fix: ensure ipv4 is present for app deploys

See coop-cloud/organising#227.

pkg/dns/common.go

@@ -1,8 +1,11 @@
 package dns
 
 import (
+	"context"
 	"fmt"
+	"net"
 	"os"
+	"time"
 
 	"github.com/AlecAivazis/survey/v2"
 	"github.com/sirupsen/logrus"
@@ -26,3 +29,38 @@ func NewToken(provider, providerTokenEnvVar string) (string, error) {
 
 	return token, nil
 }
+
+// EnsureIPv4 ensures that an ipv4 address is set for a domain name
+func EnsureIPv4(domainName string) (string, error) {
+	var ipv4 string
+
+	// comrade librehosters DNS resolver -> https://www.privacy-handbuch.de/handbuch_93d.htm
+	freifunkDNS := "5.1.66.255:53"
+
+	resolver := &net.Resolver{
+		PreferGo: false,
+		Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
+			d := net.Dialer{
+				Timeout: time.Millisecond * time.Duration(10000),
+			}
+			return d.DialContext(ctx, "udp", freifunkDNS)
+		},
+	}
+
+	logrus.Debugf("created DNS resolver via '%s'", freifunkDNS)
+
+	ctx := context.Background()
+	ips, err := resolver.LookupIPAddr(ctx, domainName)
+	if err != nil {
+		return ipv4, err
+	}
+
+	if len(ips) == 0 {
+		return ipv4, fmt.Errorf("unable to retrieve ipv4 address for %s", domainName)
+	}
+
+	ipv4 = ips[0].IP.To4().String()
+	logrus.Debugf("discovered the following ipv4 addr: %s", ipv4)
+
+	return ipv4, nil
+}