Refactor pillar/zedcloud into pillar/cloudconn with improved structure and testing

This commit significantly refactors the pillar/zedcloud package to improve
code organization, readability, and test coverage. The changes include:

1. Package renaming:
   - Renamed zedcloud to cloudconn to avoid using the name of the proprietary
     controller implementation
   - New name better reflects the package purpose, which is to establish
     connection to the controller/LOC/LPS and perform some HTTP(S) request
     or just check if connectivity is working

2. Code structure improvements:
   - Replaced ZedCloudContext with cloudconn.Client object for cleaner
     OOP approach
   - Portions of the very long and deeply nested SendOnIntf function were
     split into separate internal cloudconn.Client methods for better
     readability and maintainability
   - Renamed DeferredContext to DeferredQueue for more accurate naming
     (using Context for every struct with some methods is not particularly
     Go idiomatic)
   - Moved zedagent-specific deferred queue instances from the former
     ZedCloudContext into zedagentContext (zedagent refactoring is also
     much needed)

3. Function argument improvements:
   - Replaced long lists of boolean arguments in SendOnIntf and SetDeferred
     with RequestOptions and DeferredItemOpts structs, respectively,
     for clearer and more maintainable method calls
   - Added comments documenting all the options

4. Code reorganization:
   - Consolidated network utilities from pillar/devicenetwork into:
     * pillar/types for constants
     * cloudconn for proxy/DNS functionality
       (where some of this functionality was already present)
   - package pillar/devicenetwork was removed
     (it contained only some random leftovers from NIM/zedrouter refactoring)

5. Testing:
   - Added unit tests for cloudconn.Client's Send/Verify methods
   - Added tests for DeferredQueue functionality

The changes maintain all existing functionality while making the code more
maintainable, self-documenting, and easier to extend in the future.

Signed-off-by: Milan Lenco <milan@zededa.com>

Author: milan-zededa

docs/COMMS.md

@@ -1,7 +1,8 @@
 # Communications
 
 This document describes the components in EVE that are responsible for
-communications between an EVE instance and a Controller. Read about the API for Device to Controller Communications [here](https://github.com/lf-edge/eve-api/tree/main/APIv2.md)
+communications between an EVE instance and a Controller.
+Read about the API for Device to Controller Communications [here](https://github.com/lf-edge/eve-api/tree/main/APIv2.md)
 
 All of these are components of [pkg/pillar](../pkg/pillar/), which is the set
 of process, commands and services responsible for managing an EVE device.
@@ -22,8 +23,8 @@ with the Controller does so directly; there is no local proxy or buffering
 engine process that stands between these processes and the Controller.
 
 However, common logic for communications is extracted out to the package
-[pkg/pillar/zedcloud](../pkg/pillar/zedcloud/). Each service that needs to
-communicate with the Controller imports the `zedcloud` package and uses its
+[pkg/pillar/cloudconn](../pkg/pillar/cloudconn/). Each service that needs to
+communicate with the Controller imports the `cloudconn` package and uses its
 functions to communicate with the Controller.
 
 The overall architecture is as follows.
@@ -37,7 +38,7 @@ The overall architecture is as follows.
      |   |   |   |         |
      v   v   v   v         v
     +++ +++ +++ +++      +-+--+
-    |z| |z| |z| |z|      | zc |  *zc = zedcloud package
+    |c| |c| |c| |c|      | cc |  *cc = cloudconn package
     |c| |c| |c| |c|      |    |
     | | | | | | | |      |    |
     | | | | | | | |      |    |
@@ -59,49 +60,50 @@ The overall architecture is as follows.
      |        pubsub        |
      +----------------------+
 
-### zedcloud - communications
+### cloudconn - communications
 
 In EVE, the shared functionality for communications with the Controller is
-encapsulated in the [zedcloud](../pkg/pillar/zedcloud) package. All services
-communicate with the Controller using functions provided via the `zedcloud`
+encapsulated in the [cloudconn](../pkg/pillar/cloudconn) package. All services
+communicate with the Controller using functions provided via the `cloudconn`
 package.
 
