net: lib: coap_client: Don't decrease retry counter on send() failure

If send() fails, we have not technically send the CoAP retry yet, so
restore the same pending structure, so our timeouts and retry counters
stay the same.

This will trigger a retry next time the poll() return POLLOUT, so we
know that we can send.

Signed-off-by: Seppo Takalo <[email protected]>

Author: SeppoTakalo

subsys/net/lib/coap/coap_client.c

@@ -471,10 +471,13 @@ static int resend_request(struct coap_client *client,
 {
 	int ret = 0;
 
+	/* Copy the pending structure if we need to restore it */
+	struct coap_pending tmp = internal_req->pending;
+
 	if (internal_req->request_ongoing &&
 	    internal_req->pending.timeout != 0 &&
 	    coap_pending_cycle(&internal_req->pending)) {
-		LOG_ERR("Timeout in poll, retrying send");
+		LOG_ERR("Timeout, retrying send");
 
 		/* Reset send block context as it was updated in previous init from packet */
 		if (internal_req->send_blk_ctx.total_size > 0) {
@@ -483,22 +486,27 @@ static int resend_request(struct coap_client *client,
 		ret = coap_client_init_request(client, &internal_req->coap_request,
 					       internal_req, true);
 		if (ret < 0) {
-			LOG_ERR("Error re-creating CoAP request");
+			LOG_ERR("Error re-creating CoAP request %d", ret);
+			return ret;
+		}
+
+		ret = send_request(client->fd, internal_req->request.data,
+					internal_req->request.offset, 0, &client->address,
+					client->socklen);
+		if (ret > 0) {
+			ret = 0;
+		} else if (ret == -1 && errno == EAGAIN) {
+			/* Restore the pending structure, retry later */
+			internal_req->pending = tmp;
+			/* Not a fatal socket error, will trigger a retry */
+			ret = 0;
 		} else {
-			ret = send_request(client->fd, internal_req->request.data,
-					   internal_req->request.offset, 0, &client->address,
-					   client->socklen);
-			if (ret > 0) {
-				ret = 0;
-			} else {
-				LOG_ERR("Failed to resend request, %d", ret);
-			}
+			ret = -errno;
+			LOG_ERR("Failed to resend request, %d", ret);
 		}
 	} else {
-		LOG_ERR("Timeout in poll, no more retries left");
+		LOG_ERR("Timeout, no more retries left");
 		ret = -ETIMEDOUT;
-		report_callback_error(internal_req, ret);
-		internal_req->request_ongoing = false;
 	}
 
 	return ret;