feat: context-based tracing to record delayed DNS responses (#870)
See https://github.com/ooni/probe/issues/2221 Co-authored-by: decfox <decfox@github.com> Co-authored-by: Simone Basso <bassosimone@gmail.com>
This commit is contained in:
DecFox
GitHub
parent
fe6d378a1f
commit
2301a30630
10 changed files with 498 additions and 317 deletions
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@ -5,6 +5,7 @@ import (
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"context"
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"errors"
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"net"
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"sync"
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"testing"
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"time"
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@ -14,6 +15,7 @@ import (
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"github.com/ooni/probe-cli/v3/internal/model"
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"github.com/ooni/probe-cli/v3/internal/model/mocks"
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"github.com/ooni/probe-cli/v3/internal/netxlite/filtering"
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"github.com/ooni/probe-cli/v3/internal/testingx"
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)
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func TestDNSOverUDPTransport(t *testing.T) {
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@ -281,70 +283,16 @@ func TestDNSOverUDPTransport(t *testing.T) {
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})
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})
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t.Run("AsyncRoundTrip", func(t *testing.T) {
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t.Run("calling Next with cancelled context", func(t *testing.T) {
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srvr := &filtering.DNSServer{
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OnQuery: func(domain string) filtering.DNSAction {
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return filtering.DNSActionCache
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},
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Cache: map[string][]string{
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"dns.google.": {"8.8.8.8"},
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},
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}
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listener, err := srvr.Start("127.0.0.1:0")
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if err != nil {
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t.Fatal(err)
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}
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defer listener.Close()
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dialer := NewDialerWithoutResolver(model.DiscardLogger)
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txp := NewUnwrappedDNSOverUDPTransport(dialer, listener.LocalAddr().String())
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encoder := &DNSEncoderMiekg{}
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query := encoder.Encode("dns.google.", dns.TypeA, false)
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ctx := context.Background()
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rch, err := txp.AsyncRoundTrip(ctx, query, 1)
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if err != nil {
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t.Fatal(err)
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}
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defer rch.Close()
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ctx, cancel := context.WithCancel(ctx)
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cancel() // fail immediately
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resp, err := rch.Next(ctx)
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if !errors.Is(err, context.Canceled) {
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t.Fatal("unexpected err", err)
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}
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if resp != nil {
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t.Fatal("unexpected resp")
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}
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})
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t.Run("no-one is reading the channel", func(t *testing.T) {
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srvr := &filtering.DNSServer{
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OnQuery: func(domain string) filtering.DNSAction {
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return filtering.DNSActionLocalHostPlusCache // i.e., two responses
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},
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Cache: map[string][]string{
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"dns.google.": {"8.8.8.8"},
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},
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}
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listener, err := srvr.Start("127.0.0.1:0")
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if err != nil {
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t.Fatal(err)
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}
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defer listener.Close()
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dialer := NewDialerWithoutResolver(model.DiscardLogger)
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txp := NewUnwrappedDNSOverUDPTransport(dialer, listener.LocalAddr().String())
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encoder := &DNSEncoderMiekg{}
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query := encoder.Encode("dns.google.", dns.TypeA, false)
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ctx := context.Background()
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rch, err := txp.AsyncRoundTrip(ctx, query, 1) // but just one place
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if err != nil {
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t.Fatal(err)
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}
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defer rch.Close()
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<-rch.Joined // should see no-one is reading and stop
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})
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t.Run("typical usage to obtain late responses", func(t *testing.T) {
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t.Run("recording delayed DNS responses", func(t *testing.T) {
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t.Run("uses a context-injected custom trace (success case)", func(t *testing.T) {
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var (
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delayedDNSResponseCalled bool
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goodQueryType bool
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goodTransportNetwork bool
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goodTransportAddress bool
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goodLookupAddrs bool
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goodError bool
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)
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srvr := &filtering.DNSServer{
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OnQuery: func(domain string) filtering.DNSAction {
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return filtering.DNSActionLocalHostPlusCache
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@ -359,52 +307,94 @@ func TestDNSOverUDPTransport(t *testing.T) {
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}
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defer listener.Close()
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dialer := NewDialerWithoutResolver(model.DiscardLogger)
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txp := NewUnwrappedDNSOverUDPTransport(dialer, listener.LocalAddr().String())
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expectedAddress := listener.LocalAddr().String()
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txp := NewUnwrappedDNSOverUDPTransport(dialer, expectedAddress)
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encoder := &DNSEncoderMiekg{}
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query := encoder.Encode("dns.google.", dns.TypeA, false)
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rch, err := txp.AsyncRoundTrip(context.Background(), query, 1)
