feat: implement PROXY protocol to propagate source IPs (#22)

Fixes #13 

Co-authored-by: Geoff Bourne <itzgeoff@gmail.com>

README.md

@@ -1,3 +1,4 @@
+[![Discord](https://img.shields.io/discord/660567679458869252?label=discord)](https://discord.gg/chXNHhFJmd)
 [![GitHub issues](https://img.shields.io/github/issues/itzg/mc-router.svg)](https://github.com/itzg/mc-router/issues)
 [![Docker Pulls](https://img.shields.io/docker/pulls/itzg/mc-router.svg)](https://cloud.docker.com/u/itzg/repository/docker/itzg/mc-router)
 [![GitHub release](https://img.shields.io/github/release/itzg/mc-router.svg)](https://github.com/itzg/mc-router/releases)

cmd/mc-router/main.go

@@ -40,6 +40,7 @@ type Config struct {
 	InKubeCluster        bool     `usage:"Use in-cluster kubernetes config"`
 	KubeConfig           string   `usage:"The path to a kubernetes configuration file"`
 	MetricsBackend       string   `default:"discard" usage:"Backend to use for metrics exposure/publishing: discard,expvar,influxdb"`
+	UseProxyProtocol    bool     `default:"false" usage:"Send PROXY protocol to backend servers"`
 	MetricsBackendConfig MetricsBackendConfig
 }
 
@@ -98,7 +99,7 @@ func main() {
 	if config.ConnectionRateLimit < 1 {
 		config.ConnectionRateLimit = 1
 	}
-	connector := server.NewConnector(metricsBuilder.BuildConnectorMetrics())
+	connector := server.NewConnector(metricsBuilder.BuildConnectorMetrics(), config.UseProxyProtocol)
 	err = connector.StartAcceptingConnections(ctx,
 		net.JoinHostPort("", strconv.Itoa(config.Port)),
 		config.ConnectionRateLimit,

go.mod

@@ -14,6 +14,7 @@ require (
 	github.com/influxdata/influxdb1-client v0.0.0-20191209144304-8bf82d3c094d
 	github.com/itzg/go-flagsfiller v1.4.2
 	github.com/juju/ratelimit v1.0.1
+	github.com/pires/go-proxyproto v0.6.1
 	github.com/pkg/errors v0.8.1
 	github.com/sirupsen/logrus v1.4.1
 	github.com/stretchr/testify v1.4.0