-`zedcloud` is responsible for:
+`cloudconn` is responsible for:
 
 * Creating SSL channels
 * mutual TLS (mTLS) and client authentication
 * Handling http logic, including status codes
 * Retries in case of loss of communication
 * Using multiple management ports to communicate with the controller
 
-`zedcloud` does _not_ currently handle protobuf analysis. It is blissfully
+`cloudconn` does _not_ handle protobuf analysis. It is blissfully
 unaware of the contents of most messages in both directions. It simply makes
 the request on behalf of, and passes the response back to, the requesting
 functions.
 
 The logic in the services themselves do the following:
 
+* Create an instance of `cloudconn.Client` using the `cloudconn.NewClient` method
 * Package up any messages to be sent in protobuf
-* Pass the message to functions in `zedcloud`
-* Receive the response from `zedcloud`
+* Pass the message to `Send*` methods of `cloudconn.Client`
+* Receive the response from controller
 * Unpack the received protobufs
 
 ### services
 
 The following are a few of the key services that communicate with the
-Controller via the functions provided in the `zedcloud` package.
+Controller via `cloudconn.Client`.
 
 #### zedagent
 
 [zedconfig](../pkg/pillar/cmd/zedagent) is the service responsible for retrieving
 configuration from the Controller and updating locally running services on EVE.
 Like all other services communicating with the Controller, it does so through
-functions provided by the `zedcloud` package.
+the methods provided by `cloudconn.Client`.
 
 `zedagent` is responsible for the following:
 
 * Maintaining a regular cycle for retrieving configuration or updates from Controller.
-* Requesting the configuration from the Controller via functions in `zedcloud`.
+* Requesting the configuration from the Controller via methods provided by `cloudconn.Client`.
 * Receiving the latest correct configuration in response to its request.
 * Saving the latest correct configuration locally.
 * Loading the initial (aka bootstrap) device configuration if present (see [CONFIG.md](./CONFIG.md))
@@ -111,7 +113,7 @@ functions provided by the `zedcloud` package.
 
 [Loguploader](../pkg/pillar/cmd/loguploader) is the service responsible for
 uploading device and application gzip logs to controller. It does
-so through the functions provided by the `zedcloud` package.
+so through the methods provided by `cloudconn.Client`.
 
 #### client
 
@@ -124,14 +126,14 @@ configuration, as part of onboarding a new device to the Controller.
 [Network interface manager](../pkg/pillar/cmd/nim) is responsible for managing
 local network interfaces on the device, as well as checking connectivity to the
 Controller and retrieving the config for testing communications purposes. All
-communications with the Controller are performed via the functions provided by
-the `zedcloud` package.
+communications with the Controller are performed via the methods provided
+by `cloudconn.Client`.
 
 #### diag
 
 [Diagnostics](../pkg/pillar/cmd/diag) is responsible for managing diagnostic
 services on the device, and reporting to console for debugging if there are
 issues. It does not send information to the Controller. However, among its
 diagnostic tests, it does test the ability to reach both the ping and config endpoints
-of the Controller. To connect and test these endpoints, it uses the functions
-provided by the `zedcloud` package.
+of the Controller. To connect and test these endpoints, it uses the methods provided
+by `cloudconn.Client`.

pkg/pillar/zedcloud/zedcloudmetric.go pkg/pillar/cloudconn/agentmetrics.gopkg/pillar/zedcloud/zedcloudmetric.go renamed to pkg/pillar/cloudconn/agentmetrics.go

@@ -1,11 +1,11 @@
 // Copyright (c) 2018 Zededa, Inc.
 // SPDX-License-Identifier: Apache-2.0
 
-// AgentMetrics is used to maintain metrics about the connectivity to zedcloud.
-// Just success and failures.
+// AgentMetrics is used to maintain metrics about the connectivity to the controller.
+// Just successes and failures.
 // Reported as device metrics.
 
