Pull request: 3020 runtime clients sources control

Merge in DNS/adguard-home from 3020-client-sources to master

Closes #3020.

Squashed commit of the following:

commit f8e6b6d63373f99b52f7b8c32f4242c453daf1a4
Merge: 41fb071d 0a1ff65b
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Apr 25 19:19:15 2022 +0300

    Merge branch 'master' into 3020-client-sources

commit 41fb071deb2a87e0a69d09c8f418a016b4dd7e93
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Apr 25 13:38:28 2022 +0300

    home: fix nil, imp docs

commit aaa7765914a8a4645eba357cd088a9470611ffdc
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Apr 25 12:25:47 2022 +0300

    home: imp code

commit 3f71b999564c604583b46313d29f5b70cf51ee14
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Apr 22 19:12:27 2022 +0300

    home: runtime clients sources control

internal/home/config.go

@@ -51,6 +51,13 @@ type osConfig struct {
 	RlimitNoFile uint64 `yaml:"rlimit_nofile"`
 }
 
+type clientsConfig struct {
+	// Sources defines the set of sources to fetch the runtime clients from.
+	Sources *clientSourcesConf `yaml:"runtime_sources"`
+	// Persistent are the configured clients.
+	Persistent []*clientObject `yaml:"persistent"`
+}
+
 // configuration is loaded from YAML
 // field ordering is important -- yaml fields will mirror ordering from here
 type configuration struct {
@@ -88,7 +95,7 @@ type configuration struct {
 	// Clients contains the YAML representations of the persistent clients.
 	// This field is only used for reading and writing persistent client data.
 	// Keep this field sorted to ensure consistent ordering.
-	Clients []*clientObject `yaml:"clients"`
+	Clients *clientsConfig `yaml:"clients"`
 
 	logSettings `yaml:",inline"`
 
@@ -123,9 +130,6 @@ type dnsConfig struct {
 	// UpstreamTimeout is the timeout for querying upstream servers.
 	UpstreamTimeout timeutil.Duration `yaml:"upstream_timeout"`
 
-	// ResolveClients enables and disables resolving clients with RDNS.
-	ResolveClients bool `yaml:"resolve_clients"`
-
 	// PrivateNets is the set of IP networks for which the private reverse DNS
 	// resolver should be used.
 	PrivateNets []string `yaml:"private_networks"`
@@ -198,7 +202,6 @@ var config = &configuration{
 		FilteringEnabled:           true, // whether or not use filter lists
 		FiltersUpdateIntervalHours: 24,
 		UpstreamTimeout:            timeutil.Duration{Duration: dnsforward.DefaultTimeout},
-		ResolveClients:             true,
 		UsePrivateRDNS:             true,
 	},
 	TLS: tlsConfigSettings{
@@ -209,6 +212,15 @@ var config = &configuration{
 	DHCP: &dhcpd.ServerConfig{
 		LocalDomainName: "lan",
 	},
+	Clients: &clientsConfig{
+		Sources: &clientSourcesConf{
+			WHOIS:     true,
+			ARP:       true,
+			RDNS:      true,
+			DHCP:      true,
+			HostsFile: true,
+		},
+	},
 	logSettings: logSettings{
 		LogCompress:   false,
 		LogLocalTime:  false,
@@ -404,9 +416,7 @@ func (c *configuration) write() error {
 		s.WriteDiskConfig(&c)
 		dns := &config.DNS
 		dns.FilteringConfig = c
-		dns.LocalPTRResolvers,
-			dns.ResolveClients,
-			dns.UsePrivateRDNS = s.RDNSSettings()
+		dns.LocalPTRResolvers, config.Clients.Sources.RDNS, dns.UsePrivateRDNS = s.RDNSSettings()
 	}
 
 	if Context.dhcpServer != nil {
@@ -415,7 +425,7 @@ func (c *configuration) write() error {
 		config.DHCP = c
 	}
 
-	config.Clients = Context.clients.forConfig()
+	config.Clients.Persistent = Context.clients.forConfig()
 
 	configFile := config.getConfigFilename()
 	log.Debug("Writing YAML file: %s", configFile)