probelabs/goreplay · error

inactive handle error

Error message

inactive handle error: %q, interface: %q

What it means

Listener.PcapHandle first creates a libpcap InactiveHandle for the interface name via pcap.NewInactiveHandle. If that creation fails (it allocates a pcap_t without activating it), the error is wrapped as "inactive handle error: <err>, interface: <name>". It almost always means the interface name is invalid or libpcap could not allocate the handle.

Solutions

1. Verify the interface exists at runtime (net.Interfaces()) and match the name exactly before calling PcapHandle
2. Re-resolve the interface name by index/MAC instead of caching it in config
3. Check that the name is in the format libpcap expects for the platform (e.g. \Device\NPF_{GUID} on Windows)
4. Check memory availability if names are known-good (rare pcap_create allocation failure)

Example fix

// before
iface := pcap.Interface{Name: cfg.Iface} // stale/typo name
handle, err := l.PcapHandle(iface)
// after
names, _ := net.Interfaces()
for _, n := range names {
    if n.Name == cfg.Iface { return l.PcapHandle(toPcapIface(n)) }
}
return fmt.Errorf("interface %q not found", cfg.Iface)

ifaces, err := net.Interfaces()
found := false
for _, i := range ifaces { if i.Name == cfg.Iface { found = true } }
if !found { return fmt.Errorf("interface %q does not exist", cfg.Iface) }

handle, err := l.PcapHandle(ifi)
if err != nil && strings.Contains(err.Error(), "inactive handle error") {
    return fmt.Errorf("cannot open %s: %w — check the interface name", ifi.Name, err)
}

When it happens

Trigger: Calling PcapHandle/activatePcap with an ifi.Name that does not exist or is empty, or when libpcap fails to allocate memory for the inactive handle (pcap_create failure).

Common situations: Interface name typo or wrong interface name from config; interface renamed/removed (e.g. after netlink rename or container restart); on Windows using a name that is not the \Device\NPF_ GUID form; out-of-memory in the capture process.

Related errors

• handle buffer timeout error
• promiscuous mode error
• : supported timestamps: , interface
• snapshot length error
• handle buffer size error

AI-assisted analysis of probelabs/goreplay@251e45abd2 (2026-09-02). Data as JSON: /api/errors/d9e5ae55b44d37cd. Report an issue: GitHub.

Appendix: source

Thrown at internal/capture/capture.go:407

		if len(l.config.VLANVIDs) > 0 {
			for _, vi := range l.config.VLANVIDs {
				filter = fmt.Sprintf("vlan %d and ", vi) + filter
			}
		} else {
			filter = "vlan and " + filter
		}
	}

	return
}

// PcapHandle returns new pcap Handle from dev on success.
// this function should be called after setting all necessary options for this listener
func (l *Listener) PcapHandle(ifi pcap.Interface) (handle *pcap.Handle, err error) {
	var inactive *pcap.InactiveHandle
	inactive, err = pcap.NewInactiveHandle(ifi.Name)
	if err != nil {
		return nil, fmt.Errorf("inactive handle error: %q, interface: %q", err, ifi.Name)
	}
	defer inactive.CleanUp()

	if l.config.TimestampType != "" && l.config.TimestampType != "go" {
		var ts pcap.TimestampSource
		ts, err = pcap.TimestampSourceFromString(l.config.TimestampType)
		fmt.Println("Setting custom Timestamp Source. Supported values: `go`, ", inactive.SupportedTimestamps())
		err = inactive.SetTimestampSource(ts)
		if err != nil {
			return nil, fmt.Errorf("%q: supported timestamps: %q, interface: %q", err, inactive.SupportedTimestamps(), ifi.Name)
		}
	}
	if l.config.Promiscuous {
		if err = inactive.SetPromisc(l.config.Promiscuous); err != nil {
			return nil, fmt.Errorf("promiscuous mode error: %q, interface: %q", err, ifi.Name)
		}
	}
	if l.config.Monitor {

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