Add load balancer IPs to "localIPs" (#167)

* Adds a function to add load balancer IPs to localIPs variable

* Adds log statement when a LB IP is added to localIPs

* Causes loadbalancerIPs() to work for both IP and CIDR formats

The values being parsed were ultimately fetched from the GCE VM metadata
server. The server seems to return IPv4 addresses in standard dotted decimal
notation, while IPv6 addresses are returned in CIDR format.

* Log errors from findDestination()

findDestination() returns an err, but it was previously unused other than to
check whether it was nil or not. This change just prints the error to help in
debugging.

* Bumps Go version to v1.21

* Adds loadbalancer IPs to handler.LocalIPs

This allows traceroute-caller to recognize the loadbalancer IPs as "local".
Without this traceroute-caller will fail to recognize its own (loadbalanced) IP
addresses and will not run any traces.

* Removes pointer from slice-of-pointers h.LocalIPs of type []*net.IP

Instead it is now just []net.IP, which is easier to work with.

* Updates Go to v1.21 in Travis-CI config

* Reverts Travis-CI config Go version back to v1.20 (1.21 not supported?)

* Sets Go version in Travis config back to 1.21, but in double quotes

* Reverts back to Go v1.20 in Travis-CI config (1.21 not supported)

Author: nkinkade

.travis.yml

@@ -1,6 +1,6 @@
 language: go
 go:
-- 1.20
+- "1.20"
 
 before_install:
 - go install github.com/mattn/goveralls@latest

go.mod

@@ -1,6 +1,6 @@
 module github.com/m-lab/traceroute-caller
 
-go 1.20
+go 1.21
 
 require (
 	github.com/go-test/deep v1.0.7

go.sum

@@ -120,6 +120,7 @@ github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/me
 github.com/go-test/deep v1.0.7 h1:/VSMRlnY/JSyqxQUzQLKVMAskpY/NZKFA5j2P+0pP2M=
 github.com/go-test/deep v1.0.7/go.mod h1:QV8Hv/iy04NyLBxAdO9njL0iVPN1S4d/A3NVv1V36o8=
 github.com/gocarina/gocsv v0.0.0-20210408192840-02d7211d929d h1:r3mStZSyjKhEcgbJ5xtv7kT5PZw/tDiFBTMgQx2qsXE=
+github.com/gocarina/gocsv v0.0.0-20210408192840-02d7211d929d/go.mod h1:5YoVOkjYAQumqlV356Hj3xeYh4BdZuLE0/nRkf2NKkI=
 github.com/gogo/protobuf v1.1.1/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7atdtwQ=
 github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
 github.com/golang/groupcache v0.0.0-20190702054246-869f871628b6/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
@@ -224,6 +225,7 @@ github.com/jstemmer/go-junit-report v0.9.1/go.mod h1:Brl9GWCQeLvo8nXZwPNNblvFj/X
 github.com/julienschmidt/httprouter v1.2.0/go.mod h1:SYymIcj16QtmaHHD7aYtjjsJG7VTCxuUUipMqKk8s4w=
 github.com/julienschmidt/httprouter v1.3.0/go.mod h1:JR6WtHb+2LUe8TCKY3cZOxFyyO8IZAc4RVcycCCAKdM=
 github.com/kabukky/httpscerts v0.0.0-20150320125433-617593d7dcb3 h1:Iy7Ifq2ysilWU4QlCx/97OoI4xT1IV7i8byT/EyIT/M=
+github.com/kabukky/httpscerts v0.0.0-20150320125433-617593d7dcb3/go.mod h1:BYpt4ufZiIGv2nXn4gMxnfKV306n3mWXgNu/d2TqdTU=
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/konsorten/go-windows-terminal-sequences v1.0.3/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
@@ -232,6 +234,7 @@ github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORN
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/m-lab/annotation-service v0.0.0-20210504151333-138bdf572368 h1:cRzgLEJxoMI0iSexWOxTZQR/gNG08ra1IoEEgwJBdgs=
+github.com/m-lab/annotation-service v0.0.0-20210504151333-138bdf572368/go.mod h1:bW5A2AmUqyh6kGbmu4X8fYK2pRcfTvTjAXW/+4VQZUA=
 github.com/m-lab/go v0.1.66 h1:adDJILqKBCkd5YeVhCrrjWkjoNRtDzlDr6uizWu5/pE=
 github.com/m-lab/go v0.1.66/go.mod h1:O1D/EoVarJ8lZt9foANcqcKtwxHatBzUxXFFyC87aQQ=
 github.com/m-lab/tcp-info v1.5.3 h1:4IspTPcNc8D8LNRvuFnID8gDiz+hxPAtYvpKZaiGGe8=
@@ -298,6 +301,7 @@ github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/yuin/goldmark v1.1.25/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.1.32/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=

internal/triggertrace/triggertrace.go

@@ -6,9 +6,12 @@ package triggertrace
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"log"
 	"net"
+	"os"
+	"strings"
 	"sync"
 	"time"
 
