24b230fd38
This diff attempts to modify the errors reported by our custom resolver by matching more strings from the stdlib. Part of https://github.com/ooni/probe/issues/1733 and diff has been extracted from https://github.com/ooni/probe-cli/pull/506.
104 lines
3.0 KiB
Go
104 lines
3.0 KiB
Go
package dnsx
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import (
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"context"
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"errors"
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"net"
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"github.com/miekg/dns"
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"github.com/ooni/probe-cli/v3/internal/atomicx"
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)
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// SerialResolver is a resolver that first issues an A query and then
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// issues an AAAA query for the requested domain.
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type SerialResolver struct {
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Encoder Encoder
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Decoder Decoder
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NumTimeouts *atomicx.Int64
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Txp RoundTripper
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}
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// NewSerialResolver creates a new OONI Resolver instance.
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func NewSerialResolver(t RoundTripper) *SerialResolver {
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return &SerialResolver{
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Encoder: &MiekgEncoder{},
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Decoder: &MiekgDecoder{},
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NumTimeouts: &atomicx.Int64{},
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Txp: t,
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}
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}
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// Transport returns the transport being used.
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func (r *SerialResolver) Transport() RoundTripper {
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return r.Txp
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}
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// Network implements Resolver.Network
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func (r *SerialResolver) Network() string {
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return r.Txp.Network()
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}
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// Address implements Resolver.Address
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func (r *SerialResolver) Address() string {
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return r.Txp.Address()
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}
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// CloseIdleConnections closes idle connections.
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func (r *SerialResolver) CloseIdleConnections() {
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r.Txp.CloseIdleConnections()
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}
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// LookupHost implements Resolver.LookupHost.
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func (r *SerialResolver) LookupHost(ctx context.Context, hostname string) ([]string, error) {
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var addrs []string
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addrsA, errA := r.lookupHostWithRetry(ctx, hostname, dns.TypeA)
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addrsAAAA, errAAAA := r.lookupHostWithRetry(ctx, hostname, dns.TypeAAAA)
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if errA != nil && errAAAA != nil {
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return nil, errA
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}
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addrs = append(addrs, addrsA...)
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addrs = append(addrs, addrsAAAA...)
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return addrs, nil
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}
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func (r *SerialResolver) lookupHostWithRetry(
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ctx context.Context, hostname string, qtype uint16) ([]string, error) {
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var errorslist []error
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for i := 0; i < 3; i++ {
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replies, err := r.lookupHostWithoutRetry(ctx, hostname, qtype)
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if err == nil {
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return replies, nil
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}
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errorslist = append(errorslist, err)
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var operr *net.OpError
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if !errors.As(err, &operr) || !operr.Timeout() {
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// The first error is the one that is most likely to be caused
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// by the network. Subsequent errors are more likely to be caused
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// by context deadlines. So, the first error is attached to an
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// operation, while subsequent errors may possibly not be. If
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// so, the resulting failing operation is not correct.
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break
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}
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r.NumTimeouts.Add(1)
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}
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// bugfix: we MUST return one of the errors otherwise we confuse the
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// mechanism in errwrap that classifies the root cause operation, since
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// it would not be able to find a child with a major operation error
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return nil, errorslist[0]
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}
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// lookupHostWithoutRetry issues a lookup host query for the specified
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// qtype (dns.A or dns.AAAA) without retrying on failure.
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func (r *SerialResolver) lookupHostWithoutRetry(
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ctx context.Context, hostname string, qtype uint16) ([]string, error) {
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querydata, err := r.Encoder.Encode(hostname, qtype, r.Txp.RequiresPadding())
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if err != nil {
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return nil, err
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}
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replydata, err := r.Txp.RoundTrip(ctx, querydata)
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if err != nil {
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return nil, err
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}
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return r.Decoder.DecodeLookupHost(qtype, replydata)
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}
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