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zeroTime := time.Now()
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deterministicTime := testingx.NewTimeDeterministic(zeroTime)
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expectedAddrs := []string{"8.8.8.8"}
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respChannel := make(chan *model.DNSResponse, 8)
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mu := new(sync.Mutex)
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tx := &mocks.Trace{
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MockTimeNow: deterministicTime.Now,
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MockOnDelayedDNSResponse: func(started time.Time, txp model.DNSTransport,
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query model.DNSQuery, response model.DNSResponse, addrs []string, err error,
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finished time.Time) error {
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mu.Lock()
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delayedDNSResponseCalled = true
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goodQueryType = (query.Type() == dns.TypeA)
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goodTransportNetwork = (txp.Network() == "udp")
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goodTransportAddress = (txp.Address() == expectedAddress)
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goodLookupAddrs = (cmp.Diff(expectedAddrs, addrs) == "")
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goodError = (err == nil)
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mu.Unlock()
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select {
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case respChannel <- &response:
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return nil
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default:
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return errors.New("full buffer")
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}
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},
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MockOnConnectDone: func(started time.Time, network, domain, remoteAddr string, err error,
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finished time.Time) {
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// do nothing
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},
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MockMaybeWrapNetConn: func(conn net.Conn) net.Conn {
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return conn
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},
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}
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ctx := ContextWithTrace(context.Background(), tx)
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rch, err := txp.RoundTrip(ctx, query)
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<-respChannel // wait for the delayed response
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if err != nil {
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t.Fatal(err)
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}
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defer rch.Close()
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resp, err := rch.Next(context.Background())
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if err != nil {
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t.Fatal(err)
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}
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addrs, err := resp.DecodeLookupHost()
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addrs, err := rch.DecodeLookupHost()
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if err != nil {
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t.Fatal(err)
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}
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mu.Lock()
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if diff := cmp.Diff(addrs, []string{"127.0.0.1"}); diff != "" {
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t.Fatal(diff)
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}
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// One would not normally busy loop but it's fine to do that in the context
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// of this test because we know we're going to receive a second reply. In
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// a real network experiment here we'll do other activities, e.g., contacting
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// the test helper or fetching a webpage.
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var additional []model.DNSResponse
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for {
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additional = rch.TryNextResponses()
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if len(additional) > 0 {
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if len(additional) != 1 {
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t.Fatal("expected exactly one additional response")
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}
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break
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}
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if !delayedDNSResponseCalled {
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t.Fatal("delayedDNSResponse not called")
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}
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addrs, err = additional[0].DecodeLookupHost()
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if err != nil {
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t.Fatal(err)
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if !goodQueryType {
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t.Fatal("unexpected query type")
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}
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if diff := cmp.Diff(addrs, []string{"8.8.8.8"}); diff != "" {
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t.Fatal(diff)
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if !goodTransportNetwork {
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t.Fatal("unexpected DNS transport network")
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}
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if !goodTransportAddress {
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t.Fatal("unexpected DNS Transport address")
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}
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if !goodLookupAddrs {
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t.Fatal("unexpected delayed DNSLookup address")
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}
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if !goodError {
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t.Fatal("unexpected error encountered")
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}
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mu.Unlock()
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})
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t.Run("correct behavior when read times out", func(t *testing.T) {
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t.Run("uses a context-injected custom trace (failure case)", func(t *testing.T) {
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var (
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delayedDNSResponseCalled bool
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goodQueryType bool
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goodTransportNetwork bool
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goodTransportAddress bool
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goodLookupAddrs bool
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goodError bool
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)
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srvr := &filtering.DNSServer{
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OnQuery: func(domain string) filtering.DNSAction {
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return filtering.DNSActionTimeout
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return filtering.DNSActionLocalHostPlusCache
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},
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Cache: map[string][]string{
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// Note: the cache here is nonexistent so we should
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// get a "no such host" error from the server.
