From b901a1169cc78313298d70cce770cd1523ccbf9f Mon Sep 17 00:00:00 2001
From: Dimitry Kolyshev <dkolyshev@adguard.com>
Date: Tue, 16 Apr 2024 11:03:52 +0200
Subject: [PATCH] dnsforward: imp code

---
 internal/dnsforward/filter.go | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/internal/dnsforward/filter.go b/internal/dnsforward/filter.go
index faff248b..f6cd319d 100644
--- a/internal/dnsforward/filter.go
+++ b/internal/dnsforward/filter.go
@@ -40,12 +40,7 @@ func (s *Server) filterDNSRequest(dctx *dnsContext) (res *filtering.Result, err
 	// TODO(a.garipov): Make CheckHost return a pointer.
 	res = &resVal
 	switch {
-	case res.Reason.In(
-		filtering.Rewritten,
-		filtering.RewrittenRule,
-		filtering.FilteredSafeSearch) &&
-		res.CanonName != "" &&
-		len(res.IPList) == 0:
+	case isRewrittenCNAME(res):
 		// Resolve the new canonical name, not the original host name.  The
 		// original question is readded in processFilteringAfterResponse.
 		dctx.origQuestion = q
@@ -64,6 +59,17 @@ func (s *Server) filterDNSRequest(dctx *dnsContext) (res *filtering.Result, err
 	return res, err
 }
 
+// isRewrittenCNAME returns true if the request considered to be rewritten with
+// CNAME and has no resolved IPs.
+func isRewrittenCNAME(res *filtering.Result) (ok bool) {
+	return res.Reason.In(
+		filtering.Rewritten,
+		filtering.RewrittenRule,
+		filtering.FilteredSafeSearch) &&
+		res.CanonName != "" &&
+		len(res.IPList) == 0
+}
+
 // checkHostRules checks the host against filters.  It is safe for concurrent
 // use.
 func (s *Server) checkHostRules(