package tunneldns import ( "github.com/coredns/coredns/plugin" "github.com/miekg/dns" "github.com/pkg/errors" "golang.org/x/net/context" ) // Upstream is a simplified interface for proxy destination type Upstream interface { Exchange(ctx context.Context, query *dns.Msg) (*dns.Msg, error) } // ProxyPlugin is a simplified DNS proxy using a generic upstream interface type ProxyPlugin struct { Upstreams []Upstream Next plugin.Handler } // ServeDNS implements interface for CoreDNS plugin func (p ProxyPlugin) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) { var reply *dns.Msg var backendErr error for _, upstream := range p.Upstreams { reply, backendErr = upstream.Exchange(ctx, r) if backendErr == nil { w.WriteMsg(reply) return 0, nil } } return dns.RcodeServerFailure, errors.Wrap(backendErr, "failed to contact any of the upstreams") } // Name implements interface for CoreDNS plugin func (p ProxyPlugin) Name() string { return "proxy" }