Pull request 2389: AG-38975 Update proxy

Merge in DNS/adguard-home from AG-38975-upd-proxy to master

Squashed commit of the following:

commit 94fc1fb9bb1c004fea17d52f586af263b6918694
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Apr 17 20:45:12 2025 +0300

    home: fix typo

commit b1cbf45dcc54c6d4dc7de86868c189114caf7cb1
Merge: c2c868b7d 3521e8ed9
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Apr 17 20:44:14 2025 +0300

    Merge branch 'master' into AG-38975-upd-proxy

commit c2c868b7d938eee6e4e4a19d43b2ed734155c7da
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Apr 17 20:19:23 2025 +0300

    all: upd to tag

commit 1680a9d79f34bd42f0b64712b2e7e968890e7c6e
Merge: df42dec3a 4d258972d
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Apr 16 14:08:46 2025 +0300

    Merge branch 'master' into AG-38975-upd-proxy

commit df42dec3a302af0e6e301365a943763cd87d752d
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Apr 16 13:43:29 2025 +0300

    all: add thanks

commit f212d6a9ee3d614bd6db776204c65298f0359a87
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Apr 14 17:57:33 2025 +0300

    dnsforward: use bool

commit 055072e29dee0673cf38b198476e252bdbade8d9
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Apr 11 18:35:38 2025 +0300

    stats: imp doc

commit 6554101a73564b7786cd77d250344ba141c0cbb5
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Apr 10 19:32:34 2025 +0300

    all: log changes

commit da8ecf17778be9481232222c8bb7682beea475c6
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Apr 10 19:07:04 2025 +0300

    all: upd proxy, add config

internal/dnsforward/config.go

@@ -274,6 +274,10 @@ type ServerConfig struct {
 
 	// ServePlainDNS defines if plain DNS is allowed for incoming requests.
 	ServePlainDNS bool
+
+	// PendingRequestsEnabled defines if duplicate requests should be forwarded
+	// to upstreams along with the original one.
+	PendingRequestsEnabled bool
 }
 
 // UpstreamMode is a enumeration of upstream mode representations.  See
@@ -317,6 +321,9 @@ func (s *Server) newProxyConfig() (conf *proxy.Config, err error) {
 		UsePrivateRDNS:            srvConf.UsePrivateRDNS,
 		PrivateSubnets:            s.privateNets,
 		MessageConstructor:        s,
+		PendingRequests: &proxy.PendingRequestsConfig{
+			Enabled: srvConf.PendingRequestsEnabled,
+		},
 	}
 
 	if srvConf.EDNSClientSubnet.UseCustom {

internal/home/config.go

@@ -263,6 +263,16 @@ type dnsConfig struct {
 	// HostsFileEnabled defines whether to use information from the system hosts
 	// file to resolve queries.
 	HostsFileEnabled bool `yaml:"hostsfile_enabled"`
+
+	// PendingRequests configures duplicate requests policy.
+	PendingRequests *pendingRequests `yaml:"pending_requests"`
+}
+
+// pendingRequests is a block with pending requests configuration.
+type pendingRequests struct {
+	// Enabled controls if duplicate requests should be sent to the upstreams
+	// along with the original one.
+	Enabled bool `yaml:"enabled"`
 }
 
 // tlsConfigSettings is the TLS configuration for DNS-over-TLS, DNS-over-QUIC,
@@ -470,6 +480,9 @@ var config = &configuration{
 		UsePrivateRDNS:   true,
 		ServePlainDNS:    true,
 		HostsFileEnabled: true,
+		PendingRequests: &pendingRequests{
+			Enabled: true,
+		},
 	},
 	TLS: tlsConfigSettings{
 		PortHTTPS:       defaultPortHTTPS,

internal/home/dns.go

@@ -275,6 +275,7 @@ func newServerConfig(
 		ServeHTTP3:             dnsConf.ServeHTTP3,
 		UseHTTP3Upstreams:      dnsConf.UseHTTP3Upstreams,
 		ServePlainDNS:          dnsConf.ServePlainDNS,
+		PendingRequestsEnabled: dnsConf.PendingRequests.Enabled,
 	}
 
 	var initialAddresses []netip.Addr

internal/stats/unit.go

@@ -64,7 +64,7 @@ type Entry struct {
 	Domain string
 
 	// UpstreamStats contains the DNS query statistics for both the upstream and
-	// fallback DNS servers.
+	// fallback DNS servers.  Don't modify items in the slice.
 	UpstreamStats []*proxy.UpstreamStatistics
 
 	// Result is the result of processing the request.