Add support for IDNA

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

prober/dns.go

@@ -253,11 +253,13 @@ func ProbeDNS(ctx context.Context, target string, module config.Module, registry
 		}
 	}
 
+	queryName := internationalizeDNSDomain(logger, module.DNS.QueryName)
+
 	msg := new(dns.Msg)
 	msg.Id = dns.Id()
 	msg.RecursionDesired = module.DNS.Recursion
 	msg.Question = make([]dns.Question, 1)
-	msg.Question[0] = dns.Question{dns.Fqdn(module.DNS.QueryName), qt, qc}
+	msg.Question[0] = dns.Question{dns.Fqdn(queryName), qt, qc}
 
 	level.Info(logger).Log("msg", "Making DNS query", "target", targetIP, "dial_protocol", dialProtocol, "query", module.DNS.QueryName, "type", qt, "class", qc)
 	timeoutDeadline, _ := ctx.Deadline()

prober/utils.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/go-kit/log"
 	"github.com/go-kit/log/level"
+	"golang.org/x/net/idna"
 
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -60,6 +61,7 @@ func chooseProtocol(ctx context.Context, IPProtocol string, fallbackIPProtocol b
 		fallbackProtocol = "ip6"
 	}
 
+	target = internationalizeDNSDomain(logger, target)
 	level.Info(logger).Log("msg", "Resolving target address", "target", target, "ip_protocol", IPProtocol)
 	resolveStart := time.Now()
 
@@ -142,3 +144,18 @@ func ipHash(ip net.IP) float64 {
 	}
 	return float64(h.Sum32())
 }
+
+func internationalizeDNSDomain(logger log.Logger, domain string) string {
+	if net.ParseIP(domain) != nil {
+		// IP addresses don't need to be internationalized.
+		return domain
+	}
+	idnaDomain, err := idna.Lookup.ToASCII(domain)
+	if err != nil {
+		return domain
+	}
+	if idnaDomain != domain {
+		level.Info(logger).Log("msg", "Domain internationalized", "unicode", domain, "ascii", idnaDomain)
+	}
+	return idnaDomain
+}

prober/utils_test.go

@@ -252,3 +252,23 @@ func checkMetrics(expected map[string]map[string]map[string]struct{}, mfs []*dto
 		}
 	}
 }
+
+func TestChooseProtocolIDNA(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping network dependent test")
+	}
+	var (
+		ctx      = context.Background()
+		registry = prometheus.NewPedanticRegistry()
+		w        = log.NewSyncWriter(os.Stderr)
+		logger   = log.NewLogfmtLogger(w)
+	)
+
+	ip, _, err := chooseProtocol(ctx, "ip4", true, "www.académie-française.fr", registry, logger)
+	if err != nil {
+		t.Error(err)
+	}
+	if ip == nil || ip.IP.To4() == nil {
+		t.Error("it should answer")
+	}
+}