Fix ACL mode advertisement and detection (#7451)

These changes are necessary to ensure advertisement happens correctly even when datacenters are connected via network areas in Consul enterprise.

This also changes how we check if ACLs can be upgraded within the local datacenter. Previously we would iterate through all LAN members. Now we just use the ServerLookup type to iterate through all known servers in the DC.

agent/consul/acl_server.go

@@ -1,12 +1,15 @@
 package consul
 
 import (
+	"fmt"
 	"sync/atomic"
 	"time"
 
 	"github.com/hashicorp/consul/acl"
+	"github.com/hashicorp/consul/agent/metadata"
 	"github.com/hashicorp/consul/agent/structs"
 	"github.com/hashicorp/consul/lib"
+	"github.com/hashicorp/serf/serf"
 )
 
 var serverACLCacheConfig *structs.ACLCachesConfig = &structs.ACLCachesConfig{
@@ -84,19 +87,81 @@ func (s *Server) checkBindingRuleUUID(id string) (bool, error) {
 	return !structs.ACLIDReserved(id), nil
 }
 
+func (s *Server) updateSerfTags(key, value string) {
+	// Update the LAN serf
+	lib.UpdateSerfTag(s.serfLAN, key, value)
+
+	if s.serfWAN != nil {
+		lib.UpdateSerfTag(s.serfWAN, key, value)
+	}
+
+	s.updateEnterpriseSerfTags(key, value)
+}
+
 func (s *Server) updateACLAdvertisement() {
 	// One thing to note is that once in new ACL mode the server will
 	// never transition to legacy ACL mode. This is not currently a
 	// supported use case.
-
-	// always advertise to all the LAN Members
-	lib.UpdateSerfTag(s.serfLAN, "acls", string(structs.ACLModeEnabled))
-	s.updateSegmentACLAdvertisements()
-
-	if s.serfWAN != nil {
-		// advertise on the WAN only when we are inside the ACL datacenter
-		lib.UpdateSerfTag(s.serfWAN, "acls", string(structs.ACLModeEnabled))
+	s.updateSerfTags("acls", string(structs.ACLModeEnabled))
 }
+
+type serversACLMode struct {
+	// leader is the address of the leader
+	leader string
+
+	// mode indicates the overall ACL mode of the servers
+	mode structs.ACLMode
+
+	// leaderMode is the ACL mode of the leader server
+	leaderMode structs.ACLMode
+
+	// indicates that at least one server was processed
+	found bool
+
+	//
+	server *Server
+}
+
+func (s *serversACLMode) init(leader string) {
+	s.leader = leader
+	s.mode = structs.ACLModeEnabled
+	s.leaderMode = structs.ACLModeUnknown
+	s.found = false
+}
+
+func (s *serversACLMode) update(srv *metadata.Server) bool {
+	fmt.Printf("Processing server acl mode for: %s - %s\n", srv.Name, srv.ACLs)
+	if srv.Status != serf.StatusAlive && srv.Status != serf.StatusFailed {
+		// they are left or something so regardless we treat these servers as meeting
+		// the version requirement
+		return true
+	}
+
+	// mark that we processed at least one server
+	s.found = true
+
+	if srvAddr := srv.Addr.String(); srvAddr == s.leader {
+		s.leaderMode = srv.ACLs
+	}
+
+	switch srv.ACLs {
+	case structs.ACLModeDisabled:
+		// anything disabled means we cant enable ACLs
+		s.mode = structs.ACLModeDisabled
+	case structs.ACLModeEnabled:
+		// do nothing
+	case structs.ACLModeLegacy:
+		// This covers legacy mode and older server versions that don't advertise ACL support
+		if s.mode != structs.ACLModeDisabled && s.mode != structs.ACLModeUnknown {
+			s.mode = structs.ACLModeLegacy
+		}
+	default:
+		if s.mode != structs.ACLModeDisabled {
+			s.mode = structs.ACLModeUnknown
+		}
+	}
+
+	return true
 }
 
 func (s *Server) canUpgradeToNewACLs(isLeader bool) bool {
@@ -105,24 +170,31 @@ func (s *Server) canUpgradeToNewACLs(isLeader bool) bool {
 		return false
 	}
 
+	var state serversACLMode
 	if !s.InACLDatacenter() {
-		numServers, mode, _ := ServersGetACLMode(s.WANMembers(), "", s.config.ACLDatacenter)
-		if mode != structs.ACLModeEnabled || numServers == 0 {
+		state.init("")
+		// use the router to check server information for non-local datacenters
+		s.router.CheckServers(s.config.ACLDatacenter, state.update)
+		if state.mode != structs.ACLModeEnabled || !state.found {
+			s.logger.Info("Cannot upgrade to new ACLs, servers in acl datacenter are not yet upgraded", "ACLDatacenter", s.config.ACLDatacenter, "mode", state.mode, "found", state.found)
 			return false
 		}
 	}
 
+	state.init(string(s.raft.Leader()))
+	// this uses the serverLookup instead of the router as its for the local datacenter
+	s.serverLookup.CheckServers(state.update)
 	if isLeader {
-		if _, mode, _ := ServersGetACLMode(s.LANMembers(), "", ""); mode == structs.ACLModeLegacy {
+		if state.mode == structs.ACLModeLegacy {
 			return true
 		}
 	} else {
-		leader := string(s.raft.Leader())
-		if _, _, leaderMode := ServersGetACLMode(s.LANMembers(), leader, ""); leaderMode == structs.ACLModeEnabled {
+		if state.leaderMode == structs.ACLModeEnabled {
 			return true
 		}
 	}
 
+	s.logger.Info("Cannot upgrade to new ACLs", "leaderMode", state.leaderMode, "mode", state.mode, "found", state.found, "leader", state.leader)
 	return false
 }
 

agent/consul/acl_server_oss.go

@@ -16,6 +16,3 @@ func (s *Server) ResolveEntTokenToIdentityAndAuthorizer(token string) (structs.A
 func (s *Server) validateEnterpriseToken(identity structs.ACLIdentity) error {
 	return nil
 }
-
-// Consul-enterprise only
-func (s *Server) updateSegmentACLAdvertisements() {}

agent/consul/enterprise_server_oss.go

@@ -62,3 +62,9 @@ func (s *Server) validateEnterpriseRequest(entMeta *structs.EnterpriseMeta, writ
 func (_ *Server) addEnterpriseSerfTags(_ map[string]string) {
 	// do nothing
 }
+
+// updateEnterpriseSerfTags in enterprise will update any instances of Serf with the tag that
+// are not the normal LAN or WAN serf instances (network segments and network areas)
+func (_ *Server) updateEnterpriseSerfTags(_, _ string) {
+	// do nothing
+}

agent/consul/server_lookup.go

@@ -63,3 +63,14 @@ func (sl *ServerLookup) Servers() []*metadata.Server {
 	}
 	return ret
 }
+
+func (sl *ServerLookup) CheckServers(fn func(srv *metadata.Server) bool) {
+	sl.lock.RLock()
+	defer sl.lock.RUnlock()
+
+	for _, srv := range sl.addressToServer {
+		if !fn(srv) {
+			return
+		}
+	}
+}

agent/consul/server_serf.go

@@ -207,6 +207,7 @@ func (s *Server) lanEventHandler() {
 			case serf.EventUser:
 				s.localEvent(e.(serf.UserEvent))
 			case serf.EventMemberUpdate:
+				s.lanNodeUpdate(e.(serf.MemberEvent))
 				s.localMemberEvent(e.(serf.MemberEvent))
 			case serf.EventQuery: // Ignore
 			default: