74 lines
2.1 KiB
Go
74 lines
2.1 KiB
Go
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package dialer
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import (
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"context"
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"errors"
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"net"
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"strings"
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"github.com/ooni/probe-cli/v3/internal/engine/legacy/netx/dialid"
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"github.com/ooni/probe-cli/v3/internal/engine/netx/errorx"
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)
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// DNSDialer is a dialer that uses the configured Resolver to resolver a
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// domain name to IP addresses, and the configured Dialer to connect.
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type DNSDialer struct {
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Dialer
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Resolver Resolver
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}
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// DialContext implements Dialer.DialContext.
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func (d DNSDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
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onlyhost, onlyport, err := net.SplitHostPort(address)
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if err != nil {
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return nil, err
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}
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ctx = dialid.WithDialID(ctx) // important to create before lookupHost
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var addrs []string
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addrs, err = d.LookupHost(ctx, onlyhost)
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if err != nil {
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return nil, err
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}
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var errorslist []error
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for _, addr := range addrs {
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target := net.JoinHostPort(addr, onlyport)
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conn, err := d.Dialer.DialContext(ctx, network, target)
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if err == nil {
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return conn, nil
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}
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errorslist = append(errorslist, err)
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}
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return nil, ReduceErrors(errorslist)
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}
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// ReduceErrors finds a known error in a list of errors since it's probably most relevant
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func ReduceErrors(errorslist []error) error {
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if len(errorslist) == 0 {
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return nil
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}
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// If we have a known error, let's consider this the real error
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// since it's probably most relevant. Otherwise let's return the
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// first considering that (1) local resolvers likely will give
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// us IPv4 first and (2) also our resolver does that. So, in case
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// the user has no IPv6 connectivity, an IPv6 error is going to
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// appear later in the list of errors.
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for _, err := range errorslist {
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var wrapper *errorx.ErrWrapper
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if errors.As(err, &wrapper) && !strings.HasPrefix(
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err.Error(), "unknown_failure",
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) {
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return err
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}
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}
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// TODO(bassosimone): handle this case in a better way
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return errorslist[0]
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}
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// LookupHost implements Resolver.LookupHost
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func (d DNSDialer) LookupHost(ctx context.Context, hostname string) ([]string, error) {
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if net.ParseIP(hostname) != nil {
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return []string{hostname}, nil
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}
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return d.Resolver.LookupHost(ctx, hostname)
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}
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