dns fanout: wrap IPv6 address (#1374)

Signed-off-by: Artem Glazychev <artem.glazychev@xored.com>

Signed-off-by: Artem Glazychev <artem.glazychev@xored.com>

pkg/tools/dnsutils/fanout/handler.go

@@ -21,6 +21,7 @@ import (
 	"context"
 	"fmt"
 	"net/url"
+	"strings"
 	"time"
 
 	"github.com/miekg/dns"
@@ -55,6 +56,11 @@ func (h *fanoutHandler) ServeDNS(ctx context.Context, rw dns.ResponseWriter, msg
 				Timeout: timeout,
 			}
 
+			// If u.Host is IPv6 then wrap it in brackets
+			if strings.Count(u.Host, ":") >= 2 && !strings.HasPrefix(u.Host, "[") && !strings.Contains(u.Host, "]") {
+				u.Host = fmt.Sprintf("[%s]", u.Host)
+			}
+
 			address := u.Host
 			if u.Port() == "" {
 				address += fmt.Sprintf(":%d", h.dnsPort)