// Copyright (c) Tailscale Inc & AUTHORS // SPDX-License-Identifier: BSD-3-Clause package recursive import ( "context" "errors" "flag" "fmt" "net" "net/netip" "reflect" "strings" "testing" "time" "slices" "github.com/miekg/dns" "tailscale.com/envknob" "tailscale.com/tstest" ) const testDomain = "tailscale.com" // Recursively resolving the AWS console requires being able to handle CNAMEs, // glue records, falling back from UDP to TCP for oversize queries, and more; // it's a great integration test for DNS resolution and they can handle the // traffic :) const complicatedTestDomain = "console.aws.amazon.com" var flagNetworkAccess = flag.Bool("enable-network-access", false, "run tests that need external network access") func init() { envknob.Setenv("TS_DEBUG_RECURSIVE_DNS", "true") } func newResolver(tb testing.TB) *Resolver { clock := tstest.NewClock(tstest.ClockOpts{ Step: 50 * time.Millisecond, }) return &Resolver{ Logf: tb.Logf, timeNow: clock.Now, } } func TestResolve(t *testing.T) { if !*flagNetworkAccess { t.SkipNow() } ctx := context.Background() r := newResolver(t) addrs, minTTL, err := r.Resolve(ctx, testDomain) if err != nil { t.Fatal(err) } t.Logf("addrs: %+v", addrs) t.Logf("minTTL: %v", minTTL) if len(addrs) < 1 { t.Fatalf("expected at least one address") } if minTTL <= 10*time.Second || minTTL >= 24*time.Hour { t.Errorf("invalid minimum TTL: %v", minTTL) } var has4, has6 bool for _, addr := range addrs { has4 = has4 || addr.Is4() has6 = has6 || addr.Is6() } if !has4 { t.Errorf("expected at least one IPv4 address") } if !has6 { t.Errorf("expected at least one IPv6 address") } } func TestResolveComplicated(t *testing.T) { if !*flagNetworkAccess { t.SkipNow() } ctx := context.Background() r := newResolver(t) addrs, minTTL, err := r.Resolve(ctx, complicatedTestDomain) if err != nil { t.Fatal(err) } t.Logf("addrs: %+v", addrs) t.Logf("minTTL: %v", minTTL) if len(addrs) < 1 { t.Fatalf("expected at least one address") } if minTTL <= 10*time.Second || minTTL >= 24*time.Hour { t.Errorf("invalid minimum TTL: %v", minTTL) } } func TestResolveNoIPv6(t *testing.T) { if !*flagNetworkAccess { t.SkipNow() } r := newResolver(t) r.NoIPv6 = true addrs, _, err := r.Resolve(context.Background(), testDomain) if err != nil { t.Fatal(err) } t.Logf("addrs: %+v", addrs) if len(addrs) < 1 { t.Fatalf("expected at least one address") } for _, addr := range addrs { if addr.Is6() { t.Errorf("got unexpected IPv6 address: %v", addr) } } } func TestResolveFallbackToTCP(t *testing.T) { var udpCalls, tcpCalls int hook := func(nameserver netip.Addr, network string, req *dns.Msg) (*dns.Msg, error) { if strings.HasPrefix(network, "udp") { t.Logf("got %q query; returning truncated result", network) udpCalls++ resp := &dns.Msg{} resp.SetReply(req) resp.Truncated = true return resp, nil } t.Logf("got %q query; returning real result", network) tcpCalls++ resp := &dns.Msg{} resp.SetReply(req) resp.Answer = append(resp.Answer, &dns.A{ Hdr: dns.RR_Header{ Name: req.Question[0].Name, Rrtype: req.Question[0].Qtype, Class: dns.ClassINET, Ttl: 300, }, A: net.IPv4(1, 2, 3, 4), }) return resp, nil } r := newResolver(t) r.testExchangeHook = hook ctx := context.Background() resp, err := r.queryNameserverProto(ctx, 0, "tailscale.com", netip.MustParseAddr("9.9.9.9"), "udp", dns.Type(dns.TypeA)) if err != nil { t.Fatal(err) } if len(resp.Answer) < 1 { t.Fatalf("no answers in response: %v", resp) } rrA, ok := resp.Answer[0].