probelabs/goreplay · error

inactive handle error: %q, interface: %q

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.

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 {

View on GitHub (pinned to 251e45abd2)

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

• %q: supported timestamps: %q, interface: %q
• promiscuous mode error: %q, interface: %q
• snapshot length error: %q, interface: %q
• handle buffer timeout error: %q, interface: %q
• monitor mode error: %q, interface: %q

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