NETOBSERV-201: configure LogLevel and Sampling (#16)

* NETOBSERV-201: configure LogLevel and Sampling

* updated go mod

bpf/flows.c

@@ -23,6 +23,9 @@ struct {
     __uint(max_entries, 1 << 24);
 } flows SEC(".maps");
 
+// Constant definitions, to be overridden by the invoker
+volatile const u32 sampling = 0;
+
 // sets flow fields from IPv4 header information
 static inline int fill_iphdr(struct iphdr *ip, void *data_end, struct flow *flow) {
     if ((void *)ip + sizeof(*ip) > data_end) {
@@ -72,6 +75,12 @@ static inline int fill_ethhdr(struct ethhdr *eth, void *data_end, struct flow *f
 
 // parses flow information for a given direction (ingress/egress)
 static inline int flow_parse(struct __sk_buff *skb, u8 direction) {
+
+    // If sampling is defined, will only parse 1 out of "sampling" flows
+    if (sampling != 0 && (bpf_get_prandom_u32() % sampling) != 0) {
+        return TC_ACT_OK;
+    }
+
     void *data = (void *)(long)skb->data;
     void *data_end = (void *)(long)skb->data_end;
 

cmd/netobserv-ebpf-agent.go

@@ -21,9 +21,7 @@ func main() {
 	if err := env.Parse(&config); err != nil {
 		logrus.WithError(err).Fatal("can't load configuration from environment")
 	}
-	if config.Verbose {
-		logrus.SetLevel(logrus.DebugLevel)
-	}
+	setLoggerVerbosity(&config)
 
 	logrus.WithField("configuration", fmt.Sprintf("%#v", config)).Debugf("configuration loaded")
 
@@ -45,3 +43,12 @@ func main() {
 		logrus.WithError(err).Fatal("can't start netobserv-ebpf-agent")
 	}
 }
+
+func setLoggerVerbosity(cfg *agent.Config) {
+	lvl, err := logrus.ParseLevel(cfg.LogLevel)
+	if err != nil {
+		logrus.WithError(err).Warn("assuming 'info' logger level as default")
+		lvl = logrus.InfoLevel
+	}
+	logrus.SetLevel(lvl)
+}

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/sirupsen/logrus v1.8.1
 	github.com/stretchr/testify v1.7.1
 	github.com/vishvananda/netlink v1.1.0
+	golang.org/x/sys v0.0.0-20220412211240-33da011f77ad
 	google.golang.org/grpc v1.45.0
 	google.golang.org/protobuf v1.28.0
 )
@@ -22,7 +23,6 @@ require (
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/vishvananda/netns v0.0.0-20191106174202-0a2b9b5464df // indirect
 	golang.org/x/net v0.0.0-20220412020605-290c469a71a5 // indirect
-	golang.org/x/sys v0.0.0-20220412211240-33da011f77ad // indirect
 	golang.org/x/text v0.3.7 // indirect
 	golang.org/x/xerrors v0.0.0-20220411194840-2f41105eb62f // indirect
 	google.golang.org/genproto v0.0.0-20220407144326-9054f6ed7bac // indirect

pkg/agent/agent.go

@@ -42,7 +42,7 @@ func FlowsAgent(cfg *Config) (*Flows, error) {
 	}
 	tracers := map[string]flowTracer{}
 	for iface := range interfaces {
-		tracers[iface] = ebpf.NewFlowTracer(iface)
+		tracers[iface] = ebpf.NewFlowTracer(iface, cfg.Sampling)
 	}
 	target := fmt.Sprintf("%s:%d", cfg.TargetHost, cfg.TargetPort)
 	grpcExporter, err := exporter.StartGRPCProto(target)

pkg/agent/agent_test.go

@@ -28,7 +28,6 @@ func TestFlowsAgent(t *testing.T) {
 	flowsAgent, err := FlowsAgent(&Config{
 		TargetHost:         "127.0.0.1",
 		TargetPort:         port,
-		Verbose:            true,
 		CacheMaxFlows:      1,
 		CacheActiveTimeout: 5 * time.Second,
 		BuffersLength:      10,

