Mail reverse DNS check, what Jarl adds to named.conf, lists one per line

jarld checks the reverse DNS of the public zones' MX and SPF addresses as the internet sees it, every 6 hours (Exposure page, jarl exposure mail, jarl_mail_reverse_dns_ok). The Server options page, jarl option generated and GET /options/generated list what Jarl writes into named.conf by itself; stats.rate_limit_log turns off the query-errors logging. Option lists of three or more elements are shown one per line.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/mailcheck/mailcheck_test.go

@@ -0,0 +1,108 @@
+package mailcheck
+
+import (
+	"context"
+	"net"
+	"strings"
+	"testing"
+
+	"github.com/miekg/dns"
+
+	"jarl/internal/model"
+)
+
+// fakeResolver answers from a fixed set of records, as a recursive
+// resolver would, with the reverse zone's SOA in negative answers.
+func fakeResolver(t *testing.T, records ...string) string {
+	t.Helper()
+	var rrs []dns.RR
+	for _, s := range records {
+		rr, err := dns.NewRR(s)
+		if err != nil {
+			t.Fatal(err)
+		}
+		rrs = append(rrs, rr)
+	}
+	soa, _ := dns.NewRR("2.0.192.in-addr.arpa. 3600 IN SOA ns1.linode.com. hostmaster.linode.com. 1 3600 900 1209600 300")
+	pc, err := net.ListenPacket("udp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	srv := &dns.Server{PacketConn: pc, Handler: dns.HandlerFunc(func(w dns.ResponseWriter, q *dns.Msg) {
+		m := new(dns.Msg)
+		m.SetReply(q)
+		qn := strings.ToLower(q.Question[0].Name)
+		for _, rr := range rrs {
+			if strings.ToLower(rr.Header().Name) == qn && (rr.Header().Rrtype == q.Question[0].Qtype || rr.Header().Rrtype == dns.TypeCNAME) {
+				m.Answer = append(m.Answer, rr)
+			}
+		}
+		if len(m.Answer) == 0 && dns.IsSubDomain(soa.Header().Name, qn) {
+			if q.Question[0].Qtype == dns.TypeSOA && qn == soa.Header().Name {
+				m.Answer = append(m.Answer, soa)
+			} else {
+				m.Ns = append(m.Ns, soa)
+			}
+		}
+		w.WriteMsg(m)
+	})}
+	go srv.ActivateAndServe()
+	t.Cleanup(func() { srv.Shutdown() })
+	return pc.LocalAddr().String()
+}
+
+func TestCheck(t *testing.T) {
+	st := model.NewState()
+	ext := &model.View{ID: 1, Name: "external", MatchClients: []string{"any"}}
+	in := &model.View{ID: 2, Name: "internal", MatchClients: []string{"lan"}}
+	st.Views[1], st.Views[2] = ext, in
+	z := &model.Zone{ID: 10, Name: "example.com.", ViewID: 1, Type: model.ZonePrimary}
+	zi := &model.Zone{ID: 11, Name: "example.com.", ViewID: 2, Type: model.ZonePrimary}
+	rev := &model.Zone{ID: 12, Name: "27.2.0.192.in-addr.arpa.", ViewID: 2, Type: model.ZonePrimary}
+	st.Zones[10], st.Zones[11], st.Zones[12] = z, zi, rev
+	rec := func(id, zone int64, name, typ, data string) {
+		st.Records[id] = &model.Record{ID: id, ZoneID: zone, Name: name, Type: typ, Data: data}
+	}
+	rec(1, 10, "example.com.", "MX", "10 mail.example.com.")
+	rec(2, 10, "example.com.", "TXT", `"v=spf1 mx ip4:192.0.2.26 ip4:192.0.2.27" " ip4:198.51.100.0/24 -all"`)
+	rec(3, 10, "www.example.com.", "MX", "10 ignored.example.com.") // not the apex
+	rec(4, 11, "example.com.", "MX", "10 internal.example.com.")    // private view
+	rec(5, 10, "example.com.", "TXT", `"google-site-verification=x"`)
+	rec(6, 10, "example.com.", "MX", "20 backup.example.com.") // not on the internet
+
+	res := Resolver{Servers: []string{fakeResolver(t,
+		"mail.example.com. 300 IN A 192.0.2.25",
+		"25.2.0.192.in-addr.arpa. 300 IN PTR mail.example.com.",
+		"27.2.0.192.in-addr.arpa. 300 IN PTR li-27.members.linode.com.",
+		"li-27.members.linode.com. 300 IN A 192.0.2.99",
+	)}}
+	public := func(id int64) bool { return id == 1 }
+	rep := Check(context.Background(), st, public, res)
+	if len(rep.Errors) != 1 || !strings.Contains(rep.Errors[0], "backup.example.com (example.com, MX backup.example.com) has no address") {
+		t.Fatalf("errors %v", rep.Errors)
+	}
+	got := map[string]Result{}
+	for _, r := range rep.Results {
+		got[r.Address] = r
+	}
+	if len(got) != 3 {
+		t.Fatalf("results %+v", rep.Results)
+	}
+	if r := got["192.0.2.25"]; !r.OK || r.Level != "ok" || r.Roles[0] != "MX mail.example.com" || r.ManagedBy != "" && r.ManagedBy != "linode.com" {
+		t.Errorf("mail: %+v", r)
+	}
+	if r := got["192.0.2.26"]; r.OK || r.Level != "warning" || !strings.Contains(r.Message, "no PTR record") || r.ManagedBy != "linode.com" || r.ReverseZone != "2.0.192.in-addr.arpa" {
+		t.Errorf("no PTR: %+v", r)
+	}
+	if r := got["192.0.2.27"]; r.OK || !strings.Contains(r.Message, "doesn't resolve back") || r.LocalZone != "internal/27.2.0.192.in-addr.arpa" {
+		t.Errorf("not forward-confirmed: %+v", r)
+	}
+}
+
+func TestManagedBy(t *testing.T) {
+	for in, want := range map[string]string{"ns1.linode.com.": "linode.com", "dns0.zen.co.uk.": "zen.co.uk", "ns1.members.linode.com.": "linode.com", "localhost.": "localhost"} {
+		if got := managedBy(in); got != want {
+			t.Errorf("managedBy(%q) = %q, want %q", in, got, want)
+		}
+	}
+}