// +build linux package libpod import ( "bytes" "fmt" "io" "io/ioutil" "net" "os" "os/exec" "path/filepath" "strconv" "strings" "sync" "syscall" "time" "github.com/containernetworking/plugins/pkg/ns" "github.com/containers/common/libnetwork/types" "github.com/containers/podman/v4/pkg/errorhandling" "github.com/containers/podman/v4/pkg/rootless" "github.com/containers/podman/v4/pkg/rootlessport" "github.com/containers/podman/v4/pkg/servicereaper" "github.com/pkg/errors" "github.com/sirupsen/logrus" ) type slirpFeatures struct { HasDisableHostLoopback bool HasMTU bool HasEnableSandbox bool HasEnableSeccomp bool HasCIDR bool HasOutboundAddr bool HasIPv6 bool } type slirp4netnsCmdArg struct { Proto string `json:"proto,omitempty"` HostAddr string `json:"host_addr"` HostPort uint16 `json:"host_port"` GuestAddr string `json:"guest_addr"` GuestPort uint16 `json:"guest_port"` } type slirp4netnsCmd struct { Execute string `json:"execute"` Args slirp4netnsCmdArg `json:"arguments"` } type slirp4netnsNetworkOptions struct { cidr string disableHostLoopback bool enableIPv6 bool isSlirpHostForward bool noPivotRoot bool mtu int outboundAddr string outboundAddr6 string } const ipv6ConfDefaultAcceptDadSysctl = "/proc/sys/net/ipv6/conf/default/accept_dad" func checkSlirpFlags(path string) (*slirpFeatures, error) { cmd := exec.Command(path, "--help") out, err := cmd.CombinedOutput() if err != nil { return nil, errors.Wrapf(err, "slirp4netns %q", out) } return &slirpFeatures{ HasDisableHostLoopback: strings.Contains(string(out), "--disable-host-loopback"), HasMTU: strings.Contains(string(out), "--mtu"), HasEnableSandbox: strings.Contains(string(out), "--enable-sandbox"), HasEnableSeccomp: strings.Contains(string(out), "--enable-seccomp"), HasCIDR: strings.Contains(string(out), "--cidr"), HasOutboundAddr: strings.Contains(string(out), "--outbound-addr"), HasIPv6: strings.Contains(string(out), "--enable-ipv6"), }, nil } func parseSlirp4netnsNetworkOptions(r *Runtime, extraOptions []string) (*slirp4netnsNetworkOptions, error) { slirpOptions := append(r.config.Engine.NetworkCmdOptions, extraOptions...) slirp4netnsOpts := &slirp4netnsNetworkOptions{ // overwrite defaults disableHostLoopback: true, mtu: slirp4netnsMTU, noPivotRoot: r.config.Engine.NoPivotRoot, } for _, o := range slirpOptions { parts := strings.SplitN(o, "=", 2) if len(parts) < 2 { return nil, errors.Errorf("unknown option for slirp4netns: %q", o) } option, value := parts[0], parts[1] switch option { case "cidr": ipv4, _, err := net.ParseCIDR(value) if err != nil || ipv4.To4() == nil { return nil, errors.Errorf("invalid cidr %q", value) } slirp4netnsOpts.cidr = value case "port_handler": switch value { case "slirp4netns": slirp4netnsOpts.isSlirpHostForward = true case "rootlesskit": slirp4netnsOpts.isSlirpHostForward = false default: return nil, errors.Errorf("unknown port_handler for slirp4netns: %q", value) } case "allow_host_loopback": switch value { case "true": slirp4netnsOpts.disableHostLoopback = false case "false": slirp4netnsOpts.disableHostLoopback = true default: return nil, errors.Errorf("invalid value of allow_host_loopback for slirp4netns: %q", value) } case "enable_ipv6": switch value { case "true": slirp4netnsOpts.enableIPv6 = true case "false": slirp4netnsOpts.enableIPv6 = false default: return nil, errors.Errorf("invalid value of enable_ipv6 for slirp4netns: %q", value) } case "outbound_addr": ipv4 := net.ParseIP(value) if ipv4 == nil || ipv4.To4() == nil { _, err := net.InterfaceByName(value) if err != nil { return nil, errors.Errorf("invalid outbound_addr %q", value) } } slirp4netnsOpts.outboundAddr = value case "outbound_addr6": ipv6 := net.ParseIP(value) if ipv6 == nil || ipv6.To4() != nil { _, err := net.InterfaceByName(value) if err != nil { return nil, errors.Errorf("invalid outbound_addr6: %q", value) } } slirp4netnsOpts.outboundAddr6 = value case "mtu": var err error slirp4netnsOpts.mtu, err = strconv.Atoi(value) if slirp4netnsOpts.mtu < 68 || err != nil { return nil, errors.Errorf("invalid mtu %q", value) } default: return nil, errors.Errorf("unknown option for slirp4netns: %q", o) } } return slirp4netnsOpts, nil } func createBasicSlirp4netnsCmdArgs(options *slirp4netnsNetworkOptions, features *slirpFeatures) ([]string, error) { cmdArgs := []string{} if options.disableHostLoopback && features.HasDisableHostLoopback { cmdArgs = append(cmdArgs, "--disable-host-loopback") } if options.mtu > -1 && features.HasMTU { cmdArgs = append(cmdArgs, fmt.Sprintf("--mtu=%d", options.mtu)) } if !options.noPivotRoot && features.HasEnableSandbox { cmdArgs = append(cmdArgs, "--enable-sandbox") } if features.HasEnableSeccomp { cmdArgs = append(cmdArgs, "--enable-seccomp") } if options.cidr != "" { if !features.HasCIDR { return nil, errors.Errorf("cidr not supported") } cmdArgs = append(cmdArgs, fmt.Sprintf("--cidr=%s", options.cidr)) } if options.enableIPv6 { if !features.HasIPv6 { return nil, errors.Errorf("enable_ipv6 not supported") } cmdArgs = append(cmdArgs, "--enable-ipv6") } if options.outboundAddr != "" { if !features.HasOutboundAddr { return nil, errors.Errorf("outbound_addr not supported") } cmdArgs = append(cmdArgs, fmt.Sprintf("--outbound-addr=%s", options.outboundAddr)) } if options.outboundAddr6 != "" { if !features.HasOutboundAddr || !features.HasIPv6 { return nil, errors.Errorf("outbound_addr6 not supported") } if !options.enableIPv6 { return nil, errors.Errorf("enable_ipv6=true is required for outbound_addr6") } cmdArgs = append(cmdArgs, fmt.Sprintf("--outbound-addr6=%s", options.outboundAddr6)) } return cmdArgs, nil } // setupSlirp4netns can be called in rootful as well as in rootless func (r *Runtime) setupSlirp4netns(ctr *Container, netns ns.NetNS) error { path := r.config.Engine.NetworkCmdPath if path == "" { var err error path, err = exec.LookPath("slirp4netns") if err != nil { logrus.Errorf("Could not find slirp4netns, the network namespace won't be configured: %v", err) return nil } } syncR, syncW, err := os.Pipe() if err != nil { return errors.Wrapf(err, "failed to open pipe") } defer errorhandling.CloseQuiet(syncR) defer errorhandling.CloseQuiet(syncW) havePortMapping := len(ctr.config.PortMappings) > 0 logPath := filepath.Join(ctr.runtime.config.Engine.TmpDir, fmt.Sprintf("slirp4netns-%s.log", ctr.config.ID)) ctrNetworkSlipOpts := []string{} if ctr.config.NetworkOptions != nil { ctrNetworkSlipOpts = append(ctrNetworkSlipOpts, ctr.config.NetworkOptions["slirp4netns"]...) } netOptions, err := parseSlirp4netnsNetworkOptions(r, ctrNetworkSlipOpts) if err != nil { return err } slirpFeatures, err := checkSlirpFlags(path) if err != nil { return errors.Wrapf(err, "error checking slirp4netns binary %s: %q", path, err) } cmdArgs, err := createBasicSlirp4netnsCmdArgs(netOptions, slirpFeatures) if err != nil { return err } // the slirp4netns arguments being passed are describes as follows: // from the slirp4netns documentation: https://github.com/rootless-containers/slirp4netns // -c, --configure Brings up the tap interface // -e, --exit-fd=FD specify the FD for terminating slirp4netns // -r, --ready-fd=FD specify the FD to write to when the initialization steps are finished cmdArgs = append(cmdArgs, "-c", "-e", "3", "-r", "4") var apiSocket string if havePortMapping && netOptions.isSlirpHostForward { apiSocket = filepath.Join(ctr.runtime.config.Engine.TmpDir, fmt.Sprintf("%s.net", ctr.config.ID)) cmdArgs = append(cmdArgs, "--api-socket", apiSocket) } netnsPath := "" if !ctr.config.PostConfigureNetNS { ctr.rootlessSlirpSyncR, ctr.rootlessSlirpSyncW, err = os.Pipe() if err != nil { return errors.Wrapf(err, "failed to create rootless network sync pipe") } netnsPath = netns.Path() cmdArgs = append(cmdArgs, "--netns-type=path", netnsPath, "tap0") } else { defer errorhandling.CloseQuiet(ctr.rootlessSlirpSyncR) defer errorhandling.CloseQuiet(ctr.rootlessSlirpSyncW) netnsPath = fmt.Sprintf("/proc/%d/ns/net", ctr.state.PID) // we don't use --netns-path here (unavailable for slirp4netns < v0.4) cmdArgs = append(cmdArgs, fmt.Sprintf("%d", ctr.state.PID), "tap0") } cmd := exec.Command(path, cmdArgs...) logrus.Debugf("slirp4netns command: %s", strings.Join(cmd.Args, " ")) cmd.SysProcAttr = &syscall.SysProcAttr{ Setpgid: true, } // workaround for https://github.com/rootless-containers/slirp4netns/pull/153 if !netOptions.noPivotRoot && slirpFeatures.HasEnableSandbox { cmd.SysProcAttr.Cloneflags = syscall.CLONE_NEWNS cmd.SysProcAttr.Unshareflags = syscall.CLONE_NEWNS } // Leak one end of the pipe in slirp4netns, the other will be sent to conmon cmd.ExtraFiles = append(cmd.ExtraFiles, ctr.rootlessSlirpSyncR, syncW) logFile, err := os.Create(logPath) if err != nil { return errors.Wrapf(err, "failed to open slirp4netns log file %s", logPath) } defer logFile.Close() // Unlink immediately the file so we won't need to worry about cleaning it up later. // It is still accessible through the open fd logFile. if err := os.Remove(logPath); err != nil { return errors.Wrapf(err, "delete file %s", logPath) } cmd.Stdout = logFile cmd.Stderr = logFile var slirpReadyWg, netnsReadyWg *sync.WaitGroup if netOptions.enableIPv6 { // use two wait groups to make sure we set the sysctl before // starting slirp and reset it only after slirp is ready slirpReadyWg = &sync.WaitGroup{} netnsReadyWg = &sync.WaitGroup{} slirpReadyWg.Add(1) netnsReadyWg.Add(1) go func() { err := ns.WithNetNSPath(netnsPath, func(_ ns.NetNS) error { // Duplicate Address Detection slows the ipv6 setup down for 1-2 seconds. // Since slirp4netns is run it is own namespace and not directly routed // we can skip this to make the ipv6 address immediately available. // We change the default to make sure the slirp tap interface gets the // correct value assigned so DAD is disabled for it // Also make sure to change this value back to the original after slirp4netns // is ready in case users rely on this sysctl. orgValue, err := ioutil.ReadFile(ipv6ConfDefaultAcceptDadSysctl) if err != nil { netnsReadyWg.Done() // on ipv6 disabled systems the sysctl does not exists // so we should not error if errors.Is(err, os.ErrNotExist) { return nil } return err } err = ioutil.WriteFile(ipv6ConfDefaultAcceptDadSysctl, []byte("0"), 0644) netnsReadyWg.Done() if err != nil { return err } // wait until slirp4nets is ready before reseting this value slirpReadyWg.Wait() return ioutil.WriteFile(ipv6ConfDefaultAcceptDadSysctl, orgValue, 0644) }) if err != nil { logrus.Warnf("failed to set net.ipv6.conf.default.accept_dad sysctl: %v", err) } }() // wait until we set the sysctl netnsReadyWg.Wait() } if err := cmd.Start(); err != nil { if netOptions.enableIPv6 { slirpReadyWg.Done() } return errors.Wrapf(err, "failed to start slirp4netns process") } defer func() { servicereaper.AddPID(cmd.Process.Pid) if err := cmd.Process.Release(); err != nil { logrus.Errorf("Unable to release command process: %q", err) } }() err = waitForSync(syncR, cmd, logFile, 1*time.Second) if netOptions.enableIPv6 { slirpReadyWg.Done() } if err != nil { return err } // Set a default slirp subnet. Parsing a string with the net helper is easier than building the struct myself _, ctr.slirp4netnsSubnet, _ = net.ParseCIDR(defaultSlirp4netnsSubnet) // Set slirp4netnsSubnet addresses now that we are pretty sure the command executed if netOptions.cidr != "" { ipv4, ipv4network, err := net.ParseCIDR(netOptions.cidr) if err != nil || ipv4.To4() == nil { return errors.Errorf("invalid cidr %q", netOptions.cidr) } ctr.slirp4netnsSubnet = ipv4network } if havePortMapping { if netOptions.isSlirpHostForward { return r.setupRootlessPortMappingViaSlirp(ctr, cmd, apiSocket) } return r.setupRootlessPortMappingViaRLK(ctr, netnsPath, nil) } return nil } // Get expected slirp ipv4 address based on subnet. If subnet is null use default subnet // Reference: https://github.com/rootless-containers/slirp4netns/blob/master/slirp4netns.1.md#description func GetSlirp4netnsIP(subnet *net.IPNet) (*net.IP, error) { _, slirpSubnet, _ := net.ParseCIDR(defaultSlirp4netnsSubnet) if subnet != nil { slirpSubnet = subnet } expectedIP, err := addToIP(slirpSubnet, uint32(100)) if err != nil { return nil, errors.Wrapf(err, "error calculating expected ip for slirp4netns") } return expectedIP, nil } // Get expected slirp Gateway ipv4 address based on subnet // Reference: https://github.com/rootless-containers/slirp4netns/blob/master/slirp4netns.1.md#description func GetSlirp4netnsGateway(subnet *net.IPNet) (*net.IP, error) { _, slirpSubnet, _ := net.ParseCIDR(defaultSlirp4netnsSubnet) if subnet != nil { slirpSubnet = subnet } expectedGatewayIP, err := addToIP(slirpSubnet, uint32(2)) if err != nil { return nil, errors.Wrapf(err, "error calculating expected gateway ip for slirp4netns") } return expectedGatewayIP, nil } // Get expected slirp DNS ipv4 address based on subnet // Reference: https://github.com/rootless-containers/slirp4netns/blob/master/slirp4netns.1.md#description func GetSlirp4netnsDNS(subnet *net.IPNet) (*net.IP, error) { _, slirpSubnet, _ := net.ParseCIDR(defaultSlirp4netnsSubnet) if subnet != nil { slirpSubnet = subnet } expectedDNSIP, err := addToIP(slirpSubnet, uint32(3)) if err != nil { return nil, errors.Wrapf(err, "error calculating expected dns ip for slirp4netns") } return expectedDNSIP, nil } // Helper function to calculate slirp ip address offsets // Adapted from: https://github.com/signalsciences/ipv4/blob/master/int.go#L12-L24 func addToIP(subnet *net.IPNet, offset uint32) (*net.IP, error) { // I have no idea why I have to do this, but if I don't ip is 0 ipFixed := subnet.IP.To4() ipInteger := uint32(ipFixed[3]) | uint32(ipFixed[2])<<8 | uint32(ipFixed[1])<<16 | uint32(ipFixed[0])<<24 ipNewRaw := ipInteger + offset // Avoid overflows if ipNewRaw < ipInteger { return nil, errors.Errorf("integer overflow while calculating ip address offset, %s + %d", ipFixed, offset) } ipNew := net.IPv4(byte(ipNewRaw>>24), byte(ipNewRaw>>16&0xFF), byte(ipNewRaw>>8)&0xFF, byte(ipNewRaw&0xFF)) if !subnet.Contains(ipNew) { return nil, errors.Errorf("calculated ip address %s is not within given subnet %s", ipNew.String(), subnet.String()) } return &ipNew, nil } func waitForSync(syncR *os.File, cmd *exec.Cmd, logFile io.ReadSeeker, timeout time.Duration) error { prog := filepath.Base(cmd.Path) if len(cmd.Args) > 0 { prog = cmd.Args[0] } b := make([]byte, 16) for { if err := syncR.SetDeadline(time.Now().Add(timeout)); err != nil { return errors.Wrapf(err, "error setting %s pipe timeout", prog) } // FIXME: return err as soon as proc exits, without waiting for timeout if _, err := syncR.Read(b); err == nil { break } else { if os.IsTimeout(err) { // Check if the process is still running. var status syscall.WaitStatus pid, err := syscall.Wait4(cmd.Process.Pid, &status, syscall.WNOHANG, nil) if err != nil { return errors.Wrapf(err, "failed to read %s process status", prog) } if pid != cmd.Process.Pid { continue } if status.Exited() { // Seek at the beginning of the file and read all its content if _, err := logFile.Seek(0, 0); err != nil { logrus.Errorf("Could not seek log file: %q", err) } logContent, err := ioutil.ReadAll(logFile) if err != nil { return errors.Wrapf(err, "%s failed", prog) } return errors.Errorf("%s failed: %q", prog, logContent) } if status.Signaled() { return errors.Errorf("%s killed by signal", prog) } continue } return errors.Wrapf(err, "failed to read from %s sync pipe", prog) } } return nil } func (r *Runtime) setupRootlessPortMappingViaRLK(ctr *Container, netnsPath string, netStatus map[string]types.StatusBlock) error { syncR, syncW, err := os.Pipe() if err != nil { return errors.Wrapf(err, "failed to open pipe") } defer errorhandling.CloseQuiet(syncR) defer errorhandling.CloseQuiet(syncW) logPath := filepath.Join(ctr.runtime.config.Engine.TmpDir, fmt.Sprintf("rootlessport-%s.log", ctr.config.ID)) logFile, err := os.Create(logPath) if err != nil { return errors.Wrapf(err, "failed to open rootlessport log file %s", logPath) } defer logFile.Close() // Unlink immediately the file so we won't need to worry about cleaning it up later. // It is still accessible through the open fd logFile. if err := os.Remove(logPath); err != nil { return errors.Wrapf(err, "delete file %s", logPath) } if !ctr.config.PostConfigureNetNS { ctr.rootlessPortSyncR, ctr.rootlessPortSyncW, err = os.Pipe() if err != nil { return errors.Wrapf(err, "failed to create rootless port sync pipe") } } childIP := getRootlessPortChildIP(ctr, netStatus) cfg := rootlessport.Config{ Mappings: ctr.convertPortMappings(), NetNSPath: netnsPath, ExitFD: 3, ReadyFD: 4, TmpDir: ctr.runtime.config.Engine.TmpDir, ChildIP: childIP, ContainerID: ctr.config.ID, RootlessCNI: ctr.config.NetMode.IsBridge() && rootless.IsRootless(), } cfgJSON, err := json.Marshal(cfg) if err != nil { return err } cfgR := bytes.NewReader(cfgJSON) var stdout bytes.Buffer path, err := r.config.FindHelperBinary(rootlessport.BinaryName, false) if err != nil { return err } cmd := exec.Command(path) cmd.Args = []string{rootlessport.BinaryName} // Leak one end of the pipe in rootlessport process, the other will be sent to conmon defer errorhandling.CloseQuiet(ctr.rootlessPortSyncR) cmd.ExtraFiles = append(cmd.ExtraFiles, ctr.rootlessPortSyncR, syncW) cmd.Stdin = cfgR // stdout is for human-readable error, stderr is for debug log cmd.Stdout = &stdout cmd.Stderr = io.MultiWriter(logFile, &logrusDebugWriter{"rootlessport: "}) cmd.SysProcAttr = &syscall.SysProcAttr{ Setpgid: true, } if err := cmd.Start(); err != nil { return errors.Wrapf(err, "failed to start rootlessport process") } defer func() { servicereaper.AddPID(cmd.Process.Pid) if err := cmd.Process.Release(); err != nil { logrus.Errorf("Unable to release rootlessport process: %q", err) } }() if err := waitForSync(syncR, cmd, logFile, 3*time.Second); err != nil { stdoutStr := stdout.String() if stdoutStr != "" { // err contains full debug log and too verbose, so return stdoutStr logrus.Debug(err) return errors.Errorf("rootlessport " + strings.TrimSuffix(stdoutStr, "\n")) } return err } logrus.Debug("rootlessport is ready") return nil } func (r *Runtime) setupRootlessPortMappingViaSlirp(ctr *Container, cmd *exec.Cmd, apiSocket string) (err error) { const pidWaitTimeout = 60 * time.Second chWait := make(chan error) go func() { interval := 25 * time.Millisecond for i := time.Duration(0); i < pidWaitTimeout; i += interval { // Check if the process is still running. var status syscall.WaitStatus pid, err := syscall.Wait4(cmd.Process.Pid, &status, syscall.WNOHANG, nil) if err != nil { break } if pid != cmd.Process.Pid { continue } if status.Exited() || status.Signaled() { chWait <- fmt.Errorf("slirp4netns exited with status %d", status.ExitStatus()) } time.Sleep(interval) } }() defer close(chWait) // wait that API socket file appears before trying to use it. if _, err := WaitForFile(apiSocket, chWait, pidWaitTimeout); err != nil { return errors.Wrapf(err, "waiting for slirp4nets to create the api socket file %s", apiSocket) } // for each port we want to add we need to open a connection to the slirp4netns control socket // and send the add_hostfwd command. for _, i := range ctr.convertPortMappings() { conn, err := net.Dial("unix", apiSocket) if err != nil { return errors.Wrapf(err, "cannot open connection to %s", apiSocket) } defer func() { if err := conn.Close(); err != nil { logrus.Errorf("Unable to close connection: %q", err) } }() hostIP := i.HostIP if hostIP == "" { hostIP = "0.0.0.0" } apiCmd := slirp4netnsCmd{ Execute: "add_hostfwd", Args: slirp4netnsCmdArg{ Proto: i.Protocol, HostAddr: hostIP, HostPort: i.HostPort, GuestPort: i.ContainerPort, }, } // create the JSON payload and send it. Mark the end of request shutting down writes // to the socket, as requested by slirp4netns. data, err := json.Marshal(&apiCmd) if err != nil { return errors.Wrapf(err, "cannot marshal JSON for slirp4netns") } if _, err := conn.Write([]byte(fmt.Sprintf("%s\n", data))); err != nil { return errors.Wrapf(err, "cannot write to control socket %s", apiSocket) } if err := conn.(*net.UnixConn).CloseWrite(); err != nil { return errors.Wrapf(err, "cannot shutdown the socket %s", apiSocket) } buf := make([]byte, 2048) readLength, err := conn.Read(buf) if err != nil { return errors.Wrapf(err, "cannot read from control socket %s", apiSocket) } // if there is no 'error' key in the received JSON data, then the operation was // successful. var y map[string]interface{} if err := json.Unmarshal(buf[0:readLength], &y); err != nil { return errors.Wrapf(err, "error parsing error status from slirp4netns") } if e, found := y["error"]; found { return errors.Errorf("error from slirp4netns while setting up port redirection: %v", e) } } logrus.Debug("slirp4netns port-forwarding setup via add_hostfwd is ready") return nil } func getRootlessPortChildIP(c *Container, netStatus map[string]types.StatusBlock) string { if c.config.NetMode.IsSlirp4netns() { slirp4netnsIP, err := GetSlirp4netnsIP(c.slirp4netnsSubnet) if err != nil { return "" } return slirp4netnsIP.String() } var ipv6 net.IP for _, status := range netStatus { for _, netInt := range status.Interfaces { for _, netAddress := range netInt.Subnets { ipv4 := netAddress.IPNet.IP.To4() if ipv4 != nil { return ipv4.String() } ipv6 = netAddress.IPNet.IP } } } if ipv6 != nil { return ipv6.String() } return "" } // reloadRootlessRLKPortMapping will trigger a reload for the port mappings in the rootlessport process. // This should only be called by network connect/disconnect and only as rootless. func (c *Container) reloadRootlessRLKPortMapping() error { if len(c.config.PortMappings) == 0 { return nil } childIP := getRootlessPortChildIP(c, c.state.NetworkStatus) logrus.Debugf("reloading rootless ports for container %s, childIP is %s", c.config.ID, childIP) conn, err := openUnixSocket(filepath.Join(c.runtime.config.Engine.TmpDir, "rp", c.config.ID)) if err != nil { return errors.Wrap(err, "could not reload rootless port mappings, port forwarding may no longer work correctly") } defer conn.Close() enc := json.NewEncoder(conn) err = enc.Encode(childIP) if err != nil { return errors.Wrap(err, "port reloading failed") } b, err := ioutil.ReadAll(conn) if err != nil { return errors.Wrap(err, "port reloading failed") } data := string(b) if data != "OK" { return errors.Errorf("port reloading failed: %s", data) } return nil }