add proxy protocol support

Signed-off-by: Adphi <philippe.adrien.nousse@gmail.com>

go.mod

@@ -22,6 +22,7 @@ require (
 	github.com/justinas/alice v1.2.0
 	github.com/miekg/dns v1.1.41
 	github.com/opentracing/opentracing-go v1.1.0
+	github.com/pires/go-proxyproto v0.7.0
 	github.com/planetscale/vtprotobuf v0.4.0
 	github.com/prometheus/client_golang v1.14.0
 	github.com/rs/cors v1.7.0

go.sum

@@ -546,6 +546,8 @@ github.com/pierrec/lz4 v1.0.2-0.20190131084431-473cd7ce01a1/go.mod h1:3/3N9NVKO0
 github.com/pierrec/lz4 v2.0.5+incompatible/go.mod h1:pdkljMzZIN41W+lC3N2tnIh5sFi+IEE17M5jbnwPHcY=
 github.com/pingcap/errors v0.11.4 h1:lFuQV/oaUMGcD2tqt+01ROSmJs75VG1ToEOkZIZ4nE4=
 github.com/pingcap/errors v0.11.4/go.mod h1:Oi8TUi2kEtXXLMJk9l1cGmz20kV3TaQ0usTwv5KuLY8=
+github.com/pires/go-proxyproto v0.7.0 h1:IukmRewDQFWC7kfnb66CSomk2q/seBuilHBYFwyq0Hs=
+github.com/pires/go-proxyproto v0.7.0/go.mod h1:Vz/1JPY/OACxWGQNIRY2BeyDmpoaWmEP40O9LbuiFR4=
 github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=

service/options.go

@@ -67,6 +67,9 @@ type Options interface {
 
 	// TODO(adphi): metrics + tracing
 
+	WithoutCmux() bool
+	ProxyProtocol() bool
+
 	Default()
 }
 
@@ -341,6 +344,13 @@ func WithoutCmux() Option {
 	}
 }
 
+func WithProxyProtocol(addrs ...string) Option {
+	return func(o *options) {
+		o.proxyProtocol = true
+		o.proxyProtocolAddrs = addrs
+	}
+}
+
 type options struct {
 	ctx     context.Context
 	name    string
@@ -389,6 +399,8 @@ type options struct {
 	error              error
 	gatewayPrefix      string
 	withoutCmux        bool
+	proxyProtocol      bool
+	proxyProtocolAddrs []string
 }
 
 func (o *options) Name() string {
@@ -511,6 +523,10 @@ func (o *options) WithoutCmux() bool {
 	return o.withoutCmux
 }
 
+func (o *options) ProxyProtocol() bool {
+	return o.proxyProtocol
+}
+
 func (o *options) parseTLSConfig() error {
 	if o.tlsConfig != nil {
 		return nil

service/service.go

@@ -18,6 +18,7 @@ import (
 	"github.com/google/uuid"
 	grpcmiddleware "github.com/grpc-ecosystem/go-grpc-middleware"
 	"github.com/justinas/alice"
+	"github.com/pires/go-proxyproto"
 	"github.com/rs/cors"
 	"github.com/soheilhy/cmux"
 	"go.uber.org/multierr"
@@ -172,6 +173,34 @@ func (s *service) start() (*errgroup.Group, error) {
 		s.opts.address = s.opts.lis.Addr().String()
 	}
 
+	if s.opts.proxyProtocol {
+		p := func(upstream net.Addr) (proxyproto.Policy, error) {
+			u, _, err := net.SplitHostPort(upstream.String())
+			if err != nil {
+				return proxyproto.REJECT, err
+			}
+			ip := net.ParseIP(u)
+			if ip == nil {
+				return proxyproto.REJECT, fmt.Errorf("proxyproto: invalid IP address")
+			}
+			if ip.IsPrivate() || ip.IsLoopback() {
+				return proxyproto.USE, nil
+			}
+			return proxyproto.REJECT, nil
+		}
+		if len(s.opts.proxyProtocolAddrs) > 0 {
+			var err error
+			p, err = proxyproto.StrictWhiteListPolicy(s.opts.proxyProtocolAddrs)
+			if err != nil {
+				return nil, err
+			}
+		}
+		s.opts.lis = &proxyproto.Listener{
+			Listener: s.opts.lis,
+			Policy:   p,
+		}
+	}
+
 	for i := range s.opts.beforeStart {
 		if err := s.opts.beforeStart[i](); err != nil {
 			return nil, err