go.sum

@@ -53,7 +53,6 @@ github.com/google/btree v1.0.0/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
 github.com/google/go-cmp v0.3.0 h1:crn/baboCvb5fXaQ0IJ1SGTsTVrWpDsCWC8EGETZijY=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
-github.com/google/gofuzz v1.0.0 h1:A8PeW59pxE9IoFRqBp37U+mSNaQoZ46F1f0f863XSXw=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
 github.com/google/gofuzz v1.1.0 h1:Hsa8mG0dQ46ij8Sl2AYJDUv1oA9/d6Vk+3LG99Oe02g=
 github.com/google/gofuzz v1.1.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
@@ -83,7 +82,6 @@ github.com/influxdata/influxdb1-client v0.0.0-20191209144304-8bf82d3c094d h1:/WZ
 github.com/influxdata/influxdb1-client v0.0.0-20191209144304-8bf82d3c094d/go.mod h1:qj24IKcXYK6Iy9ceXlo3Tc+vtHo9lIhSX5JddghvEPo=
 github.com/itzg/go-flagsfiller v1.4.2 h1:aQRyQ9/ps111FZYGhzxgKYiOewE7zbAks7rxF49Qlm8=
 github.com/itzg/go-flagsfiller v1.4.2/go.mod h1:mfQgTahSs4OHn8PYev2Wwi1LJXUiYiGuZVCpBLxzbYs=
-github.com/json-iterator/go v1.1.6 h1:MrUvLMLTMxbqFJ9kzlvat/rYZqZnW3u4wkLzWTaFwKs=
 github.com/json-iterator/go v1.1.6/go.mod h1:+SdeFBvtyEkXs7REEP0seUULqWtbJapLOCVDaaPEHmU=
 github.com/json-iterator/go v1.1.8 h1:QiWkFLKq0T7mpzwOTu6BzNDbfTE8OLrYhVKYMLF46Ok=
 github.com/json-iterator/go v1.1.8/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
@@ -114,6 +112,8 @@ github.com/onsi/ginkgo v1.11.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+
 github.com/onsi/gomega v0.0.0-20170829124025-dcabb60a477c/go.mod h1:C1qb7wdrVGGVU+Z6iS04AVkA3Q65CEZX59MT0QO5uiA=
 github.com/onsi/gomega v1.7.0/go.mod h1:ex+gbHU/CVuBBDIJjb2X0qEXbFg53c61hWP/1CpauHY=
 github.com/peterbourgon/diskv v2.0.1+incompatible/go.mod h1:uqqh8zWWbv1HBMNONnaR/tNboyR3/BZd58JJSHlUSCU=
+github.com/pires/go-proxyproto v0.6.1 h1:EBupykFmo22SDjv4fQVQd2J9NOoLPmyZA/15ldOGkPw=
+github.com/pires/go-proxyproto v0.6.1/go.mod h1:Odh9VFOZJCf9G8cLW5o435Xf1J95Jw9Gw5rnCjcwzAY=
 github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
@@ -126,7 +126,6 @@ github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
@@ -168,7 +167,6 @@ golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20191022100944-742c48ecaeb7 h1:HmbHVPwrPEKPGLAcHSrMe6+hqSUlvZU0rab6x5EXfGU=
 golang.org/x/sys v0.0.0-20191022100944-742c48ecaeb7/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.0.0-20160726164857-2910a502d2bf/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2 h1:tW2bmiBqwgJj/UpqtC8EpXEZVYOwU0yG4iWbprSVAcs=
@@ -184,7 +182,6 @@ golang.org/x/tools v0.0.0-20190226205152-f727befe758c/go.mod h1:9Yl7xja0Znq3iFh3
 golang.org/x/tools v0.0.0-20190312170243-e65039ee4138/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
 google.golang.org/api v0.4.0/go.mod h1:8k5glujaEP+g9n7WNsDg8QP6cUVNI86fCNMcbazEtwE=
 google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
-google.golang.org/appengine v1.4.0 h1:/wp5JvzpHIxhs/dumFmF7BXTf3Z+dd4uXta4kVyO508=
 google.golang.org/appengine v1.4.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
 google.golang.org/appengine v1.5.0 h1:KxkO13IPW4Lslp2bz+KHP2E3gtFlrIGNThxkZQ3g+4c=
 google.golang.org/appengine v1.5.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
@@ -192,7 +189,6 @@ google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoA
 google.golang.org/genproto v0.0.0-20190307195333-5fe7a883aa19/go.mod h1:VzzqZJRnGkLBvHegQrXjBqPurQTc5/KpmUdxsrq26oE=
 google.golang.org/genproto v0.0.0-20190418145605-e7d98fc518a7/go.mod h1:VzzqZJRnGkLBvHegQrXjBqPurQTc5/KpmUdxsrq26oE=
 google.golang.org/grpc v1.19.0/go.mod h1:mqu4LbDTu4XGKhr4mRzUsmM4RtVoemTSY81AxZiDr8c=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
@@ -201,7 +197,6 @@ gopkg.in/inf.v0 v0.9.1 h1:73M5CoZyi3ZLMOyDlQh031Cx6N9NDJ2Vvfl76EDAgDc=
 gopkg.in/inf.v0 v0.9.1/go.mod h1:cWUDdTG/fYaXco+Dcufb5Vnc6Gp2YChqWtbxRZE0mXw=
 gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7/go.mod h1:dt/ZhP58zS4L8KSrWDmTeBkI65Dw0HsyUHuEVlX15mw=
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.8 h1:obN1ZagJSUGI0Ek/LBmuj4SNLPfIny3KsKFopxRdj10=
 gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
@@ -215,7 +210,6 @@ k8s.io/client-go v0.18.5 h1:cLhGZdOmyPhwtt20Lrb7uAqxxB1uvY+NTmNJvno1oKA=
 k8s.io/client-go v0.18.5/go.mod h1:EsiD+7Fx+bRckKWZXnAXRKKetm1WuzPagH4iOSC8x58=
 k8s.io/gengo v0.0.0-20190128074634-0689ccc1d7d6/go.mod h1:ezvh/TsK7cY6rbqRK0oQQ8IAqLxYwwyPxAX1Pzy0ii0=
 k8s.io/klog v0.0.0-20181102134211-b9b56d5dfc92/go.mod h1:Gq+BEi5rUBO/HRz0bTSXDUcqjScdoY3a9IHpCEIOOfk=
-k8s.io/klog v0.3.0 h1:0VPpR+sizsiivjIfIAQH/rl8tan6jvWkS7lU+0di3lE=
 k8s.io/klog v0.3.0/go.mod h1:Gq+BEi5rUBO/HRz0bTSXDUcqjScdoY3a9IHpCEIOOfk=
 k8s.io/klog v1.0.0 h1:Pt+yjF5aB1xDSVbau4VsWe+dQNzA0qv1LlXdC2dF6Q8=
 k8s.io/klog v1.0.0/go.mod h1:4Bi6QPql/J/LkTDqv7R/cd3hPo4k2DG6Ptcz060Ez5I=
@@ -225,7 +219,6 @@ k8s.io/utils v0.0.0-20200324210504-a9aa75ae1b89/go.mod h1:sZAwmy6armz5eXlNoLmJcl
 sigs.k8s.io/structured-merge-diff/v3 v3.0.0-20200116222232-67a7b8c61874/go.mod h1:PlARxl6Hbt/+BC80dRLi1qAmnMqwqDg62YvvVkZjemw=
 sigs.k8s.io/structured-merge-diff/v3 v3.0.0 h1:dOmIZBMfhcHS09XZkMyUgkq5trg3/jRyJYFZUiaOp8E=
 sigs.k8s.io/structured-merge-diff/v3 v3.0.0/go.mod h1:PlARxl6Hbt/+BC80dRLi1qAmnMqwqDg62YvvVkZjemw=
-sigs.k8s.io/yaml v1.1.0 h1:4A07+ZFc2wgJwo8YNlQpr1rVlgUDlxXHhPJciaPY5gs=
 sigs.k8s.io/yaml v1.1.0/go.mod h1:UJmg0vDUVViEyp3mgSv9WPwZCDxu4rQW1olrI1uml+o=
 sigs.k8s.io/yaml v1.2.0 h1:kr/MCeFWJWTwyaHoR9c8EjH9OumOmoF9YGiZd7lFm/Q=
 sigs.k8s.io/yaml v1.2.0/go.mod h1:yfXDCHCao9+ENCvLSE62v9VSji2MKu5jeNfTrofGhJc=

