add local plugin (#4262)

* add local plugin See: #4260 Signed-off-by: Miek Gieben <miek@miek.nl> * stickler bot Signed-off-by: Miek Gieben <miek@miek.nl> * See Also Signed-off-by: Miek Gieben <miek@miek.nl>
2025-10-27 16:24:19 -04:00 · 2020-11-05 15:02:07 +01:00
parent b091eff139
commit 7bbcf6920f
9 changed files with 364 additions and 0 deletions
--- a/plugin/local/local.go
+++ b/plugin/local/local.go
@@ -0,0 +1,127 @@
+package local
+
+import (
+	"context"
+	"net"
+	"strings"
+
+	"github.com/coredns/coredns/plugin"
+	clog "github.com/coredns/coredns/plugin/pkg/log"
+	"github.com/coredns/coredns/request"
+
+	"github.com/miekg/dns"
+)
+
+var log = clog.NewWithPlugin("local")
+
+// Local is a plugin that returns standard replies for local queries.
+type Local struct {
+	Next plugin.Handler
+}
+
+var zones = []string{"localhost.", "0.in-addr.arpa.", "127.in-addr.arpa.", "255.in-addr.arpa."}
+
+func soaFromOrigin(origin string) []dns.RR {
+	hdr := dns.RR_Header{Name: origin, Ttl: ttl, Class: dns.ClassINET, Rrtype: dns.TypeSOA}
+	return []dns.RR{&dns.SOA{Hdr: hdr, Ns: "localhost.", Mbox: "root.localhost.", Serial: 1, Refresh: 0, Retry: 0, Expire: 0, Minttl: ttl}}
+}
+
+func nsFromOrigin(origin string) []dns.RR {
+	hdr := dns.RR_Header{Name: origin, Ttl: ttl, Class: dns.ClassINET, Rrtype: dns.TypeNS}
+	return []dns.RR{&dns.NS{Hdr: hdr, Ns: "localhost."}}
+}
+
+// ServeDNS implements the plugin.Handler interface.
+func (l Local) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	state := request.Request{W: w, Req: r}
+	qname := state.QName()
+
+	lc := len("localhost.")
+	if len(state.Name()) > lc && strings.HasPrefix(state.Name(), "localhost.") {
+		// we have multiple labels, but the first one is localhost, intercept this and return 127.0.0.1 or ::1
+		log.Debugf("Intercepting localhost query for %q %s, from %s", state.Name(), state.Type(), state.IP())
+		LocalhostCount.Inc()
+		reply := doLocalhost(state)
+		w.WriteMsg(reply)
+		return 0, nil
+	}
+
+	zone := plugin.Zones(zones).Matches(qname)
+	if zone == "" {
+		return plugin.NextOrFailure(l.Name(), l.Next, ctx, w, r)
+	}
+
+	m := new(dns.Msg)
+	m.SetReply(r)
+	zone = qname[len(qname)-len(zone):]
+
+	switch q := state.Name(); q {
+	case "localhost.", "0.in-addr.arpa.", "127.in-addr.arpa.", "255.in-addr.arpa.":
+		switch state.QType() {
+		case dns.TypeA:
+			if q != "localhost." {
+				// nodata
+				m.Ns = soaFromOrigin(qname)
+				break
+			}
+
+			hdr := dns.RR_Header{Name: qname, Ttl: ttl, Class: dns.ClassINET, Rrtype: dns.TypeA}
+			m.Answer = []dns.RR{&dns.A{Hdr: hdr, A: net.ParseIP("127.0.0.1").To4()}}
+		case dns.TypeAAAA:
+			if q != "localhost." {
+				// nodata
+				m.Ns = soaFromOrigin(qname)
+				break
+			}
+
+			hdr := dns.RR_Header{Name: qname, Ttl: ttl, Class: dns.ClassINET, Rrtype: dns.TypeAAAA}
+			m.Answer = []dns.RR{&dns.AAAA{Hdr: hdr, AAAA: net.ParseIP("::1")}}
+		case dns.TypeSOA:
+			m.Answer = soaFromOrigin(qname)
+		case dns.TypeNS:
+			m.Answer = nsFromOrigin(qname)
+		default:
+			// nodata
+			m.Ns = soaFromOrigin(qname)
+		}
+	case "1.0.0.127.in-addr.arpa.":
+		switch state.QType() {
+		case dns.TypePTR:
+			hdr := dns.RR_Header{Name: qname, Ttl: ttl, Class: dns.ClassINET, Rrtype: dns.TypePTR}
+			m.Answer = []dns.RR{&dns.PTR{Hdr: hdr, Ptr: "localhost."}}
+		default:
+			// nodata
+			m.Ns = soaFromOrigin(zone)
+		}
+	}
+
+	if len(m.Answer) == 0 && len(m.Ns) == 0 {
+		m.Ns = soaFromOrigin(zone)
+		m.Rcode = dns.RcodeNameError
+	}
+
+	w.WriteMsg(m)
+	return 0, nil
+}
+
+// Name implements the plugin.Handler interface.
+func (l Local) Name() string { return "local" }
+
+func doLocalhost(state request.Request) *dns.Msg {
+	m := new(dns.Msg)
+	m.SetReply(state.Req)
+	switch state.QType() {
+	case dns.TypeA:
+		hdr := dns.RR_Header{Name: state.QName(), Ttl: ttl, Class: dns.ClassINET, Rrtype: dns.TypeA}
+		m.Answer = []dns.RR{&dns.A{Hdr: hdr, A: net.ParseIP("127.0.0.1").To4()}}
+	case dns.TypeAAAA:
+		hdr := dns.RR_Header{Name: state.QName(), Ttl: ttl, Class: dns.ClassINET, Rrtype: dns.TypeAAAA}
+		m.Answer = []dns.RR{&dns.AAAA{Hdr: hdr, AAAA: net.ParseIP("::1")}}
+	default:
+		// nodata
+		m.Ns = soaFromOrigin(state.QName())
+	}
+	return m
+}
+
+const ttl = 604800