-package zedcloud
+package cloudconn
 
 import (
 	"strings"
@@ -17,7 +17,7 @@ import (
 	"github.com/lf-edge/eve/pkg/pillar/types"
 )
 
-// AgentMetrics stores zedcloud related metrics for one agent (microservice).
+// AgentMetrics stores controller related metrics for one agent (microservice).
 // Able to properly handle concurrent access.
 type AgentMetrics struct {
 	sync.Mutex
@@ -40,18 +40,20 @@ func (am *AgentMetrics) acquire(log *base.LogObject) (release func()) {
 }
 
 // getInterfaceMetrics is an internal function returning metrics corresponding
-// to a given interface. It assumes that the caller has acquired metrics using AgentMetrics.acquire().
-func (am *AgentMetrics) getInterfaceMetrics(ifname string) types.ZedcloudMetric {
+// to a given interface. It assumes that the caller has acquired metrics using
+// AgentMetrics.acquire().
+func (am *AgentMetrics) getInterfaceMetrics(ifname string) types.CloudMetrics {
 	if _, ok := am.metrics[ifname]; !ok {
-		am.metrics[ifname] = types.ZedcloudMetric{
+		am.metrics[ifname] = types.CloudMetrics{
 			URLCounters: make(map[string]types.UrlcloudMetrics),
 		}
 	}
 	return am.metrics[ifname]
 }
 
-// RecordFailure records failed zedcloud API request.
-func (am *AgentMetrics) RecordFailure(log *base.LogObject, ifname, url string, reqLen, respLen int64, authenFail bool) {
+// RecordFailure records failed controller API request.
+func (am *AgentMetrics) RecordFailure(log *base.LogObject, ifname, url string,
+	reqLen, respLen int64, authenFail bool) {
 	release := am.acquire(log)
 	defer release()
 	log.Tracef("RecordFailure(%s, %s, %d, %d, %t)",
@@ -81,24 +83,25 @@ func (am *AgentMetrics) RecordFailure(log *base.LogObject, ifname, url string, r
 	am.metrics[ifname] = m
 }
 
-// RecordSuccess records successful zedcloud API request.
-func (am *AgentMetrics) RecordSuccess(log *base.LogObject, ifname, url string, reqLen, respLen, timeSpent int64, resume bool) {
+// RecordSuccess records successful controller API request.
+func (am *AgentMetrics) RecordSuccess(log *base.LogObject, ifname, url string,
+	reqLen, respLen, timeSpent int64, resume bool) {
 	release := am.acquire(log)
 	defer release()
 	log.Tracef("RecordSuccess(%s, %s, %d, %d, %d, %t)",
 		ifname, url, reqLen, respLen, timeSpent, resume)
 	m := am.getInterfaceMetrics(ifname)
 
-	m.SuccessCount += 1
+	m.SuccessCount++
 	m.LastSuccess = time.Now()
 	var u types.UrlcloudMetrics
 	var ok bool
 	if u, ok = m.URLCounters[url]; !ok {
 		u = types.UrlcloudMetrics{}
 	}
-	u.SentMsgCount += 1
+	u.SentMsgCount++
 	u.SentByteCount += reqLen
-	u.RecvMsgCount += 1
+	u.RecvMsgCount++
 	u.RecvByteCount += respLen
 	u.TotalTimeSpent += timeSpent
 	if resume {
@@ -109,14 +112,16 @@ func (am *AgentMetrics) RecordSuccess(log *base.LogObject, ifname, url string, r
 }
 
 // Publish the recorded metrics through the given publisher.
-func (am *AgentMetrics) Publish(log *base.LogObject, publication pubsub.Publication, key string) error {
+func (am *AgentMetrics) Publish(
+	log *base.LogObject, publication pubsub.Publication, key string) error {
 	release := am.acquire(log)
 	defer release()
 	return publication.Publish(key, am.metrics)
 }
 
 // GetURLsWithSubstr returns URLs containing the given substring.
-func (am *AgentMetrics) GetURLsWithSubstr(log *base.LogObject, substr string) (set []string) {
+func (am *AgentMetrics) GetURLsWithSubstr(
+	log *base.LogObject, substr string) (set []string) {
 	release := am.acquire(log)
 	defer release()
 	for _, cm := range am.metrics {
@@ -136,7 +141,8 @@ func (am *AgentMetrics) RemoveURLMetrics(log *base.LogObject, url string) {
 	for intf, m := range am.metrics {
 		if _, ok := m.URLCounters[url]; ok {
 			delete(m.URLCounters, url)
-			log.Tracef("RemoveURLMetrics: on interface %s deleted metrics for url %s", intf, url)
+			log.Tracef("RemoveURLMetrics: on interface %s deleted metrics for url %s",
+				intf, url)
 			continue
 		}
 	}