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feat(dnsovergetaddrinfo): collect the CNAME (#876)

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* feat(dnsovergetaddrinfo): collect the CNAME

This diff modifies how dnsovergetaddrinfo.go works such that the
returned DNSResponse includes the CNAME.

Closes https://github.com/ooni/probe/issues/2226.

While there, recognize that we can remove getaddrinfoLookupHost and
always call getaddrinfoLookupANY everywhere. (This simplification is
why we did https://github.com/ooni/probe-cli/pull/874.)

* fix: extra debugging because of failing CI

Everything is OK locally (on macOS). However, maybe things are a bit
different on GNU/Linux perhaps?

Here's the error:

```
--- FAIL: TestPass (0.11s)
    resolver_test.go:113: unexpected rcode
FAIL
coverage: 95.7% of statements
FAIL	github.com/ooni/probe-cli/v3/internal/cmd/jafar/resolver	0.242s
```

I'm a bit confused because jafar's resolver is _unrelated_. But actually this
error never occurred again after a committed the debugging diff.
This commit is contained in:
Simone Basso 2022-08-23 13:53:08 +02:00 • committed by GitHub
commit 080abf90d9
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GPG key ID: 4AEE18F83AFDEB23
6 changed files with 49 additions and 46 deletions
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47
internal/netxlite/dnsovergetaddrinfo.go
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@ -17,8 +17,11 @@ import (
// dnsOverGetaddrinfoTransport is a DNSTransport using getaddrinfo.
type dnsOverGetaddrinfoTransport struct {
testableTimeout time.Duration
testableLookupHost func(ctx context.Context, domain string) ([]string, error)
// (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)
}
var _ model.DNSTransport = &dnsOverGetaddrinfoTransport{}
@ -28,13 +31,13 @@ func (txp *dnsOverGetaddrinfoTransport) RoundTrip(
if query.Type() != dns.TypeANY {
return nil, ErrNoDNSTransport
}
addrs, err := txp.lookup(ctx, query.Domain())
addrs, cname, err := txp.lookup(ctx, query.Domain())
if err != nil {
return nil, err
}
resp := &dnsOverGetaddrinfoResponse{
addrs: addrs,
cname: "", // TODO: implement this functionality
cname: cname,
query: query,
}
return resp, nil
@ -46,30 +49,42 @@ type dnsOverGetaddrinfoResponse struct {
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, error) {
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.
addrsch, errch := make(chan []string, 1), make(chan error, 1)
outch, errch := make(chan *dnsOverGetaddrinfoAddrsAndCNAME, 1), make(chan error, 1)
ctx, cancel := context.WithTimeout(ctx, txp.timeout())
defer cancel()
go func() {
addrs, err := txp.lookupfn()(ctx, hostname)
addrs, cname, err := txp.lookupfn()(ctx, hostname)
if err != nil {
errch <- err
return
}
addrsch <- addrs
outch <- &dnsOverGetaddrinfoAddrsAndCNAME{
addrs: addrs,
cname: cname,
}
}()
select {
case <-ctx.Done():
return nil, ctx.Err()
case addrs := <-addrsch:
return addrs, nil
return nil, "", ctx.Err()
case p := <-outch:
return p.addrs, p.cname, nil
case err := <-errch:
return nil, err
return nil, "", err
}
}
@ -80,11 +95,11 @@ func (txp *dnsOverGetaddrinfoTransport) timeout() time.Duration {
return 15 * time.Second
}
func (txp *dnsOverGetaddrinfoTransport) lookupfn() func(ctx context.Context, domain string) ([]string, error) {
if txp.testableLookupHost != nil {
return txp.testableLookupHost
func (txp *dnsOverGetaddrinfoTransport) lookupfn() func(ctx context.Context, domain string) ([]string, string, error) {
if txp.testableLookupANY != nil {
return txp.testableLookupANY
}
return getaddrinfoLookupHost
return getaddrinfoLookupANY
}
func (txp *dnsOverGetaddrinfoTransport) RequiresPadding() bool {