Function printNetCheckReport

cmd/tailscale/cli/netcheck.go:157–247

(dm *tailcfg.DERPMap, report *netcheck.Report)

}

func printNetCheckReport(dm *tailcfg.DERPMap, report *netcheck.Report) error {
	var j []byte
	var err error
	switch netcheckArgs.format {
	case "":
	case "json":
		j, err = json.MarshalIndent(report, "", "\t")
	case "json-line":
		j, err = json.Marshal(report)
	default:
		return fmt.Errorf("unknown output format %q", netcheckArgs.format)
	}
	if err != nil {
		return err
	}
	if j != nil {
		j = append(j, '\n')
		Stdout.Write(j)
		return nil
	}

	printf("\nReport:\n")
	printf("\t* Time: %v\n", report.Now.Local().Format(tstime.DateSpTimeNanoZ))
	printf("\t* UDP: %v\n", report.UDP)
	if report.GlobalV4.IsValid() {
		printf("\t* IPv4: yes, %s\n", report.GlobalV4)
	} else {
		printf("\t* IPv4: (no addr found)\n")
	}
	if report.GlobalV6.IsValid() {
		printf("\t* IPv6: yes, %s\n", report.GlobalV6)
	} else if report.IPv6 {
		printf("\t* IPv6: (no addr found)\n")
	} else if report.OSHasIPv6 {
		printf("\t* IPv6: no, but OS has support\n")
	} else {
		printf("\t* IPv6: no, unavailable in OS\n")
	}
	printf("\t* MappingVariesByDestIP: %v\n", report.MappingVariesByDestIP)
	printf("\t* PortMapping: %v\n", portMapping(report))
	if report.CaptivePortal != "" {
		printf("\t* CaptivePortal: %v\n", report.CaptivePortal)
	}

	// When DERP latency checking failed,
	// magicsock will try to pick the DERP server that
	// most of your other nodes are also using
	if len(report.RegionLatency) == 0 {
		printf("\t* Nearest DERP: unknown (no response to latency probes)\n")
	} else {
		if report.PreferredDERP != 0 {
			if region, ok := dm.Regions[report.PreferredDERP]; ok {
				printf("\t* Nearest DERP: %v\n", region.RegionName)
			} else {
				printf("\t* Nearest DERP: %v (region not found in map)\n", report.PreferredDERP)
			}
		} else {
			printf("\t* Nearest DERP: [none]\n")