service,lbmap: Use consistent hashing for LB maps

Currently, it's been implemented in very crude way, just as PoC.

Signed-off-by: Martynas Pumputis <m@lambda.lt>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

pkg/maps/lbmap/lbmap.go

@@ -24,6 +24,7 @@ import (
 	"github.com/cilium/cilium/pkg/loadbalancer"
 	"github.com/cilium/cilium/pkg/logging"
 	"github.com/cilium/cilium/pkg/logging/logfields"
+	"github.com/cilium/cilium/pkg/maglev"
 	"github.com/cilium/cilium/pkg/option"
 	"github.com/cilium/cilium/pkg/u8proto"
 
@@ -50,7 +51,7 @@ type LBBPFMap struct{}
 // so that the function can remove obsolete ones.
 func (*LBBPFMap) UpsertService(
 	svcID uint16, svcIP net.IP, svcPort uint16,
-	backendIDs []uint16, prevBackendCount int,
+	backends map[string]uint16, prevBackendCount int,
 	ipv6 bool, svcType loadbalancer.SVCType, svcLocal bool,
 	svcScope uint8, sessionAffinity bool, sessionAffinityTimeoutSec uint32,
 	checkSourceRange bool) error {
@@ -68,6 +69,30 @@ func (*LBBPFMap) UpsertService(
 
 	slot := 1
 	svcVal := svcKey.NewValue().(ServiceValue)
+
+	var backendIDs []uint16
+	// TODO(brb) add param "cHash bool" to control the following
+	if svcType == loadbalancer.SVCTypeNodePort ||
+		svcType == loadbalancer.SVCTypeExternalIPs ||
+		svcType == loadbalancer.SVCTypeLoadBalancer {
+
+		backendNames := make([]string, 0, len(backends))
+		for name := range backends {
+			backendNames = append(backendNames, name)
+		}
+		m := uint64(113) // TODO(brb) configure
+		table := maglev.GetLookupTable(backendNames, m)
+		backendIDs = make([]uint16, m)
+		for i, pos := range table {
+			backendIDs[i] = backends[backendNames[pos]]
+		}
+	} else {
+		backendIDs = make([]uint16, 0, len(backends))
+		for _, id := range backends {
+			backendIDs = append(backendIDs, id)
+		}
+	}
+
 	for _, backendID := range backendIDs {
 		if backendID == 0 {
 			return fmt.Errorf("Invalid backend ID 0")

pkg/maps/lbmap/lbmap_mock.go

@@ -39,16 +39,16 @@ func NewLBMockMap() *LBMockMap {
 }
 
 func (m *LBMockMap) UpsertService(id uint16, ip net.IP, port uint16,
-	backendIDs []uint16, prevCount int, ipv6 bool, svcType lb.SVCType, svcLocal bool,
+	backends map[string]uint16, prevCount int, ipv6 bool, svcType lb.SVCType, svcLocal bool,
 	svcScope uint8, sessionAffinity bool, sessionAffinityTimeoutSec uint32, checkLBSrcRange bool) error {
 
-	backends := make([]lb.Backend, len(backendIDs))
-	for i, backendID := range backendIDs {
+	backendsList := make([]lb.Backend, 0, len(backends))
+	for name, backendID := range backends {
 		b, found := m.BackendByID[backendID]
 		if !found {
-			return fmt.Errorf("Backend %d not found", id)
+			return fmt.Errorf("Backend %s (%d) not found", name, id)
 		}
-		backends[i] = *b
+		backendsList = append(backendsList, *b)
 	}
 
 	svc, found := m.ServiceByID[id]
@@ -60,7 +60,7 @@ func (m *LBMockMap) UpsertService(id uint16, ip net.IP, port uint16,
 			return fmt.Errorf("Invalid backends count: %d vs %d", prevCount, len(svc.Backends))
 		}
 	}
-	svc.Backends = backends
+	svc.Backends = backendsList
 	svc.SessionAffinity = sessionAffinity
 	svc.SessionAffinityTimeoutSec = sessionAffinityTimeoutSec
 

pkg/service/service.go

@@ -42,8 +42,8 @@ var (
 
 // LBMap is the interface describing methods for manipulating service maps.
 type LBMap interface {
-	UpsertService(uint16, net.IP, uint16, []uint16, int, bool, lb.SVCType, bool,
-		uint8, bool, uint32, bool) error
+	UpsertService(uint16, net.IP, uint16, map[string]uint16, int, bool, lb.SVCType,
+		bool, uint8, bool, uint32, bool) error
 	DeleteService(lb.L3n4AddrID, int) error
 	AddBackend(uint16, net.IP, uint16, bool) error
 	DeleteBackendByID(uint16, bool) error
@@ -655,15 +655,15 @@ func (s *Service) upsertServiceIntoLBMaps(svc *svcInfo, onlyLocalBackends bool,
 	}
 
 	// Upsert service entries into BPF maps
-	backendIDs := make([]uint16, len(svc.backends))
-	for i, b := range svc.backends {
-		backendIDs[i] = uint16(b.ID)
+	backends := make(map[string]uint16, len(svc.backends))
+	for _, b := range svc.backends {
+		backends[b.String()] = uint16(b.ID)
 	}
 
 	err := s.lbmap.UpsertService(
 		uint16(svc.frontend.ID), svc.frontend.L3n4Addr.IP,
 		svc.frontend.L3n4Addr.L4Addr.Port,
-		backendIDs, prevBackendCount,
+		backends, prevBackendCount,
 		ipv6, svc.svcType, onlyLocalBackends,
 		svc.frontend.L3n4Addr.Scope,
 		svc.sessionAffinity, svc.sessionAffinityTimeoutSec,