ooni-probe-cli/internal/netxlite/dnsovergetaddrinfo.go
Simone Basso 86ffd6a0c4
feat: reintroduce the tproxy functionality (#975)
We originally removed the TProxy in https://github.com/ooni/probe/issues/2224. Nevertheless, in https://github.com/ooni/probe-cli/pull/969, we determined that something like the previous TProxy, with small changes, was required to support https://github.com/ooni/probe/issues/2340. So, this pull request reintroduces a slightly-modified TProxy functionality that better adapts to the `--remote=REMOTE` use case.
2022-10-12 17:38:33 +02:00

160 lines
3.9 KiB
Go

package netxlite
//
// DNS over getaddrinfo: fake transport to allow us to observe
// lookups using getaddrinfo as a DNSTransport.
//
import (
"context"
"net"
"time"
"github.com/miekg/dns"
"github.com/ooni/probe-cli/v3/internal/model"
"github.com/ooni/probe-cli/v3/internal/runtimex"
)
// dnsOverGetaddrinfoTransport is a DNSTransport using getaddrinfo.
type dnsOverGetaddrinfoTransport struct {
// (OPTIONAL) allows to run tests with a short timeout
testableTimeout time.Duration
// (OPTIONAL) allows to mock the underlying getaddrinfo call
testableLookupANY func(ctx context.Context, domain string) ([]string, string, error)
}
// NewDNSOverGetaddrinfoTransport creates a new dns-over-getaddrinfo transport.
func NewDNSOverGetaddrinfoTransport() model.DNSTransport {
return &dnsOverGetaddrinfoTransport{}
}
var _ model.DNSTransport = &dnsOverGetaddrinfoTransport{}
func (txp *dnsOverGetaddrinfoTransport) RoundTrip(
ctx context.Context, query model.DNSQuery) (model.DNSResponse, error) {
if query.Type() != dns.TypeANY {
return nil, ErrNoDNSTransport
}
addrs, cname, err := txp.lookup(ctx, query.Domain())
if err != nil {
return nil, err
}
resp := &dnsOverGetaddrinfoResponse{
addrs: addrs,
cname: cname,
query: query,
}
return resp, nil
}
type dnsOverGetaddrinfoResponse struct {
addrs []string
cname string
query model.DNSQuery
}
// Used to move addrs and cname out of the worker goroutine
type dnsOverGetaddrinfoAddrsAndCNAME struct {
// List of resolved addresses (it's a bug if this is empty)
addrs []string
// Resolved CNAME or empty string
cname string
}
func (txp *dnsOverGetaddrinfoTransport) lookup(
ctx context.Context, hostname string) ([]string, string, error) {
// This code forces adding a shorter timeout to the domain name
// resolutions when using the system resolver. We have seen cases
// in which such a timeout becomes too large. One such case is
// described in https://github.com/ooni/probe/issues/1726.
outch, errch := make(chan *dnsOverGetaddrinfoAddrsAndCNAME, 1), make(chan error, 1)
ctx, cancel := context.WithTimeout(ctx, txp.timeout())
defer cancel()
go func() {
addrs, cname, err := txp.lookupfn()(ctx, hostname)
if err != nil {
errch <- err
return
}
outch <- &dnsOverGetaddrinfoAddrsAndCNAME{
addrs: addrs,
cname: cname,
}
}()
select {
case <-ctx.Done():
return nil, "", ctx.Err()
case p := <-outch:
return p.addrs, p.cname, nil
case err := <-errch:
return nil, "", err
}
}
func (txp *dnsOverGetaddrinfoTransport) timeout() time.Duration {
if txp.testableTimeout > 0 {
return txp.testableTimeout
}
return 15 * time.Second
}
func (txp *dnsOverGetaddrinfoTransport) lookupfn() func(ctx context.Context, domain string) ([]string, string, error) {
if txp.testableLookupANY != nil {
return txp.testableLookupANY
}
return TProxy.GetaddrinfoLookupANY
}
func (txp *dnsOverGetaddrinfoTransport) RequiresPadding() bool {
return false
}
func (txp *dnsOverGetaddrinfoTransport) Network() string {
return TProxy.GetaddrinfoResolverNetwork()
}
func (txp *dnsOverGetaddrinfoTransport) Address() string {
return ""
}
func (txp *dnsOverGetaddrinfoTransport) CloseIdleConnections() {
// nothing
}
func (r *dnsOverGetaddrinfoResponse) Query() model.DNSQuery {
runtimex.PanicIfNil(r.query, "dnsOverGetaddrinfoResponse with nil query")
return r.query
}
func (r *dnsOverGetaddrinfoResponse) Bytes() []byte {
return nil
}
func (r *dnsOverGetaddrinfoResponse) Rcode() int {
return 0
}
func (r *dnsOverGetaddrinfoResponse) DecodeHTTPS() (*model.HTTPSSvc, error) {
return nil, ErrNoDNSTransport
}
func (r *dnsOverGetaddrinfoResponse) DecodeLookupHost() ([]string, error) {
if len(r.addrs) <= 0 {
return nil, ErrOODNSNoAnswer
}
return r.addrs, nil
}
func (r *dnsOverGetaddrinfoResponse) DecodeNS() ([]*net.NS, error) {
return nil, ErrNoDNSTransport
}
func (r *dnsOverGetaddrinfoResponse) DecodeCNAME() (string, error) {
if r.cname == "" {
return "", ErrOODNSNoAnswer
}
return r.cname, nil
}