Allow selecting flows' direction (#58)

* Allow selecting flows' direction

* Fix typo

* make linter happy

docs/config.md

@@ -29,6 +29,8 @@ The following environment variables are available to configure the NetObserv eBF
   deduplicator. After a flow hasn't been received for that expiry time, the deduplicator forgets it.
   That means that a flow from a connection that has been inactive during that period could be
   forwarded again from a different interface.
+* `DIRECTION` (default: `both`). Allows selecting which flows to trace according to its direction.
+  Accepted values are `ingress`, `egress` or `both`.
 * `LOG_LEVEL` (default: `info`). From more to less verbose: `trace`, `debug`, `info`, `warn`,
   `error`, `fatal`, `panic`.
 * `KAFKA_BROKERS` (required if `EXPORT` is `kafka`). Comma-separated list of tha addresses of the

e2e/kafka/manifests/12-kafka-topic.yml

@@ -5,5 +5,5 @@ metadata:
   labels:
     strimzi.io/cluster: "kafka-cluster"
 spec:
-  partitions: 1
+  partitions: 12
   replicas: 1
\ No newline at end of file

pkg/agent/agent.go

@@ -130,8 +130,11 @@ func FlowsAgent(cfg *Config) (*Flows, error) {
 		return iface
 	}
 
+	ingress, egress := flowDirections(cfg)
+
 	tracer, err := ebpf.NewFlowTracer(
 		cfg.Sampling, cfg.CacheMaxFlows, cfg.BuffersLength, cfg.CacheActiveTimeout,
+		ingress, egress,
 		interfaceNamer,
 	)
 	if err != nil {
@@ -147,6 +150,20 @@ func FlowsAgent(cfg *Config) (*Flows, error) {
 	}, nil
 }
 
+func flowDirections(cfg *Config) (ingress, egress bool) {
+	switch cfg.Direction {
+	case DirectionIngress:
+		return true, false
+	case DirectionEgress:
+		return false, true
+	case DirectionBoth:
+		return true, true
+	default:
+		alog.Warnf("unknown DIRECTION %q. Tracing both ingress and egress traffic", cfg.Direction)
+		return true, true
+	}
+}
+
 // Run a Flows agent. The function will keep running in the same thread
 // until the passed context is canceled
 func (f *Flows) Run(ctx context.Context) error {

pkg/agent/config.go

@@ -9,6 +9,9 @@ const (
 	ListenWatch      = "watch"
 	DeduperNone      = "none"
 	DeduperFirstCome = "firstCome"
+	DirectionIngress = "ingress"
+	DirectionEgress  = "egress"
+	DirectionBoth    = "both"
 )
 
 type Config struct {
@@ -49,6 +52,9 @@ type Config struct {
 	// again from a different interface.
 	// If the value is not set, it will default to 2 * CacheActiveTimeout
 	DeduperFCExpiry time.Duration `env:"DEDUPER_FC_EXPIRY"`
+	// Direction allows selecting which flows to trace according to its direction. Accepted values
+	// are "ingress", "egress" or "both" (default).
+	Direction string `env:"DIRECTION" envDefault:"both"`
 	// Logger level. From more to less verbose: trace, debug, info, warn, error, fatal, panic.
 	LogLevel string `env:"LOG_LEVEL" envDefault:"info"`
 	// Sampling holds the rate at which packets should be sampled and sent to the target collector.

pkg/ebpf/tracer.go

@@ -47,12 +47,15 @@ type FlowTracer struct {
 	flowsEvictor   *sync.Cond
 	lastEvictionNs uint64
 	cacheMaxSize   int
+	enableIngress  bool
+	enableEgress   bool
 }
 
 // TODO: decouple flowtracer logic from eBPF maps access so we can inject mocks for testing
 func NewFlowTracer(
 	sampling, cacheMaxSize, buffersLength int,
 	evictionTimeout time.Duration,
+	ingress, egress bool,
 	namer flow.InterfaceNamer,
 ) (*FlowTracer, error) {
 	if err := rlimit.RemoveMemlock(); err != nil {
@@ -96,6 +99,8 @@ func NewFlowTracer(
 		flowsEvictor:    sync.NewCond(&sync.Mutex{}),
 		lastEvictionNs:  uint64(monotime.Now()),
 		cacheMaxSize:    cacheMaxSize,
+		enableIngress:   ingress,
+		enableEgress:    egress,
 	}, nil
 }
 
@@ -129,6 +134,23 @@ func (m *FlowTracer) Register(iface ifaces.Interface) error {
 	}
 	m.qdiscs[iface] = qdisc
 
+	if err := m.registerEgress(iface, ipvlan); err != nil {
+		return err
+	}
+
+	if err := m.registerIngress(iface, ipvlan); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (m *FlowTracer) registerEgress(iface ifaces.Interface, ipvlan netlink.Link) error {
+	ilog := log.WithField("iface", iface)
+	if !m.enableEgress {
+		ilog.Debug("ignoring egress traffic, according to user configuration")
+		return nil
+	}
 	// Fetch events on egress
 	egressAttrs := netlink.FilterAttrs{
 		LinkIndex: ipvlan.Attrs().Index,
@@ -146,7 +168,7 @@ func (m *FlowTracer) Register(iface ifaces.Interface) error {
 	if err := netlink.FilterDel(egressFilter); err == nil {
 		ilog.Warn("egress filter already existed. Deleted it")
 	}
-	if err = netlink.FilterAdd(egressFilter); err != nil {
+	if err := netlink.FilterAdd(egressFilter); err != nil {
 		if errors.Is(err, fs.ErrExist) {
 			ilog.WithError(err).Warn("egress filter already exists. Ignoring")
 		} else {
@@ -154,7 +176,15 @@ func (m *FlowTracer) Register(iface ifaces.Interface) error {
 		}
 	}
 	m.egressFilters[iface] = egressFilter
+	return nil
+}
 
+func (m *FlowTracer) registerIngress(iface ifaces.Interface, ipvlan netlink.Link) error {
+	ilog := log.WithField("iface", iface)
+	if !m.enableIngress {
+		ilog.Debug("ignoring ingress traffic, according to user configuration")
+		return nil
+	}
 	// Fetch events on ingress
 	ingressAttrs := netlink.FilterAttrs{
 		LinkIndex: ipvlan.Attrs().Index,
@@ -172,7 +202,7 @@ func (m *FlowTracer) Register(iface ifaces.Interface) error {
 	if err := netlink.FilterDel(ingressFilter); err == nil {
 		ilog.Warn("ingress filter already existed. Deleted it")
 	}
-	if err = netlink.FilterAdd(ingressFilter); err != nil {
+	if err := netlink.FilterAdd(ingressFilter); err != nil {
 		if errors.Is(err, fs.ErrExist) {
 			ilog.WithError(err).Warn("ingress filter already exists. Ignoring")
 		} else {
@@ -376,9 +406,9 @@ func (m *FlowTracer) listenAndForwardRingBuffer(ctx context.Context, forwardFlow
 // For synchronization purposes, we get/delete a whole snapshot of the flows map.
 // This way we avoid missing packets that could be updated on the
 // ebpf side while we process/aggregate them here
-// Changing this method invaction by BatchLookupAndDelete could improve performance
+// Changing this method invocation by BatchLookupAndDelete could improve performance
 // TODO: detect whether BatchLookupAndDelete is supported (Kernel>=5.6) and use it selectively
-// Supported Lookup/Delete oprations by kernel: https://github.com/iovisor/bcc/blob/master/docs/kernel-versions.md
+// Supported Lookup/Delete operations by kernel: https://github.com/iovisor/bcc/blob/master/docs/kernel-versions.md
 func (m *FlowTracer) lookupAndDeleteFlowsMap() map[flow.RecordKey][]flow.RecordMetrics {
 	flowMap := m.objects.AggregatedFlows