@@ -23,6 +26,7 @@ import (
 var (
 	// Variables to aid in black-box testing.
 	netInterfaceAddrs = net.InterfaceAddrs
+	metadataDir       = "/metadata"
 )
 
 // Destination is the host to run a traceroute to.
@@ -61,7 +65,7 @@ type TracerWriter interface {
 type Handler struct {
 	Destinations     map[string]Destination // key is UUID
 	DestinationsLock sync.Mutex
-	LocalIPs         []*net.IP
+	LocalIPs         []net.IP
 	IPCache          FetchTracer
 	Parser           ParseTracer
 	HopAnnotator     AnnotateAndArchiver
@@ -76,7 +80,7 @@ func NewHandler(ctx context.Context, tracetool TracerWriter, ipcCfg ipcache.Conf
 	if err != nil {
 		return nil, err
 	}
-	myIPs, err := localIPs()
+	myIPs, err := localIPs(metadataDir)
 	if err != nil {
 		return nil, err
 	}
@@ -115,7 +119,7 @@ func (h *Handler) Open(ctx context.Context, timestamp time.Time, uuid string, so
 	defer h.DestinationsLock.Unlock()
 	destination, err := h.findDestination(sockID)
 	if err != nil {
-		log.Printf("context %p: failed to find destination from SockID %+v\n", ctx, *sockID)
+		log.Printf("context %p: failed to find destination from SockID %+v: %v\n", ctx, *sockID, err)
 		return
 	}
 	h.Destinations[uuid] = destination
@@ -220,12 +224,13 @@ func (h *Handler) findDestination(sockid *inetdiag.SockID) (Destination, error)
 }
 
 // localIPs returns the list of system's unicast interface addresses.
-func localIPs() ([]*net.IP, error) {
-	localIPs := make([]*net.IP, 0)
+func localIPs(metadataDir string) ([]net.IP, error) {
+	localIPs := make([]net.IP, 0)
 	addrs, err := netInterfaceAddrs()
 	if err != nil {
 		return localIPs, err
 	}
+
 	for _, addr := range addrs {
 		var ip net.IP
 		switch a := addr.(type) {
@@ -237,8 +242,62 @@ func localIPs() ([]*net.IP, error) {
 			return localIPs, fmt.Errorf("unknown address type %q", addr.String())
 		}
 		if ip != nil {
-			localIPs = append(localIPs, &ip)
+			localIPs = append(localIPs, ip)
 		}
 	}
+
+	localIPs, err = loadbalancerIPs(localIPs, metadataDir)
+	if err != nil {
+		return localIPs, err
+	}
+
+	return localIPs, nil
+}
+
+// loadbalancerIPs returns the public IP addresses, if any, of a load balancer
+// that may sit in front of the machine. Not all machines site in front of a
+// load balancer, so this function may return the the same []*net.IP that was
+// passed to it. This function is necessary because traceroute-caller needs to
+// recognize the load balancer IPs as "local", else it will fail to identify a
+// proper destination, and will exit with an error, producing no traceroute data.
+func loadbalancerIPs(localIPs []net.IP, metadataDir string) ([]net.IP, error) {
+	var ip net.IP
+
+	// While every machine _should_ have a /metadata/loadbalanced file, for now
+	// consider its non-existence to mean that the machine is not load balanced.
+	if _, err := os.Stat(metadataDir + "/loadbalanced"); errors.Is(err, os.ErrNotExist) {
+		return localIPs, nil
+	}
+
+	lb, err := os.ReadFile(metadataDir + "/loadbalanced")
+	if err != nil {
+		return localIPs, fmt.Errorf("unable to read file %s/loadbalanced: %v", metadataDir, err)
+	}
+
+	// If the machine isn't load balanced, then just return localIPs unmodified.
+	if string(lb) == "false" {
+		return localIPs, nil
+	}
+
+	for _, f := range []string{"external-ip", "external-ipv6"} {
+		ipBytes, err := os.ReadFile(metadataDir + "/" + f)
+		if err != nil {
+			return localIPs, fmt.Errorf("unable to read file %s/%s: %v", metadataDir, f, err)
+		}
+		ipString := string(ipBytes)
+
+		// GCE metadata for key "forwarded-ipv6s" is returned in CIDR format.
+		if strings.Contains(ipString, "/") {
+			ip, _, _ = net.ParseCIDR(ipString)
+		} else {
+			ip = net.ParseIP(ipString)
+		}
+		if ip == nil {
+			return localIPs, fmt.Errorf("failed to parse IP: %s", ipString)
+		}
+		localIPs = append(localIPs, ip)
+		log.Printf("added load balancer IP %s to localIPs\n", ip.String())
+	}
+
 	return localIPs, nil
 }

