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refactor: DNSTransport I/Os DNS messages (#760)

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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
This commit is contained in:
Simone Basso 2022-05-25 17:03:58 +02:00 • committed by GitHub
commit 01a513a496
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35 changed files with 1694 additions and 1039 deletions
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35
internal/netxlite/dnsoverhttps.go
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@ -8,6 +8,7 @@ import (
"bytes"
"context"
"errors"
"io"
"net/http"
"time"
@ -19,6 +20,9 @@ type DNSOverHTTPSTransport struct {
// Client is the MANDATORY http client to use.
Client model.HTTPClient
// Decoder is the MANDATORY DNSDecoder.
Decoder model.DNSDecoder
// URL is the MANDATORY URL of the DNS-over-HTTPS server.
URL string
@ -31,9 +35,9 @@ type DNSOverHTTPSTransport struct {
//
// Arguments:
//
// - client in http.Client-like type (e.g., http.DefaultClient);
// - client is a model.HTTPClient type;
//
// - URL is the DoH resolver URL (e.g., https://1.1.1.1/dns-query).
// - URL is the DoH resolver URL (e.g., https://dns.google/dns-query).
func NewDNSOverHTTPSTransport(client model.HTTPClient, URL string) *DNSOverHTTPSTransport {
return NewDNSOverHTTPSTransportWithHostOverride(client, URL, "")
}
@ -42,22 +46,31 @@ func NewDNSOverHTTPSTransport(client model.HTTPClient, URL string) *DNSOverHTTPS
// with the given Host header override.
func NewDNSOverHTTPSTransportWithHostOverride(
client model.HTTPClient, URL, hostOverride string) *DNSOverHTTPSTransport {
return &DNSOverHTTPSTransport{Client: client, URL: URL, HostOverride: hostOverride}
return &DNSOverHTTPSTransport{
Client: client,
Decoder: &DNSDecoderMiekg{},
URL: URL,
HostOverride: hostOverride,
}
}
// RoundTrip sends a query and receives a reply.
func (t *DNSOverHTTPSTransport) RoundTrip(ctx context.Context, query []byte) ([]byte, error) {
func (t *DNSOverHTTPSTransport) RoundTrip(
ctx context.Context, query model.DNSQuery) (model.DNSResponse, error) {
rawQuery, err := query.Bytes()
if err != nil {
return nil, err
}
ctx, cancel := context.WithTimeout(ctx, 45*time.Second)
defer cancel()
req, err := http.NewRequest("POST", t.URL, bytes.NewReader(query))
req, err := http.NewRequest("POST", t.URL, bytes.NewReader(rawQuery))
if err != nil {
return nil, err
}
req.Host = t.HostOverride
req.Header.Set("user-agent", model.HTTPHeaderUserAgent)
req.Header.Set("content-type", "application/dns-message")
var resp *http.Response
resp, err = t.Client.Do(req.WithContext(ctx))
resp, err := t.Client.Do(req.WithContext(ctx))
if err != nil {
return nil, err
}
@ -70,7 +83,13 @@ func (t *DNSOverHTTPSTransport) RoundTrip(ctx context.Context, query []byte) ([]
if resp.Header.Get("content-type") != "application/dns-message" {
return nil, errors.New("doh: invalid content-type")
}
return ReadAllContext(ctx, resp.Body)
const maxresponsesize = 1 << 20
limitReader := io.LimitReader(resp.Body, maxresponsesize)
rawResponse, err := ReadAllContext(ctx, limitReader)
if err != nil {
return nil, err
}
return t.Decoder.DecodeResponse(rawResponse, query)
}
// RequiresPadding returns true for DoH according to RFC8467.