[er5] Could not process mesh packet...

[Inti3456]

I am currently working on a project based on the light_switch mesh example and am running into an issue where I'm receiving several of the following error throughout operation:

[er5] Could not process mesh packet...

er5 refers to NRF_ERROR_NOT_FOUND

It would appear that it comes about from the following function in net_packet.c

uint32_t net_packet_decrypt(network_packet_metadata_t * p_net_metadata,
                            uint32_t net_packet_len,
                            const packet_mesh_net_packet_t * p_net_encrypted_packet,
                            packet_mesh_net_packet_t * p_net_decrypted_packet,
                            net_packet_kind_t packet_kind)
{
    NRF_MESH_ASSERT(p_net_metadata != NULL && p_net_encrypted_packet != NULL &&
                    p_net_decrypted_packet != NULL &&
                    p_net_decrypted_packet != p_net_encrypted_packet);

    if (net_packet_len < PACKET_MESH_NET_PDU_OFFSET || net_packet_len > PACKET_MESH_NET_MAX_SIZE)
    {
        return NRF_ERROR_INVALID_LENGTH;
    }

    p_net_metadata->internal.iv_index = net_state_rx_iv_index_get(packet_mesh_net_ivi_get(p_net_encrypted_packet));
    p_net_metadata->p_security_material = NULL;
    uint8_t nid = packet_mesh_net_nid_get(p_net_encrypted_packet);

    const nrf_mesh_network_secmat_t * p_secmat[2] = { NULL, NULL };
    do {
        nrf_mesh_net_secmat_next_get(nid, &p_secmat[0], &p_secmat[1]);

        for (uint32_t i = 0; i < ARRAY_SIZE(p_secmat) && p_secmat[i] != NULL; i++)
        {
            if (try_decrypt(p_net_metadata,
                            net_packet_len,
                            p_net_encrypted_packet,
                            p_net_decrypted_packet,
                            p_secmat[i],
                            packet_kind))
            {
                return NRF_SUCCESS;
            }
        }
    } while (p_secmat[0] != NULL);

    return NRF_ERROR_NOT_FOUND;
}

Any idea what would be causing this to happen?

[Hung Bui]

Hi Inti, 

How often do you see the "[er5] Could not process mesh packet...  " ? 
We have seen that occurred occasionally as well. It's can be either from from corrupted packets or packets from other network. So any packet that passed CRC and has the right Mesh flag in the advertising type will get to packet_in(). 
When net_packet_decrypt() couldn't decode the message, it will throw NRF_ERROR_NOT_FOUND

[Inti3456]

I see it with nearly every transaction of mesh messages. Usually for every Unencrypted data I get, I get 2 or so of those error packets.

[Hung Bui]

Do you have a lot of mesh traffic around ? 
Could you give some more information about the setup ? How many device did you use ? Did you use the phone to test ? 
Could you capture a full log when you see the issue ?