Default node-ip from flannel-iface

pkg/cli/agent/agent.go

@@ -13,6 +13,7 @@ import (
 	"github.com/rancher/k3s/pkg/agent"
 	"github.com/rancher/k3s/pkg/cli/cmds"
 	"github.com/rancher/k3s/pkg/datadir"
+	"github.com/rancher/k3s/pkg/netutil"
 	"github.com/sirupsen/logrus"
 	"github.com/urfave/cli"
 )
@@ -56,6 +57,10 @@ func Run(ctx *cli.Context) error {
 		return fmt.Errorf("--server is required")
 	}
 
+	if cmds.AgentConfig.FlannelIface != "" && cmds.AgentConfig.NodeIP == "" {
+		cmds.AgentConfig.NodeIP = netutil.GetIPFromInterface(cmds.AgentConfig.FlannelIface)
+	}
+
 	logrus.Infof("Starting k3s agent %s", ctx.App.Version)
 
 	dataDir, err := datadir.LocalHome(cmds.AgentConfig.DataDir, cmds.AgentConfig.Rootless)

pkg/cli/server/server.go

@@ -10,6 +10,8 @@ import (
 	"strings"
 	"time"
 
+	"github.com/rancher/k3s/pkg/netutil"
+
 	systemd "github.com/coreos/go-systemd/daemon"
 	"github.com/docker/docker/pkg/reexec"
 	"github.com/natefinch/lumberjack"
@@ -126,6 +128,10 @@ func run(app *cli.Context, cfg *cmds.Server) error {
 	serverConfig.ControlConfig.AdvertisePort = cfg.AdvertisePort
 	serverConfig.ControlConfig.BootstrapType = cfg.BootstrapType
 
+	if cmds.AgentConfig.FlannelIface != "" && cmds.AgentConfig.NodeIP == "" {
+		cmds.AgentConfig.NodeIP = netutil.GetIPFromInterface(cmds.AgentConfig.FlannelIface)
+	}
+
 	if serverConfig.ControlConfig.AdvertiseIP == "" && cmds.AgentConfig.NodeIP != "" {
 		serverConfig.ControlConfig.AdvertiseIP = cmds.AgentConfig.NodeIP
 	}

pkg/netutil/iface.go

@@ -0,0 +1,57 @@
+package netutil
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+)
+
+func GetIPFromInterface(ifaceName string) string {
+	ip, err := getIPFromInterface(ifaceName)
+	if err != nil {
+		logrus.Warn(errors.Wrap(err, "unable to get global unicast ip from interface name"))
+	} else {
+		logrus.Infof("found ip %s from iface %s", ip, ifaceName)
+	}
+	return ip
+}
+
+func getIPFromInterface(ifaceName string) (string, error) {
+	iface, err := net.InterfaceByName(ifaceName)
+	if err != nil {
+		return "", err
+	}
+	addrs, err := iface.Addrs()
+	if err != nil {
+		return "", err
+	}
+	if iface.Flags&net.FlagUp == 0 {
+		return "", fmt.Errorf("the interface %s is not up", ifaceName)
+	}
+
+	globalUnicasts := []string{}
+	for _, addr := range addrs {
+		ip, _, err := net.ParseCIDR(addr.String())
+		if err != nil {
+			return "", errors.Wrapf(err, "unable to parse CIDR for interface %s", iface.Name)
+		}
+		// skipping if not ipv4
+		if ip.To4() == nil {
+			continue
+		}
+		if ip.IsGlobalUnicast() {
+			globalUnicasts = append(globalUnicasts, ip.String())
+		}
+	}
+
+	if len(globalUnicasts) > 1 {
+		return "", fmt.Errorf("multiple global unicast addresses defined for %s, please set ip from one of %v", ifaceName, globalUnicasts)
+	}
+	if len(globalUnicasts) == 1 {
+		return globalUnicasts[0], nil
+	}
+
+	return "", fmt.Errorf("can't find ip for interface %s", ifaceName)
+}