Azure IoT Hub Library with OpenThread

[fhfs]

Hello Everyone,

We are working on a new product using the nrf52840 and OpenThread.Our current product uses the Azure IoT Hub and we were wondering if we could use the library used by the nrf91.

According to Didrik in a post on Devzone It should be possible to use this library to connect to the Azure IoT Hub.

I have set up a Thread network and added a route for the NAT64 interface. I am able to use the NAT64 interface as a DNS server to get a IPv6 address synthesized from the well-known-prefix and the IPv4 address.

I've done this using the OpenThread CLI example from the nRF Connect SDK.

I've created a project and I've included the Azure IoT Hub library. It runs but is unable to get a ip address for the provided domain.

I've looked at the Azure IoT Hub code and it uses getaddrinfo to get a ip address from a hostname.

What would be the best way to proceed? I can see the OpenThread CLI example uses a different method to retrieve the ip address from the DNS. Is there a way to configure a DNS server used by getaddrinfo?

[fhfs]

Debugging shows the DNS_EAI_CANCELED is the result of a timeout.

I'm also getting a timeout using the OpenThread specific DNS API's

#include <openthread/dns_client.h>

void ot_dns_response(otError aError, const otDnsAddressResponse *aResponse, void *aContext)
{

	char address_string[OT_IP6_ADDRESS_STRING_SIZE];
	otIp6Address address;
	uint32_t ttl;

	// Fails with error 28
	// [00:00:19.219,787] <inf> net_l2_openthread: State changed! Flags: 0x00000200 Current role: 3
	// [00:00:21.184,112] <err> coap_server: ot_dns_response failed 28

	if (aError == OT_ERROR_NONE)
	{
		uint16_t index = 0;

		LOG_INF("ot_dns_response Success");

		while (otDnsAddressResponseGetAddress(aResponse, index, &address, &ttl) == OT_ERROR_NONE)
		{
			otIp6AddressToString(&address, address_string, sizeof(address_string));
			LOG_INF("ip: %s, TTL:%u ", address_string, ttl);
			index++;
		}
	}
	else
	{
		LOG_ERR("ot_dns_response failed %d", aError);
	}
}

otDnsQueryConfig config;
const otDnsQueryConfig *current_config;
void set_ot_dns_config(void)
{
	otError error;
	current_config = otDnsClientGetDefaultConfig(ot_context->instance);

	memcpy(&config, current_config, sizeof(otDnsQueryConfig));

	config.mNat64Mode = OT_DNS_NAT64_ALLOW;
	config.mRecursionFlag = OT_DNS_FLAG_RECURSION_DESIRED;
	config.mMaxTxAttempts = 2;
	config.mResponseTimeout = 1000;
	config.mServerSockAddr.mPort = 53;

	error = otIp6AddressFromString("FDAA:BB:1::2", &config.mServerSockAddr.mAddress);
	if (error != OT_ERROR_NONE)
		LOG_ERR("otIp6AddressFromString failed %d", error);

	otDnsClientSetDefaultConfig(ot_context->instance, &config);

	current_config = otDnsClientGetDefaultConfig(ot_context->instance);
}

void resolve_ot_dns(void)
{
	otError error;
	error = otDnsClientResolveAddress(ot_context->instance, "ing.nl", &ot_dns_response, ot_context->instance, &config);
	if (error != OT_ERROR_NONE)
	{
		LOG_ERR("ot_dns_response resolve_dns %d", error);
	}
}

Thanks for your suggestions. I'm going to try and increase logging and let you know. Any suggestion to which NET component I should set to debug logging?

[Erik Hougaard]

Hi,

Were you able to make this work? I'd be really interested as I am about to implement a similar solution, so any head-start would be appreciated.

Best regards,

Erik

[fhfs]

According to zephyr\subsys\net\lib\dns\resolve.c:1153 getting mapped ipv4 through getaddrinfo will not work.
I am able to use the OpenThread Libraries to resolve DNS requests through the NAT64 interface.

I will be trying to make small modifications to the nRFConnect Azure library to use Openthread sockets to test if connections will actually work.

[fhfs]

Don't call any zephyr socket functions in any event handlers. Totally forgot I'm now working in a RTOS, shouldnt be doing that anyway.

Zephyr sockets with MBedTLS should be working. Look at echo_client / echo_server as examples.
You can track everything with TCPDump on your Pi.
You can test TLS connection with socat on the Pi.
The guys at OpenThread Github (Discussion board) are very helpful!

Still have not gotten zephyr dns to work, using the OpenThread DNS works.

I am now trying to connect to my Azure IoT Hub using a static ipv6 address (a mapped ipv4 address)
I'll keep you updated.

How are you doing with this problem

[fhfs]

I was using the default interface to do my DNS requests and connections to the network outside the Thread network.

This was fixed when I configured my IPv6 address as "CONFIG_NET_CONFIG_MY_IPV6_ADDR="fd3f:76ab:550:1:2a9d:e83a:3e:84a7""

I was using my mesh local address instead of my localaddress. Mesh Local can only talk to mesh local prefix addresses

With the correct interface I was able to do DNS requests and connections to NAT64 mapped ipv6 addresses