fake - generate random networking data for testing and benchmarks

Generate realistic random IPs, MACs, ports, Kubernetes names, and Hubble network flows — with fine-grained control over every field.

Quick start

import "github.com/cilium/fake"

f := fake.New()

f.IP()                              // "10.244.3.87" or "fd00::a1b2:..."
f.IP(fake.WithIPv4())               // always IPv4
f.IP(fake.WithIPCIDR("10.0.0.0/8")) // always in 10.0.0.0/8

f.MAC()                             // "3e:a7:01:cc:9f:12"
f.Port()                            // 1–65535
f.Port(fake.WithPortDynamic())      // 49152–65535

Kubernetes generators

f := fake.New()

f.K8sNamespace() // "kube-system" or "grafana-prod"
f.K8sPodName()   // "relay-x8f2k"
f.K8sNodeName()  // "brave-falcon"
f.K8sLabels()    // ["app=hubble", "team=relay"]

Generating Hubble flows

The flow sub-package builds complete flowpb.Flow protobufs suitable for testing Hubble pipelines, exporters, or UIs.

import "github.com/cilium/fake/flow"

ff := flow.NewFaker()

// A fully random flow
f := ff.NewFlow()

// A dropped flow on a specific node
f = ff.NewFlow(
    flow.WithFlowVerdict(flowpb.Verdict_DROPPED),
    flow.WithFlowDropReason(flowpb.DropReason_POLICY_DENIED),
    flow.WithFlowNodeName("worker-03"),
)

Deterministic output

Pass your own source to get reproducible sequences — useful for golden tests or benchmarks.

import randv2 "math/rand/v2"

seed := [32]byte{} // fixed seed
f := fake.NewWithSource(randv2.NewChaCha8(seed))
fmt.Println(f.IP()) // always the same

Performance

Each Faker instance is independent and lock-free. For parallel workloads, create one per goroutine:

for range runtime.GOMAXPROCS(0) {
    go func() {
        f := fake.New()
        for {
            process(f.IP())
        }
    }()
}

Package-level convenience functions (fake.IP(), fake.Name(), ...) use a global instance behind a mutex and are slower under contention.

CLI

A small CLI wraps the library for shell scripts and quick iteration.

$ fake ip --ipv4 --count 3
192.0.2.41
10.128.7.200
172.21.0.14

$ fake flow | jq .verdict
"FORWARDED"

Install with:

make install                    # → /usr/local/bin/fake
BINDIR=~/.local/bin make install

Modules

Module	Purpose
github.com/cilium/fake	Generic generators (IPs, MACs, ports, names, K8s resources)
github.com/cilium/fake/flow	Hubble flow protobuf generation
github.com/cilium/fake/cmd	CLI binary

Contributing

Contributions are welcome! The options pattern makes it straightforward to add new constraints to existing generators or to introduce new ones.