TREL - Platform#

otPlatTrelPeerInfo#

typedef struct otPlatTrelPeerInfo otPlatTrelPeerInfo

This structure represents a TREL peer info discovered using DNS-SD browse on the service name "_trel._udp".

otPlatTrelEnable#

void otPlatTrelEnable (otInstance * aInstance, uint16_t * aUdpPort)

This function initializes and enables TREL platform layer.

Upon this call, the platform layer MUST perform the following:

1) TREL platform layer MUST open a UDP socket to listen for and receive TREL messages from peers. The socket is bound to an ephemeral port number chosen by the platform layer. The port number MUST be returned in aUdpPort. The socket is also bound to network interface(s) on which TREL is to be supported. The socket and the chosen port should stay valid while TREL is enabled.

2) Platform layer MUST initiate an ongoing DNS-SD browse on the service name "_trel._udp" within the local browsing domain to discover other devices supporting TREL. The ongoing browse will produce two different types of events: "add" events and "remove" events. When the browse is started, it should produce an "add" event for every TREL peer currently present on the network. Whenever a TREL peer goes offline, a "remove" event should be produced. "remove" events are not guaranteed, however. When a TREL service instance is discovered, a new ongoing DNS-SD query for an AAAA record should be started on the hostname indicated in the SRV record of the discovered instance. If multiple host IPv6 addressees are discovered for a peer, one with highest scope among all addresses MUST be reported (if there are multiple address at same scope, one must be selected randomly).

TREL platform MUST signal back the discovered peer info using otPlatTrelHandleDiscoveredPeerInfo() callback. This callback MUST be invoked when a new peer is discovered, when there is a change in an existing entry (e.g., new TXT record or new port number or new IPv6 address), or when the peer is removed.

otPlatTrelDisable#

void otPlatTrelDisable (otInstance * aInstance)

This function disables TREL platform layer.

After this call, the platform layer MUST stop DNS-SD browse on the service name "_trel._udp", stop advertising the TREL DNS-SD service (from otPlatTrelRegisterService()) and MUST close the UDP socket used to receive TREL messages.

@pram[in] aInstance The OpenThread instance.

otPlatTrelHandleDiscoveredPeerInfo#

void otPlatTrelHandleDiscoveredPeerInfo (otInstance * aInstance, const otPlatTrelPeerInfo * aInfo)

This is a callback function from platform layer to report a discovered TREL peer info.

Note

• The aInfo structure and its content (e.g., the mTxtData buffer) does not need to persist after returning from this call. OpenThread code will make a copy of all the info it needs.

otPlatTrelRegisterService#

void otPlatTrelRegisterService (otInstance * aInstance, uint16_t aPort, const uint8_t * aTxtData, uint8_t aTxtLength)

This function registers a new service to be advertised using DNS-SD [RFC6763].

The service name is "_trel._udp". The platform should use its own hostname, which when combined with the service name and the local DNS-SD domain name will produce the full service instance name, for example "example-host._trel._udp.local.".

The domain under which the service instance name appears will be 'local' for mDNS, and will be whatever domain is used for service registration in the case of a non-mDNS local DNS-SD service.

A subsequent call to this function updates the previous service. It is used to update the TXT record data and/or the port number.

The aTxtData buffer is not persisted after the return from this function. The platform layer MUST NOT keep the pointer and instead copy the content if needed.

otPlatTrelSend#

void otPlatTrelSend (otInstance * aInstance, const uint8_t * aUdpPayload, uint16_t aUdpPayloadLen, const otSockAddr * aDestSockAddr)

This function requests a TREL UDP packet to be sent to a given destination.

otPlatTrelHandleReceived#

void otPlatTrelHandleReceived (otInstance * aInstance, uint8_t * aBuffer, uint16_t aLength)

This function is a callback from platform to notify of a received TREL UDP packet.

Note

• The buffer content (up to its specified length) may get changed during processing by OpenThread core (e.g., decrypted in place), so the platform implementation should expect that after returning from this function the aBuffer content may have been altered.