Pull request: AGDNS-3523-imp-proxy

Merge in GO/dnsproxy from AGDNS-3523-imp-proxy to master

Squashed commit of the following:

commit c60921e
Author: Dimitry Kolyshev <dkolyshev@adguard.com>
Date:   Thu Feb 19 12:09:12 2026 +0700

    proxy: rm BeforeRequestHandler

Author: Mizzick

proxy/beforerequest.go

@@ -55,11 +55,6 @@ type Config struct {
 	// performing a single lookup.  If nil, it will be enabled by default.
 	PendingRequests *PendingRequestsConfig
 
-	// BeforeRequestHandler is an optional custom handler called before each DNS
-	// request is started processing, see [BeforeRequestHandler].  The default
-	// no-op implementation is used, if it's nil.
-	BeforeRequestHandler BeforeRequestHandler
-
 	// RequestHandler is an optional custom handler for DNS requests.  It's used
 	// instead of DefaultHandler if set.  In case of [ErrDrop] error returned
 	// from this handler, the proxy will not send any response to the client.

proxy/beforerequest_internal_test.go

@@ -87,11 +87,7 @@ type Proxy struct {
 	// messages constructs DNS messages.
 	messages MessageConstructor
 
-	// beforeRequestHandler handles the request's context before it is resolved.
-	beforeRequestHandler BeforeRequestHandler
-
-	// requestHandler handles the DNS request after it's been processed by the
-	// beforeRequestHandler.  It is never nil.
+	// requestHandler handles the DNS request.  It is never nil.
 	requestHandler Handler
 
 	// dnsCryptServer serves DNSCrypt queries.
@@ -219,10 +215,6 @@ func New(c *Config) (p *Proxy, err error) {
 			c.PrivateSubnets,
 			netutil.SubnetSetFunc(netutil.IsLocallyServed),
 		),
-		beforeRequestHandler: cmp.Or[BeforeRequestHandler](
-			c.BeforeRequestHandler,
-			noopRequestHandler{},
-		),
 		requestHandler:   cmp.Or[Handler](c.RequestHandler, DefaultHandler{}),
 		upstreamRTTStats: map[string]upstreamRTTStats{},
 		rttLock:          sync.Mutex{},

proxy/config.go

@@ -89,9 +89,7 @@ func (p *Proxy) serveListeners() {
 }
 
 // handleDNSRequest processes the context.  The only error it returns is the one
-// from the [Handler], or [Resolve] if the [Handler] is not set.  d is left
-// without a response as the documentation to [BeforeRequestHandler] says, and
-// if it's ratelimited.
+// from the [Handler], or [Resolve] if the [Handler] is not set.
 func (p *Proxy) handleDNSRequest(d *DNSContext) (err error) {
 	p.logDNSMessage(d.Req)
 
@@ -104,10 +102,6 @@ func (p *Proxy) handleDNSRequest(d *DNSContext) (err error) {
 	ip := d.Addr.Addr()
 	d.IsPrivateClient = p.privateNets.Contains(ip)
 
-	if !p.handleBefore(d) {
-		return nil
-	}
-
 	// TODO(d.kolyshev):  Consider moving validation to a new middleware.
 	d.Res = p.validateRequest(d)
 	if d.Res == nil {