Pull request: all: less annoying pkg names

Merge in DNS/adguard-home from imp-naming to master

Squashed commit of the following:

commit d9e75c37af9a738384393735c141a41406d22eeb
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu May 13 15:52:14 2021 +0300

    all: less annoying pkg names

internal/filtering/dnsrewrite.go

@@ -0,0 +1,80 @@
+package filtering
+
+import (
+	"github.com/AdguardTeam/urlfilter/rules"
+	"github.com/miekg/dns"
+)
+
+// DNSRewriteResult is the result of application of $dnsrewrite rules.
+type DNSRewriteResult struct {
+	Response DNSRewriteResultResponse `json:",omitempty"`
+	RCode    rules.RCode              `json:",omitempty"`
+}
+
+// DNSRewriteResultResponse is the collection of DNS response records
+// the server returns.
+type DNSRewriteResultResponse map[rules.RRType][]rules.RRValue
+
+// processDNSRewrites processes DNS rewrite rules in dnsr.  It returns
+// an empty result if dnsr is empty.  Otherwise, the result will have
+// either CanonName or DNSRewriteResult set.
+func (d *DNSFilter) processDNSRewrites(dnsr []*rules.NetworkRule) (res Result) {
+	if len(dnsr) == 0 {
+		return Result{}
+	}
+
+	var rules []*ResultRule
+	dnsrr := &DNSRewriteResult{
+		Response: DNSRewriteResultResponse{},
+	}
+
+	for _, nr := range dnsr {
+		dr := nr.DNSRewrite
+		if dr.NewCNAME != "" {
+			// NewCNAME rules have a higher priority than
+			// the other rules.
+			rules = []*ResultRule{{
+				FilterListID: int64(nr.GetFilterListID()),
+				Text:         nr.RuleText,
+			}}
+
+			return Result{
+				Reason:    RewrittenRule,
+				Rules:     rules,
+				CanonName: dr.NewCNAME,
+			}
+		}
+
+		switch dr.RCode {
+		case dns.RcodeSuccess:
+			dnsrr.RCode = dr.RCode
+			dnsrr.Response[dr.RRType] = append(dnsrr.Response[dr.RRType], dr.Value)
+			rules = append(rules, &ResultRule{
+				FilterListID: int64(nr.GetFilterListID()),
+				Text:         nr.RuleText,
+			})
+		default:
+			// RcodeRefused and other such codes have higher
+			// priority.  Return immediately.
+			rules = []*ResultRule{{
+				FilterListID: int64(nr.GetFilterListID()),
+				Text:         nr.RuleText,
+			}}
+			dnsrr = &DNSRewriteResult{
+				RCode: dr.RCode,
+			}
+
+			return Result{
+				Reason:           RewrittenRule,
+				Rules:            rules,
+				DNSRewriteResult: dnsrr,
+			}
+		}
+	}
+
+	return Result{
+		Reason:           RewrittenRule,
+		Rules:            rules,
+		DNSRewriteResult: dnsrr,
+	}
+}