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},
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}
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listener, err := srvr.Start("127.0.0.1:0")
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@ -413,22 +403,71 @@ func TestDNSOverUDPTransport(t *testing.T) {
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}
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defer listener.Close()
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dialer := NewDialerWithoutResolver(model.DiscardLogger)
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txp := NewUnwrappedDNSOverUDPTransport(dialer, listener.LocalAddr().String())
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txp.IOTimeout = 30 * time.Millisecond // short timeout to have a fast test
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expectedAddress := listener.LocalAddr().String()
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txp := NewUnwrappedDNSOverUDPTransport(dialer, expectedAddress)
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encoder := &DNSEncoderMiekg{}
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query := encoder.Encode("dns.google.", dns.TypeA, false)
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rch, err := txp.AsyncRoundTrip(context.Background(), query, 1)
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zeroTime := time.Now()
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deterministicTime := testingx.NewTimeDeterministic(zeroTime)
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respChannel := make(chan *model.DNSResponse, 8)
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mu := new(sync.Mutex)
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tx := &mocks.Trace{
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MockTimeNow: deterministicTime.Now,
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MockOnDelayedDNSResponse: func(started time.Time, txp model.DNSTransport,
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query model.DNSQuery, response model.DNSResponse, addrs []string, err error,
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finished time.Time) error {
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mu.Lock()
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delayedDNSResponseCalled = true
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goodQueryType = (query.Type() == dns.TypeA)
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goodTransportNetwork = (txp.Network() == "udp")
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goodTransportAddress = (txp.Address() == expectedAddress)
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goodLookupAddrs = (len(addrs) == 0)
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goodError = errors.Is(err, ErrOODNSNoSuchHost)
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mu.Unlock()
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respChannel <- &response
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return errors.New("mocked") // return error to stop background routine to record responses
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},
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MockOnConnectDone: func(started time.Time, network, domain, remoteAddr string, err error,
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finished time.Time) {
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// do nothing
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},
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MockMaybeWrapNetConn: func(conn net.Conn) net.Conn {
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return conn
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},
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}
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ctx := ContextWithTrace(context.Background(), tx)
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rch, err := txp.RoundTrip(ctx, query)
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<-respChannel // wait for the delayed response
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if err != nil {
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t.Fatal(err)
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}
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defer rch.Close()
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result := <-rch.Response
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if result.Err == nil || result.Err.Error() != "generic_timeout_error" {
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t.Fatal("unexpected error", result.Err)
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addrs, err := rch.DecodeLookupHost()
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if err != nil {
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t.Fatal(err)
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}
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if result.Operation != ReadOperation {
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t.Fatal("unexpected failed operation", result.Operation)
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mu.Lock()
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if diff := cmp.Diff(addrs, []string{"127.0.0.1"}); diff != "" {
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t.Fatal(diff)
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}
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if !delayedDNSResponseCalled {
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t.Fatal("delayedDNSResponse not called")
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}
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if !goodQueryType {
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t.Fatal("unexpected query type")
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}
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if !goodTransportNetwork {
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t.Fatal("unexpected DNS transport network")
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}
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if !goodTransportAddress {
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t.Fatal("unexpected DNS Transport address")
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}
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if !goodLookupAddrs {
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t.Fatal("unexpected delayed DNSLookup address")
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}
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if !goodError {
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t.Fatal("unexpected error encountered")
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}
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mu.Unlock()
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})
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})
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