internal/triggertrace/triggertrace_test.go

@@ -106,6 +106,11 @@ func (fa *fakeAnnotator) Annotate(ctx context.Context, ips []string) (map[string
 }
 
 func TestNewHandler(t *testing.T) {
+	var strV4 string = "77.77.88.88"
+	var strV6 string = "7777:77:888:88::"
+
+	metadataDir = "./testdata/metadata"
+
 	saveNetInterfaceAddrs := netInterfaceAddrs
 	defer func() { netInterfaceAddrs = saveNetInterfaceAddrs }()
 
@@ -114,10 +119,63 @@ func TestNewHandler(t *testing.T) {
 		t.Fatalf("NewHandler() = nil, want error")
 	}
 
+	// Set up metadata files
+	os.MkdirAll(metadataDir, 0755)
+	os.WriteFile(metadataDir+"/loadbalanced", []byte("true"), 0644)
+	os.WriteFile(metadataDir+"/external-ip", []byte(strV4), 0644)
+	os.WriteFile(metadataDir+"/external-ipv6", []byte(strV6), 0644)
+	defer os.RemoveAll(metadataDir)
+
 	netInterfaceAddrs = fakeInterfaceAddrs
-	if _, err := newHandler(t, &fakeTracer{}); err != nil {
+	handler, err := newHandler(t, &fakeTracer{})
+	addrCount := len(handler.LocalIPs)
+
+	if err != nil {
 		t.Fatalf("NewHandler() = %v, want nil", err)
 	}
+
+	var ipv4 net.IP = net.ParseIP(strV4)
+	var ipv6 net.IP = net.ParseIP(strV6)
+
+	ok := false
+	for _, v := range handler.LocalIPs {
+		if v.Equal(ipv4) {
+			ok = true
+			break
+		}
+	}
+	if !ok {
+		t.Fatalf("NewHandler(): h.LocalIPs does not contain loadbalancer IP %s", strV4)
+	}
+
+	ok = false
+	for _, v := range handler.LocalIPs {
+		if v.Equal(ipv6) {
+			ok = true
+			break
+		}
+	}
+	if !ok {
+		t.Fatalf("NewHandler(): h.LocalIPs does not contain loadbalancer IP %s", strV6)
+	}
+
+	// Setting loadbalanced=false should result in the original addrCount to
+	// stay the same, since loadbalancerIPs() should return localIPs unmodified.
+	os.WriteFile(metadataDir+"/loadbalanced", []byte("false"), 0644)
+	handler, _ = newHandler(t, &fakeTracer{})
+	if len(handler.LocalIPs) > addrCount {
+		t.Fatalf("NewHandler(): LocalIPs has %d addresses, but should have %d", len(handler.LocalIPs), addrCount)
+	}
+
+	// If the metadata file loadbalanced doesn't exist then the original
+	// addrCount should stay the same, since loadbalancerIPs() should return
+	// localIPs unmodified.
+	os.Remove(metadataDir + "/loadbalanced")
+	handler, _ = newHandler(t, &fakeTracer{})
+	if len(handler.LocalIPs) > addrCount {
+		t.Fatalf("NewHandler(): LocalIPs has %d addresses, but should have %d", len(handler.LocalIPs), addrCount)
+	}
+
 }
 
 func TestOpen(t *testing.T) {
@@ -362,7 +420,7 @@ func TestAnonymize(t *testing.T) {
 				t.Fatalf("NewHandler() = %v, want nil", err)
 			}
 			l := net.ParseIP(tt.input.Tracelb.Src)
-			h.LocalIPs = []*net.IP{&l}
+			h.LocalIPs = []net.IP{l}
 			h.done = make(chan struct{})
 			sockID := &inetdiag.SockID{SrcIP: tt.input.Tracelb.Src, DstIP: tt.input.Tracelb.Dst}
 			h.Open(context.TODO(), time.Now(), tt.name, sockID)