add: dns.go

dns.go

@@ -0,0 +1,43 @@
+package warc
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/miekg/dns"
+)
+
+func (d *customDialer) resolveDNS(address string) (net.IP, error) {
+	m := new(dns.Msg)
+	m.SetQuestion(dns.Fqdn(address), dns.TypeA)
+
+	r, _, err := d.DNSClient.Exchange(m, d.DNSServer)
+	if err != nil {
+		return nil, err
+	}
+
+	// Print raw DNS output
+	// fmt.Printf("Raw DNS response for %s:\n%s\n", address, r.String())
+
+	var ipv4, ipv6 net.IP
+
+	for _, answer := range r.Answer {
+		if a, ok := answer.(*dns.A); ok && !d.disableIPv4 {
+			ipv4 = a.A
+		} else if aaaa, ok := answer.(*dns.AAAA); ok && !d.disableIPv6 {
+			ipv6 = aaaa.AAAA
+			break // Prioritize IPv6 if available
+		}
+	}
+
+	// Prioritize IPv6 if both are available and enabled
+	if ipv6 != nil {
+		return ipv6, nil
+	}
+
+	if ipv4 != nil {
+		return ipv4, nil
+	}
+
+	return nil, fmt.Errorf("no suitable IP address found for %s", address)
+}