server/connector.go

@@ -6,9 +6,11 @@ import (
 	"github.com/go-kit/kit/metrics"
 	"github.com/itzg/mc-router/mcproto"
 	"github.com/juju/ratelimit"
+	"github.com/pires/go-proxyproto"
 	"github.com/sirupsen/logrus"
 	"io"
 	"net"
+	"strconv"
 	"time"
 )
 
@@ -29,16 +31,18 @@ type ConnectorMetrics struct {
 	ActiveConnections metrics.Gauge
 }
 
-func NewConnector(metrics *ConnectorMetrics) Connector {
+func NewConnector(metrics *ConnectorMetrics, sendProxyProto bool) Connector {
 
 	return &connectorImpl{
 		metrics:        metrics,
+		sendProxyProto: sendProxyProto,
 	}
 }
 
 type connectorImpl struct {
 	state          mcproto.State
 	metrics        *ConnectorMetrics
+	sendProxyProto bool
 }
 
 func (c *connectorImpl) StartAcceptingConnections(ctx context.Context, listenAddress string, connRateLimit int) error {
@@ -189,12 +193,45 @@ func (c *connectorImpl) findAndConnectBackend(ctx context.Context, frontendConn
 	c.metrics.ActiveConnections.Add(1)
 	defer c.metrics.ActiveConnections.Add(-1)
 
+	// PROXY protocol implementation
+	if c.sendProxyProto {
+		remoteHostStr, _, _ := net.SplitHostPort(backendHostPort)
+		sourceAddrStr, sourcePortStr, _ := net.SplitHostPort(clientAddr.String())
+		sourcePort, _ := strconv.Atoi(sourcePortStr)
+
+		header := &proxyproto.Header{
+			Version:           2,
+			Command:           proxyproto.PROXY,
+			TransportProtocol: proxyproto.TCPv4,
+			SourceAddr: &net.TCPAddr{
+				IP:   net.ParseIP(sourceAddrStr),
+				Port: sourcePort,
+			},
+			DestinationAddr: &net.TCPAddr{
+				IP: net.ParseIP(remoteHostStr),
+			},
+		}
+
+		_, err = header.WriteTo(backendConn)
+		if err != nil {
+			logrus.
+				WithError(err).
+				WithField("clientAddr", header.SourceAddr).
+				WithField("destAddr", header.DestinationAddr).
+				Error("Failed to write PROXY header")
+			c.metrics.Errors.With("type", "proxy_write").Add(1)
+			_ = backendConn.Close()
+			return
+		}
+	}
+
 	amount, err := io.Copy(backendConn, preReadContent)
 	if err != nil {
 		logrus.WithError(err).Error("Failed to write handshake to backend connection")
 		c.metrics.Errors.With("type", "backend_failed").Add(1)
 		return
 	}
+
 	logrus.WithField("amount", amount).Debug("Relayed handshake to backend")
 	if err = frontendConn.SetReadDeadline(noDeadline); err != nil {
 		logrus.
@@ -204,6 +241,7 @@ func (c *connectorImpl) findAndConnectBackend(ctx context.Context, frontendConn
 		c.metrics.Errors.With("type", "read_deadline").Add(1)
 		return
 	}
+
 	c.pumpConnections(ctx, frontendConn, backendConn)
 	return
 }