(*dns.A) if !ok { t.Fatalf("invalid RR type: %T", resp.Answer[0]) } if !rrA.A.Equal(net.IPv4(1, 2, 3, 4)) { t.Errorf("wanted A response 1.2.3.4, got: %v", rrA.A) } if tcpCalls != 1 { t.Errorf("got %d, want 1 TCP calls", tcpCalls) } if udpCalls != 1 { t.Errorf("got %d, want 1 UDP calls", udpCalls) } // Verify that we're cached and re-run to fetch from the cache. if len(r.queryCache) < 1 { t.Errorf("wanted entries in the query cache") } resp2, err := r.queryNameserverProto(ctx, 0, "tailscale.com", netip.MustParseAddr("9.9.9.9"), "udp", dns.Type(dns.TypeA)) if err != nil { t.Fatal(err) } if !reflect.DeepEqual(resp, resp2) { t.Errorf("expected equal responses; old=%+v new=%+v", resp, resp2) } // We didn't make any more network requests since we loaded from the cache. if tcpCalls != 1 { t.Errorf("got %d, want 1 TCP calls", tcpCalls) } if udpCalls != 1 { t.Errorf("got %d, want 1 UDP calls", udpCalls) } } func dnsIPRR(name string, addr netip.Addr) dns.RR { if addr.Is4() { return &dns.A{ Hdr: dns.RR_Header{ Name: name, Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 300, }, A: net.IP(addr.AsSlice()), } } return &dns.AAAA{ Hdr: dns.RR_Header{ Name: name, Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: 300, }, AAAA: net.IP(addr.AsSlice()), } } func cnameRR(name, target string) dns.RR { return &dns.CNAME{ Hdr: dns.RR_Header{ Name: name, Rrtype: dns.TypeCNAME, Class: dns.ClassINET, Ttl: 300, }, Target: target, } } func nsRR(name, target string) dns.RR { return &dns.NS{ Hdr: dns.RR_Header{ Name: name, Rrtype: dns.TypeNS, Class: dns.ClassINET, Ttl: 300, }, Ns: target, } } type mockReply struct { name string qtype dns.Type resp *dns.Msg } type replyMock struct { tb testing.TB replies map[netip.Addr][]mockReply } func (r *replyMock) exchangeHook(nameserver netip.Addr, network string, req *dns.Msg) (*dns.Msg, error) { if len(req.Question) != 1 { r.tb.Fatalf("unsupported multiple or empty question: %v", req.Question) } question := req.Question[0] replies := r.replies[nameserver] if len(replies) == 0 { r.tb.Fatalf("no configured replies for nameserver: %v", nameserver) } for _, reply := range replies { if reply.name == question.Name && reply.qtype == dns.Type(question.Qtype) { return reply.resp.Copy(), nil } } r.tb.Fatalf("no replies found for query %q of type %v to %v", question.Name, question.Qtype, nameserver) panic("unreachable") } // responses for mocking, shared between the following tests var ( rootServerAddr = netip.MustParseAddr("198.41.0.4") // a.root-servers.net. comNSAddr = netip.MustParseAddr("192.5.6.30") // a.gtld-servers.net. // DNS response from the root nameservers for a .com nameserver comRecord = &dns.Msg{ Ns: []dns.RR{nsRR("com.", "a.gtld-servers.net.")}, Extra: []dns.RR{dnsIPRR("a.gtld-servers.net.", comNSAddr)}, } // Random Amazon nameservers that we use in glue records amazonNS = netip.MustParseAddr("205.251.192.197") amazonNSv6 = netip.MustParseAddr("2600:9000:5306:1600::1") // Nameservers for the tailscale.com domain tailscaleNameservers = &dns.Msg{ Ns: []dns.RR{ nsRR("tailscale.com.", "ns-197.awsdns-24.com."), nsRR("tailscale.com.", "ns-557.awsdns-05.net."), nsRR("tailscale.com.", "ns-1558.awsdns-02.co.uk."), nsRR("tailscale.com.", "ns-1359.awsdns-41.org."), }, Extra: []dns.RR{ dnsIPRR("ns-197.awsdns-24.com.", amazonNS), }, } ) func TestBasicRecursion(t *testing.T) { mock := &replyMock{ tb: t, replies: map[netip.Addr][]mockReply{ // Query to the root server returns the .com server + a glue record rootServerAddr: { {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: comRecord}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: comRecord}, }, // Query to the ".com" server return the nameservers for tailscale.com comNSAddr: { {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: tailscaleNameservers}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: tailscaleNameservers}, }, // Query to the actual nameserver works. amazonNS: { {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{ dnsIPRR("tailscale.com.", netip.MustParseAddr("13.248.141.131")), dnsIPRR("tailscale.com.", netip.MustParseAddr("76.223.15.28")), }, }}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{ dnsIPRR("tailscale.com.", netip.MustParseAddr("2600:9000:a602:b1e6:86d:8165:5e8c:295b")), dnsIPRR("tailscale.com.", netip.MustParseAddr("2600:9000:a51d:27c1:1530:b9ef:2a6:b9e5")), }, }}, }, }, } r := newResolver(t) r.testExchangeHook = mock.exchangeHook r.rootServers = []netip.Addr{rootServerAddr} // Query for tailscale.com, verify we get the right responses ctx := context.Background() addrs, minTTL, err := r.Resolve(ctx, "tailscale.com") if err != nil { t.Fatal(err) } wantAddrs := []netip.Addr{ netip.MustParseAddr("13.248.141.131"), netip.MustParseAddr("76.223.15.28"), netip.MustParseAddr("2600:9000:a602:b1e6:86d:8165:5e8c:295b"), netip.MustParseAddr("2600:9000:a51d:27c1:1530:b9ef:2a6:b9e5"), } slices.SortFunc(addrs, func(x, y netip.Addr) int { return strings.Compare(x.String(), y.String()) }) slices.SortFunc(wantAddrs, func(x, y netip.Addr) int { return strings.Compare(x.String(), y.String()) }) if !reflect.DeepEqual(addrs, wantAddrs) { t.Errorf("got addrs=%+v; want %+v", addrs, wantAddrs) } const wantMinTTL = 5 * time.Minute if minTTL != wantMinTTL { t.Errorf("got minTTL=%+v; want %+v", minTTL, wantMinTTL) } } func TestNoAnswers(t *testing.T) { mock := &replyMock{ tb: t, replies: map[netip.Addr][]mockReply{ // Query to the root server returns the .com server + a glue record rootServerAddr: { {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: comRecord}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: comRecord}, }, // Query to the ".com" server return the nameservers for tailscale.com comNSAddr: { {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: tailscaleNameservers}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: tailscaleNameservers}, }, // Query to the actual nameserver returns no responses, authoritatively. amazonNS: { {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{}, }}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{}, }}, }, }, } r := &Resolver{ Logf: t.Logf, testExchangeHook: mock.exchangeHook, rootServers: []netip.Addr{rootServerAddr}, } // Query for tailscale.com, verify we get the right responses _, _, err := r.Resolve(context.Background(), "tailscale.com") if err == nil { t.Fatalf("got no error, want error") } if !errors.Is(err, ErrAuthoritativeNoResponses) { t.Fatalf("got err=%v, want %v", err, ErrAuthoritativeNoResponses) } } func TestRecursionCNAME(t *testing.T) { mock := &replyMock{ tb: t, replies: map[netip.Addr][]mockReply{ // Query to the root server returns the .com server + a glue record rootServerAddr: { {name: "subdomain.otherdomain.com.", qtype: dns.Type(dns.TypeA), resp: comRecord}, {name: "subdomain.otherdomain.com.", qtype: dns.Type(dns.TypeAAAA), resp: comRecord}, {name: "subdomain.tailscale.com.", qtype: dns.Type(dns.TypeA), resp: comRecord}, {name: "subdomain.tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: comRecord}, }, // Query to the ".com" server return the nameservers for tailscale.com comNSAddr: { {name: "subdomain.otherdomain.com.", qtype: dns.Type(dns.TypeA), resp: tailscaleNameservers}, {name: "subdomain.otherdomain.com.", qtype: dns.Type(dns.TypeAAAA), resp: tailscaleNameservers}, {name: "subdomain.tailscale.com.", qtype: dns.Type(dns.TypeA), resp: tailscaleNameservers}, {name: "subdomain.tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: tailscaleNameservers}, }, // Query to the actual nameserver works. amazonNS: { {name: "subdomain.otherdomain.com.", qtype: dns.Type(dns.TypeA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{cnameRR("subdomain.otherdomain.com.", "subdomain.tailscale.com.")}, }}, {name: "subdomain.otherdomain.com.", qtype: dns.Type(dns.TypeAAAA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{cnameRR("subdomain.otherdomain.com.", "subdomain.tailscale.com.")}, }}, {name: "subdomain.tailscale.com.", qtype: dns.Type(dns.TypeA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{dnsIPRR("tailscale.com.", netip.MustParseAddr("13.248.141.131"))}, }}, {name: "subdomain.tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{dnsIPRR("tailscale.com.", netip.MustParseAddr("2600:9000:a602:b1e6:86d:8165:5e8c:295b"))}, }}, }, }, } r := &Resolver{ Logf: t.Logf, testExchangeHook: mock.exchangeHook, rootServers: []netip.Addr{rootServerAddr}, } // Query for tailscale.com, verify we get the right responses addrs, minTTL, err := r.Resolve(context.Background(), "subdomain.otherdomain.com") if err != nil { t.Fatal(err) } wantAddrs := []netip.Addr{ netip.MustParseAddr("13.248.141.131"), netip.MustParseAddr("2600:9000:a602:b1e6:86d:8165:5e8c:295b"), } slices.SortFunc(addrs, func(x, y netip.Addr) int { return strings.Compare(x.String(), y.String()) }) slices.SortFunc(wantAddrs, func(x, y netip.Addr) int { return strings.Compare(x.String(), y.String()) }) if !reflect.DeepEqual(addrs, wantAddrs) { t.Errorf("got addrs=%+v; want %+v", addrs, wantAddrs) } const wantMinTTL = 5 * time.Minute if minTTL != wantMinTTL { t.Errorf("got minTTL=%+v; want %+v", minTTL, wantMinTTL) } } func TestRecursionNoGlue(t *testing.T) { coukNS := netip.MustParseAddr("213.248.216.1") coukRecord := &dns.Msg{ Ns: []dns.RR{nsRR("com.", "dns1.nic.uk.")}, Extra: []dns.RR{dnsIPRR("dns1.nic.uk.", coukNS)}, } intermediateNS := netip.MustParseAddr("205.251.193.66") // g-ns-322.awsdns-02.co.uk. intermediateRecord := &dns.Msg{ Ns: []dns.RR{nsRR("awsdns-02.co.uk.", "g-ns-322.awsdns-02.co.uk.")}, Extra: []dns.RR{dnsIPRR("g-ns-322.awsdns-02.co.uk.", intermediateNS)}, } const amazonNameserver = "ns-1558.awsdns-02.co.uk." tailscaleNameservers := &dns.Msg{ Ns: []dns.RR{ nsRR("tailscale.com.", amazonNameserver), }, } tailscaleResponses := []mockReply{ {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{dnsIPRR("tailscale.com.", netip.MustParseAddr("13.248.141.131"))}, }}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{dnsIPRR("tailscale.com.", netip.MustParseAddr("2600:9000:a602:b1e6:86d:8165:5e8c:295b"))}, }}, } mock := &replyMock{ tb: t, replies: map[netip.Addr][]mockReply{ rootServerAddr: { // Query to the root server returns the .com server + a glue record {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: comRecord}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: comRecord}, // Querying the .co.uk nameserver returns the .co.uk nameserver + a glue record. {name: amazonNameserver, qtype: dns.Type(dns.TypeA), resp: coukRecord}, {name: amazonNameserver, qtype: dns.Type(dns.TypeAAAA), resp: coukRecord}, }, // Queries to the ".com" server return the nameservers // for tailscale.com, which don't contain a glue // record. comNSAddr: { {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: tailscaleNameservers}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: tailscaleNameservers}, }, // Queries to the ".co.uk" nameserver returns the // address of the intermediate Amazon nameserver. coukNS: { {name: amazonNameserver, qtype: dns.Type(dns.TypeA), resp: intermediateRecord}, {name: amazonNameserver, qtype: dns.Type(dns.TypeAAAA), resp: intermediateRecord}, }, // Queries to the intermediate nameserver returns an // answer for the final Amazon nameserver. intermediateNS: { {name: amazonNameserver, qtype: dns.Type(dns.TypeA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{dnsIPRR(amazonNameserver, amazonNS)}, }}, {name: amazonNameserver, qtype: dns.Type(dns.TypeAAAA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{dnsIPRR(amazonNameserver, amazonNSv6)}, }}, }, // Queries to the actual nameserver work and return // responses to the query. amazonNS: tailscaleResponses, amazonNSv6: tailscaleResponses, }, } r := newResolver(t) r.testExchangeHook = mock.exchangeHook r.rootServers = []netip.Addr{rootServerAddr} // Query for tailscale.com, verify we get the right responses addrs, minTTL, err := r.Resolve(context.Background(), "tailscale.com") if err != nil { t.Fatal(err) } wantAddrs := []netip.Addr{ netip.MustParseAddr("13.248.141.131"), netip.MustParseAddr("2600:9000:a602:b1e6:86d:8165:5e8c:295b"), } slices.SortFunc(addrs, func(x, y netip.Addr) int { return strings.Compare(x.String(), y.String()) }) slices.SortFunc(wantAddrs, func(x, y netip.Addr) int { return strings.Compare(x.String(), y.String()) }) if !reflect.DeepEqual(addrs, wantAddrs) { t.Errorf("got addrs=%+v; want %+v", addrs, wantAddrs) } const wantMinTTL = 5 * time.Minute if minTTL != wantMinTTL { t.Errorf("got minTTL=%+v; want %+v", minTTL, wantMinTTL) } } func TestRecursionLimit(t *testing.T) { mock := &replyMock{ tb: t, replies: map[netip.Addr][]mockReply{}, } // Fill out a CNAME chain equal to our recursion limit; we won't get // this far since each CNAME is more than 1 level "deep", but this // ensures that we have more than the limit. for i := range maxDepth + 1 { curr := fmt.Sprintf("%d-tailscale.com.", i) tailscaleNameservers := &dns.Msg{ Ns: []dns.RR{nsRR(curr, "ns-197.awsdns-24.com.")