{"record":{"id":"d9e5ae55b44d37cd","repo":"probelabs/goreplay","slug":"inactive-handle-error-q-interface-q","errorCode":null,"errorMessage":"inactive handle error: %q, interface: %q","messagePattern":"inactive handle error: %q, interface: %q","errorType":"error_code","errorClass":null,"httpStatus":null,"severity":"error","filePath":"internal/capture/capture.go","lineNumber":407,"sourceCode":"\t\tif len(l.config.VLANVIDs) > 0 {\n\t\t\tfor _, vi := range l.config.VLANVIDs {\n\t\t\t\tfilter = fmt.Sprintf(\"vlan %d and \", vi) + filter\n\t\t\t}\n\t\t} else {\n\t\t\tfilter = \"vlan and \" + filter\n\t\t}\n\t}\n\n\treturn\n}\n\n// PcapHandle returns new pcap Handle from dev on success.\n// this function should be called after setting all necessary options for this listener\nfunc (l *Listener) PcapHandle(ifi pcap.Interface) (handle *pcap.Handle, err error) {\n\tvar inactive *pcap.InactiveHandle\n\tinactive, err = pcap.NewInactiveHandle(ifi.Name)\n\tif err != nil {\n\t\treturn nil, fmt.Errorf(\"inactive handle error: %q, interface: %q\", err, ifi.Name)\n\t}\n\tdefer inactive.CleanUp()\n\n\tif l.config.TimestampType != \"\" && l.config.TimestampType != \"go\" {\n\t\tvar ts pcap.TimestampSource\n\t\tts, err = pcap.TimestampSourceFromString(l.config.TimestampType)\n\t\tfmt.Println(\"Setting custom Timestamp Source. Supported values: `go`, \", inactive.SupportedTimestamps())\n\t\terr = inactive.SetTimestampSource(ts)\n\t\tif err != nil {\n\t\t\treturn nil, fmt.Errorf(\"%q: supported timestamps: %q, interface: %q\", err, inactive.SupportedTimestamps(), ifi.Name)\n\t\t}\n\t}\n\tif l.config.Promiscuous {\n\t\tif err = inactive.SetPromisc(l.config.Promiscuous); err != nil {\n\t\t\treturn nil, fmt.Errorf(\"promiscuous mode error: %q, interface: %q\", err, ifi.Name)\n\t\t}\n\t}\n\tif l.config.Monitor {","sourceCodeStart":389,"sourceCodeEnd":425,"githubUrl":"https://github.com/probelabs/goreplay/blob/251e45abd242886bb64ff2b2dc98789556b56330/internal/capture/capture.go#L389-L425","documentation":"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.","triggerScenarios":"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).","commonSituations":"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.","solutions":["Verify the interface exists at runtime (net.Interfaces()) and match the name exactly before calling PcapHandle","Re-resolve the interface name by index/MAC instead of caching it in config","Check that the name is in the format libpcap expects for the platform (e.g. \\Device\\NPF_{GUID} on Windows)","Check memory availability if names are known-good (rare pcap_create allocation failure)"],"exampleFix":"// before\niface := pcap.Interface{Name: cfg.Iface} // stale/typo name\nhandle, err := l.PcapHandle(iface)\n// after\nnames, _ := net.Interfaces()\nfor _, n := range names {\n    if n.Name == cfg.Iface { return l.PcapHandle(toPcapIface(n)) }\n}\nreturn fmt.Errorf(\"interface %q not found\", cfg.Iface)","handlingStrategy":"try-catch","validationCode":"ifaces, err := net.Interfaces()\nfound := false\nfor _, i := range ifaces { if i.Name == cfg.Iface { found = true } }\nif !found { return fmt.Errorf(\"interface %q does not exist\", cfg.Iface) }","typeGuard":null,"tryCatchPattern":"handle, err := l.PcapHandle(ifi)\nif err != nil && strings.Contains(err.Error(), \"inactive handle error\") {\n    return fmt.Errorf(\"cannot open %s: %w — check the interface name\", ifi.Name, err)\n}","preventionTips":["Resolve interface names at runtime via net.Interfaces() rather than hardcoding","Re-resolve names after network reconfiguration or container restart","On Windows use the \\Device\\NPF_{GUID} form libpcap expects"],"tags":["go","pcap","interface","libpcap"],"backgroundTag":"invalid-interface-name","analyzedSha":"251e45abd242886bb64ff2b2dc98789556b56330","analyzedAt":"2026-09-02T16:44:11.369Z","contentChangedAt":null,"schemaVersion":2},"datasetVersion":"2026-09-09T21:17:11.164Z"}