Import code, preparing for release

dot.go

@@ -0,0 +1,35 @@
+package ctrld
+
+import (
+	"context"
+	"crypto/tls"
+	"net"
+
+	"github.com/miekg/dns"
+)
+
+type dotResolver struct {
+	uc *UpstreamConfig
+}
+
+func (r *dotResolver) Resolve(ctx context.Context, msg *dns.Msg) (*dns.Msg, error) {
+	// The dialer is used to prevent bootstrapping cycle.
+	// If r.endpoing is set to dns.controld.dev, we need to resolve
+	// dns.controld.dev first. By using a dialer with custom resolver,
+	// we ensure that we can always resolve the bootstrap domain
+	// regardless of the machine DNS status.
+	dialer := newDialer(net.JoinHostPort(bootstrapDNS, "53"))
+	dnsClient := &dns.Client{
+		Net:    "tcp-tls",
+		Dialer: dialer,
+	}
+	endpoint := r.uc.Endpoint
+	if r.uc.BootstrapIP != "" {
+		dnsClient.TLSConfig = &tls.Config{ServerName: r.uc.Domain}
+		_, port, _ := net.SplitHostPort(endpoint)
+		endpoint = net.JoinHostPort(r.uc.BootstrapIP, port)
+	}
+
+	answer, _, err := dnsClient.ExchangeContext(ctx, msg, endpoint)
+	return answer, err
+}