Upstream plugin prototype

upstream/tls_upstream.go

@@ -0,0 +1,47 @@
+package upstream
+
+import (
+	"crypto/tls"
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+	"time"
+)
+
+// TODO: Use persistent connection here
+
+// DnsOverTlsUpstream is the upstream implementation for plain DNS-over-TLS
+type DnsOverTlsUpstream struct {
+	endpoint      string
+	tlsServerName string
+	timeout       time.Duration
+}
+
+// NewHttpsUpstream creates a new DNS-over-TLS upstream from the endpoint address and TLS server name
+func NewDnsOverTlsUpstream(endpoint string, tlsServerName string) (Upstream, error) {
+	return &DnsOverTlsUpstream{
+		endpoint:      endpoint,
+		tlsServerName: tlsServerName,
+		timeout:       defaultTimeout,
+	}, nil
+}
+
+// Exchange provides an implementation for the Upstream interface
+func (u *DnsOverTlsUpstream) Exchange(ctx context.Context, query *dns.Msg) (*dns.Msg, error) {
+
+	dnsClient := &dns.Client{
+		Net:          "tcp-tls",
+		ReadTimeout:  u.timeout,
+		WriteTimeout: u.timeout,
+		TLSConfig:    new(tls.Config),
+	}
+	dnsClient.TLSConfig.ServerName = u.tlsServerName
+
+	resp, _, err := dnsClient.Exchange(query, u.endpoint)
+
+	if err != nil {
+		resp = &dns.Msg{}
+		resp.SetRcode(resp, dns.RcodeServerFailure)
+	}
+
+	return resp, err
+}