detectPublicIPv4: try to detect ipv4's from interfaces with a default…

… gateway first (#493) #### detectPublicIPv4: try to detect ipv4's from interfaces with a default gateway first - adds github.com/vishvananda/netlink to get at the routing tables - if none found, old logic is kept (gets the first IPv4 from the first interface that has one) Signed-off-by: Ricardo Pardini <[email protected]>
tinkerbell · Aug 27, 2024 · db21d79 · db21d79
2 parents 160defe + c746cb9
commit db21d79
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Showing 3 changed files with 54 additions and 1 deletion.
diff --git a/cmd/smee/flag.go b/cmd/smee/flag.go
@@ -11,8 +11,11 @@ import (
 	"text/tabwriter"
 	"time"
 
+	"golang.org/x/sys/unix"
+
 	"github.com/peterbourgon/ff/v3"
 	"github.com/peterbourgon/ff/v3/ffcli"
+	"github.com/vishvananda/netlink"
 )
 
 // customUsageFunc is a custom UsageFunc used for all commands.
@@ -172,6 +175,11 @@ func newCLI(cfg *config, fs *flag.FlagSet) *ffcli.Command {
 }
 
 func detectPublicIPv4() string {
+	ipDgw, err := autoDetectPublicIpv4WithDefaultGateway()
+	if err == nil {
+		return ipDgw.String()
+	}
+
 	ip, err := autoDetectPublicIPv4()
 	if err != nil {
 		return ""
@@ -200,3 +208,41 @@ func autoDetectPublicIPv4() (net.IP, error) {
 
 	return nil, errors.New("unable to auto-detect public IPv4")
 }
+
+// autoDetectPublicIpv4WithDefaultGateway finds the network interface with a default gateway
+// and returns the first net.IP address of the first interface that has a default gateway.
+func autoDetectPublicIpv4WithDefaultGateway() (net.IP, error) {
+	// Get the list of routes from netlink
+	routes, err := netlink.RouteList(nil, unix.AF_INET)
+	if err != nil {
+		return nil, fmt.Errorf("failed to list routes: %v", err)
+	}
+
+	// Find the route with a default gateway (Dst == nil)
+	for _, route := range routes {
+		if route.Dst == nil && route.Gw != nil {
+			// Get the interface associated with this route
+			iface, err := net.InterfaceByIndex(route.LinkIndex)
+			if err != nil {
+				return nil, fmt.Errorf("failed to get interface by index: %v", err)
+			}
+
+			// Get the addresses assigned to this interface
+			addrs, err := iface.Addrs()
+			if err != nil {
+				return nil, fmt.Errorf("failed to get addresses for interface %v: %v", iface.Name, err)
+			}
+
+			// Return the first valid IP address found
+			for _, addr := range addrs {
+				if ipNet, ok := addr.(*net.IPNet); ok && !ipNet.IP.IsLoopback() {
+					if ipNet.IP.To4() != nil {
+						return ipNet.IP, nil
+					}
+				}
+			}
+		}
+	}
+
+	return nil, fmt.Errorf("no default gateway found")
+}
diff --git a/go.mod b/go.mod
@@ -17,6 +17,7 @@ require (
 	github.com/prometheus/client_golang v1.20.0
 	github.com/tinkerbell/ipxedust v0.0.0-20240726225714-c9bd1dd89cc3
 	github.com/tinkerbell/tink v0.10.0
+	github.com/vishvananda/netlink v1.1.0
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.53.0
 	go.opentelemetry.io/otel v1.28.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.28.0
@@ -25,6 +26,7 @@ require (
 	go.uber.org/zap v1.27.0
 	golang.org/x/net v0.28.0
 	golang.org/x/sync v0.8.0
+	golang.org/x/sys v0.23.0
 	google.golang.org/grpc v1.65.0
 	k8s.io/apimachinery v0.31.0
 	k8s.io/client-go v0.30.3
@@ -80,6 +82,7 @@ require (
 	github.com/rs/zerolog v1.33.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/u-root/uio v0.0.0-20230305220412-3e8cd9d6bf63 // indirect
+	github.com/vishvananda/netns v0.0.0-20191106174202-0a2b9b5464df // indirect
 	github.com/x448/float16 v0.8.4 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.28.0 // indirect
 	go.opentelemetry.io/otel/metric v1.28.0 // indirect
@@ -88,7 +91,6 @@ require (
 	golang.org/x/crypto v0.26.0 // indirect
 	golang.org/x/exp v0.0.0-20231206192017-f3f8817b8deb // indirect
 	golang.org/x/oauth2 v0.21.0 // indirect
-	golang.org/x/sys v0.23.0 // indirect
 	golang.org/x/term v0.23.0 // indirect
 	golang.org/x/text v0.17.0 // indirect
 	golang.org/x/time v0.5.0 // indirect

diff --git a/go.sum b/go.sum
@@ -174,6 +174,10 @@ github.com/tinkerbell/tink v0.10.0 h1:W34Psx6Yn5o0jILSgyjF8C7Cg6ivDcccUqJ6zG9zGz
 github.com/tinkerbell/tink v0.10.0/go.mod h1:Dc8PpbvrC8Kfhr8yGhUsWBN6Dq6opRIX655KDTxLUJY=
 github.com/u-root/uio v0.0.0-20230305220412-3e8cd9d6bf63 h1:YcojQL98T/OO+rybuzn2+5KrD5dBwXIvYBvQ2cD3Avg=
 github.com/u-root/uio v0.0.0-20230305220412-3e8cd9d6bf63/go.mod h1:eLL9Nub3yfAho7qB0MzZizFhTU2QkLeoVsWdHtDW264=
+github.com/vishvananda/netlink v1.1.0 h1:1iyaYNBLmP6L0220aDnYQpo1QEV4t4hJ+xEEhhJH8j0=
+github.com/vishvananda/netlink v1.1.0/go.mod h1:cTgwzPIzzgDAYoQrMm0EdrjRUBkTqKYppBueQtXaqoE=
+github.com/vishvananda/netns v0.0.0-20191106174202-0a2b9b5464df h1:OviZH7qLw/7ZovXvuNyL3XQl8UFofeikI1NW1Gypu7k=
+github.com/vishvananda/netns v0.0.0-20191106174202-0a2b9b5464df/go.mod h1:JP3t17pCcGlemwknint6hfoeCVQrEMVwxRLRjXpq+BU=
 github.com/x448/float16 v0.8.4 h1:qLwI1I70+NjRFUR3zs1JPUCgaCXSh3SW62uAKT1mSBM=
 github.com/x448/float16 v0.8.4/go.mod h1:14CWIYCyZA/cWjXOioeEpHeN/83MdbZDRQHoFcYsOfg=
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
@@ -225,6 +229,7 @@ golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
 golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190606203320-7fc4e5ec1444/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20220622161953-175b2fd9d664/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=