRouter.cpp] Routing packet with id: xxx crc: yyy
However, it sometimes occurred after other logs.

I suppose it's a memory leak because I added various logs during packet preparation and it often failed near instructions that allocate memory.
I used this function (with 4096 as the starting point) to try to estimate how heap memory was occupied over time, and I noticed a drastic reduction message after message.

I also tried sending a 117-character message (after a reset to free memory). It froze instantly.

Do you have any idea of where the problem is?
Thanks

To reproduce

1. Add in loop() the following

if (Serial.available() > 0) {
        std::string input = Serial.readString().c_str();
        sendMessage({0xff, 0xff, 0xff, 0xff}, input);
}

sendMessage() implementation

typedef std::array<byte, RM_ID_LENGTH> RadioMeshAddress;
void sendMessage(RadioMeshAddress addr, const std::string& str) {
    loginfo_ln("Sending message: %s", str.c_str());
    std::vector<byte> payload(str.begin(), str.end());

    int rc = device->sendData(0x10, payload, addr);
    if (rc == RM_E_NONE) {
        loginfo_ln("Sent message: %s", str.c_str());
    } else {
        logerr_ln("Failed to send message.");
    }
}

2. Add at the end of onPacketReceived callback the following:

loginfo_ln("Received application message, topic: 0x%02X", packet->topic);
const std::vector<byte>& data = packet->packetData;
const std::string msg(data.begin(), data.end());
loginfo_ln("%s", msg.c_str());

3. Chat between CubeCell devices, inserting text with various lengths (in my own tests 15-20 messages with 25-40 characters were enough to make the board freeze).

Expected behavior

The board does not freeze.

Additional context

• Boards name: CubeCell AB02, AB02A, AB01v2
• Wireless module type: LoRa SX1262
• Library version: 0.1.0

Edit: I used RM_LOG_INFO as log level, I might try a few tests with RM_LOG_DEBUG

[amirna2]

@andrea3x thank you for reporting this issue. I am looking into it.

[amirna2]

@andrea3x My preliminary investigation does not reveal any obvious memory leaks.
However memory allocation and usage is not optimized for device like the CubeCell with only 16kb memory.
Specifically the library is making a lot of small dynamic memory allocations which causes heap to be fragmented over time.

The biggest offender appear to be AesCmac::computeCMAC which allocates a ton of small 16 bytes vectors on the heap on a long message it could easily 100s of allocation. On 16 KB that fragments the arena until a large contiguous request can't be satisfied and a failed allocation on this core means freeze.

The logger also is non optimal as it dumps large messages: the Data: %s line in calculatePacketCrc and packet.log() are the biggest logger allocations.

I'll work on a fix for these two issues.

[andrea3x]

@amirna2 thank you for your investigation!

I hope you can fix it!
Thank you

PS: I also leave you the link of my pull request and of a discussion I created a while back, in case you didn't see them