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netxlite: code quality, improve tests, docs (#494)

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See https://github.com/ooni/probe/issues/1591
This commit is contained in:
Simone Basso 2021-09-08 22:48:10 +02:00 • committed by GitHub
commit 50b58672c6
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GPG key ID: 4AEE18F83AFDEB23
15 changed files with 318 additions and 154 deletions
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33
internal/netxlite/resolver.go
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@ -27,6 +27,20 @@ type Resolver interface {
// NewResolverSystem creates a new resolver using system
// facilities for resolving domain names (e.g., getaddrinfo).
//
// The resolver will provide the following guarantees:
//
// 1. handles IDNA;
//
// 2. performs logging;
//
// 3. short-circuits IP addresses like getaddrinfo does (i.e.,
// resolving "1.1.1.1" yields []string{"1.1.1.1"};
//
// 4. wraps errors;
//
// 5. enforces reasonable timeouts (
// see https://github.com/ooni/probe/issues/1726).
func NewResolverSystem(logger Logger) Resolver {
return &resolverIDNA{
Resolver: &resolverLogger{
@ -48,7 +62,6 @@ type resolverSystem struct {
var _ Resolver = &resolverSystem{}
// LookupHost implements Resolver.LookupHost.
func (r *resolverSystem) LookupHost(ctx context.Context, hostname string) ([]string, error) {
// This code forces adding a shorter timeout to the domain name
// resolutions when using the system resolver. We have seen cases
@ -89,24 +102,18 @@ func (r *resolverSystem) lookupHost() func(ctx context.Context, domain string) (
return net.DefaultResolver.LookupHost
}
// Network implements Resolver.Network.
func (r *resolverSystem) Network() string {
return "system"
}
// Address implements Resolver.Address.
func (r *resolverSystem) Address() string {
return ""
}
// CloseIdleConnections implements Resolver.CloseIdleConnections.
func (r *resolverSystem) CloseIdleConnections() {
// nothing
// nothing to do
}
// DefaultResolver is the resolver we use by default.
var DefaultResolver = &resolverSystem{}
// resolverLogger is a resolver that emits events
type resolverLogger struct {
Resolver
@ -115,7 +122,6 @@ type resolverLogger struct {
var _ Resolver = &resolverLogger{}
// LookupHost returns the IP addresses of a host
func (r *resolverLogger) LookupHost(ctx context.Context, hostname string) ([]string, error) {
r.Logger.Debugf("resolve %s...", hostname)
start := time.Now()
@ -136,7 +142,6 @@ type resolverIDNA struct {
Resolver
}
// LookupHost implements Resolver.LookupHost.
func (r *resolverIDNA) LookupHost(ctx context.Context, hostname string) ([]string, error) {
host, err := idna.ToASCII(hostname)
if err != nil {
@ -151,7 +156,6 @@ type resolverShortCircuitIPAddr struct {
Resolver
}
// LookupHost implements Resolver.LookupHost.
func (r *resolverShortCircuitIPAddr) LookupHost(ctx context.Context, hostname string) ([]string, error) {
if net.ParseIP(hostname) != nil {
return []string{hostname}, nil
@ -166,24 +170,20 @@ var ErrNoResolver = errors.New("no configured resolver")
// domain names to IP addresses and always returns ErrNoResolver.
type nullResolver struct{}
// LookupHost implements Resolver.LookupHost.
func (r *nullResolver) LookupHost(ctx context.Context, hostname string) (addrs []string, err error) {
return nil, ErrNoResolver
}
// Network implements Resolver.Network.
func (r *nullResolver) Network() string {
return "null"
}
// Address implements Resolver.Address.
func (r *nullResolver) Address() string {
return ""
}
// CloseIdleConnections implements Resolver.CloseIdleConnections.
func (r *nullResolver) CloseIdleConnections() {
// nothing
// nothing to do
}
// resolverErrWrapper is a Resolver that knows about wrapping errors.
@ -193,7 +193,6 @@ type resolverErrWrapper struct {
var _ Resolver = &resolverErrWrapper{}
// LookupHost implements Resolver.LookupHost
func (r *resolverErrWrapper) LookupHost(ctx context.Context, hostname string) ([]string, error) {
addrs, err := r.Resolver.LookupHost(ctx, hostname)
if err != nil {