}, Extra: []dns.RR{dnsIPRR("ns-197.awsdns-24.com.", amazonNS)}, } // Query to the root server returns the .com server + a glue record mock.replies[rootServerAddr] = append(mock.replies[rootServerAddr], mockReply{name: curr, qtype: dns.Type(dns.TypeA), resp: comRecord}, mockReply{name: curr, qtype: dns.Type(dns.TypeAAAA), resp: comRecord}, ) // Query to the ".com" server return the nameservers for NN-tailscale.com mock.replies[comNSAddr] = append(mock.replies[comNSAddr], mockReply{name: curr, qtype: dns.Type(dns.TypeA), resp: tailscaleNameservers}, mockReply{name: curr, qtype: dns.Type(dns.TypeAAAA), resp: tailscaleNameservers}, ) // Queries to the nameserver return a CNAME for the n+1th server. next := fmt.Sprintf("%d-tailscale.com.", i+1) mock.replies[amazonNS] = append(mock.replies[amazonNS], mockReply{ name: curr, qtype: dns.Type(dns.TypeA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{cnameRR(curr, next)}, }, }, mockReply{ name: curr, qtype: dns.Type(dns.TypeAAAA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{cnameRR(curr, next)}, }, }, ) } r := newResolver(t) r.testExchangeHook = mock.exchangeHook r.rootServers = []netip.Addr{rootServerAddr} // Query for the first node in the chain, 0-tailscale.com, and verify // we get a max-depth error. ctx := context.Background() _, _, err := r.Resolve(ctx, "0-tailscale.com") if err == nil { t.Fatal("expected error, got nil") } else if !errors.Is(err, ErrMaxDepth) { t.Fatalf("got err=%v, want ErrMaxDepth", err) } } func TestInvalidResponses(t *testing.T) { mock := &replyMock{ tb: t, replies: map[netip.Addr][]mockReply{ // Query to the root server returns the .com server + a glue record rootServerAddr: { {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: comRecord}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: comRecord}, }, // Query to the ".com" server return the nameservers for tailscale.com comNSAddr: { {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: tailscaleNameservers}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: tailscaleNameservers}, }, // Query to the actual nameserver returns an invalid IP address amazonNS: { {name: "tailscale.com.", qtype: dns.Type(dns.TypeA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, Answer: []dns.RR{&dns.A{ Hdr: dns.RR_Header{ Name: "tailscale.com.", Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 300, }, // Note: this is an IPv6 addr in an IPv4 response A: net.IP(netip.MustParseAddr("2600:9000:a51d:27c1:1530:b9ef:2a6:b9e5").AsSlice()), }}, }}, {name: "tailscale.com.", qtype: dns.Type(dns.TypeAAAA), resp: &dns.Msg{ MsgHdr: dns.MsgHdr{Authoritative: true}, // This an IPv4 response to an IPv6 query Answer: []dns.RR{&dns.A{ Hdr: dns.RR_Header{ Name: "tailscale.com.", Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 300, }, A: net.IP(netip.MustParseAddr("13.248.141.131").AsSlice()), }}, }}, }, }, } r := &Resolver{ Logf: t.Logf, testExchangeHook: mock.exchangeHook, rootServers: []netip.Addr{rootServerAddr}, } // Query for tailscale.com, verify we get no responses since the // addresses are invalid. _, _, err := r.Resolve(context.Background(), "tailscale.com") if err == nil { t.Fatalf("got no error, want error") } if !errors.Is(err, ErrAuthoritativeNoResponses) { t.Fatalf("got err=%v, want %v", err, ErrAuthoritativeNoResponses) } } // TODO(andrew): test for more edge cases that aren't currently covered: // * Nameservers that cross between IPv4 and IPv6 // * Authoritative no replies after following CNAME // * Authoritative no replies after following non-glue NS record // * Error querying non-glue NS record followed by success