6d3a4f1db8
When preparing a tutorial for netxlite, I figured it is easier to tell people "hey, this is the package you should use for all low-level networking stuff" rather than introducing people to a set of packages working together where some piece of functionality is here and some other piece is there. Part of https://github.com/ooni/probe/issues/1591
64 lines
1.5 KiB
Go
64 lines
1.5 KiB
Go
package netxlite
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import (
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"context"
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"time"
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)
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// DNSOverUDP is a DNS over UDP RoundTripper.
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type DNSOverUDP struct {
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dialer Dialer
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address string
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}
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// NewDNSOverUDP creates a DNSOverUDP instance.
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func NewDNSOverUDP(dialer Dialer, address string) *DNSOverUDP {
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return &DNSOverUDP{dialer: dialer, address: address}
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}
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// RoundTrip implements RoundTripper.RoundTrip.
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func (t *DNSOverUDP) RoundTrip(ctx context.Context, query []byte) ([]byte, error) {
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conn, err := t.dialer.DialContext(ctx, "udp", t.address)
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if err != nil {
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return nil, err
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}
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defer conn.Close()
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// Use five seconds timeout like Bionic does. See
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// https://labs.ripe.net/Members/baptiste_jonglez_1/persistent-dns-connections-for-reliability-and-performance
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if err = conn.SetDeadline(time.Now().Add(5 * time.Second)); err != nil {
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return nil, err
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}
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if _, err = conn.Write(query); err != nil {
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return nil, err
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}
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reply := make([]byte, 1<<17)
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var n int
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n, err = conn.Read(reply)
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if err != nil {
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return nil, err
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}
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return reply[:n], nil
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}
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// RequiresPadding returns false for UDP according to RFC8467
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func (t *DNSOverUDP) RequiresPadding() bool {
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return false
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}
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// Network returns the transport network (e.g., doh, dot)
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func (t *DNSOverUDP) Network() string {
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return "udp"
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}
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// Address returns the upstream server address.
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func (t *DNSOverUDP) Address() string {
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return t.address
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}
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// CloseIdleConnections closes idle connections.
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func (t *DNSOverUDP) CloseIdleConnections() {
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// nothing to do
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}
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var _ DNSTransport = &DNSOverUDP{}
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