01a513a496
This diff refactors the DNSTransport model to receive in input a DNSQuery and return in output a DNSResponse. The design of DNSQuery and DNSResponse takes into account the use case of a transport using getaddrinfo, meaning that we don't need to serialize and deserialize messages when using getaddrinfo. The current codebase does not use a getaddrinfo transport, but I wrote one such a transport in the Websteps Winter 2021 prototype (https://github.com/bassosimone/websteps-illustrated/). The design conversation that lead to producing this diff is https://github.com/ooni/probe/issues/2099
86 lines
2.1 KiB
Go
86 lines
2.1 KiB
Go
package netxlite
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//
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// DNS-over-UDP transport
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//
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import (
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"context"
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"time"
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"github.com/ooni/probe-cli/v3/internal/model"
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)
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// DNSOverUDPTransport is a DNS-over-UDP DNSTransport.
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type DNSOverUDPTransport struct {
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dialer model.Dialer
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decoder model.DNSDecoder
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address string
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}
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// NewDNSOverUDPTransport creates a DNSOverUDPTransport instance.
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//
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// Arguments:
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//
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// - dialer is any type that implements the Dialer interface;
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//
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// - address is the endpoint address (e.g., 8.8.8.8:53).
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func NewDNSOverUDPTransport(dialer model.Dialer, address string) *DNSOverUDPTransport {
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return &DNSOverUDPTransport{
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dialer: dialer,
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decoder: &DNSDecoderMiekg{},
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address: address,
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}
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}
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// RoundTrip sends a query and receives a reply.
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func (t *DNSOverUDPTransport) RoundTrip(
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ctx context.Context, query model.DNSQuery) (model.DNSResponse, error) {
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rawQuery, err := query.Bytes()
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if err != nil {
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return nil, err
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}
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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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const iotimeout = 5 * time.Second
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conn.SetDeadline(time.Now().Add(iotimeout))
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if _, err = conn.Write(rawQuery); err != nil {
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return nil, err
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}
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const maxmessagesize = 1 << 17
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rawResponse := make([]byte, maxmessagesize)
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count, err := conn.Read(rawResponse)
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if err != nil {
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return nil, err
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}
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rawResponse = rawResponse[:count]
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return t.decoder.DecodeResponse(rawResponse, query)
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}
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// RequiresPadding returns false for UDP according to RFC8467.
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func (t *DNSOverUDPTransport) RequiresPadding() bool {
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return false
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}
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// Network returns the transport network, i.e., "udp".
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func (t *DNSOverUDPTransport) 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 *DNSOverUDPTransport) Address() string {
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return t.address
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}
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// CloseIdleConnections closes idle connections, if any.
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func (t *DNSOverUDPTransport) CloseIdleConnections() {
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// nothing to do
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}
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var _ model.DNSTransport = &DNSOverUDPTransport{}
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