Use persisted peer name if it matches old-style ID

Makefile

@@ -71,7 +71,7 @@ testrunner: $(RUNNER_EXE) $(TEST_TLS_EXE)
 $(WEAVER_EXE) $(WEAVEPROXY_EXE) $(WEAVEUTIL_EXE): common/*.go common/*/*.go net/*.go net/*/*.go
 $(WEAVER_EXE): router/*.go ipam/*.go ipam/*/*.go db/*.go nameserver/*.go prog/weaver/*.go
 $(WEAVEPROXY_EXE): proxy/*.go prog/weaveproxy/*.go
-$(WEAVEUTIL_EXE): prog/weaveutil/*.go net/*.go plugin/net/*.go plugin/ipam/*.go
+$(WEAVEUTIL_EXE): prog/weaveutil/*.go net/*.go plugin/net/*.go plugin/ipam/*.go db/*.go
 $(SIGPROXY_EXE): prog/sigproxy/*.go
 $(KUBEPEERS_EXE): prog/kube-peers/*.go
 $(WEAVENPC_EXE): prog/weave-npc/*.go npc/*.go npc/*/*.go

net/uuid.go

@@ -1,37 +1,79 @@
 package net
 
 import (
-	"fmt"
+	"errors"
 	"io/ioutil"
 	"net"
 	"os"
+
+	"github.com/weaveworks/mesh"
+	"github.com/weaveworks/weave/db"
 )
 
+func getOldStyleSystemUUID() ([]byte, error) {
+	uuid, err := ioutil.ReadFile("/sys/class/dmi/id/product_uuid")
+	if os.IsNotExist(err) {
+		uuid, err = ioutil.ReadFile("/sys/hypervisor/uuid")
+	}
+	return uuid, err
+}
+
 func getSystemUUID(hostRoot string) ([]byte, error) {
+	uuid, err := getOldStyleSystemUUID()
+	if err != nil && !os.IsNotExist(err) {
+		return nil, err
+	}
 	machineid, err := ioutil.ReadFile(hostRoot + "/etc/machine-id")
 	if os.IsNotExist(err) {
-		machineid, _ = ioutil.ReadFile(hostRoot + "/var/lib/dbus/machine-id")
-	}
-	uuid, err := ioutil.ReadFile(hostRoot + "/sys/class/dmi/id/product_uuid")
-	if os.IsNotExist(err) {
-		uuid, _ = ioutil.ReadFile(hostRoot + "/sys/hypervisor/uuid")
+		machineid, err = ioutil.ReadFile(hostRoot + "/var/lib/dbus/machine-id")
 	}
 	if err != nil && !os.IsNotExist(err) {
 		return nil, err
 	}
-	if len(machineid)+len(uuid) == 0 {
-		return nil, fmt.Errorf("Empty system uuid")
+	if len(uuid) == 0 {
+		return nil, errors.New("All system IDs are blank")
 	}
 	return append(machineid, uuid...), nil
 }
 
+func getPersistedPeerName(pathName string) (mesh.PeerName, error) {
+	d, err := db.NewBoltDBReadOnly(pathName)
+	if err != nil {
+		return mesh.UnknownPeerName, err
+	}
+	defer d.Close()
+	var peerName mesh.PeerName
+	nameFound, err := d.Load(db.NameIdent, &peerName)
+	if err != nil || !nameFound {
+		return mesh.UnknownPeerName, err
+	}
+	return peerName, nil
+}
+
 // GetSystemPeerName returns an ID derived from concatenated machine-id
 // (either systemd or dbus), the system (aka bios) UUID and the
 // hypervisor UUID.  It is tweaked and formatted to be usable as a mac address
-func GetSystemPeerName(hostRoot string) (string, error) {
+func GetSystemPeerName(dbPrefix, hostRoot string) (string, error) {
+	// Check if we have a persisted name that matches the old-style ID for this host
+	if oldUUID, err := getOldStyleSystemUUID(); err == nil {
+		pathName := dbPrefix + db.FileName
+		if _, err := os.Stat(pathName); err == nil {
+			persistedPeerName, err := getPersistedPeerName(pathName)
+			if err != nil && !os.IsNotExist(err) {
+				return "", err
+			}
+			if persistedPeerName == mesh.PeerNameFromBin(MACfromUUID(oldUUID)) {
+				return persistedPeerName.String(), nil
+			}
+		}
+	} else if !os.IsNotExist(err) {
+		return "", err
+	}
 	var mac net.HardwareAddr
 	if uuid, err := getSystemUUID(hostRoot); err == nil {
 		mac = MACfromUUID(uuid)
+	} else if !os.IsNotExist(err) {
+		return "", err
 	} else {
 		mac, err = RandomMAC()
 		if err != nil {

prog/weaveutil/unique_id.go

@@ -7,11 +7,12 @@ import (
 )
 
 func uniqueID(args []string) error {
-	if len(args) != 1 {
-		cmdUsage("unique-id", "<host-root>")
+	if len(args) != 2 {
+		cmdUsage("unique-id", "<db-prefix> <host-root>")
 	}
-	hostRoot := args[0]
-	uid, err := weavenet.GetSystemPeerName(hostRoot)
+	dbPrefix := args[0]
+	hostRoot := args[1]
+	uid, err := weavenet.GetSystemPeerName(dbPrefix, hostRoot)
 	if err != nil {
 		return err
 	}