pkg/agent/config.go

@@ -32,8 +32,11 @@ type Config struct {
 	// CacheActiveTimeout specifies the maximum duration in which a flow is kept in the accounting
 	// cache before being flushed for its later export
 	CacheActiveTimeout time.Duration `env:"CACHE_ACTIVE_TIMEOUT" envDefault:"5s"`
-	// Verbose logs mode
-	Verbose bool `env:"VERBOSE" envDefault:"false"`
+	// 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.
+	// E.g. if set to 100, one out of 100 packets, on average, will be sent to each target collector.
+	Sampling uint32 `env:"SAMPLING" envDefault:"0"`
 }
 
 func getInterfaces(cfg *Config, interfaces func() ([]net.Interface, error)) (map[string]struct{}, error) {

pkg/ebpf/tracer.go

@@ -15,6 +15,7 @@ import (
 	"github.com/netobserv/netobserv-ebpf-agent/pkg/flow"
 	"github.com/sirupsen/logrus"
 	"github.com/vishvananda/netlink"
+	"golang.org/x/sys/unix"
 )
 
 // $BPF_CLANG and $BPF_CFLAGS are set by the Makefile.
@@ -22,6 +23,8 @@ import (
 
 const (
 	qdiscType = "clsact"
+	// constants defined in flows.c as "volatile const"
+	constSampling = "sampling"
 )
 
 var log = logrus.WithField("component", "ebpf.FlowTracer")
@@ -29,6 +32,7 @@ var log = logrus.WithField("component", "ebpf.FlowTracer")
 // FlowTracer reads and forwards the Flows from the Transmission Control, for a given interface.
 type FlowTracer struct {
 	interfaceName string
+	sampling      uint32
 	objects       bpfObjects
 	qdisc         *netlink.GenericQdisc
 	egressFilter  *netlink.BpfFilter
@@ -37,10 +41,11 @@ type FlowTracer struct {
 }
 
 // NewFlowTracer fo a given interface type
-func NewFlowTracer(iface string) *FlowTracer {
+func NewFlowTracer(iface string, sampling uint32) *FlowTracer {
 	log.WithField("iface", iface).Debug("Instantiating flow tracer")
 	return &FlowTracer{
 		interfaceName: iface,
+		sampling:      sampling,
 	}
 }
 
@@ -53,9 +58,18 @@ func (m *FlowTracer) Register() error {
 	if err := rlimit.RemoveMemlock(); err != nil {
 		return fmt.Errorf("removing mem lock: %w", err)
 	}
-	// Load pre-compiled programs and maps into the kernel.
-	if err := loadBpfObjects(&m.objects, nil); err != nil {
-		return fmt.Errorf("loading objects: %w", err)
+	// Load pre-compiled programs and maps into the kernel, and rewrites the configuration
+	spec, err := loadBpf()
+	if err != nil {
+		return fmt.Errorf("loading BPF data: %w", err)
+	}
+	if err := spec.RewriteConstants(map[string]interface{}{
+		constSampling: m.sampling,
+	}); err != nil {
+		return fmt.Errorf("rewriting BPF constants definition: %w", err)
+	}
+	if err := spec.LoadAndAssign(&m.objects, nil); err != nil {
+		return fmt.Errorf("loading and assigning BPF objects: %w", err)
 	}
 	ipvlan, err := netlink.LinkByName(m.interfaceName)
 	if err != nil {
@@ -110,7 +124,7 @@ func (m *FlowTracer) Register() error {
 		LinkIndex: ipvlan.Attrs().Index,
 		Parent:    netlink.HANDLE_MIN_INGRESS,
 		Handle:    netlink.MakeHandle(0, 1),
-		Protocol:  3,
+		Protocol:  unix.ETH_P_ALL,
 		Priority:  1,
 	}
 	m.ingressFilter = &netlink.BpfFilter{

scripts/generators.Dockerfile

 FROM fedora:35
 
-ARG GOVERSION="1.17.8"
+ARG GOVERSION="1.17.9"
 ARG PROTOCVERSION="3.19.4"
 
 # Installs dependencies that are required to compile eBPF programs