Upstream plugin prototype

upstream/dns_upstream.go

@@ -0,0 +1,36 @@
+package upstream
+
+import (
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+	"time"
+)
+
+// DnsUpstream is a very simple upstream implementation for plain DNS
+type DnsUpstream struct {
+	nameServer string        // IP:port
+	timeout    time.Duration // Max read and write timeout
+}
+
+// NewDnsUpstream creates a new plain-DNS upstream
+func NewDnsUpstream(nameServer string) (Upstream, error) {
+	return &DnsUpstream{nameServer: nameServer, timeout: defaultTimeout}, nil
+}
+
+// Exchange provides an implementation for the Upstream interface
+func (u *DnsUpstream) Exchange(ctx context.Context, query *dns.Msg) (*dns.Msg, error) {
+
+	dnsClient := &dns.Client{
+		ReadTimeout:  u.timeout,
+		WriteTimeout: u.timeout,
+	}
+
+	resp, _, err := dnsClient.Exchange(query, u.nameServer)
+
+	if err != nil {
+		resp = &dns.Msg{}
+		resp.SetRcode(resp, dns.RcodeServerFailure)
+	}
+
+	return resp, err
+}