all: sync with master

internal/filtering/hosts.go

@@ -0,0 +1,92 @@
+package filtering
+
+import (
+	"fmt"
+	"net/netip"
+
+	"github.com/AdguardTeam/golibs/hostsfile"
+	"github.com/AdguardTeam/golibs/log"
+	"github.com/AdguardTeam/golibs/netutil"
+	"github.com/AdguardTeam/urlfilter/rules"
+	"github.com/miekg/dns"
+)
+
+// matchSysHosts tries to match the host against the operating system's hosts
+// database.  err is always nil.
+func (d *DNSFilter) matchSysHosts(
+	host string,
+	qtype uint16,
+	setts *Settings,
+) (res Result, err error) {
+	// TODO(e.burkov):  Where else is this checked?
+	if !setts.FilteringEnabled || d.conf.EtcHosts == nil {
+		return Result{}, nil
+	}
+
+	vals, rs, matched := hostsRewrites(qtype, host, d.conf.EtcHosts)
+	if !matched {
+		return Result{}, nil
+	}
+
+	return Result{
+		DNSRewriteResult: &DNSRewriteResult{
+			Response: DNSRewriteResultResponse{
+				qtype: vals,
+			},
+			RCode: dns.RcodeSuccess,
+		},
+		Rules:  rs,
+		Reason: RewrittenAutoHosts,
+	}, nil
+}
+
+// hostsRewrites returns values and rules matched by qt and host within hs.
+func hostsRewrites(
+	qtype uint16,
+	host string,
+	hs hostsfile.Storage,
+) (vals []rules.RRValue, rls []*ResultRule, matched bool) {
+	var isValidProto func(netip.Addr) (ok bool)
+	switch qtype {
+	case dns.TypeA:
+		isValidProto = netip.Addr.Is4
+	case dns.TypeAAAA:
+		isValidProto = netip.Addr.Is6
+	case dns.TypePTR:
+		addr, err := netutil.IPFromReversedAddr(host)
+		if err != nil {
+			log.Debug("filtering: failed to parse PTR record %q: %s", host, err)
+
+			return nil, nil, false
+		}
+
+		names := hs.ByAddr(addr)
+
+		for _, name := range names {
+			vals = append(vals, name)
+			rls = append(rls, &ResultRule{
+				Text:         fmt.Sprintf("%s %s", addr, name),
+				FilterListID: SysHostsListID,
+			})
+		}
+
+		return vals, rls, len(names) > 0
+	default:
+		log.Debug("filtering: unsupported qtype %d", qtype)
+
+		return nil, nil, false
+	}
+
+	addrs := hs.ByName(host)
+	for _, addr := range addrs {
+		if isValidProto(addr) {
+			vals = append(vals, addr)
+		}
+		rls = append(rls, &ResultRule{
+			Text:         fmt.Sprintf("%s %s", addr, host),
+			FilterListID: SysHostsListID,
+		})
+	}
+
+	return vals, rls, len(addrs) > 0
+}