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net: lwm2m: Allow to acknowledge request early from the callback

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LwM2M engine by default sends piggybacked responses for requests after
all callbacks are executed. This approach however isn't good enough if
the application callback executes some lenghty operations (for instance
during FW update). Delaying the ACK may result in unnecessary
retransmissions.

This commits adds an API function which allows to send an early empty
ACK from the application callback. This prevents further retransmissions
from the server side. After all callbacks are executed, the LwM2M engine
will send the response as a separate CON message.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>
This commit is contained in:
Robert Lubos 2020-12-01 13:56:34 +01:00 • committed by Anas Nashif
commit 4331c05f17
2 changed files with 91 additions and 0 deletions
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71
subsys/net/lib/lwm2m/lwm2m_engine.c
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@ -1076,6 +1076,27 @@ cleanup:
return ret;
}
void lwm2m_acknowledge(struct lwm2m_ctx *client_ctx)
{
struct lwm2m_message *request;
if (client_ctx == NULL || client_ctx->processed_req == NULL) {
return;
}
request = (struct lwm2m_message *)client_ctx->processed_req;
if (request->acknowledged) {
return;
}
if (lwm2m_send_empty_ack(client_ctx, request->mid) < 0) {
return;
}
request->acknowledged = true;
}
uint16_t lwm2m_get_rd_data(uint8_t *client_data, uint16_t size)
{
struct lwm2m_engine_obj *obj;
@ -3766,6 +3787,42 @@ error:
return 0;
}
static int lwm2m_response_promote_to_con(struct lwm2m_message *msg)
{
int ret;
msg->type = COAP_TYPE_CON;
msg->mid = coap_next_id();
/* Since the response CoAP packet is already generated at this point,
* tweak the specific fields manually:
* - CoAP message type (byte 0, bits 2 and 3)
* - CoAP message id (bytes 2 and 3)
*/
msg->cpkt.data[0] &= ~(0x3 << 4);
msg->cpkt.data[0] |= (msg->type & 0x3) << 4;
msg->cpkt.data[2] = msg->mid >> 8;
msg->cpkt.data[3] = (uint8_t) msg->mid;
/* Add the packet to the pending list. */
msg->pending = coap_pending_next_unused(
msg->ctx->pendings,
CONFIG_LWM2M_ENGINE_MAX_PENDING);
if (!msg->pending) {
LOG_ERR("Unable to find a free pending to track "
"retransmissions.");
return -ENOMEM;
}
ret = coap_pending_init(msg->pending, &msg->cpkt, &msg->ctx->remote_addr);
if (ret < 0) {
LOG_ERR("Unable to initialize a pending "
"retransmission (err:%d).", ret);
}
return ret;
}
static void lwm2m_udp_receive(struct lwm2m_ctx *client_ctx,
uint8_t *buf, uint16_t buf_len,
struct sockaddr *from_addr,
@ -3867,12 +3924,26 @@ static void lwm2m_udp_receive(struct lwm2m_ctx *client_ctx,
/* skip token generation by default */
msg->tkl = 0;
client_ctx->processed_req = msg;
/* process the response to this request */
r = udp_request_handler(&response, msg);
if (r < 0) {
return;
}
if (msg->acknowledged) {
r = lwm2m_response_promote_to_con(msg);
if (r < 0) {
LOG_ERR("Failed to promote reponse to CON: %d",
r);
lwm2m_reset_message(msg, true);
return;
}
}
client_ctx->processed_req = NULL;
r = lwm2m_send_message(msg);
if (r < 0) {
LOG_ERR("Err sending response: %d", r);